Cytogenetics of Atlantic eels: C- and G-banding, nucleolus organizer regions, and DNA content

Abstract

C- and G-banding, silver staining, and cytofluorometric analysis of DNA content were carried out on two species of eels, Anguilla anguilla and A. rostrata, to compare them, to investigate the existence of sex chromosomes in both species, on which different authors disagree, and to understand the significance of the sex-independent variability found in one chromosome pair.

Mapping 18S ribosomal genes in fish of the genus Brycon (Characidae) by fluorescence in situ hybridization (FISH)

“…Wiberg, 1983;Sola et al, 1984;Viñas et al, 1996). Regional chromosomal duplications, produced either by DNA polymerase slippage or unequal crossing over (Warburton and Henderson, 1979;Jhanwar et al, 1981), could lead to the observed structural polymorphism.…”

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

“…G-banding was very useful because it allowed some homologous chromosomes to be characterized; others pairs, however, showed very similar banding patterns. The fact that among the Anguilliformes studied A. anguilla (Wiberg, 1983), A. rostrata (Sola et al, 1984) and C. conger showed identifiable G-bands, while Muraena Murena helena (Cau et al, 1992) did not, increased the number of taxonomic affinities between Anguillidae and Congridae.…”

“…Clear G-bands were published for A. anguilla (Wiberg, 1983), A. rostrata (Sola et al, 1984) and more recently for some North American cyprinids (Gold et al, 1990;Gold & Li, 1991). 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.…”

“…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…”

“…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.…”