Snejana Grozeva

Instituta of biodiversity and ecosystem research, BAS Bulgaria
{{numberWithCommas(28)}} Publications

New data on karyotype, spermatogenesis and ovarian trophocyte ploidy in three aquatic bug species of the families Naucoridae, Notonectidae, and Belostomatidae (Nepomorpha, Heteroptera)

We report the karyotype, some aspects of spermatogenesis, and ovarian trophocytes ploidy in three aquatic bug species: Ilyocoris cimicoides (Linnaeus, 1758), Notonecta glauca Linnaeus, 1758, and Diplonychus rusticus Fabricius, 1871 from previously unexplored regions – South Europe (Bulgaria) and Southeast Asia (Vietnam). Our results add considerable support for the published karyotype data for these species. In I. cimicoides, we observed achiasmate male meiosis – the first report of achiasmy for the family Naucoridae. More comprehensive cytogenetic studies in other species of the Naucoridae are required to elucidate the role of achiasmy as a character in the systematics of the family. Our observations on the association between phases of spermatogenesis and developmental stages in I. cimicoides and N. glauca differ from the previously published data. In these species, we assume that the spermatogenesis phases are not strongly associated with certain developmental stages. For further cytogenetic studies (on the Balkan Peninsula), we recommend July as the most appropriate month for collection of I. cimicoides and N. glauca. In the ovaries of both species, we studied the level of ploidy in metaphase and interphase trophocytes. In I. cimicoides, diploid and tetraploid metaphase trophocytes were found. Heteropycnotic elements, observed in interphase trophocytes of this species, represented the X chromosomes. It allowed us to determine the trophocytes ploidy at interphase (2n was repeated up to 16 times). The situation with N. glauca was different. The metaphase trophocytes were diploid and we were not able to determine the ploidy of interphase trophocytes since such conspicuous heteropycnotic elements were not found. The scarce data available suggest a tendency for a low level of trophocyte ploidy in the basal infraorders (Nepomorpha and Gerromorpha) and for a high level in the more advanced Pentatomomorpha. Data about this character in species from other infraorders are needed to confirm that tendency.

New evidence for the presence of the telomere motif (TTAGG) n in the family Reduviidae and its absence in the families Nabidae and Miridae (Hemiptera, Cimicomorpha)

Male karyotype and meiosis in four true bug species belonging to the families Reduviidae, Nabidae, and Miridae (Cimicomorpha) were studied for the first time using Giemsa staining and FISH with 18S ribosomal DNA and telomeric (TTAGG)n probes. We found that Rhynocoris punctiventris (Herrich-Schäffer, 1846) and R. iracundus (Poda, 1761) (Reduviidae: Harpactorinae) had 2n = 28 (24 + X1X2X3Y), whereas Nabis sareptanus Dohrn, 1862 (Nabidae) and Horistus orientalis (Gmelin, 1790) (Miridae) had 2n = 34 (32 + XY) and 2n = 32 (30 + XY), respectively. FISH for 18S rDNA revealed hybridization signals on a sex chromosome, the X or the Y, in H. orientalis, on both X and Y chromosomes in N. sareptanus, and on two of the four sex chromosomes, Y and one of the Xs, in both species of Rhynocoris Hahn, 1834. The results of FISH with telomeric probes support with confidence the absence of the “insect” telomere motif (TTAGG)n in the families Nabidae and Miridae and its presence in both species of genus Rhynocoris of the Reduviidae, considered as a basal family of Cimicomorpha. Increasing evidence reinforces the hypothesis of the loss of the canonical “insect” telomere motif (TTAGG)n by at least four cimicomorphan families, Nabidae, Miridae, Tingidae, and Cimicidae, for which data are currently available.

ARPHA Conference Abstracts

First data on the phenology and spermatogenesis of Ilyocoris cimicoides (Heteroptera, Nepomorpha, Naucoridae) from the Balkan Peninsula

Ilyocoris cimicoides (Linnaeus, 1758) is an aquatic bug, common predator in lakes and ponds (Denton and Rordam 1998). It is very broadly distributed: found in most of Europe and in Asia from Anatolia to Siberia and Northern China (Fent et al. 2011). The phenology of the species has been studied in Northern and Central Europe (references in Papacek and Gelbic 1989, Waitzbauer 1974), the Lower Volga region and Western Siberia (references in Kanyukova 2006). A chromosome formula of 2n = 48A + 2m + X and post-reduction of the sex chromosomes have been reported for I. cimicoides (as Naucoris cimicoides), based on specimens (no information about the developmental stage) collected north of the Danube River (Steopoe 1929). Von Divaz (1915) published a study on the spermatogenesis of I. cimicoides (as Naucoris cimicoides) from Serbia, but he did not in fact deal with the spermatogenesis, focusing instead on the presence and behaviour of specific chromatophilic bodies (“corpuscules archoplasmiques”). The only information on spermatogenesis during the preimaginal development of I. cimicoides has been reported by Papacek and Gelbic (1989) for South Bohemia. They studied the development of the internal male reproductive system with a brief comment on spermatogenesis observed in different nymphal stages. There are neither phenology nor chromosome data about I. cimicoides from the Balkan Peninsula published. Such information for this region could contribute to a better understanding of the adaptations of this broadly distributed aquatic insect to the climate conditions in South-East Europe, or to potential climate changes. We analysed I. cimicoides specimens collected between March and November 2008–2019 from more than 50 different localities in Bulgaria and determined the months of the year when each of the developmental stages was available. In addition, we studied the spermatogenesis in different nymphal stages and imago, collected between September 2018 and August 2019. The analysis of the phenology data showed that in Bulgaria, similarly to the observations from other parts of its range, I. cimicoides has one generation per year (i.e. it is univoltine). In the studied region, the postembryonic development begins earlier (in April) than in Central Europe (in May) and western Siberia (in June) (references in Papacek and Gelbic 1989, and in Kanyukova 2006). We confirm the chromosome formula and the behaviour of the sex chromosomes reported by Steopoe (1929). In stage V nymphs, collected in September, spematogenesis was already completed – we observed only spermatids/spermatozoa, as it has been reported by Papacek and Gelbic (1989). But in nymphs V, collected in July and August, we observed both first and second meiotic divisions – the spermatogenesis process was still going on. The differences between the phenology data for I. cimicoides, reported for northern parts of its range (Central Europe and West Siberia), and the data obtained in the present study could be a result of an adaptation of the species to the climate specific for South-Eastern Europe (in particular, Bulgaria).

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