Experimental studies on predation and cannibalism of the settlers of Chasmagnathus granulata and Cyrtograpsus angulatus (Brachyura: Grapsidae)

Abstract

The grapsid crabs Chasmagnathus granulata and Cyrtograpsus angulatus are considered as key species within the benthic communities of estuaries and brackish coastal lagoons in the southwestern Atlantic region. In controlled laboratory experiments, we studied the intensity of interspecific predation as well as intra-and intercohort cannibalism in setllers in relation to refuge Ž . availability, predator characteristics species, size, sex, nutritional state , and the presence or Ž . absence of an alternative food source Artemia nauplii . In both species, the intensity of Ž . intracohort cannibalism among recently settled crabs instars I and II, AsettlersB was low, with ca. 5% mortality during 48 h experimental observation periods. Larger juveniles and adults of both species, by contrast, preyed heavily on the settlers. Predation was significantly reduced when refuges were available for the settlers. Hunger of the predators enhanced in general the predation rate. In the presence of alternative food, the consumption of settlers was significantly reduced. In C. granulata, adult females ate more settlers than the males, probably as a consequence of differences in the morphometric traits of their chelae. Cannibalism and predation by juvenile and adult crabs may play an important role in the regulation of recruitment success for both species and hence, in the structure of estuarine benthic communities. q

Temporal window of receptivity and intraspecific variability in the responsiveness to metamorphosis-stimulating cues in the megalopa of a semi-terrestrial crab,Sesarma curacaoense

“…While the response to adult odours should increase the chance to find the most suitable microhabitat, the selective advantage of this larval behaviour might be offset by increasing cannibalism among different cohorts of juveniles, in particular in physically suitable and thus densely populated habitats (see Luppi et al, 2001). Further ecological field studies considering the settlement of megalopae as well as the patterns of microdistribution of early juvenile crab stages in their natural habitat, including refuge utilization and spatial segregation of different age groups (see Luppi et al, 2002), would greatly enhance our understanding of life-history evolution in this and other responsive crustacean species.…”

“…On the other hand, physically suitable and densely populated habitats with high predation pressure (cf. Luppi et al, 2001Luppi et al, , 2002 should select against this flexible but costly life-history trait. This hypothesis can be tested with combined investigations in the field (studying patterns of larval settlement and juvenile distribution in relation to habitat properties) and in the laboratory (testing the responsiveness of offspring originating from different populations).…”

Causes of decoupling between larval supply and settlement and consequences for understanding recruitment and population connectivity

“…Few studies have explained the link between cannibalism and the stabilizing dynamics in 1 marine populations (Luppi et al, 2001). 2 Cannibalistic interactions in aquatic systems mostly involve fish (Wespestad et al, 2000;Olson 3 et al, 2005) or post-settlement cannibalistic interactions among crabs (Moksnes, 2004), with 4 little information on the regulatory role of cannibalism in benthic broadcast spawners at 5 settlement (Luppi et al, 2001;Tamburri et al, 2007).…”

“…2 Cannibalistic interactions in aquatic systems mostly involve fish (Wespestad et al, 2000;Olson 3 et al, 2005) or post-settlement cannibalistic interactions among crabs (Moksnes, 2004), with 4 little information on the regulatory role of cannibalism in benthic broadcast spawners at 5 settlement (Luppi et al, 2001;Tamburri et al, 2007). Cannibalism often contributes towards 6 mortality at settlement (Luppi et al, 2001;Porri et al, 2008a) and, therefore, alters recruitment 7 and controls population dynamics (Fox, 1975;Polis, 1981). In some species, evolutionary 8 adaptations at settlement can limit mortality caused by cannibalism (Tamburri et al, 2007).…”

Intraspecific interactions in the mangrove crab Ucides cordatus (Decapoda: Ocypodidae) during the metamorphosis and post-metamorphosis periods under laboratory conditions

“…This problem is especially limiting when the crabs reared, under controlled conditions, suffer asynchronous metamorphosis (QUINITIO & PARADO-ESTEPA 2000, ZMORA et al 2005. Technologies to decrease mortality rates, related to this behavior, have already been developed involving food supplementation (DUTIL et al 1997, LUPPI et al 2001) and the use of artificial substrates (CHEN 1990, MARICHAMY & RAJAPACKIAM 2001, HAMASAKI et al 2002, BAYLON & FAILAMAN 1999, AILEEN et al 2000, ZMORA et al 2005.…”