Epibiosis on embryos and brooding care in the burrowing crab Chasmagnathus granulatus (Brachyura:Varunidae): comparison between mudflats and saltmarshes.

SILVA PAOLA; LUPPI TOMAS; SPIVAK EDUARDO

JOURNAL OF THE MARINE BIOLOGICAL ASSOCIATION OF THE UNITED KINGDOM

Año: 2007 p. 893 - 901

0025-3154

Chasmagnathus granulatus is a semiterrestrial intertidal burrowing crab that inhabits both the unvegetated mudflats and the cordgrass (Spartina densiflora) salt marshes in Mar Chiquita Lagoon (Argentina), where it is considered the ecologically key species. The mass of C. granulatus eggs incubated by females is colonized by epibiotic micro-organisms and accumulates detritus. The type of epibionts that use eggs as a substrate, the infestation degree, the maternal care behaviour and the protection of the incubation chamber were compared between females living on mudflats and on Spartina-dominated areas. In both places, the epibiosis by bacteria and filamentous fungi and peritrichid colonial ciliate was significantly higher in the periphery than in the centre of the brood mass. The accumulation of detritus was higher in the periphery in mudflat females but not in salt marsh females. Moreover, the level of detritus was significantly higher in mudflat than in salt marsh females only in the periphery of the brood. The infestation level of bacteria and fungi, and peritrichids, increased throughout the embryonic development only in mudflat females. The periphery of the brood mass was significantly more contaminated in mudflat than in marsh females, while the central region of the brood mass did not differ between habitats. The pleopods were significantly more contaminated by bacteria and filamentous fungi and peritrichid colonial ciliates in premoult females than in postmoult females, independently from the collection site. The percentage of females with abnormal embryos was significantly higher in mudflats (26.7%) than in marshes (12.3%). Females with late embryos spent more time flapping the abdomen and probing the embryos with the chela. Non-ovigerous females did not perform specific maternal care activities. The volume of brood mass both in early or late stage of development is greater than that of the incubation chamber and, consequently, peripheral embryos are more exposed.