Ultrastructural alterations in sperm formation of the beetle, Blaps polycresta (Coleoptera: Tenebrionidae) as a biomonitor of heavy metal soil pollution

Abstract

Little is known about ultrastructural alterations induced by heavy metals pollution in insects. Therefore, the main objective of the present study is to elucidate ultrastructural changes in sperm formation of the tenebrionid beetle, Blaps polycresta as a biomonitor of heavy metal soil pollution. Metal percentages in testicular tissues of adult insects collected from reference and polluted sites were estimated using energy-dispersive X-ray microanalysis (EDX). Only cadmium, among eight detected metals, showed significantly higher percentages in the polluted testes compared with the reference ones. Ultrastructure investigation revealed severe alterations both in spermatogenic and spermiogenic stages of the polluted insects. Some cells were totally eroded. No spermatozoa were observed in all the examined cysts. Most degenerations were confined to the flagella of spermatids having enlarged vacuolated cytoplasm and malformed mitochondrial derivatives. Groups of multiple axial filaments were appeared in the form of bi-and tetra-flagellate spermatids. Electron dense vesicles were observed in almost all stages of the polluted testes. It is a novel trend in which ultrastructural alterations in sperm formation of insects could be used as a promising biomonitoring and risk assessment tool for heavy metal soil pollution.

Beetles as Model Organisms in Physiological, Biomedical and Environmental Studies – A Review

“…The coleopterans may be found in almost every type of habitat in which any insect is found, and the niches that are inhabited by many species of Coleoptera are often inaccessible for other insects. Some beetle species are also immensely sensitive to changes occurring in their environments (Osman and Shonouda, 2017; Shonouda and Osman, 2018). Taking this fact into consideration along with well-established and standardized collecting methods (Spence and Niemelä, 1994) and readily available keys for identification, coleopterans are perfect organisms for bioindication.…”

“…Ground beetles (Carabidae) are the most commonly used bioindicators, notably when trying to assess environmental pollution (Abildsnes and Tømmerås, 2000; Ghannem et al, 2018). Other families, such as Curculionidae, Tenebrionidae, and Staphylinidae, are also used (Shonouda and Osman, 2018). Agricultural activities strongly influence the assemblage of ground beetles found in woody habitats and grasslands.…”

“…Similar results were obtained for P. cupreus whose body size decreases notably with an increase of heavy metals in food (Maryanski et al, 2002). In addition to direct toxic effects, heavy metal pollutants may alter locomotory behavior, as was shown in larvae of P. cupreus exposed to copper (Bayley et al, 1995), and it affects reproducibility by causing degeneration of the flagella of spermatids (Shonouda and Osman, 2018).…”

Relative gene expression, micronuclei formation, and ultrastructure alterations induced by heavy metal contamination in Pimelia latreillei (Coleoptera: Tenebrionidae) in an urban-industrial area of Alexandria, Egypt

“…As metal ions traverse cell barriers, the balance of extracellular and intercellular ions is interrupted, which affects membrane permeability [11]. Therefore, insects, including ground beetles have been used as bioindicators to monitor environmental pollution and in particular, soil pollution by heavy metals [12][13][14][15]. Ground beetles inhabit most of the biogeographical regions and are simply sampled from their habitats, and their bionomics and systematics are well studied [16].…”

“…Insects possess special structures, spherites for accumulating trace metals [34]. Accumulation of heavy metals in insect organs influences cell viability and induces cellular damage, as well as cell apoptosis [14,[35][36][37]. Heavy metals may affect the regulation and control mechanisms of the reproductive process, leading to spermatogenetic alterations, which, in turn, can result in the production of damaged spermatozoa [38][39][40].…”