Chromosome analysis using different staining techniques and fluorescent in situ hybridization in Cerithium vulgatum (Gastropoda: Cerithiidae)

摘要

Modern cytological methods such as chromosome banding and fluorescent in situ hybridization (FISH) proved to be very useful for understanding the genomic organization of numerous vertebrate species (Sumner 1990; Trask 1991). The same methods have sporadically been used to examine the chromosomes in the phylum Mollusca. In particular, available karyological data on the class Gastropoda indicate that more than 300 species have been analysed cytogenetically (Patterson 1969; Patterson and Burch 1978; Nakamura 1986; Thiriot-Quievreux 1994), while less than 20 of them have been examined using banding techniques.Several families of this class have remained poorly characterized from a karyological point of view. One of this is the family Cerithiidae, where the haploid (n) and/or diploid (2n) chromosome numbers of eight species of four different genera have been determined from analysis of Giemsa stained preparations (Nishikawa 1962; Vitturi and Catalano 1984; Yaseen et al. 1995; Ebied et al. 2000).The Cerithiidae, order Neotaenioglossa, belong to the superfamily Cerithioidea (Ponder and Warén 1988), a group whose origins can be traced back to Jurassic-Cretaceous. According to Houbrick (1988) and Boisseller-Dubayle and Gofas (1999), it includes organisms whose diversity, in terms of morphology, size, habitat, feeding methods, reproductive biology and ecophenotypic plasticity is notable.The present paper was designed with several aims: 1) to describe the karyotype of the “large”Cerithiumvulgatum Bruguière, 1792; 2) to examine the nucleolar organizer regions (NORs) using both conventional (silver, CMA3, and DAPI staining) and molecular (rDNA FISH) techniques; 3) to test for the presence of telomeric (TTAGGG)n and (GATA)n repeats; and 4) to compare results of this study with those reported upon other molluscan species.