Limb Autotomy, Epibiosis On Embryos, And Brooding Care In

J. Mar. Biol. Ass. U.K. (2003), 83, 1015^1022 Printed in the United Kingdom

Limb autotomy, epibiosis on embryos, and brooding care in the crab Cyrtograpsus angulatus (Brachyura: Varunidae)
Paola Silva*, T ¤ s A. Luppi*O and Eduardo D. Spivak* oma
*Departamento de Biolog|¤ a, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, Casilla de Correos 1245, 7600 Mar delPlata, Argentina. OCorresponding author, e-mail: taluppi@mdp.edu.ar

The e¡ects of the multiple autotomy on epibiosis infestation on embryos, on the survival of embryos, and on brooding care behaviour were examined in females of Cyrtograpsus angulatus, a south-western Atlantic intertidal and subtidal crab. The population of C. angulatus in Mar Chiquita, a coastal lagoon, presents a highincidence of limb autotomy. Newly laid embryos of both healthy and autotomized females were immediately colonized by bacteria and ¢lamentous fungi, peritrichid ciliates, and few small animal species, while detritus was accumulated. The periphery of the embryo mass was more infested by epibionts and accumulated more detritus than the central region. Multiple autotomy in female C. angulatus increased theepibiosis and detritus accumulation in embryos and pleopods, decreased the chance of embryos to complete their development. The following behaviours related to brooding care were observed in both healthy and autotomized females: standing, chela and pereiopod probing, abdominal £apping, pleopod beating and maxilliped beating. However, the time devoted to standing and abdominal £apping wassigni¢cantly higher in healthy and autotomized females, respectively. Brooding care behaviour in nonovigerous females and in females with early and late embryos, suggests the presence of di¡erent signalling systems that trigger them. We propose that multiple autotomy modi¢es brood care, decreases the success of embryonic development and, consequently, reduces the contribution of autotomized females(approximately 30% of the potentially reproductive females of C. angulatus in Mar Chiquita) to the following generation.

INTRODUCTION
New surfaces of crustaceans such as postmoult cuticle, recently extruded embryos, are colonized by epibionts that may interfere with sensory, respiratory, locomotive and reproductive activities: bacteria, unicellular algae, fungi, protozoans, small metazoans, and larvaeof larger animals (Bauer, 1989). Crab embryos develop beneath the female abdomen, attached to pleopods and water circulates through the brood mass, which acts like a ¢lter for accumulating debris (Bauer, 1979). Fisher (1976, 1977, 1983a) suggested that epizoic microorganisms restrict gaseous exchange across the embryonic surface or utilize the necessary oxygen for embryo development. In bothcases, embryos could be asphyxiated. Decapods show structures for grooming and cleaning the embryo mass, and speci¢c behaviours, that decrease the e¡ect of fouling (Bauer, 1989). Several speci¢c behaviours of brooding female crabs, such as abdominal £apping and reverse gill ventilation, are used to ventilate, clean, provide oxygen, and eliminate metabolites produced by embryos, and the occurrence ofthese behaviours increases throughout embryonic development (Wheatly, 1981; de Vries et al., 1991; Naylor et al., 1999; ¤ Fernandez et al., 2000; Forster & Baeza, 2001; Baeza & « ¤ Fernandez, 2002; Ruiz-Tagle et al., 2002). Some of these authors considered that brood care in crabs is a case of parental care. Parental care is an evolutionary response of species whose early stages of life aresubjected to environments with extreme physical characteristics, to
Journal of the Marine Biological Association of the United Kingdom (2003)

microbial infestations, to intra- and inter-speci¢c high predation, and/or to an intense competence for resources (Clutton-Brock, 1991). Adults of Cyrtograpsus angulatus (Dana, 1851), a common South American coastal crab, are usually found in tidal £ats of...