On coral reefs off the Florida Keys (USA), the obligate sponge-dwelling brittlestar Ophiothrix lineata lives almost exclusively in the tube sponge Callyspongia vaginalis. We examined chemotactic recognition by O. lineata to assess sponge host preferences using a Y-tube assay chamber. O. lineata preferentially selected seawater conditioned by C. vaginalis relative to seawater controls and showed no preference for seawater conditioned by the infrequent host sponge Niphates digitalis or the non-host sponge Aplysina archeri. When offered seawater conditioned by C. vaginalis and N. digitalis, O. lineata preferentially chose C. vaginalis. Field manipulations examined growth of O. lineata confined to live in all 3 sponge species and the impact of habitat size on growth of O. lineata living in C. vaginalis. Growth of O. lineata was significantly greater in longer (12 cm) tubes of C. vaginalis than in shorter (6 cm) tubes, and while O. lineata was able to survive in A. archeri, growth was greater for brittlestars living in C. vaginalis and N. digitalis. Surveys of O. lineata in C. vaginalis revealed that 74.3% of sponges had at least 1 male and female brittlestar, with 37.1% of sponges having a greater proportion of males, which may increase brittlestar fertilization success. Abundance of O. lineata increased with sponge size and did not differ based on the presence of brooded larvae in sponge tissue. The obligate association of O. lineata with C. vaginalis likely evolved as a consequence of some combination of host abundance, enhanced food availability, and greater probability of mating success in the multi-tubed sponge.
KEY WORDS: Host specificity · Chemotaxis · Ophiothrix lineata · Callyspongia vaginalis
Resale or republication not permitted without written consent of the publisherAquat Biol 12: [37][38][39][40][41][42][43][44][45][46] 2011 pheus is most likely a function of space partitioning based on sponge morphology, competitive interactions between shrimp species, the eusocial behavior of several species, and the direct development and short dispersal distances of larvae (Duffy 1992, 1996b, Macdonald et al. 2006.The pattern of host use observed in alpheid shrimp is probably one of many, considering the abundance and diversity of sponges and their associated fauna (reviewed by Wulff 2006). The sponge-dwelling brittlestar Ophiothrix lineata is a species-specific obligate living in association with the tube sponge Callyspongia vaginalis (Henkel & Pawlik 2005). Although O. lineata has been observed living in association with other sponges at low frequency (Kissling & Taylor 1977, Hendler et al. 1995, Henkel & Pawlik 2005, surveys of sponges in the Florida Keys, USA, recorded O. lineata living in C. vaginalis 99% of the time, despite the presence of similarly shaped tube sponges that could provide refuge (Henkel & Pawlik 2005). The association between O. lineata and C. vaginalis has been described as a cleaning mutualism, with O. lineata deposit-feeding on the surface of the sponge (Hendler 1984). Compari...