Karyological analysis of two species of mudskippers (Teleostei: Gobioidei: Oxudersidae) in the Musa estuary, Persian Gulf, Iran

Cytological parameters including whole sets of chromosomes, known as karyology, has become increasingly prevalent in resolving taxonomic issues for uncertain species. This study focuses on the karyological analysis of haploid and diploid chromosomes in two amphibious fish species, Periophthalmus waltoni and Boleophthalmus dussumieri which inhabit muddy beaches of the Persian Gulf. This survey is the first to report on the chromosome number of P. waltoni. To achieve this task, 10 male and 10 female specimens were collected from the beaches of Musa estuary, Persian Gulf, Iran. Mitotic chromosomes and haploid chromosomes were obtained from branchial and testicular tissue samples in males, respectively. The chromosomes were stained using the traditional Giemsa staining technique. The diploid chromosome number for P. waltoni was determined to be 2n=44 in both males and females, with a fundamental number (NF) of 82, whereas the numbers for B. dussumieri were 46 and 82. The karyotype of P. waltoni consisted of 14 large metacentrics, four large sub-metacentric, eight large sub-telocentric, four medium metacentric, six medium sub-metacentric, two medium telocentric, two small sub-telocentric, and four small telocentric chromosomes. In contrast, the karyotype of B. dussumieri comprised 18 large metacentrics, eight large sub-metacentric, two large telocentric, eight medium metacentric, two medium sub-metacentric, two medium telocentric chromosomes, and four microchromosomes. No sex chromosomes were identified in either species. Notably, the results revealed that the chromosome count and morphology differed among the species within the same genus, and the use of the Ag-NOR banding technique accentuated these differences.