Haplosyllis spongicola Grube Polychaeta, Syllidae Associated with Two Species of Sponges from East Africa Tanzania, Indian Ocean

Abstract. The presence of Haplosyllis spongicola G rube 1855 Polychaeta, Syllidae in two sponge species from the Indian Ocean Tanzania, Theonella swinhoei G ray 1868 and Liosina paradoxa THIELE 1899, was detected. Polychaetes lived exclusively inside the aquiferous system of the sponges, reaching a mean density of 68 individuals · cm^-3 in T. swinhoei and 148 individuals · cm^-3 in L. paradoxa Acetone extractions were prepared from sponge tissues of T. swinhoei and L. paradoxa and from the gut contents of their respective inhabiting polychaetes. Absorption spectra matched for each sponge/polychaete pair. These data confirm that polychaetes exploit the soft parts of the sponges in which they live. In addition, in L. paradoxa direct confirmation of a predatory activity of worms on sponge internal tissues was obtained on the basis of the finding of terrigenous sediments, which typically reinforced the sponge canal walls, in the gut lumen of the inhabiting polychaete. No evident ultrastructural changes of the host tissue due to endobionts have been observed. These results confirm the parasitic/micropredatory habits of H. spongicola. Data on different morphological characteristics of H. spongicola living in the two sponge species are presented and discussed.