| This study demonstrates a novel approach to identifying sipunculan larvae, which has previously been difficult. Two species of sipunculan adults and their corresponding larvae were distinguished from each other by DNA fingerprinting using random amplified polymorphic DNA and the polymerase chain reaction (RAPD-PCR). Sipuncula is a phyum which consists of over 200 species of benthic, marine invertebrates. The pelagosphera larvae are planktotrophic and may remain in pelagic waters for a protracted period of time, thus providing a mechanism for the animal's dispersal and genetic exchange. Morphologic similarities between sipunculan larvae and difficulties in rearing the larvae to the adult form in the laboratory have caused the identification of the larval species to remain quite tenuous. RAPD-PCR was used to screen 80 primers of which several produced species specific molecular markers capable of distinguishing between Siphonosoma cumanense, Phascolosoma turnerae, Apionsoma misakiana and Sipunculus nudus. The same banding pattern was demonstrated for adults and larvae spawned from known adults for two species, S. cumanense and P. turnerae. For S. cumanense, tentatively identified individual planktotrophic larvae and juveniles reared from larvae were included. A. misakiana and S. nudus were highly polymorphic intraspecifically and no molecular markers were found in this study capable of producing a specific marker for these two species. This study is the first of its kind for obtaining amplifiable DNA from individual planktotrophic sipunculan larvae and pooled spawned embryos. Now that a correspondence between the adult and larval markers has been established, it should be possible to distinguish other planktotrophic sipunculan larvae and better understand their biogeographic and evolutionary significance. |
