See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/231788899 Breeding period of the arrow crab Stenorhynchus seticornis from Couves Island, south-eastern Brazilian coast Article in Journal of the Marine Biological Association of the UK · December 2002 DOI: 10.1017/S0025315402006598 CITATIONS READS 18 79 1 author: Valter Cobo Universidade de Taubaté 62 PUBLICATIONS 605 CITATIONS SEE PROFILE Some of the authors of this publication are also working on these related projects: Hermit crabs from Western Atlantic View project All content following this page was uploaded by Valter Cobo on 09 December 2015. The user has requested enhancement of the downloaded file. J. Mar. Biol. Ass. U.K. (2003), 83,979^980 Printed in the United Kingdom Fecundity of the arrow crab Stenorhynchus seticornis in the southern Brazilian coast O Claudia Melissa Okamori* and Valter Jose¤Cobo *Departamento de Biologia, Universidade de Taubate¤öUNITAU, Pc° a. Marcelino Monteiro, 63, 12030-010, Taubate¤,(SP)Brasil. E-mail: [email protected] O Departamento de Biologia, Universidade de Taubate¤öUNITAU, Pc° a. Marcelino Monteiro, 63, 12030-010, Taubate¤,(SP)Brasiland Group of Studies on Crustacean Biology, Ecology and CultureöNEBECC. E-mail: [email protected] The arrow crab Stenorhynchus seticornis (Brachyura, Majidae), is a common inhabitant of the rocky subtidal along the Brazi- lian coast. Fecundity and the in£uence of environmental variables on egg production are investigated in this study. Information on egg size and egg loss through incubation are also provided. Monthly samples were conducted using SCUBA diving, from January to December 1998 in the Ubatuba region (23825025@S^44852003@W), south-eastern Brazilian coast. Early broods were used for the estimation of size-speci¢c relationships of fecundity. Egg loss was assessed by comparing average egg numbers of early and late broods. The fecundity was estimated in 621.1 Æ339.6 eggs, with an average diameter of 0.48 Æ0.1 and 0.57 Æ0.1mm for early and late eggs, respectively. The number of eggs produced was apparently constant year-round. No signi¢cant di¡erences were recorded among monthly fecundity values. The variation of abiotic factors did not show any rela- tionship with temporal variability of fecundity, suggesting that the environmental e¡ect in egg production is slight at best. Preliminary studies on the fecundity of crustaceans showed a to the laboratory of Zoology at the Universidade de Taubate¤ö positive relationship between fecundity and size of the parental UNITAU. female (e.g. Hynes, 1954). In fact, the size of the breeding female At the laboratory, each ovigerous female was measured (cara- has been pointed out as a key variable determining the number pace width, CW) with a Vernier caliper, and sorted in 1-mm of eggs extruded per batch and, thus, the reproductive output of size-classes (CW). The egg mass of each ovigerous female was brachyuran females. The weight of the egg mass is usually detached from the pleopods and the eggs were counted under a constrained to about 10% of the female’s somatic weight, since dissecting microscope with a manual counter. A sub-sample of the space enclosed in the cephalotorax for the accumulation of ¢ve eggs was taken in each case and measured using a micro- yolk is limited (Hines, 1982). metric scale. Fecundity is commonly measured as the number of eggs Only counts of early eggs were used to estimate the size- produced in each egg batch, and is described as a function of speci¢c fecundity relationship to avoid underestimation due to body size (Corey & Reid, 1991). Yet, it is convenient to distin- egg loss. Both early and late broods were used to assess egg loss. guish fecundity estimates according to the stage of egg produc- For this, median values were compared using the analysis of tion, i.e. potential fecundity (number of oocytes stored in the variance (ANOVA) and the Student’s t-test parametric proce- ovaries), realized fecundity (number of extruded eggs attached) dures (Zar, 1999). and actual fecundity (number of larvae released) (Steachey & The embryonic development stages were determined Somers, 1995; Luppi, et al., 1997). according to Boolootian et al. (1959), but adapted to this species The arrow crab Stenorhynchus seticornis is commonly found in as follows: the shallow subtidal on rock bottoms, corals, calcareous algae, ö initial stage¼the egg is completely ¢lled with yolk; no sign and also on soft sediments, such as shelly gravel and sand. This of cleavage nor cellular di¡erentiation; species distribution is restricted to the western Atlantic from ö ¢nal stage¼the yolk is restricted to a reduced patch; the North Carolina (USA) to Argentina. It was reported from embryo is fully di¡erentiated, with clear segmentation of shallow waters to great depths (Melo, 1996). limbs and developed eyes. In spite of being a common inhabitant of hard bottoms, several aspects of its biology remain poorly studied. In this Average values of temperature and salinity were provided by paper, the realized fecundity of the arrow crab is examined for a the LabMet at the Instituto Oceanogra¤¢co da Universidade de population from the south-eastern Brazilian coast. The role of Sa‹ oPauloöUSP. The section of climatology of the Instituto temperature, salinity and luminosity is also assessed by sampling Agrono“ mico de CampinasöBase de Ubatuba, provided the over a 1-y-period. In addition, we also report information on light intensity data. The relationship between the seasonal varia- egg size and loss during incubation. This information may tion of fecundity and the variation of environmental factors was contribute to the understanding of the reproductive biology of tested using the Pearson’s coe⁄cient. The 5% statistical signi¢- the arrow crab in south-eastern Brazil. cance level was used. Monthly samples were obtained from January to December A total of 113 ovigerous females was measured, within an 1998 at Couves Island, Ubatuba, south-eastern Brazilian coast average size of 9.24 Æ1.52 mm CW, spanning eight size-classes, (23825025@S44852003@W). Crabs were collected by hand, using from 6.0 to 14.0 mm CW.The number of eggs ranged from 69 to SCUBA diving with a monthly catch-e¡ort of approximately 1850 eggs. From the whole sample, 95 and 18 ovigerous females 4 h. Each crab was packed in plastic bags and transferred frozen were found with initial and ¢nal broods, respectively. Journal of the Marine Biological Association of the United Kingdom (2003) 980 C.M. Okamori and V.J. Cobo Fecundity of the Stenorhynchus seticornis According to Bryant & Hartnoll (1995), the terminal moult precedes the ¢rst oviposition in Inachus dorsettensis (Pennant, 1777). It is characterized by a high moult increment compared to the juvenile moults, and the gonads only ripen after moulting. There is thus a delay between ecdysis and brooding. Due to the high energetic cost of the terminal moult, the resources allo- cated for reproduction are limited and, therefore, the ¢rst brood is typically smaller. The egg increase during embryogenesis, as observed for S. seticornis, is a result of water uptake, a common feature in brachyurans (Wear, 1974). The eggs of S. seticornis are relatively large if compared to Pinotheres ostreum (Say, 1817), which produces the smallest eggs within the Brachyura (0.25 mm), but similar to Figure 1. Box^whisker plot of the fecundity average related to the the size observed in Geryon fenneri Manning & Holthuis, 1984, crab size-classes. (0.56 mm) (see Hines, 1982). There is often an inverse relation- ship between size and number of eggs produced. The arrow crab S. seticornis produces large eggs and small clutches, a strategy directly related to the type of larval development. Choy (1988) points out that large eggs ensure a long incubation period and provide endogenous food resources for larvae, thus reducing early larval mortality. The authors are grateful to the Universidade de Taubate¤ö UNITAU, for the ¢nancial support (P# 251/2001-PRPPG) and the OMNI-MARE Dive Center, for the logistical facilities dur- ing the samples programmes. Our special thanks to Dr Itamar Alves Martins, for his assistance during the dive sessions. REFERENCES Figure 2. Relationship between egg number and crab size (carapace width). Boolootian, R.A., Farmanfarmaian, A. & Turcker, J., 1959. Reproductive cycles of ¢ve west coast crabs. Physiological Zo˛logy, 4, 213^220. Average fecundity for females carrying early embryos was Bryant, A.D. & Hartnoll, R.G., 1995. Reproductive investment 621.1 Æ339.6 eggs. The values of mean fecundity in each size- in two spider crabs with di¡erent breeding strategies. Journal class (Figure 1) and the regression analysis ¢tting the allometric of Experimental Marine Biology and Ecology, 188,261^275. model to data (E ¼1.27CW 2.7, r2 ¼0.43) (Figure 2), show a close Choy, S.C., 1988. Reproductive biology of Liocarcinus puber and relationship between size and fecundity, despite the relatively L. holsatus (Decapoda, Brachyura, Portunidae) from the low coe⁄cient of determination obtained. Gower Peninsula, South Wales. Marine Ecology, 9, 227^241. Average number of eggs in ¢nal clutches was 474.61 Æ236.7, Corey, S. & Reid, D.M., 1991. Comparative fecundity of which did not di¡er signi¢cantly from initial clutches (Student’s decapod Crustacean. I. The fecundity of thirty-three species t-test, P40.05). Yet, the average number of eggs in early egg of nine families of caridean shrimp. Crustaceana, 60, 271^293. batches was 23% higher than the mean number of eggs in late Hines, A.H., 1982. Allometric constraints and variable of repro- ductive e¡ort in brachyuran crabs. Marine Biology, 69,309^ ones. 320. During the sampled period, no di¡erences were found among Hynes, H.B.N., 1954.