Long-term study of the life cycle and growth of Heleobia australis (Caenogastropoda, Cochliopidae) in the Bahía Blanca estuary, Argentina

Mc Carcedo,Sm Fiori

doi:10.7773/cm.v38i4.2079

Abstract

The life cycle and growth of the mud-snail Heleobia australis was studied in the Bahía Blanca estuary (Argentina) from April 2008 to April 2010. Four age classes were identified. This species recruits once a year, during summer. In general, the recruits (< 2.5 mm) represented a small percentage of the total population. The growth rate of H. australis declined with increasing animal size and showed a marked seasonal pattern for the population under study: lower rate during winter and higher rate in summer. A life cycle of approximately 30 months (~2.5 years) was estimated for the population of H. australis in the Bahía Blanca estuary. This population shows variations in growth rate, abundance of recruits, and shell size in relation to more northerly populations. Several factors like parasitism, predation, environmental features, and anthropogenic action may be interacting to produce these differences. This work constitutes the first long-term study of the life cycle of cochliopids. Heleobia australis appears to be a long-lived species and exhibits variations in its life cycle that seem to be influenced by biological and physical variables. Long-term studies that include biological interactions and spatial features of the microhabitats are needed to elucidate patterns in life-history traits of H. australis along its distribution range.

Highlights

Heleobia australis (d’Orbigny 1835) is an intertidal gastropod that inhabits low-energy coastal environments such as estuaries and coastal lagoons
We aim to estimate the number of breeding seasons, life cycle, and growth parameters of the population of H. australis in the Bahía Blanca estuary and compare this information with parameters reported for other populations located along its distribution range
The population of H. australis showed a marked seasonal growth pattern: lower rate during the cold season and higher rate during the warm season. This is similar to the seasonal pattern described by De Francesco and Isla (2004) for the H. australis population in the Mar Chiquita lagoon

Summary

Introduction

Heleobia australis (d’Orbigny 1835) is an intertidal gastropod that inhabits low-energy coastal environments such as estuaries and coastal lagoons This species has a wide distribution range that extends from southeastern Brazil to northeastern Patagonia, Argentina (22o–64o S) (Gaillard and Castellanos 1976, Aguirre and Farinati 2000). It is associated with mixohaline and hyperhaline conditions (Aguirre and Farinati 2000, Aguirre and Urrutia 2002, De Francesco and Isla 2003, Canepuccia et al 2007) and dominates, in terms of abundance and biomass, the macrobenthic community of estuaries and coastal lagoons (Gonçalves et al 1998, Carcedo and Fiori 2011).

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