DNA barcode library revealed unknown diversity of chironomid midges in Montenegro

We present the first results of the study aiming to investigate the diversity of the non-biting midges (Diptera: Chironomidae) fauna of the Skadar Lake system (Montenegro and Albania), a well-known hotspot of freshwater biodiversity composed by the young lake Skadar (originated 1200 before present) and by its old system of springs (originated during Pliocene). During the study, 8,147 COI barcodes were obtained and revealed the presence of 474 BINs and 586 OTUs assigned to 148 species. Our results provide the first insight into the factual molecular diversity among chironomids inhabiting Skadar Lake basin and fill a significant gap in the knowledge of the biodiversity in the Balkan region. With 219 (46.2%) unique BINs from the Skadar Lake basin new for BOLD, we can expect that further development of barcode reference libraries will help to bind unidentified developmental stages with those identified based on morphology and will reveal hidden Chironomidae species diversity. Further studies should be focused on sampling developmental stages which provides the best species-level resolution, such as mature males. It will help to develop a reliable reference barcode library - fundamental during further assessments.

Wastewater treatment works change the intestinal microbiomes of insectivorous bats

Mammals, born with a near-sterile intestinal tract, are inoculated with their mothers’ microbiome during birth. Thereafter, extrinsic and intrinsic factors shape their intestinal microbe assemblage. Wastewater treatment works (WWTW), sites synonymous with pollutants and pathogens, receive influent from domestic, agricultural and industrial sources. The high nutrient content of wastewater supports abundant populations of chironomid midges (Diptera), which transfer these toxicants and potential pathogens to their predators, such as the banana bat Neoromicia nana (Vespertilionidae), thereby influencing their intestinal microbial assemblages. We used next generation sequencing and 16S rRNA gene profiling to identify and compare intestinal bacteria of N. nana at two reference sites and two WWTW sites. We describe the shared intestinal microbiome of the insectivorous bat, N. nana, consisting of seven phyla and eleven classes. Further, multivariate analyses revealed that location was the most significant driver (sex, body size and condition were not significant) of intestinal microbiome diversity. Bats at WWTW sites exhibited greater intestinal microbiota diversity than those at reference sites, likely due to wastewater exposure, stress and/or altered diet. Changes in their intestinal microbiota assemblages may allow these bats to cope with concomitant stressors.

Extracellular hemoglobin and environmental stress tolerance in Chironomus larvae

Hemoglobin (Hb) is one of the most common conserved molecules found in organisms belonging to all major kingdoms of life. Chironomid midge larvae are unique among the invertebrates being the only free-living group of organisms possessing extracellular hemoglobins (Hbs) in monomeric and dimeric forms floating in their hemolymph. Remarkable ability of individual species of chironomid midges to tolerate wide range of environmental stressors prevailing in their respective ecosystems has enabled chironomids to sustain as one of the most widely distributed insects in the world. Ability of different Chironomus spp to thrive under extreme hypoxic conditions as well as in the presence of chemical pollution made chironomid midges an efficient model system to assess the effect of environmental stress in different freshwater ecosystems. The modulation of Hb concentration has been found to be a function of different type of abiotic stressors and thus Hb of chironomid midges (Ch-Hb) has attracted the attention as a potential biomarker for environmental biomonitoring. Large body of literature on Ch-Hb accumulated mainly during sixties to eighties of twentieth century has enriched our understanding of its physiological, developmental and biochemical features. Empirical as well as in-silico studies carried out in recent years provided insights into many structure-function relationships of Ch-Hb. However, for the last few decades, majority of the studies were carried out to project and validate Ch-Hb as potential bioindicator for evaluating toxicants, chemical pollutants and environmental gradients of dissolved oxygen concentration. In this review, historical development of the subject has been compiled with notes on future implications of contemporary studies on Ch-Hb.

Aquatic silk proteins in Chironomus: A review

Silk proteins secreted by salivary glands in the dipteran insect, Chironomus play a significant role as proteinaceous adhesives for construction of underwater housing nests by larvae. To date, only three Chironomus species, C. tentans Fabricius, C. pallidivittatus Malloch and C. riparius Meigen have been explored for characterization of their aquatic silk protein. Genes coding for silk proteins are located on specific chromosomal ‘puffs’ called Balbiani rings as well as non-Balbiani ring regions. Expression of these genes is closely regulated by developmental and hormonal alterations and environmental factors. Furthermore, pilot studies have postulated that silk proteins probably occur in diverse size classes grouped into large (~1000 kDa), intermediate (100-200 kDa) and small (≤100 kDa). Barring few preliminary reports that date back to the 1990s, the physical and bioproperties of silk from chironomid midges remain largely unknown, leading to paucity of updated information. This review was therefore aimed to compile existing literature database and to highlight the wide possibilities for commercialization of midge larval silk as a novel biopolymer.