Sex change and reproductive output of the protandric shrimp Merguia rhizophorae (Rathbun, 1900) (Decapoda, Merguiidae)

ABSTRACT

The aim of this study was to confirm the type of protandry adopted by M. rhizophorae and to describe the size at which sex change occurs in order to test predictions of sex allocation theory. The reproductive output also was investigated, based on fecundity and embryo volume. Specimens were collected cohabiting burrows built by mud shrimps Upogebia omissa in an estuary region in the northeast of Brazil. The body size (carapace length, CL) and sex of the shrimps were recorded. Observations were made developmental stages of the embryos, fecundity, and embryo volume. A total of 204 M. rhizophorae individuals was sampled, of which 170 (83.3%) male phase (MP) and 34 (16.7%) female phase (FP) individuals. The body size (mean ± SD) of the individuals in the MP was smaller than in the FP: 3.91 ± 0.78 and 6.18 ± 0.52 mm CL, respectively. The size at which 50% of the shrimps changed to FP (CL₅₀) was 5.62 ± 0.01 mm CL. Reproductive output (fecundity and embryo volume) increased linearly with shrimp body size. An increase in embryo size during development and the loss of embryos during final stage of development were recorded. In this study, the behaviour exhibited by M. rhizophorae (share a burrow with another shrimp species) was recorded for the first time, expanding knowledge about the ecology of this semi-terrestrial shrimp. Our results indicate the adoption of strict protandric hermaphroditism by M. rhizophorae. Our study supports the prediction of sex allocation theory that sex ratio is significantly biased towards the first-sex in sequential hermaphrodites. We also found evidence of possible trade-offs between the size in which the sex change occurs and the reproductive strategy exhibited by M. rhizophorae.

KEYWORDS:

• Hermaphroditism
• k-strategy
• protandry
• reproductive investment
• symbiosis

Acknowledgements

The authors are grateful to Dr. Paulo Eugenio Alves Macedo de Oliveira (Institute of Biology, Federal University of Uberlândia) for allowing the use of her laboratory. RCC thanks the Brazilian National Council for Scientific and Technological Development – CNPq (Scholarship PQ-CNPq number 306672/2018-9). The authors are also grateful to the reviewer PhD. Martin Thiel, who contributed with valuable comments and suggestions, improving the present manuscript. All sampling in this study was conducted according to applicable state and federal laws.

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Funding

The author(s) reported there is no funding associated with the work featured in this article.