Relative growth and reproduction in Achelous spinicarpus (Crustacea: Portunidae) on the south-eastern continental shelf of Brazil

Abstract

This investigation aimed to study the relative growth, morphological sexual maturity and fecundity of the swimming crab Achelous spinicarpus in a tropical region, on the south-eastern continental shelf of Brazil (258S). Biometry of all specimens was conducted, including measurements of the cephalothorax, cheliped, abdomen and gonopods. Relative growth was described based on the equation for allometry (y ¼ ax b ), and size at sexual maturity was determined from inflections in relations involving the cheliped, gonopods (males), and abdomen (females), as dependent variables, related to the cephalothorax width (independent variable). Fecundity was estimated by the gravimetric method. The relations of the length of the chelar propodus and carpal spine to the carapace width without the lateral spines (CW) showed positive allometry in both sexes, with a significant variation in the constant 'b' for males between the developmental stages (juvenile and adult) and the size at maturity estimated at 37 mm CW. In females, the abdomen was most appropriate for the estimate of morphological maturity, which occurred at a smaller size (32 mm CW), with a change in the growth pattern between the stages, passing from isometric (juveniles) to positive allometric (adults). The gonopods also showed different growth rates between developmental stages, in synchrony with the variables of the cheliped. Mean fecundity for the species was 53,984 eggs, with a positive correlation between the number of eggs exteriorized and the size of the female; the equations allowed interconversion between these variables, due to the adjustment of the power function (r 2 ≥ 86%).

Reproductive biology of the commercially exploited kolibri shrimp, Solenocera agassizii (Decapoda: Solenoceridae), from the Pacific coast of Costa Rica, with considerations for its management

“…Histology is typically used to determine the size at physiological maturity (SPM) through the analysis of primary sexual characters, where microscopic changes in gonad tissues are associated with macroscopic gonad development (McQuaid et al, 2006;Li et al, 2012). In addition to the fact that the determination of SPM is not a trivial process, physiologically mature individuals may not be functionally able to mate due to small body size or the underdevelopment of body parts (sexual secondary characters) that are engaged in the mating process (McQuaid et al, 2006;Pardal-Souza, & Pinheiro, 2013: Queirós et al, 2013. Therefore, the examination of the primary sexual characters alone could lead to an imprecise estimation of SOM (Bell, Redant, &Tuck, 2006;MacDiarmid & Saint-Marie, 2006).…”

Slipper lobsters (Scyllaridae) off the southeastern coast of Brazil: relative growth, population structure, and reproductive biology

“…8 (Golden Software, Golden, CO). We adopted the TL as the size indicator for the hooded slipper lobster, as was done in previous studies of lobsters of the genus Scyllarides (Hearn, 2006;Pessani and Mura, 2007). The relative growth of each sex was assessed by a regression analysis of the empirical points for morphometric relationships given by the power function y=ax b , and then a t-test was used to check for possible differences in allometry (Huxley, 1950).…”

“…Therefore, the linearized data (lny=lna+[b×lnx]) for each relationship were assessed with the segmented library (Muggeo, 2008) in R (vers. 2.13.0) to identify significantly different growth rates during ontogeny, according to procedures used by Pardal-Souza and Pinheiro (2012). This method of regression analysis seeks to partition the independent variable into intervals at break points, separating line segments that are fitted to each interval.…”

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

“…body size), growth rate can be obtained by allometric coefficient ('b' constant), generating an isometry (b=1) or allometry (positive b>1 and negative b<1). Such growth patterns are specific to each species and vary as a function of development phase of each sex (juvenile and adult), generating two discontinuous phases of growth and consequently two different levels of allometric coefficients that define the moment of the morphological sexual maturity in decapods Fransozo 1998, Pardal-Souza andPinheiro 2013).…”