Browsing Science by Subjects
Now showing items 1-2 of 2
A chromosomal analysis of Nepa cinerea Linnaeus, 1758 and Ranatra linearis (Linnaeus, 1758) (Heteroptera, Nepidae)An account is given of the karyotypes and male meiosis of the Water Scorpion Nepa cinerea Linnaeus, 1758 and the Water Stick Insect Ranatra linearis (Linnaeus, 1758) (Heteroptera, Nepomorpha, Nepidae). A number of different approaches and techniques were tried: the employment of both male and female gonads and mid-guts as the sources of chromosomes, squash and air-drying methods for chromosome preparations, C-banding and fluorescence in situ hybridization (FISH) for chromosome study. We found that N. cinerea had a karyotype comprising 14 pairs of autosomes and a multiple sex chromosome system, which is X1X2X3X4Y (♂) / X1X1X2X2X3X3X4X4 (♀), whereas R. linearis had a karyotype comprising 19 pairs of autosomes and a multiple sex chromosome system X1X2X3X4Y (♂) / X1X1X2X2X3X3X4X4 (♀). In both N. cinerea and R. linearis, the autosomes formed chiasmate bivalents in spermatogenesis, and the sex chromosome univalents divided during the first meiotic division and segregated during the second one suggesting thus a post-reductional type of behaviour. These results confirm and amplify those of Steopoe (1925, 1927, 1931, 1932) but are inconsistent with those of other researchers. C-banding appeared helpful in pairing up the autosomes for karyotype assembly; however in R. linearis the chromosomes were much more uniform in size and general appearance than in N. cinerea. FISH for 18S ribosomal DNA (major rDNA) revealed hybridization signals on two of the five sex chromosomes in N. cinerea. In R. linearis, rDNA location was less obvious than in N. cinerea; however it is suggested to be similar. We have detected the presence of the canonical “insect” (TTAGG)n telomeric repeat in chromosomes of these species. This is the first application of C-banding and FISH in the family Nepidae.
Further karyosystematic studies of the Boreonectes griseostriatus (De Geer) group of sibling species (Coleoptera, Dytiscidae)–characterisation of B. emmerichi (Falkenström, 1936) and additional European dataA lectotype is designated for the Tibetan species Deronectes emmerichi Falkenström, 1936 (Currently Boreonectes emmerichi (Falkenström)), and its habitus, as well as the median lobe and parameres of its aedeagus, are figured along with additional comparative material. Material of B. emmerichi from Sikkim (BMNH) represents the first record of a Boreonectes Angus, 2010 species from India. The karyotype of B. emmerichi is described as having 26 pairs of autosomes plus sex chromosomes which are X0 (♂), XX (♀). The karyotype is most like that of B. macedonicus (Géuorguiev, 1959), but with slight differences. Additional chromosomal information is given for B. griseostriatus griseostriatus (De Geer, 1774) in the French Alps, B. g. strandi (Brinck, 1943) on the Kola Peninsula, B. multilineatus (Falkenström, 1922) in the Pyrenees and B. ibericus (Dutton & Angus, 2007) in the Spanish Picos de Europa.