Population structure of the South American estuarine crab, Chasmagnathus granulatus (Brachyura: Varunidae) near the southern limit of its geographical distribution: comparison with northern populations

BAS CLAUDIA; LUPPI TOMÁS; SPIVAK EDUARDO

HYDROBIOLOGIA

Kluwer Academic Publishers

Año: 2005 vol. 537 p. 217 - 228

0018-8158

Abstract 12 Crabs are among the most conspicuous and ecologically important invertebrates of the large intertidalCrabs are among the most conspicuous and ecologically important invertebrates of the large intertidal 13 zones that characterize estuarine and protected coastal areas in temperate regions. The habitat, populationzones that characterize estuarine and protected coastal areas in temperate regions. The habitat, population 14 structure and breeding cycle of Chasmagnathus granulatus (Brachyura: Varunidae), a semiterrestrial bur-structure and breeding cycle of Chasmagnathus granulatus (Brachyura: Varunidae), a semiterrestrial bur- 15 rowing crab endemic to the warm temperate coasts of the Southwestern Atlantic, were studied in Sanrowing crab endemic to the warm temperate coasts of the Southwestern Atlantic, were studied in San 16 Antonio Bay (Argentina), near the southern limit of its range. San Antonio Bay has no freshwater input,Antonio Bay (Argentina), near the southern limit of its range. San Antonio Bay has no freshwater input, 17 winter is relatively colder, and summer warmer, than northern habitats of this species. Crabs lived both inwinter is relatively colder, and summer warmer, than northern habitats of this species. Crabs lived both in 18 vegetated and unvegetated zones, but density and sex ratio varied among dates and zones. The maximumvegetated and unvegetated zones, but density and sex ratio varied among dates and zones. The maximum 19 observed density was 136 crabs/m2, the maximum carapace width (CW) was 32 mm (males) and 29.8 mmobserved density was 136 crabs/m2, the maximum carapace width (CW) was 32 mm (males) and 29.8 mm 20 (females), ovigerous females were found only in November and January, and the smallest ovigerous female(females), ovigerous females were found only in November and January, and the smallest ovigerous female 21 measured 17 mm CW. The population structure, spatial distribution, and recruitment pattern of C. gran-measured 17 mm CW. The population structure, spatial distribution, and recruitment pattern of C. gran- 22 ulatus did not differ between San Antonio Bay and northern habitats. The higher density, smaller maximumulatus did not differ between San Antonio Bay and northern habitats. The higher density, smaller maximum 23 size and shorter reproductive cycle observed in San Antonio cannot be atributed to changes associated withsize and shorter reproductive cycle observed in San Antonio cannot be atributed to changes associated with 24 a latitudinal cline and other factors, such as thermal amplitude and food availability, need to be studied.a latitudinal cline and other factors, such as thermal amplitude and food availability, need to be studied.