Verification of cyprid size as a tool in the identification of two European species of Chthamalus barnacles using mtDNA-RFLP analysis

Abstract

Adult barnacles of Chthamalus stellatus and Chthamalus montagui were collected in August 1998, from Garrettstown Co. Cork and Kilkee Co. Clare, in southwest and west Ireland, respectively. Attached cypris larvae were collected during the settlement season of C. stellatus and C. montagui, on 2 shores in Co. Cork and 1 shore on Clare Island, Co. Mayo in west Ireland. Cyprid collections were made during either August or September, in 1992, 1994 and 1998 and all cyprids were measured along their carapace length. Size-frequency histograms were produced for each sampling occasion. Total DNA was extracted and the COI-COII mitochondrial genes were PCR amplified, both from selected adults and cyprids of each species collected in 1998. Composite haplotypes, produced by digesting PCR products with the restriction endonucleases TaqI and RsaI, showed clear identification between the 2 species as adults and larvae. Of the 68 cyprids examined, those measuring 525 μm and under were found to have RFLP profiles corresponding with C. montagui adults, while those of 550 μm and larger were found to match C. stellatus adults. The findings verify previous length-frequency analysis. Carapace length is an important character in the identification of C. stellatus and C. montagui cyprids. The PCR primers developed during this study will also amplify DNA from 4 other species of acorn barnacle.