Growth, sexual maturity and sexual dimorphism of Aegla georginae (Decapoda: Anomura: Aeglidae) in a tributary of the Ibicuí River in southern Brazil

Carlos Eduardo Copatti,Rosemari Parise Legramanti,Sandro Santos,André Trevisan

doi:10.1590/s1984-4689zool-20160010

Abstract

This study aimed to estimate the growth and size at the onset of sexual maturity in a population of Aegla georginae . Specimens were sampled from November 2007 to October 2008 in the Perau Creek (Ibicui-Mirim sub-basin; Uruguay River basin). All captured specimens were sexed, and their cephalothoracic length (CL), minor and larger propodi length (MPL, LPL, respectively), height of major chela (HMQ), and abdomen width (AW) were measured. The lengthwise growth of males and females was evaluated using the Bertalanffy model, and the morphological sexual maturity was evaluated using the REGRANS program. The smallest ovigerous female presented a 10.45 mm CL. Males reached larger sizes than did females, but the growth rate was similar between the sexes. Longevity estimates for males and females were 670 and 736 days, respectively. The best relationship used to infer the size at morphological sexual maturity in males was CLxHMQ (12.78 mm) and in females was CLxAW (10.78 mm). Aegla georginae follows a common pattern for aeglids in terms of lifecycle, where sexual dimorphism is associated with the onset of morphological sexual maturity.

Highlights

Species of Aegla Leach, 1820 have a lifecycle that is entirely restricted to freshwater environments and is the only taxon of Anomura with this profile (Bond-Buckup et al 2008, Fernandes et al 2013)
Previous studies have contributed to the understanding of the population dynamics in species such as Aegla platensis Schmitt, 1942 (Bueno et al 2000); Aegla castro Schmitt, 1942 (Swiech-Ayoub & Masunari 2001); Aegla leptodactyla Buckup & Rossi, 1977 (Noro & Buckup 2003); Aegla jarai Bond-Buckup & Buckup, 1994 (Boss et al 2006); Aegla longirostri Bond-Buckup & Buckup, 1994 (Silva-Castiglioni et al 2006); Aegla italacomiensis Bond-Bu ckup & Buckup, 1994 (Silva-Gonçalves et al 2009); and Aegla manuinflata Bond-Buckup & Santos, 2009 (Trevisan & Santos 2011)
Considering the importance of body growth and the onset of morphological sexual maturity for understanding aeglid biology, we propose to study these parameters in Aegla georginae Santos & Jara, 2013, a threatened species of southern Brazil (Santos et al 2013)

Summary

Introduction

Species of Aegla Leach, 1820 have a lifecycle that is entirely restricted to freshwater environments and is the only taxon of Anomura with this profile (Bond-Buckup et al 2008, Fernandes et al 2013). Body growth can be represented by a curve that corres ponds to the dimensions of an individual measured over time or, more often, by means of the partial or total population (Margalef 1977). This curve is of great importance because it provides information regarding the maximum size, the age when this size is achieved and the growth rate of individuals (Valenti et al 1987). Sexual dimorphism in the width of the abdomen is not found in other groups of Anomura (Trevisan et al 2012)

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