Population structure of Aegla grisella Bond-Buckup & Buckup, 1994 (Crustacea, Aeglidae) from Perau de Janeiro, Arvorezinha, RS, Brazil.

Abstract

The species Aegla grisella Bond-Buckup & Buckup, 1994 is included in the list of the threatened species of Rio Grande do Sul, as VU, according to the IUCN. The aim of this research was describe the population dynamics of A. grisella, through the definition of the reproductive period, distribution in size classes, abundance and monthly distribution for sexes. From August /14 to July/15 were collected specimens of A. grisella in an affluent of Forqueta´s river. Were obtained measurements of the cephalothorax length (CC), and the sexing was done observing the presence of pleopod. Were sampled 1377 specimens of A. grisella. The CC (mm) varied from 5,08 to 36,14 (x=13,5 ± 5,57) in males; 4,19 a 37,96 (x=15,4 ± 5,07) in females; 12,46 a 35,49 (x=20,3 ± 5,32) in ovigerous females. According to CC, the female were significantly bigger than males (p<0,0001). With respect to the sexes, were observed fluctuations throughout the year, but both were more frequently on spring and summer. The sex ratio were 0,9:1 male/female, without significant difference (X² = 7,122; p = 0,6244). The abundance was unimodal for both sexes, with the size class of 12-14 mm most frequent for males and 14-16 mm for females. A unsignificant tendency occurs (G = 12,9811; p = 0,1635), from a bigger abundance of males in inferior size classes and female in superior size classes. Ovigerous female were more abundant on Spring and juvenile were more abundant in Autumn and Winter.