Abundance, Density, And Size Structureof Spirobranchus Gaymardi (polychaeta,rnserpulidae) In Philippine Coral Reefs

摘要

Spirobranchus gaymardi (Quatrefages, 1865) is a tubicolous polychaete known to be associated with corals. Its abundance, density, and size structure on Philippine coral reefs were studied at several sites separated by a few kilometers (within province) to more than 300 km (northern vs southern province of mainland Luzon). Tubeworms were seen only in about 10 species of corals, and were generally more numerous at shallower depths. While S. gaymardi appeared to colonize a suite of corals, there seemed to be fewer coral species where they grow larger. Massive Po-rites appeared to be the most favorable host, having the most number of worms of different sizes. Large worms were mainly found in the northern sites on massive Porites corals. The largest worms, however, were found on dead corals of massive Porites. Smaller worms were uncommon in such dead colonies suggesting that after the association with massive Porites breaks down (i.e., the host dies), survival of the worms is better if they are larger. Abundance and density of S. gaymardi were only significantly different among sites, especially more distant ones (northern > southern province). Host coral size and organic matter content of the sediments each accounted for about 28% of the variation in worm abundance. Spirobranchus gaymardi was gregarious and size class analysis of these aggregations on massive Porites showed similar occurrences of single and mixed year classes. Solitary worms were also common. These results may reflect the variable behavior of S. gaymardi larvae at settlement which may be an adaptive strategy.