Population features of the western Atlantic hermit crab Pagurus exilis (Anomura, Paguridae) in Brazil

Abstract

The population structure of the hermit crab Pagurus exilis has been studied in Caraguatatuba region (23 o 34’ and 23 o 51’S; 45 o 10’ and 45 o 26’W), northern coast of Sao Paulo, Brazil for the first time in terms of total and seasonal size frequency distribution, sex ratio and reproductive season. The animals were monthly collected during two consecutive years (2001/2003) with a fishery boat equipped with “double rig” nets. At the laboratory, the specimens were identified, counted, weighed and measured. A total of 1,963 animals were captured, which 1,372 were males and 591 females (311 non ovigerous females and 280 ovigerous ones). The size of animal (Cephalothoracic Shield Length) ranged from 2.4 to 8.3 mm, and males were significantly larger, showing a sexual dimorphism. The size frequency distribution showed an unimodal pattern with non-normal distribution. The total sex ratio was significantly different from the expected, biased to males (1:0.43). Most ovigerous females presented eggs in initial developmental stage, with a few percentages in intermediary and final stages. The profile found an abundant population with a continuous reproduction (ovigerous females occurring along the year).