Early Developmental Sequences of Aratus pisonii (H. Milne Edwards) (Brachyura, Grapsidae) under Laboratory Conditions

Abstract

The larval development of the mangrove tree crab Aratus pisonii can exhibit three different sequences when reared under different salinity conditions, using larvae and water obtained from marine and estuarine environments. Such sequences consist of the suppression of one and occasionally two zoeal stages prior to metamorphosis. The occurrence of these sequences and their duration does not appear significantly affected by the origin of larvae or-water used, neither by the rearing conditions (e.g., food, temperature, salinity and photoperiod). The adoption of any particular developmental sequence is interpreted as a tendency to increase fitness through developmental plasticity, consequently as an evolutionary trend of the species towards an optional reduction of its pelagic life. This allows some flexibility of response to the varying environmental conditions but it does not constitute an adaptation to any particular habitat because the occurrence of the sequences did not prove to be significantly affected by common environmental parameters.