Size Distribution of Spirobranchus gianteus in Bonaire: Is There a Benefit of Recruitment to Live Coral?
Spirobranchus giganteus is a tube-dwelling polychaete more commonly known as the Christmas tree worm. S. giganteus larvae are planktonic, which is followed by benthic settlement and development into a sessile adult. It has been shown that chemical and physical cues produced by live coral and adult S. giganteus attract larvae to settlement sites. In fact, it has been postulated that there may be a mutualistic relationship between S. giganteus and live coral. However, settlement of S. giganteus on coral rubble has been noted in the field. The aim of this study is to investigate whether there is a relationship between size of S. giganteus and substratum settlement type on the coral reefs of Bonaire. The hypothesis under examination in this study states that S. giganteus settled on live coral will be larger than S. giganteus settled on rubble. The measurement chosen for this study was the diameter of the orifice of the calcareous tube, since it has been shown that this is a good estimate for overall size of the polychaete. The diameter of the orifice of S. giganteus was significantly greater for individuals living on rubble (0.510 cm) than individuals living on live coral (0.457 cm). The species of coral that S. giganteus settled on also appeared to affect the orifice diameter. Individuals on Agaricia agaricites were significantly smaller than individuals settled on both Montastrea annularis and Siderastrea siderea. These results may indicate that the interactions between S. giganteus and live coral, such as extracoelenteric digestion and sweeper tentacles, may be disruptive enough to cause a lower size distribution of polychaetes on that substrate when compared to rubble.
This student research was retrieved from Physis: Journal of Marine Science III (Spring 2008)19: 25-30 from CIEE Bonaire.