Comparative Cytogenetics最新文献

[This corrects the article DOI: 10.3897/compcytogen.v16.i2.79033.].

Triploid female Helophorusbrevipalpis Bedel, 1881 are recorded from two localities in Provence, France. Their karyotypes are analysed using both chromosome morphology and C-banding. Their karyotypes appear to be identical with those of Spanish material recorded by Angus (1992) but show minor differences from Italian triploid material described by Angus, Jia (2020). Data on C-banding in English H.brevipalpis are given and chromosomal variation in H.brevipalpis is discussed.

We report on the results of a chromosomal study of the big-eyed true bug Geocorisdispar Waga, 1839 (Heteroptera: Geocoridae) aimed at obtaining data on its telomeres. Using fluorescence in situ hybridization (FISH), we have shown, that G.dispar has a non-canonical 10-bp telomeric motif TTAGGGGTGG. This is the first evidence of telomere structure in the family Geocoridae and the first finding of the telomeric sequence (TTAGGGGTGG) _n in the large superfamily Lygaeoidea (infraorder Pentatomomorpha).

The African non-annual killifish genus Epiplatys Gill, 1862 (family Nothobranchiidae) comprises 36 valid species distributed in West, Central and East Africa. The available cytogenetic information for the genus indicates a wide variability in diploid chromosome number (2n) and number of chromosome arms (FN). Here, we report the karyotype of Epiplatysspilargyreius (Duméril, 1861), one of the two species with the lowest diploid chromosome number (2n = 34) in the genus, from the White Nile basin in Ethiopia. Male and female karyotypes contained 18 metacentric/acrocentric and 16 subtelocentric/acrocentric chromosomes. The number of chromosome arms is, respectively, FN = 52. Analysis of karyotype differentiation in the genus allowed us to suggest that the 2n reduction in E.spilargyreius and many other members of the genus Epiplatys is mainly due to Robertsonian translocations (reduction of 2n from 48 to 34 with stable NF = 48-52). We provide an up-to-date summary of cytogenetic data and a brief review of chromosome evolution in the genus.

Supernumerary B chromosomes are significant dispensable genetic elements that follow their own species-specific evolutionary pathways. Despite their widespread occurrence, comprehensive analyses of their meiotic behavior remain limited. In this study, we present the first systematic investigation of B chromosome morphology and meiotic behavior in the hangingfly Bittacuscirratus Tjeder, 1956 using cytogenetic approaches. The male basal chromosome numbers of B.cirratus is 2n = 30 + XO, with 0-5 polymorphic B chromosomes. Intraspecific B chromosome polymorphism manifests as various distinct morphotypes ranging from punctiform, bicentric, and ring-shaped to larger coiled forms, indicating that the B chromosomes may undergo rapid structural changes. During meiosis, B chromosomes display transmission drive through asymmetric segregation, preferentially accumulating in one daughter cell. Most B chromosomes formed univalents, with few forming bivalents or trivalents at meiosis I. Three unconventional retention mechanisms were identified in univalent B chromosomes: (1) associating with a nonhomologous chromosome, (2) accumulating near spindle poles, and (3) contributing to unequal spindle formation. Based on the abundant chromosomal changes of A chromosomes and stable XX/XO sex determination, we infer that the B chromosomes likely originated from multiple A chromosomes in B.cirratus. The roles of B chromosomes in the cell cycle and individual fitness are briefly discussed, and the evolutionary scenario is putatively put forward for the diversification of B chromosomes.

We analyzed chromosomes of four species of East Asian dobsonflies (Megaloptera: Corydalidae): Protohermesgrandis (Thunberg, 1781), P.immaculatus Kuwayama, 1964, P.disjunctus Liu, Hayashi et Yang, 2007 and P.costalis (Walker, 1853). The chromosome number in all species was 2n = 24, consisting of 11 pairs of autosomes plus the XX chromosomes in females and the Xy_p in males. The karyotype of P.immaculatus which occurs in near the central part of the Ryukyu Islands, and is a vicarious species of P.grandis, was similar to the karyotype of P.grandis. On the other hand, the karyotype of P.disjunctus, which is from the Sakishima Islands, and is a vicarious species of P.costalis, resembled that of P.costalis. The X chromosomes are submetacentric, while the Y is the smallest, dot-like chromosome of the set. The sex chromosomes of the first meiotic metaphase (MI) spermatocytes in all species invariably appear as a bivalent-like structure known as parachut bivalents Xy_p, suggesting that the species in this genus share a common sex-bivalent mechanism.

We analyzed chromosomes of four species of fishflies (Megaloptera: Chauliodinae). Three species were from western North America (Dysmicohermesdisjunctus (Walker, 1866), Dysmicohermesingens Chandler, 1954, and Orohermescrepusculus (Chandler, 1954)), and another one from eastern North America (Nigroniaserricornis (Say, 1824)). The chromosome number of the three western species was 2n = 22, with the karyotype consisting of 10 pairs of autosomes plus XY in males. The X chromosomes of these three species are subtelocentric, while the Y chromosomes are small and dot-like. Of the ten pairs of autosomes, the last pair is substantially smaller than the others. The chromosome number in the first meiotic metaphase in spermatocytes of N.serricornis from Michigan was n = 10 (9 autosomal bivalents + Xy_p in the male). The sex chromosomes of N.serricornis formed parachute-type bivalents synchronously with the autosomes. The parachute-type bivalent Xy_p has also been found in four fishflies and four dobsonflies (Megaloptera: Corydalinae) from East Asia, as well as in a fishfly and a dobsonfly from North America. These data suggest that the two subfamilies of Corydalidae share a common sex-bivalent mechanism, along with many beetles (Coleoptera).

Chromosomal polymorphism has been studied in 31 natural populations of Ch.borokensis. For 11 out of 31 populations quantitative analysis of chromosomal polymorphism has been performed. Data from previous publications (10 populations) have also been used to perform an overview of the chromosomal polymorphism of Ch.borokensis and to establish the species range. Most studied populations show a high level of chromosomal polymorphism: on average 66.1 ± 2.6% of specimens were heterozygotes with 1.1 ± 0.6 heterozygotic inversions per larvae. The number of banding sequences found in populations varied from 7 to 18 per population with an average of 12 ± 3. Inversions were found in all chromosomal arms. Besides inversions, B-chromosome was present in 13 populations, and 5 translocations were found. The total number of banding sequences found in banding sequence pool of Ch.borokensis is 40. Twenty six banding sequences are described for the first time for the species.

The barbels of the subfamilies ´Poropuntinae´ and Smiliogastrinae within the family Cyprinidae play a significant role as a food source for fish in artisanal fisheries and are highly valued as ornamental fish in Thailand. In this study, we employed both conventional and molecular cytogenetics to analyze the karyotype of 15 fish species from two cyprinid lineages. All analyzed species had a diploid chromosome number of 2n = 50. Despite sharing the same 2n, our analyses revealed species-specific distribution patterns of the mapped microsatellite motifs [(CA)₁₅, (TA)₁₅, (CAC)₁₀, and (CGG)₁₀]. They were predominantly found at telomeric sites of all-to-few chromosomes. Additionally, some species exhibited a widespread distribution of the mapped microsatellites across the chromosomes while others showed no signal. These variations reflect the evolutionary divergence and chromosomal diversity within the cyprinids. Thus, our findings support the 2n stability in cyprinoid lineages while emphasizing the intrachromosomal evolutionary diversity accompanied by species-specific microsatellite distribution.

Identifying clades with extensive and conspicuous changes in diploid chromosome number (2n) is an important step in unraveling the evolutionary mechanisms underlying karyotype evolution. Here, we report low 2n in a monophyletic group of teleost fishes within the family Osphronemidae defined by their unique spiral egg structure (the "spiral egg" clade). We sampled seven of the nine known species within the spiral egg clade, reporting novel 2n for five species and confirming two others. We find high variability in both 2n and chromosome arm number (fundamental number, FN), suggesting a 2n reduction during the emergence of the clade and numerous large-scale mutations across evolutionary time. These data provide important information in cataloguing 2n shifts in teleost fishes and highlight this group for further study in chromosomal and genomic evolution due to their karyotypic heterogeneity.