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.