Postsettlement growth of two estuarine crab species, Chasmagnathus granulata and Cyrtograpsus angulatus (Crustacea, Decapoda, Grapsidae): laboratory and field investigations

Abstract

The estuarine grapsid crabs Chasmagnathus granulata and Cyrtograpsus angulatus belong to the most typical and dominant inhabitants of brackish coastal lagoons in southeastern South America. In a combined laboratory and field investigation of juvenile growth, we measured the increase in body size in these species under controlled conditions as well as in field experiments (in Mar Chiquita lagoon, Argentina), seasonal changes in size frequency distribution of a natural population, and growth related changes in selected morphometric traits of male and female juveniles (relations between carapace width, carapace length, propodus height and length of the cheliped, and pleon width). At 24°C, Cy. angulatus grew faster than Ch. granulata; it reached the crab-9 instar (C9; 13 mm carapace width) after 92 days, while Ch. granulata required 107 days to reach the C8 instar (7.4 mm). At 12°C, growth ceased in both species. The pleon begins to show sexual differences in the C5 (Cy. angulatus) and C8 instar (Ch. granulata), respectively, while the chelae differentiate earlier in Ch. granulata than in Cy. angulatus (in C4 vs C6). In the field, growth was maximal in summer, and was generally faster than in laboratory cultures. However, there is great individual variability in size (about 25% even in the first crab instar) and in size increments at ecdysis, increasing throughout juvenile growth. Our data indicate that, in the field, small-scale and shortterm variations in feeding conditions, temperature, and salinity account for an extremely high degree of variability in the absolute and relative rates of growth as well as in the time to sexual differentiation.

A life history model for the San Francisco Estuary population of the Chinese mitten crab, Eriocheir sinensis (Decapoda: Grapsoidea)

“…The distribution of sizes of early staged crabs from natural habitats supports the occurrence of a molt increment around 22% in South Bay tributaries (C. Culver, unpublished data), and is similar to increments reported for small crabs in Germany (24%) (Panning 1939a). This molt increment is similar to growth rates reported for other young juvenile grapsoid crabs (Spivak 1988;Luppi et al 2002) and other decapods (Hartnoll 1982).…”

Seasonal and interpopulational variability in fecundity, egg size, and elemental composition (CHN) of eggs and larvae in a grapsoid crab, Chasmagnathus granulatus

“…Dense populations of this species are found in estuarine mudXats and salt marshes, as well as in coastal bays and lagoons with highly variable salinities, temperatures, and tidal patterns (Spivak 1997). Studies of diVerent populations of this species have shown diVerences, particularly between marine and estuarine habitats, in maximum adult body size, egg size, and in the timing and duration of the reproductive season (see Botto and Irigoyen 1979;D'Incao et al 1992;Anger et al 1994;RuVino et al 1994;Spivak et al 1994Spivak et al , 1996Iribarne et al 1997;Luppi et al 1997Luppi et al , 2002López-Greco and Rodríguez 1999;Ituarte et al 2004;Bas et al 2005).…”

Effect of different protein supply on growth of three populations of a crab adapted to low energy diets

“…In this regard, Luppi et al [18] compared growth of juvenile N. granulata and Cyrtograpsus angulatus, another grapsoid aquatic euryhaline crab from MC, from megalopae to stage 8 juveniles. Individuals were fed with high protein live diet (Artemia sp.…”

“…The same is true for size increment per molt, since no differences appeared between diets D and E and similar values were obtained in individuals fed with live Artemia spp. nauplii [18] or Artemia spp. nauplii and frozen Idotea baltica [19].…”