Population dynamics and reproductive output of the non-indigenous crab Charybdis hellerii in the south-eastern Caribbean Sea

Abstract

Charybdis hellerii is one of several poorly known non-indigenous crabs in the Caribbean. In this study we report on the reproductive dynamic of a shallow subtidal population that invaded Isla Margarita, Venezuela, south-eastern Caribbean Sea . 15 years ago and has persisted in the region up to date. Male and female crabs, both large and small, were found year-round at the study site. The size-frequency distribution indicated a lifespan of 2-3 years. Charybdis hellerii reproduces continuously but with very low intensity during the year. Small individuals (,25 mm carapace length) were uncommon and intermittently found during the study period. Sex-ratio varied between 0.1 and 0.65 (mean + SD ¼ of 0.46 + 0.14) and did not differ significantly from 1:1 ratio during most of the year. The size of the smallest brooding female was 36.81 mm carapace width (CW). Behavioural size at first maturity (movable abdomen) in males and females was estimated to be 22.39 mm CW (confidence limits: 18.35-24.72) and 37.43 mm CW (35.55-39.09), respectively. Reproductive output, estimated as the ratio of embryo to female body dry mass, varied between 0.052 and 0.084 (0.07 + 0.008). Also, reproductive output was sizedependent with large females allocating proportionally less resources to egg production than small females. The reproductive schedule here reported for C. hellerii disagrees with the generalized idea of exotic populations 'thriving' in an environment free of natural enemies (e.g. predators, competitors and diseases).

A test of large-scale reproductive migration in females of the amphidromous shrimp Macrobrachium acanthurus (Caridea : Palaemonidae) from south-eastern Brazil

“…For gonochoric (separate sexes) species such as M. acanthurus, sex allocation theory predicts equal sex ratios as parents should produce an equal number of male and female offspring because of frequency-dependent selection against the more common sex in the population (Fisher 1930). However, female or male skewed population-wise sex ratios have been reported before in other shrimps (Alon and Stancyk 1982;Bauer and Abdalla 2001;Fransozo et al 2004; Mejía-Ortíz and Alvarez 2010) and major causes for imbalances in sex ratio among marine invertebrates include sex-specific growth and/ or mortality rates (Wenner 1972), sex-dependant migration (Wenner 1972;Costa et al 2010), sex-dependant mating behaviours (Willson and Pianka 1963;Castilho et al 2008), and/or sampling error (Bolaños et al 2012). Sex-dependant migration does not appear to occur in the studied river.…”

Fecundity and fertility in a freshwater population of the neotropical amphidromous shrimpMacrobrachium acanthurusfrom the southeastern Atlantic

“…In other groups of decapod crustaceans, i.e. brachyuran crabs, brood weight, and/or fecundity exhibits an isometric or nearly isometric constraint to about 10% of body weight and limitations on space available for yolk accumulation in the body cavity appear to be the main factor constraining brood size (Hines 1982; for an exception, see Bolaños et al 2012). We argue in favor of future studies examining whether fecundity increases proportionally or disproportionally with a unit increase in body size in caridean shrimps to improve our understanding of those intrinsic (i.e.…”

Size of catch, reproduction and feeding of the small-eye smooth-hound, <em>Mustelus higmani</em> (Carcharhiniformes: Triakidae), in Margarita Island, Venezuela

“…This portunid crab was observed in Venezuela in 1993 (Bolaños et al 1997), and its distribution in the Atlantic includes Florida, the Caribbean Sea and Brazil (Campos and Türkey 1989, Lemaitre 1995, Mantelatto and Dias 1999. Along its distribution range in the Atlantic, C. hellerii is considered well established, forming dense populations on sandy habitats of both marine and estuarine coast (Bolaños et al 2012, Sant'Anna et al 2012. The occurrence of C. hellerii in the diet of M. higmani denotes that this species could play an important role as a natural predator of this invasive species.…”