MEPS 118:179-186 (1995)  -  doi:10.3354/meps118179

Pattern of spatial distribution of a brood-protecting schizasterid echinoid, Abatus cordatus, endemic to the Kerguelen Islands

Poulin, É., Féral, J.-P.

This study examined the spatial distribution at different geographic scales of the echinoid Abatus cordatus which is endemic to the Kerguelen Islands. Special attention was paid to the non-dispersal strategy of the species. It lives burrowed in the sediment and females brood their young in dorsal pouches. The dispersal of this species is therefore characterised by a limited mobility among adults and the lack of a free-swimming larval phase. Using SCUBA and dredging, A. cordatus was sampled all around Kerguelen. The spatial distribution from the island scale to the bay scale shows discontinuities at 2 levels: (1) at the island level favourable sectors (principally characterised by jagged coastline with numerous sheltered bays) are separated by linear coastline or swell exposed sectors; (2) at the bay scale A. cordatus lives in high density, isolated demes in shallow water of sheltered bays. A. cordatus was most numerous in sediments that ranged from medium to fine sand. The granulometry of the sediment and the lack of predation determine this aggregated spatial distribution pattern. Considering that the scale of larval dispersal is the consequence of spatial and temporal habitat structure, the non-dispersal strategy of A. cordatus is associated with a spatially varying but temporally constant habitat as predicted by theoretical models.

Abatus . Brooding . Habitat limits . Kerguelen . Non-dispersal strategy . Schizasteridae . Spatial distribution . Subantarctic

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