Population dynamics of the pea crab Austinixa aidae (Brachyura, Pinnotheridae): a symbiotic of the ghost shrimp Callichirus major (Thalassinidea, Callianassidae) from the southwestern Atlantic

Douglas F Peiró,Fernando L Mantelatto

doi:10.1590/s0073-47212011000100001

Douglas F Peiró, Fernando L Mantelatto

Open Access

https://doi.org/10.1590/s0073-47212011000100001

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Journal: Iheringia. Série Zoologia	Publication Date: Jun 1, 2011
Citations: 36	License type: cc-by

Affiliation: Universidade de São Paulo

Abstract

The Pinnotheridae family is one of the most diverse and complex groups of brachyuran crabs, many of them symbionts of a wide variety of invertebrates. The present study describes the population dynamics of the pea crab Austinixa aidae (Righi, 1967), a symbiont associated with the burrows of the ghost shrimp Callichirus major (Say, 1818). Individuals (n = 588) were collected bimonthly from May, 2005 to September, 2006 along a sandy beach in the southwestern Atlantic, state of São Paulo, Brazil. Our data indicated that the population demography of A. aidae was characterized by a bimodal size-frequency distribution (between 2.0 and 4.0 mm and between 8.0 and 9.0 mm CW) that remained similar throughout the study period. Sex ratio does not differ significantly from 1:1 (p > 0.05), which confirms the pattern observed in other symbiontic pinnotherids. Density values (1.72 ± 1.34 ind. • ap.-1) are in agreement with those found for other species of the genus. The mean symbiosis incidence (75.6%) was one of the highest among species of the Pinnotheridae family, but it was the lowest among the three studied species of the genus. Recruitment pattern was annual, beginning in May and peaking in July, in both years, after the peak of ovigerous females in the population (from March to May). Our findings describe ecological and biological aspects of A. aidae similar to those of other species of this genus, even from different geographic localities.

Highlights

-1 confirms the pattern observed in other symbiontic pinnotherids
Austinixa Heard & Manning, 1997 species are found on sandy beaches and own peculiar ecological features, such as the symbiotic life with thalassinoid crustaceans of the Callichirus major (Say, 1818) complex or with few ecologically equivalent species (HEARD & MANNING, 1997; HARRISON, 2004), where they inhabit the upper portion of the host’s burrows (MANNING & FELDER, 1989) and shelter near the entrance of these structures
Studies that investigate the ecology of the sandy beaches indicate that the pinnotherid crabs from the Austinixa genus (= Pinnixa) are the frequent dominant infauna of the Americas (MANNING & FELDER, 1989; SOUZA & GIANUCA, 1995)

Summary

Introduction

-1 confirms the pattern observed in other symbiontic pinnotherids. Density values (1.72 ± 1.34 ind. ap. ) are in agreement with those found for other species of the genus. O presente estudo descreve a dinâmica populacional do caranguejo pinoterídeo Austinixa aidae (Righi, 1967), um simbionte que vive associado às galerias do “corrupto” Callichirus major (Say, 1818). Pinnotheridae pea crabs (Brachyura) are typically small and symbiotic of a wide variety of benthonic invertebrate hosts (SCHMITT et al, 1973; WILLIAMS, 1984; HARRISON & HANLEY, 2005). Pinnotherid crabs are widely distributed along the marine coastal habitats of almost all oceans (SCHMITT et al, 1973; MARTINS & D’INCAO, 1996) Despite their ecological importance and their great diversity, the information about the population demography of the pea crabs is still scarce, especially about those species that inhabit the Atlantic coast of the Americas. Austinixa aidae (Righi, 1967) has been reported as a symbiont of C. major, a callianassid shrimp that inhabits

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