Multiple sex chromosome system of X1X1X2X2/X1X2Y type in lutjanid fish, Lutjanus quinquelineatus (Perciformes)

Abstract

The karyotype and other chromosomal markers as revealed by C-banding and Ag-staining were studied in Lutjanus quinquelineatus and L. kasmira (Lutjanidae, Perciformes). While in latter species, the karyotype was invariably composed of 48 acrocentric chromosomes in both sexes, in L. quinquelineatus the female karyotype had exclusively 48 acrocentric chromosomes (2n = 48) but that of the male consisted of one large metacentric and 46 acrocentric chromosomes (2n = 47). The chromosomes in the first meiotic division in males showed 22 bivalents and one trivalent, which was formed by an end-to-end association and a chiasmatic association. Multiple sex chromosome system of X(1)X(1)X(2)X(2)/X(1)X(2)Y type resulting from single Robertsonian fusion between the original Y chromosome and an autosome was hypothesized to produce neo-Y sex chromosome. The multiple sex chromosome system of L. quinquelineatus appears to be at the early stage of the differentiation. The positive C-banded heterochromatin was situated exclusively in centromeric regions of all chromosomes in both species. Similarly, nucleolus organizer region sites were identified in the pericentromeric region of one middle-sized pair of chromosomes in both species. The cellular DNA contents were the same (3.3 pg) between the sexes and among this species and related species.

Cytogenetic studies in three species of Lutjanus (Perciformes: Lutjanidae: Lutjaninae) from the Isla Margarita, Venezuela

“…The cytogenetic features here reported for the examined specimens of L. analis, L. griseus and L. synagris revealed that the three species have the 48-acrocentric karyotype which is shared by most of the Lutjaninae species previously analyzed, such as Lutjanus argentimaculatus (Raghunath & Prasad, 1980), L. kasmira (Choudhury et al, 1979;Ueno & Takai, 2008), L. sanguineus (Rishi, 1973) and L. russelli (Ueno & Ojima, 1992). The only exception is L. quinquelineatus which has been reported to possess 2n=48 A in females and 2n = 47 (1M+46A) in males (Ueno & Takai, 2008).…”

“…Due to the frequency of cytotype II, approximately 9.5%, this rearrangement suggests the existence of a chromosomal polymorphism in the studied population of L. synagris. Nevertheless, the possibility that the observed fusion in L. synagris might originate a neo-Y chromosome and that an incipient stage of multiple sex chromosome differentiation, as the one reported in L. quinquelineatus (Ueno & Takai, 2008), has been identified, can not be discarded.…”

“…The only exception is L. quinquelineatus which has been reported to possess 2n=48 A in females and 2n = 47 (1M+46A) in males (Ueno & Takai, 2008).…”

“…In fact, when chromosome differences are restricted to one sex, the presence of sex chromosomes is strongly suggested (Devlin & Nagahama, 2002). As a matter of fact, the presence of 2n=48 acrocentric chromosomes in females and 2n=47 (1 M+46A) in males of L. quinquelineatus was interpreted by Ueno & Takai (2008) as the result of a single Robertsonian fusion which formed a neo-Y chromosome, establishing a multiple sex chromosome system of X 1 X 1 X 2 X 2 /X 1 X 2 Y type. In the case reported here for L. synagris, the reduced 2n=47 cytotype II characterizes only two (one male, one immature) of the 21 specimens analyzed, but, among these latter, the remaining eight males present the same 48 acrocentric chromosome cytotype I shown by all ten females and one immature specimens.…”

“…In fact, among the 105 recognized species of Lutjanidae, barely five species have been karyotyped to date: Lutjanus argentimaculatus (Raghunath & Prasad, 1980), L. kasmira (Choudhury et al, 1979;Ueno & Takai, 2008), L. sanguineus (Rishi, 1973), L. russelli (Ueno & Ojima 1992), and L. quinquelineatus (Ueno & Takai, 2008). For most of them, only the chromosome number and morphology have been reported and there is no data regarding the chromosomal distribution and composition of the constitutive heterochromatin or numbers and locations of the major and minor ribosomal genes, which have proved to be useful markers in the investigation of the phylogenetic relationships among fish species within a family (Sola et al, 2007).…”