A Combined Approach of DNA Probe and RFLP for Family and Species Identification of Larval Stages of Commercially Important Aquatic Species: A Study on the Surfclam Spisula solidissima

This paper deals briefly with a technique developed for the identification of the early stages of veligers of the surfclam Spisula solidissima from the larval stages of other common bivalve species using a combination of DNA probe and restriction fragment length polymorphism (RFLP) analysis. An oli¬ gonucleotide sequence designed from the 18S ribosomal RNA gene (nucleotide position 259-276) provided a sensitive probe for the Family Mactridae, to which S. solidissima belongs. DNA of unknown larvae picked from the plankton samples was extracted using Chelex-100. The 600bp fragment of the 18S rRNA gene was amplified by polymerase chain reaction (PCR). PCR products and controls were tested with the mactrid-specific probe by dot-blot hybridization. The probe hybridized only with controls and larvae of S. solidissima and Mulinia lateralis (The only other member of Family Mactridae present in the study site). Higher percentage of larval amplifications were detected by dot-blot hybridization than by agarose gel electrophore¬ sis indicating that colorimetric detection with a probe is more sensitive than ethidium bromide in the visualization of DNA. Restriction enzymes BtsUI and Aval having different restriction sites were used in RFLP analysis to separate the larvae of S. solidissima from those of M. lateralis. It is suggested that a similar approach in fishery biology may be very effective and quick in identification of eggs and larval stages of commercially important species of shell and finfishes in studies pertaining to population dynamics, reproductive behaviour, larval recruitment, resource evaluation and management. Problem