Identification of scleractinian coral recruits from Indo-Pacific reefs

Study of the early life history of scleractinian corals has been hampered by the inability to identify recently settled juveniles. To increase taxonomic resolution of coral recruits, we compared the morphology of the skeleton of juveniles raised from known parents for 29 species in 21 genera and 12 families. Juveniles from only 3 families could be reliably distinguished throughout their 1st year of life: the Acroporidae, which have a porous coenosteum, prominent septa, and no columella; the Pocilloporidae, which have a solid coenosteum, prominent septa and a prominent columella; and the Poritidae, which have septa with prominent teeth. Juveniles in the remaining families examined could not be consistently distinguished. In these taxa, the skeleton began as an epitheca with little internal structure, growth was slow, and the pattern of septal development was similar. Within the 3 distinctive families, a number of other taxa could be recognized when juveniles were young. Genera of the Pocilloporidae could be distinguished by size differences in the diameter of the primary corallite. Isopora, Acropora, and Montipora juveniles could be distinguished by differences in the size of the corallum at settlement. Juveniles of the broadcast spawning Porites appear to be distinguished from those of brooding Porites by the pattern of septal development and by the small size at settlement. The number of taxa that could be distinguished was highest when juveniles were between 4 and 8 wk old. After this time, variation in the growth rates of individuals and thickening of the skeleton obscured differences between the taxa