Cytogenetic characterization of the moray eel Gymnothorax tile karyotype (Actinopterygii, Anguilliformes).

Cytogenetic characterization of the moray eel Gymnothorax tile karyotype (Actinopterygii, Anguilliformes) Coluccia E., Salvadori S., Cannas R., Deiana A.M Dipartimento di Biologia Animale ed Ecologia, Università di Cagliari, V.le Poetto, 1 – 09126 Cagliari, Italy – e-mail: coluccia@unica.it Our research group have studied the cytogenetic and molecular characterization of Anguilliformes for many years with the aim to verify the evolutionary relations among species and families. In this work we report the characterization of the Gymnothorax tile karyotype by conventional chromosome bandings and FISH. Gymnothorax tile (Hamilton, 1822) is an Anguilliform fish belonging to family Murenidae, it lives in brakish waters of Pacific and Indian Oceans. The knowledge on this species is very few and refers only its maintenance in captivity: it has a commercial importance as aquarium fish. We analized eleven females by blood cell culture. More than eighthy metaphases plates have been analyzed by Wright’s staining, C- and CMA3- bandings, silver staining and fluorescence in situ hybridization (F.I.S.H.). The relative length and centromeric index of each chromosome pair has been measured by the Cromowin System software (TESI imaging) and Levan et al. (1964) chromosome morphology classification has been applied. A 42 chromosomes karyotype was determined, chromosomes have been arranged in two group of pairs: the first comprises 17 meta-submetacentric of decreasing length and the second 4 acrocentric pairs; heterochromosomes were not identified. Telomeric C-bands were present on all acrocentrics but one, and peculiar intercalary bands characterized some biarmed pairs. One Ag-NOR was localized on the p-arm of pair 12, this was also the only region positive both to 45S rDNA F.I.S.H. and to CMA3 staining. Karyological studies on the Muraenidae family are very sparse and the karyotype is known only in seven species out of 200 (Nelson, 1994) belonging to 15 genera, present in tropical and temperate seas. Most of the species have 2n=42 but with a different karyotype structure; heteromorphic sex chromosomes were reported in Gymnothorax eurostus. Within the family, Muraena helena and G. unicolor genomes are the most studied both at a cytogenetic and molecular level; recently replication banding techniques have pointed out numerous chromosomal homeologies and the chromosome rearrangements that occurred in the evolution of the karyotype between these species. Cytogenetic data on Murenidae species have been reviewed and compared with those here reported for G. tile.