Research Article |
Corresponding author: Snejana Grozeva ( sgrozeva@yahoo.com ) Academic editor: María José Bressa
© 2019 Snejana Grozeva, Boris A. Anokhin, Nikolay Simov, Valentina G. Kuznetsova.
This is an open access article distributed under the terms of the CC0 Public Domain Dedication.
Citation:
Grozeva S, Anokhin BA, Simov N, Kuznetsova VG (2019) 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). Comparative Cytogenetics 13(3): 283-295. https://doi.org/10.3897/CompCytogen.v13i3.36676
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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.
Heteroptera, Rhynocoris punctiventris, R. iracundus, Nabis sareptanus, Horistus orientalis, TTAGG-FISH
The true bugs (Hemiptera: Heteroptera), with almost 45,000 described species distributed into 91 families and seven infraorders (
Primarily to address this issue, we did a (TTAGG)n FISH experiment involving four species of the Cimicomorpha, which have not previously been studied in respect to telomere composition. These are Nabis (Halonabis) sareptanus Dohrn, 1862 from the family Nabidae; Horistus orientalis (Gmelin, 1790) from the family Miridae; Rhynocoris punctiventris (Herrich-Schäffer, 1846) and R. iracundus (Poda, 1761) from the family Reduviidae, the subfamily Harpactorinae. Specifically, we looked for a strong evidence of the absence of the (TTAGG)n telomere motif in Nabidae and Miridae as well as an additional evidence of the presence of this motif in the family Reduviidae.
In addition, we aimed to detect the 18S rDNA loci in the above species. Finally, we characterized, for the first time, the karyotype and meiotic pattern of spermatogenesis in each of the species under study.
The true bug specimens were collected in May-June 2018, in Bulgaria. The localities from which the bugs were collected and the number of males and mitotic/meiotic preparations studied are given in Table
Species | Locality | Date of collection | Number of males/ preparations analysed by Shiff-Giemsa staining | Number of males/ preparations analysed by FISH |
---|---|---|---|---|
Rhynocoris punctiventris (Herrich-Schäffer, 1846) | Bulgaria, Kresna Gorge 41.762378N, 23.169228E | 23 May 2018 | 1/6 | 1/3 |
Rhynocoris iracundus (Poda, 1761) | 23 May 2018 | 3/11 | 2/5 | |
Horistus orientalis (Gmelin, 1790) | 23 May 2018 | 1/1 | 1/2 | |
Nabis (Halonabis) sareptanus Dohrn, 1862 | Bulgaria, Pomorie Lake 42.565609N, 27.630627E | 07 June 2018 | 3/5 | 1/1 |
For this staining, we followed the Schiff-Giemsa method described by
Probes for 18S rDNA and (TTAGG)n were prepared and FISH was performed according to
As a control for the efficacy of our (TTAGG)n FISH experiments, we used chromosome preparations from Scarlupella discolor (Germar, 1821) (Hemiptera: Auchenorrhyncha) known to be (TTAGG)n -positive (
The routinely stained preparations were analysed under a light microscope (Axio Scope A1 – Carl Zeiss Microscope) at 100× magnification and documented with a ProgRes MF Cool, Jenoptic (Jena, Germany). FISH images were taken using a Leica DM 6000 B microscope with a 100× objective, Leica DFC 345 FX camera, and Leica Application Suite 3.7 software with an Image Overlay module (Leica Microsystems, Wetzlar, Germany). The filter sets applied were A, L5 and N21 (Leica Microsystems). The specimens from which the chromosome preparations have been obtained are stored at the Institute of Biodiversity and Ecosystem Research, BAS (Sofia, Bulgaria).
Subfamily Harpactorinae
Tribe Harpactorini
Rhynocoris punctiventris, 2n ♂ = 28 (24A + X1X2X3Y), Figs
R. iracundus, 2n ♂ = 28 (24A + X1X2X3Y), Figs
Both species were found to have 28 chromosomes at spermatogonial metaphases (Figs
Rhynocoris punctiventris (1, 3, 4, 6b, 7) and R. iracundus (2, 5, 6a), 2n (♂) = 28 (24A + X1X2X3Y). Routine staining (1–4), FISH with 18S rDNA (green) and telomeric (TTAGG)n (pink) probes (5–7). 1, 5 spermatogonial metaphase 2 early condensation stage with four sex chromosome bodies 3, 6a, b metaphase I (MI) 4, 7 metaphase II (MII) with four sex chromosomes located in the center of the ring formed by autosomes. Hybridization signals of the (TTAGG)n probe are seen at the ends of chromosomes, and the signals of 18S rDNA FISH are seen on the Y chromosome and on one of the X chromosomes in both species (5–7). Scale bars: 10 μm.
Figures
Subfamily Nabinae
Tribe Nabini
Nabis (Halonabis) sareptanus, 2n ♂ = 34 (32A + XY), Figs
The chromosome complement of males studied here agrees with that reported earlier for males of this species originating from the Republic of Kazakhstan (
Nabis (Halonabis) sareptanus, 2n (♂) = 34 (32A + XY). Routine staining (9–12), FISH with 18S rDNA (green) and telomeric (TTAGG)n (pink) probes. (13, 14); 9, 14 condensation stage (9 at the early condensation stage, 2 univalent sex chromosomes are positively heteropycnotic and associate to one another via a nucleolus; arrowed) 10 MI 11 MII 12 anaphase II (AII) 13 spermatogonial metaphase. There are no hybridization signals of the (TTAGG)n probe; the signals of the 18S rDNA probe are seen on both X and Y chromosomes (13, 14). Scale bars: 10 μm.
FISH with the (TTAGG)n probe revealed no signals on chromosomal spreads of N. sareptanus (Figs
Subfamily Mirinae
Tribe Mirini
Horistus orientalis, 2n ♂ = 32 (30A + XY), Fig.
Fifteen bivalents of autosomes and a pseudo-bivalent composed of the X and Y sex chromosomes are present at early MI (Fig.
Horistus orientalis, 2n (♂) = 32 (30A + XY). FISH with 18S rDNA (green) and telomeric (TTAGG)n (pink) probes. Early MI – bivalents with one or occasionally two tenacious threads, the so-called collochores (arrowed). There are no hybridization signals of the (TTAGG)n probe; the signals of the 18S rDNA probe are seen on the XY sex chromosome pseudo-bivalent. Scale bar: 10 μm.
FISH with the (TTAGG)n probe revealed no signals on chromosomal spreads of H. orientalis suggesting thus that its telomeres lack, as in N. sareptanus, the “insect” telomere motif (TTAGG)n. The twin hybridization signals of the 18S rDNA probe were seen on the XY sex chromosome pseudo-bivalent; however, we failed to understand whether they were present on the X or on the Y chromosome. In two another species of the family Miridae studied previously in this respect, Deraeocoris rutilus (Herrich-Schaeffer, 1838) and D. ruber Linnaeus, 1758, both with an XY sex chromosome system, rDNA clusters were shown to be located on the X chromosome and on both X and Y chromosomes, respectively (
The major result of our work is a compelling support for the absence of the canonical “insect” telomeric TTAGG tandem repeat in the families Nabidae and Miridae (Table
Karyotypes and results of FISH mapping of telomere (TTAGG)n motif and 18S rDNA loci.
Taxon | 2n ♂ | Presence / absence of (TTAGG)n motif | Location of 18S rDNA loci |
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Family Reduviidae | |||
Rhynocoris punctiventris | 28 (24A + X1X2X3Y) | Present | Y and one of the X chromosomes |
Rhynocoris iracundus | 28 (24A + X1X2X3Y) | Present | Y and one of the X chromosomes |
Family Miridae | |||
Horistus orientalis | 32 (30A + XY) | Absent | One of the sex chromosomes (unidentified) |
Family Nabidae | |||
Nabis (Halonabis) sareptanus | 34 (32A + XY) | Absent | Both X and Y chromosomes |
With approximately 6,800 described species in 25 subfamilies, the assassin bugs represent one of the largest families within the order Hemiptera. Phylogeny and relationships within and between subfamilies of the Reduviidae are far from being resolved (
We thank Dr. Iliya Gyonov who collected Scarlupella discolor for this study. The present study was supported by the research project no. AAAA-A19-119020790106-0, by the research grant from the Russian Foundation for Basic Research no 17-04-00828, and by the program of Presidium RAS “Biodiversity of Natural Systems” (Genofunds of living nature and their conservation).