The family Tetraodontidae comprises 193 valid species of teleost fish distributed in tropical and subtropical regions worldwide. Available cytogenetic information for 31 species indicates extensive variability in diploid chromosome number (2n) ranging from 28 to 46. Here, we present the preliminary cytogenetic characteristics of Tetraodon lineatus Linnaeus, 1758, the type species of Tetraodon Linnaeus, 1758, which is the type genus of the family. The karyotype of a single male of T. lineatus from the White Nile Basin in Ethiopia comprised 12 metacentric/submetacentric and 28 subtelocentric/acrocentric chromosomes (2n = 40, FN = 52). These data are briefly compared with the available cytogenetic information on other tetraodontid genera, summarized according to the current taxonomic classification.
Triploid female Helophorus brevipalpis Bedel, 1881 are recorded from one locality near Oslo, Norway. Analysis of their karyotypes using both conventional Giemsa staining and C-banding reveals a chromosomal arrangement similar to that shown by English diploid material and different from the arrangements shown by known parthenogenetic populations in Spain, France and Italy, indicating that this parthenogenesis has evolved independently.
The small-sized Crocidura horsfieldii (Tomes, 1856) species complex, comprising C. watasei (Kuroda, 1924), C. tadae (Tokuda et Kano, 1936), C. kurodai (Jameson et Jones, 1977), C. wuchihensis (Wang, 1966), and C. indochinensis (Robinson et Kloss, 1922), has long been the subject of taxonomic confusion in the literature. Here, we report for the first time the karyotype of female C. indochinensis from Yongde Snow Mountain, based on conventional Giemsa staining and the GTG-banding technique. C. indochinensis has 2n = 38 and FN = 56. The autosomes consist of four metacentric or submetacentric pairs, four subtelocentric pairs, and ten acrocentric pairs, whereas the X chromosome is a medium-sized submetacentric. Our results demonstrate that the karyotype of C. indochinensis differs markedly in 2n and FN from those of C. horsfieldii, C. watasei, C. tadae and C. kurodai, providing further evidence for the distinct species status of C. indochinensis within this complex. Furthermore, comparative analysis of the G-banded chromosomes of C. indochinensis and C. dsinezumi revealed a high degree of karyotypic homology, with their karyotypes differing primarily by a single fusion/fission event and a centromeric shift or a pericentric inversion, thereby enhancing our understanding of karyotype evolution within the genus Crocidura Wagler, 1832.
Gobies (family Gobiidae) rank among the most diverse of all marine fish families. Although the cytogenetics of these small, ubiquitous fish is still a young field, studies on Atlantic species, despite their limited number, have already revealed a remarkable level of karyotypic variation. This karyotype diversity has provided critical evidence for discovering new species, uncovering population structures, identifying sex chromosomes, and pinpointing major shifts in repetitive DNA. This study presents the first chromosomal characterization of two Atlantic goby species, Coryphopterus glaucofraenum (Gill, 1863) and Evorthodus lyricus (Girard, 1858), using classical cytogenetics and base-specific fluorochrome staining. Our analyses revealed a striking divergence in their karyotypes. Evorthodus lyricus exhibited a karyotype of 2n = 46 (FN = 92), whereas C. glaucofraenum presented 2n = 40 (FN = 42), indicating significant differences in both chromosome and fundamental number (FN). These cytogenetic patterns, combined with existing data for the family, reinforce the high karyotypic diversity within Gobiidae and suggest a relationship between speciation processes and chromosomal modifications in the diversification of this family.
Telomeric sequences in the insect infraorder Nepomorpha (Hemiptera: Heteroptera) have previously been characterized only in the basal superfamily Nepoidea, where the canonical arthropod motif (TTAGG)n was confirmed by fluorescence in situ hybridization (FISH). The telomeric repeat composition of the remaining Nepomorpha superfamilies remained unknown. Using TREW, a tool for de novo identification of candidate telomeric sequences from short-read whole-genome sequencing data, we screened 32 publicly available NCBI datasets representing 24 genera and all 13 Nepomorpha families. The method was validated against species with known (TTAGG)n telomeres in Nepoidea, successfully recovering the expected motif. In Corixoidea, (TTAGG)n was uniformly identified as the best candidate for telomeric sequence across all eight species of three families – Corixidae, Diaprepocoridae and Micronectidae. In contrast, derived 10-bp motifs were recovered from the remaining four superfamilies: (TGGTTAGTGA)n and (TGGTTAGTGT)n in Ochteroidea, (TGGATAGGTG)n and (TGGATAGGAG)n in Naucoroidea (including Aphelocheiridae and Potamocoridae), and (TGGATAGGGT)n uniformly across Notonectoidea and Pleoidea. All derived decamers except those from Ochteroidea share the core octamer TGGATAGG. The retention of (TTAGG)n in the two basal superfamilies and the occurrence of derived decamers in more derived clades are congruent with most current phylogenetic hypotheses for Nepomorpha and support independent evolution of 10-bp motifs within the infraorder. The presence of an identical candidate for telomeric sequence – (TGGATAGGGT)n in Notonectoidea and Pleoidea provides additional support for their close phylogenetic relationship and might be a synapomorphy for this clade. These findings extend the known pattern of telomeric diversification within Heteroptera to Nepomorpha and demonstrate the utility of short-read archival data for taxonomic surveys of telomeric composition.
