Abstract
Myrmeleontidae, commonly known as “antlions”, are the most diverse family of the insect order Neuroptera, with over 1700 described species (in 191 genera) of which 37 species (in 21 genera) have so far been studied in respect to standard karyotypes. In the present paper we provide first data on the occurrence of the “insect-type” telomeric repeat (TTAGG)n and location of 18S rDNA clusters in the antlion karyotypes studied using fluorescence in situ hybridization (FISH). We show that males of Palpares libelluloides (Linnaeus, 1764) (Palparinae), Acanthaclisis occitanica (Villers, 1789) (Acanthaclisinae) and Distoleon tetragrammicus (Fabricius, 1798) (Nemoleontinae) have rDNA clusters on a large bivalent, two last species having an additional rDNA cluster on one of the sex chromosomes, most probably the X. (TTAGG)n - containing telomeres are clearly characteristic of Palpares libelluloides and Acanthaclisis occitanica; the presence of this telomeric motif in Distoleon tetragrammicus is questionable. In addition, we detected the presence of the (TTAGG)n telomeric repeat in Libelloides macaronius (Scopoli, 1763) from the family Ascalaphidae (owlflies), a sister group to the Myrmeleontidae. We presume that the “insect” motif (TTAGG)n was present in a common ancestor of the families Ascalaphidae and Myrmeleontidae within the neuropteran suborder Myrmeleontiformia.
Highlights
The ends of eukaryotic chromosomes are capped with complex nucleoprotein structures, the telomeres, which preclude fusion, recombination and degradation of the chromosome ends and maintain the genome integrity
We show that males of Palpares libelluloides (Linnaeus, 1764) (Palparinae), Acanthaclisis occitanica (Villers, 1789) (Acanthaclisinae) and Distoleon tetragrammicus (Fabricius, 1798) (Nemoleontinae) have rDNA clusters on a large bivalent, two last species having an additional rDNA cluster on one of the sex chromosomes, most probably the X. (TTAGG)n - containing telomeres are clearly characteristic of P. libelluloides and A. occitanica; the presence of this telomeric motif in D. tetragrammicus is questionable
We detected the presence of the (TTAGG)n telomeric repeat in Libelloides macaronius (Scopoli, 1763) from the family Ascalaphidae, a sister group to the Myrmeleontidae
Summary
The ends of eukaryotic chromosomes are capped with complex nucleoprotein structures, the telomeres, which preclude fusion, recombination and degradation of the chromosome ends and maintain the genome integrity. In a large number of organisms, telomeric DNA consists of highly repetitive short sequences. Telomeres are diversified in their DNA sequence composition in different eukaryotic groups, several phylogenetic lineages demonstrate highly conserved motifs. Three main types of telomeric repeats are known: TTAGGG, TTAGGC, and TTAGG. The (TTAGG)n telomeric motif is commonly found among different higher insect taxa, and this telomere structure is supposed to be phylogenetically ancestral in the class Insecta in general (Frydrychová et al 2004). The insect-type consensus telomeric sequence is known to be lost independently during insect evolution (Frydrychová et al 2004, Lukhtanov and Kuznetsova 2010, Gokhman et al 2014). It is worth noting that the number of species with known telomere structure is extremely low in each insect order, including Neuroptera (Frydrychová et al 2004)
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