First chromosomal study of Mantophasmatodea: Karyotype of Karoophasma biedouwense (Austrophasmatidae)

Dorota Lachowska-Cierlik,Valentina Kuznetsova,Mike Picker,Anna Maryańska-Nadachowska

doi:10.14411/eje.2015.093

Abstract

We have investigated for the first time the chromosomes of Karoophasma biedouwense, a species belonging to the Mantophasmatodea, a recently discovered order of carnivorous insects. Our study has revealed that males of this species display testes with numerous seminal tubes (follicles), as in other Polyneoptera, and short tubular seminal vesicles embedded in a utricular gland. The karyotype consists of 2n = 12A + X and biarmed, meta/submetacentric chromosomes (fundamental number of arms: FN = 26) with blocks of heterochromatin around centromeres. The autosomes are classified into two size groups, one represented by a single, very large pair of autosomes, the other by five smaller pairs which constitute a continuous series gradually decreasing in size. Among monocentric orders of Polyneoptera, K. biedouwense shares its low chromosome number, 2n = 13, as also found with some Orthoptera (Acridoidea, Grylloidea, Gryllacridoidea). Male meiosis is of the classical pre-reductional type and the X(0) sex determination system is probably an ancestral state. Use of FISH along with an 18S rDNA probe revealed multiple ribosomal clusters, which most likely represent an apomorphic condition. We identified the ancestral insect telomeric sequence (TTAGG)n in the terminal areas of the chromosomes. Currently available data on the polyneopteran orders putatively related to Mantophasmatodea showed a wide variability of cytogenetic characteristics within and between them. The only character allowing some tentative inference to be made on the ancestry of K. biedouwense is its low chromosome number, the karyotypic pattern so far unreported for the Polyneoptera except in certain Orthoptera.

Highlights

Mantophasmatodea is the most recently discovered insect order
We investigated the chromosomes of the recently discovered insect order Mantophasmatodea for the first time using the South African species, Karoophasma biedouwense
The study revealed that the testes have numerous seminal tubes, whilst the chromosomes themselves have a monocentric morphology and the karyotype consisting of 2n = 12A + X and biarmed, meta/submetacentric chromosomes

Summary

Introduction

Mantophasmatodea is the most recently discovered insect order. These carnivorous insects (heelwalkers, rock crawlers or gladiators) were first described from Eocene Baltic amber fossils (Zompro, 2001), whilst amazingly, living specimens were found in Southern Africa at the turn of this century (Klass et al, 2002; Picker et al, 2002). The unique development of the neuroendocrine capa-neurons in the central nervous system was described as a synapomorphy of Mantophasmatodea + Grylloblattodea (Predel et al, 2012) This clade was recovered in the phylogenetic study based on a secondary structure model of the complete 28S rRNAs (Wang et al, 2013) and thoracic morphology (Wipfler, 2015). All these data from multiple sources have supported the unification of Mantophasmatodea + Grylloblattodea = Notoptera, and confirmed that it represents one of the major lineages of the “lower Neoptera” (Terry & Whiting, 2005, Wipfler et al, 2014). Mantophasmatodea currently comprises 19 described extant and 5 extinct species, with at least five more undescribed species (Buder & Klass, 2013)

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