Marine Biology

, Volume 151, Issue 5, pp 1875–1886 | Cite as

Gonopore sexing technique allows determination of sex ratios and helper composition in eusocial shrimps

  • Eva TóthEmail author
  • Raymond T. Bauer
Research Article


An evaluation of the social organization and sexual system of eusocial species of Synalpheus has been hindered because it has not been possible to determine the sexual composition of colony helpers (workers). The external sexual characters typically used to sex caridean shrimps are lacking in Synalpheus. We used SEM sexing technique to determine the sexual composition of helpers in colonies of Synalpheus regalis, S. rathbunae, S. chacei, S. rathbunae A (see Morrison et al. Mol Phylogen Evol 30:563–568, 2004), and S. filidigitus. Colonies consisted of both sexes and sex ratios of helpers generally conformed to 50:50 female to male. Females were characterized by gonopores with U-shaped slits on the coxae of the third pereopods (first walking legs) while males had oval gonopore openings on the coxae of the fifth pereopods (third or last walking legs). In S. chacei, S. filidigitus, and S. rathbunae A, a few helpers were found that had both male and female gonopores (intersexes). All three reproductive females (queens) of S. filidigitus examined were intersexes. Sexing of helpers allowed us to test some hypotheses about sexual differences in helper morphology that might indicate task specialization (division of labor). Male helpers were not different from female ones in body size (except in S. regalis: males somewhat larger) and in fighting chela size. The lack of sexual dimorphism in these characters suggests no male–female specialization in colony tasks such as defense. The presence of male and female helpers similar in size suggests that the sexual system of these eusocial species is gonochoristic, although protandry of some sort in S. filidigitus can not be ruled out. The intersexuality observed in a few individuals may be due to developmental anomalies, protandry, or even simultaneous hermaphroditism. Finally, the sexing technique allowed us to establish that new colonizers of unoccupied sponges in S. rathbunae are a single male and female of helper size.


Sponge Ejaculatory Duct Sexual System Reproductive Male Eusocial Species 
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We gratefully acknowledge use of facilities at the University of Louisiana at Lafayette’s (ULL) Electron Microscopy Center and help from its Director, Dr. Thomas Pesacreta and his assistant Anne Hume. We also thank J. Emmett Duffy for providing us with individuals of colony 1 of S. chacei to analyze, and the Fisheries Department of the Virginia Institute of Marine Science for letting us use their measuring equipment. This research was supported by the Marine Science Network Fellowship of Smithsonian Institute and the Smithsonian Tropical Research Institute (to ET). We thank JE Duffy, M Thiel and a third anonymous reviewer for their helpful comments and suggestions. This is contribution no. 791 from Caribbean Coral Reefs Ecosystem program (supported in part by the Hunterton Oceonographic Research Fund), and no. 113 of the ULL Laboratory of Crustacean Research. Sample collection complies with the current laws of both Belize and Panama, and collection permits were obtained from the Belizean department of Fisheries and ANAM in Panama.


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Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  1. 1.Smithsonian Tropical Research Institute, Unit 0948APO AAUSA
  2. 2.Department of BiologyUniversity of Louisiana at LafayetteLafayetteUSA

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