FIELD SURVEY OF THE OCCURRENCE AND SIGNIFICANCE OF REGENERATION IN AMPHIURA-CHIAJEI (ECHINODERMATA, OPHIUROIDEA) FROM KILLARY HARBOR, WEST-COAST OF IRELAND

The boreo-Mediterranean amphiurid Amphiura chiajei Forbes occurs in hi gh numbers (approximately 700 individuals/m2) in Killary Harbour, a fj ordic inlet on the west coast of Ireland. 99.1% of the adult individua ls show signs of arm regeneration, while 0.5% show regeneration of the disc. A study of the phenomenon commenced in November 1987 and contin ued on a seasonal basis until July 1989. Specimens were collected by S CUBA. The overall mean length of regenerated arm tissue over the 21 mo sampling period was 33.5 +/- 6.5 mm. Regeneration points were most co mmon in the proximal and in the distal one-third of each arm. An overa ll mean of 4.21 +/- 0.3 arms per individual showed evidence of regener ation, while biomass assays revealed that regenerated tissue accounted for up to 57.9% of the total body weight. Anthropogenic activity (e.g . bottom trawling) may contribute to regeneration, although sub-lethal predation appears to be the main causitive factor of regeneration. Gu t analyses of potential predators at the sampling station revealed tha t fish species (especially the Pleuronectidae) are particularly implic ated. This predation seems to vary seasonally, being greatest in the s ummer months. Since the larger individuals showed the greatest evidenc e of arm regeneration, it is assumed that such sub-lethal damage is a persistent experience. Whatever the causality, the population of A. ch iajei in Killary Harbour is deemed to be highly resilient.