Population structure, relative growth and morphological sexual maturity of the snapping shrimp Alpheus brasileiro Anker, 2012 (Caridea: Alpheidae) from the south-eastern coast of Brazil

Abstract

The present study investigated the population structure of the snapping shrimp Alpheus brasileiro. We tested the hypotheses that the sex ratio of the population differs from the expected 1:1 and that the growth pattern differs between adults and juveniles and between sexes. Reproductive period, juvenile recruitment and morphological sexual maturity were estimated. Samples were collected in two periods. The first sampling occurred bimonthly from March 2013 to January 2014. The second sampling occurred monthly from April 2015 to March 2016. The population structure was determined based on the size-frequency distribution of different demographic categories. To analyse the relative growth, we measured the second pleuron length, major cheliped propodus length, major cheliped propodus width, major cheliped propodus height, appendix interna length, appendix masculina length. The results showed that the sex ratio did not differ from 1:1 (male:female). Reproduction and juvenile recruitment were continuous throughout the study period. The analysis of relative growth confirmed the hypothesis that males and females, and juveniles and adults, have different growth patterns, indicating distinct strategies of energy allocation. The estimated carapace length at the onset of morphological sexual maturity was 4.9 mm in males and 4.7 mm in females. The results obtained in this study are probably related to the monogamous social behaviour of A. brasileiro. Monogamy can influence demographic parameters such as sex ratio and the size at which males and females reach morphological sexual maturity.

Growth, age at sexual maturity, longevity and natural mortality of Alpheus brasileiro (Caridea: Alpheidae) from the south-eastern coast of Brazil

“…Our results regarding the growth parameters and longevity are consistent with the estimates of the morphological sexual maturity obtained through the use of the relative growth method (Pescinelli et al, 2018a). With this method it was estimated that males reach the sexual maturity at a slightly larger size (4.9 mm CL) than the females (4.7 mm CL).…”

“…Previous studies investigated the biology of A. brasileiro analyzing egg production and social monogamy (Pescinelli et al, 2017a), relative growth (Pescinelli et al, 2018a) and showed that males and females have different relative growth, and that reproduction and recruitment are continuous. The morphology of early larval stages was also analyzed, and led to the conclusion that A. brasileiro has an extended larval development in the plankton (Pescinelli et al, 2017b).…”

“…The age at maturity was calculated using the information of the size at the onset of functional maturity of females and the morphological maturity of males and females. The size at the onset of morphological maturity used in the calculations (4.9 and 4.7 mm CL for males and females, respectively) was estimated in a previous study that addressed the structure and relative growth of the same population (Pescinelli et al, 2018a).…”

“…The differential growth between males and females can be explained by different energy allocation strategies. While males invest in growth and, especially, in the development of structures related to agonistic behavior, i.e., territory defense, competition for females, and defense against predators, females invest energy into reproduction, i.e., in the gonadal development and production and maintenance of eggs (Correa and Thiel 2003;Bauer, 2004;Pescinelli et al, 2018a).…”

Relative growth, sexual maturity and handedness in the ghost shrimp <em>Callichirus major</em> (Decapoda: Callianassidae) from the southwestern Atlantic

“…Heterochely, here defined as different-sized chelipeds, is a common attribute in most decapods (e.g. Aegla franca Schmitt, 1942: Bueno andShimizu 2009;Alpheus brasileiro Anker, 2012: Pescinelli et al 2018Platyxanthus crenulatus [Milne-Edwards, 1879]: Laitano et al 2013), including members of the family Callianassidae Dana, 1852 (collectively known as ghost shrimps). Adult males of callianassids invariably develop one hypertrophied cheliped (heterochely), while females and juveniles have subequal or homochelous chelipeds (Hernáez 2018 and references therein).…”