A STUDY OF THE ECOLOGICAL RELATIONSHIPS AND
TAXONOMIC STATUS OF TWO SPECIES OF THE
GENUS CALANUS (CRUSTACEA: COPEPODA)
by
CHARLES D. WOODHOUSE, JR.
B.A., University of California in Santa Barbara, 1962 M.A., University of Oregon, 1964
A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY
in the Department of ZOOLOGY
accept this thesis as conforming to the required standard
THE UNIVERSITY OF BRITISH COLUMBIA
April, 1971 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study.
I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission.
Department
The University of British Columbia Vancouver 8, Canada
Date /^"^tP/y/. This thesis presents the results of an investigation on the relationships between populations of closely related animals un• der apparent sympatric conditions. The mechanisms found have particular application toward understanding the species problem among members of the free-swimming marine copepod genus Calanus that possess a toothed inner surface on the coxopodites of the fifth pair of swirnming legs.
The investigation describes the morphology, distribution, and general ecology of two forms of toothed Calanus from the far eastern North Pacific Ocean. Morphological differences were es• tablished and used to distinguish both forms on the oasis of length, shape of the anterior surface of the cephalothorax, proportionate differences in segments of the urosome and fifth swimming legs, and by the degree of asymmetry in the fifth pair of swimming legs of males. An additional feature was the length of a small spine on the fifth swimming legs of both forms.
A general account of the distribution and ecology of both forms from Glacier Bay, Alaska, to the Mexican Border was de• rived from data gathered during several long cruises. The Large
Form was found from Glacier Bay, Alaska, to Cape Mendocino,
California. The Small Form was found from the Mexican Border to the vicinity of Vancouver Island, British Columbia. Along the outer coast, the Large Form appeared to be associated with
Pacific Sub-Arctic water typical of the California Current, whereas the Small Form appeared to be associated with the warmer more saline water typical of Equatorial Pacific water associ• ated with the Davidson Counter Current. A detailed analysis of the ecological relationships of both forms in a region of overlap was performed in Indian Arm, an inlet near Vancouver, British Columbia. In this inlet, the Large Form was generally associated with the cooler more saline deep water.of the inlet. The Small Form occurred at shallower depths. Overlap between the populations of both forms was lim• ited to Large Form females that rose to shallower depths during part of the year occupying nearly the same portion of the water column as the Small Form population. The yearly cycles of both forms in Indian Arm were shown to be different indicating dif• ferent times of breeding for Large and Small Forms. On the basis of morphology and previous descriptions for toothed members of the genus Calanus, the Large Form appeared to he Calanus glacialis and the Small Form C. pacificus californi- cus. Based on the results of the distributional study and the ecological study, it was concluded that both forms were behaving as good species since separation of breeding populations both spatially and temporally appeared to be real, and the likelihood of interbreeding appeared to be small. In the classical sense, the two species are sympatric be• cause their ranges overlap, and there is a strong indication that interbreeding occurs infrequently if at all. Association to dif• ferent types of water and differences in yearly cycles appear to be the primary mechanisms that act to maintain the integrity of sympatric species. The vertical as well as horizontal space must be given equal consideration in planktonic studies. Under these conditions, therefore, the toothed Calanus spp. of Indian Arm are allopatric with respect to the water column. Page
ABSTRACT • i
LIST OF TABLES v
• LIST OF FIGURES vii
ACKNOWLEDGEMENTS • ix
INTRODUCTION 1
MATERIALS AND METHODS . 12 General sampling procedure 12 Morphology 14 Distributional Survey 21 Ecological Study . . 23
RESULTS 34 Morphology 34 Prosome 34 Headshape 39 Urosome 42 Swimming Legs 49 Distribution 6l Ecology 69 Yearly Presence and Density 69 Yearly Cycles and Periods of Breeding 69 Analysis of Moulting Rates 83 Physical Environment 85 Mid-Day Vertical Distributions 93 24 Hour Vertical Distributions 97 Available Food IO5 Breeding Experiments.- 107
DISCUSSION • 109 Summary of the Differences 1.09 Comparison to. Other Species 110 Distribution 118 Distributional Ecology 120 Ecological Studies in Indian Arm 127
BIBLIOGRAPHY" .141
APPENDIX I - Procedure with Stratified Plankton Net Tows 146
APPENDIX II - The External Morphology of•Toothed Calanus spp. from the Waters of Southern British Columbia 154 I Station list 2\\
-II .Analysis of prosome lengths 37 III Mean Prosome lengths for Large Form along range sampled $8 IV Mean prosome lengths for Small Form along range sampled iiO
V Prosome analysis ill
VI Results of T test on headshapes i\.7
VII Analysis of width/length ratios of the urosome segments IL7 VIII Analysis of asymmetry in fifth legs of males, -statistical results of the ratio: length right exopod/length left exopod- 52 IX A Analysis of the proportionate lengths of exopod segments in the fifth legs of males 52 IX B T test on the proportionate lengths of the exopod segments of the left fifth swimming legs of males 53 >X Width:length values of first, and/or second segments, left exopod, fifth swimming leg, males 53 XI A Analysis of proportionate lengths of exopod segments in fifth legs of females 59 .AXIBB T test on proportionate lengths of exopod segment 3 on the fifth swimming legs of females 59 XII T test on mean lengths of the spinose process on the fifth legs of males and females 60 TABLE NO:SUBJECT PAGE XIII Proportions of adults to stage-V copepodites for Indian Arm 76 XIV Proportion of adults:stage-V copepodites Alaskan Cruise of Aug. 1965 77 XV Proportion of adults: stage-V copepodites. Cruises to inlets of British Columbia July 1966 and June 1967 78 XVI Proportion of adults:stage-V copepodites. Eastern Pacific cruise of Feb. 66 8l XVII Composition of Breeding Experiments 108 NO. SUBJECT . PAGE
1. A. Diagram of typical female Calanus in lateral view
B. Diagram of typical fifth swimming leg of male Calanus 11
2. Diagram of the process of headshape measure• ment showing orientation of the cephalothorax 18
3. Map of west coast U.S.A. with station positions 22
li. Map of Indian Arm, British Columbia 28
5. Sub-sampler 31
6. Prosome lengths 35
7. Prosome lengths: Large Form vs latitude 3©
8. Photograph of females I4.3
9. Photograph of stage-V copepodites ijij.
10. Photograph of males ij.5
11. Head shape distributions lj.6
12. Urosome ratios, distribution ii8
13. Photographs of male fifth swimming legs 50
Ratio length right exopod/length left exopod; fifth swimming legs of males %\\.
15. Females: third exopod seg./prosome segments
16. Females: spinose process, length vs
frequency 57
17. Males: spinose process, length vs frequency 58
18. Map showing distribution of both Large and Small Forms 62 19. T, S diagram of west coast data 63 NO. SUBJECT . . PAGE 20. T, S, P diagram of west coast data 64 21. Total animals/m-Vro°nth (both Forms? Indian Arm only) . . 70
22. Yearly cycles: both adults and Stage-V's 71 23. Percentage of adults of each Form over sampling period 72 24. Moulting rate vs temperature - . 84 25. T & S profiles for Indian Arm, Feb., Mar. 1967 87 26. T & S profiles for Indian Arm, Apr., May, June, 1967 88 27. T & S profiles for Indian Arm, Jul., Aug., Sep. , 1967 89 28. T & S profiles for Indian Arm, Oct., Nov., Dec. , 1967 90 29. T & S profiles for Indian Arm, Jan., Feb., Mar. , 1968 91 30. Mid-day distribution, Indian Ajem 96
31. 24 hour vert, distributions Feb. 6? & May 67 101
32. 24 hour vert, distributions Jul. 6? & Aug. 6 102 ? 33. 24 hour vert, distributions Sep. 6? & Jan. 68 103 34. 24 hour vert, distributions Feb. 68 & Mar. 68 104 35. Chlorophyll distribution for Feb. & Mar. 1968 106 I am grateful to the officers and men of the CNAV ENDEAVOUR,
R/Vs VECTOR and EHKOLT. Their help and experience in planning
and conducting the cruises for the field work in this study was
indispensible, and indeed, without the use of these ships a study
of this type could not be accomplished. I would like to express a special note of thanks to Mr. Murray Storm and to Mr. Heinz
Heckel of the Institute of Oceanography, University of British
Columbia. Mr. Storm provided invaluable assistance in the collec•
tion and analysis of hydrographic data and Mr. Heckel provided a necessary capability in the construction, maintenance and repair
of the sampling gear used during the investigation. During the
sorting and identification phases of the plankton sample analyses,
Miss Diane Debruyn devoted many hours to this tedious work, and I
shall forever be appreciative of her willingness to continue and
of her interest in the research as it progressed.
I express my sincere appreciation to Dr. Alan G. Lewis and
to Dr. Brian Bary. Dr. Bary suggested the problem since it ap• peared as though it would be a worthwhile adjunct to a larger
research problem of his own. Dr. Lewis has acted as an immediate
supervisor, and to him I am grateful of his guidance and continued
criticism of the research and final manuscript. Both Dr. Lewis and Dr. Bary have shown a unique willingness to take time out
from their own work and provide assistance as problems arose dur•
ing the course of this investigation. Finally, I express my gratitude to the remaining staff of the Institute of Oceanography who in one way or another provided their assistance and guidance during the study. A special word of appreciation must go to the Government of Canada for its financial support during the summer months and to the University of British Columbia, Zoology Department for the invaluable teaching assistantships during the winter sessions at the Uni• versity. A knowledge of the ecological relationships between two sympatric species would help in understanding the species prob• lem by elucidating at least some of the mechanisms that act to block the gene flow between two such species populations in the absence of distinct geographical boundaries. Within the calanoid copepod genus Calanus there is a group of closely related species distinguished by a toothed coxopodite on the fifth swimming leg (Brodsky. 1950, 1959. 1965; Jaschnov, 1955. 1957, 1958; Marshall & Orr, 1955). This is a relatively diverse group yet a number of the recognized species overlap geographically, occurring under what appear to be sympatric conditions. Although the various members of this genus are one of the most studied groups of the zooplahkton, mechanisms of speciation within the group and in• terrelationships of the overlapping species have not been satis• factorily resolved. Shan (1962) demonstrated that two "forms" of toothed Calanus sp. occur in southern British Columbia. Bary (personal communi• cation) has suggested that British Columbia might be a region of overlap between these two "forms" with the result that further north or further south one or the other would be absent. Thus, existence of a sympatric condition in the waters of southern British Columbia was implied, but because the taxonomy of the local "forms" was uncertain previously, the experimental approach of this study had to be one that would resolve this taxonomic problem as well as contribute to the understanding of sympatric species relationships. The degree of morphological distinction in the local animals is similar to other well recognized species pairs, e.g., Calanus finmarchicus and C; helgolandicus (Marshall, personal communi• cation). Under these premises a dichotomy exists whereby re• sults of a more detailed study would show either that the two "forms" are one species but may possibly be diverging sympa- trically or that the two "forms" are two distinct but sympatric species. If the former case were true, further study might indicate th£ processes of sympatric speciation within the zoo- plankton. A study where the latter case were true would result in a better understanding of how two planktonic species maintain their integrity under sympatric conditions. With these possibili• ties in mind, the present study was designed so that the.field sampling and experimental results would allow amplification of either possibility. The early reports of toothed Calanus from the west coast of North America relied upon the descriptions of C. finmarchicus from the North Atlantic for identification. There is some simi• lar i|y between the animals from both regions, and as a result the Pacific coast forms were considered morphological variants of C. finmarchicus. Esterly (1905) described the Calanus from the region of San Diego and later (1924) from San Francisco Bay as C. finmarchicus. In his discussion he mentions the differences between C, finmar• chicus and C. helgolandicus but states his agreement with With (1915) that these differences are not significant and that both are C. fInmarchicus. The earliest indication that a species of toothed Calanus may be present in the waters of British Columbia is in a report by McMurrich (19-6). He studied the plankton along the British Columbia coast and mentions encountering large numbers of a copepod "metanauplius" that resembled that of C. finmarchicus. Confirmation of the presence of the species was not possible due to the absence of adults in his samples. . The earliest and most extensive published account on the zoo- plankton from the waters of British Columbia was completed by Campbell (1929). In this publication the toothed Calanus is diagnosed as C. finmarchicus. although a difference between the local males is noted. Following Sars (1903) Campbell notes that some of the males are similar to C. finmarchicus and others to
C. helgolandicuB. No differences are noted for females and in the discussion the author states, "the difference between the two forms are so slight that they may both be considered as varieties oi* C. f inmarchicus." The following year (Campbell, 1930) a second paper was published in which the controversy between C. finmar• chicus and C. helgolandicus is discussed. The author still main• tains the differences in the males but suggests that the two varieties may represent C. finmarchicus and C. helgolandicus thus reversing the earlier conclusion (Campbell, 1930). It is in these two papers, however, that the first indication of the ex• istence of two morphologically different forms of Calanus along the west coast appears. Davis (194-9) briefly discusses the problem of correctly diag• nosing the toothed Calanus of the northeast Pacific. The indica- tion presented is that there is one species, although it may be either C, finmarchicus or C. helgolandicus. The fact is mentioned that some consider C. helgolandicus to be a variety of C. finmarch• icus . but any definite statement on the status of Calanus from the northeast Pacific is not presented because insufficient specimens were available to permit a detailed diagnosis (Davis, 1949).
Brodsky (1948, 1950) mentioned that specimens collected 1 from the northwestern Pacific were similar to those described by
Esterly (1924) from San Francisco Bay. In conclusion he points out that Esterly's C. finmarchicus is actually a new species,
C. pacificus, and on the basis of mrophological differences, par• ticularly in the fifth swimming legs, separates C. pacificus.
C. helgolandicus. and C. finmarchicus. This is the first indica- tiontion from the literature that the west coast toothed Calanus are taxonomically different from the Atlantic forms.
Despite the comments of Brodsky (1950)» two papers were published in 1957 which dealt in part with the toothed Calanus of the waters of British Columbia. In the vicinity of the Queen
Charlotte Islands specimens of toothed Calanus were identified as' C. finmarchicus and a variation in size was noted with the conclusion that these different size groups belonged to different broods (Cameron, 1957)* In Georgia Strait a study was carried out on the distribution of zooplankton (Legare, 1957). but there
Is no mention of the occurrence of two forms of toothed Calanus. those present being identified as C. finmarchicus.
The copepods of Indian Arm, British Columbia, were studied by Shan (1962). With regard to the toothed Calanus, he noted two size groups but found they were difficult to distinguish. He was the first to mention a difference in the shape of the anterior region of the cephalothorax and noticed, as did Campbell (1929), the differences in the fifth legs of the males. In his work,
Shan refers to the Large and Small Form of Calanus sp. but in discussion of these two forms calls attention to the similarity of the Large Form to C. glacialis (Jaschnov, 1955) and of the Small Form to C. pacificus (Brodsky, 1950)• According to Shan (1962), however, the local Large Form is much smaller than C. glacialis as originally described, and the local Small Form dif• fers slightly from C. pacificus (Brodsky) in the structure of the fifth swimming legs. The toothed Calanus of Indian Arm is further distinguished from C. finmarchicus by the shape of the row of teeth on the fifth swimming legs and from C. helgolandicus by the shape of the anterior portion of the cephalothorax (Brod• sky, 1950). This work is the first to suggest the possibility that C. glacialis may be represented in the zooplankton of the coast of British Columbia, and it substantiates the speculation by Campbell (1929) that two forms in fact occur. In his final remarks, Shan suggests that a study in greater detail is needed to clarify the systematic position of the two forms. Since the appearance of Brodsky's work on the Calanoida (Brodsky, 1950), the species Calanus pacificus appears to be ac• cepted by a greater number of investigators. LeBrasseur (1964) published a checklist of zooplankton species for the waters of British Columbia and in this account he refers to the C. finmar• chicus type as C. pacificus. Fleminger (1964) described the toothed Calanus from California coastal waters as C. helgolandi• cus but does indicate the possibility that this animal may actu• ally be C. pacificus* Both of these publications cover a large amount of material so that a detailed study of the systematic position of any one species was not attempted and the acceptance of Brodsky's C. pacificus appears to be a matter of convenience. Groups of specimens of Calanus pacificus collected in vari• ous parts of the Pacific are diverse enough morphologically that they can be distinguished. Thus Brodsky (1965) sub-divided the group into a number of sub-species and erected C. p. California- us for the sub-species from California waters. Brodsky shows it to be distributed from Cape Flattery, Washington, to Baja Cal• ifornia. In addition to the speculation by Shan (1962) on the occur• rence of C. glacialis in British Columbia, Brodsky (1965) sug- . gests that the species may occur as far south as Cape Flattery, Washington, but a lack of material prevents the formulation of an accurate distribution for this species. Subsequent papers dealing with the toothed Calanus in British Columbia fail to mention C. glacialis or even that two forms appear in the zoo- plankton with the result that C. pacificus (helgolandicus) is the only species recognized (Fulton, 196b} Mullin, 196b). Since there is little doubt of the existence of two morpho• logically distinct groups of toothed Calanus in British Columbia (Shan, 1962; Bary, personal, communication), it is evident from the literature that their taxonomic position is in need of clari• fication. The Intent is to substantially demonstrate the taxon- omic position on both morphological and ecological grounds. The ecological relationships of two forms in an area of overlap pro• vide a valuable set of criteria in determining whether two such forms are behaving as true species populations in the sense of Mayr (1942). In the case of the toothed Calanus there has been very little done in terms of viewing the taxonomic status of the morphological variants through their ecology. This study deals only with the adult males and females and the juvenile Stage-V copepodites of the forms mentioned by Shan (1962). Other stages, i.e., first through sixth naupliar and first through fourth copepodite exhibit no distinguishing mor• phological characters on which they may be separated. For the reader who may be unfamiliar with the biology of toothed Calanus spp., a brief account of the broader aspects is included here. Comprehensive accounts may be found in a number of books devoted to the subject (Caiman, 1909J Marshall and Orr, 1955; and Waterman, i960). The animals are dioecious, holoplanktonic, neritic members of the zooplankton occurring in the upper 500 meters of the water column. They are generally found in the temperate, sub• polar and polar waters. A few have been reported from tropical or sub-tropical regions (Wilson, 1942 & 1950; Marshall and Orr, 1955)* Fertilization occurs by means of sperm from spermatophore produced by the male and attached to the female. Sperm cells are non-motile and are generally stored in the paired spermathecal sacs of the female genital segment or first urosomal segment (Fig. 7). Eggs are shed by the female and are fertilized internal to the genital pore where the left and right canals of the
spermathecal sacs join the distal end of the oviduct (Heb-erer,
1932). Once released the fertilized eggs develop apart from
the female, and normally hatching occurs after twenty-four hours
in at least one species (Marshall and Orr, 1955)• Subsequent to
hatching the young moult through six successive naupliar stages,
between the sixth nauplius and first copepodite stage, a marked
change in morphology is evident, and the juvenile assumes an appearance like that of the adult. As the animals moult from
copepodite Stage-I to Stage-V, the young become larger and addi•
tional segments are successively apparent. The final moult re•
sults in the adult, and secondary sexual characteristics become
evident. Some refer to the adult as Stage VI (Marshall and Orr,
1955).
The Stage-V copepodite has been referred to as the overwin•
tering stage. (Raymont, 1963s Marshall and Orr, 1955)' This par•
ticular stage is unique because it can withstand environmental
extremes that normally affect the survival of the other stages.
It is interesting to note that development to the fifth copepodite
stage takes approximately one month for Calanus finmarchicus (Mar•
shall and Orr, 1955), and a similar time span is indicated from
the results of this study for the eastern Pacific species. How• ever, the length of time spent in the Stage-V alone can be a mat•
ter of months. In one instance during this investigation, a 4- liter beaker containing 10 to 15 Stage-V copepodites was left in
the dark on a shelf in a cold-room (5«5°C) without food or water
change for b months. At the end of this time they were moving freely and responded to agitation of the water. The following frequently used terms are defined in order to clarify their use in the text and to avoid confusion with slight• ly different meanings attached to them by other authors.
Cephalothoraxi the anteriormost portion of the prosome of calanoid copepods consisting of the head and first thoracic somite (Marshall and Orr, 1955) (Fig. 1).
1 Neritic waters: those waters which are considered as "coastal" and which cover the continental shelf. They are often rich in nutrients and are generally regions of high biological productivity.
Oceanic waters: those waters that are seaward of neritic waters and in which the depth to the bottom is greater than 100 fathoms.
Prosome: the larger portion of the body of calanoid copepods consisting of the cephalothorax, which forms the anterior part, and five or six free thoracic somites forming the posterior part (Fig. 1). The term is synonomous with metasome as used by Marshall and Orr (1955).
Species: a group of organisms which interbreed and maintain populations that are reproductively isolated, under natural con• ditions, from populations of other similar and closely related organisms (Mayr, 19^2). Standard hydrographic depths, as used in this study they are, 0, 5, 10, 20, 30, 50, 75. 100, 125, 150, 175. and 200 meters. In the few cases where bottle casts were deeper than 200 meters, bottles were spaced 100 meters apart.
Toothed Calanus; That group of species within the genus Calanus bearing a dentate inner border on the coxopodite of the fifth swimming legs (Fig. 1).
Urosome: The smaller portion of the body of calanoid copepods, consisting of the last one or two thoracic somites and the abdomen, with a maximum of four segments including the telsoni and with a pair of caudal rami )Caiman, 1909. Marshall and Orr, 1955) (Fig. 1).
Water body: a group of related points on a temperature- salinity diagram which indicate a body of water distinctrfrom water surrounding it either in the veritcal or horizontal direc tion (Bary, 1963). Figure 1. A diagram of female Calanus in lateral view; Pr., prosome} Ur.i urosome; Cephthx., cephalothoraxj R.F. , rostral filament; G.S., genital segment; C.F., caudal furca. B, diagram of fifth swimming leg of male Calanusi Ex., exopodite; End., endopoditej Sp.P, , spinose process; Bs., basipodite; Cx., coxopodite; Th,, teeth. The scope of the study has made it necessary to apply a num• ber of different techniques. For this reason the materials and methods are classified according to the section of the study in which they were employed, with the exception of the opening sec• tion on sampling techniques. Intrinsic problems encountered in some of the procedures are also discussed.
General Sampling Procedure
A routine procedure was followed on the cruises. Tempera• ture and salinity measurements were taken over the portion of1 the water column to be sampled biologically. On early cruises oxygen measurements were taken, but there appeared to be no cor• relation between the oxygen concentrations encountered and the vertical distribution of Calanus and oxygen measurements were discontinued. Standard hydrographic depths were used, and the horizontal plankton sampling was planned so that the nets would sample about these same depths.
• ' Atlas bottles and closed reversing thermometers were used for hydrographic sampling. A bathythermograph was employed to check against readings obtained from the reversing thermometers, and to aid in interpolation of hydrographic conditions betweem sampling depths. Salinity samples were drawn from the Atlas bottles and run at a later time on an inductively coupled salin- ometer manufactured by Auto-lab Industries Pty. Ltd., Sydney,
Australia. Meterological observations were made at each station. When 24 hour stations were run at station number 9 in Indian Arm, only one hydrographic station was made during the period. A 70 centimeter ring net with a mesh aperture of 270 microns square was used for vertical sampling. This mesh was chosen for its relative effectiveness in retaining plankton of the size of Calanus. The net is cylindrical for 2/3 of its length. The distal 1/3 is a cone which xtapers to a diameter of 15 centimeters at the cod end. The design is considered particularly efficient for vertical sampling (E. Gllfillan, personal communication). Prior to the design and construction of this 70 centimeter ring net, available equipment included a Discovery net with a mesh aperture of 300 microns square, and a 1 meter ring net of mesh aperture ?00 microns square. These two nets were used in some of the early preliminary vertical sampling in collecting speci• mens for morphological study.
1 Clarke-Bumpus nets with a diameter of 13 centimeters and mesh aperture of 366 microns square (#2 nets) were used for strat• ified tows. A bathykymograph, time-depth recorder, was used in conjunction with-these nets to monitor a particular tow. The? specific procedure used for determining the depth of the Clarke- Bumpus nets is described in Appendix II. Life specimens were collected with the 70 centimeter net and thermos jugs were used to transport living material to the lab• oratory. Water for maintaining these specimens was-; collected with a 16 liter Van Dorn water bottle, filtered with a 0.45 micron Millipore, and stored in 20 liter Nalgene carboys at 5»5°C in the laboratory cold room. Animals were collected from Indian Arm station 9 (Fig. (ty) and
Georgia Strait Station I (^9°17'06" N, 12 3°50,00" W). The speci• mens were preserved with. 5% formalin buffered with sodium borate until they could be sorted and placed in 1 dram vials.
Specimens" were stained and cleared in one step in Clorazol
Black E dissolved in a $0% lactic acid solution. After reten• tion in this preparation for a minimum of 24 hours animals were transferred to a 50% glycerin solution for short term storage until they could be dissected and mounted on microslides.
Appendages were dissected using Minuten-Naden and mounted in CMC-S diluted about 2:1 with CMC-10. These two water sol• uble media are manufactured by TURTOX and are convenient for mounts of this nature. Oral appendages were mounted on 22 by
40 mm cover slips which were mounted in turn on cardboard slides so specimens could be studied from either side under high power objectives.
Peraepods were mounted on regular glass microslides. After dissection of the appendages, whole mounts of the remaining pro- some and urosome were made by gluing 1 cm, diameter plastic rings to a glass slide, and then melting glycerin jelly in the result• ing cavity. Using this technique, the whole mounts can be removed at a later date by heating the slide gently, removing the cover slip and placing the specimen in glycerin. Glycerin jelly was chosen as a mounting medium for whole mounts because it does not shrink as is the case for CMC-S and CMC-10. The two latter media will dry out with thick mounts and thus damage the specimen. All measurements were made with a pre-calibrated, optical . • micrometer mounted in a Zeiss compound microscope. Measurements of the prosome and urosome were made before dissection of the ap• pendages by placing each specimen in a hanging drop of glycerin. This technique avoids the problem of squashing or distortion by a cover glass and by dissection. Every animal was assigned a serial number so that subsequent measurements of the mounted ap• pendages could be maintained with the prosome and urosome measure• ments of the same specimen. i Among the morphological differences found in species and sub-species of Calanus. head shape is a consistent feature used to separate one type from the other• In their comparisons of the species many workers usually bring this feature into their descriptions (Brodsky, 1950; Marshall and Orr, 1955; Sars, 1903;
Jaschnov, 1955)» but rarely has it been described quantitatively. Often the slight differences in headshape are difficult to show on a drawing (Bary, personal communication).. For this reason an attempt was made to arrive at a means of measuring this feature in the llocal> animals so that the numerical quantities could be subjected'to statistical analysis and the significance of the headshape differences demonstrated. Several methods of headshape measurement were tried includ• ing one used previously on Calanus finmarchicus and C. helgoland• icus (Barnes and Barnes, 1953). All methods involved the,analysis of the curve of the cephalothorax. The reference points used, so that tracings were uniform, were the articulation surfaces of the cephalothorax including those at the bases of the oral appendages. A vector analysis, measurement of head angle, and a curvilinear regression were tried in addition to the method described by Barnes and Barnes (1953)* The vector analysis failed to show any difference in headshape although It was obvious from the ap• pearance of specimens used that a difference in curvature of the anterior cephalothorax did exist. The method of measuring head angle was unsuccessful in distinguishing the headshapes of the males, but the curvilinear regression was successful in demon• strating a difference between the adults of both sexes and juven• ile &tage-V copepodites when headshape differences were apparent from direct observation. The method using a curvilinear regression analysis involved tracing the animal in lateral aspect. Since the posterior artic• ulation of the cephalothorax has a slight thickening in the mid- dorsal line, it is an easy point to find in a photograph of the animal and was consequently chosen as a reference point. The second reference point was the posterior surface of the base of the rostral filament. Animals chosen for analysis were photo• graphed in lateral view. The negatives were projected onto graph patper wdth 1mm divisions by means of a photographic enlarger. Magnifications were kept consistent by projecting a scale onto the graph paper and setting the enlarger so that one division on the projected scale always covered the same number of divisions oh the graph paper (Fig. 2). X and Y axes were chosen so that the Y axis ran between the two reference points (Fig. l). The point at the base of the rostral filament.on the posterior surface was placed so that it would lie on the intersection of two axes on the graph paper, and the origin of the X and Y axes was always set 1 cm below this point since the head outline extended slightly anterior.! Thus, the base of the rostral filament at the posterior surface always had the coordinates X _ 0 and Y = 10. Once the reference points were aligned on the graph paper, the outline of the lateral view of the cephalothorax was traced from the anterior surface of the base of the rostral filament to the posterior articulation. Values of X and corresponding values of Y were then read from the graph until a maximum value of X was reached. Consequently only the anterior portion of the cephalothorax was analysed, and it is this portion that appears different. The X, Y values were then subjected to a regression analysis where A regression coefficient was calculated for each animal. Length measurements of the animals were made by placing specimens on their sides and measuring the length of the prosome fr'om the anterior end of the cephalothorax to the posterior end of the last prosome segment. Individual length and width measure• ments of each segment were also recorded. The length and width of each segment of the urosome was recorded. For the caudal rami, the width was measured at the articulation with the last urosomal segment. The length was measured from this anterior articulation to the insertion of the posteriormost seta. Figure 2. Diagram of the process of headshape measurement showing the orientation of the cephalothorax. The appendages of the cephalothorax are much alike in the local species and are morphologically similar to other species in the genus. The length and width of each antennule segment was determined; for the antennae, the length and width of the second segment of the exopodites was measured. Measurements were taken of those swimming leg segments that appeared proportionately different. Width measurements were made when it was felt width to length ratios of a particular segment might show a proportionate difference between specimens. Lengths of exopodite segments were measured from the proximal articulation surface to the distal articulation surface. Total length of the exopodites was determined by summing the individual length measurements df each segment. Teeth on each coxopodite were counted. Male specimens of Calanus show the greatest amount of vari• ability in the lengths of the left and right exopods, and the degree of asymmetry is a common taxonomic character (Brodsky, 1965? Jaschnov, 1955). For females, the legs are symmetrical, but the first segment of the exopodite has been reported to vary in proportion between C. finmarchicus and C. helgolandicus (Jaschnov, 1955). The degree of asymmetry in the local species was measured by dividing the length of the right exopodite by that of the left. Length measurements of individual exopod seg• ments were proportionately different in length. It was felt that proportionate differences could be elucidated by using a measure• ment common in proportion to most species of Calanus. This measurement would serve as a common denominator in any ratios -20- v
1 formed, and make it possible to directly compare features which
vary in degree among the toothed species of Calanus.
Based on his work of Calanus species around the world, Bary
(personal communication) has suggested that the proportionate-
lengths of the fourth and fifth prosome segments (cephalothorax
considered the first) show very little variation (Figs. 1 and'
8^10). This was tested on the local species by forming ratios
with the prosome segments. The length of any one prosome segment
was placed in the numerator and the sum of the lengths of prosome
segments one through five was placed in the denominator. The
last or sixth prosome segment was deleted because its length is
hard to measure accurately and would therefore introduce a samp•
ling error in the analysis. The proportionate lengths of the'
fourth and fifth prosome segments were found to be identical in
the local species and were chosen as the common measurement for
forming ratios with the exopod segments of the fifth legs. The
length of each exopod segment was divided by the sum of the ;
lengths of prosome segments four and five for each animal.
Measurements were analyzed to determine any significant dif•
ferences. Student's "t" tests were used to determine the signi•
ficance of differences in the means of measurements between the
two^forms described by Shan (1962), and variances were tested by
the F test. Regression analyses were used to determine the
dependence or independence of the differences found and prosome
length. A P value of 0.01 was used in all tests.
A complete set of drawings to illustrate the appendages arid
the body shapes was made with a camera lucida. These are included in AppendixII, with the morphological description of the local animals.
Distributional Survey
Between I965 and 196? several long cruises were completed covering a range from 330 north to 59° north along the west coast of North America (Fig. 3). In the waters north of Vancouver,
British Columbia, sampling was carried out in Georgia Strait, Bute
Inlet, Knight Inlet, Johnston Strait, and Queen Charlotte Strait.
In the late summer of I965 a cruise on CNAV ENDEAVOUR through the Inside Passage of Alaska provided the opportunity to sample many of the inlets of southeastern Alaska including Glacier Bay, a cold inlet located at the northernmost part of the Alaskan archi• pelago. The cruise included stations in the Northeast Pacific, along the outer coast of Alaska, and in Dixon Entrance and Queen
Charlotte Sound. South of Vancouver, a single cruise in early
1966 on CNAV ENDEAVOUR was arranged to example the region"from the mouth of Juan de Fuca Strait to San Diego, California. The cruise was set so that the edge of the continental shelf (100 fathom line) was criss-crossed in legs of approximately 100 miles in length. This provided the opportunity to sample over the conti• nental shelf, the continental slope, and deep oceanic water. Sta• tions were also set over deep regions such as the Monterey Canyon and the Mendocino Escarpment.
Since the cruises to Alaska and San Diego ran continuously over a 24 hour day, samples along the range were taken at a vari• ety of different times, and it was possible to obtain some idea
of the effect of hydrographic conditions on the vertical migra• tions of the toothed species of .Calanus* Samples taken on cruises to the inlets of southern British Columbia were generally during daylight hours, but the study in Indian Arm included 24- hour sampling of one station in order to study the vertical migration patterns in detail. Table I is a list of oceanographic stations occupied in this study. For ease in description place names are used in the text while the exact geographical coordinates of the sta• tions may be determined from this Table. Station numbers or letters in parentheses are the official designation for the sta• tion as given in the data reports of the Institute of Oceano• graphy at the University of British Columbia. Stations from which samples were drawn for the morphological, distributional and ecological analyses are indicated by an asterisk in the ap• propriate columns. .
Ecological Study
The program was designed to provide data about the forms of toothed Calanus described by Shan (1962) which would help in answering the following questions: 1. Do both forms occur in one stage or another throughout the year? 2. Are the yearly cycles, particularly the time of breed• ing and spawning, the same for both? 3. Is the time of reproduction the same in other areas? TABLE I
STATION LIST
M=Morphology study; D=Distributional study; E=Ecology study.
STATION LATITUDE LONGITUDE N D E
Gla. Bay 8 58 41.2N 136 11. OW * tt Icy St. 3 58 14.7 135 24.3 * * « Lynn Canal 10 58 40.3 135 06.9 * Icy St. 1 58 18.0 136 19.2 tt »
Behm East 18 54 42.0 131 10.0 tt » Clarence 22 54 42,5 131 44.6 Behm East 11 55 15.1 131 02.7 # » Behm East 2 55 59.0 131 16.0 Behm West 7 55 39.2 131 45.4 «
Clarence 14 55 26.5 131 58.5 • Clarence 6 56 01.6 132 45.0 tt
Sumner 10 56 03.0 133 48.7 « « Lynn Canal 40 56 17.5 134 26.5
Lynn Canal 30 57 02.8 134 41.8 #
Lynn Canal 20 57 49.8 134 51.7
Pacific A 57 48.0 137 05.0 » « Pacific B 56 04.0 135 29.5 * tt # Pacific C 55 28.0 134 58.0 # « « Pacific D 54 30.0 134 02.0 * Pacific E 54 28.0 132 25.0 «
Pacific F 51 10.0 129 50.0 « « Pacific G 51 04.9 128 12.0 * STATION LATITUDE LONGITUDE N D E Johnston St 3. 50 30.ON 126 20. 9W * # Queen Char. St. 50 45.5 127 20.0
# * •H- Knight Inlet 3 5° 39.7 126 05.1 Sutil Chan. 1 50 05.0 125 07.0 * * Pacific 1 48 '25.0 124 50.0 * Pacific 2 48 00.0 126 08.0 * * Pacific 3 47 38.2 . 125 37.0 * Pacific 47 13.0 124 53.0 * * Pacific 5 47 00.0 124 30.0 * Pacific 6 46 35.0 124 34.5 Pacific 7 45 20.0 124 50.0 * * • Pacific 8 44 41.5 124 34.0
Pacific 9 43 45.0 124 20.0 # Pacific 10 43 25.0 124 37.5 * Pacific 14 40 59.5 124 20.5 * Pacific 15 40 27.0 124 36.5 * Pacific 16 40 10.0 124 55.0 * Pacific 17 39 29.0 124 27.0 * Pacific 18 38 45.2 123 45.0 «
Pacific 19 38 15.3 123 10.0 Pacific 20 37 48.0 122 31.0 * Pacific 21 37 51.0 122 26.0 * Pacific 22 37 00.0 122 20.0 Pacific 23 36 42.0 122 06.0 # » * Pacific 24 36 17.0 122 03.0 •a * Pacific 25 34 45. ON 120 50. OW * « Pacific 26 34 25.0 120 15.0 « Pacific 27 33 , 55.0 119 50.0 Pacific 28 33 35.5 119 11.0 * Pacific 29 33 09.5 118 20.0 » Pacific 30 32 45.0 117 31.0 * * * Pacific 33 37 47.5 123 15.0 # Pacific 34 40 20.0 124 27.0 •* * Pacific 35 42 25.0 124 45.0 * Pacific 36 42 50.0 124 45.5 *• « Pacific 39 46 15.0 124 33.0 » Unimak Pass 54 00.0 165 00.0 * * Georgia St. 1 49 15.0 123 41.0 # Saanich In. 48 38.0 123 30.2 * * Malaspina St. 49 34.0 124 09.0 * Bute In. 50 24.0 125 04.7 Juan de Fuca 7 48 19.0 124 11.9 « Georgia St 2 49 51.0 124 50.0 * correlation between vertical distribution and the pre• vailing hydrographic conditions? 5. What happens to the spatial relationship of the popula• tions in the vertical direction over a 24 hour period? 6. Are the two forms reproductively isolated and therefore good species as defined by Mayr (1942)? 7. Is there any association between one form or the other to particular water bodies in the sense applied by Bary (1963)? Indian Arm, an inlet near Vancouver, British Columbia, was chosen for the ecological study (Fig, 4). Relative abundance of both species over the year, physiography of the inlet, and the proximity of Indian.Arm to Vancouver were the main reasons for choosing this area. Preliminary sampling indicated that both populations of toothed Calanus were breeding populations, and that their abundance during the year did not appear to be affected by the large blooms of a related non-toothed species, C. plumchrus. that occur in the Strait of Georgia and other in• lets in the region. The inlet is a relatively deep basin with a maximum depth of 245 meters and a shallow sill depth of approxim• ately 30 meters (Q'ilmartin, 1962). The mouth of the inlet is comparatively narrow and adjoins Vancouver harbor which is sep• arated from the Strait of Georgia by a second narrow entrance, wFJiis.tsNacfeQwg,M On the basis of these boundary conditions, it was felt that immigration and emigration on the part of Calanus might be restricted, and any continuing research program could reason- Figure 4. Map of Indian Arm, British Columbia, showing location of station number 9»
STN. 9 ably assume that the same populations were being sampled on each cruise. The proximity of Indian Arm to Vancouver became important when collecting live animals and transporting them to the laborat• ory for further work. By keeping the amount of time the animals are kept in collecting containers to a minimum, there is a lower risk of exposing the specimens to conditions which may be damag• ing and deterrant to survival. A station was selected over the deepest part of Indian Arm for this work, station 9 of Figure 4. Vertical hauls were taken monthly from October 1966 to April 1968. These included the whole water column from approximately 200 meters to the surface. Additional hauls at any one sampling period provided live animals for laboratory experiments. From February I967 to March 1968, a monthly series of stratified tows was taken at noon, 1200 hours, With the nets sampling at eight different depths to include the major portion of the water column. Twenty-four hour stations were run in February, May, July, Augusts and September of I967, and in January, February, and March of 1968. The pattern of sampling was the same as for the mid-day stations, except that samples were taken every six hours. Preserved samples were placed in plastic petri dishes with an engraved grid forming 1 cm squares. This grid facilitated counting by enabling the sorter to keep track of the counted and uncounted portions of the dish. The numbers of males, females and stage-V copepodites of both forms were recorded, and in the later samples the numbers of females with attached spermatophores were also counted. Samples taken with the Clarke-Bumpus nets were not sub- ; sampled prior to counting, but samples obtained from vertical' hauls were split into four equal portions with the aid of a cylindrical sub-sampler (Fig. 5). During the sub-sampling pro• cedure, the entire plankton sample was poured into the cylinder without the partition. After thoroughly stirring the sample, the partition was immediately placed in the tube. Subsequently any number of the chambers could be emptied into an appropriate container and the sample counted,. In order to check the effici• ency of this sampler, several entire plankton samples were count• ed by counting all the specimens in each chamber, then by summing the counts for the four chambers and dividing by four an ex• pected number of animals per chamber was derived. Applying a chi-square test the effectiveness of the sub-sampler in dividing the original sample into four equal parts was determined. For toothed Calanus, the instrument consistently gave acceptable 're• sults when there were at least six specimens per chamber, but for larger organisms such as etuphausiids, the discrepancy in counts between the four chambers was too large to be acceptable and the trapping of individual specimens under the partitions was a problem. ' For an estimate of the relative amount of food available at various depths, analyses of chlorophyll A were run in February and March of 1968 by the method of Strickland and Parsons (1965). Since chlorophyll A is common to all phytoplankton it was felt unnecessary to determine the amounts of the other chlorophylls. The turbidity of the surface water was also used as an indication
of the degree of primary productivity during these two months.
Water samples were obtained from standard hydrographic depths with
Atlas bottles. In March 1968, nets with a mesh aperture of ?6 microns square were attached to Clarke-Bumpus frames, and an addi•
tional series of tows at all eight depths was completed. In addi•
tion to those taken for chlorophyll analysis, samples were also
taken from the Atlas bottles and preserved in Lugol solution for
later identification and estimation of the distribution of phyto- plankton over the 200 meter* water column. Specimens of Calanus
captured in the fine mesh nets were subjected to gut content anal• ysis to determine the types of food organisms ingested.
For the moulting and breeding experiments, Stage-V copepodites
of each form described by Shan (1962) were placed in plastic boxes.
These boxes were divided into 24 compartments each with a 100 ml
capacity, and one specimen was placed in each compartment. An
extra stock was kept after each collecting cruise in the event of
failure:.;:, or mishap in the experimental boxes. Specimens -were kept
in'4 liter beakers with 25 to 30 animals per beaker.
The compartmented boxes were placed in different temperatures as the particular experiment dictated. Temperatures of 5, 10 and
15°C were used. Within each temperature there were two boxes at any one time. One wasua control with no food organisms the other an experimental box with food organisms. To provide a second con•
trol , an experiment at 5°C was always run simultaneously with an
experiment at one of the other temperatures. The phytoplankton food source consisted of Dunaliella st>. and phaeodactylon tricomutum. Boxes were checked every two or three days, and the number of specimens which had moulted to the adult stage was recorded. After moulting, adults were placed in 4 liter beakers for breed• ing experiments by the following scheme:
Large Form males x Large Form females Small Form males x Small Form females Large Form males x Small Form females Large Form females x Small Form males
The breeding experiments were conducted at 5° and 10° C. Fertilization was confirmed by dissecting out the spermathecal sacs of females and squashing them in aceto-orcein nuclear stain. Morphology
Detailed descriptions of the toothed Calanus sp. forms noted by Shan (1962) are included as an appendix. Morphological differ ences between the two are presented in this section. Table I shows the stations along the west coast of North America where sub-samples of animals were taken for use in the morphology study
Prosome
Two size groups of toothed Calanus are evident.although overlaps in length distribution occur, particularly in adults (Fig. 6). Wales are generally smaller than females. On the basis of prosome length measurements of 50 animals of each sex the mean length values were determined and are presented in Table II with the results of the T test on the data.
A change %n the average length of Shan's Large Form (1962) was noted whil§ sorting specimens from different regions of the west coast. Measurements of prosome length reflect this change, resulting in a decreased length toward" the southern extent of the range. The results are summarized in Table III. Figure % presents the change in prosome length for the Large Form, and length values reported by Park (1968) and by Jaschnov (1955) are included for'comparison. A regression analysis indi• cated a significant change of prosome length on latitude based, on the animals measured, in this study. The calculated regression Figure 6. Prosome lengths.
Large Form (males) 20- 15- 10- 5-
1S Small Form (males) 10- 5-
o 15- Large Form (females) | 10- -c5 5- ^ 15-1 Small Form (females) I 10- E 5-
15- Large Form (stage-V) 10- 5-
15- Small Form (stage-V) 10-
5- •
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 Prosome length (mm) Pigure 7. Prosome lengths: Large Form vs. latitude; open circlest one animalj closed circles: two animals; open tri• angles: three animals; closed trianglesi four or five ani• mals; for females, A-F: data from Park (1968) along meridi• an 154° W. longitude, Gi data from Jaschnov (1958) from sea of Okhotsk; for males, A-C from Park (1968), Di Jaschnov (1958); for stage-V copepodites, A: data from Jaschnov (1958). ANALYSIS OF PROSOME LENGTHS
FORM. SEX MEAN VARIANCE CALC. T T(.Ol)
Large females 2.9 0.027 16.62 2.63 Small females 2.4 0.024 Large males 2.8 0.010 29.47 2.62 Small males 2.2 0.013 Large Stage-V 2.6 0.022 14.55 2.66 Small Stage-V 2.1 0.016 *MEAN PROSOME LENGTHS FOR LARGE FORM ALONG RANGE SAMPLED
STATION FEMALES MALES C-V
Unimak Pass 3.1 mm — WWW Glacier Bay 3.2 3.1 mm 2.9 mm Icy Strait 2.9 2.9 2.8
Lynn Canal 3.1 2.7 2.9 Pacifici Stn B 3.1 2.6 2.8 Pacific: Stn C — 2.6
Queen Charlotte Sound 3.0 2.8 2.7 Queen Charlotte Strait 2.8 2.7 2.7 Knight Inlet 3.2 2.8 2.8 Sutll Channel 2.8 2.8 2.8 Indian Arm 2.9 2.8 2.6 Pacific: Stn 1 2.6 2.6 — Pacific: Stn 2 2.7 2.7 2.5 Pacific: Stn 7 2.7 2,7 2.6 Pacific: Stn 10 2.7 — 2.4
Pacific: Stn 36 2.6 ——— Pacific; Stn 34 2.7 2.7 ———
* Sample size for each class was 5 except for Indian Arm, where 10 of each sex and 10 stage-V copopodites were measured. line is on each graph, and the range of prosome lengths for each station may be determined from this diagram. In the case of Indian Arm, a random sample of 10 males, females, and Stage-V copepodites was drawn for the purpose of comparison to other areas. Similar measurements on Shan's Small Form, collected from a series of stations along the west coast (Table I and Table IV), do not ex• hibit the same variation in prosome length with latitude, although the Stage-V copepodites are somewhat smaller at the southernmost portion of the range sampled in this survey. Table IV summarizes the data for this form. The results of the analysis for possible variation in the proportionate lengths of the prosome segments are presented, in Table V. The variation between the two forms is slight and sta• tistically insignificant. The ratio, segment 1/sum of segments 1 to 5» nas the greatest variation within and between forms, and may reflect the variation in head shape evident between the two forms. The ratios formed from segments 3, 4, and 5 are the most consistent. A similar analysis of specimens from the various sta• tions along the range of each form showed no significant change in proportions.
Head Shape
The shape of the anterior end of the cephalothorax in lateral view differs between the two local forms of toothed Calanus. The Stage-V copepodites appear much like the adult females making it possible to distinguish the head shapes of the two forms at this stage. Large Form females and Stage-Vs have a rounded head, in -RO•
*MEAN PROSOME LENGTHS'. FOR SMALL FORM ALONG RANGE SAMPLED
STATION FEMALES MALES C-V
Sutil Channel 2.5 ma 2.3 mm 2.2 mm Indian Arm 2.4 2.2 2.1 Pacifies Stn 7 2.5 2.3 Pacific: Stn 10 2.2 2.0 1.9 Pacific: Stn 36 2.2 . 2.0 1.9 Pacific: Stn 34 2.4 2.1 1.9 Pacific: Stn.:23 2.4 2.1 1.9 Pacific: Stn 24 2.5 2.2 1.9 Pacific: Stn 30 2.4 2.0 1.7
* Sample size for each class was 5 except for Indian Arm, where 10 of each sex and 10 stage-V copepodites were measured. TABLE V
PROSOME ANALYSIS
FORM (Sex) SEG.l/SEG.1-5 SEG.2/SEG.1-5 SEG.3/SEG.1-5 SEG.4/SEG.1-5 SEG.5/SEG.1-5
LARGE N _ 34 N = 34 N = 34 N = 34 N 34 (females) X re0.45 X = 0.20 X = 0.13 X 0.12 X = 0.10 s — 0.013 s _ 0.007 s = 0.007 s — 0.005 s as 0.005
SMALL N — 35 - N — 35 N 35 N _ 35 N — 35 (females) X as 0.48 X 0.19 X = 0.13 X _ 0.11 X as 0.10 s _ 0.013 s = 0.011 s 0.009 s 0.003 s as 0.008
LARGE N — 35 N — 35 N _ 35 N — 35 N as 35 (males) X = 0.52 X = 0.16 X — 0.12 X 0.11 X s= 0.09 s = 0.014 s ss 0.010 s 0.006 s — 0.004 s ss 0.006
SMALL N — 35 N _ 35 N — 35 N — 35 N as 35 (males) X = 0.52 X _ 0.17 X = 0.12 X == 0.11 X = 0.09 s = 0.020 s 0.011 s rt 0.008 s as 0.008 s ss 0.009
LARGE N _ 25 N — 25 N — 25 N — 25 N as 25 (G-Y) X _ 0.45 T 0.20 X = 0.13 X = 0.12 X s= 0.10 s as 0.012 s _ 0.011 s _ 0.009 s SB. 0.007 s 0.005
SMALL N — 25 N — 25 N — 25 N _ 25 N _ 25 (C~Y) X _ 0.4? X _ 0.19 X = 0.13 X _ 0.12 X as 0.09 s = 0.017 s — 0.014 s = 0.010 s S= 0.011 s — 0.007 contrast to the more protuberant head of comparable stages of the Small Form (Figs. 8 and 9). The males of both forms have head shapes that are more protuberant than females and. stage-V's, but the degree of protuberance differs between males of each form (Fig. 10). The results of head shape measurements using the method of regression are presented in Fig. 11. The distribution patterns for females and stage-V's show the greatest difference, a fact that may also be determined from the photographs of the animals. The males have more similar distribution patterns, but the degree of spread is much smaller, possibly indicating a lesser degree of variation among males within each form. Table VI summarizes the statistical results for the head shape data. A regression analysis where head shape was considered the dependant variable and prosome length the independent variable failed to show any significant relationshipbbetween these two features. The conlusion is that head shape is independent of size.'
Urosome
Width and length measurements of each urosome segment were made on 2? males and 27 females of each form. The segments were numbered consecutively with the proximal or genital segment designated number 1. Width to length ratios were calculated from the data. Mean values of the ratios for each segment were compared between the same sex of both forms. Segments 1, 2 and 3 differed between females, and segments 3 and 4 differed between Figure 8. Photograph of females: Small Form on left, Large Form on right. Note attached spermatophores. Figure 9. Photograph of Stage-V copepodites; Large Form on left; Small Form on right.
••MP?*' m
Figure 11. Head shape distributions.
Small Form (females)
Large Form (females)
Small Form (males)
Small Form (stage-V)
Large Form (stage -V) _
o. i -i i • * i -H i -i— i ' i ^ ' .05 .07 .09 .11 .13 Regression coefficient RESULTS OF T TEST ON HEAD SHAPES
FORM SEX MEAN VARIANCE CALC. T T(.Ol)
Large Form F 0.11 0.7 x 10-^ 11.69 2.66 Small Form F 0.08 1.4 x 10 Large Form M 0.0? o.6 x io-;* 6.64 2.66 Small Form M 0.06 0.4 x 10-4 Large Form C-V 0.11 2.0 x 5.14 2.66 Small Form C-V 0.08 3.0 x 10"^
TABLE VII ANALYSIS OF WIDTH/LENGTH RATIOS OF THE UROSOME SEGMENTS
FORM SEX SEGMENT MEAN VARIANCE CALC.T T(.Ol)
Large Form F 1 0.85 0.006 3.94 2.67 Small Form F 1 0.93 0.006 Large Form F 2 1.14 0.002 7.36 2.67 Small Form F 2 1.28 0.008
Large Form F 3 1.41 0.010 5.38 2.6? Small Form F 3 1.56 0.011 Large Form M 3 1.11 0.007 6.63 2.67 Small Form M 3 1.22 0.001 Large Form M 4 1.32 0.006 7.33 2.67 Small Form M 4 1.49 0.008 Flgure 12. Urosome ratios, distribution.
Small Form (females) 10. urosome segment 1 5.
0 Large Form (females) 10. urosome segment 1 5. 0 hu o ' in Small Form (females) urosome segment 2 1 d
Large Form (females) 15. urosome segment 2 10.
5.
0 Small Form (females) 10. urosome segment 3 5-
0 1 I
i n Large Form (females) d i n o urosome segment 3
r Small Form (males) 10. urosome segment 3 5. 0 Large Form (males) 15. urosome segment 3 10.
5. 0 Small Form (males) 10H urosome segment 4 5^
0 Large Form (males) urosome segment 4
O c n o < —1 T 1——I——i 1— i——I——I— II 1 r 0.7 0.9 1.1 1.3 1.5 1.7 Ratio of width/length t males. Results of the analysis are summarized In Table VII.
The ratios are plotted as histograms-in Figure 12. To ar• range the data into convenient class intervals the ratios were rounded to the nearest 0.1 before plotting, although the stu• dent's "t" test was run on the data before rounding.
A regression of the width/length ratios on prosome length indicated the proportions were Independent of size. Animals taken from various points along the range (Table I).were measured and analyzed in the same manner. No apparent change in proportions over the range sampled was evident.
Swimming Legs
In the local forms the inner surface of the first segment of the exopodites on the second and third swimming legs was curved in some specimens and not in others. Initially it was thought that this would be a distinguishing characteristic be• tween the two local forms. In fact, it appears to be a feature that is present or absent depending on the orientation of the leg on a microscope slide. Width and length measurements were determined and ratios of width to length were calculated. No significant difference in these proportions was noted, and the degree of curvature can be misleading. However, if the legs are observed before mounting under a cover slip, the curvature of this inner border can be seen to change as the leg is turned.
The degree of asymmetry in the exopods of the fifth swim• ming legs of the males is greater for the Small Form than for Large Form Small Form Fifth swimming legs (males) the Large Form (Fig. 13). The results of measurements and stat• istics are presented in Table VIII. Figure 14 shows the distribu• tions resulting from the ratio of length of right exopod/length of left exopod for the two forms. When regressed on prosome length, the ratio Indicated that the degree of asymmetry, between the left and right exopodites was independent of size.
The results of the ratios where the individual exopod seg• ments of the left fifth leg were divided by the sum of the lengths of prosome segments 4 and 5 are presented in Table IX A. The re• sults indicate that the proportionate length of segment 1 and of segment 2 of the left exopod change significantly between the two forms (Table IX B). The proportionate length of segment 3 does not vary significantly.
The toothed Calanus spp. have been divided into two groups on the basis of the relation of width to length of the first and second segments of the left exopods of the fifth legs of males
(Brodsky, 1959). Values for this ratio on specimens measured in this study are presented in Table X.
With the exception of Queen Charlott Sound, the values of
Table X are all lower than those reported by Brodsky (1959) for
Pacific and Sub-Arctic Calanus spp., and a certain degree of variability is evident in this study when specimens from vari• ous points along the range are measured. It would appear that different populations of the same species can vary in this respect.
The degree of asymmetry and the proportionate lengths of the first two segments of the left exopods in the fifth legs for animals measured in this study did not vary with latitude. ANALYSIS OP ASYMMETRY IN FIFTH LEGS OF MALES — Statistical Re• sults of the ratio: length right exopod/length left exopod—
FORM N MEAN VARIANCE CALC. T T(.Ol)
Small 46 0.74 6 x lO"^ 21.03 2.617 Large 46 0.85 5 x^iO-^
TABLE IX A ANALYSIS OF PROPORTIONATE LENGTHS OF EXOPOD SEGMENTS IN THE FIFTH LEGS OF MALES
Left Exopod FORM SEGMENT 1 SEGMENT 2 SEGMENT 3
Small N=27 N=27 N=27 X=6.42 X=4,04 X=7.75 s=0.57 s=0.62 s=0.34 Large N=27 N=27 1=27 X=6.47 X=5.62 s=0.38 X=3.82 =0.30 s s=0.73 Right Exopod
FORM SEGMENT 1 SEGMENT 2 SEGMENT 3
Small 1=27 N=27 N=27 X=4.28 X=4.19 x=5.05 s=0.40 s=0.34 s=0.4l Large N=27 N=27 N=27 X=4.38 x=4.l4 X=4.99 s=0.21 s=0.19 s=0.27 T TEST ON THE PROPORTIONATE LENGTHS OF THE EXOPOD SEGMENTS ON THE LEFT FIFTH SWIMMING LEGS OF MALES
FORM SEGMENT N MEAN VARIANCE CALC.T T(.O:
Small 1 2? 7.75 0.38 9.12 2.67 Large 1 27 6.47 0.15
Small 2 27 6.42 0.10 6.48 2.67 Large 2 27 5.62 0.32
Small 3 27 4.04 0.12 1.43 2.67 Large 3 27 3.82 0.53
TABLE X
WIDTHsLENGTH VALUES OF FIRST AND/OR SECOND SEGMENTS, LEFT EXOPOD, FIFTH SWIMMING LEG, MALES.
LOCATION LARGE SMALL
Indian Arm, B.C. 1:2.4 1:2.4
Glacier Bay, Alaska 1:2.7
Queen Charlotte Sound, B.C. 1:3.2
Pacific Station #10 1:2.8
Pacific Station #24 — 1:2.5
Pacific Station #30 1:2.9
Pacific Station #34 1:2.3 1:2.6 Large Form (males) ct -P- 12-| tr. CO 10. 3 to
8 K* O
6 CD a 4. CD (5? T3 ct co 3* 2. 0 4
C 0 Small Form (males) 1 ct 0 12J CD CD co M • O •d o p< 1 *J \ M z 6. CD tS 4- ct 3* 2. H» CD M> 0 ct to CD I 0.66 0.70 0.75 0.80 0.85 0.90 X Ox o I Ratio of length right exopod/length left exopod o The exopods of the fifth legs of females of both forms were subjected to the same type of analysis as were those of the males. The results of the ratios where the individual lengths of the exopod segments were divided by the sum of the lengths of prosome segments k and 5 indicate that the proportionate length of the distal or third exopod segment differs between the two forms (Table XI A). Table XI B summarizes the "t" test on the data. The distributions are presented in Figure
15. A regression of this ratio on prosome length indicated that the proportionate length of this third segment is inde• pendent of size on the animal and further, no significant varia• tion with latitude was noted for either form.
Since the spinose process on the anterior distal surface of the basipodites on the fifth swimming legs appeared to vary in length between the two forms, length measurements were taken.
The results are presented as a histogram (Figs. 16 and 17).
This spine is always shorter in specimens ofthe Large Form and is sometimes present only as a small bump. In the Small Form it is always evident and much longer. The difference in lengths of this process between the two forms is significant (Table XII), and the values of the length measurements do not vary signifi• cantly with latitude. A regression analysis indicated that the length of this process is independent of size of the animal with• in the size ranges measured. This process is found on males, females and Stage-V copepodites, and is useful in distinguishing the two forms particularly when the exopods ofrtheffifth leg have been broken off. CD H o» •O CD
ro o^B
4H CO CD CO h» - 3 p. M- Ct O 3* P H- ct H CD P-
H» CD CD M O cfd o CD a oM ca •d CD o cn p.. • \ •d o CO o s CD
CO CD
CD 5.0 5.5 6.0 6.5 3 ct Ratio of length exopod segment 3/sum lengths prosome segments 4+5 CO i ON I Flgure 16. Femalest spinose process, length vs. frequency. Open bars indicate left leg.
J L 00 E E OJ i_ o LL £ mm CVJ o cn E c O if) OJ c O !_ 00 U if) (0 CU (fl o c OJ — o Y/////////M s: cn c (U 00 CD I- —I 1 1 1 1 1 1 1 1 1 1 1 1 r ^C\JO00(O^C\JOC\IO 00(D-^OJO 9|Dnp!Aipui jo jaqujnN o Small Form (males) a 12-| *a a H 10. 8. 1 CO fiT * 6. H> 6. H CD 3 4. W ct 2. V < O. CO 1 - —i 1— 8 10 12 14 16 18 20 22 24 —i— 28 26 Length of spinose process (microns) CD CD 3 o I 00 I LEGS OF FEMALES LEFT EXOPOD FORM SEGMENT 1 SEGMENT 2 SEGMENT 3 Small N = 2? N 26 N = 26 X = 3.92 X 3.87 X = 6.19 s = 0.31 s 0.30 s = 0.41 Large N = 27 N 27 N = 27 X = 3.92 X 3.63 X = 5.64 s = 0.16 s 0.18 s = 0.28 RIGHT EXOPOD Small N 27 N = 23 N 22 X 3.90 x + 3.88 X 6 s = 0.28 s .14 x 0.29 0.51 Large N 27 N = 27 N 27 X 3.95 X 5.65 s 0.20 X = 3.62 s s = 0.19 0.28 TABLE XI B T TEST ON PROPORTIONATE LENGTHS OF EXOPOD SEGMENT 3 ON THE FIFTH SWIMMING LEGS OF FEMALES FORM N MEAN VARIANCE CALC . T T(.Ol) LEFT EXOPOD Small 26 6.19 0.17 5.58 2.68 Large 27 5.64 0.08 RIGHT EXOPOD Small 22 4.17 2.69 Large 27 6.14 0.26 5.65 0.08 T TEST ON MEAN LENGTHS OF THE SPINOSE PROCESS ON THE FIFTH OF MALES AND FEMALES FORM SEX I MEAN VARIANCE CALC T T(.O; LEFT LEG Small female 46 19.61 8.64 10.83 2.63 Large female 46 11.83 15.09 Small male 46 18.40 7.07 18.65 2.63 Large males 46 7.61 8.42 RIGHT LEG Small female 46 20.11 10.81 12.38 2.63 Large female 46 11.12 13.61 Small male 46 18.73 9.69 . 12.21 2.63 Large male 46 9.89 14.2? A map showing station positions is included in the materials and methods section, while a list of the stations with their geo• graphic coordinates is presented in Table I. Figure 18 outlines the distributions for both forms in the area sampled. The approximate boundaries for the region of overlap, on the basis of samples analysed in this study, are from 40° to 42° N latitude. The Large Form was found in samples from Glacier Bay, Alaska, in the north to Cape Mendocine, Calif• ornia, in the south. The Small Form was found in samples from Johnston Strait, British Columbia, in the north to San Diego, California, in the south. No samples were available from the west coast of Vancouver Island, and it must be assumed that the northern extent of the Small Form occurs in this region. Temperature and salinity data from selected stations were used to characterize the physical environment along the portions of the ranges of both forms covered by this study. Stations lo• cated in the inland waters and fjords were not used because these regions are greatly influenced by inshore processes (e.g., freshwater run-off) which makes direct comparison to open ocean stations difficult. Temperature and salinity data from several stations along the outer coast were omitted for the sake of clarity in the diagrams. Such stations did not differ from respective adjacent stations, and the hydrographic pattern de• picted by the plotted stations is representative for the time of the survey. Figure 18. Map showing distribution of both Large and Small Forms. Horizontal striations indicate range of Large Form; vertical striations indicate range of Small Form. Figure 19. T, S diagram of west coast data. 00 p — a a B ! n o E u >, D z o uo «3 U c > 1) O co z g-8 • E 2 o ; L. a 1/1 a c a u _ - u ^ < 5 U U o O C OO GO U Figure 20. T, S, P diagram of west coast data. Circles indicate Large Form; squares indicate Small Form. Station Pacific 34, located inshore at Cape Mendocino, was plotted to show the effect of upwelling in the Immediate region. No stratified plankton tows are available for this station although a vertical haul revealed the presence of both forms. All other stations plotted Included stratified plankton tows taken in conjunction with hydrographic samples. Plots of temperature and salinity for the stations are presented after the method of Bary (1963) with the exception that the vertical as well as the horizontal changes in both fac• tors are considered (Fig. 19). Arbitrary boundaries indicate the major changes in hydrographic characteristics In the hori• zontal direction. Using the method. ofTBary (1964), these bound• aries are then superimposed on the temperature-salinity-plankton (TSP) diagrams (Fig. 20) to Indicate the general association between the water masses and the two forms of Calanus. In interpreting the T-S diagram (Fig. 19), it should be recalled, that the Alaskan and northern British Columbia stations were taken in August whereas those off the coast of the continent• al United States were taken in February. The seasonal effect, with respect to temperature and salinity, is mainly in the, sur• face waters with the deeper water off Alaska similar with respect to temperature to the water north of Cape Mendocino but slightly more dilute. Four main hydrographic regions are defined (Fig. 19). The first includes the relatively cool, dilute water off southeastern Alaska and northern British Columbia. The second includes the water off the coast of the continental United States, from the mouth of Juan de Fuca to a point approximately 60 miles north of Cape Mendocino, California, and is characterized by slightly more saline water. Deeper water in this area differs from the more northern water in the somewhat higher temperatures. The third region is in the vicinity of Cape Mendocino. The water is markedly warmed in the upper 100 meters and the salinity of the surface and sub-surface layers is notably higher. The fourth region includes the stations south of Cape Mendocino to San Diego and is characterized by warm relatively saline water. The vicinity of Cape Mendocino represents a region of change between the northern and southern waters, and appears as a transitional zone on the T-S diagram (Fig. 19). Station Paci• fic 14, about 40 miles north of Cape Mendocino, is similar to the stations of the second region defined above. Station Paci• fic 15, off Cape Mendocino, and Station Pacific 17, about 60 miles south, are similar to each other but distinctly different from the more northern stations with regard to temperature al• though the salinity of the surface and sub-surface water is slightly higher. Station Pacific 18, which is approximately 50 miles south of Pacific 17, has the characteristics of the more southern stations of the fourth region. There is little change in properties between Station 18 and Station 30 off San Diego. Two of the stations plotted are different from the others in the respective regions. Pacific St&tion l, in the mouth of Juan de Fuca Strait, is characterized by relatively cool and dilute water in the upper 75 meters, probably a manifestation of the large amount of freshwater run-off from the Fraser River (Tully, 1942; Lane, 1962). Below this depth, the temperature- salinity plots are similar to those characteristic of the Pacific coast of Washington. Station Pacific 34 is inshore of Pacific 15 off Cape Mendocino, hut it is different from the latter, being characterized by water similar to that found deep• er at the more northern stations. The seemingly anomalous qualities are probably the result of localized upwelling near shore. The Large Form of Calanus sp. (Shan, 1962) is commonly found throughout the water of region 1 (Fig. 20) with the high• est concentrations in the warmer surface layers between approxim• ately 9 and 12° C. In region 2 it is present in surface, sub• surface and deep water. In region 3 the abundance of this form drops sharply to a single occurrence in the sub-surface water. In region 4 the large form is absent. The Small Form of Calanus sp. (Shan, 1962) is entirely ab• sent -from region 1 (Fig. 20). It Is found throughout region 2 but in low densities with the exception of one surface sample from the coast of Oregon (Pacific Station 9) in which the cal• culated concentration was approximately 100 animals per cubic meter. The Small Form is present in region 3 in an abundance similar to region 2. In region 4 it is present in a notably higher density in the upper 100 meters. The figure of 100 animals per cubic meter, as determined for the surface sample at Station Pacific 9, appears anomalous in contrast to the abundance at other levels on the same station and to the abundance at other stations in the immediate area. The phenomenon of encountering localized high concentrations occurred occasionally in Indian Arm, where sampling was more complete particularly when the same station was sampled period• ically over a 24 hour period. During one such sampling period an estimated 3000 animals per cubic meter was taken from a near surface tow, and yet in other sampling periods in the same 24 hour day the total number of animals per cubic meter integrated over the whole water column was much less than this figure. In this study such occurrences were more the exception than the rule and may be attributed to some concentrating effect such as the horizontal convergence of several water currents or possibly a localized upwelling. Yearly Presence and Density Analysis of vertical hauls and horizontal tows over a period of 15 months revealed the presence of both forms in Indian Arm throughout the year and eliminated the possibility that the two forms were seasonal morphological variants. Figure 21 shows the total animals per cubic meter for each month. The greatest fluctuations In abundance correlate with the life cycle. Since only adults and Stage-V copepodites were counted, fluctuations in abundance were expected during periods when younger stages of both forms predominate, but such periods appear to exist for a short time. Fluctuations of smaller magnitude may be due to sampling error, predation, and possibly emigration and Immigra• tion. In addition, the Small Form appears to be more abundant than the large form throughout the year (Shan, 1962). Yearly Cycles and Periods of Breeding Figure 22 shows the fluctuation in abundance of adults and Stage-V copepodites for both forms over a period from October 1966 to April 1968. Figure 23 presents the fluctuation in adults of the two species on a percentage basis emphasizing the different periods of breeding. For any particular month the total number of adults of both species was determined, and then the percentage of that total represented, by the Large Form or the Small Form was calculated. Figure 21. Total animals/ / month (both Forms; Indian Arm only). Figure 22. Yearly cycles both adults and stage-V's. Large Form adults reach a peak ln abundance in February (Fig. 23). Thereafter the abundance of adults drops and, through• out the remainder of the year, the adult population is mainly fe• male. The Stage-V copepodites of the Large Form undergo a fluc• tuation in abundance that is the inverse of that of the adults.. An exception occurred in October 19^7, but this Is believed to be due to net sampling error (Fig. 22). October was the one month in which ship time did not permit a complete vertical haul from near the bottom to the surface; as a result the net only sampled the upper 150 meters, 70 meters short of the-bot• tom, and the majority of the Stage-V population was probably in• completely sampled. It will be seen below that the Stage-rV of the Large Form generally occupies the near bottom water layers especially during mid-day when the sample was taken. Small Form adults reach a peak of abundance in March', April or May, and again around September. The fluctuation in abund• ance of the Stage-V copepodites Is nearly Inverse to that of the adults. The period of sampling covers 19 months so that one complete yearly cycle with parts of the previous and parts of the succeed• ing yearly cycles are shown. The low numbers of adults for both species from October and November to January and February is re• peated and thus the results seem to be consistent. The pattern of increase in adults for both species appears to repeat itself, and the respective times within each species for the onset of this increase are similar in early 1967 and early 1968. Data obtained from the distributional study was used for a spot check of other populations of both forms. The objective was to determine if these populations were in a breeding or non-breeding stage. Assuming that a breeding population!) has a proportionately higher number of adults than Stage-V copepo• dites, the determination of a breeding or non-breeding popula• tion was based upon the ratio: number of adults to number of Stage-V copepodites. The monthly series from Indian Arm was used as a basis for comparison and'is summarized, in Table XIII. The cruise to Alaska in August of 19&5 encountered the Large Form only. The results of the ratios are presented, in Table XIV. Nearly all the stations analyzed have a proportion• ately greater number of Stage-V copepodites than adults. The population of the Large Form in Indian Arm has a similar pro• portion for this time of year. Station Pacific A differs not• ably in this ratio from the others, and it is believed that this is due to incomplete sampling. Other stations in the re• gion of Pacific A show the Stage-V's to be in greater propor• tion. The station depth at Pacific A was approximately 900 meters, but the nets only sampled down to 290 meters. Ninety- nine percent of the adults were found in the upper 12 meters. Since the Stage-V copepodites of this form occur relatively deep and in Indian Arm they are generally found below the maj• ority of the adults, the same situation may have prevailed at Pacific A with the result that the nets failed to sample the total population effectively. Sumner Strait had equal numbers of adults and Stage-Vs. Based on the proportions observed at the other stations of this cruise, it is possible that the pop• ulation at this station was near the end of its breeding season. The results of the adult Stage-V ratios for the two cruises to inlets of British Columbia in June- 1966 and June 1967 are summarized in Table XV. Both forms were found at some of the stations, e.g. ,. Sutil Channel and Johnstone Strait. The north• ern boundary of the Small Form was found during these cruises and the Sutil Channel station was measured twice thus enabling a check on the consistency of the findings from one year to the next. In Sutil Channel the Large Form Stage-V copepodites pre• dominated in both years. This proportion is similar to Indian Arm for the Large Form at this time of the year. For the Small Form the adults predominated or were equal in proportion to the Stage-V's which is a pattern similar to that for Indian Arm at this time of year. Since the time of sampling in Sutil Channel is one month earlier in 1967 than 1966, the ratios might be ex• pected to vary somewhat. The trend of more Stage-V*s and fewer adults in the population of Large Form is similar for both years. Within the population of the Small Form the ratio of adults: Stage-V changes notably in the July I966 and June 1967 samples (Table XV). It is conceivable, therefore, that the change for this form in Sutil Channel is due to this type of population flux rather than sampling error. Further, the trend from June to July is toward fewer adults and more Stage-V's in both Indian Arm and Sutil Channel. THE PROPORTIONS OF ADULTS TO STAGE-V COPEPODITES FOR INDIAN ARM MONTH LARGE FORM SMALL FORM July 1966 1:18 4:1 October 1966 1:70 1:7 November 1966 1:113 1:35 December 1966 1:109 1:125 January 1967 1:5 1:67 February 1967 1:1 .1:36 March 1967 69:1 1:2 April 1967 1:1 1:1 May 1967 1:13 2:1 June 1967 1:14 5:1 July 1967 1:22 1:2 August 1967 1:24 2:1 September 1967 1:18 1:2 October 1967 1:21 1:9 November 1967 1:48 1:50 December 1967 1:20 1:82 January 1968 1:7 1:44 February 1968 3:1 1:21 March 1968 46:1 1:2 April 1968 1:2 17:1 PROPORTION OP LARGE FORM ADULTS : STAGE-V COPEPODITES. CRUISE TO ALASKA - AUGUST 1965 STATION RATIO OF ADULTS Glacier Bay 1:49 Icy Strait 1:7 Pacific A 8:1 Pacific B 1:8 Pacific C 1:12 Lynn Canal 1:6 Pacific F 1:4 Sumner Strait 111 Indian Arm (Aug. 1967) 1:24 PROPORTION OF ADULTS, J STAGE-V COPEPODITES CRUISES TO INLETS OF BRITISH COLUMBIA — JULY 1966, JUNE 1967 RATIO OF STATION FORM ADULTS:STAGE-V Sutil Channel Large 1:8 (1966) Small 1:1 Sutil Channel Large 1:6 (1967) Small 7:1 Queen Charlotte Strait Large 5*1 (1967) JohnstoneStrait Large 4:1 (1967) *Small 3:1 Knight Inlet Large 1:30 (1967) Indian Arm Large 1:18 (July 1966) Small 4:1 Indian Arm Large 1:14 (June 1967) Small 5'1 Indian Arm Large 1:22 (July 1967) Small 1:2 *Based on only 13 specimens — see text. In Johnstone Strait, June 1967, only 13 adult specimens of the Small Form were found whereas nearly 1000 Large Form were encountered in the same sample. Adults of the Large Form pre• dominated, unlike the pattern in Indian Arm for this time of year. Since the Large Form outnumbered the Small Form 76:1, the fact that adults of the latter also predominated at this station is probably insignificant with regard to interactions such as interbreeding and competition for food between adults of both forms. This region is the northern boundary in the range of the Small Form, and the presence of suchllow numbers may indicate that the Johnston^ Strait population is not resi• dent but in fact an immigrant population derived from a resident population further south. The tides in the area are strong, and as a result may have a pronounced effect in transporting planktonic organisms some distance from their actual breeding populations. The strong turbulent tidal action in the narrow passages is an obvious mechanism for mixing the northern waters of Queen Charlotte Strait and Queen Charlotte Sound with the southern waters of upper Strait of Georgia. This action would con• ceivably contribute to the dilution of environmental factors essential to the survival and or reproduction of the Small Form. The lack of Small Form populations north of Johnstone Strait indicates these waters are different in character from the more southerly waters. The conditions which prohibit sur• vival and reproduction of the Small Form in Queen Charlotte Strait are present to a degree in the Johnstone Strait region and contribute to the dilution of the favorable conditions in the waters of the Strait of Georgia. As a result, the popula• tions of the Small Form appear diluted in the sense that popu• lation densities drop drastically in Johnstons Strait. The Large Form was the only form of the two encountered in Queen Charlotte Strait in June 1967. The adults of this popu• lation were greater in proportion to the Stage-V1s, as they were in Johnstone Strait, but dissimilar to the proportion in Indian Arm. In neighboring Knight inlet, the Large Form, was the only one noted, but in this region the Stage-V copepodites made up the greatest proportion of the population at this time, as they do in Indian Arm in June. The ratios for the cruise along the west coast of the U.S.A. in February 1966 are summarized in Table XVI. During this cruise the southern boundary of the Large Form was estab• lished. No data ajre available for Indian Arm in February 1966, but since the Indian Arm cycle appears to repeat itself, it is probably that the ratios determined for February 196? and Feb• ruary 1968 are reasonable estimates of the pattern prevailing in February 1966. From Station Pacific 2, off the northwest coast of the state of Washington, to Station Pacific 34, off Cape Mendocino, California, adults of the Large Form tended to predominate in• creasingly toward, the southern boundary of its range. Adults of this form predominate or are equal In proportion to stage-V copepodites In Indian Arm at this time of year. PROPORTION OF ADULTS : STAGE-V COPEPODITES EASTERN PACIFIC CRUISE OF FEBRUARY 1966 RATIO OP STATION FORM ADULTS : STAGE-V Pacific 2 Large 1:2 Small 1:20 Pacific 4 Large 4:1 Small 1:2 Pacific 7 Large 22:1 Pacific 34 Large 71:1 Small 2:1 Pacific 33 Small 1:4 Pacific 23 Small 1:2 Pacific 29 Small Pacific 30 Small 3*1 Indian Arm Large 1:1 (February 1967) Small 1:36 Indian Arm Large 3:1 (February 1968) Small 1:21 For the same range of stations, Stage-V's of the Small Form predominated in the populations sampled; this proportion is similar to Indian Arm in February. Off Cape Mendocino, however, the Small Form adults predominated, but they outnum• bered the Large Form 89:1. As in Johnstone Strait, where the Small Form was outnumbered by the Large, there is probajbly little significant interaction between adults of both forms when one greatly outnumbers the other. South of Cape Mendocino, Small Form Stage-V's predominated in the populations off Central California. The reverse is true for the populations off southern California, where the adults predominated, in stations from Santa Barbara Channel to San Diego. Comparing these results to those for Indian Arm, it was noted that in regions where both forms occur together, the respective ratios of adults:Stage-V's were similar to those for Indian Arm. South of the overlap, the ratio of adults: Stage-V's for the Small Form was dissimilar to the ratio found for Indian Arm. As for the Large Form, however, the proportionate number of adults increased torward the southern part of the range. The data indicate;, that the onset of the breeding period starts earlier at the southern end of the range for both forms. In regions of overlap, the life cycles in general appear to be similar to those for the Indian Arm populations, but outside the overlap the breeding periods may differ. Analysls of Moulting Rates; Stage-V to Adult The moulting rates in several temperatures and in abundant food are presented in Figure 24. In the controls (no food) the time to 50 percent moulting was consistently greater than 20 days, and often over the experimental period cfr30 days, less than 50 percent of the'animals moulted. Experiments in at least two different temperatures were carried out during each experimental period so that a second control was available to check if the reaction to temperature for that period was real. The number of days (Fig. 24) in which it took 50 percent of the test animals to.moult from the fifth copepodite stage to the adult stage represents an average of three replicate ex• periments at each temperature for each form. The variation around each average was not more than 3 days. For both forms a notable change in rate occurs between 5 and 10° C. A slower rate of moulting at 10 and 15° C for the Large Form compared to the Small Form is indicated by the slope of the respective graphs (Fig. 24), but at 5° 0, the Small Form appears to be somewhat slower compared to the rate in 10 and 15° C water. Between 5 and 10° C, the Small Form exhibits a more marked reaction, the period to 50 percent moulting being more than twice as long at the Iowerrtemperature. For the Large Form, over the same temperature range, this period is less. Figure 24. Moulting rate VB temperature. Each point repre sents an average time to $0% mounted gf 3 reglicate ex periments at each temperature (5 , 10 , & 15 C). 24 animals were involved in each replicate. Large Form Small Form A"'t Station 9 in Indian Arm, measurements of temperature and salinity were made immediately prior to a series of strati• fied plankton tows. The purpose was to determine any possible division of the water column into distinct regions with respect to these two conservative oceanographic factors. Any regions thus defined might then be correlated to the vertical distribu• tion of the two local forms of toothed Calanus sp. The physical data was analyzed apart from the plankton data to avoid any possible bias. Temperature and salinity profiles are represented in groups to emphasize seasonal effects. The months are grouped according to the seasons demarcated by Gilmartin (1962) which are based primarily on the annual fluctuations in salinity. These seasons are as follows i 1) January to March' — late winter salinity minimum; 2) April to June — spring salinity maximum; 3) July to September — mid-summer salinity minimum; 4) October to December — early winter salinity maximum. Three main regions are evident upon inspection of the profiles (Figs. 25 - 29). These regions are the surface layer, the intermediate layer, and the bottom or deep layer. The surface layer generally extends from the surface to approxim• ately 10 meters. For convenience it is definedaas the region where salinity changes more than one part per thousand per 10 meters, and temperature changes more than 0.8 degrees centi- grade per 10 meters. The deep layer generally starts around 125 meters and extends to the bottoms it is characterized by a change in salinity of 0.1 parts per thousand or less per 25 meters and a change in temperature of 0.1 degree centigrade or less per 25 meters. The intermediate layer is defined as that region between the surface layer and the deep layer. The sur• face layer is subject to large fluctuations in temperature and salinity and is influenced to a large degree by the seasonal changes in temperature and freshwater runoff into the inlet. The intermediate layer exhibits a yearly variation with regard to both factors but the degree of variation is smaller relative to the surface layer. The deep layer is a relatively stable region which is influenced more by instrusions of denser water from the outside (Gilmartin, 1962). The three regions of the water column defined in this way, may represent three distinct water bodies in the sense of Bary (I963). Their origin may be distinct and their qual• ity with respect to the survival and reproduction of both forms of Calanus sp. may differ to the extent that essentially three habitats are present. Under these circumstances morpho• logically similar forms or species with nearly identical eco• logical niches could conceivably coexist in a geographical sense, i.e., both are found in a particular oceanographic re• gion. This would be an allopatric relationship with respect to the water column. Figure 25 represents the temperature and salinity condi• tions for February and March 196?. The three regions are S°/oo 21 22 23 24 25 26 27 o- i 25- 50- 75- 100- &125-I x—x Apr. 1967 Q (5.44 %oSfc.) 150-1 o—o May 1967 (15.22 °/ooSfc.) 175j . . Jun. 1967 (5.92 %oSfc.) Figure 27. T & S profiles for Indian Arm, Jul., Aug., Sep., 1967. Figure 28. T & S profiles for Indian Arm Oc, Nov., Dec, 1967. S °/oo 21 22 23 24 25 26 27 0-1 ' 1 1 ' L. 25J 5 OH 754 100H & 125-1 x—x Jan. 1 968 (9.57 %o sfc.) 150J o—o Feb. 1968 (14.18 %o sfc.) M5A - Mar. 1968 (17.08 °/oo sfc.) 200- evident. A notable temperature change between the two months occurred in the intermediate layer illustrating the relatively short term fluctuations that can occur in this layer. .. The temperature and salinity profiles for the remaining months are represented in Figures 26 - 29. The development of a large but gradual halocline and thermocline occurred from April to June 196?. In April 1967 there was little ap• parent change in both temperature and salinity between 10 meters and 200 meters and any indication of an intermediate layer was nearly absent. In May 1967, a halocline developed and stratification was evident with respect to temperature. By June the thermocline and halocline appeared as a gradual change with regard to both properties, resulting in a T-S diagram for this month that appears as a straight line, down to a depth of 100 meters. There was little appearance of stratification in the intermediate layer, and in this month, the deep layer warmed slightly. In the subsequent months the temperature of this deep layer varied little from the June values. From July to September 196? stratification was evident in the intermediate layer, to a depth of 75 meters. Through these months the halocline became progressively steeper, tend• ing toward the salinity profile of February and March 1967. From October to December 1967 the halocline was less strongly developed, and the intermediate layer became progress• ively cooler indicating that the summer stratification was waning. Prom January to March 1968, the pattern was similar to February and March of 1967. The halocline was evident but not as pronounced, as earlier. The temperature c*Kangp:iin the inter• mediate layer was also relatively small. The upper level of the deep layer was displaced upward to 100 meters in June 1967 and from January to March 1968. The boundaries must not be considered as precise, however, asfc a zone of mixing of 5 to 10 meters or possibly more may exist between the layers. The temperature and salinity profiles from April to June 1967 are difficult to explain on the basis of sampling from one station. The nearly uniform conditions of both factors in April and the subsequent pattern in May and June suggest a possible intrusion of water from the out• side which gradually mixed with the resident water. The inlet is known to turn over periodically (Gllmartin, 1962) but any explanation over the sampling period described can only be built on speculation from knowledge about the previous history of the inlet. Mid-Day Vertical Distributions The mid-day distributions determined from monthly samples from February 1967 to March 1968 at station number 9 in Indian Arm are represented in Figure 30. Both forms are segregated into males, females, and Stage-V copepodites. The boundaries of the three water layers, as determined from the temperature and salinity conditions on the station for each month, are represented by stippling. Since a degree of mixing probably occurs at the interface between each layer, the boundaries are arbitrarily represented as regions at least 5 meters thick. The pertinent observations are as follows: 1. All the stages represented, with the exception of Large Form males and Stage-V copepodites, showed a reaction to the conditions present in June 1967. The abundance of each population was notably higher for this one month. 2. Large Form Stage-V's were notably higher in the water column in April 1967. During this month the tempera• ture and salinity conitions over the water column between 10 meters and 200 meters were nearly uniform. Over the sampling period, only a slight vertical displacement was present in June 1967 for this stage. The majority of the ,stage-V population was present in the deep layer. 3. The adults and Stage-V copepodites of both forms ap• peared to react to the summer stratification. Gen• erally, they all occurred at lower levels between July and September 1967. 4. Large Form males are present for a comparatively short time, being present only in 7 of the total 14 months samples. Over most of the period the major• ity of the population occurred in the deep water layer? at other times the majority occurred near the boundary of the deep layer, reacting similarly to the Stage-V copepodites of this form in April 196?. 5. Large Form females generally appear higher in the water column than the males and Stage-V's. Small Form females are not distributed this way. 6. The majority of the population of Small Form adults and Stage-V's was found in the intermediate layer throughout the year. ?. Small Form males were absent for only 3 of the 14- months sampled, and thus were present for a longer period than the males of the Large Form. 8. The mid-day distributions of Large Form males show that the majority is always below the majority of the population of Small Form females. 9. Large Form females significantly overlapped the population of Small Form males over much of.the sampling period. From July to October, however, the majority of female Large Form were separate and below the majority of Small Form males. 10. The penetration of the upper boundary in June was not as pronounced for Large Form females. In con• trast more than 75% of all the Small Form stages studied were present in this upper layer in June. 11. Over the sampling period Large Form females were generally in the lower half of the intermediate layer, and 50% of the population was generally deeper than adults of the Small Form. 24-Hour Vertical Distributions Twenty-four hour stations taken during selected months over the same period as the noon hour samples provide a more detailed picture of the reaction of the animals to the pre• vailing water bodies, while indicating the relative length of time any particular stage of one form may overlap with that of the other. During the early part of the year the de• gree of overlap between males and females of the two forms be• comes important since at this, time there is a slight overlap in the breeding periods. If inter-breeding were to occur it would be during this period. As in the mid-day distributions each form is broken down into males, females, and. Stage-V copepodites, and the distribu• tion of each considered separately. In cases where one stage was present in concentrations of less than 0.5 animals/cubic meter or entirely absent during one or more of the sampling times for the month considered, the stage in question was not plotted. Such low numbers cannot be accurately represented, with regard to vertical distribution and association with • Water layers. Also, low numbers of either sex were considered to be insignificant with regard to interbreeding. The 24 hour vertical distributions are represented in Figures 31-34. The boundaries of the water layers are repre- sented. as they were in Figure 30i for the mid-day distribu• tions. The dotted quartile lines represent the distribution of females with attached spermatophores. The general points to be noted from these distributions are: 1. Both forms appear to attain their deepest level dur• ing the daylight hours when vertical migration is evident. *" 2. With the exception of May 1967. all stages of Small Form appear to Migrate vertically over a 24 hour period. Large Form females migrate whereas, males and Stage-Vs of this form appear not to do so. 3. The females of both forms migrate vertically more consistently than the males and Stage-Vs. 4. For both forms, the peak or shallowest point attained during a vertical migration is generally around 2400 hours. Exceptions occur, however (e.g., August 1967, when Large Form females attained their shallowest point at 1800). In September 19&7 and January 1968 the peak of vertical migration was reached at 1800 hours for migrating stages of both forms. In March 1968 Large Form females reached a peak at 1800 hours and a similar trend was noted for Small Form females. With regard, to Large Form adults and stage-V copepodites the pertinent observations are: 1. Large Form females are generally higher than the males and Stage-V's of this form over a 24 hour period. 2. For most of a 24 hour period, the majority of the females are generally in the lower portion of the intermediate or in the upper portion of the deep layer. 3. Obvious overlaps occur between Large Form females and the population of Small Form adults and stage-V's. In February and March 1968, the majorty of the Large Form female population was below the majority of the Small Form male population during most of the sampl• ing period. 4. Large Form females with attached spermatophores were generally below the majority of the females. In January and February 1968 Large Form females with attached spermatophores were below the majority of Small Form males; the vertical distribution over• lapping that of the Large Form males. 5. During some months there was a tendency for 50- 100- iininillwtfflffiTi^^ IININIIIII^ NNJpMlffiMllll^ 150- 200- Large Form males Large Form females Large Form stage-V Small Form stage-V May 1967 18 24 06 12 18 24 06 12 18 24 06 12 18 24 06 12 18 24 06 12 J I L -I I L_ 100- 150 Large Form females Large Form stage-V Small Form males Small Form females Small Form stage-V Time (hours) July 1967 18 24 06 12 18 24 06 12 18 24 06 12 18 24 06 12 18 24 06 12 i i i i I i_ i i i_ i i 1 100 150- 200 Large Form females Large Form stage-V Small Form males Small Form females Small Form stage-V Aug 1967 12 18 24 06 12 12 18 24 06 12 12 18 24 06 12 12 18 24 06 12 12 18 24 06 12 j i i i -| i i i i i i i i i I i i ' ' 50- 100- 150 Large Form females Large Form stage-V Small Form males Small Form females Small Form stage-V Figure 33. 24 hour vert, distributions Sep. 67 and Jan. 68. (UJ) LudaQ exceptlon was in January 1968, when the lower 25$ stayed deep in the Intermediate layer following a pattern similar to Small Form Stage-V copepodites. Available Food When it became evident from the samples that portions of the Large Form population were remaining in the deep layer for extensive periods of time, the question arose as to how the deep living animals maintained themselves. An available food source would be necessary to support them in some periods at least. In order to answer this question two chlorophyll anal• yses were run, one in February and one in March 1968. Feb• ruary was a month of low primary productivity at the surface. In contrast to this month, March 1968 was a period of rela• tively high primary productivity. Visibility from the surface was less than a meter, and the phytoplankton bloom consisted primarily of the diatom Thailassloslra sp. In March, fine mesh (#20) Clarke-Bumpus nets were used to sample the phytoplankton at the same standard depths as the zooplankton samples. The guts of specimens of"both"forms were analyzed to determine the type of food material'ingested. 'The results of the chlorophyll analyses are presented in Figures 35 arid 36. Since chlorophyll A occurs in all phyto• plankton (Chapman, 1962), it was considered sufficient to analyze for this pigment only in order to indicate the rela• tive quantity of phytoplankton available. In February 1968 Figure 35. Chlorophyll A distribution for Feb. & Mar., I968, 100-3 Indian Arm (stn. 9) Feb. 1968 10-d ro E 100-3 Indian Arm (stn. 9) Mar 1968 oa o u 10-d 50 , 100 150 Depth (m) 200 there was a definite peak of chlorophyll A at the surface and a second obvious peak at 150 meters. Below 150 meters there was a relatively high concentration of chlorophyll A. In March 1968, the presence of a phytoplankton bloom at the surface was indicated by the high concentration of chloro• phyll A found there. Compared to the previous month there was nearly a tenfold increase in chlorophyll A at the sur• face. Other peaks occurred at 50. 100, and 200 meters. The indications are that viable phytoplankton cells do occur in the deep layer. Analysis of the Clarke-Bumpus tows revealed the presence of viable cells of Thallassiosira sp. and Skeletonema sp. in the deep layer and in the upper regions of the water column. Analyses of the guts of animals of both forms revealed the presence of Thallassiorsira sp. Breeding Experiments Breeding experiments following the scheme described in the materials and methods section, page 33» were conducted on four different occasions. The numbers of each sex of each form in• volved in the crosses are shown in Table XVII. Interformal fer• tilization never occurred. Intraformal fertilization was con• firmed in one Large Form female in the September I967 experiment. In the November I967 experiment, one Small Form female was fer• tilized. COMPOSITION OF BREEDING EXPERIMENTS m _ MONTH EXPERIMENT CONDUCTED Type of Cross Aug. 1967 Sep. 1967 Nov* 1967 Jan. 1968 Large Males 7 .2 3 4 x • Large Females 27 20 3 21 Large Males 8 2 2 6 X Small Females 19 18 2 12 Large Females 27 20 3 23 X Small Males 3 2 3 6 Small Males 3 2 8 1 X Small Females 18 17 8 1 DISCUSSION The Large and Small forms of Calanus noted by Shan (1962) differ not only In external morphology, but in their distribu• tion along the west coast of North America, and in their gen• eral ecological relationships. Summary of the Differences The morphological differences between the two forms are similar to differences found, between recognized species of toothed Calanus from other regions (Marshall and. Orr, 1953; Brodsky, 1950? Jaschnov, 1955; Marshall, personal communica• tion). The obvious overlap in the ranges of the Large and Small Form is similar to that found for Calanus finmarchicus and C. helgolandlcus of the eastern North Atlantic and North Sea (Marshall and Orr, 1953). The most obvious morphological differences between the two forms are the overall length as reflected by the prosome length measurements, and the head shapes. Differences in the width to length proportions of the urosome segments are ap• parent from the analysis of the measurements, but these are hard to discern by eye. The genital and following two distal segments are different, in proportion, between the females; in the males the third and fourth segments from the proximal end of the urosome differ in length to width proportion. In the fifth swimming legs, the results of the ratio formed by dividing the length of the right exopod by the length.of the left exopod express the varying degree of asymmetry between the males of the local forms. The fifth legs of females are symmetrical although a difference in the proportionate lengths of the third or terminal segments was evident after analysis. A character common to the males and females of both forms is the spinose process located on the distal surface of the bsipodites of the fifth legs. It is notably longer In the Small Form and Is particularly useful in Identification when the exopods have been broken off the males of both forms. On these grounds, there is a possibility that the toothed Calanus from British Columbia are not identical from a taxonomic point of view. Comparison to Other Species Since the toothed Calanus of the Northeastern Pacific have frequently been synonymized with C. finmarchicus and. C. helgolandicus of the North Atlantic, it is important to dis• tinguish the animals from these two regions. The local toothed Calanus can be distinguished by the characteristics presented in the foregoing, whereas the distinctions from the North At• lantic species are based on descriptions and comments by Brodsky (1950 and 1965), Shan (1962), Jaschnov (1955)» Marshall and Orr (1950), and Sars (1903). On the basis of the protuberant shape of the anterior region of the cephalothorax, the curved row of teeth on each coxopodlte of the fifth swimming legs, and the greater degree of asymmetry in the fifth swimming legs of the males, the Small Form noted by Shan (1962) may be distinguished from Calanus flnmarohlous (Gunnerus). The Small Form may be dis• tinguished from C. helgolandious (Claus) by the shape of the anterior region of the cephalothorax and by the relative lengths of the segments of the left exopod of the fifth swim• ming legs of males. The Large Form noted by Shan (1962) may be distinguished from C. finmarchicus (Gunnerus) by the shape of the. row of teeth on the fifth swimming legs of both sexes and. the degree of asymmetry of this appendage in the males. The Large Form is easily distinguished from C. helgolandlcus (Claus) by the shape of the anterior region of the cephalothorax and the degree of asymmetry in the fifth swimming legs of the males. Of the descriptions for various species and, sub-species of toothed Calanus, those of C. pacificus callfornicus Brodsky (1965) and C. glaclalis Jaschnov (1955) best apply to the toothed Calanus in the waters of British Columbia. The diag• nosis is based on the written descriptions, drawings, and re• corded distributions presented, by the respective authors. The complete descriptions of the local forms given in the appendix may be useful for reference. In the paper describing the sub-species Calanus pacificus callfornicus for the first time, Brodsky (1965) compares two other sub-species, C. p. oceanlcus and C. p. pacificus. There is little doubt from the drawings alone/ that the local Small toothed Calanus is distinct from the latter two sub-species, particularly on the basis of the structure of the fifth, swim• ming legs of the males. Female Calanus pacificus californicus are distinguished by the protuberant anterior region of the cephalothorax, the relatively short genital segment which is strongly curved along the dorsal surface, the number of teeth of the fifth leg (averaging about Zh and ranging from 20 to 29) and the indistinct boundary between the eighth and ninth segments on the antennules (Brodsky, 1965). In the local Small Form (Shan, 1962), the shape of the anterior region of the cephalo• thorax Is identical to the drawings given in Brodsky's des• cription. Compared to the other sub-species described by Brodsky (1965)» C. p. californicus appears to have a longer, more pronounced "forehead". The genital segment is notice• ably curved in the local Small Form, but a direct comparison is difficult since a drawing of the genital segment in lateral view is lacking in Brodsky1s (1965) original description. The number of teeth of the fifth swimming legs given by Brodsky agrees with that of the local Small Form. The females also have the indistinct articulation between the eighth and ninth segments on the antennules, but the same is also true of the local Large Form. Male Calanus pacificus californicus are primarily dis• tinguished by the length of the left endopod of the fifth swimmlng legs (Brodsky, 1965). Unlike the other sub-species discussed, this endopod is longer and extends beyond the first segment of the left exopod, terminating within the lower third of the second segment of the left exopod. The right exopod does not extend beyond the articulation between the second and third segments of the left exopod but may extend to the middle or distal third of the second segment of the left exopod. The males of the local Small Form are identical in these respects. The size range of Calanus pacificus callfornicus males andrfemalesy as reported by Brodsky (1965)» agrees with that found for the Small Forms in this study. The geographic range of Calanus pacificus callfornicus includes the west coast of the United States (Brodsky, 1965). Animals collected for this study from the same region not only fit the morphological description for C. p. callfornicus given by Brodsky (1965) but were also morphologically identical to the Small Form described by Shan (1962) from Indian Arm. On this basis, the Small Form is believed to be C. p. callfornicus (Brodsky). The females of Calanus glaclalis are distinguished by an evenly rounded anterior region of the cephalothorax and a compact,, relatively broad body. The antennules reach to the end of the caudal furcae, or the last one or two segments extend beyond. The fifth swimming legs have a distinctly curved row of teeth near the middle ofthe coxopodite although the curve is somewhat displaced toward the posterior surface of the segment (Jaschnov, 1955). This last feature may vary with temperature (Mathews, 1966). The teeth are relatively large and blunt and vary in number from 26 to 43 (Jaschnov, 1955)• The outer and inner edges of the first segment of the exopods of the fifth swimming legs are nearly parallel as op• posed to the triangular shape in C. pacificus. The males of Calanus glacialis are distinguished primar• ily by the fifth swimming legs. The right exopod is shorter than the left, extending to or slightly beyond the articula• tion between the second and third segments of the left exopod. The left endopod does not reach beyond the middle of the second segment of the left exopod. Within the left exopod of the fifth legs, the first and second segments are nearly equal in length, but the third segment is approximately 2/3 the length of the second segment (Jaschnov, 1955). The local Large Form differs from the original descrip• tion of Calanus glacialis Jaschnov (1955) in being somewhat shorter and. having fewer teeth on the coxopodite of the fifth leg. Most specimens of C. glacialis, from Jaschnov*s (1955) work, have 30-35 teeth per leg, whereas the majority of speci• mens of the local Large Form had 22-27 teeth per leg. Shan (1962) reports tooth counts which agree with those found in this study and also mentions the inability to differentiate the two local forms on the basis of number of teeth. The number of specimens counted in this study was 30, while the number counted by Shan (1962) was 82. The number of specimens used by Jaschnov (1955) is not mentioned, and his vaies are expressed by percentages, but if a low number of animals were used then his distributions could be incomplete. A higher number of counts of animals from the Arctic and Sea of Japan, where the species was originally described (Jaschnov, 1955), might result in distributions which would be more like those of the local populations. A check of the number of teeth in the Large Form from various points along the range in this study, failed to show any significant variation with latitude. The Large Form of Shan (1962) appears to Calanus glacialis although, unlike C. pacificus callfornicus, the length varies significantly with latitude (Fig. 7). This could explain Shan's (1962) notation that, except for their smaller size, the local Large Form appeared morphologically similar to C. glaclalls as described by Jaschnov (1955). Grainger (196l) reports a similar change in mean length for C. glaclalls In samples taken along the northeast coast of Canada from the Arctic Ocean to the Gulf of Maine. Grainger's samples range much further north than those from this study, but he reports a maximum length in individuals somewhat south of the northern extent of the range of the species. Animals in the Arctic Ocean were shorter than those in the area of Foxe Basin, Hud• son Strait, and north Hudson Bay. The mean length of speci• mens from Foxe Basin was 3.98 mm while the mean length of those from the Gulf of Maine was 2,80 mm. Since change in length of the prosome appears to be much less than in the urosome segments in preserved animals, pro- some lengths only were used in this study to reflect the overall size of each specimen. In order to make an approxim• ate comparison of prosome length data with total body length data the following relationships were derived: For C. glaci• alis the prosome length of females is 0.74 of the total length. For males and Stage-V copepodites the prosome length is 0.73 and 0.75 of the total body length', respectively. In this study a change in mean prosome length of 0.6 mm for females and 0.5 mm for males and Stage-V copepodites was recorded over the portion of the range sampled along the North American west coast. Jaschnov (1955) reports C. glacialis from the Sea of Japan and the Sea of Okhotsk as well as a number of regions along the Arctic coast ofc-the U.S.S.R. Jaschnov's length measurements are greater than those from Grainger's (1961) study, with a range of lengths, for female specimens from the Sea of Japan, of 4.3 - 5.0 mm (equivalent prosome lengths are 3.2 and 3*7 mm respectively): for the Sea of Okhotsk, 4.5 - 5«2 mm (equivalent prosome lengths are 3.3 and 3.8 mm respectively). Males and Stage-V copepodites are somewhat smaller. The species has been reported from the Bering Sea and length measurements for females are similar to those reported from the Sea of Okhotsk (Jaschnov, 1958). In the central North Pacific, female G. glacialis collected from 31° 54' N, 154° 49' W, were reported to have a length range of 3*45 - 3.84 mm (equivalent prosome lengths are 2.56 and 2.84 mm respectively) (Park, 1968). Size variations on the order of 1 mm have been reported for the toothed Calanus sp. in the Queen Charlotte area (Cam• eron, 1957)• It is assumed that these Calanus are C. glacialls Jaschnov since no other species were noted from that region in this survey, and no others have been reported In the litera• ture other than the synonomy with C. finmarchicus. Cameron (1957) suggested that the size variation may be due to speci• mens from different broods. This statement is based on the findings of Digby (1950), who reports that species producing more than one brood a season frequently show a size variation in adults from different broods, and such a variation was found to be true of C. finmarchicus in the vicinity of the British Isles. C. finmarchicus reaches maturity in approxim• ately 28 days in the waters around Britain, but this period is reported to be longer in more northern waters (Digby, 1950). Cameron (1957) states that her collections were made in a period of 21 days and therefore it was not likely.that the 4dults from two broods were capturepl. • Further, she notes that size variation in adults of local breeding populations were minimal, but she did note different size ranges between breeding populations. Since the size of C. glaclalls appears to increase in colder northern waters (Jaschnov, 1958; Graing• er, 1961), it may also be true that the size may increase in populations breeding in the colder fpords of the British Col• umbia and southeast Alaskan Coasts. In regions around the Queen Charlotte Islands that are influenced by the relatively warmer waters of the Pacific Ocean, the breeding populations of G. glacialis may appear smaller. On the basis of these findings It is evident that a size variation with latitude similar in magnitude to that described by Grainger (1961) occurs in the waters of the northeast Pacif• ic Ocean. As a result, the C. glacialis in Indian Arm are smaller than the specimens described by Jaschnov (1955) from more northern waters. Biochemical differences were also noted for the local species. Using the method of starch gel electrophoresis a difference of 2 out of 7 protein zones was demonstrated (Beh- rens, 1968). This result helps substantiate the fact that good differences do exist, but any conclusion as to the taxo• nomic relationship on a biochemical basis must await further study. Distribution Calanus pacificus californicus has been reported from 23° N to 48° N along the west coast of the United States and Mexico (Brodsky, 1965). The occurance of C. glacialis in the northeastern Pacific has been proposed by Jaschnov (1957) and Brodsky (1965)» and the C. finmarchicus type described by Campbell (1930) along the west coast of Canada is believed by Jaschnov to be C. glacialis. This Is based on Campbell's de• scriptions of the fifth legs of the males (Jaschnov, 1957). A sample from Unimak Pass in the Aleutians sorted in this study- confirmed the presence of C. glaclalis. The southern extent of C. glaclalis. along the west coast of North America, has been surmised to be slightly south of Cape Flattery, Washing• ton (Brodsky, 1965). Neither of the two authors verify the occurrence of either species in the inldnd waters of southern British Columbia, and the amount of overlap indicated for the two species is believed to be slight, covering about one de• gree of latitude between k?° and 48° N. The faunistlc boundaries established In this study ex• tend those presented above, particularly in the case of C. glaclalls. Brodsky (1965) indicates the absence of C. p. callfornicus from two stations slightly south of Cape Cook on the west coast of Vancouver Island. Since this species Is present in the mouth of Juan de Fuca Strait, the northern boundary along the outer coast probably occurs slightly north of this point. In addition, C. p. callfornicus was not pres• ent in samples taken from Pacific station 2 located about 60 miles seaward of Cape Flattery, although Brodsky (1965) indi• cates its seaward occurrence farther south off the coast of California to be on the order of several hundred miles. The boundaries are subject to variability from several sources. They may fluctuate with season, currents, tides, and movements of water masses. Tides may be of particular concern in the inland waterway of southern British Columbia. Any one or a combination of hydrographic properties such as temperature and salinity may also be responsible for varia• tion in these faunal boundaries, especially if the animals are associated with particular water masses or water bodies (Bary, 1964). In the Northeastern Pacific, the respective faunal boundaries for toothed Calanus spp. may reflect the water mass boundaries 6f:..'theotwO'4waterr,masses Indicated on Figures 19 and 20. As the limits of these water masses shift with time, so would the general distribution of toothed Calanus spp. be expected to shift. Since the two species cannot be easily distinguished in stages younger than the Stage-V copepodite, the stage of the life cycle predominating in a population of one species in a given area becomes important. If such an area, sampled when the majority of the population of one species were in a stage younger than Stage-V copepodite, revealed no adults or Stage- V*s in the samples, then conceivably a false conclusion could be drawn about the exact distribution of that species. For all these reasons, the boundaries found from the samples in this study can only be considered as approximate. Distributional Ecology In terms of density of Stage-V copepodites and adults of Calanus glacialis and C. pacificus californicus there appears to be a difference in the associations with the water bodies illustrated in Figures 19 and 20. C. glacialis has greater population densities in the cooler, more dilute northern waters whereas C. p. callfornicus occurs In greater numbers in the warmer, more saline southern waters. Interpret&ion of these hydrographic properties and faunal distributions along the west coast of North America requires a general knowledge of the California Current System. The main concern in this study is that portion of the system between latitudes 33° and 58° N. Of particular concern is the cause of the marked, change in properties around Cape Mendocino, and the influence of the system in general on the distribution of both species. The southward, relatively slow flowing branch of the Aleutian or Sub-Arctic current is known as the California Current and normally occurs between latitudes 48° and 23° N (Sverdrup, 1943). A second northward flowing branch of sub- Arctic water forms part of the Alaska Gyral (Ibid). The water of the California Current is primarily sub- Arctic In origin, but as the system moves toward the south the sub-Arctic water becomes mixed horizontally with Central North Pacific water and both vertically and horizontally with Equatorial Pacific water (Sverdrup, 19-+3; Reid, 1958). In regions of upwelllng in the current system, water from the lower part of the sub-Arctic water mass mixes with a 'transi• tional' form of Equatorial Pacific water flowing north below 200 meters and is carried to the surface (Reid, 1958). Sub- Arctic water is characterized by low temperatures and low salinities. The Equatorial Pacific water may be detected by its warmer temperatures and higher salinities. A counter current is associated with the California Cur• rent system. It Is present over the year below 200 meters oc• curring inshore of the southward, flowing Sub-Arctic water and represents a northward flow of Equatorial Pacific water. Dur• ing parts of the year, when winds from the north and,northwest are relatively weak, i.e., generally from November to January, this counter current appears at the surface and is known as the Davidson Current (Reid, 1958). Drift bottle experiments have shown that this surface counter current flows at an esti• mated rate of 0.5 knots (Reid, i960), and it may extend as far north as Vancouver Island (Sverdrup, 1943; Reid,.1958, I960). Other intermittant features of the system are the seas• onal upwelling, occurring in spring and summer when winds from the north are strongest, and. the localized eddy systems which 'Occur in the surface water (Reid, 1958, I960). The temperature and salinity data presented in this study-for the stations along the outer coast reflect, the char• acteristics of at least two of the water masses involved in the California Current system. Since the waters north of Cape Mendocino to southeastern Alaska are relatively cool and low in salinity, it is probable that the water is primarily Sub-Arctic. The stations off southeastern Alaska and northern British Columbia may be distinguished, from the stations between Cape Flattery and. Cape Mendocino mainly on the basis of sal• inity in the upper layers and of temperature in the deeper layers. The northernmost series of stations are'nearshore and the water represented on the T-S diagram may be Sub- Arctic water of the Alaskan Gyral which has become mixed to some extent with the waters of the Inside Passage. The water sampled along the coasts of Washington, Oregon, and northern California is probably sub-arctic for the most part since the California Current is broad in cross-section and. the sta• tions in this study were generally near the coast, away from the mixing effects with the warmer, more saline'Central North Pacific water. The presence of C. glaclalis in-these coastal waters may be an indication of their sub-Arctic origin. South of Cape Mendocino the temperature and salinity measurements are markedly different from the more northern stations. Since the stations were within the area where the Davidson Current Is known to exist, the warmer, more, saline water encountered, south of Cape Mendocino probably represents water of this northward flowing counter current. The inshore stations north of the cape reflect the characteristics of sub-Arctic water. The water around the cape appears transi• tional between the two main water masses and. is, probably a zone of mixing. During the time of the year when the cruise was taken (February) the extent and strength of the Davidson Current was probably past its seasonal peak andits northward extent less than has been recorded previously. ' Calanus glaclalis appeared in greatest abundance in sub- Arctic water. As the water mass became mixed around Cape Mendocino, the species dropped in abundance and disappeared altogether in the water of the Davidson Current. The presence of this species in the Bering Strait, Sea of Okhotsk, and Sea of Japan has been confirmed by Jaschnov (1957). In this study it was noted In a sample from Unimak Pass in the Aleu• tians.. Part of the water forming the sub-Arctic current is be• lieved to come from an anti-clockwise gyre in the Bering Sea, and contributes to the formation of the sub-Arctic water through the Oyashio Current (Sverdrup, 1943). The sub-Arctic water is believed to be formed by mixing of the Oyashio and Kuroshio waters. The eastward flowing and. eventual branching to a northward.andsouthward flow, of the sub-Arctic Current provides a means of transport by which C. glacialis could be carried from the Arctic into the North Pacific and thence to the west coast of North America. - If samples in this study were taken in sub-Arctic water, i.e., further offshore, at the southern part of the distribu• tion of C. glacialisf then the southern boundary of distribu• tion might possibly be extended. As was the case in this study the Davidson Current was encountered and the species lost. The high numbers found in sub-Arctic water, the trace found in the mixed water around. Cape Mendoclrio and the ab• sence in the Davidson Current indicate that C. glacialis lives in cool, dilute sub-Arctic water. As the sub-Arctic water becomes mixed with the other water masses a degree of change occurs beyond which the species cannot tolerate. In other re• gions, e.g., the North Atlantic, this species is generally found in cold relatively dilute water (Jaschnov, 1961). Since mixing of sub-Arctic water occurs inshore, with water of Equatorial origin, and. seaward, with water of Central North Pacific origin, the southern boundary of C. glaclalis may ac• tually be wedge shaped as mortality of the animals increases at the eastern and western boundaries of the sub-Arctic water. The effect would be a core of relatively unmixed sub-Arctic water penetrating to the south with a concurrent core of C. glaclalis present until conditions are met which the animals cannot tolerate. C. pacificus callfornicus was present in greatest abund• ance in the relatively warm, saline water of the Davidson Current, but contrary to C. glacialls Its density dropped off sharply in the sub-Arctic water. Abundance of C. p. callf• ornicus south of Cape Mendocino as shown in this study is similar to density figures reported for C. helgoland1cus in the CALCOPI atlas number 2 in 1958 and 1959 (Fleminger, 1964). Since the majority of samples reported in this atlas are well below Cape Mendocino this species is most likely C. p. callf• ornicus Brodsky. Pleminger (personal communication) does recognize C. glaclalis as a separate species. The atlas also indicates that the highest concentrations occur near- shore between San Francisco and Los Angeles. Since sampling occurred at a time after the Davidson Cur• rent is usually at its peak, the generally low abundance of C. p« californicus in the sub-Arctic water north of Cape Mendocino is possibly an indication that those specimens present represent relics. It is possible that breeding popula• tions of this species do not occur along the coast of Washing• ton, Oregon and northern California since the number of Stage-V copepodites encountered in the region outnumbered the adults, but farther south the reverse was true. The copepodite Stage- V of Calanus is a hardy overwintering stage and will with• stand environmental fluctuations and extremes that the other stages cannot tolerate (Marshall and Orr, 1955). If true for Cp. californicus, the result would be that adults carried north by the Davidson Current would have a higher mortality rate than the Stage-V copepodites when the counter current breaks down and sub-Arctic water predominates: thus the adult to Stage-V ratio is altered in favor of the juvenile over• wintering stage. It has been shown for two copepod species off the Oregon coast that the seasonal cycle of currents and associated water bodies is influential on copepod distribu• tions (Cross and Small, 196?). Acartia danae was found dur• ing the winter in Davidson Current water, but in summer the concentration became less and a second copepod, Centropages mcmurrichi, appeared in water of northern origin. During periods of change (the breakdown of the Davidson Current in late winter) sporadic.low density occurrences of both species were found (Cross and Small, 1967). The seasonal occurrence of A. danae off the coast of Washington in winter has suggest• ed a possible use of this species as an indicator of "southern water (Frblander, 1962). Ecological Studies in Indian Arm Results of the Indian Arm study show Calanus pacificus callfornicus in greater abundance than C. glaclalis. Further, the density of the former is similar to that found off central and southern California. There is little doubt from the eco• logical results that C. p. callfornicus can maintain a breed• ing population in this inlet. Speculating on the results of the distributional survey, Calanus pacificus callfornicus ,1s established as a breeding . population off southern and central California and is associ• ated with the Davidson Current water. The Davidson Current - provides a transport mechanism of relatively high rate, i.e., 0.5 knot (Reid, i960), which has the potential to carry the species north to the strait of Juan de Fuca. Tidal currents and. deeper onshore flow of water could transport the species into the southern inlets of British Columbia (Tully, 1942; Herlinveaux and Tully, 196l; Lane, 1962).. The spring and summer conditions of the water bodies in inlets such as Indian Arm are suitable for breeding, growth, and survival of adults, mauplii and. copepodite stages. The Stage-V copepodite is capable of survival until the following spring when it moults into the adult and breeding occurs. The breeding populations of British Columbia and California appear to be connected by the Davidson Current. This allows an intermittant connection > between the populations and Isolation within the species is not complete. Assuming that a peak in the abundance of adults is an indication of the period of breeding, there is a strong sug• gestion from the data that the breeding cycles,for Calanus glacialis and C. pacificus californicus are out of phase with one another. There is a period pf overlap when the number of C; glacialis adults is decreasing and C. p. californicus adults increasing. This period occurs in the early spring and is'the most important period with regard, to interbreeding. Further, it appears as though C. p. californicus may produce two broods during the year, one in late spring-early summer and one in late summer. C. glacialis on the other hand has only one breeding period. i The yearly cycle exhibited by Calanus glacialis in Indian Arm is: not unlike the pattern found, for Calanus in more north• ern waters. C. finmarchicus breeds only once a year in west Greenland and Ungava Bay (Fontaine, 1955? Maclellan, 1967), but in the warmer regions of the Clyde Sea and English Channel this species may produce several broods (Marshall and Orr, 1955). Copepods of the Arctic and Sub-arctic breed.and spawn so that the young often appear at the beginning or at the peak of phytoplankton blooms. Such peak periods of primary pro• duction are sudden and. over the year the relative time of high primary productivity is short (Dunbar, 1968). Obviously survival of second and third broods would be less once the yearly period of high productivity had reached,its peak, and the pattern often found in such northern species is a life cycle that may span a period of one, two or more years (Dun• bar, 1968).' In Indian Arm, C. glaclalis begins to moult to the adult stage about a month before the first phytoplankton bloom is in evidence. During the two months in which the chlorophyll analyses were taken in this survey, the develop• ment of the yearly cycle of both species of Calanus was also noted. In February 1968, some chlorophyll A was measured, but in March 1968, the measurement of chlorophyll A showed a marked increase over the preceding month. C. glaclalis had started, to moult in January, in February the number of adults had increased nearly 50% over the previous month, and. in March the number of adults was at its peak. About two months after the peak in adults,, a peak occured. in the S-:tage-V copepodites of C. glaclalis suggesting that the time for egg maturation and subsequent development for juveniles is not unlike that reported, for C. finmarchicus. It is curious, however, that C. glacialls retains a yearly cycle pattern typical of the Arctic and sub-Arctic animals whereas popula• tions of other species, i.e., C. finmarchicus, appear to have a.different yearly cycle In temperate than in more northern cooler waters. The males of Calanus glacialls in Indian Arm are only present for a short time. This species is considered repre• sentative of Arctic and sub-Arctic fauna (Jaschnov, 1955; Duhbar, 1968) and the males of Calanus appear to be more sen• sitive to environmental changes than the females (Marshall and Orr, 1955).. Conceivably then, the lack of a second brood in this species could be due to the inability of the males to survive the summer conditions in the inlet. A second possi• bility is based on Gause's'.^; principle;, and natural .selection. C. glacialis breeds earlier than C. p. californicus and, as a result, animals at a comparable stage of development are not present at the same time. If comparable stages of both species were present, competition could result in the exclusion or reduction in number of one or the other species, but when com• parable stages are not coincident, competition may be absent or reduced and. both species are able to maintain breeding populations. The members of a species which breed at a time when such competition is at a minimum, are selected for since these are the individuals that persist and subsequently breed when proper environmental conditions again prevail. Onset of moulting can be induced by increased temperature and abundant food in the laboratory. Stage-V copepodites, taken at a time of the year when the majority of the popula• tion is in the overwintering stage, will start to mbult, when food, organisms are present. This occurs even at low tempera• tures (5° C). In January 1968, however, gtage-V C. glacialis moulted as well without food as when food was added. Since primary productivity in the environment was low during this month and. 5° C and 10° C experimental temperatures showed little effect on moulting rate, it would appear that some other factor or combination of factors is involved iniinducing moulting the adult stage in this species. No such anomaly was noted for C. p. californicus. One possible factor that was not tested is the increasing length of day at this time of year. The ecological results show that the stage-V of C. glacialis occurs mainly in water below 100 meters depth, how• ever, and, it seems unlikely that changes in length of light period has any real effect at this depth, particularly since this stage undergoes very little vertical migration. The possibility of food acting as a stimulus should not be ruled out. Little is known of the minimum amount needed to stimu• late moulting and. the amount of food, organisms present in January 1968 particularly with regard to flagellates and other smaller organisms was not determined. The lack of measurements in the preceding months as well makes it difficult to determine if any increase in available food occurred. The slight or no change in the moulting rate of both forms between 10° and 15° C (Pig. 24) is probably an indication of a minimal reaction time which an animal from the natural environment requires before moulting, i.e., the reaction to the experi• mental . temperature and, abundant food elicits a series of phys• iological changes which eventually result in moulting, but this process requires a minimal time period. Prom the results in Indian Arm, there is evidence to support the hypothesis that the two species occupy different bodies of water. The reactions of males, females and Stage-V copepodites within the populations of each species appear to differ, particularly in C. glacialls. Over the period of study the three water bodies in In• dian Arm, defined on the grounds of temperature and salinity, appear to be consistently present. Calanus glaclalis Is pri• marily associated with the deep layer, whereas C. p. callf• ornicus is primarily found, in the intermediate water. The deep layer is more uniform over the year with respect to fluctuations in temperature and salinity than-the intermedi• ate or surface layers. This may be an influential factor in determining the vertical position of the two species and, in fact, C. p. callfornicus may be more tolerant of such fluc• tuations. The distributional survey showed that Calanus pacificus callfornicus was more abundant in waters of relatively high temperature and salinity. In Indian Arm, however, the salin• ities are noticeably less dilute than those encountered any• where along the open coast and only in the summer do the tem• peratures approach conditions comparable to these found off California. C. glacialls occurs in waters which are much cooler than those found over the year in Indian Arm deep and intermediate water and, with regard, to salinity, Indian Arm is more dilute than the sub-Arctic water with which the species has been associated in the open sea. Despite these differ• ences both species are able to survive and reproduce in Indian Arm and a preference with regard to habitat is evident. On these grounds the conditions which determine a suitable habi• tat for either species Include more than temperature and sal• inity although these factors may be influential when one or the other becomes limiting. A-noticeable reaction occurred in May and June 1967. Dur• ing this time temperature and salinity over the- water column was more uniform than at any other time. The indication based on the findings of Gilmartln (1962) was-that an overturn had occurred. This is the only period when extreme vertical migrations were evidenced, particularly in the case of Stage-V C. glaclalis, and If this species is normally associated with water of a particular type the reaction of this stage may also be evidence of such an overturn. In all the other sampling periods the stage remained in the deep layer. Vertical communities have been described for the Gulf of Maine (Bigelow, 1926) so that the occurrence-of different associations of animals at different depths is not unique. Segregation of males, females, and Stage-V's has been noted, for C. finmarchicus, and the behavior with respect to deep habitat and lack of vertical migration is similar to that found for C. glacialls in this study (Nicholls, 1933). The males and Stage-V's occurred mainly in the deep layer and, with the exception of May 1967,: neither of the two stages migrated extensively. The females on the other hand under• went a definite migration In most sampling periods except in September 196? and January 1968. During the former period most of the C. glacialis population was in the overwintering Stage-V and in the latter period moulting to the adult stage was just beginning to occur. In both cases the total number of females is less than that found at other times and a com• parison of migration patterns when relatively low numbers are present may lead to false conclusions. The occurrence pf the main female population somewhat above the other two stages has been noted for C. finmarchicus (Nicholls,. 1933). In In• dian Arm, the female C. glacialis usually appears in the lower part of the intermediate layer. During the early months of the year when the C. glacialis population is beginning to moult, copulate, and spawn, this vertical displacement of the females is puzzling. When females with spermatophores were tallied, however, it was noticed that the bulk of the females with an attached spermatophore occurred somewhat be• low the main female population and was closer to or overlap• ped with the range of the males of the species. For C. fin• marchicus around the British Isles, a period of one month elapses between moulting to adult and, maturation of the eggs (Marshall and Orr, 1955). Remembering the similarities of the yearly cycle for local C. glacialis and that described for C. finmarchicus, the female C. glacialis in Indian Arm that oocur above the males have probably been fertilized and are in the process of maturing eggs. Those females occurring deeper usually bear spermatophores indicating copulation in the near past. They also occur near the main population of Stage-V copepodites of the species. These C. Z females are probably newly moulted, and soon afterward they are ferti• lized by the males. A migration upward then ensues while the eggs mature. Since energy is needed for egg production and most of the primary productivity takes place In the upper layers,' this upward, displacement of the females may have sig• nificance in terms of obtaining energy for egg production. Females maturing eggs are nearer a food source. Also it has been shown that egg laying coincides with the occurrence of phytoplankton blooms (Dunbar, 1968) with the supposition that young are not produced until sufficient food is available for their survival. The adults can maintain themselves on food reserves built up during the Stage-V condition, but the young lack such reserves after the yolk has been used up. This oc• curs about the third nauplius stage (Marshall and Orr, 1955). A vertical displacement of the females maturing eggs may be an indication of an environmental adaptation. Thus the young, when hatched, are closer to the main food source in the water column and consequently have a greater chance for survival than young hatched in deep water, well below the region of maximum food supply. A third possibility explaining this up• ward movement of the female population lies in the fact that an egg released, in the upper or surface water takes longer to sink and reach bottom than an egg released in deeper water. A period of 24 hours is required for hatching in the eggs of C; finmarchicus (Marshall and Orr, 1955). and. survival of an egg once it becomes mired at the bottom is doubtful; thus the greater the distance an egg can sink before nearing bottom the greater the chances of survival of the nauplius upon hatching. i Vertical separation of males, females, and Stage-V's of C.i pacificus californicus is not as evident, and contrary to C. glacialis all three stages appear to migrate vertically. There is a good degree of overlap between males and females of this species and since they.live in or near to the region of maximum primary productivity a vertical displacement of the females toward the upper layer is not necessary If the foregoing hypothesis is true. • The presence of a food source in the deep layer has been confirmed by the chlorophyll analyses and horizontal tows with fine mesh nets. Gut content analyses confirmed the presence of deep occurring food, organisms in the animals. The food available may not be sufficient to sustain the younger stages since a sudden increase in numbers of Calanus must occur if each female releases a number of eggs. The nauplii may not eat the same type of food as the adults, but the early cope• podite stages have oral appendages similar to the Stage-V and. adults and have the potential to compete with the later stages for similar food, organisms. As a result the upward displace• ment of ovigerous females toward a more abundant food source may be an adaptation necessary to the survival of the species. Although both species are morphologically similar and appear to be closely related, there are a number of distinct differences not only in external morphology but in their dis• tribution and general ecology. If they are to be recognized as distinct species then two populations such as"those of Indian Arm must be reproductively isolated. Many thousands of specimens of both species were examined in this study. Animals from various regions and. from different times of year were subjected to detailed morphological analy• sis, but at no time was there an appearance of a form which could, be construed as being intermediate between Calanus. glacialls and C. pacificus callfornicus. A priori it would appear that the two groups are reproductively isolated, and. even though copulation may occur between them development Is incomplete. The ecological data from Indian Arm shows the yearly cycles to be different although there is a period, when inter• breeding could, occur. This time is usually in the late winter-early spring during which the population of adult C. glaclalis is waning and the population of adult C. p. callf• ornicus is increasing. When this pattern was noticed, in early 1967 a series of 24 hour stations for early 1968 was scheduled so that the detailed reactions of the two popula• tions during this critical time could be studied. The vertical distributions, particularly over a 24 hour period, show that the potential for breeding between C. gla- t cialls males and C. p. californicus females is very low. In general the C. glacialis males occupied the deep water whereas the C. p. californicus females were generally In the middle or upper part of the intermediate water. Over any one 24 hour period there was no real change in the relative positions of these males and females. On the other hand, overlap between C. glacialis females and C. p. californicus males occurs and is particularly evident in March 1968 over the 24 hour period. The overlap between these two typesaappears greatest about the time the female C. glacialis start to move upward in the water column presumably while maturing their,eggs. Supposed• ly these females have been fertilized while in the deep water with the male C. glacialis. but since little.is known about the frequency of copulation for any one Calanus female, the possibility for copulation with C. p. californicus males ap• pears to exist. The evidence provided by tallying the number of females with spermatophores supports the hypothesis that reproductive isolation is present. During March 1968, when the overlap be• tween C. glacialis females and C. p. californicus males was most evident, none of the former had. spermatophores attached but, in the population of C. p. californlcus.females present at this time, a distinct proportion were observed with sper• matophores. If Interbreeding were to occur to a significant degree, one would expect to find spermatophores on the C. glacialis females since male C. glacialis decreased consider- ably in abundance at this time. During times when males of C. glacialls are low or absent, in number the occurrence of spermatophores on the females Is rare or absent all together. This same correlation has been noted for C. p. callfornicus. In February 1968 there was some overlap over,a 24 hour period, between C. glaclalis females and C. p. callfornicus males, but when the distribution of G. glacialls females with attach• ed spermatophores was noted, they were found mainly below the majority of the C. p. callfornicus males and overlapped sig• nificantly with male C. glacialls. The overlap between males and. females over a 24 hour period, for Calanus glacialls, was greatest in January 1968, when the species began moulting to the adult stage. In Feb• ruary : the total number of adults of this species increased, and the" population of females started to move upward so that overlap with the male population lessened. By March the num• ber of adults decreased, particularly the male contingent, and the female population had. migrated upward to the Inter• mediate layer. If both forms were to behave as good species in the sense employed, by Mayr (1942), then.gene flow between the two popu• lations would be blocked. The-blocking mechanisms are not al• ways apparent in planktonic species, particularly since obvious geographical barriers and wide separation of reproducing popu• lations do not always exist. Only through a thorough ecologic• al analysis can the taxonomic relationships between popula- tions 6f similar, closely related organisms be clarified. The results of the field study in Indian Arm, British Colum• bia, revealed a different pattern of yearly cycles and ver• tical distribution between the Large and Small Form of toothed Calanus. 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Mayr, E. 1942. Systematics and the Origin of Species. Dover Pub. 1964. 334 pp. . Mullin, C. H. 1968. Egg-laying in the planlctonic copepod Calanus helgolandicus (Claus). Crustaceana, supplement No. 1, pp. 29-34. Park, Tai Soo. 1968. Calanoid Copepods from the central North Pacific Ocean. U. S. Fish and Wildlife Service Fishery Bulletin 66(3): 527-572. Raymont. J. E. I963. Plankton and Productivity in the Oceans. Macmillan Co., New York. 660 pp. Reid, J. L. i960. Oceanography of the northeastern Pacific Ocean during the last ten years. California Cooperative Oceanic Fisheries Investigations, Reports VII.. Pp. 77-90. Jan. I960. Reid, J. L., G. I. Roden and J. G., ¥yllie. 1958. Studies of the California Current System. California Cooperative Oceanic Fisheries Investigations. Progress Report 1 July 1956 - 1 January 1958. Pp. 27-56. Sars, G. 0. I903. Art Account of the Crustacea of Norway. IV. Copepodai Calanoida. Bergen. Pp. 1-171. Shan, Kuo-cheng. 1962. Systematic and ecological studies on Copepoda in Indian Arm, British Columbia. M.Sc. Thesis, Univ. of B.C. Strickland, J. D. H. and T. R. Parsons. 1965. A Manual of Sea Water Analysis. Pish,. Res. Bd. Canada Bull. No. 125, 2d ed. Ottawa, 1965. Sverdrup, H. U. 19i+3- Oceanography for Meterologists. Pren• tice-Hall Inc. Pub. 2i|6 pp. Tullyj J. P. 191+2. Surface non-tidal currents In the ap• proaches to Juan de Fuca Strait. J. Pish. Res. Bd. Canada, 5(1+): 398-1-.09. Waterman, T. H. I960. The Physiology of Crustacea. 2 Vols. Academic Press, New York, London. 1315 pp. Wilson, C. G-. 191+2. The copepods of the plankton gathered ' during the last cruise of the Carnegie. Carnegie Cruise 7 (1928-1929), Biology Nos. 1-F^ 1950. Copepoda gathered by the United States Fisheries Steamer Albatross from 1887-1909, chiefly'in the Pacific Ocean. Bull.„TJ. S. National Mus. 100(Vol. 111., Pt. k): 1J+1-W. With, C. 1915. .The Danish-Ingolf Expedition. Copepoda. I. Calanoida Amphascandria. Vol. III(li). PROCEDURE WITH STRATIFIED PLANKTON NET TOWS It is nearly impossible to tow a net horizontally at pre• cisely the same depth at which temperature and salinity measure• ments are taken. The region sampled by a net covers a range of depths in the vicinity of the region sampled hydrographically. This is due to the sin wave pattern followed by a net when being towed as a result of fluctuations in speed of the ship, tidal currents, wind, deep currents and possibly internal waves. •5 Also, Aron et al (1965) have shown that changes.in sampling depth are greater for equivalent fluctuations in towing speed (or wire angle) at slow towing speeds than they are at faster towing speeds, and greater fluctuations in sampling depth occur when the amount of wire out is increased. The diameter of the towing wire and the type of depressor or weight used are two ad• ditional factors which need to be considered when trying to maintain a consistent depth with a sampler (Aron et al, I965). 17 ; • Since the opening and closing mechanisms of the Clarke-Bumpus nets fail to function efficiently at wire angles greater than 50° (about 2.5 knots with 50 lbs. of weight), slow speeds are a necessity. Trial tows using Kite-Otter and Isaacs-Kidd depres• sors proved to be unsuccessful in reducing the wire angle with increasing speeds, and lateral movement of the samplers became a problem. The diameter of the wire and the amount of weight at the end of the wire were kept constant throughout the sampl• ing program. 5/32 inch hydrographic wire and 50 lbs. of weight were used. Changes in weight of up to 200 lbs. appeared to have little effect in reducing the fluctuation in wire angle with changes in towing speed. By adequate spacing of water bottles and thermometers, a relatively detailed description of temperature and salinity conditions over the water column may be determined. This helps to compensate for the fluctuation in net depth during a tow, and a reasonable estimate of temperature and salinity over the towing range can be made. Nets should be spaced on the wire in such a manner that depth ranges sampled by them do not overlap. The approximate towing speed and resultant wire angle must be anticipated to do this. Often a trial run is advisable to es• tablish the proper ship speed and wire angle for the oceanic conditions prevalent at the time. In the inlets the commonest such oceanic conditions that may effect the wire angle are the tidal current, and wind with its effect on a ship towing at slow speeds. The majority of the ecological and distributional surveys were done with stratified tows. Clarke-Bumpus nets were spaced on the wire so that a 10° fluctuation in wire angle could be tolerated before depth ranges sampled by the nets would over• lap. The depth range sampled by a net at a particular position on the wire for a 10° wire angle change was determined from an angle chart. This chart (Fig. 1-1) was constructed with depths in meters on the vertical axis. Lines were drawn at 10° inter• vals with the origin at 0 meters. The lines for each interval were also scaled in meters. Figure 1-1. Wire Angle Chart. ANGLE CHART FOR ESTIMATI NG NET DEPTHS SCALE: 1cm =10m An arrangement such as this is based on the assumption that the wire behaves like a straight line during a tow. Rec• ords from the Bathykymograph indicate this is not the case. It is believed by other workers that the towing wire actually assumes a hyperbolic shape (Bary, personal communication). Further, these bathykymograph records show that the change in sampling depth for a concurrent change in wire angle is of a much smaller magnitude than one would predict from the angle chart. By using the angle chart to determine net spacing for avoidance of overlap in sampling range, one is actually over estimating the actual conditions and a margin of safety is introduced. To be absolutely certain of the depth of each net during a tow, a monitering device such as a time-depth recorder should be used. With one recorder placed by each net on the wire, a series of charts constructed from the recorder data would show the actual shape of the wire for various wire angles, and various amounts of wire out. Ideally, further observations made under various conditions of wind and tide would show the effect of these parameters. Unfortunately with the equipment available, this type of arrangement would interfere with the opening and closing messengers of the Clarke-Bumpus nets. In order to approximate the actual sampling depths, how• ever, a single time-depth recorder was placed immediately below the bottom net. During a tow the wire angle was monit- ered continuously, and the times when fluctuations in wire angle occurred were noted. Through this procedure, with a given amount of wire out, it was possible to associate par• ticular wire angles with particular depths. A working table was then constructed showing position of the recorder on the wire in meters, wire angle, actual depth attained by the re• corder for that angle, an equivalent straight line angle, and estimated sampling depths for nets placed at known positions above the recorder. The equivalent straight line angle is a quantity determined from the angle chart. Reading down the vertical axis of this chart to the depth determined by the recorder for a particular measured wire angle, the equivalent angle was defined as the angle of the line that intersected with the recorded depth at the position of the recorder on the wire. Figure 1-2 is an example showing how equivalent straight line angles were determined when the amount of wire out and angle of the towing wire were known. In this case the bathy- kymograph was placed near the end of the towing wire with 90 meters of wire out. The angle of the towing wire was 4-5° when the bathykymograph recorded a depth of 70 meters. Using this information the equivalent straight line angle was determined by reading down the vertical axis of the angle chart to 70 meters. Reading across the chart a line was found such that the 90 meter point on its depth scale intersected the 70 meter line. The angle of this line from the vertical axis was found to be 38°. This value is the equivalent straight line angle. Sampling depths of nets placed above the recorder may be estimated from this line, e.g., a net.placed at 60 meters on For a given amount of wire out, a relationship was estab• lished by plotting measured wire angles against their equivalent straight line angles. The resulting curves made it possible to approximate the degree of fluctuation in measured wire angle that could be tolerated for an equivalent fluctuation of 10° on the angle chart (Table 1-1). For the range of angles encounter- ed on a tow, the equivalent angles were determined, and the sampling ranges of the nets estimated. This estimate is still based on the assumption that the towing wire is straight but only from the shallowest to the deepest net. For ease in plot• ting, the median of the sampling range was considered the sampl• ing depth. . Normally no more than four Clarke-Bumpus nets were placed on the wire for any given tow. Each net had a counter that monitered the number of revolutions of an impeller mounted in the metal collar of the net frame. When this device was cal• ibrated by towing the nets over a measured distance the number of cubic meters of water filtered per revolution of the impell• er was determined. By recording the number of revolutions of this impeller for each tow, the amount of water filtered in cubic meters was determined, and subsequently the number of plankton specimens per cubic meter estimated. Figure 1-2. Example showing the determination of an equivalent straight line angle. 80- TABLE 1-1 DETERMINATION OF EQUIVALENT WIRE ANGLES IN 10° RANGES TOTAL WIRE OUT =.90 meters RANGE- OF MEASURED WIRE ANGLE RANGE OF EQUIVALENT ANGLES' 20° to 37° 20° to 30° 38° to 45° 30° to 40° 46° to 60° 40° to 50° TOTAL WIRE OUT = 200 meters RANGE OF MEASURED WIRE ANGLE RANGE OF EQUIVALENT ANGLES 20° to 42° 20° to 30° 42° to 55° 30° to 40° 56° to 60° 40° to 50° THE EXTERNAL MORPHOLOGY OF THE TOOTHED CALANUS SPP. ' FROM THE WATERS OF SOUTHERN BRITISH COLUMBIA, CANADA ORDER. Copepoda Crustacea with head, thorax and abdomen. Head' of six co• alesced somites, rounded anteriorly or with rostrum, without carapace, with median naupliar eye but without compound eye. Thorax composed of at least 7 somites some of which are not- fused; each usually with 1. pair of appendages. First appendage pair modified to form maxillipeds, last 1 or 2 pairs often re• duced or absent, remaining pairs biramous and natatory. Abdo• men with maximum of k segments, devoid of appendages. Telson with 1 pair of caudal rami. Division present between fifth and sixth, or sixth and seventh thoracic somites distinct, dividing body into anterior prosome and posterior urosome. (Prosome composed of head and most of thorax. Urosome composed of last 1 or 2 thoracic somites and abdomen.) Antennules uniramous, usually conspicuous. Antennae often biramous, often prehensile. Mandibles frequently with biramous or uniramous palp. Maxillae with opening of maxillary gland at base. Maxillipeds frequently prehensile. Fifth pair of thoracic legs frequently modified for sperm transfer in male. Large copepods with oval body, urosome about 1/3 the length of prosome. Head or anterior-most tagma well defined or coalescent with first pedigerous segment; 2 rostral filaments present anteroventrally. Fourth and fifth pedigerous segments rarely fused. Lat• eral posterior conners of fifth pedigerous segment often rounded. Urosome 5-segmented in male; generally 4-segmented in female. Caudal rami with 6 setae. Antennules long, 16-25 segments in female, 15""24 segments in amel. Often thickened proximally in male, some proximal articulations fused, covered with setae and aesthetascs. An• tepenultimate and penultimate segments with 1 strong plumose seta posteriorly. Antennae biramous, rami nearly equal in length. All 5 pairs of legs generally natatory with three segment• ed exopodites and endopodites. First 2 anterior pairs sometimes with 1 or 2 segmented endopodites; fifth pair of legs in female same as preceding pairs, or in various stages of degeneration. Fifth pair in male often modified, asymmetrical, prehensile. Coxopodites of fifth legs smooth or denticulate on inner surface. Cephalosome fused with or distinct from thorax, fourth and fifth pedigerous segments never fused. Anterior end often slightly carinated dorsally, particularly in male. Urosome 4-segmented in female with genital segment slight• ly protuberant ventrally; 5-segmented in male. Caudal rami symmetrical with second seta from inner surface longest. Antennules 25-segmented in female, first 2 segments often fused in male; generally longer than body in both sexes. In males seta on antepenultimate segment noticeably shorter than seta on penultimate segment. Antennae with 7-segmented exopodite nearly equal in length to 2-segmented endopodite. Thoracic legs natatory, exopodites and endopodites 3- segmented. Exopodites of first 4 pairs of 1, 1, and 2 spines on outer surface of respective segments; terminal segment with apical spine. Endopodite of first pair with 1, 2 and 6 setae, respectively. Terminal segment of endopodites of second and third legs with 8 setae, those of fourth legs with 7 setae. Coxopodite of first 4 legs usually with stout plumose seta on inner surface. In females fifth legs similar to preceding pairs. In males fifth legs slightly asymmetrical, left exopodite longer; both exopodites without setae. Inner surface of coxopodite denticu• late or with solitary seta. SMALL FORM. Calanus sp. (Shan, 1962) Prosome (plate I) 2-parted, cephalothorax forming anterior part, 5 free thoracic somites forming posterior part. Cephalo• thorax consisting of head and first thoracic somite (Marshall & Orr, 1955). Anterior surface of head slightly protuberant. Ros• tral filaments present, situated anterior to anterinule. Small solitary hair-like processes present on anterior surface of head. Posterior dorsal surface of cephalothorax protuberant slightly at line of division with first pedigerous somite. First pedigerous somite between 1/3 and 1/2 the length of cephalothorax. Pedigerous somites 1 through 5 decreasing in length and width posteriorly. First pedigerous somite form• ing widest part of prosome, anterior edge slightly wider than posterior edge of cephalothorax. Lateral surface of third pedigerous somite with 2 setules, 1 near division with second pedigerous somite, second near divi• sion with four pedigerous somite. Fourth pedigerous somite with 1 setule laterally, near division with fifth pedigerous somite. Posterior lateral surface of fifth pedigerous somite ex• tending posteriorly to shield anterior lateral portion of genital segment. Posterior lateral margin of fifth pedigerous somite roundedi dorsal and ventral surface U-shaped not extend• ing over junction with genital segment. Urosome (plate I) four-segmented with 2 caudal rami. First, or genital segment, longest and widest, with 2 conspicuous spermathecae. Ventral surface parallel to main axis of uro• some at region of genital pore. Successive urosome segments shorter and narrower poster• iorly} segments 3 and 4 of nearly identical length. Caudal rami longer than wide, each with 4 terminal plumose setaet second seta from inner surface longest. 1 sub-terminal plumose seta on outer surface, 1 sub-terminal plumose setule on inner surface. Antennule (plate II). 25 segmented, first and second no• ticeably larger. Segments 3 to 9 nearly equal in length, width decreasing slightly with each successive segment. Segments 10 and 11 slightly longer than 1 - 9* Segments 12 to 25 markedly longer than wide; width of each segment decreasing slightly. Segments 15 to 19 nearly equal in length. Segments 20 and 21 of nearly equal length, but slightly shorter than segments 15 to 19. Segment 22 with plumose setule on posterior surface. Seg• ments 23 and 24 each with single long plumose seta on posterior surface, setae of equal length. Segment 25 with sub-terminal seta on anterior surface and 4 terminal setae. Antenna (plate III). Biramous, protopodite 2-segmented, basis larger than coxa. Exopodite 7-segmented, endopodite 2- segmented. Two setae on anterior edge of basipodite. One plumose seta on coxa. First 2 segments of exopodite each with 2 long plumose setae on outer surface. First segment wider than long, longer on side nearest endopodite. Second segment slightly longer than wide; some specimens with length and width equal. Seg• ments 3» 4, 5. and 6 shortest} each with 1 plumose seta on outer surface. Width of ramus decreasing to segment 5s segment 6 slightly wider and proximal end of segment 7 nearly as wide as distal end of segment 2. Segment 7 tapers toward distal end. This segment with one plumose seta on middle of outer surface, 3 plumose setae on terminus. Endopodite 2-segmented, proximal segment nearly as long v as exopodite. Outer sui-face with 2 plumose setae near distal end. Shorter terminal segment bilobed, outer lobe with 5 large plumose setae, 3 smaller plumose setae on outermost surface, and 1 small seta at base of inner edge. Inner lobe with 6 large plumose setae, and 1 small setule nearer inner surface. Mandible (plate IV). Biramous, protopodite 2-segmehted. Coxopodite longer than basipodite and endopodite combined. Segment nearly perpendicular to remainder of appendages toothed edge overlies labrum. Posterior corner of toothed edge with conspicuous tooth or spine. Lateral surface with 1 short plumose setule proximally. Basipodite irregular; inner edge longer than outer, with 3 setae on protuberance about 1/3 the length from articulation with endopodite, a fourth seta near mid-point of inner surface. Endopodite 1-segmented, slightly longer than half the length of basipodite. Protuberance on lateral surface with 4 setae, 10-plumose setae on terminus. Exopodite 5-segmented. Four proximal segments with one plumose seta, terminal with 2 plumose setae. Maxillule (plate IV). Gnathobase with 13 short plumose setae, on inner surface; 1 short setule on anterior surface. First exite with 7 plumose setae on terminus, 2 plumose setae nearer base. First endite much smaller than first exite, lobelike, with 4 plumose setae on terminus. Second exite small, often hidden by first exite in mounted specimens, with 1 plumose seta on terminus. Second endite (first lobe of basipodite) with 4 plumose setae on distal end, shape similar to first endite. Second lobe of basipodite appears as protuberance near base of endopodite. Distal surface with 4 plumose setae. First lobe of endopodite appears as a lobe distal to sec• ond lobe of basipodite, with 4 plumose setae on terminus. Second lobe of endopodite with 2 groups of plumose setae. One with k plumose setae distal to first lobe, other on distal end with 7 plumose setae. Exopodite a curved segment arising between second exite and base of endopodite, segment bearing 11 plumose setae. Maxilla (plate V, fig. 3).- Three-segmented. Proximal segment with 6 plumose setae grouped on inner surface distally. Second segment with 3 groups of 3 plumose setae each on lobe• like structures on inner; surface. One plumose seta on outer surface near proximal segment. Distal segment with 4 setae on lobe-like structure on inner surface, 1 setule near base of lobe, 6 plumose setae in succession to terminus distal to lobe, 2 plumose setae sub-terminal in center of anterior sur• face. Maxilliped (plate V, fig. C). Eight-segmented. Proximal segment largest, with 3 groups of plumose setae, most proximal group with 3 other 2 groups with 4 setae each. Second protopodite segment with 3 plumose setae grouped in center of inner surface. Third segment smallest, with 2 plumose setae on inner surface near distal articulation of second protopodite segment. Fourth segment with 4 plumose setae grouped on small lohe in middle of segment near inner surface. Fifth and sixth segments nearly identical. Fifth with 4 plumose setae in group near distal articulation in inner sur• face. Sixth segment with 3 plumose setae in comparable posi- " tion. Seventh segment with one plumose seta on outer surface near proximal articulation, with 3 plumose setae on inner sur• face near distal articulation. Eighth segment with 3 plumose setae on terminus, with 1 sub-terminal plumose seta on outer surface. Anterior or first pair of swimming legs on second thoracic somite (plate VI, figs. A & B). Coxopodite with one plumose seta on inner surface. Basipodite with one curved plumose seta on anterior surface, adjacent to articulation with endopodite. Endopodite 3-segmented, shorter than exopoditej proximal seg• ment widest, with one plumose seta on inner surface. Second segment with 2 plumose setae on inner surface. Terminal seg• ment longest with 3 plumose setae on inner surface. . Exopodite 3-segmented. Proximal segment with one seta on inner surface» one spine on outer surface adjacent to articula° tion with second segment. Second segment similar to proximal segment but smaller. Distal segment.with 3 plumose setae on inner surface, one sub-terminal plumose seta, one terminal plumose seta plus one seta-like spine.^ Terminal seta with membrane along outer surface, plumosities along inner surface.1 Terminal segment also with seta-like spine on outer surface 1/3 length from terminus. As with endopodite, proximal segment of exopodite broadest while terminal segment longest. Second pair of swimming legs symmetrical} on third thoracic somite (plate VII, figs. A & E). Coxopodite largest with one plumose seta on inner surface, and plumosities extending from seta to interpodal plate. Basipodite with no setae, but with spine on outer surface adjacent to articulation with exopodite. Endopodite 3-segmented; basal segment with one plumose seta on inner surface, distal outer surface drawn off to spine• like point. Second segment with 2 plumose setae on inner sur• face; outer surface drawn off to spine-like point near articu• lation with terminal segment. Terminal segment with 4 plumose setae on inner surface, 2 plumose setae on terminus, and 2 plumose setae on outer surface. Outer surface of second and 1. See discussion under description of exopodite of first swimming legs for Calanus pacificus californicus males. Exopodite 3-segmented, proximal segment with one plumose seta on inner surface, spine on outer surface, both adjacent to articulation with second segment. Proximal segment also with 2 "flap" on outer distal surface covering part of articulation. Second segment with one plumose seta on inner surface near articulation with terminal segment. Spine and "flap" occur adjacent to distal articulation. Distal segment with 5 plumose setae on inner surface, one long and one short spine on termin• us, one short spine 1/3 length from terminus. Third pair of swimming legs on fourth thoracic somite; essentially same as second pair but longer (plate VII, figs. B & F). Fourth pair of swimming legs on fifth thoracic somite; slightly longer than third pair (plate VIII, figs. A & C). Coxopodite longest segment with one plumose seta on inner sur• face. Basipodite nearly as long as wide, with.no setae. Short spine on outer surface near articulation with exopodite. Be• tween articulation with exopodite and articulation with endo• podite on anterior distal surface, a conspicuous spine-iike extension present. Distal posterior surface appears to overlap with exopodite. Endopodite 3-segmented. Proximal segment shortest/second segment about twice as long, and distal segment about four times as long. Proximal segment as in second and third legs. 2. These "flaps" appear to be extensions of the more proximal of two adjacent segments. They may be membranous in nature. Distal segment with 3 plumose setae on inner surface, 2 term• inal setae, and 2 setae on outer surface; segment differs from second and third legs in this aspect. Exopodite 3-segmented. Proximal segment shortest, with second and third segments progressively longer. This ramus identical to exopodites of second and third swimming legs. Fifth pair of swimming legs on sixth thoracic somite (plate IX). Legs symmetrical, shorter than third or fourth legs. Coxopodite with a row of teeth on inner surface; this row slightly concave near middle of segment. Basipodite similar to fourth swimming leg. Spine^like extension on anterior distal surface near articulation with endopod particularly evident. Endopodite 3-segmented. Proximal segment smallest, second segment slightly longer, distal segment about 2.5 times as long as proximal. Distal segment proportionately not as long as distal segment of endopodite of fourth leg. Segments 1 and 2 each with one plumose seta on inner surface. Distal (third) segments with 2 plumose setae on inner surface, one sub-terminal and one terminal plumose seta on distal end; one small plumose seta on outer surface about 1/3 length from tip; some specimens with additional plumose seta on outer surface. One short tooth• like spine just lateral to distalmost terminal seta. Exopodite 3-segmented. Proximal segment as in second leg; but with no setae. Second segment nearly equal in length to proximal segment, similar to corresponding segment of second leg. Distal segment with 4 setae on inner surface, one long spine and one short spine on terminus with short spine outside long spine. Outer surface, with short spine about 1/3 length from terminus. Longest terminal spine on exopodite of legs 2 through 5 with membrane-like structure along outer surface. Inner sur• face with fine plumosities. MALE. • Prosome (plate XI, fig. A) 2-parted as in female. Anter• ior surface of cephalothorax markedly protuberant, with small protuberance neai-ly opposite antennules on dorsal surface, and posterior dorsal surface produced markedly at point of division with first free thoracic somite. First free thoracic somite about 1/3 length of cephalothorax. Remainder of prosome as for small female. Urosome 5-segmented with 2 caudal rami. First segment peduncular with proximal end noticeably narrower than distal end. Articulation of first segment shielded laterally by posterior extensions of sixth thoracic segment. Second seg• ment longest. Width of distal end of first segment and width of second segment nearly equal. Successive segments narrower and shorter. Caudal rami' nearly equal in length to third seg• ment. Setae on caudal rami identical to small female. Antennule (plate XI, fig. A) 24-segmented. Proximal or first, segment largest, conspicuous macroscopically. Second segment markedly smaller, slightly angular on anterior surface, with conspicuous setule near distal articulation. Segments 2 to 8 wider than long; each succeeding segment from proximal to distal tapered in appearance. Segments 9 and 10 nearly as wide as long. Segments 11 to 24 markedly longer than wide. Segments 12 to 18 of nearly equal length,but decreasing width thus tapered in appearance. Segments 19 to 22 all nearly equal in length, but slightly shorter than segments 12 to 18. Segments 2 3 and 24 nearly equal in length but shorter than segments 11 to 22. Segment 21 with setule on posterior surface near ar• ticulation with segment 22. 2 large conspicuous setae on pos• terior surface of segments 22 and 23; seta on segment 22 (ante• penultimate segment) longer. Terminal segment with 4 setae and aesthetasc on distal end. Sub-terminal setule on anterior surface. Male antennule with many more aesthetascs on outer or anterior surface than female antennule. Antenna (plate XII, fig. B), biramous, protopodite 2-seg- mented, basis with conspicuous, plumose seta. Coxa larger and orbiculate, with 2 plumose setae on anterior surface near ar• ticulation with endopodite. Endopodite 2-segmented, exopodite 7-segmented. Exopodite similar to small female except second segment slightly longer than wide. Endopodite same as description for small female. Mandible (plate XIII, fig. B) similar in appearance to small female. Gnathobase of. coxopodite conspicuously dentate. Basipodite same as small female. Endopodite same as small female. Exopodite same as small female. Maxillule (plate XIV, fig. C) same as description for small female. Maxilla (plate XIV, figs. D & E) same as description for small female. Maxilliped (plate XV, fig. A) as in small female except seta on outer surface of seventh segment larger in male and re- flexed toward proximal end of appendage. Sub-terminal seta on outer surface of eighth or terminal segment also larger than in female and reflexed toward proximal end of appendage. Anterior or first pair of swimming legs on second thoracic somite (first free thoracic somite), and symmetrical (plate XVI, fig. A). Coxopodite largest segment with plumose seta on inner surface. Basipodite slightly wider than long, with curved plumose seta on anterior surface adjacent to articulation of endopo• dite. Segment shorter on lateral side. Endopodite. First or proximal segment nearly as wide as long, 1 plumose seta on inner surface. Second segment small• est, with 2 plumose setae on inner surface. Third or distal segment longest, with 3 plumose setae on inner surface, 2 plumose setae on terminus, and one plumose seta on outer sur• face about 2/3 of length from proximal end of segment. End of Exopodite. First or proximal segment broadest. Spine lateral to articulation with second segment. Inner surface with plumosities» distinctly rounded from proximal end to point of attachment of seta. Second segment shorter than first, not rounded, but with spine lateral to distal articulation, and with plumose seta on inner surface near distal articulation. Inner surface with plumosities. Distal segment longest, inner- surface with 3 plumose setae, terminus with one sub-terminal and one terminal plumose seta. Terminal seta with membrane structure as in small female. Outer surface with 1 seta-like spine near terminus and second seta-like spine about 2/3 of length from proximal articulation. (These seta-like spines are thick at their bases like spines, but tips taper as a tip of a setule.. They appear devoid of plumosities.) Second pair of swimming legs with coxopodite as in small female (plate XVII, fig. A). Basipodite wider than long with spine on outer surface adjacent to articulation with exopodite. Endopodite 3-segmented, basal segment smallest, segments length• ening distally. Outer surface of first 2 segments drawn off to a spine-like point lateral to distal articulations. First segment with one plumose seta on inner surface. Second segment with 2 plumose setae on inner surface. Terminal segment with 4 plumose setae on inner surface; one sub-terminal and one term• inal plumose seta, 2 plumose setae on outer surface. Exopodite 3-segmented, first with "flap" near outer sur• face of distal articulation just medial to lateral spine. (See description for small female.) Inner surface with plumosities, and one plumose seta. Segment rounded on inner surface with broadest region near distal end at base of seta, narrowest region at proximal end. Second segment similar to first or proximal segment, but more rhomboidal in shape. Proximal por• tion of inner and outer surface with plumosities. Distal seg• ment longest, with 5 plumose setae on inner surface, 2 term• inal spines, inner one longer and with membrane as described for small female; with a tooth-like projection between bases of these 2 spines. One spine on outer surface about 2/3 of length from proximal articulation. Pores evident near base of short terminal spine and spine on outer surface. Third pore sometimes noticeable about mid-way between proximal articula• tion and base of spine on outer surface. Third swimming legs (plate XVII, fig. BO similar to sec• ond but larger. Fourth pair of swimming legs (plate XVII, fig.. C). Coxo• podite nearly twice as long as wide, with plumose seta as in small'female. Basipodite wider than lorig; distal outer sur• face drawn off to short spine-like process but no distinct spine as in second and third legs. Spinose process on anterior distal surface evident as in small female. Endopodite with plumosities on outer surface of proximal and second segments arid proximal portion of distal segment. Plumosities also on proximal inner surface of second and dis• tal segments. Distal segment with 3 plumose setae on inner surface, one sub-terminal and one terminal plumose seta, and \ 2 plumose setae on outer surface. Endopodite like endopodite of second leg in all other aspects. Exopodite. Inner surface of proximal segment not rounded as in second and third legs. Distal segment as in second leg. Plumosities on proximal outer surface of second and distal segments and along entire inner surface of proximal segment and proximal portion of second and third segments. Fifth swimming legs (plate XIX, fig. A). Asymmetrical, left leg longer than right. Inner surface of both with row of teeth, concave near middle of coxopodite; row extends away from inner surface onto posterior surface of segment. Basipodite with inner surface longer than outer in both legs. Inner surface curved, outer surface straight. Distal anterior articulation surface adjacent to exopod with conspicu• ous spinose process. Outer surface, lateral to distal articu• lation, drawn off to small spine-like process. Endopodite. Segments increase in length from first or proximal to third or distal. First segment sub-triangular with proximal end much narrower than distal. Outer surface of both first and second segments drawn off to spine-like process distally. First and second segments each with one plumose seta on inner surface. Distal segment with 2 plumose setae on inner surface and 2 on outer surface. Sub-terminal plumose seta medi• ally; terminal plumose seta, plus terminal, spinose process lateral to it. Plumosities along inner and outer surfaces of second segment, and along proximal portion of corresponding sur• faces, of ^distal usegment^ •. Left exopodite longer than right. Segments decreasing in length from proximal to distal. Proximal segment with "flap" and spine lateral to distal articulation. Small pore on anterior surface just proximal to this spine. Second seg• ment shorter and narrower, with plumosities on inner surface. This segment with spine, "flap," and pore as in first segment. Distal segment oblong and shortest,Jwith short spine on outer surface about 2/3 length from base. Terminus with one short spine just latei-al to second slightly longer spine; also with small spinose process on anterior surface between these two spines. Plumosities along inner surface. Right exopodite with first 2 segments longer on outer surface. Both segments with flap-like process and spine as above, but both much shorter than corresponding segments on left exopodite. Shape like first 2 segments on exopodite of fourth swimming leg. Pores as in left exopodite. Plumosities proximally on outer surfaces of second and distal segments, along inner surfaces of segment 2 and proximally on inner sur• face of distal segment. Distal segment with spine on outer surface 2/3 length from proximal articulations one pore slightly more proximal to this spine. Terminus with 2 spines, outer• most shorter; short spinose process between these two. Longer of 2 terminal spines without membrane structure. Right exopodite slightly shorter than first 2 segments of left exopodite. First 2 segments of right exopodite slightly longer than first segment of left exopodite. LARGE FORM: Calanus sp. (Shan, 1962) FEMALE. Prosome (plate I, fig. B) same as Small female except anterior and well rounded, mid-dorsal posterior margin of cephalothorax at point of division with second thoracic somite not produced as in Small female. Urosome (plate I, fig. B) with first segment longer than wide; more so than Small female. Description for Small female same for Large female. Antennule (plate II, fig. A). Same as description for Small female. Both females with partial fusion between seg• ments 8 and 9« Antenna (plate III, fig. A) with protopodite as in Small female. Exopodite with second segment slightly wider than long thus differs slightly from Small female. Remainder of ramus identical to description for Small female. Endopodite same in appearance as Small female. Mandible (plate IV, fig. B) same as Small female. Maxillule (plate IV, fig. D) same as Small female. Maxilla (plate V, fig. A) same as Small female, except for additional setule on third or terminal segment of appendage. This setule near proximal end of segment near site of setule described for Small female. Maxilliped (plate V, fig. E) same in appearance as Small female. First pair of swimming legs (plate VI, fig. C) same as Small female. Second pair of swimming legs (plate VII, fig. C) same as small female. Third pair (plate VII, fig. D) and fourth pair (plate VIII, fig. B) of swimming legs same as Small female. Fifth pair of swimming legs (plate X, fig. A) same as Small female except for proportionate length differences in the distal segment of the exopods as noted in the results sec• tion. Also, third or distal segment of endopodites either with 5 °r 6 setae. This feature not consistent between forms• e.g., one animal may have 6 setae on left terminal segment znd 5 on right. Large females with 6 rather than 5 setae more frequently than Small females. For males, 6 setae on distal segment common but not consistent. MALE. Prosome (plate XI, fig. B) with anterior cephalothorax slightly more produced than female but not as extreme as small male. Mid-posterior dorsal surface of cephalothorax at division with second thoracic somite not as markedly produced as Small male. Remainder of prosome as for description of Small male and female. Urosome (plate XI, fig. B) same as description for Small male, but width to length ratios differ for segments 3 and -4-. (See results section.) Antennule (plate XI, fig. B'; same as description for Small male. Partial fusion between segments 7 and 8 in males of both forms. Antenna (plate XI, fig. B) same as description for Small male. Mandible (plate XIII, fig. A) same as description for Small male and female. Maxillule (plate XIV, fig. A) same as description for Small female. Maxilla (plate XIV, fig. B) same as description for Large female. Maxilliped (plate XV, fig. B) same as description for Small male and Small female. (Note plumosities near proximal articulation of second segment in both forms.) First (plate XVI, fig. B), second (plate XVII, fig. D), third (plate XVII, fig. E), and fourth (plate XVII, fig. F) pairs of swimming legs same as description of Small male only- larger. Fifth pair of swimming legs (plate XVIII, fig. A) with coxopodite similar to Small male. Basipodite with spinose process on anterior surface of distal articulation near exo• podite not as conspicuous as in Small males. Endopodite similar to Small male. Left exopodite not markedly longer than right exopodite as in Small males; thus legs appear nearly symmetrical. De• scription for Small male same as for Large male but note pro• portionate differences discussed in results section. Right exopodite same as for description of Small male except right exopodite extends slightly beyond articulation of distal segment of left exopodite. First 2 segments of right exopodite markedly longer than first segment of left exopodite. PLATE VI a