The Eleotridae family consists of 35 genera and 150 species distributed in freshwaters/brackish waters, estuaries or shores of tropical and subtropical regions. A few species are found in the Central America and South America. Cytogenetic analyses were performed on sympatric species
Dormitator maculatus (12 individuals; 9 males and 3 females) and
Eleotris pisonis (5 individuals; 2 males and 3 females) collected in the lower course of the Pium River, Northeastern Brazil. Both the species have 2
n=46 with striking differences for the chromosome formulas (
D. maculatus, 40m-sm+6st-a and
E. pisonis, 46a). The two species revealed preferentially centromeric or telomeric heterochromatic regions and absence of structural chromosome heteromorphisms between the sexes. The NORs are located on the short arm of a submetacentric pair (pair 4) in
D. maculatus and in intersticial position on a medium acrocentric (pair 21) in the
E. pisonis. Meiotic analyses carried out on
D. maculatus and
E. pisonis showed a modal value of 23 in both MI and in MII. Comparison with cytogenetic data of Mexican populations (
D. maculatus, 34m-sm+12st-a;
E. pisonis, 2m-sm+42st-a) indicated that the karyotypical changes among the populations from Northeastern Brazil and the Mexican coast are mainly due to pericentric inversion, although translocations, fission and fusion are involved in the karyotypic diversification of the group. The differences observed among the karyotype macrostructure of South and Central American forms suggest the existence of distinct species in these two regions.
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