Search Results (6)

Many researchers have used the species composition, relative abundance and distribution pattern of profundal benthic macroinvertebrate communities in particular, especially chironomid fauna, as indicators of the trophic state and pollution of lakes. In addition, compared with previous benthic macroinvertebrate data, it is expected that the process of eutrophication/oligotrophication of lakes can also be traced. Benthic macroinvertebrate distribution was studied in Lake Kawaguchi, Japan (maximum depth 16.1 m; mean depth 9.3 m), on 7 March 2025. The benthic animals identified were aquatic oligochaetes, chironomid larvae, shellfish and others. Differences among environmental factors and zoobenthos densities and rank correlation were analyzed using a non-parametric test. The mean density of oligochaetes, which was the dominant group, was 2457 ± 1247 individuals/m², followed by chironomid larvae at 816 ± 391 individuals/m². The larvae of Propsilocerus akamusi were the most abundant species at 669 ± 358 individuals/m², followed by Chironomus plumosus at 109 ± 114 individuals/m². Other chironomids (38 ± 75 individuals/m²) were also captured. Benthic communities were collected at all sites, but each taxa had its own characteristics. Oligochaetes and C. plumosus were widely distributed throughout the lake, whereas the distribution of P. akamusi was skewed toward the western part of the lake. In comparison with previous studies, P. akamusi larvae were now found to be the most abundant chironomid species in this lake, accounting for an increased percentage of the chironomid community, while C. plumosus larvae had decreased in recent years. In addition, the higher levels of organic matter in the upper sediment layer of the lake suggest ongoing eutrophication. Previous studies classified Lake Kawaguchi as mesotrophic–eutrophic, but reconsideration of this classification is warranted given the above findings. We suggest that this lake be ranked as a eutrophic lake (chlorophyll-a concentration; ca. 0.05 mg/L) based on a long-term investigation of the changes in chironomid fauna. Full article

Propsilocerus akamusi (Tokunaga, 1938) larvae serve as key bioindicators for water quality assessment. This study identifies optimal reference genes for RT-qPCR under diverse experimental conditions. Fifteen candidate genes commonly employed in other insect species were selected, candidate genes commonly used in other insect species. Homologous genes were identified in the P. akamusi genome through sequence alignment with their Drosophila melanogaster counterparts. Expression stability across developmental stages, body parts, temperature variations, and deltamethrin/nickel chloride exposures was systematically evaluated using geNorm, NormFinder, BestKeeper, and ΔCt methods. RPL32 exhibited the highest expression stability across different body parts of adults under varying temperature conditions, and RPS11 and RPL8 showed the greatest stability across developmental stages and in larvae exposed to different temperatures. Furthermore, under nickel chloride and deltamethrin treatments, RPS11 and RPL8 maintained the highest expression stability. The results indicated that the expression stability of reference genes varied under different conditions. Among different body parts of adults, RPL32 and RPL4 exhibited the most stable expression. Across different developmental stages, RPS11 and RPL8 performed best in terms of expression stability. Under different temperature treatments, RPL32 and RPL4 remained stable in adults, while RPS11 and RPL8 showed the greatest stability in larvae. Similarly, under nickel chloride and deltamethrin treatments, RPS11 and RPL8 demonstrated the most stable expression in larvae. Through the above research, we can advance ecosystem-impact insights and bolster environmental protection and water quality monitoring. Full article

Cytochrome P450 monooxygenases (P450s) are one of the most widespread enzyme superfamilies in the biological world. In insects, P450 proteins play a crucial role in the synthesis of endogenous substances and the metabolism of xenobiotics. To date, extensive research has been conducted on P450 gene-mediated detoxification and metabolism across multiple insect species. While Chironomidae species—dominant benthic organisms inhabiting diverse ecological niches and playing critical ecological roles—remain largely uncharacterized in terms of P450 protein annotation, with the exception of a single study on Propsilocerus akamusi. In this study, we expanded the annotation scope by identifying the P450 protein genes in eight additional Chironomidae species. A total of 577 P450 protein genes were annotated across the eight species, which could be classified into the following four distinct clans: 50 belonging to the CYP2 clan, 258 to the CYP3 clan, 198 to the CYP4 clan, and 71 to the Mito clan. Phylogenetic analysis using Drosophila melanogaster as an outgroup revealed that the CYP2 clan and the Mito clan are highly conserved during evolution, while the CYP3 clan and the CYP4 clan have undergone significant expansion. Most P450 proteins in Chironomidae species exhibit clear orthologous relationships with their D. melanogaster counterparts. Our research contributes to a better understanding of the evolutionary processes and the physiological functions of P450 proteins in Chironomidae species and lays the foundation for elucidating the role of P450 in environmental adaptability among the Chironomidae species inhabiting diverse habitats. Full article

The exoskeleton of insects, known as the cuticle, necessitates regular renewal during molting and metamorphosis, with chitin being its primary structural component. Consequently, the molting and metamorphosis processes in insects are characterized by periodic degradation and synthesis of chitin, which are tightly regulated by juvenile hormone (JH) and 20-hydroxyecdysone (20E). Propsilocerus akamusi, a species that plays a crucial role in freshwater ecosystems, demonstrates remarkable resilience to environmental pollutants, including metallic elements found in industrial waste. In this investigation, we systematically analyzed and summarized the metabolic pathways associated with JH, 20E, chitin, and heavy metal transport in P. akamusi. Based on previous genome assembly, we conducted a systematic annotation and functional analysis of genes involved in these metabolic pathways in P. akamusi. This was achieved by querying conserved domains using Pfam and SMART, as well as identifying gene-specific classical consensus regions through amino acid sequence alignment using DNAMAN. Through our validation, a total of 109 genes were definitively categorized into four distinct metabolic pathways: 27 genes were involved in the JH metabolic pathway, 24 in the 20E metabolic pathway, 27 in the chitin metabolic pathway, and 31 in metal transport pathways. A total of 30 genes failed our validation and were temporarily excluded. Furthermore, through RNA sequencing (RNA-seq)-based transcriptome analysis, we observed that under copper (Cu) stress, the expression levels of the majority of genes participating in these metabolic pathways in P. akamusi were altered. This finding suggests that copper exposure influences the molting process in P. akamusi. Full article

Plenty of freshwater species, especially macroinvertebrates that are essential to the provision of numerous ecosystem functions, encounter higher mortality due to acute hypoxia. However, within the family Chironomidae, a wide range of tolerance to hypoxia/anoxia is displayed. Propsilocerus akamusi depends on this great tolerance to become a dominant species in eutrophic lakes. To further understand how P. akamusi responds to acute hypoxic stress, we used multi-omics analysis in combination with histomorphological characteristics and physiological indicators. Thus, we set up two groups—a control group (DO 8.4 mg/L) and a hypoxic group (DO 0.39 mg/L)—to evaluate enzyme activity and the transcriptome, metabolome, and histomorphological characteristics. With blue–black chromatin, cell tightness, cell membrane invagination, and the production of apoptotic vesicles, tissue cells displayed typical apoptotic features in the hypoxic group. Although lactate dehydrogenase (LDH), alcohol dehydrogenase (ADH), catalase (CAT), and Na+/K+ -ATPase (NKA) activities were dramatically enhanced under hypoxic stress, glycogen content, and superoxide dismutase (SOD) activities were significantly reduced compared to the control group. The combined analysis of the transcriptome and metabolome, which further demonstrated, in addition to carbohydrates, including glycogen, the involvement of energy metabolism pathways, including fatty acid, protein, trehalose, and glyoxylate cycles, provided additional support for the aforementioned findings. Lactate is the end product of glycogen degradation, and HIF-1 plays an important role in promoting glycogenolysis in acute hypoxic conditions. However, we discovered that the ethanol tested under hypoxic stress likely originates from the symbiodinium of P. akamusi. These results imply that some parameters related to energy metabolism, antioxidant enzyme activities, and histomorphological features may be used as biomarkers of eutrophic lakes in Chironomus riparius larvae. The study also provides a scientific reference for assessing toxicity and favoring policies to reduce their impact on the environment. Full article

Chironomids commonly dominate macroinvertebrate assemblages in aquatic habitats and these non-biting midges are known for their ability to tolerate contaminants. Studies regarding the interplay between gut microbiota and host detoxification ability is currently a point of interest. Cytochrome P450s (P450s) are critical metabolic enzymes in which a subset is involved in xenobiotic detoxification. In this study, we first conducted an integrated global investigation of P450s based on the whole genomic sequence of Propsilocerus akamusi and retrieved a series of 64 P450 genes which were further classified into 4 clans and 25 families on the basis of phylogenetic relationships. With assistance of RNA-Seq and RT-qPCR validation, the expression profile of screened PaP450s in guts was compared between chlorpyrifos-challenged larvae with deficient gut microbiota (GD) and those with a conventional gut community (CV). An increasing prevalence of chlorpyrifos from sublethal to lethal dosages induced a greater mortality rate of individuals coupled with remarkable downregulation of 14 P450s in GD larval guts when compared to CV ones. Moreover, it turned out that the decreased level of PaCYP3998B1 and PaCYP3987D1 might imply impaired host endogenous detoxification capability potentiated by gut dysbiosis, reflected by a remarkably severe mortality in GD larvae treated with lethal chlorpyrifos. Collectively, our study unveiled candidate P450 genes that might be mediated by gut symbionts in chlorpyrifos-challenged P. akamusi larvae, possibly facilitating further understanding of the detoxified mechanism that chironomids might employ to alleviate poisonousness. Full article