Abstract
Eleven sublittoral ,sponges, Geodia barretti, G. macandrewii, Geodia sp., Isops phlegraei, Stryphnus ponderosus, Thenea levis, T. valdiviae, Phakellia robusta, P. rugosa, P. ventilabrum and Tragosia infundibuliformis, all of which are widely distributed in the North Atlantic, were examined for associated fauna. At least 242 epi- and infauna species were found, of which 115 are reported as sponge associates for the first time in the North Atlantic. Sixty species, 19 genera and 1 family are recorded for the first time from the Faroes. Two hundred and twenty-five taxa were found as epifauna on the sponges, three taxa occurred as infauna and 14 taxa both as epi- and infauna.
The morphology of the sponges influences the occurrence and composition of the represented fauna. Thus, the largest number of taxa were present on sponges having a spicule ‘fur’. A number of species showed preference for the oscular cavities of S. ponderosus and the incurrent furrow of T. levis and T. valdiviae. Only one sponge predator, Hanleya nagelfar, was found. The majority of the associated fauna uses the sponges as a substratum. Three categories of direct effect of interactions between the sponges and the associated fauna are proposed. The results of the present investigation show that demosponges constitute a substratum for a large number of benthic taxa on the outer shelf and upper slope in the northeastern Atlantic, and that the scarcity of earlier reports is a result of insufficient investigation. It is suggested that the fauna associated with sponges in temperate to cold waters is facultative, representing the fauna of the local geographical area. This is in contrast to the large number of apparently obligate associates of Porifera in warm tropical waters.
