ABSTRACT
Ecology of Echinometra lucunter (Linnaeus), a West Indian echinoid.
Random samples of 100 urchins a month were taken from two contrasting locations in Barbados, West Indies for a period of one year. One location, Little Bay, was on the wave-swept northeast coast and the other, Graves End was on the relatively calm southwest coast of the island. The size and breeding condition of these urchins were measured. Data from Little Bay were analysed and compared with data obtained from Graves End. The two groups of urchins showed several significant differences in species characteristics as well' as a pronounced difference in the breeding cycle over a one year periode Four short behaviour experiments are included in the present study. These experiments were designed to test the reaction of E. lucunter to light and to test the hypothesis that E. lucunter is functionally bilat erally symmetrical.
Gail Doran Department of Zoology M.Sc. thesis ECOLOGY OF ECHINOMETRA LUCUNTER (LINNAEUS). a West Indian echinoid. bl" Gail Doran
A thesis submitted ta the Faculty of Graduate Studies and Research in par-
1 tial fulfilment of the requirements -for the degree of Master of Science.
Department of Zoalogy, April 1968 McGill University, Montreal, Canadao
,,'
~ Gail Doran 1968 ACKNOWLEDGMENTS
l am indebted to Dr. John B. Lewis, Director of Bellairs Research Institute of McGill University, for bis constant encouragement and advice throughout this project. Dr. D.M. Steven of the Zoology Department of
McGill University has greatly assisted in ~he preparation of.the; manuscript. Several students of Bellairs Research Institute deserve 'thanks for time spent helping me: D. Patriquin for collection aid and algae identification, C. Ooleman for collection aid and R.E. Chilcott for assistance with mathematical procedures. l am also grateful for the Many hours my husband, Lee D. Doran, spent discussing and offering'ideas for the present study. The field work was supported in part by a grant in aid of research from the National Research Couneil of Canada.
ii TABLE OF CONTENTS Page ACKNOWLEDGMENTS ••••••••••••••••••••••••••••••••••• ii
LIST OF TABLES •••••••••••••••••••••••• o· ••••••••••• v LIST OF ILLUSTRATIONS ••••••••••••••••••••••••••••• viii
INTRODUCTION •••••••••••••••••••••••••••••••••••••• 1 REVIEW OF THE LITERATURE General •••••••••••••••••••••••••••••••••••••• 4 Breeding of Echinoids •••••••••••••••••••••••• 7
Growth of Echinoids 0 ••••••••••••••••••••••••.• g Comparative Studies of Echinoids ••••••••••••• 11 Behaviour of Echinoids ••••••••••••••••••••••• 13
PART l - GROWTH, BREEDING AND COMPARATIVE STUDIES Materials and Methods...... 15 Results Growth...... 22 Breeding...... 32
Comparative Studies ••••••••••• ~ •••••••• o. 39 Discussion...... 57
ii1 Table' of Contents continued
Page PART II - BEHAVIOUR Introduction...... 66 -Materials, Methods and Results
Expèriment One ...... ~ ••• o...... 67 Experiment Two...... '70
:Experiment Three •••••• Il ...... _ 75 Experiment Four...... 78
Discussion~ ...... -••••••••••••_ ••••••••• 11- •••• CI .. 82
SUMMARY AND CONCLUSIONS ...... o.~... 84
LITERATURE CITED._ ..... 0 0 ...... CI ...... 0 .. .. • ...... 87
APPENDIX ...... '•••••••••••.•••••••• 0·.0 99
iv LIST OF TABLES
Table . Page
1. Information on gro\~h rates of echinoids gatheredfrom the literature...... 10 2. The correlation of· width, height and volume to length inurchins from Little Bay and . . . . Graves End, J~ne·1966 •••• ~ ••••••• " o...... 23 .,' . ". . 3. The spineandtest colouririgofLittle Bay
urébj,ns.,· •• 0 ••••••••••••••••••• ~ • • • • • • • • • • .. .40· 4. The spineand test.colouring of Graves .End
urcr~ns.·••••••••.• ~ •.•••.•.••••••.••••••••••••• 41 - . .-' ',,'" ,'...... 5l The spineand testcolouringof Little Bay and ..' .' " .. ' ... Graves Endurchins. Figures are expressed
as·pèrcentages ...... ~~ •••••••• ~. 42 6. Analyses of covariance of test thickness to . . '.' . ". . test length of urchins...... •• •••••••• 46 7. Analyses of covariance of test height to test length of urchins ••• ·•••••••••.••••••••••••• . 47 8. Patterns of'ocular plate insertion found in
. urchins from.Barbados.~...... 52 9. Patterns of ocular plate insertion found in urchins from Bermuda and the West Indies by Jackson (1912).. •.• •• •• • • • • • • • • • • • • • •• • • 53
v List' of Tables c:ontÙluèd Table Page 10. The frequency of occurrence of four pore-pair arc types in Little Bay and Graves End urchins...... 56 11. The reactions of Echinometra lucunter to an
overhead light (Experiment One) ••••••••• o. 69 12. The reactions of !. lucunter to a·horizontal . . beam of light(Experiment Two) ••• ~.o •••••• 73 13. The average rate of movementof 1. lucunter
(Experiment Two) •••• 0 ••••••••••••••• " ••• ". 74 14. T test appliedto data obtainedduring'Exper-
iment Three •.••••.••••••••• ~ •••••••• '. • • • • • • • 77 15. Experiment Four:. the orientation of !. 'lucunter during righting.movements •••••••••• .,...... 79' 16. ExperimentFour: the orientation of!. 1ucunter
," ., '. during wa1king movem~nts ••••• ·...... 80 Appendix A. Raw data: the growth of smal1 urchins.in an aquarium. • • • • •.• • • • • .. • • •• • • •• • • • • • • • • • • • •.• • 99 B. Seasonalvariation in gonad condition of Little·
Bay urchins •••••••••••••• ~ ••••••• '. • • • •• • • • 102 c. .Seasona1 variation in gonad condition of Graves End urchins...... 103
vi List of Tables èont1nuèd Table Page D. The rates of movement of individual urchins
during Experiment Two •••••••••••••••• ~ 104 ./ E. The individual ..a,~hesion periods of urchins ',.during ExpEj!riment Three.~...... 105 • • ' q • , • F. . Discrete groups a.rid group means .found in •. '. monthly >samples br using ·Hardingts(~949)
method of analysis •••••••••••••••••• ~ ••• ..' ' 106 .' Go Sizeclass (testle~gth)and lengthof spines· of Little Bay and Graves End urchins. •.••••.. 107
vii LIST OF ILLUSTRATIONS
Figure Page . 1. Photographs of collection locations at Little Bay and Graves End, Barbados, West Indies.. 16 2. The linear regression lines of log test volume 'on log test length 'for urchins collected " " in Jurle1966 •••• ~ • • • • • •• • • • • • • • • • •• • • • • • • • • 24 3. '" Length frequency distributions of Little Bay ',' urchinscollectedmonthly" October 1965 to Mareh,1966 ••• ~...... 26 ,4. ,L~ngthfrequencydistributions of Little Bay . . . ) - .
urchins co.llectedmonthlY li' April to ' ·September1966...... 27 '". "L~ngth frequency distriblltionsof 'Graves" End' urchins ,collectedmontply--October 1965
-- ' .'. ' . " ta ,March 1966~ •. ~ •• '. • •• • • •• • ... • • • • • • • • • • • • • • 28 . 6. 'Length frequency distributions of Graves End
,urchins "c()llected monthly. - ~pril to September 19660 •••• ·•••• '. • • .. .. • • • • • • • • • • • • •• • 29 . ,',. . " " " , ..., ., " -" 7., Mônthlyaverage'lengtbsof urchins atLittle Bay and Graves E,ndj' October 1965 to , September 1966 ••••••••• '. .. • •• • • • • •• • • • • • • •• • 30
viii List of Illustrations continued Figure Page 6. Monthly""average lengths of urchins collected October 1965 to September 1966. Harding's (1949) method of resolving polymodal fre quency distributions has been used...... 31 9. The growth of nine ,small urchina kept in an
aquarium. 00 '. 0.,.0 ••••• ' •••••••••••••••••• 0 • • • .33 '" ' 10. The seasonsl variation of gonad indices of Little Bay and Graves End urchins...... 34 11. Theseasonal variation' of gonad indices of male and female, urchins from Little Bay.... 35 12. The seasonal variation of go nad indices of
male and female urchins from Graves End ••• ~ '36 13. The percentage of ripe, unripe and spent
ur~ins ,from Little Bay and Graves End, October 1965 to September 1966...... 38 14. Mean spi ne length plotted,against mean test length of Little Bay and Graves End
'urchins ••• '••• , •••, ••••••• 0 •••••••••• '. • • • • • • • • 43 15. The linear regression lines of test thickness on test length, Little Bay and Graves
End urchins ••••••• ~'o '. ' •• ~; ••• ~'. '.~~ •••• 00. • • • • 45
ix List of Illustrations éàni1nùëd.
Figure Page
16. The linear regression lines of test height on test length, Little Bay and Graves End urchins...... 48 17. Height/length ratioplottedagainst lengthof
test, Little ,Bay and Graves End urchins~... 50 18. Apical system of Echinometra 1ucunter (after
r~cdonald (19,36), hisFigure 1)...... 51 19. Frequencydj.stributions of Mean number of pore
pairs, Little Bay and Graves End urchins o •• 55 20. The current pattern around Barbados" \'lest Indies (after Emery (1964) his Figure 7)... 6,3 21. The apparatus used for Experiment One •••• o...... 68 22. The apparatus usedfor Experiment '!'wo...... 71 2,3. The apparatus used for· Experiment Three...... 76
x - 1 -
INTRODUCTION
Echinometra lucunter (~innaeus) is a regular
. " . echinoid which is abundantin the West Ip.dies. Its . . . range.on the western Atlantic. coast stretches :trom Flor- - .~' . .ida and the Bermudas in the north to Desterra on the southeast .coast of Braz{l. Thisechinoid has beenre ported at Ascension, S"t. Helena' andalong the West African coast from Dakar to Angola (Mortensen, 1943). In aIl these.areas it is mainly a shallow-water (1-10 feet) form but may go down to 45 ineters (Koehler, 1908). Echinometra lucunter has been recordedin Barbados by Doderlein and Ha~:tmeyer (191~l, Clark (1919) and more recently by Lewis. (1960a). This species occurs in con siderable numbers around the coast of Barbados and is
mo~t abundant in areas of rock rubble or rock ledges. Occasionally an individual is found on living coral but never on areas of sandor mud bottom. Nutting (1919) reported Echinometra viridis from Barbados but only §. lucunter was listed by Clark(1921) from Nutting's collection. §. viridis was not found in Barbados during the present study. The species of Echin- ometra found in Barbados and used for this study was identified with the aid of the key of Mortensen (1943). The tridentate pedicellariae of the Barbados Echinometra - 2 -
species have only a small gap between the bottom of the hinged teeth as dothose of the form Mortensen ascribed
to E. lucunter (1943" Plate LXIV, Figures 7 and 22) ~ The,
. . . '. teeth of the tridentate pedi~ellariaeofE. viridis are separatedby a large gap and meet'onlyat thetips.Fon-
, >. - '. '. .: "'". '" •• ,": taine (1953) described that the east coast is continuously subjected to heavier wave action than the we·st· coast. ft The purpose of this study is to examine the gen eral biology of Echinometra 1ucunter and to discover whatintraspecific differences exist at the ecological 1evel:between two populations living in widely differ inghabitats. For the present study twocollection locations were selected: Little' Bay on the.exposed northeast coast of Barbados and Graves End on the she1- tered southwest coast. The data for this project were collect,ed in Barbados during the period September 1965 to September 1966. The field work was carried out at the Be11airs Research Institute of McGill'University in Barbados, West Indies under the supervision of Dr. John B. Lewis •. The analysis of the results was carried out in part at the Department of Zoology, McGill University, Montreal, Canada. ,:' - 4 - REVIEW OF THE LlTERATURE General !. lucunter has been used as an experimental animal for studies of the'physiological, cytological and biochemical development of urchin eggs. Studies on embryology and early development were reported by Tennent, Gardiner and Smith (1931), Miller and Smith (1931), Hayes (1934), Leitch (1936; 1937). These specialized reports are of intere'st to the student of deuterostome develop ment, but are not of particularrelevance to the pre sent study. In his voluminous work on the Echinoidea (1943), Mortensen described the distribution of the species E. lucunter, devised a key for identification and listed characteristics of the species. The habits and appear ance of Jamaican E. lucunter and !. viridis are detail ed by Fontaine (1953). E. lucunter is well known as a rock-boring echinoid. From a review of the literature on rock-borers Otter (1932) concluded that urchins indulge in burrowing only when natural crevices are absent and that this mode of 1ife is taken as protection ag.ainst wave action and dessic ation at low tide. Urchin burrows in the reefs off - 5 - Brazil were described by Branner (1904). One early author (Cai11iaud, 1856) actual1y described the rotary motion of the spines and teeth of a burrowing urchin. MeLe an (1964) conc1uded that the urchin burrows when it feeds, i.e. the teeth scrape up roc~ whi1e co11ecting encrusting b1ue green algae. These burrows, or depress ions, are then enlarged by physical processes invo1ving loose rocks, sand and wave action. McLean's study of !. 1ucunter faeca1 pellets revea1ed that a 30 mm long urchin i5 capable of removing 24 gram3'of beachrock per year •. He found E. 1ucunter to be "the Most important biological erosive agent o~ beachrock in Barbados." Other authors who have commented on the erosive ability of Echinometra lucunter.on intertidal shores include Crossland (1905), Umbgrove (1947), Kaye (1959) and Voss and Voss (1960). Four stages or 'steps' in the process of geograpbic speciation were illustrated using 16 genera of West Indian urehins (Mayr, 1954). Geographie speciation pro ceeds from one homogenous species to: 1) geographic variation within one species (Tripneustes at the present time) 2) geographic isolates within one species (Lytechinus at the present time) 3) allopatric populations which may be either species - 6 - or subspecies (i.e. Echinometra at the present time) 4) the occurrence of superspecies. This is a dynamic process which has been arbitrarily di vided into four stages for convenience. Mayr stated that the Genus Echinometra Gray is now at 'Step Three'. This genus consists of four rock-boring species (E. mathaei, E. insularis, ~. vanbrunti and E. lucunter) and one coral-dweller, !. viridis. All four rock-barers are allopatric and their distributions (Mayr's Figure 6) are an example of nperfect geographic speciation". Two of the five species exist sympatrically: E. viridis lives on coral reefs and coexists with E. lucunter in a small part of the latter's range. E. viridis has adopted a different mode of life and is not in competition with E. lucunter. Mayr noteè especially the wide variation within the species E. lucunter over its range. He considered that variants arising out of adaptation to local envir onments in shallow and deepwater members of a species (vertical variation) do not lead to speciation but geographical variation (horizontal variation) does lead to speciation. Mayr concluded that If the pre vailing speciation pro cess in sexually reproducing marine animals,is that of geographic variation." This view is supported by Mayr's review of the work of other - 7 - authors on distribution of marine species. Breeding of Echinoids Lewis (1960a) reported that the breeding period of !. lucunter lasted from May unti1 August in Barbados. He also studied (1958) the breeding cycle of the Barbados sea-egg j Tripneustes esculentus ( = ventricosus). Dur ing the latter study, Lewis analysed the incrcase and decrease of gonad volumes over a three year periode Tripneustes and Echinometra spawned only in March and .April in the West Indies according to Mortensen (1921), but Lewis found that Tripneustes began to spawn in May and ended in 'August for three years in Barbados. During one year the gonads maintained peak values from March to August. Moore ~.!! (196,3a) also studied the reproductive cycle of ·Tripneustes in Florida and noted spawning in the spring and summer. The time of release of gametes varied in the different years andthey concluded that this was a result of the triggering of spawning by temperature. They found gonads steadily developing reproductive products and becoming ... increasingly recepti ve to a triggering stimulus (i.e. temperature). After a critical point had been reached, the urchin grew more - 8 - receptive to the stimulus as the threshold was lowered. The reproductive cycles of several species of Strongylocentrotus are well known, especially those species occurring along the coast of California. Bennett and Giese (1955) reported that two species of Strongylocentrotus have annu al reproductive cycles. Boolootian and Giese (1959) found no latitudinal effect (within 11 degrees of latitude) on the breeding cycle of ~. purpuratus. Sufficient work has been done on the reproductive physiology of S. purpuratus to "suggest that endogenous factor(s) may influence, control, or regulate reproductivitylf (Boolootian, 1966). The re productive cycle he studied was remarkably similar in two populations of S. purpuratus living in water masses of different temperature. However, the duration of spawning was longer in the warmer site. Growth of Echinoids Mortensen (1921) has ~escribed the developmental stages of the 19 day larval life of 1. lucunter. His plutei larvae were obtained in Tobago, West Indies. Moore (1935) studied Echinus esculentus in three different environments in the North Atlantic near the - 9 - Isle of Man. He established age classes by means of growth rings on the genital plates. No similar growth rings were found in Echinometra lucunter in the present study. Many echinoidspecies have had approximate yearly growth rates established by researchers o Among these are Echinus esculentus (Moore, 1935), Lytechinus varie gatus (Moore ~ !l, 1963b), Tripneust~s ventricosus (Lewis, 1958; MCPherson, 1965), Hemicentrotus pulcher rimus (Fuji, 1963) and Strongylocentrotus droebachiensis (Swan, 1961). Table 1 lists the species, comparative growth rates and sources of the above material. Lewis (1958) in Barbados and McPherson (1965) in Florida reported different rates of growth for Trip- . neustes,ventricosus. The specimens Lewis studied grew 50 to 80 mm in the first year while those McPherson measured took two years to reach a length of 75 mm. Several authors have observed the growth of echinoids in laboratory conditions, such as Arbacia and Psammechinus {Bull, 1938}, but no work has been done on the growth of !. lucunter. Moore (1936) was able to distinguish year classes of Echinocardium cordatum by the different colour of their tests. Swan (1958) found class-specifie variation of characters between four age classes of Strongylocentrotus. Age classes could be determined not only by length but - 10 - TABLE 1 Information on growth ratës of echinoids gathered from the 1itera1:;ure. Species Size Age Source Area (mm) (years) Echinus escu1entus Moore (1935) North Sea Chicken area 70 7 Breast area 90 6-7 Breakwater 100 6, Hemicentrotus 10-11 0.5 Fuji (1963) Japan J2u1cherrimus 20-22 1.5 27-29 2.5 32-35 3.5 L~techinus 40 1.0 Moore et al F10rida variegatus (1963b) TriJ2neustes 50-80 1.0 Le'wis Barbados ventricosus (1958) Tri!J2neust~s 75 2.0 McPherson F10rida ventricosus (1965) Strongylocentrotus 1 .08 Swan New England droebachiensis 8-10 1.0 (1961 ) 24-26 2.0 40-42 3.0 46-54 4.0 - 11 - also bythe relationship of test height to test dia meter, test diameter .tolog testweight,mean number of coronal plates perrow and.number of wedges in the spine. C«?mparative'Studiesof Echinoids Sharp and Gray (19.62) reportedapparently minor behavioural differences between Lytechinus variegatus and Arbacia punctulata. These·differences affected the local distrlbutionofthe species~. On~specieswas better able, to hold on to a substrate with its tube feet and· as a consequence was successful in staying on concrete piles or rocks while the other species was confined to the bottom. Moore (~934;1935; 1937) found that wave action, available food and other factors imposed differences between three groups of Echinus in,colour, . shape, test thickness and breeding cycle. Buchanan (1966) reported similar differences in a littoral and an offshore population of Echinocardium cordatum. He concluded that the littoral population was four times as productive as the offshore population. The littoral ·population reached maturity in three years and grew 8 mm per year while the offshore population did - 12 - ~,,~i,~,:,' W not reach maturity in 7 years and grew 3 mm per yearo Stevenson and Ufret (1966) compared the feeding habits and chemical composition of the tests of !. la cunter and Tripneustes esculentus at two locations. Theydiscovered'thàt the,two species have significantly diffe~ent amount~of metallic substances in their tests but the amount of metals, in the test of the same species did not differ between the two locations. Hagstrom and Lonning (1964) studied morphologieal variation in Echinus esculentus in a Norwegian fjord. One group had an Aristotle's lantern twice as large as the lantern of the other group at a comparable test size. They deduced that this was caused by the pr~senee in the population of a larg~ number of 'fertile hybrids of E. acutus and !. esculentus. These hybrids evident ly had a larger lantern than the individuals of either of the parent;,; species. In a previous paper (Hagstrom and Lonning, 1961) the authors have established signi ficant variation within species of morphologics! char acters used by Mortensen to distinguish !. acutus from !. esculentus. They'proved also that 10 to 20 % cif the Echinus population in their area are fertile adult . ~ , hybrids of the two species and show intermediate species characters. It is thus of especial interest to determine the reliability of the morphological characters used to - 13 - define the species Echinometra lucunter. f Behaviour of Echinoids A nlunber of experiments have been reported on the reaction of regular echinoids to stimuli. Parker (1922) studied the geotrophic response of the 10ng-spined s"ea.;.egg; Centrechinus. Phototaxis wasthe subject of HOlme's work (1912) on Arbacia punctulata. The studies o~ Millott (1952; 1953; 1959; 1963) have provided a wealth of information on the light reactions and nervous . '. system of Diadema.~ill~. He investigated the re- lationship of reaction to light and the epidermal and radial nervQus system. Macdonald (1936) studied the walking and righting movements of Lytechinus variegatus in.detailin an attempt to prove that bilateral symmetry is inherited in aIl ·regular echinoids: a symmetry which 1s functional and structural. '~ Loven (1892, quote~ in Macdonald, 1936) wrote of a system presently used to describe the symmetry of the echinoids. Macdonald made "observations" on Echinometra lucunter as weIl as five other species of echinoids and found that "Echinometra is elliptical through the I,3 - 14 - axis, but from observations on its wa1king and righting movements, it is definite1y functiona11y bi1at~ra11y symmetrical about Lov~nts axis" (i.e. III,5)0 The forward movement of Echinometra lucunter is described by Macdonald (1936): "an ambulacral area with the tube feet extended 1eads, and the principal forward propulsion is provided by.the spines on either side, which move in a rowing arc." Jackson (1912) found that during the deve10pment of the coronal system of the regular echinoids the ocu lar plates are ~nserted in the periproct in a way which emphasizes the bi1atera1 symmetry of the sea urchin (i.e. along the II1,5 axis). Part l GROWTH, BREEDING and COMPARATIVE STUDIES - 15 ... MATERIALS AND METHODS Random samplesof approximately one hundred urchins were collected at monthly intervals trom the two shallow-water ~reas, Little Bay and Gr~ves End. The . ." ,", specimens were bl'ought to the laboratory:in large buckets filled with sea water (one~half hour in transit) and placed in concrete sea water tables supplied with running sea water. At .. Little. Bay the urchins inhabit the "surf(zone" and the lower part of the adjacent pink zone. The, surf zone is described by Lewis (1960a) as being "a relatively narrow band lying from the mean low l'later mark to approx imately mean low water springs." The urèhins are either immersed in water or continually wasbed bywaves except during a few very low tides each year. There ia no sim ilar rocky surf zone at Graves End. The urchins live slightly above the mean low water level. Photographs of the two areas areshown in Figure 1. At Little Bay the land ends in a cliff which 1s 15 to 40 feet high. At the bottom of this cliff is a'ledge which is exposed at low tide and continually washed with waves except at low spring tides. The urchins live in cre vices and tide pools at the edge of this platform.The area is very similar to the cliff station in River B~y West described by Lewis (l960a). - 16 - FIGURE 1. Photographs of collection locations at Little Bay (A) and Graves End (B), Barbados, West Indies. 1 - 16a - r, B B FIGURE 1. (continued) - 17 - The Graves ,End locationis a beach area. The .first 90 feet of sandy bottom support, an" eel grass (Thalassia testudinumKon1g)" community. "The urchi~s' were collected 100 to 130 feeto.ffshore in an'area :'of rubble rock. The depth ofthe,water inthe:rubble'area, . . .. "' .' , at low tide var1ed trom 0 to 12 inches.D.R.Moo~e'(1963) , ", . in bis study of the distribu~lLon of'Thalassia:.inthe, ," . . '. . . . southern United States, describedtheenvironmentaf-:c~:)D- diti0l?-s essential for, this type of alga. 'Oile of hi~. , , , conclusions was that "the presence ofgrassbedsinoff shb're waters depends on reduced wave action. This occurs where reefsbreak up oceanic waves, orwherethe config uration o~ the bottom and coastline reduces the stre~th of waves t'lmle still some distance off, shore ~ If The extensive and successful Thalassia communityat Graves End 1s an additional factor which indicates reduced, wave action in that area. From the collected specimens the "followingmea- ' surements were taken with pointed-end calipers in ,the ambitalregion of the test between the'spines: length, width and height (distance from buccal membrane toapical system). Measurements were made ta the,' nearest mm. Each urchi~ was then placed in an overflow vesselfilled With sea water and the urchin's live volume (with spines) '"las calculated from the amount of water displaced. Measurements - 18. .;... of v91ume weremade to the nearest 0.1 cc. The 59 large st urchinsfrom each site wereretain.. ed forgonad examinations. .The . gonadswere examined . immèdia~ely tifter the test ·meEAsure~entswere.taken.· 'G<)~aclrCo!ldi tion was .'. estimated bymicroscope. examinatio:q~<·· , . . '. . - .' . .' . .. .' " ;.' . . . .",.. '. ~ . "...... ' ...... ~:r;a gOll.ads.8mpl~ smeared'~nasli(if3.(Moore, ,i9~4f •...... ,A11·urChin~~exanti.nèd·.'Sllowed, ". eviden~e' of h~virig·.b~ed·'· befor~. . Thusa .shrunkengonad·wasaninciic.ationtha1;· : th~.urchi.n l'las···· spe~t .' andll~t;i.Iri~àt~re~ ····.·.:TheriP~:gona4s . :,.' . '. ofboth sexes ranfreely whenbr()ken'and' thiswas aIse>.·· .... used as a',guide . 'to 'e~tima~irig: ripelless •. . .. . Ur.chins ~ëreclassiiieda$rnale:or.femaie and-' .. ·.·ripe, unr~pe oriapen~.· ,'~hë :fOllowing:condi't1oll~ 'l1~re iloted: . '" .,':-.- ". " '<,: • ",o' - Fem~le: . rip~ -presenc:e' of ovaOf',:WhiCh:·at:ieast.~510 l. .. :' ," .. ' ..': .. t095%. are. ripe, .gonadswoilenit .. ... ,- '. nearly ripe-swollen . ' . . . . Male: . ripé. - swollèn'gonads, presence of many active' sperme ' . .'. 'neàrly'ripe'-1argegonad~ presence of active sperme partially spent . "';· .. shrinking gonad J some live sperm present. , . nearly spent - small gonad, few live sperm present. ,spent - no active sperm,shrunken gonad.' Gonad volumes l'lere calculated by the displacement' method.Two of thefive gonads of each urchin weré· placed in a graduatedcylinder whosewater level had already been '. not~à. The total gonad volume l'las calcul- atedon the assumptionthat the twogonads measured con stituted approximately two-fifths of the total volùme of' all five gonads. Measurements were made to the nearest 0.1 c~. A 'gonad index is expressed as a ratio:,o:f te~ t;mes the actual totalgonad volume (G.'V.) of' each :', - urchinto the live test volume (T.V.) of that urc~~, i.e. gonad index = '10' G. V. ' T.V. This index is used in order to facilitate the comparison - 20 - of gonad volumes of mature urchinsof different sizes (Moore, 19.34). The colour of .the spines and test ofeach urchin frommonthly collections was also noted •. Four predom inant colours were.present, red, black, brown and green. It was. thus possible to analysecolour variations using , a standard four by four table (Ferguson, 1966). :i:n January, February,March, April and May +966 20 additional urchins per month were collectedfrom Little Bay andfrom Graves End. Theseanimalswere put . . . . into a solution of laundrybleacn (approximately 5~25% sodium hypochlorite) until the spines fellaway from the test. Length, lrIidth and height of the bared' test were then measured. The apical system of each test was examined to determine which ocular plates were inserted into the periproct. All ambulacral plates on the ambitus of every urchin were examined and the nlunber of pore pairs on each plate counted. Thus, 10 arcs of pores were count ed in each urchin. An interambulacral plate was select ad from the ambitus of interampulacra 3 (Lovén's syst~m) and the thickness of this plate was measured at the suture of the interambulacr~l plates. This measurement was taken under a microscope with a micrometer eyepiece. The test thickness was measured to the nearest 0.1 mm. One 21 spine was taken f'rom the.same position. on e~ery inter ambulacral ambita1 region of each urcllin(five primary spines) and a meanlength of' spine was,calculated for each urchin. Nina small urchins (3 to 8 mm in length) were kept in a gl~ss ~quariwnwithrunning·seawater·from , . , . . . 27 November,1965unt11·11 June 1966. Tneyweremeasur- ed periodically \dththe'.aid ot·a microscope and micro- . meter eyepiece. '. These smallurchinsgrazed on algal growth on thesides of the aquarium, small f'resh rocks which were periodica11ychanged and occasionally a frag-· ment' of' snail, 1impet or fish was put into the tank. TWo urchins died, one in.Janu~y and on~ in April. Their testswere removed f'romthe aquarium,spines mea sured and.an ambu1acral pore pair count made to insure' that the urchin was Echinometra 1ucunter. The other 7 " urchins survived until 11 June'1966 when all werelost accidentally. - 22 - RESULTS' Growth Studieson,the growth rates of regular echinoids ,'were 'sUmmarized "in the 'Introduction"of 'the, .présent 'study. Several oftlle' authors mentioned used, ,ambital' test; dia meter as a parameter of size (Lewis, 1958; Moore, 1934; Swan, 1961). ~. lucunter is not circular but elliptical <-' in,shape, thus,the diameter, of the test cannot be mea- sured directly but an equivalentparameter, can be -calcul ,ated from length and width me àsurements • In the present studytestlength along,theelliptical axis (Lov~nts . ' axisI,3) 1s used asa ëriterio~ofsize.' In order to . . '. , justify using testlength asa primàry parameter in this study, the co'rrelation coefficie,ntsof 'testlength and test width,lengthand height,and length,andvolume were calcu~ated. Table 2 lists the correlation coef- ',- . ficients of these measurements., Test length is highly correlated withtest width,height and live volume and its use as a measureof size is thus justified. Figure 2 'shows the regression lines of the log arithm oftestvolume,on'logarithmof test length at Little Bay and Graves End. The difference in the slopes of the two regression lines May partially be explained - 23 - ;) V TABLE 2 The correlation of width, height and volume to length in urchinsfrom Little. Bay and Graves End (see text). Measurements Correlation coefficients Little Bay Graves End length & width 0.95 0.97 length & height 0.86· 0.89 length & volume* 1.009 0.87 * this is an exponential relationship. Logarithms of measurements were used in calculation of correlation coefficient. , , - 24 - LITTLE BAY GRAVES END ) 100 1 ,1 ,-... u u ~ w 2: 1 ::> --1 0 . > " . 1 , 1 80 1 100 " .' LENGTH' (mm)" Little· Bay" l~g.l =.2.75 log X - 0.2.34- . . ~ '. . . Graves End, ',iog y ,= 2.22 log X+ 0.042 .,; , , FIGURE 2'. The lirieàr' regres·sion. lines of log test " \.. volume on log testlength for ur~hins collected at ~ , , Little Bay and Graves End, June 1966. . , .. - 25 - by the facts that urchins from Little Bay have longer spines than those from Graves End and that urchins from Little Bay are shorter per unit length than those from Graves End. The results of growth studies are summarized. in . Figures 3 to 7. In the monthlycollectionsfrom Little Bay, urchins, ranged in test length from 8 to 47 mm •.. Urchins measuring up to 70 mm in lengthwere foundat Graves End, those over 47 mm in lengthbeing 15%· (range = 2 %ta 37 %) of total èollectionsthere. Specimens of more than 4 romand less thanlO mm· in length were found at both locations only during June to August 1966. The monthly length distribution express ed as percentage of total collection is plotted in Figures 3 and 4 for Little Bay and Figures 5 and 6 for Graves End. The monthly Mean urchin lengths for each area are shown in Figure 7. Data on length of urchins collected for 12 months from Little Bay and Graves End were analysed to ascertain whether the length frequency distribution for each month was polymodal and thus indicated two or more age groups in any monthly sample. Two distinct groups were obtain ed in six samples. The samples and group means are illus trated in Figure 8. Harding!s (1949) method of resolving polymodal frequency distributions was used. ...; 26 25°/0 October '65' 'OL-~~~~ __+--+ __ +--+~*--+ __~-+ 10 30 40 50 60 \ LE~~.TH (mm) \ .. FIG:tJRE,3. ,Lengtll frequency distribut;lQns of Little Bay ,uréhinsco1;Le'cted mOIlthly, October 1965 to March \ ' 1966. ,Measurements are grouped into 5 mm 1ength classes. - 27 - :;:;; ['9:~(~. sOr " ~. 2.5' J. September '66 0 2S . AuguSt li) \ C ,25 July 0 _ -tJ U Q) " -0 u June U \4- 0 0 25" May ---0 25 ·April .10 . 20 30 40 50 60 " ., .. LENGTH (nim) FIGURE 4. Length fr~quèncy. distributions of L1ttl~' Bay .. urcltins' collected wonthlY. April. to September 1966. Length.measuremerits are grouped into 5 mm classes. 11 : .. " ' .\. -28 - D 50% \ .. . 25"% March 0 Z5% .February (/') s:: 0 +' Z5 January u '66 (J) 0 U 25 \f- 0 0 \ 0- 1 Z'5~ \ 1, October ' 65 10 .20 30 40 50 60 . LENGTH (mm) '/ FIGURE 5. Len~h frequèncy' distributions of Graves End 'urchins co11ected monthly, October 1965 to March 1966. Length measurements are grouped into 5 mm, classes. . .. . _- --",--- ... _-~ - 29 - f9 50 2S' September '66 0 25' August (/) c 0 2~ . ,1 ...., July u (l) 0 U 25' \t- 0 0 .:2S' ---0 .1 April 1 O-'-~-f---i-==::t::::==t====~-4--i--'-'-I--+--~~~~ 10· . '20 30 40 50 , . LENGTH . (mm) .. , ·i FIGURE 6. Length frequency ,distributions of Graves End . 1,U'chinscollected monthly,~April 1966to Septem-. ber 1966~ Length measurements are grou~e~ into' .5 mm classes. \. ... ._ ...... _.. ... - ~ ... -... "_.---;-- - "'--"--"7'-_.",',":--;----' --.----~-;--:. _--. .-.~-. ------. __ .----- _--_. __ ._ ---_.- .. :_--_.~\ _._-_. ---- '\.;,;;;/ , , , , .:~. . :. ':. '- .•'j-- 'x = Graves End o = Little,Bay t 50 E ,x.. '- " " ..... "....." ' ' .c - 40 '1t: ".....'.)C-----x-- ' _--x----x ... - --~" +-'rn c ~?-=-o (» 30 +-' tI) .' FIGURE 7.. Monthly average lengths ~f urchins .coilèctedatLittlé Bàyand ",- Graves End trom Oétober 196;to' .sePte~~er 1966.--' ' - -,; . ,,';' ' ',' ./ ,/ . ;:., .' ~ . , o = Little Bay x = Graves End . 50 ,,;x..... E ..... ,"" ' _'V___ E 40 ~ 'x----~.---x-'-- '" -x----x...... - ,.v ...... /'0___.. ----0-- .. ____. 0-0 ____ . .- ...... x----x--_ -x',,""" 0--- " ~-o 0 :5 30 0 rn \.t.) c .... (JJ 20 o _x . " ...... x- ___v,--:- .... c ~, X'''. .' .... ~ . a 10 (JJ E 0' 1. o N· D J F· M A M J J A s month of collectron FIGURE 8. Monthly average lengths of .Urch1ns collectedat ~~tle ~ayand G~aves End .:t'rom October 1965 to Septe.mber19~6~ .' Results obtained _____------·us:i.~g Harding.ts (1949) method of resolvlngpolymodal frequency . ... - distributions (seeTable F,Appendix). - 32 - ) The gro\'lth o:f the 9 small urchins kept in an aquarium is recorded in Figure 9. Little or no growth was recorded Erom November to February and thereaEter the growthrate is 60 to 66 %oE test length per month (--' 1.5 mm permonth) • When theexperiment was termin- . . ated on 11 June 1966 the small urcbins ranged in length from 7 to 13 DDIl. The urehins studied in the aquarium reached,the length oE 10 mm in May and June 1966~Urcbins oE 10 nnn length Eirstappearedinmonthly collections at Graves End and Little Bay in May and June 1966. No inEormation is available on the growth rate of'. small urcbins in the Eield. Breeding The results of analysis.of seasonal changes in gonads are shown as average gonad indices from both areas in Figures 10, 11 and 12. The average monthly gonad index of urchins Erom Little Bay rose steadily from October 1965 until August 1966 whe.n spawning occurred. The monthly gonad index of urchins from Graves End was at a peak in November 1965, Eell to a minimum value in February 1966 and rose toa second peak 1 • - 33 - 14 12 10 6 ~ '" 4 -E 2 ...... E 0 I ..... r- <.9 . 12 . z w 10 ---1 _--x r- 8 -- li> ---- o W r- 4 c ~ =- 2 ...... ~. 0 50 100 150 200 TIME IN DAYS FIGURE 9. The growth of nine small urchins kept in an 1 aquarium fram 27 November 1965 to June 1966. SEle Table A, Appendix • . \ \" ....; ''''';'J ~ 2.0T 0 ~ Little Bay ,/ x = Gr~vesEnd // 1.5 gonàd index 1.0 --x~_x ~1' ~ 1 : K \IJ ." o/~~O . ~ .. o 0.5 o~~ cf ., )" \:.~ o Oct Nov Dec J"a.n Feb May H,,~ f\1a.~ :rune. j-u.l~ RIAS Sept .. month of collection· ,FIGURE 10. The seasonal variation in the volume o~ the gonads o~ urchins from Little Bay and Graves End, 1965-66. Ali gonad volumes are expressed as gonad indices· (see text). , v 2.0 1 x = male /' o =. female /' 1.5 / 1 1 1 ~ "x u ",' c 1.0 . - 0 TI . ~...... ~x/ o~~><- \.oJ o J(~ . . \Jl c o CJ) o~. ///0 - 0.5 x- . . /.. - ~~~ - ., ) ., \~,. -0 o N DJ -F M A M J J A s ... month of collection FIGURE 11. The seasonal variation in .the volume of thegonads of male and female urchins from Little Bay, 1965-66. - All gonadvo;Lumes are expressed as gonad indices (see text). V· , -_:...------ 2.0 . x= male o =f'emale- 1.5 , , x----x'\ . ~ . , ~. '" . " - • /l--"""-a 1.0 O-,---O~ ___ \ ;;~/ --X--.___ '\\\ ~ TI O~\ - ".... 'tx----YI . . \, C ~~ - \ ~ \ 0 • / \0 ~ \. / ~ " \ / ,.. TI . 'x'- o c 0.5 o rn o ' 1 1 ", 1 1 1 1 1 1 1 r , o N D JF M'A ·MJJ A S month of collection . FIGUREI2.· The seasonal- vari~tion in the volume of' the gonads of' male and -'f'einale -urchin~'f'rom Graves ·.End,l965-66 .Allgonadvolumes.are expressed as gonad . . . . , . ., indices (sëe text). - \ - 37 - in July 1966. The go nad indices of Graves End did not fall as low as thosefrom Little Bay •. .,' ", . ", , ". . . l haveassumedthatthe reduct:tonof gonad vol~,' umes and hence gonad indices,isd~e torelease'ofgam~ ; .' . etes and not depletiC)n of food reserves. ,The gonad may, serve a double role, reproduction and foodstorage. Lawrence ,and Lawrence (unpublished,Bool~otian1966) and Caullery (1925)found gonad shrinkage 'after uréhins were starved in the laboratory for a ,period of more than six weeks. It is unlikely that E. lucunter would face periods of starvation' in,natural conditions. The results of analyses based on thedegree:of ripeness of the gonads are shown in Figure'13. For"the three month period of October,'Novèmber and December 1965, 80 to 95 % of the gonads observed 'from Graves End . were ripe or unripe (developing) while only 40 % of thosetaken from Little Bay were in thesame condition. Gonad analyses from Little Bay and Graves End in June 1966 show the,same trends. In both areas 50% of the males were ready,to spawn in June. Fifty percent of the females were ripe br July. ' ... ' \ ' \ 'C' ;0 ,: otJ, "/00 A',' ','. LITTLE BAY "u, V' ",', ,0 "80 ',U , spent "- " ", ,60 0' .:: :,',': "r'',' p 'e' ', ..: ~ .::' '::.:,:' t •• '. '. ~ • . '. 'O:' " •• : • • 'f •••••••• "~'.', • ~ •• ~'. :,-:.:: =...... :~'; , 40 ..... " " ...... "'- • ~ • • •• • '" • •• • • .'. '•••••• ' ~ l' 1 ••• o ••• 0" •••.••••• '. , ••.••• • Il .: 0,':,'. ',' Il, ,: :.' : .... ,f •• ", •. '.' "1 • <1.> • • '.' ., •••••' •••••••••• Il •••• 'u ~...:...:..~~-~ ...... ,. L 20 unr ipe . Cl.> 0. o~ __~ __~~ __~ __~ __~+- __-+ ______~~ __~~~ Ott ' NDV bec. Fe.h 1'10.". Il;;,,, l1afj J'une 'jul'J" Ru.t) Sept B GRAVES END c 100 0 ~ U (l) , spent 0 u (, "- 0 0 '0- 20'~-..:J unripe " Oct . Nov ·Dec. JCltn Feb ,Ma.... Apl' ,/y1Q~.' J'lAne Jltll{ I114S. Sept month of collection " FIGURE 13. The percent age (if ripe,' unripe and spe'nt ~chin' gOlrlads from, Little Bày and Graves End, October 1965- , SeF>tember 1966. - 39 - Comparative Studies .,", '; \ ,: . The resultsof analyses, ofcoloùr differellc~'s are' . presentedin Tables J and 4. 'Tlie d~tahave.~eeni~rië.l'YSed:: .,', .: ...... :. :'.' .:: :" ,:', lly,application ofthEr :~hi-sql1aretest. ,The, col~ûr,:difi~, • , ' 'erences were f'ound to besign1ficant· at, the P(O.OOl ' ',levf3l. The group,percentage coloUrsin,both locations . are ,listed in Table 5. ' , . Most of the urchinsfromLittle Bayh~ve,ablack test andblack-spines or redtest andbrownspines. "Those from Graves End tend to beBlore varied,'tllemajor- ' :1.tYhave red tests and brownspin~s; a considerable number have redtests and'red or green spineso Six small aquarium'urchins were completely black . , , in colour and three had gr~en tests and violet~pines wi th white tips. By themiddle of March the colour of ' , all, s~vi ving experimental urchins( seven} had" cha~ged to reddish test and reddish brown spines. The raw data compiled in this study,of smallurchins islistedin Table A (Appendix). Urchins from Little Bay have longer spines, in,:, relation to test length, thanthose froBl'Gr~vesEnd (Figure 14). Urchins were grouped into 5 .. ,mm·test ... length groups. The mean spine lengthofL~ttle Bay group X w~s compared with.the mean spine length of the Graves - 40- .. '. :',' .....: .. " . ' . ' ....., ':,., :.: ' .. ' .. .: :" ' .... ' ...•.. '. ·TABLE~r········ . ',.. ,,:" ", ,:",., ; ; ",' .,- , . " .. \:, ". " ',. ': .. . ,' : " ,,'; " . . ,:, ':" ',' .. " " . .: 1105 Littie Bayurchins. ··Data .' . , ..... ""', .:'. "",' . " ... wero collectèd.overa. per:tod of . .' one·year. ======---- ...... Test co1our' 'Spine colour .' . . red:' black' . brown green ··tota1 • '·.... 1.· -.,.. • red ':39 155- 334 23 551 '. black .. . - 0 '523. 2 2 ;27. brown 0 2 23 l 26 . green 1 0 0 0 1· total 40 680 359, 26 1105 degrees of freedom = 9 X2 =:618.73 . p < 0.b01 - 41 - . TABLE 4' ·.The spine and .. te st colollr;Lngof • . .... : •. ·1116,GravesErid.. ~chins. .' Data ."we~~ 'col1eèted o~er a p~riod of one year. 'Test .colour . Spi.ne colour .red. black .·brown green . total . red·· 124 " .123 . 388 178 813 - 1 black 0 213 2 8 ,.22)' brown 0 2 51 10 63< green 0 4 13 17 total 124 338 445 209 1116' degreesof freedom = 9 X2 =62ge36 . . . p (. 0.001 . - 42 - D .TABLE 5 The spine and test·colouring of Graves· End and Little Bayurchins.· Figures are . expressed. aspercentages. Little Bay Test colour ·Spine colour red black brown green red 3 14 30 2 black a 47 (0.1 (0.1 brown 0 <0.1 2 (0.1 green (0.1 0 a 0 Graves End Testco1our Spine col our·. red black brown green red 11 11 34 15 black 0 19 <0.1 <0.1 brown 0 (0.1 4 <0.1 green a a <0.1 l - 43 - ) ...... E . E30 -.. ' .c -tJ 0) C" i . , '. . .," FIGURE 14. Mean spine length plotted against mean test length ofurchins from Graves End and .LittleBay. Data grouped into 5 mmlength classes (see text and Table G, Appendix)o . - 44 - End group X. T tests were applied to the data to obtain signifi.cance levels. Arrows in Figure 14 indicate groups found to be significantly different at the P <0.05 level of confidence. Thelinear relationship of test thicknes:a to test length of Little Bay and Graves Endurchinsis shown as a reg~éssion.line in Figure 15. 'Analysis of covariance . -, , tests' àppliedtothis data. show that.theurchins from , , ' . Little Bay (N= 101) have athi~ker test in're1ationto , . test length. than ,those from Graves End (N= 10,3). A, significance level ofO.Olwas usedas acriterionin , testing the~eans and regressionline .slopes of any two groups. The slopes of the regression lines were not , ' , , ,significantly different." Themeans were, significant1y different in thebetween-groupstest. The results of , , ' analysis of covariance tests are listed in Table 6 (method used, Ferguson, 1966). Analysifjlof covariance ,tests were also used to interpret the relationship of testheight t() test length of urchins. Urchins from Graves End are taller per unit length than those of Little Bay (Table 7). The mean test heights of Little Bay' and Graves End urchins are signif'icantly different at the 0.01 levêlof confidence. The slopes of the resulting regression lines are not significantly different. Figure 16 shows the regression .' \ . - 45 - \, " \ ...... = Little : .. Bay:: ... .'. x·~·G·rdV·es·End 1.0 . :. '.' '.' ....'- E.8 . ...... ,.E ..... ~. ":. (J)' .. '...... '.V> . .' .. •'. zw .. •6 . ~ U' I· r- r- .4 "V> W .'1- . •2 o . 10 . 20 30 40 50 .: LENGT H (mm) :Litt1e ..'Bay X = 0.016Y + 0.20 Graves'End X= 0.015Y + 0.17 FIGURE 15. The 1inear regression ~f test thickness on test iength. Data fro~ Little Bay and Graves 'End, January .to May 1966. -46 - Groups Tested Significant Significant difference, difference, group means regression line slopes Little Bay> vs Graves End 0.01 , (all specimens) Little Bay vs Little Bay JanuaryvsFebruary 'O~Ol Februaryvs March" ,Màrch vs· April - "April vs May', Graves End vs Graves End JanuaryvsFebruary February vs March 0.01 March vs April April vs May TABLE 6. The results obtained from analyses of covariance of test thickness to test length of Little Bay and Graves End urchins. Over 190',~:, individuals taken from each location. See texte - 47 - ~ V Groups Tested Significant Significant difference, difference, group means regression line slopes Little Bay vs Graves End (all specimens) 0.01 Little Bay vs Little Bay January vs February February vs March March vs April April vs May Graves End vs Graves End January vs February February vs March March vs April April vs May TABLE 7. Analyses of covariance of test height to test length of Little Bay and Graves End urchins. - 48 - 35 • = Little Bay 30 )( = 'Graves End 25 ~ " 20 E :/,; '-" J- 15 I li) w 10 . :c '5 o 5, 10 15 20 25' 30 35 40 45 50 LENGTH (mm) ...... ·Lit,tl~ Bay" ·X"=O.54Y - 2.0, , Graves End X' 0::. O.57Y - ~. 7 .' , ' .... ': ...... ; FIGURE 16. ' Theiinear regre~sion of test, height on test.léngth. . , . . ,'" ...... - . Data, fram Little, Bay and Graves End, 'Jan~a.ri t'ô'May 1966. ,', . i : ;::;; J / . •••• f '. .' -;------; "--. -.• _--~ ... _--: --'-'-r.-;-.---·~·; ~-:--."-'-"--;--:a.~',----.------:-;-."':--'- --_ .... -. ·.' __ '.N ____ .•' __ •• _ ._ ..•. - ..• -. '-_0-'_- - . - ._0' .., ':--: •. - . --_...... - ""'-_._---.----... -~.-- - 49 - lines of height on length for the above data. Figure 17 shows the relationship of the height/ length ratio to length. In both areas height accounts for an increasingly larger portion of the height/length ratio as the test length increases. Figuré 18 is a rep~esentative drawing of the "apical system of an urchi~ with theocular and apical plates'numbered according to Loven'slit' system. Ocular plates become inserted in the periproct during the 1 cour~e of morphological development in a manner which emphasizes the urchin 's bilateral symmetry "(Jackson, 1912). Table 8 lists the kind and number of oculars foun~.. insert in the examination of 101 urchins from, Little Bay and l02"urchins from Graves End. Table 9 lists the percentage of oculars insert found by Jackson (19l2), in Bermuda and the West Indies. Chi-square tests have been applied to the datacontained in Tables 8 and 9. Ocular insertion is significantly different at the 0.001 level in the two populations studied. It is highly varièble among the members of ,one population. Morten sen (1943) stated that ocular IV and sometimes ocular V are inserted in the periproct in E. lucunter and all oculrrs exsert in E. viridis. The present study proves that ocular insert is not a species-limited character \ as Mortensen implied and should not be used to distinguish -.;.;.;/ ------;-- - . /x(6) ~58 / . ~.---.:t/" " 054 . "" "",*," 0 )1::''''' r- ,/' « . " n::: ./"- .... -~ .50 ., I r- ,/' <.9 ... ,~;f z *,' • = Litt le Bay \J'lo w '~' 146 /' .. x= Graves· End --1 / ~r- / ( )= less thon 20 urchins I· ,1 <.9. 1 1 .42 1 w 1 I 1 1 1 1 1 ~(5) .38 10 20 30 40 50 60· 70 . LENGTH(mm) FIGURE 17. Height/length ratio:: 'plotted against .~;test length. Data f'rom all urchins ·éollected f'rom Little Bay and Graves End, 1965-66. \ - 51 - \ A\ ~. , \ A = axis,along whiçh ùrqhin"is elliptical '" "" " B = preferred axis of movement FIGURE la. "Apical system 2f. Echinometralucunter. ", Genital plateswith Arab~c numbers', ocular plates with Roman numerals. (After Macdonald (1936), his Figure 1). 'TABLE' 8 · , ' ' Plitt·erris''Of.'ocUlarpl~te,ins~rti~ll, . " ~ ..... ,/ . '(' i6undfrÎ' urchinsfrom :J.,i ttle 'Bay . ~ . . . , a~d:"GrélVeSE~d,Barbados~ , ;.. :...... >. . " '.... .1 .', .':; " . Area Ocular plates inserted l, ,V V + l' IV ,V + l, none total Little Bay l 35 40 l 24 101 Graves End l 55 3 0 43 102 total 2 90 43 l 67 203 degrees of freedom = 4 x2 = 44.8 P < 0.001 - 53- ~ . . . '. TABLE 9' ".: ',:':: :, ' ...... '. .- ",' patter~s :dt;·:oèulâ~.'piateIri~ê:rti6n,'· .' ' . .... '". ',.;',. ::',' ",' . ·.f'ound>inur~hiri~. f,'rôm:Bermud'â..~:and' ~ ... '. . ';, , , . . ',.': ~heWe.st .• ]~~âi~·S.t'.{~~hk.~Ori·;'è+9~2.J .• . ':··f' " " . . Areà ·OC~l:~z."pJ.at és· .. insett~d· . '.:,,:.. ('perce.n~) ',; .','. ,.' . ; .::;: Bermuda' West· Indies 25····· total 103···· . 68 degrees of' :freedom = l X2 = 6~27 0.02 >P > 0 • .01 ...... ':>: '. J' - 54 - . '.' . .'~ . ~ ", ..' . \. 'bettteén .!~' lucûÏ1té'r: and;:E ·•. ,:.·v:L:ridi s': :L·ti:·, t'he )le s~:'Iridi éS'~.., Th~ Jr~~u'~~~Y dist~ibtitio~s··.:~f,: '~è'~'n . n~be~s: ',~f: ~:' . ' .. :, " .... ::. ' ...' . .:.: ~ .. : " ," ..... >;r;~:l;:·i~:h,:j~:o~~~:~::èt:!;i~:i~:~~O!:~:C::~~;.\ .•...... " ',' ·.. ··co~tJ::the·:·diifer.é1lges.;:are·.:not:,.·~ign·it~ri:~rit,:a:t 'i~iel.~,.·:.".:~f ... '9oïiiidè~ê'~:":":": ",c:;:··:'":·:i'.>'·:;: > :';:'~~:>.: .. :.; .. . . :.:.'~' :' . . . :.. :, -:' .· •...• ·U.i'~~~fi,·pâ:tr. •....4a.~li.âr~·iri~i~~;~·:i.i{.~able:16·.::'~d· . de'~erminè ••• ~~~th~~::·':e:L ~~~~·:.·.~·~.~~·•. ·haëi;:·:·~ •. ·~ig~·fiç~htii:,·li'Ïgh·ér'~": .. , " ,'\" ',.. .' ...... '. ·1ncldencè;. 6;f·5-pa~f;o~.'~7~P~ir. •. ·:~o~:~·:_.àf.~:$:~~'.·:*h~··::q~~~:~ho~'·::·· tha1i~both' a.~eâs .arê_~.similaf .ip .. ti11i5 ,re.sP~Ç.t; .·«)~2({>.':l> .•. '.:", '.' )·OLIO). '. "" ,'i,;;,:;,Y "'- ---- 7.0 LITTLE BAY GRAVES END c:: w ca :E :lz" c:: _ '. 10 " 2"0 30 10" "20" 30,," "NO. INDIVI DlJALS NO. INDIVIDUALS" FIGURE 19."·" Frequency distributions of mean number of pore pairs in Little" Bay and. Graves, End urchinso" "Se~i texte - 56 -. TABLE 10 The frequency of occurrence of four . pore-pair arc types in Little Bay and Graves End urchins. Area /1 of /1 of /1 of /1 of total 5-pore 6-pore 7-pore 8-pore arcs arcs arcs arcs Little Bay 116 767 125 2 1010 Graves End 152 764 112 2 1030 total 268 1531 237 4 2040 degrees of freedom = 3 X2 - 5. 6 0 0.20 ') P ) 0.10 ~, 57 - . ", . DISCUSSION, , Ihave shownthat Little Bayurchiri.s and'Graves . End' urchinsvary 'SigriificantlY" in ,,' seve~al'morp~OlogiCal .. characters. ' Urchins from Graves End attainalargersize than those from Little Bay. The average test lengthof Graves End urchins was greater than the average test length of urchins trom Little Bay for 10 of 12 collect ions. During August and September 1966 numerous small urchins were collected, therefore, average test lengths of urchins for these two months are not comparable to those of the previous 10 months. The size range of Little Bay urchins was 4 to 47 mm test-length. Graves End urchins ranged in length from 4 to 70 mm with 15 %of the total measuring more than 47 mm test-length (Figures 3 to 6). Thus approx imat~ly 180 Graves End urchins were collected which were largèr than any of the 1,200 urchins taken from Little Blay. It was not possible to collect urchins from the lower limit of their vertical distribution in either location. There is no reason, however, to suspect that very large or very small urchins were collected prefer entially in either area. - 58 - ,No4tol() IIlDllong specimens werefoundfrom Oct "ober,1965 ~OMaY,1.966iJ:l.clusive., 'Urchins, of' this size ", wer~,;,f()und' inJune,J~lyand,Aùgust 1966" i.e.ùrchins ofthis sizear'e'visibleandwerenot overlooked iri " , earlier' collections. ' No urchins smaller than 4mm in length werefound in monthly collections. Several small rocks from the rubble area at Graves End and other similar areas were brought into the'laboratory for close inspection. Very smala. urchi:ls ( ( 4 mm in length). were found in the mat ted algal growth covering the rocks. l suggest that specimens of less than 4 mm in length at Little Bay live in the cracks which honey comb the platform, or at the lower limit of their vert ical distribution. The p~atform does not offer any other shelter to these small urchins. Mortensen's Figure 26 (1921) shows a 15 day old pluteus larva of approximately 0.30 mm length. Thus, a settling E. lucunter juvenile (19 days old) would be approximately 0.60 to 0.80 mm in length. Using the data of Mortensen (1921) and that ob tained in the present study, a rough estimate of the growth of small urchins can be obtained. An individual ...... egg of 0.08 mm (Lewis, 1960a) in diameter spawned in - 59 - ear1y August 1965 wou1d settle as a 0.80 mm metamorphosed juveni1e in 1ate August. Metamorphosing!. 1ucunter 1arvae ha,ve been caught in p1ankton hau1s off the coast of Barbados in Ju1y and August (Lewis, 1960a). By Nov embet 1965 such an urchin could have reached 2.8 mm in 1ength. We can then follow the growth of this individ ual from November 1965 until May 1966 by using data obtained on the g~bwth of smal1 urchins in captivity. In monthlycollections there was no distinct age class division unti1 the 10 mm urchins appeared in May 1966, the month in which smal1 urchins in the aquarium reached g to 10 mm in length. During May and June, young urchins of 10 mm appeared in large numbers in the monthly collections. The Mean 1ength of smal1 urchins at Graves End in June 1966 was 13.0 mm and increased to 20 mm by September 1966. (Figure B). Thus, urchin 1arvae spawned in August 1965 would reach the length of 20.0 mm in one year. Mortensen (1921) reported that E. 1ucunter spawned in March and April in Tobago. Lewis (1960a) found that the breeding period lasted from May unti1 August in Bar bados. In the present study some ripe urchins (on1y male, only female, or male and female) were found every month (Tables Band C, Appendix). In 1966 the ma1esat Graves - 60 - End and Little Bay ripened a month earlier than the fe males. Moore (19.34) attributedthe apparent earlier .ripening of males to bis criteria used in estimating the degree of ripeness of thegonads. Moore's criteria have been followed in the present study. Little Bay urchins spawned in August 1966. The average gonad index dropped from'l.5.3 in Augu~t ta 0.59 in September •. At Graves End, the gonad index fell grad ually in thefall of 196, froml.12 to 0.,8 in four months. In July 1966 the Graves End indexwas 1.25 and in two months fell to 0.68. It appears that the population at Little Bay spawns once a year in July and August, wi th most of the . gametesreleased in August. The population at Graves End has an irregularly bimodal or extended spawning periode Urchins from Little Bay have significantly longer spines per unit test length than those from Graves End (Figure 14). This result is entirely unexpected. It was thought that urchins from Little Bay would have shorter spines due to wear and tear during heavy wave action. On the other hand there is no rubble rock at Little Bay, all loose stones are washed away while the urchins of Graves End live under, and in the niches of, rubble rocks. Perhaps the spines of the latter group - 61 - are worn down in this manner. The spines of urchins from the rubblp. area at Graves End are in fact noticeably blunter than those from Little Bay. Two other important morphalogical differences have been shown to exist between urchins from Little Bay and Graves End. The urchins of'Little Bay have thicker tests and tend to be flatter per unit length thanthose from Graves End. McLean (1964) bas shown that the east coast, Little Bay, is subject to heavier wave action than the west coast, Graves End. It 1s suggested that the mor phological differences observed are due to the influence of heavier wave action at Little Bay. D'Arcy Thompson (1917) indicated that the downward and outward pull of the tube feet of an urchin will tend to flatten the test unless the test grows thicker. Moore (1935) reported that Ecbinus from a 'breakwater' habitat was both flat ter and thicker shelled than the Echinus from two shel- tered are as. With increasing test length, height is a greater proportion of the height/length ratio (Figure 17). Height is 44 to 45 %of height/length ratio wh en urchins are 11 to 15 mm in length. When urchins are 41 to 45 mm in length, height accounts for 51 to 53 %of the heightl length ratio. Urchins from Graves End always have height proportionally greater in the aiL ratio than do urchins - 62 - 1T\ J from Little Bay. This latter difference has been shown to be due to environmental differences in wave action (D'Arcy Thompson, 1917; Moore, 1935). This May be a factor which imposes a size limit on urchins at Little Bay. Because of the current pattern around Barbados the urchins of Little Bay and the rest of the east coast may be isolated from those of the west coast. The work of Emery (1964) suggests that no 1arvae spawned on the west coast are likely to re~ch the east coast, whereas east coast larvae couldeasily be carried to the west coast.. The current pattern sho.wn in Figure 20 (after Emery, 1964) undergoes seasonal shifts. The outflow of fresh water from the Amazon River (during the rainy season) and the Benguela-Guyana current cause a consid erable flow of 10w salinity water north and west past Barbados in May and June (Ryther ~!!, 1967; Calet and Grice, 1967). Lewis ~!! (1962) have confirmed the presence of these low salinity surface water masses around Barbados during the summer months. The larval life span of approximately 19 days of !. 1ucunter (Mortensen, 1921) ru1es out transportation of larvae from the western African coast by the Equator ial Current. The mid-Atlantic island of St. Helena is approximately 2900 miles east of Barbados, as is the nearest coast of Africa. The maximum observed Benguela- . - 63 - N î 10 1 miles A = Little Bay B = Graves· End ... ·.F~:GURE 20 ••'. The. current pat.tern around Barbados, \qest Indies. Figure .af:ter .Emery (1964) his figure 7. ...... . !l' ., .• / - 64 - 11::\.'. Guyana Currentspeed is 2.3 miles per hour in the summer' months (Wùst, 1964). At this rate of 55.2 miles par day it.wou1d take 53 days for the larvae to trave1 to Barbados trom St. Helena or the coast of Africa. The east coast of South America is 1500 miles from St. Helena; 1arvae wou1d be carried from St. Helena to South America in 27 days. Although a11 transport figures are maximum year1y speeds of the Benguela-Guyana Current and the 19 day larva1 life span is approximate, even so it appears un likely from the above data that 1arvae from Africa or St. Helena would reach the coast of Barbados or South America under optimum conditions at the present time. But E. lucunter larvae might possibly be brought to Barbados from the coast of Brazi1 by the Benguela-Guyana Current mentioned above - if the se urchins in Brazil breed in May and June. According to Mortensen (1921), E. 1ucunter in Tobago breeds in March and April; therefore no larvae spawned in Tobago would be carried to Barbados. If E. 1ucunter from the coast of Brazil north of the Amazon do not breed in Bay and June, the population of Barbados is isolated - and the group of urehins on the east coast of Barbados is~ dependent for recruitment on whatever of their own larvae ar~ not washed away by the currents. The presence of E. viridis in the waters off the coast of South America (region of Curacao) presents - 65 - an interesting problem. If the fauna of Barbados regul arly receives recruits from South American waters, why has not E. viridis colonized the coral reefsof Barbados? The two populations examined in the presentstudy differ in several characters: length of spines an.dcolour of test (acquired characters), shape andtestthickness (due to wave action), breeding periodin one: year,pore pair count and oeular plates insert. Mayr (1954)· remarked on this variability of thecharacters of Echinometra lucunter, "specimens from Bermuda and Brazil are very large, African specimens are .very dark, and specimens from St. Helenadiffer inseveral minor characters including the average number.of pore pairs." The very characters shown to be highly variable in this study - . pore pair cOUnt and ocular insert - are used by Mortensen (1943) to help distinguish different Echinometra species. PART II BEHAVIOUR - 66 - INTRODUCTION Echinometra"lucunter ort the platform at Little Bay is e~posed to constant direct light during the day. The urchins at Graves End are found under, and in the crannies of, loose rocks and thus live in a shaded envir onment. The e~periments described in Part II of the present study were designed to discover whether the en vironmental differences in exposure to light in natural conditions were reflected in behavioural differences which could be tested in the laboratory. E~periment One tested the reaction of the urchins to direct overhead light. In E~periment Two urchins were e~posed toa horizontal beam of light. E~periment Three measured the attachment strength of the tube feet of urchins from the two locations. In E~periment Four orientation and righting"behaviour of urchins were ob servedo - 67 - MATERIALS, METHODS AND RESULTS Experiment OI:J,e The apparatus used in Experiment One is shown in Figure 21. Thirty urchins from Graves End and fort y from Little Bay were used (one at a time) in this experiment. Specimens were collected in groups of ten, placed for three hours in daylight conditions in the sea table and then placed in darkness for one hour. All further ex periments were carried out in a darkened room. A microscope lamp was suspended on a steel frame- o work over a glass dish containing water. A circle of light 85 mm in diameter was projected on the bottom of the disho One urchin at a time was placed in the middle of the lighted circle. There was no restriction placed ° on the direction. of movement of the urchin~ The time required for the urchin to move completely out of this circle of light was recorded. A maximum time of 5 min utes per urchin was allowed, after which the animal was removeà, measured and discarded. Table 11 summarizes the results obtained in Ex periment One. This data has been treated by the chi square method of analysis. The reactions of urchina from Little Bay and Graves End are significantly diff erent at the 0.001 level of confidence. The 37 urchins - 68 - ) 1 1 A l 23 cm ~l A - microscope lamp B - urchin C :,,'g;~àss,' 4ish' conta~ning ,sea water \. . \ ' ,F.IGURE 21.' ,The ~pparatus used for Experiment On,e( see text) • .. 1 " - 69 - TABLE 11 The reactions of Echinometra lucunter to an overhead light (see text, Exper iment One). Reaction No movement # reaching goal* total Little Bay 3 37 40 Graves End 29 1 30 total 32 38 70 degrees of freedom = 1. X2 = 52.86 p <. 0.001 * # that moved out of the lighted area. - 70 - from Little Bay moved out of the circle of light in an average time of 1.98 minutes. The onlyurchin from Graves End which moved out of the lighted circle did so in 4.05 minutes. Experiment Two Figure 22 shows the arrangement of the apparatus used in ExperimentTwo. Ten urchins from Little Bay and twenty-twofroin Graves End were used for this experiment. Specimens werecollected and conditioned as in Exper iment One and the experiments were carried out in a darkened room. A plexiglass trough 760 mm 10ng,85.mm wide and 140 mm highwas coated on the outside withblack matt paint, except for a circular hole15 mm in diameter placed 10 mm above the bottom atone end. The trough was filled with sea waterand a microscope lamp was placed level with this aperture in order that a beam of light might shine down the length of thetrough. The urchins couldonly move in a straight line towards or away from the light because of the narrow width of the trough. Position A, 200 mm from the light, was chosen as the star·ting point and positions Band C were chosen - 71 .... /.' A - white' marker' B ~ white marker ,. C -' .white marker D ~ 1.,.cm diameter circ1e, no black peint . E ... micros'cope lamp .~ , , FIGURE 22. .' The': apparatus used .for ExpeI."iment Two.,. fse'e .~'ext) • j ·72 .. ····· . ,'. " ~ '; . ) . .... ,,", , as goals~ Point. 'e:L therside . B'and'POl'nt:(}were','56mm,'6~" '~ . . . . of Point A. ,Thé' ÛI'chiIl~\ 'tôbe·test~d.we~~ plac~d levei .• : . ,". ;.":.' "'. ,,;';' -.. "", .. ",., '.' \. . ",;' with Point'A an.d· given5;niinu'te's toreaêh' ;~itherPoint B " "ôr'Pointe (o~e:urèhin,at; a;time>:~~', Atte-t test111g,-'each .. . :: .... '.: , ' . "'~" ',' ~~ ,··urchiir was mèasuréd 'ând: discàrdèd~ " ' :- . .~.", .. " , ,', During ExperimEmtTW(),lt,was poss~ble to: de termine ' , . the direction{ph~t()PqSi~Ftre~r:Photoh;~gèti v~ ) ' in Little Bay. Theraw,da~a for Table 1.3 (see Table D, 'Appendix) wereanalysedbymeans of a ttest. ,Therewas no significant ditference inspeed of movement of urchins trom Little Bay and Graves End towards oraway from a horizontal beam of light. All the urchins in Experiments ','One and Two, in cluding those which did notmove, showed sensitivity to . light changes. There wasageneralagitationof spines and tube .feet when the'iight beam was blocked ·for three . ~ , seconds, or when the intensity of the light was changed. 73 - TABLE 12 The reactions of Echinometr.a lucunter .~ . . 1;0· a horizontal beam of light j,see text, Experiment Two·) •. Area Reaction No movement Photo{+) Photo{';') total Little Bay l 0 9 10 Graves End 12 l 9 22 total 13 l 18 32 degrees of freedom = 2 X2 = 5 .. 58 0.10 ) P.) 0.05 - 74 - TABLE 13 The average rate of movement of E. lucunter exposed to a horizon tal beam of light (excludingthose urchins that did not move - see text). Area Average speed Range Number (mm/minute) (mm/minute) Little Bay 10 29.9 5.0 - 71.4 Graves End 14 22.6 2.0 - 83.3 degrees of freedom ==·22 t = 0.842 0.30 "> p) 0.20 - 75 - Experiment Three The arrangement of the apparatus used in Exper iment Three 1s shawn in Figure 23. Twenty-six urchins from Little Bay and sixteen urchins from Graves End were collected, put into the sea table for three hours and then tested individually. Each ur chin ta be tested was placed in the Middle of a concrete black in a deep pan of waterand given two minutes ta attach itself ta the black. A 250 gram weight was then put on the weight pan and the test tube holder applied ta the urchin. The length of time the urchin was able ta withstand the pull of the weight was recorded as well as the urchin' s length, width, and height. The empty weight pan was balanced by the test tube holders. The pulleys were of plastic, turned with very little friction and did not corrode in the salt air. The method used was simi1ar ta that described by Sharp and Gray (1962). Table 14 summarizes the results of Experiment Three. The urchins from Little Bay supported a weight of 250 grams for an average of 43.3 minutes; those from Graves End supported the same weight for 'an aver age of 85.0 minutes. T tests applied ta the data in Table E (Appendix) show that there is no significant difference in the holding times of the urchins from ~ . ..' . - 76 - \ . a= 1===t======~===1 , . . A ·-wèight }>àn B - 250 gramweight ·0- test tube holder D":,,:,pan·.filledwith water ·E ,~ concr~'e block '\ . . FIGURE. 23.' The appa'l;atus used in Experiment Three (·see text). 1 i --, -77 - TABLE 14 T test applied to data obtained during Experi.ment Three (see text). Area Average holding Range Number time (minutes) (minutes) Little Bay 15 43.3 1.5 - 160.4 Graves End 11 85.0 8.5 - 255.2 degrees of freedom = 24 t = 1.921 0.10 ) P '1 0.05 - 78 - Little Bay and Graves End. Experiment Four Several of Macdonald's (1936) experiments on orientation of Echinometra lucunter were repeated. When urchins were placed on their ab oral surface in a. glass dish·the·righting reactioncould be delayed b~ placing a piece of. coral in contact with the oral tube feet. This is the same reaction Macdonald des':' cribed. . . Sixteen urchins (eight from Little Bay andeight' from Graves End) were placed upsidedown in a glass dish filled with sea water. The orientation of the urchin in the righting motion and in subsequent walking move ments were noted. Each ur chin underwent two trials. In this experiment the majority of urchins started to right themselves along the III,5 axis (Figure 19). Because !. lucunter is elliptical along the I,3 axis the resulting motion usually was completed along the II,4 axis (the shorter ·diameter). The results of this experiment, and the walking movement experiment are listed respectively in Tables 15 and 16. Chi-square tests were applied to the data contained - 79 - :;~.,' TABLE 15 , Experiment Four:' the orientation of E. lucunter' during righting movements " (seetext )~', ' ,Area, Number of times'. axis used , , : , I,3 ' II,4 III,5 IV', 1 , V,2 total 'Little Bay ° 10 3 1 2 ' 16 Graves End ° '8 2 2 4 16 total ° 18 5 3 6 32 degreesof freedom = 4 2 ' X = 1.38 P >0.80 - 80- TABLE 16 Experiment Four: the orientation of E. lucunter during walking movements . (see t ext ) • Area Number of times axis used I,3 II,4 III,5 IV,l V,2 total Little Bay 2 2 Il 0 l 16 Graves End l 2 Il 0 2 16 total 4 22 0 3 32 degrees of freedom = 4 X2 = 0.68. P >0.95 ." '. - 81 - in Tables 15 and 16. There is no significant difference in the righting or walking movements of the urchins frQm Little Bay and those of Graves End. """ '" .~-~,~~~- - 82 - DISCUSSION The reactions of Little Bay and Graves End urchins to an overhead beam of light differ significantly (Exper iment One). The majority of the Little Bay urchins mov ed out of the lighted circle within two mi~utes. The Graves End urchins stayed under the light, waving their spines and tube feet. The difference in reactions could have been éaused by other factors than light. Little Bay urchins appear to be more active than Graves End urchins, as they do in Experiment Three also. Under the conditions of Experiment Two, urchins could show a photopositive, photonegative or null react~ . ion only. In this experiment there was no significant difference in the photonegative or photopositive react ions of the two habitat groups. This experiment is the Most indicative of the reactions to light of both groups. Urchins from both areas tended to move away from a hor izontal beam of light at a rate of approximately25 mm per minute. In Experiment Three there was no significant difference between the two areas in the length of time they could support a 250 gram weight. Urchins from Graves End attached. to the concrete.. block where they were placed and did not moveA But the urchins from Little Bay - 83 .. ) crawled all over th~ block and when they reached the edge they extended many tube feet to find another sur face. The.~landering" caused the weight to pull them - off the block. If they had not been as active, they probably would have held on much longer than the urchins trom Graves End. - The regain their composure. E~en so, the results agree with Macàonald's (1936) findings that E. lucunter ft is defin- itely functionally bilaterally symmetrical about Loven'sv axis" (i.e •. 111,5 axis): although l do not think his findings, or those of the present study, justify wording this statement so stronglyo - 84- ) SUMMARY AND CONCLUSIONS Random samples of 10,0 urchins a month were taken from two contrasting locations in Barbados, West Indies for a period of one year. One location, Little Bay, was on the wave-swept northeast coast and the other, Graves End, was on the relatively calm southwest coast of the isl~nd. The size and breeding condition of these animaIs were measured. Several experiments designed to test reaction to Iight and environmental influences were carried out. The following conclusions were reached after analysis of the data collected: 1. the test Iength along the elliptical axis of Echino met ra lucunter is a valid measurement of size. This measurement is highly correlated with test width, height and live volume of the urchin. 2. Little Bay urehins have significantly longer spines per unit test length than those from Graves End. 3. Little Bay urehins have signifieantly thieker tests per unit test length than those at Gra~es End. 4. Little Bay urehins are signifieantly shorter per unit test length than those at Graves End. 5. the pattern of oeular plate insertion in the peri proct is significantly different in the two popula tions. At Little Bay oeulars V or none, or V + l - 8 5 - are usually insert. The Graves End urchins have all oeulars exsert or only oeular V ins€rt. 6. there is no significant differenee in the Mean number of pore pairs of the two groups. 7. 180 urchins found at Graves End (over a 12 month period) were 47 to 70 mm in length while no urchins over 47 mm long were found at Little B~y • 8. Little Bay urchins spawned dur-ing the months of July and August 1966. Graves End urchins spawned in Oct ober and November 1965 and again in cJuly and August 1966. 9. no definite age class groups were found in either population. 10. an estimate of the first year's growth of !. lucunter was obtainedfrom material in the literature and mat- erial gathered in the present study. It is estimated that !. lucunter attains the test length of 20 mm in one year. 11. urchins ffom both areas show a photonegative reaction to a horizontal beam of light. 12. Little Bay urchins can adhere to a surface under stress conditions for an average of 43.3 minutes; those from Graves End, under the same conditions, had an average holding time of 85.0 minutes. Due to the great variation between individuals there - $6 - is no significant difference between the holding times of the two groups. 13. over ;0 %of the urchins from both araas righted themselves along Loven's II,4 axis, although MOst started to right themselves'alongthe III,; axis. 14. over ;0 %of the urchins from both areaa commenced walking movement along Loven's III,; axis~ !.~ cunter thus appeara to be functionally bilaterally symmetrical. - 87 - LITERATURE CITED BENNETT, John B. & Arthur C. GIESE~ 1955. The Annual Reproductive and Nutritional Cycles in Two Western Sea Urchins. Biol. Bull. mare biol. Lab., Woods Hole, 129: 226-237. BOOLOOTIAN, R.A. & A.C. GIESE. 1959. The effect of latitude on the reproductive activity of Strongylocentrotus purpuratus. Intern. Oceanog. Congr., Amer. Ass.Adv. Sei., : 216-217. BOOLOOTIAN, R.A. 1966. (Editor). Physiology of Echin odermata. Interscience Publishers, John Wiley and Sons, New York, 822 pp BRANNER, J.C. 1904. The stone reefs of Brazil - their geological and geographical relations. Harvard Coll. Mus. Comp. Zool. Bull., 44: 1-285. BUCHANAN, John B. 1966. The biology of' Echinocardium cordatum (Echinodermata: Spatango~dea) from different habitats. J. mare bial. Ass. U.K., 46 (1): 97-114. - 88 - BULL, H.O. 1938. The growth of Psammechinus miliaris (Gmelin) under aquarium conditions. Rept. Done Mar. labo Cullercoats, sere 3(6): 39-41 CAILLIAUD, F. 1856. Observations sur les oursins per forants de Bretagne. Rev. et Mag. Zool. 4: CALEF, G.W. & G.D. GRICE. 1967. Influence of the Amazon River outflow on the ecology of the western tropical Atlantic. Ile Zooplankton abundance, copepod distribution, with remarks on the fauna of low salinity areas. J. Mar. Res. 25(1): 84-94. CAULLERY, M. 1925. 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Gulf Caribb., 13(2): 329-342 MOORE, Hilary B. 1934. A comparison of the Biology of Echinus esculentus in Different Habitats. Part I. J. mare biol. Ass. U.K •• , 19: 869-885 - 9 5 - MOORE, Hi1ary B. 1935. A Comparison of the Bio1ogy of Echinus escu1entus in Different Habitats. Part II. J.mar. bio1. Ass. U.K., 20: 109-i28 ______• 1936. The bio1ogy of Echinocardium cordatum •. J. mare biol. Ass. U.K., 20: 655- 671 ______• 1937. A Oomparison of the Bio1ogy of Echinus escu1entus in Different Habitats. Part III. J. mare bio1. Ass. U.K., 21: 711-719 MOORE, H.B., T. JUTARE, J.A. JONES, B.F. McPHERSON & C.F.E. ROPER. 1963a. A contribution to the bio1ogy of Tripneustes escu1entus. Bull. mare Sci. Gulf Caribb., 13(2): 267-281 MOORE, H.B., T. JUTARE,J.C. BAUER & J.A. JONES. 1963b. The bio1ogy of Lytechinus variegatus. Bull. mare Sci. G~lf Caribb., 13(1): 25-53 MORTENSEN, Th. 1921. Studies of the deve10pment and 1arva1 forms of echinoderms. G.E.C. Gad. Copenhagen, 261 pp - 96 - ) :J MORTENSEN, Th. 1943. A Monograph of the Echinoidea. III. 3. Camarodonta. II. Echinidae, Strong ylocentrotidae, Parasaleniidae, Echinometridae. C.A. Reitzel, Copeh~gen NUTTING, C.C. 1919. Barbados-Antigua Expedition. Univ •. ' Iowa Studies in Nat. Hist., 8: 274 pp OTTER, G.W. 1932. Rock-boring echinoids. Cambridge Philos. Soc. Biol. Rev. & Proc., 7(2): 89-107 PARKER, G.H.- 1922. The Geotrophism of the sea ur chin Centrechinus.Biol. Bull. mare biol. Lab., Woods Hole, XLIII: 374-382 RYTHER, J.H., D.W. MENZEL & Nathaniel CORWIN. 1967. Influence of the Amazon River outflow on the ecology of the western tropical Atlantic. I. Hydrography and nutrient chemistry. J. Mar. Res. 25(1): 69-83 SHARP, David T. & I.E. GRAY. 1962. Studies on factors affecting the local distribution of two sea urchins, Arbacia punctulata and Lytechinus variegatus. Ecol., 43(2): 309-313 ------97 - ~. ~ STEVENSON, Robert A~ & Sara Lugo UFRET. 1966. Iron, manganese and nickel in skeletons and food of the sea urchins Tripneustes esculentus and Echinometra lucunter. Limnol.& Oceanogr. 11(1): 11-17 SWAN, E.F. 1958 •. Growth and variation in sea urchins of York, Maine. Jo Mar. Res., 17: 505-522 ------_. 1961. ,Some observations on the:growth rate of sea urchins in the genus Strongylocentrotus. f Biol. Bull. mare biol. Lab., Woods Hole, 120: 420-427 TENNENT, David H., M.S. GARDINER & D.E. SMITH. 1931. A cytological and biochemical study of the .ovaries of the sea ur chin Echinometra lacunter. Carnegie Inst. Wash. Tortugas Lab. Papers~ 27: 1-46 THOMPSON, D'Arcy W. 1917. On Growth and Form. Cambridge Univ. Press {, . - 98 - UMBGROVE, J.H .. F. 1947. Coral reefs of,the East Indies. ,Geol. Soc. Amer. Bull., 58: 729;.778 U.S. COAST AND GEODETIC SURVEY. 1967. Tide tables'1967. East coast north and south America including; Greenland. Environmental Sciences Administration, Coast and Geodetic Survey, Depto of Commerce.,' . U.S. NAVY SAILING DIRECTIONS. ,1949. SE.!iling Directions for the West Indies. Vol. II, H.O, Publ. 129 VOSS, G.L. & N.A. VOSS. 1960. An ecological survey of the marine invertebrates of Bimini, Bahamas, with a consideration of their zoogeographical relationships. Bull. mare Sei. Gulf Caribb., 10 (1): 96-116 .. WUST, Georg. 1964. Stratification and Circulation in the Antillean-Caribbean Basins. Part I. Columbia Univ. Press, New York, 201 pp -- - ." -- '"" APPENDIXTABLE a Raw data:the:g~9~~:9~"~m~l+:~~?~~n~:in"anaq~arium." Urchin # l Si z e (mm ):J(; Spine length Date L W H (mm) Test col our Spine colour Location found i~ 27 Nov 65 2.9 2.5 green violet, white tip Church Point, St. James, 2 Feb 66 3.0 3.0 2.2 2.0 - 2.5 green ,- violet on rubble rock 16 Mar 66 4.5 4.0 2.0 4.0 - 5.0 r~d green pink 22 May 66 7.0 7.0 3.0 9.0 brown brown 10 June 66 7.0 6.0 3.0 10 - Il BARE TEST Urchin # 2 0\ 10 Dec 65 3.0 2.5 black blac.k as # l 0\ 2 Feb·66 3.0 2.5 1.8 2.0 - 2.5 black black 16 Mar 66 5.0 4.5 2.5 3.0 - 4.0 red green violet 22 May 66 7.5 7.0 4.0 12~0 "red pink Urchin # 3 10 Dec 65 3 0 0 2.4 black black as"# l 2 Feb 66 3.5 3.0 2.0 4.0 - 5.0 green violet 16 Mar 66 7 0 0 6 .. 0 3.5 7.0 red brown brown 22 May 66 9.0 "9.0 6.0 14.0 red pink .n..... "".... "".A .LAU.wJ.:l D,~_ \ \,;VUlI.l.flUeU J •••••• O" •••••••• 0 ••••••••••••••••••••••••••••••••••• 0 •••••••••••••••••••••••••••••••••••••••••••••••••• • • • ••• • • • • • • • • • • • • ••• 0-0 •••••• ...... Urchin Il 4 Size (mm) Spine length . Date L W .H (mm) Test colour Spine colour Locationfound 10 Dec 65 5.0 4.0 black black As # 1 2 Feb 66 5.0 5.0. 3.5 6.0 - 7.0 red pink-brown 16 Mar 66 8.5 8.0 5.0 10 - 11 red pink 22 May 66 13.0 12.0 8.0 12.0 red black· Urchiil1 5 14 Dec 65 3.5 3.5 green violet, white tip As # 1 2 Feb 66 4.0 4.0 3.0 4.5 - 5.2 red green violet, white tip 0 0 r-I 16 Mar 66 . -7.0 7.0 3.5 9.0 red brown brown 22 May 66 12.0 11.0 6.0 13.0 red pink Urchin # 6 14 Dec 65 5.0 4 .. 5 green green as # 1 2 Feb 66 5.2 4.8 4.0 5.0 6.0 green green, violet tip 16 Mar 66 10.0 9.0 5.0 8.0 9.0 red dark brown 22 May 66 14.0 12.0 7.0 13.0 brown brown A APPENDIX TABLE B (continued) ...... Urchin # 7 Size (mm) Spine length Date L \v -H (mm') . Test colour. Spine colour Location found 17 Dec 65 5.0 5.0- black black Six Men's Bay, on plat- 2 Feb 66 7.0 7.0 4.0 7.0 black black form washed by waves. 16 Mar 66 10.0 à.O 4.0 BARE TEST Urchin # 8 17 Dec 65 6.0 5.0 black black as # 7 2 Feb 66 7.0 6.0 3.0 BARE TEST 1 Urchin # 9 . r-t . 0 r-t là Jan 66 4.0 3.0 black black as # l 2 Feb 66 4.5 3.5 2.5 green violet 16 Mar 66 7.0 7.04.0 10.0 red brown brown 22 May 66 12.0 11.0 -7.0 16.0 red black * L =: test length, \1= test width, H = test height -- . ~. -. - - -. APPENDIX TABLE B- Seasonal variati0I?- in.gQnad:ç9n~~~~on:9f.L~tt~~:l?ay.u~chins Male Female % total Date unripe(%) ripe(%) spent (%) - . #- -unripe(%) ripe{%) spent(%) # spent October 12, 1965 8' 0 92 26 50 g 42 24 62 November 10 50 10 40 20 50 0 50 30 46 December 14 42 0 58 25 27 3 70 25 64 January 17, 1966 21 0 79 24 19 4 77 26 80 February 19 6 6 88 18 3 0 97 32 94 March 17 0 4 96 .. 26 8 O· 92 24 94 ·N o April14 4 19 77 25 4 13 83 25 80 r-I 1 May 10 37 17 46 22 11 11 78 28 62 June 10 0 50 50 18 38 6 56 32 54 July 12 26 53 21 19 27 41 32 Jl 28 August 9 0 100 - 0 26 25 75 0 24 0 September 10 52 18 30 23 48 4 48 27 40 ~ ... -.. -. " - .-. A.PPENDIX TABLE .& - Seasonal variation in gonad çondition of Graves End urchins. '. . , Male Female % total Date' unripe(%} ripe{%) spent{%} # unripe(%} ripe(%) spent(%} # spent t::."· Octobe'r '19,-1965 14 72 14 22 30 70 0 29 6 Nov~mber 18·' . 16 84 0 18 22 56 22 33 14 December 20. 48 38 14 21 45 31 24 29 20 " , January 26;':1969 24 20 56 25 16 0 84 25 70 Fe bruary ·.24: 14 7 79 27 9 9 82 23 80 March 20:·:" ". 3 0 97 29 0 0 100 21 98 8 April 18, 0 l8 82 22 Il 3 86 28 84 1"""1 1 May 16 5 21 74 19 32 0 68 31 70 June 14 25 67 8 24 58 23 19 26 14 July 16 9 91 0 22 18 75 7 28 4 August 17. 17 75 $ 24 19 73 8 26 8 Se ptember:Œ2 67 22 Il 18 75 9 16 32 14 tffp.. - 104 - APPENDIX'TABLE D Theratës.of.inovement of'individual' m-chins' .duririg,-~Xp~riment Two: (~e~u text). ~eed* (mm niinute) Little Bay Graves End 38.5 4.6 8.6 16 0 7 22.7 25 00 2708 15.6 50.0 41.7 31.2 16.7 29.4 83.3 5.0 24.2 14.3 ,38.5 71.4 2.0 22.7 2.0 20.0 3.0 * determined from one run per urchin. ~ .. .J '. ~ ...... - 105 - APPENDIX TABLE E The individua1 adhesion periods of urchins inExperimentT~ree. Urchins .. that did not" adhere to the b10ck for at 1east one minute have been exc1uded. Holding time . (minutes) Little Bay Graves End 19.8 65.5 41.7 162.1 13.2 44.2 58.5 73.3 1.5 255.2 3.7 89.0 29.0 13.7 160.4 83.3 23.0 82.7 13.7 57.5 84.4 8.5 15.7 74.7 59.9 50.5 ------106 - APPENDIX TABLE F Discrete groups and group means found in month1y samp1es by usingHardings' (1949)method of iso1ating po1ymoda1 peaks in a distrigution , .. Month First group Second group Area (1966) Mean '1ength Mean 1ength (mm) . {mm} Little Bay May 13.75 33.50 June 16.75 33.00 Graves End June 13.00 38.75 Ju1y 16.75 38.50 August 16.75 37.50 September 20.00 43--.00 ," - 107 - APPENDIX TABLE a . Size class (test length) and length of spines of Little Bay and Graves End urchins collected during the period January - May 1966. Little Bay Graves End Test # Mean spine # Mean spine length(mm) individuals length(mm) individuals length(mm) Il - 15 1 14 0 16 - 20 2 13 1 10 21 - 25 4 17 5 13 26 - 30 16 20 21 14 31 ~ 35 40 21 26 14 36 - 40 29 21 18 17 41 - 45 9 22 16 16 46 - 50 0 6 19 51 - 55 0 5 18 56 - 60 0 2 21 61 - 65 0 2 18