Ecological implications of allometric growth in Brachyurans: Data from Uca Tangeri resident in a West African mangrove swamp

Abstract

A survey was carried out on the fiddler crabs present in a small naturally defined mangrove swamp in the upper Bonny Estuary of the Niger Delta (S. Nigeria), the purpose of which was to study the ecological significance of the claws of the Ocypodidae crab, Uca tangeri (Eydoux, 1835). Previous studies on the size of the claws of crabs generally have focused on their use in foraging. In the present investigation, the use of claws in reproduction provides further support to the view that evolution of crab chelae (claws) is not driven by feeding requirement alone. Mating pairs collected in the field showed that > 75% of mating males had chelae above the average size of the male population as a whole. Maintenance costs for cheliped in Uca tangeri estimated by respirometry were not significantly different from other body tissues as oxygen uptake could be predicted solely from dry tissue weight. Moreover, the rate of oxygen uptake was independent of the proportion of the total body weight that could be contributed by the chelipeds. Changes in the allometry of various dimensions at sexual maturity was observed in U. tangeri and suggests a sexual role in the crab.

KEYWORDS: Relative growth, Uca tangeri; Claw size, Bonny Esturary.