The Enigmatic Life History of the Symbiotic Crab Tunicotheres moseri (Crustacea, Brachyura, Pinnotheridae): Implications for Its Mating System and Population Structure

Abstract

Resource-monopolization theory predicts the adoption of a solitary habit in species using scarce, discrete, and small refuges. Life-history theory suggests that temporarily stable parental dwellings favor extended parental care in species that brood embryos. We tested these two predictions with the symbiotic crab Tunicotheres moseri. This species exhibits abbreviated development and inhabits the atrial chamber of the scarce, structurally simple, long-lived, and relatively small ascidian Phalusia nigra in the Caribbean. These host characteristics should favor a solitary habit and extended parental care (EPC) in T. moseri. As predicted, males and females of T. moseri inhabited ascidians solitarily with greater frequency than expected by chance alone. The male-female association pattern and reverse sexual dimorphism (males < females) additionally suggests a promiscuous "pure-search" mating system in T. moseri. Also in agreement with theoretical considerations, T. moseri displays EPC; in addition to embryos, females naturally retain larval stages, megalopae, and juveniles within their brooding pouches. This is the first record of EPC in a symbiotic crab and the second confirmed record of EPC in a marine brachyuran crab. This study supports predictions central to resource-monopolization and life-history theories.

Host-use pattern of the shrimp Periclimenes paivai on the scyphozoan jellyfish Lychnorhiza lucerna: probing for territoriality and inferring its mating system

“…Also, in P. paivai, sex specific differences in mortality rates by predators, driven by a greater propensity of males (compared to females) to switch among host individuals (see above), could lead to the observed sex ratio being skewed towards females in the population. Female-skewed sex ratios have been reported before in other symbiotic and free-living crustaceans in which males frequently roam among hosts in search of receptive females [12,61]. By contrast to that reported for P. paivai, the sex ratio is hardly ever skewed in favor of females in populations of symbiotic crustaceans that do not or rarely switch among host individuals, and that exhibit a monogamous mating system [15,26,31].…”

Host use pattern of the pea crab Afropinnotheres monodi: potential effects on its reproductive success and geographical expansion

“…That is, the dominance of solitary guest crabs in this population of A. monodi suggests that the selection of the host in this species tends to be random (opportunity-related) and, consequently, the occasional pairs observed inside hosts were accidental and transitory. This host monopolisation is an efficient adaptation (more benefits than costs) to hosts with small body size and/or low morphological complexity (Baeza & Thiel 2003, 2007Hernández et al 2012), as the host bivalves in this study. In fact, mussels, the host that harboured mainly soft females, showed fewer female-female pairs than expected by chance.…”

“…From all the above-mentioned, pea crabs are considered an exceptionally interesting group to explore the different types of behavioural, phenotypic and genetic adaptations of symbionts, during the evolution process toward complex parasitic cycles (Grove et al 2000;Jossart et al 2013). Despite the increasing interest in host use and mating behaviour of pinnotherids in recent years (De Bruyn et al 2009, 2010Hernández et al 2012;Ocampo et al 2012;Jossart et al 2013;Peiró et al 2013), several aspects of their complex lifestyle are still unknown (Becker & Türkay 2010).…”

Reproductive traits of the symbiotic pea crab Austinotheres angelicus (Crustacea, Pinnotheridae) living in Saccostrea palmula (Bivalvia, Ostreidae), Pacific coast of Costa Rica

“…Since the host plays a fundamental role in the life cycle of the pea crab, it seems necessary to get a better understanding of the interactions between population dynamics of the host and adaptive responses of the symbiotic pea crab. Hernández et al (2012) assumed that small host populations induce pea crabs to adopt a solitary life style, and predicted that stable dwellings stimulate extended parental care. Moreover, the larval phase and recruitment processes are unknown in Austinotheres angelicus , and it has been speculated that pinnotherid larvae suffer higher mortality rates while searching for the specialized recruitment place (different types of hosts) than free-living species (Lardies and Castilla 2001).…”