Population biology and sexual dimorphism in the freshwater prawn Atya scabra (Decapoda: Atyidae) in the De Contas River, Bahia, Brazil

Abstract

Abstract. Introduction: Crustaceans have economic and ecological importance and the role of caridean crustaceans in lentic environments is crucial to maintain the trophic structure. The species Atya scabra is occasionally associated with fisheries, especially in Northeast and Northern Brazil. Objective: To determine the population structure, reproductive period, patterns of growth and distribution of size classes among sexes in a population of the prawn A. scabra in the De Contas River, Bahia, Brazil. Methods: Individuals were sampled in a period of one year by passing sieves through marginal vegetation and using dragnets. In the laboratory, we recorded the sex of the individuals and measured them using a pachymeter with 0.001 mm precision. The dimensions measured were CL (carapace length), TL (total length) and CW (carapace width). In order to analyze data, linear models for the relationships CL × CW were constructed and the type of allometry for each sex was determined. Individuals were grouped into size classes of 5 mm intervals. A chi-square test (χ2) was used to test deviation from the 1:1 sex ratio. The proportion of ovigerous females was registered for each month to determine the breeding period. Results: A total of 517 individuals were collected, 328 were males and 186 females of which 169 were ovigerous. Males showed a polymodal distribution in size classes and were significantly larger than females, which presented a unimodal distribution in size classes. The observed growth patterns demonstrated that both sexes present negative allometry. However, sexual dimorphism was detected when comparing the growth parameters. Ovigerous females were sampled the entire year and size-frequency data demonstrated that recruitment also occurs throughout the year, which allowed us to classify their reproduction as continuous. Conclusions: Our data is essential to draw sustainable fishery management strategies. We suggest a minimum capture size of 70 mm and capture restrictions from May to August.
 Key words: ecology; freshwater; limnology; conservation; morphometry.

Relative growth and sexual dimorphism in the hermit crab Clibanarius signatus Heller, 1861 (Anomura, Diogenidae) from the northern coast of the Persian Gulf, Iran

“…However, in the population, the males had the biggest ones and the intersex individuals showed a tendency to present intermediate sizes between males and females. Males having larger body size is common among crustaceans (de Barros et al, 2020;Noori et al, 2015;Öndes et al, 2017) as well as hermit crabs. The results are in line with those reported in other hermit crabs, such as Calcinus tibicen (Fransozo and Mantelatto, 1998), Loxopagurus loxochelis (Mantelatto et al, 2002), Petrochirus diogenes (Turra et al, 2002), Diogenes moosai, D. lopochir, C. infraspinatus (Teoh and Chong, 2015), Isocheles sawayai (Fantucci et al, 2009), Dardanus insignis (Branco et al, 2002), C. antillensis, C. sclopetarius, and C. vittatus (Turra and Leite, 2000) that males are heavier and larger than females.…”

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“…Menurut Annawaty (2010), ukuran tubuh M. pilimanus kecil yaitu sekitar 3-5 cm. Menurut de Barros et al (2020), udang jantan umumnya memiliki ukuran lebih besar daripada betina karena pola pertumbuhan udang jantan lebih ke arah perkembangan struktur dan perilaku seksual Udang yang ditemukan didominansi oleh udang betina dengan ukuran yang kecil. Menurut Ukagwu et al (2021), udang betina memiliki rentang hidup yang pendek atau lebih cepat mati.…”