Phylogeny and historical biogeography of the water boatmen (Insecta: Hemiptera: Heteroptera: Nepomorpha: Corixoidea)

Water boatmen (Heteroptera: Nepomorpha: Corixidae) of Romania

We here update the distribution and provide a checklist of the water boatmen (Hemiptera: Heteroptera: Corixoidea: Corixidae) of Romania based on country-wide sampling, a literature survey, and private and museum collections. The Romanian fauna currently comprises 25 water boatmen species and subspecies in eight genera and two subfamilies. The occurrence of Glaenocorisa propinqua (Fieber, 1860), Arctocorisa carinata carinata (Sahlberg, 1819), and Corixa panzeri Fieber, 1848, all known from old and single records, is here confirmed. The first record of an intermediate shape of the pala between Sigara falleni (Fieber, 1848) (triangular) and S. iactans Jansson, 1983 (trapezoidal) is reported from the southeastern European population of the latter, suggesting possible hybridization.

Utilizing Insects as Bioindicators: An Approximation for Conservation in Urban Lentic Ecosystems in Central Chile

This study considered using insect families as bioindicators to establish the health status of an ecosystem of lentic bodies. The water quality in urban lentic bodies in the Metropolitan Region, Chile, was evaluated from aquatic insect family assemblages and physicochemical variables for conserving aquatic life. Evaluations were carried out in parallel at four sampling stations of three water bodies (Batuco Wetland, Carén Lagoon, and Chada Reservoir) in a 2-3-year series, spring (2015, 2017, and 2018) and fall (2016 and 2018), with three replicates. Families were randomly sampled and aquatic insects were identified; abundance and richness differences were compared with non-parametric tests. Physicochemical variables were measured using portable multiparametric and laboratory chemical analyses to determine the water quality. A Canonical Correspondence Analysis was applied for insect families and the physical-chemical variable. In order to categorize the health of these water bodies based on aquatic insect composition and abundance, the Family Biotic Index (FBI), British Biological Monitoring Work Party (BMWP), and Stream Invertebrate Grade Number-Average Level (SIGNAL), adapted for Chile by Figueroa et al. (2007), were calculated. The eudominant insect families were Corixidae and Chironomidae in Batuco, Chironomidae and Corixidae in Carén, and Corixidae in Chada. Baetidae was dominant in Carén and Chada. The water bodies were classified in descending order of water quality by Chilean physicochemical standards: Chada > Carén > Batuco. The TSS (total suspended solids), phosphorus, and electrical conductivity were strongly positively correlated and negatively associated with dissolved oxygen. The TSS level was the most significant influential factor. The BMWP value and the SIGNAL differed from the FBI, but the first was more restrictive, contributing to the conservation of these ecosystems. Based on the nitrogen and phosphorus levels in the water bodies, all of them were eutrophic. Given the ecosystem diversity and complexity, studies should delve deeper into wetlands to establish methods that contribute to determining water quality, using insect families as bioindicators and physicochemical variables.

DNA barcoding is currently unreliable for species identification in most crayfishes

DNA barcoding is commonly used for species identification. Despite this, there has not been a comprehensive assessment of the utility of DNA barcoding in crayfishes (Decapoda: Astacidea). Here we examined the extent to which local barcoding gaps (used for species identification) and global barcoding gaps (used for species discovery) exist among crayfishes, and whether global gaps met a previously suggested 10× threshold (mean interspecific difference being 10× larger than mean intra specific difference). We examined barcoding gaps using publicly available mitochondrial COI sequence data from the National Center for Biotechnology Information's nucleotide database. We created two versions of the COI datasets used for downstream analyses: one focused on the number of unique haplotypes (N H) per species, and another that focused on total number of sequences (N S; i.e., including redundant haplotypes) per species. A total of 81 species were included, with 58 species and five genera from the family Cambaridae and 23 species from three genera from the family Parastacidae. Local barcoding gaps were present in only 30 species (20 Cambaridae and 10 Parastacidae species). We detected global barcoding gaps in only four genera (Cambarus, Cherax, Euastacus, and Tenuibranchiurus), which were all below (4.2× to 5.2×) the previously suggested 10× threshold. We propose that a ~5× threshold would be a more appropriate working hypothesis for species discovery. While the N H and N S datasets yielded largely similar results, there were some discrepant inferences. To understand why some species lacked a local barcoding gap, we performed species delimitation analyses for each genus using the N H dataset. These results suggest that current taxonomy in crayfishes may be inadequate for the majority of examined species, and that even species with local barcoding gaps present may be in need of taxonomic revisions. Currently, the utility of DNA barcoding for species identification and discovery in crayfish is quite limited, and caution should be exercised when mitochondrial-based approaches are used in place of taxonomic expertise. Assessment of the evidence for local and global barcoding gaps is important for understanding the reliability of molecular species identification and discovery, but outcomes are dependent on the current state of taxonomy. As this improves (e.g., via resolving species complexes, possibly elevating some subspecies to the species-level status, and redressing specimen misidentifications in natural history and other collections), so too will the utility of DNA barcoding.

The complete mitochondrial genome of Sigara lateralis (Leach, 1817) (Nepomorpha: Corixidae)

The Sigara lateralis (Leach, 1817) is a small aquatic insect belonging to the family Corixidae. The study aims to reveal the genomic data of the mitochondrial genome of S. lateralis. The length of its circular mitochondrial genome is 15,725 bp long with an A + T bias (75.96%). The mitogenome comprises 37 genes, including 13 protein-coding genes (PCGs), 22 transfer RNA genes, and two rRNA genes. The phylogenetic analyses showed that the S. lateralis is the closest to S. septemlineata. These findings will help the conservation of Corixidae from the perspective of genetic evolution.

The Micronecta Kirkaldy, 1897 (Hemiptera: Heteroptera: Micronectidae) of Iran, with four new records and an illustrated key to the species

The fauna of Micronectidae (pygmy water boatmen) was investigated in Guilan Province. The present study has raised the number of micronectid species known from Iran to nine by reporting four first records for the country, including Micronecta carpatica Wrblewski, 1958, M. griseola Horvth, 1899, M. poweri (Douglas & Scott, 1869), and M. pusilla (Horvth, 1895). Morphological diagnoses for these four species are provided, accompanied by illustrations of male habitus, male genitalia, and a key to the species of Micronecta known from Iran.

Sexual selection and predation drive the repeated evolution of stridulation in Heteroptera and other arthropods

Acoustic and substrate-borne vibrations are among the most widely used signalling modalities in animals. Arthropods display a staggering diversity of vibroacoustic organs generating acoustic sound and/or substrate-borne vibrations, and are fundamental to our broader understanding of the evolution of animal signalling. The primary mechanism that arthropods use to generate vibroacoustic signals is stridulation, which involves the rubbing together of opposing body parts. Although stridulation is common, its behavioural context and evolutionary drivers are often hard to pinpoint, owing to limited synthesis of empirical observations on stridulatory species. This is exacerbated by the diversity of mechanisms involved and the sparsity of their description in the literature, which renders their documentation a challenging task. Here, we present the most comprehensive review to date on the systematic distribution and behavioural context of stridulation. We use the megadiverse heteropteran insects as a model, together with multiple arthropod outgroups (arachnids, myriapods, and selected pancrustaceans). We find that stridulatory vibroacoustic signalling has evolved independently at least 84 times and is present in roughly 20% of Heteroptera, representing a remarkable case of convergent evolution. By studying the behavioural context of stridulation across Heteroptera and 189 outgroup lineages, we find that predation pressure and sexual selection are the main behaviours associated with stridulation across arthropods, adding further evidence for their role as drivers of large-scale signalling and morphological innovation in animals. Remarkably, the absence of tympanal ears in most Heteroptera suggests that they typically cannot detect the acoustic component of their stridulatory signals. This demonstrates that the adoption of new signalling modalities is not always correlated with the ability to perceive those signals, especially when these signals are directed towards interspecific receivers in defensive contexts. Furthermore, by mapping their morphology and systematic distribution, we show that stridulatory organs tend to evolve in specific body parts, likely originating from cleaning motions and pre-copulatory displays that are common to most arthropods. By synthesising our understanding of stridulation and stridulatory organs across major arthropod groups, we create the necessary framework for future studies to explore their systematic and behavioural significance, their potential role in sensory evolution and innovation, and the biomechanics of this mode of signalling.