The characterization of somatic chromosomes of Gymnothorax unicolor (Delaroche, 1809) by C-banding and NOR staining (Osteichthyes, Anguilliformes)

Abstract

The diploid chromosome number of Gymnothorax unicolor (Delaroche, 1809) is 2n=42, the karyotype comprising six pairs of meta-submetacentric and fifteen pairs of acrocentric chromosomes. C-positive chromatin is present in the centromeres of all chromosomes as well as in the paracentromeric regions of some chromosomes. A nucleolar organizer region was identified on the long arm of chromosome 9, near the centromere. This region is also positive to C-banding.Cytotaxonomical relationships are evidenced between the described karyotype and that of the related species Muraena helena.

First chromosome Characterization in the Neotropical Eel, Gymnothorax ocellatus (Pisces, Muraenidae)

“…1). The NORs showed to be similar to those found in other species analyzed until now in this family, in which only one chromosomes pair was found to be involved with the nucleolar organization (Takai and Ojima 1986, Cau et al 1988, Deiana et al 1990). The differences found were due to the chromosomes involved with the NORs.…”

“…No chromosomal differences related to the sex were observed. The same and very conservative diploid number of chromosomes was also observed in other species of family Muraenidae analyzed so far; thus, Gymnothorax eurostus (Takai and Ojima 1986), Gymnothorax kidako (Nogusa 1960), Gymnothorax reevesi (Shoubai et al 1991), Gymnothorax unicolor (Deiana et al 1990), Muraena helena (Cau et al 1988), Muraena paradalis (Takai and Ojima 1986), and Sideria picta (Ojima 1985, Rishi 1973 all have 2nϭ42 chromosomes. However, differences in the karyotypic formula were observed for those species (Table 1).…”

Karyotype, C‐ and G‐banding, and nucleolar organizer regions ofconger conger(osteichthyes, anguilliformes)

“…NOR was located as follows: a) terminally on the short arm of a small submetacentric chromosome in A. anguilla (Wiberg, 1983), A. rostrata (Sola et al, 1984), M. helena (Cau et al, 1988) and Ophisurus serpens (Thode et al, 1985); b) terminally on the short arm of an acrocentric chromosome in C. conger (present report); c) interstitially, adjacent to the centromere on the long arm of a large acrocentric chromosome in Gymnothorax unicolor (Deiana et al, 1990) and Anago anago (Takai et al, 1987). It is noteworthy that, in the specimens we have studied, C. conger NORs did not show the heteromorphism already evidenced in other Anguilliformes (Sola et al, 1980(Sola et al, , 1984Cau et al, 1988;Deiana et al, 1990). C-positivity coincided with the location of the NORs in all the species studied except Ophisurus serpens.…”

“…Chiarelli et al, 1969Passakas, 1981So\iet al, 1980Park & Grimm, 1981Wiberg, 1983Ohno et al, 1973Solaef al, 1980Park & Grimm, 1981Passakas, 1981Nishikawa et al, 1971Solaef al, 1980Nishikawa et al, 1971Park & Kang, 1979Subrahmanyah & Ramamoorthi, 1971Park & Kang, 1979Ojima & Ueda, 1982Takai & Ojima, 1985Takai & Ojima, 1985Takai et al, 1987Nogusa, I960 Cau et al, 1988Takai & Ojima, 1985Deiana et al, 1990Takai & Ojima, 1985«/., 1991Ojima, 1985Ojima, 1985Nogusa, I960 Ojima, 1985Nishikawa & Sakamoto, 1977Thodeetal, 1985Murofushi etal, 1984 -data not reported NOR chromosomal patterns in Anguilliformes have been studied on only six species from different families, all of which presented a single pair of NOR chromosomes. NOR was located as follows: a) terminally on the short arm of a small submetacentric chromosome in A. anguilla (Wiberg, 1983), A. rostrata (Sola et al, 1984), M. helena (Cau et al, 1988) and Ophisurus serpens (Thode et al, 1985); b) terminally on the short arm of an acrocentric chromosome in C. conger (present report); c) interstitially, adjacent to the centromere on the long arm of a large acrocentric chromosome in Gymnothorax unicolor (Deiana et al, 1990) and Anago anago (Takai et al, 1987). It is noteworthy that, in the specimens we have studied, C. conger NORs did not show the heteromorphism already evidenced in other Anguilliformes (Sola et al, 1980(Sola et al, , 1984…”

“…The karyotype was determined from cultured lymphocytes (Deiana et al, 1990). Specimens were anesthetized in water containing MS222 Sandoz (0.02%), and blood was collected from the dorsal artery using a heparinized syringe.…”