Chromosome banding and 18S rDNA in situ hybridization analysis of seven species of the family Achiridae (Teleostei: Pleuronectiformes).

Achiridae is an important family of the order Pleuronectiformes widely distributed in North, Central, and South America with freshwater and marine species. In the present study cytogenetic analyses comprising conventional and molecular techniques were carried out in seven species of this family. The following diploid numbers (2n) and fundamental numbers (FN) were obtained: Achirus declivis 2n=34, FN=52; Achirus lineatus 2n=40, FN=66; Catathyridium jenynsi 2n=40 and FN=50; Gymnachirus nudus 2n=36 and FN=50; Hypoclinemus mentalis 2n=38 and FN=54; Trinectes paulistanus 2n=42 and FN=52; and Trinectes sp. 2n=38 and FN=54. All species presented a single nucleolar organizer region (NOR) bearing chromosome pair and C-band positive segments mainly distributed at the pericentromeric position. The wide variation observed in chromosome number and FN suggests the occurrence of larger chromosome rearrangements in the family Achiridae if compared with other families of the same order.