Cytogenetic investigations on some species of the family pentatomidae (insecta: hemiptera: heteroptera)

Abstract

The order Hemiptera comprises about 80,000 species which are distributed in two suborders: Homoptera and Heteroptera. Approximately 37,000 species distributed in 77 families belong to Heteroptera. Some of the major subfamilies of Heteroptera are Pentatomidae, Reduviidae, Coriedae, Lygaeidae, Miridae, Alydidae and Pyrrhocoridae. The Heteroptera includes a diverse assemblage of insects that have become adapted to a broad range of habitats: terrestrial, aquatic and semi-aquatic. Economically, plant feeding heteropterans are important pests of many crop plants. Predatory species are generally regarded as beneficial as they attack primarily lepidopteran and coleopteran larvae which are important pests in agro systems. Some heteropteran species received attention as potential biological control agents for agricultural pests. Cytogenetically, members of the suborder Heteroptera form an interesting group due to the presence of unique features. Heteropteran insects possess holocentric chromosomes (chromosomes with diffused centromere). Heteropterans are also characterized by the presence of a special stage of prophase called the diffuse stage where autosomes decondense while the sex chromosomes remain condensed. Another characteristic feature is the presence of an “inverted meiosis” (Post-reductional meiosis for sex chromosomes) wherein the autosomes segregate reductionally during anaphase I and equationally during anaphase II while sex chromosomes follow the reverse. Chromosome studies in Heteroptera have been limited only to reporting chromosome number and sex determining mechanisms as it is difficult to characterize chromosomes due to their small size and lack of primary constriction. Recently, differential staining techniques have developed and individual chromosome variations have been used for species differentiation in different groups of Heteroptera. C-banding, fluorescent banding and silver nitrate staining techniques are used to characterize constitutive heterochromatin, sequence specificity of the heterochromatin and nucleolar organizer regions respectively and these techniques reveal species specific cytogenetic markers. The Pentatomidae is one of the largest families of Heteroptera comprising about 642 genera and 4112 species distributed in eight subfamilies (Pentatominae, Asopinae, Podopinae, Edessinae, Phyllocephalinae, Discocephalinae, Cyrtocorinae and Serbaninae). Regardless of this rich biodiversity, cytogenetic work on Pentatomidae is meager with cytogenetic reports of only less than 400 species. Keeping in mind the economic importance of Pentatomidae and very meager knowledge on its cytogenetic aspects, this group has been selected for the present study in which a comprehensive work has been carried out on the cytogenetics of some representative species of the family by the use of both conventional and modern cytogenetic techniques. As many as 23 species belonging to the family Pentatomidae ((Aeliomorpha sheanensis, Apodiphus pilipes, Eysarcoris rosaceous, Halys seregera, Halys sulcata, Halyomorpha murrea, Nezara graminea, Piezodorus rubrofasciatus, Plautia fimbriata, Tropicoris punctipes, Bagrada picta, Carbula scutellata, Dollocoris baccarum, Erthesina fullo, Eurydema pulchrum, Eysarcoris inconspicuous, Nezara viridula, Priassus exemptus, Andrallus spinidens, Canthecona furcellata, Perillus bioculatus and Podops inuncta)have been collected referable to 3 subfamilies (Pentatominae Asopinae and Podopinae) and 19 genera from different localities of Punjab, Haryana, Himachal Pradeish and Uttrakhand states.