BIOLOGICAL AND OCEANOGRAPHIC INSIGHTS FROM LARVAL LABRID (PISCES, LABRIDAE) IDENTIFICATION USING MTDNA SEQUENCES

Polymerase chain reaction and direct comparison of mitochondrial DNA s equences from a cytochrome b gene fragment were used to identify two m orphologically distinct larval types of Xyrichtys, a genus of tropical wrasse (Pisces: Labridae). Both larval types were collected during ic hthyoplankton surveys on the Middle Atlantic Bight shelf in the summer of 1988. DNA sequence comparisons indicated that both types were larv ae of Xyrichtys novacula (Linnaeus). Back-calculated birthdate distrib utions for those larvae collected on the Middle Atlantic Bight shelf d emonstrated that the two larval types formed two distinct cohorts indi cating a biological difference. The two distinct larval types may be a consequence of an ecophenotypic effect, or they may represent offspri ng from genetically distinct populations. These results emphasize that important biological and oceanographic information can be gained thro ugh the use of the polymerase chain reaction and DNA sequencing for la rval identification.