Smaller host size and monopolization of space in Patagonian scallops, Psychrochlamys patagonica, covered by the sponge Iophon proximum

LÓPEZ GAPPA, J.; LANDONI, N.A.

JOURNAL OF THE MARINE BIOLOGICAL ASSOCIATION OF THE UNITED KINGDOM

Cambridge University Press

Año: 2007 vol. 87 p. 927 - 931

0025-3154

The aim of this study is to analyse the co-occurrence of the encrusting sponge Iophon proximum and other sessile organisms on the shells of the Patagonian scallop, Psychrochlamys patagonica, and the relationship between scallop size and the presence of this sponge. Scallops were collected from 4 beds distributed along the 100-m depth isobath on the continental shelf off Argentina (SW Atlantic). Statistically significant avoidance was observed between I. proximum and all other groups of sessile invertebrates. Co-occurrence of bryozoans, foraminiferans, folliculinid ciliates, hydrozoans, octocorals and spirorbid, serpulid and sabellarid polychaetes on valves not monopolised by I. proximum produced significant clumping, which, however, almost ceased to occur when only valves without this sponge were analysed. Dead bryozoan colonies and calcareous tubes of serpulid and spirorbid polychaetes were found completely overgrown by sponge tissue, suggesting that the coexistence of I. proximum and other sessile organisms on the surface of P. patagonica is an intermediate stage before I. proximum eventually achieves full coverage of the valve. In Patagonian beds, valves completely covered by I. proximum were significantly smaller than those in which the sponge was absent (valve height, mean±SE, with I. proximum: 54.1±1.74 mm, without I. proximum: 60.4±0.62 mm). This is the first study to report a significantly smaller size in sponge-covered scallops compared to those without sponges.