DISTRIBUTION OF HOLOTHURIAN LARVAE DETERMINED WITH SPECIES-SPECIFIC GENETIC PROBES

Identification of marine invertebrate larvae to the species level is o ften difficult due to morphological similarity and phenotypic plastici ty. To study dispersal of morphologically indistinguishable holothuria n larvae, we developed a simple detection protocol that uses a series of oligonucleotide probes for the 16S rRNA portion of the mitochondria l DNA genome; this protocol may be feasible for use onboard research v essels. Using our technique, we analyzed > 1,800 larvae from collectio ns made during spring 1993 in the western Gulf of Maine. Of the three species present in the plankton, Cucumaria frondosa larvae dominated t he samples, often comprising >90% of the larval pool and 95% of new re cruits. Temporal differences in planktonic distribution suggest the so uthward transport of C. frondosa. The vertical distribution of larvae over time suggests that larvae are located primarily in the upper coas tal waters. The presence of C. frondosa larvae in the coastal waters o f New Hampshire represents a loss to recruitment because C. frondosa a dults are extremely rare in this area.