Sponge-seaweed associations in species of Ptilophora (Gelidiaceae, Rhodophyta)

Abstract

Sponge–seaweed associations in the seaweed genus Ptilophora are poorly understood; therefore, 94 specimens, representing all 17 species of Ptilophora, were examined to detail this phenomenon. All but 2 Ptilophora species were shown to produce surface proliferations, with 13 species found to have sponge associations. Evidence for facultative sponge epiphytism was found with species–specific interactions being unlikely. Results show that surface proliferations are not induced by sponge epiphytes, as they often occur in the absence of sponge epiphytes, and vice versa. The significant number of proliferate thalli found with sponge epiphytes suggests that there is a likely relationship between the presence of surface proliferations and sponge infestation. Sponge epiphytes and Ptilophora species appeared structurally related in that the sponge probably exploits a niche habitat provided by the alga, for which surface proliferations might aid the sponge in bonding to the alga