Sex-Specific Growth and Survival in the Mole Crab Emerita Portoricensis (Schmitt)

Home , Emerita (genus), Emerita analoga, Emerita rathbunae, Emerita talpoida, Hippidae

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JOURNALOF CRUSTACEANBIOLOGY, 11(1): 103-112, 1991

SEX-SPECIFIC GROWTH AND SURVIVAL IN THE MOLE CRAB EMERITA PORTORICENSIS (SCHMITT)

Miguel P. Sastre

ABSTRACT The anomurancrab Emerita portoricensis often occursin the intertidalzone of sandybeaches in the Caribbean.Four sites on PuertoRico, within Mayagiiezand Aiiasco bays, were sampled for 2 yearsin orderto constructsize-frequency distributions and determinerelative growth and survival of each sex. Emeritaportoricensis was regardedas a dioecious species, since no inter- mediateforms were found in any of the 30,755 specimens.Size frequencydistributions of male and female mole crabs were not significantlydifferent between sites. However, the maximum length of the carapaceof male mole crabs (11 mm) was shorterthan that of females (19 mm). Growthcurves based on size-frequencydistributions indicated that females grew significantly fasterthan males. Densities of males were greatestfollowing recruitment. The percentagesurvival of youngindividuals (< 5 months of age)was higherfor males than femalesand percentage survival of older mole crabs was greaterfor females. Results of this study indicate that sexual heterogeneitiesin size structureof populations can be explained by differentialgrowth and survival of the sexes.

Mole crabs of the genus Emerita (Ano- spermatophoresto pleopods of larger fe- mura: Hippidae) are commonly encoun- males (MacGintie, 1938; Wharton, 1942; tered in the intertidalzone of temperateand Knox and Boolotian, 1963; Efford, 1967; tropical sandy beaches. These crabs usually Diaz, 1980; Subramoniam, 1984). aggregateand migrate alongshore (Dillery Caribbean mole crabs, E. portoricensis and Knapp, 1970). Smaller crabs typically (Schmitt, 1935), spawn continuously occur in the upper portion of the littoral throughout the year. The proportion of zone, while largerorganisms are usually lo- ovigerous females increases with growth to cated at lower levels within this zone (Ef- larger size classes. The largest carapace ford, 1965). Like other beach organisms, length observed for megalopae is approxi- species of Emerita migrate synchronously mately 3 mm, which coincides with the with the tide and maintain zonation smallest carapacelength of the firstjuvenile (MacGintie, 1938; Wharton, 1942; Efford, instar (Sastre, 1988). 1965; Cubit, 1969). The hypothesis of whether sexual heter- Within the genus, male crabs generally ogeneities in size structuresof E. portori- are smaller than female crabs (Goodbody, censis are caused by differentialgrowth and 1965; Barnes and Wenner, 1968; Wenner, survival rates between sexes is examined. 1972; Subramoniam, 1977; Diaz, 1980). The possible occurrenceof protandricher- This sexual differencein size has been ex- maphroditismis also examined in this spe- plained in terms of differentialsurvival and cies. growth rates for Emerita analoga (see Ef- ford, 1967) and Emerita talpoida(see Diaz, 1980). Subramoniam (1981) proposed re- MATERIALSAND METHODS version of sex from male to female for the A descriptionof study sites and methods employed case of Emerita asiatica. Although protan- to monitor populationsof E. portoricensiswere pre- dry also was suggested for E. analoga (see viously described(Morelock et al., 1983;Sastre, 1988). Barnes and Wenner, 1968; Wenner, Briefly,four study sites wererandomly selected at Ma- 1972), yagiiezBay and two at Aiiasco Bay, Puerto Rico. Sed- a further study did not support this hy- iment enclosed in 30 quadrats(1,254 cm2each) 10 cm pothesis (Wennerand Haley, 1981). deep was sampled at monthly intervals for 2 years at Precocious sexual maturity (neoteny) in each site. All sediment was sieved through2-mm and males has been reportedin at least five spe- 1-mm mesh size sieves. Emeritaportoricensis retained in each quadratwere sexed and the carapacelength cies of Emerita (not includingEmerita por- was measured. These data were used to construct toricensis) (see Efford, 1967). Neotenous monthly size-frequencydistributions (Figs. 1, 2). The males attach ribbon-shaped or spherical presenceof eggs in the abdomenof femalesand sperm

103 0045259 -

104 JOURNAL OF CRUSTACEAN BIOLOGY, VOL. 11, NO. 1, 1991

240 - February 1984 210 180 - 24( C) July 1983 21C 150 120 - 18c 0- 15t 0- 90- 60 - 12C 0- 30 910- 6( 0- 0 - 240 March 1984 3( 0- ' 210 10- 180 241 0- August 1983 211 150

18( 120 15( 90 121 60 0- 9( 30 61 0 3; 570 0- >. 540 zZ 24( 0- September 1983 510 211 480

18l 450 15! 420 12 0- 390 0 9 360 !O 6 330 -I 3 300 LL 270 2424 o - October 1983 240 Rpril 1984 21 0- 210 18 0- 180 15 0 - LU 150 121! 0- 120 9 0 LJ 90 6 60 3 30

24 0 480 21 LO0 - 450 18 420 15 0 - 390 WJ 12 tO 360 9 0 - 330 6 ;O 0 O - 300, 310 C,) 270 24 10 - DeceMber 1983 240 nay 1984 21 .O 210 18 180 s0 - 15 150 20 - 12 120

990 - 90

6i0 _ 60 3 30 0 24 40 - January 1984 240 June 1984 2J LO 210

11 10 - 180 - SO 150 121;20 120 90 - 90 60 - 60 30 30

0 ...... 0 3 4 S 6 7 8 9 10 1 12 13 14 15 16 17 18 19 3 4 5 6 7 8 9 10 14 12 13 14 15 16 17 18 19

CARAPACE LENGTH (MM) Fig. 1. Size-frequency distributions of females of Emerita portoricensis (individuals/15.48 m2) at all sites for 1983-1985. 0045260

SASTRE: GROWTH AND SURVIVAL IN EMERITA PORTORICENSIS 105

240 July 1984 210

180 150 120

90 60 30

1984 August 24( 0 - January 1985 21C

18C - 15( 120 - 12( 0 90 - 92 0 60 6C0 - 30 31 - 0 240 SepteMber 1984 0 24( - February 1985 210 211 00- 180 z 18( 0 - 150 151 0 - 120 121 90 _ 9( 60 6 0 30 3 C~ O 0 - 540 24 510 21 480 18 - 0 450 15 420 12 ;00 -r 390 9 360 6 lO -

330 3 10 4 300 270 24 t0 Apri 1 1985 21 LO 240 October 1984 I-m 210 18 0 - 180 15 O 150 12 - 9 0 - 120 30 -J 6 390 60 330 30 mG...~...,~ 27 ?o 0 240 HoveMber 1984 24 (In 210 21 180 18 150 15 50 - 120 12 90 9 60 620

30 330 0 0 240 Decemnber 1984 24 40- June 1985 210 21 LO

180 150 15 50- 0 120 12 20

90 90- 60 60 30 30 0 O

3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

CARAPACE LENGTH (MM) . 0045261

106 JOURNAL OF CRUSTACEAN BIOLOGY, VOL. 11, NO. 1, 1991

360 July 1983 320 280- 240- 360 - February 1984 200- 320 160 - 280 120 240 80 200 40- 160 0 . L 480 120 440 _ 80 400- 40 360 August 1983 0 360 March 1984 320 - 320 280 - 280 240 - 240 200- 200 160 160 120- 120 80 80 40- 0 40 0 0 360 - eptenber 1983 600 z 320 560 280- 520 240 - 480 200- 440 160 - 400 120 360 April 1984 80 320 40- 280 U- 0 240 LLI 360 October 1983 200 320 160 280- 120 240- 80 200- 40 160 - 0 120 880 LLI 80 840 40 - (I) 800 36( o'D L November 1983 760 32t 720 28C 680 1 - 24C D - 640 600 20C 0 - 16C O - 560 12C O - 520 8(C 480 4( 440 400

36C 30 1.December 1983 360 Hay 1984 (n 320 32C 28C o - 280 m 24C o - 240 20( 3 - 200 160 16? o - 3 121 120 81 80 4( 40 0 0 - 361 0 - January 1984 360 June 1984 0 321 320 28( O0 - 280 - 241 240 0 - 20( 200 16 0- 160 121 0 120 8 80 0 - 4 0 - 40 0 3 4 5 6 7 8 9 10 11 3 4 5 6 7 8 9 10 11

CARAPACE LENGTH (MM) Fig. 2. Size-frequency distributions of males of Emerita portoricensis (individuals/15.48 m2) at all sites for 1983-1985. 0045262 0

SASTRE: GROWTH AND SURVIVAL IN EMERITA PORTORICENSIS 107

600 560 520 480 440 400 360 320 280 240 200 160 361 0 January 1985 120 321 0. 80 28( 0 40 24( 0 0 20( D 360 August 1984 16( 0 320 12( 280 8( D 240 4( 0: 200 0 0. 160 361 0 February 1985 D- 0 120 32( 0 80 281 0 z 40 24( 0 0 201 LU 360 Septexber 1984 16( 0 320 12( 0 0. 280 8( 0 240 4( UI 200 OC 160 361 120 32( LLJ 80 28( 40 24( 0 201 0 - 680 16( o - LU 640 121 0 600 81 560 4(41 520 480 36( 0 - April 1985 w 440 321 0- 400 28( 360 October 1984 24( O 320 201 280 16( 240 121 o - 0 200 8( 0 - 0 - 160 41 120 O 80 48( 40 441 40( C') 0 360 - oveber- 1984 361 D - May 1985 320 32( o_ - m 280 28( 240 24( o 200 201 160 16( 120 12( 80 8( 40 4( 0 360 December 1984 36( 0O - _ June 1985 320 32( 0 - 280 281 0 240 24( 0 200 20( 160 161 120 121 80 8 40 4 un - I, m 3 4 5 6 7 8 9 101o 1 3 4 5 6 i 8 9 10 11

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Percentagesurvival was calculatedfor each size class as: (S,,+/S) x 100. A three-wayANOVA test was used to evaluatedif- 560 - O \ ferences in percentagesurvival among age, months, W 40-40 - and sexes (Sokal and Rohlf, 1981). Regressionanalysis was used to determinepossible Z 30 - relationshipsbetween monthly growth and carapace W 20 - lengthfor each sex. Differencesin elevation in each of the above regressionswere tested using analysisof co- 10 - variance(Sokal and Rohlf, 1981).

0 2 3 4 5 6 7 8 9 10 11 12 RESULTS CARAPACE LENGTH(mm) Size-frequency Distributions Fig. 3. Sex ratio as a functionof size (age).n, number of Emeritaportoricensis. Size-frequency distributions of each sex were not significantly different among sites. ribbons attached to the genital papillae of males also Therefore, data from all sites were pooled were observed. for each sex. Growthwas estimatedby periodicallyfollowing in- Sexual in size structures dividual peaks in size-frequencydistributions. The heterogeneities numberof months elapsed duringeach growthincre- were evident, since males reached a cara- ment (measuredas an increasein carapacelength) was pace length of 11 mm as compared to 19 counted for each sex in order to calculatedifferential mm for females. Combined data for two growthfor each size class. years indicate that males became most The von Bertlanffyequation: abundant (68%) at about 5 mm (Fig. 3), dL/dt = k(Loo - Lt) whereas females achieved a sex ratio of 100% was used to fit differentialgrowth calculations. The from 12-19 mm. discrete form: AL/At, the change in carapacelength Recruitment of megalopae was synchro- (mm) per month, was used to approximatedL/dt. The nized for both sexes Smaller size slope k in the discreteform of the above equationwas (Figs. 1, 2). calculated by the regressionof AL/At against mean classes (3-5 mm) were more abundant dur- carapacelength, Lt. The asymptotic height, Loo, was ing April, May, and October 1984, and dur- approximatedby the point wherethis line intercepted ing May 1985. The frequency of these size the x-axis. classes was much lower fall and win- The over the entire of E. during growth pattern life-span ter 1983 portoricensiswas calculatedusing the integratedform and throughout winter 1984. of the equation: Males above 8 mm were present throughout both and Lt = Loo(l - Ce-kt) years except during February March 1985. Female size classes 15 mm or where Lt is carapacelength at time t (months) and C were absent and k are constants.A measurementof carapacelength longer during September 1983, at any knownage was used to calculateC (Grigg,1974). from July to October 1984, and during June The planktoniclarval life period of E. portoricensis 1985. was estimatedby the time elapsedbetween periods of very low (<2,500 eggs) or zero total egg production Growth and very low megalopae abundance(<3 specimens/ m2): October 1983 to January 1984; March to May Differential growth between sexes was 1984; November 1984 to January1985, and January large at smaller carapace lengths and de- to May 1985. In two cases the time lag between these creased as crabs periodsis 2 months. This was assumedto be constant grew (Figs. 4, 5). Monthly and was used as an approximationof the length of growth determinations were observed more larval life in survival curves. Larval survival was es- clearly at smaller carapace length, when timated each month by calculatingthe total number crabs grew at a faster rate and abundance of eggs which survived to recruits(after 2 months). It was still a was assumed that all live larvae. Per- relatively high. Hence, greater eggs produced number of sonal observationsin the laboratoryand data from E. growth increments could be plot- talpoida(see Diaz, 1975) supportthis assumption. ted during this period (Fig. 4). Survivorshipschedules for all age classeswere based An analysis of covariance indicated sig- on actual absolute frequencies,S,, ratherthan on the nificant differences in elevation (position) proportion of organisms surviving to different age for male and female increment re- classes,1x. Survival curves were calculated by following growth cohorts each successive month duringthe firstyear of gressions (SS and MS = 6.3781; d.f = 1; P sampling. = 0.003). Nonsignificant differences were 0045264

SASTRE: GROWTH AND SURVIVAL IN EMERITA PORTORICENSIS 109

4.U 10000 - CI FEMALES AL/At = 3.3558 0.1799Lt r = 0.78 *- MALES 3.5 0 + MALES AL/At = 2.9546 - 0.3957Lt r = 0.87 O-- FEMALES E 3 2 3.0 D ]O >. 2.5

-a: 2.0 I z1 1.5 1000_ o 1.0 _+ D cr % 0.5 ++F 2 2 3 6 ... ffi 4; I Il I! I ! It IJ ! 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

Sexual maturityin males Sexual maturityin females CARAPACE LENGTH (mm) 100 Fig. 4. Average monthly increase in carapace length x (AL/At) of males (N = 13) and females (N = 15) of \, Emerita portoricensis. Numbers indicate amount of t- o multiple data points at each mark; above, females; be- low, males. observed among slopes (SS and MS = I0 0.9905; d.f = 1; P > 0.05). Females always \ '\R grew faster. At 3 mm the growth rate of females was 2.8 mm per month as com- ,I pared to 1.8 mm for males (Fig. 4). Al- though the method used to measure growth ' in the field can be it can // i Ii ~ I1 I I subjective, give / 2 4 6 8 10 12 14 16 18 20 reasonable estimates of male and female AVERAGE AGE (MO) growth rates. Fig. 6. Survivorship curves for male and female Emerita portoricensis at different age classes. Survival Age-specific absolute density, Sx, was used Monthly survival calculations of the ben- as a measure of survival. Lowest survival thic life-stage of both sexes did not reveal rates were calculated during the planktonic much clear information (due to noise), since stage. Monthly estimates on the survival of the percentage survival reached above 100% E. portoricensis from egg to recruit (2-3 on many occasions. However, the slope was months) ranged from 0.0353 to 11.3%. No negative at all times except for the Decem- significant correlation was observed be- ber 1983 recruits. To increase confidence, tween percentage survival of larvae and monthly survival data were pooled (except population size (males, r2 = 0.1594; fe- for the December 1983 recruits) and aver- males, r2 = 0.1558; d.f = 20; P > 0.05). aged (using the geometric mean) in order to construct male and female survivorship 20 curves (Fig. 6). The density of male survi- 18 - FEMALES vors was higher than that of females during 16- the first year of life (after recruitment). E 14 However, I assumed that the number of male survivors dropped to zero at age 13 months. The significant sex x age interaction in a 3-way ANOVA indicates that the age-specific survivorship curves differ between 2 - males and females (SS = 45,284.670; d.f =

1 2 3 4 5 6 7 8 9 10 1 2 13 6; MS = 7,547.445; F= 5.611; P < 0.001).

TIME (mo) The percentage survival of males was higher than that of females for classes. = younger age Fig. 5. Growth curves for males (Lt 11.0(1 - females survived better at oldest 0.8440e--03957t)) and females (Lt = 19.0(1 - However, 0.8549e-? 1799t)) of Emerita portoricensis from data age intervals (Fig. 7). The month x age in- shown in Fig. 4. teraction indicates that the survival of dif- 0045265

110 JOURNAL OF CRUSTACEAN BIOLOGY, VOL. 11, NO. 1, 1991

10o crements were much higher than those for FEMALES 90-----0 - MALES males. The same pattern was observed in 80- - E. portoricensisfrom beaches at Mani and > 70 - Guanajibowhere females grew significantly

60 - faster than males at all sizes. t- Estimatesof the 2-month lar- 50 - planktonic val life duration are rough approximations z - 40 for the populationof E. portoricensiswithin cr -- LL 30 Q. Mayagiiezand Aniascobays. The develop- 20 - ment time from eggto juvenile of laboratory 10 - rearingsof E. talpoida is approximately38 o I i i i I i I I I I I I days and the difference between pulses of 1 2 3 4 5 6 7 8 9 10 11 121314 15 16 17 breedingand recruitmentis approximately AVERAGE AGE (mo) 60 days (Diaz, 1980). Fig. 7. Percentage survival of male and female Emer- The estimatedrange of survival of E. por- ita portoricensis at different age classes, with estimates toricensisfrom to of standard error based on arcsine transformed data. egg recruit(0.0353-11.3%) is within a range of estimates observed for other marine invertebrateshaving various ferent age classes varied significantlyfrom types of development (Hines, 1986). The month to month (SS = 352,377.744; d.f = estimated larval survivorshipof E. talpoida 66; MS = 5,339.057; F= 3.969; P < 0.001). in North Carolinawas 0.4131 and 0.6067% for females and males, respectively (Diaz, DISCUSSION 1980). In the present work, sexual maturity in Monthly survival curves of both sexes re- males was observed at 5 mm. At this size, flected a noticeable amount of noise, since males had well-definedgenital papillae and some values exceeded 100%.Sampling er- a vas deferens swollen with spermato- ror due to patchinessoften observed in this phores.These spermatophoreswere long and genus (Cubit, 1969; Perry, 1980) could have sticky, similar to those observed by Subra- influencedthe above situation. The greater moniam (1977, 1984). Males lost natatory proportion of male crabs observed during pleopods and other characters unique to the samplingperiod (Sastre, 1988) could be megalopae at 3 mm; the smallest mature due to a higher number of survivors in males did not have natatory pleopods and youngerage classes (Fig. 6). The percentage charactersunique to megalopae. survival of both sexes was age-specific(i.e., Females of E. portoricensisreached ma- varied significantlyfrom age to age). Young turity at 7 mm. At this size, females had (small) males and old (large) females eggs attached to their pleopods and abdo- achieved higher percentage survival rates men. In Jamaica,the smallest ovigerous fe- (Fig. 7). The month x age interaction in male was 9 mm (Goodbody, 1965). Most survivorshiprevealed a highly variablepat- other species of Emerita reach sexual ma- ternwhich did not follow any seasonaltrend. turity at size classes larger than 7 mm. Even though ocean currentsare known to Emerita asiatica reaches sexual maturityat affect dispersal (Scheltema, 1971; Jackson 19 mm (Subramoniam,1977, 1981), Emer- and Strathmann,1981) the effect of immi- ita austroafricanaat 23 mm (Barnard,1950), gration and emigration of larvae was ig- Emerita holthuisiat 10 mm (Achuthankutty nored. The bathymetryand circulationpat- and Wafar, 1976), Emerita rathbunaeat 33 tern of both bays (Morelock et al., 1983) mm (Efford, 1967), E. talpoida at 14 mm suggest a relatively low water interchange (Efford,1967; Diaz, 1980), and E. analoga between the bays and the open ocean. The at 8 mm (Barnesand Wenner, 1968). hydrology of the area is similar to that of Sexual differences in growth rates are an estuary since both bays receive fresh- common in this genus.Females usually grow water dischargefrom three rivers and sev- much fasterthan males (Efford,1967; Oso- eral other sources (Morelock et al., 1983). rio et al., 1967). Auyong (1981) found that The inshore-offshore circulation pattern in every size class of E. analoga held in the usuallyassociated with this system can help laboratoryfor four days, female growth in- to retainplanktonic larvae in inshorewaters 0045266

SASTRE:GROWTH AND SURVIVALIN EMERITAPORTORICENSIS Ill

(Bousfield, 1955; Scheltema and Carlton, thuisi Sankolli.-Indian Journalof Marine Science 1984; Scheltema, 1986). The above could 5: 98-102. in the densities Auyong,J. 1981. Comparisonof populationstructure explain part high population of sand crabs (Emeritaanaloga Stimpson)living at of Donax denticulatusand E. portoricensis increasingdistances from a power plant.--M.S. the- observed in these areas (Sastre, 1981, 1984, sis, University of California,Santa Barbara,Cali- 1988). fornia. Pp. 1-90. Sex via Barnard,K. H. 1950. Descriptivecatalogue of South change protandroushermaphro- African decapod Crustacea.-Annals of the South ditism is common in crustaceans(Ghiselin, AfricanMuseum 38: 1-837. 1969; Policansky, 1982). It is a subject of Barnes, N. B., and A. M. Wenner. 1968. Seasonal much research focusing on the relative re- variationin the sandcrab Emerita analoga (Decapo- productive success of males and females, da, Hippidae)in the Santa Barbaraarea of Califor- a model nia.-Limnology and Oceanography13: 465-475. largelybased upon size-advantage Bousfield,E. L. 1955. Ecologicalcontrol of the oc- (Warner,1975; Policansky, 1982). Emerita currenceof barnaclesin the Miramichi Estuary.- asiatica is the only species within this genus Bulletinof the National Museumof Canada 137: 1- where protandric hermaphroditism possi- 69. occurs.The of Cubit,J. 1969. Behaviorand physicalfactors causing bly disappearance genital pa- aggregation in the sand crab Emerita analoga pillae is the first visible sign of sex reversal. (Stimpson).-Ecology 50: 118-123. Gonads of intersexual organisms show in- Diaz, H. 1975. Life history patternand population active testicularand active ovarianportions growth of the sand crab Emerita talpoida (Say).- (Subramoniam, 1981). Ph.D. dissertation,Duke University,Durham, North the of Carolina.Pp. 1-148. Wenner (1972) suggested presence 1980. The mole crabEmerita talpoida (Say). protandrichermaphroditism for E. analo- A case of changinglife history pattern.--Ecological ga, since all individuals are female when Monographs50: 437-456. largeand mostly male at smallersize classes. Dillery, D. G., and L. V. Knapp. 1970. Longshore Wennerand found severallines movements of the sand crab,Emerita analoga (De- Haley(1981) capoda, Hippidae).-Crustaceana 18: 233-240. of evidence which negated the original sex Efford, I. E. 1965. Aggregationin the sand crab, reversalhypothesis. Some coincide with re- Emerita analoga (Stimpson).-Journal of Animal sults obtainedduring this study:(1) Females Ecology 34: 63-75. grow significantly faster than males; (2) 1967. Neoteny in sand crabs of the genus Emerita(Anomura, Hippidae). -Crustaceana 13:81- Males and females survive at significantly 93. differentrates; and (3) No intermediateform Ghiselin, M. T. 1969. The evolution of hermaph- was observed in any of the 30,755 speci- roditism among animals.-Quarterly Review of Bi- mens. Therefore, it is unlikely that sexual ology 44: 189-208. in size structureof E. Goodbody, I. 1965. Continuous breedingin popu- heterogeneities por- lation of two tropicalcrustaceans Mysidium colum- toricensiswere due to protandrichermaph- biae(Zimmer) and Emeritaportoricensis (Schmitt). - roditism. Ecology46: 195-197. Grigg,R. W. 1974. Growthrings: annual periodicity in two gorgoniancorals. -Ecology 55: 876-881. ACKNOWLEDGEMENTS Hines, A. H. 1986. Larvalproblems and perspectives in life historiesof marineinvertebrates. -Bulletin of I thank Elena J. Biam6n, Jose E. Rosario Fibregas MarineScience 39: 506-525. and Daniel Matos for their assis- (Chevaro), helpful Jackson,G. A., and R. R. Strathmann. 1981. Larval tance in the field. Drs. C. Angel Berrios,Terry Hazen, mortality from offshore as a link between Juan A. Juan G. and Luis R. Al- mixing Rivero, Gonzilez, precompetentand competent periods of develop- modovarprovided helpful suggestions during this study. ment.-American Naturalist 118: 16-26. This investigationis partof a Ph.D. dissertationby M. and R. A. Boolotian. 1963. Functional P. Sastre at the of MarineSciences Knox, C., (1988) Department morphologyof the externalappendages of Emerita of the University of Puerto Rico at Mayagiiez,Puerto -Bulletin of the SouthernCalifornia Acad- Rico. I am to advisor, Dr. Paul M. analoga. very grateful my emy of Sciences 62: 45-68. Yoshioka.Financial support of this workwas provided MacGintie,G. E. 1938. Movementsand matinghab- in part by a Sigma Xi grant-in-aidof researchand by -American for Science and En- its of the sand crab, Emerita analoga. a grantfrom the ResourceCenter MidlandNaturalist 19: 471-481. gineering(University of Puerto Rico, Rio Piedras). Morelock,J., K. Grove, and M. L. Hernmndez.1983. Oceanographyand patterns of shelf sediments.- LITERATURECITED Journalof SedimentaryPetrology 53: 371-381. Osorio, C., N. Bahamonde,and M. T. L6pez. 1967. Achuthankutty,C. T., and M. V. M. Wafar. 1976. El limancheEmerita analoga (Stimpson) en Chile.- Ecologyof sandy beach at Sancoale,Goa: Part II- Boletin del Museo Nacional de HistoriaNatural 29: Population model and productionof Emerita hol- 60-110. 0045267

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Perry, D. M. 1980. Factors influencingaggregation mura of Porto Rico and the Virgin Islands.-Sci- patternsin the sand crab Emerita analoga (Crusta- entificSurvey of PuertoRico and the VirginIslands, cea: Hippidae).-Oecologia 45: 379-384. New York Academy of Sciences 15(2): 125-227. Policansky,D. 1982. Sex change in plants and ani- Sokal, R. R., and F. J. Rohlf. 1981. Biometry.-W. mals.-Annual Review of Ecologyand Systematics H. Freeman,San Francisco,California. Pp. 1-859. 13: 471-495. Subramoniam,T. 1977. Aspects of sexualbiology of Sastre,M. P. 1981. The ecology of Donax denticu- the anomurancrab Emerita asiatica.- Marine Bi- latus and its limiting factorsin PuertoRican beach- ology 43: 369-377. es.-M.S. dissertation,University of Puerto Rico, 1981. Protandrichermaphroditism in a mole Rio Piedras,Puerto Rico. Pp. 1-65. crab, Emerita asiatica (Decapoda:Anomura).-Bi- 1984. Relationshipsbetween environmental ological Bulletin 160: 161-174. factorsand Donax denticulatuspopulations in Puer- 1984. Spermatophoreformation in two in- to Rico.--Estuarine, Coastal and Shelf Science 19: tertidalcrabs Albunea symnista and Emeritaasiatica 217-230. (Decapoda:Anomura).-Biological Bulletin 166: 78- . 1988. Sex specific life history strategy of 95. Emerita portoricensis (Schmitt).-Ph.D. disserta- Warner, R. R. 1975. The adaptive significanceof tion, University of Puerto Rico, Mayagiiez,Puerto sequentialhermaphroditism in animals.--American Rico. Pp. 1-141. Naturalist 109: 61-82. Scheltema,R. S. 1971. Larvaldispersal as a means Wenner,A. M. 1972. Sex ratio as a function of size of geneticexchange between geographically separat- in marineCrustacea. -American Naturalist106:321- ed populations of shoal-waterbenthic marine gas- 350. tropods.-Biological Bulletin 140: 284-322. ,and S. R. Haley. 1981. On the question of 1986. On dispersaland planktoniclarvae of sex reversalin mole crabs (Crustacea,Hippidae).-- benthicinvertebrates: an eclecticoverview and sum- Journalof CrustaceanBiology 1: 506-517. mary of problems.-Bulletin of Marine Science 39: Wharton,G. M. 1942. A typical sand beach animal 290-322. the mole crab, Emerita talpoida (Say).-Ecological ,andJ.T.Carlton. 1984. Methodsof dispersal Monographs12: 157-164. amongfouling organisms and possibleconsequences for rangeextension and geographicalvariation. -In: RECEIVED:10 February 1990. J. D. Costlowand R. C. Tipper,eds., Marinebiodete- ACCEPTED:4 July 1990. rioration:an interdisciplinarystudy. Naval Institute Address: Press, Annapolis, Maryland.Pp. 127-133. Departmentof Biology,University of Puer- Schmitt, W. L. 1935. CrustaceaMacrura and Ano- to Rico, Humacao,Puerto Rico 00661.

Errata-JCB, vol. 10, no. 4 Page 624. At the top of the right hand column one line was dropped in printing. Please read:Nuclei lackingstained nucleoli were detectedin some areas of some preparations. Page 766. Add: Streptocephaluskargesi, new species ...... 5:169. Page 766. Change: Tortanussheni, new name ...... 8:656.