Chironomus gelhausi, a new species of surface-mating Chironomus Meigen, 1803 (Diptera: Chironomidae) from Mongolia.

The adult male and female of Chironomus gelhausi n. sp. are described from a small lake in western Mongolia. Based on field observations and morphological characters, C. gelhausi is a surface-mating species which has retained the ability to fly. Morphological characteristics associated with surface-mating in this species include apically truncated wings, reduced antennal plume in the male, reduced palps, reduced mid and hind leg length, and enlarged hypopygium. Behavioral observations and morphology of C. gelhausi indicate that this species is a species of Chironomus which has independently evolved morphological characteristics consistent with surface-mating behavior similar to that of Fleuria and other species within Chironomus sensu lato. We can assume that this behavior and the associated morphological characteristics are related to survival in a harsh environment where high winds could displace aerial mating swarms from the larval habitat.

Chironomidae (Diptera) species diversity of estuaries across a land use gradient on the Caribbean coast of Costa Rica / Diversidad de especies de Chironomidae (Diptera) de estuarios en un gradiente de uso de suelo en la costa Caribe de Costa Rica

Abstract The family Chironomidae (Diptera) is the most widely distributed, most diverse, and often the most abundant of all families of benthic macroinvertebrates in aquatic ecosystems, including estuaries and other coastal marine ecosystems. Chironomid assemblages are likely to provide a useful measure of biotic integrity in estuaries of Costa Rica, which lack an intensive estuarine bioassessment tool to support environmental monitoring and regulatory programs. We characterized the taxonomic composition of Chironomidae, tested a Chironomidae Index of Biotic Integrity (CIBI) developed from extrinsic pollution tolerance values for its efficacy in evaluating the surface water quality and physical habitat, and made recommendations for increasing the sensitivity of the CIBI to detect differing degrees of stress across a range of estuaries in Costa Rica. Specifically, we selected nine estuaries within six different watersheds across a land use gradient located on the Caribbean coast of Costa Rica and collected Chironomidae surface-floating pupal exuviae (SFPE) samples biannually for two consecutive years (July 2012, Jan. 2013, July 2013, Jan. 2014). We identified 228 morphospecies and 70 genera from 17 071 Chironomidae pupal exuviae collected from nine estuaries, which ranked in the following order from lowest to highest biotic integrity based on CIBI scores: Estero Negro, Laguna Cuatro, Laguna Jalova, Laguna del Tortuguero, Río Parismina, Laguna Barra del Colorado, Río Pacuare, Río Bananito, and Río Estrella. The CIBI successfully differentiated between estuaries with poor versus good biotic integrity, indicating that CIBI could be used to evaluate the surface water quality and physical habitat of Costa Rican estuaries. We recommend that future studies refine our approach by developing regionally accurate genus and corresponding species-level tolerance values to improve the sensitivity of the CIBI for biological monitoring of Costa Rican estuaries. Rev. Biol. Trop. 66(3): 1118-1134. Epub 2018 September 01.

Resumen La familia Chironomidae (Diptera) es la más ampliamente distribuida, más diversa y a menudo, la más abundante de todas las familias de macroinvertebrados bentónicos en ecosistemas acuáticos, incluyendo estuarios y otros ecosistemas marinos. Probablemente, los ensambles de quironómidos proporcionen una medida útil de integridad biótica en estuarios de Costa Rica, los cuales carecen de una herramienta de evaluación biológica que respalde programas de monitoreo ambiental y programas regulatorios. Caracterizamos la composición taxonómica de Chironomidae, probamos un Índice de Integridad Biótica de Chironomidae (CIBI) desarrollado a partir de valores de tolerancia de contaminación extrínseca, por su eficacia en evaluar la calidad de la superficie del agua y el hábitat físico. Además, realizamos recomendaciones para incrementar la sensibilidad del CIBI para detectar diferentes grados de estrés en un rango de estuarios en Costa Rica. Específicamente, seleccionamos nueve estuarios dentro de seis cuencas diferentes a lo largo de un gradiente de uso de suelo en la costa Caribe de Costa Rica y recolectamos muestras de las exuvias pupales que flotan en la superficie (SFPE) por dos años consecutivos (Julio 2012, Enero 2013, Julio 2013, Enero 2014). Identificamos 228 morfoespecies y 70 géneros de 17 071 exuvias de pupas de Chironomidae recolectadas en nueve estuarios, los cuales se clasificaron en el siguiente orden de menor a mayor integridad biótica basado en los valores del CIBI: Estero Negro, Laguna Cuatro, Laguna Jalova, Laguna del Tortuguero, Río Parismina, Laguna Barra del Colorado, Río Pacuare, Río Bananito, y Río Estrella. El CIBI diferenció eficazmente entre estuarios con integridad biótica pobre versus buena, indicando que el CIBI puede ser usado para evaluar la calidad de la superficie del agua y el hábitat físico de estuarios de Costa Rica. Recomendamos que estudios futuros refinen nuestro planteamiento desarrollando valores de tolerancia de géneros precisos regionalmente y niveles correspondientes de especies para mejorar la sensibilidad del CIBI para el monitoreo de estuarios de Costa Rica.

Two new species of genus Hydrosmittia Ferrington & Sæther (Diptera: Chironomidae) from China.

The genus Hydrosmittia from China is reviewed. Two new species H. continalinea sp. n. and H. sipinata sp. n. are described and illustrated based on male imagines. Key to known male imagines of genus Hydrosmittia worldwide is provided.

Sympotthastia wuyiensis sp. n. from China, with description of the immature stages of S. takatensis (Tokunaga) (Diptera, Chironomidae).

Sympotthastia wuyiensis sp. n. is described and illustrated as male imago from China. The immature stages of S. takatensis (Tokunaga) are described. The generic diagnosis is emended. Key to the known adult males, larvae and pupae of the genus worldwide is presented.

First record of Odontomesa Pagast from China, with description of the immature stages of O. ferringtoni Sæther (Diptera, Chironomidae, Prodiamesinae).

The genus Odontomesa Pagast is newly recorded from China. Based on associated material collected from China and U.S.A, the immature stages of Odontomesa fulva (Kieffer) and Odontomesa ferringtoni Sæther are redescribed. Odontomesa sp. A Sæther is confirmed as conspecific with O. ferringtoni. The generic diagnosis of immature stages is emended. Keys to the known larvae and pupae of the genus are presented.

Use of Chironomidae (Diptera) Surface-Floating Pupal Exuviae as a Rapid Bioassessment Protocol for Water Bodies.

Rapid bioassessment protocols using benthic macroinvertebrate assemblages have been successfully used to assess human impacts on water quality. Unfortunately, traditional benthic larval sampling methods, such as the dip-net, can be time-consuming and expensive. An alternative protocol involves collection of Chironomidae surface-floating pupal exuviae (SFPE). Chironomidae is a species-rich family of flies (Diptera) whose immature stages typically occur in aquatic habitats. Adult chironomids emerge from the water, leaving their pupal skins, or exuviae, floating on the water's surface. Exuviae often accumulate along banks or behind obstructions by action of the wind or water current, where they can be collected to assess chironomid diversity and richness. Chironomids can be used as important biological indicators, since some species are more tolerant to pollution than others. Therefore, the relative abundance and species composition of collected SFPE reflect changes in water quality. Here, methods associated with field collection, laboratory processing, slide mounting, and identification of chironomid SFPE are described in detail. Advantages of the SFPE method include minimal disturbance at a sampling area, efficient and economical sample collection and laboratory processing, ease of identification, applicability in nearly all aquatic environments, and a potentially more sensitive measure of ecosystem stress. Limitations include the inability to determine larval microhabitat use and inability to identify pupal exuviae to species if they have not been associated with adult males.

Characterization of Chironomidae (Diptera) surface-floating pupal exuviae sample sort time from coastal tropical aquatic systems.

Many studies either ignore chironomids or only identify specimens to subfamily or tribe due to the associated difficulty and high cost with processing and identifying larvae. An efficient form of sampling chironomids involves collections of surface-floating pupal exuviae (SFPE). SFPE sample sorting has been shown to be more time efficient than traditional dip-net methods in temperate urban and peri-urban streams. However, no published studies have tested the time efficiency of SFPE sample sorting from coastal tropical aquatic systems. We calculated sort times for SFPE samples collected from a coastal tropical stream and an estuary and used multiple linear regression analysis to quantify the relationship between sample sort time and number of specimens, average body length of specimens, and dry weight of sample residue. The average amount of time required to sort very small samples was 69.3 min, while moderate samples averaged 85.6 min and large samples averaged 153.5 min. However, on average, small samples were nine times more time consuming per specimen than large samples. Additionally, dry weight of small-sized residue and the number of specimens contributed significantly to sort time. Therefore, we recommend collecting larger samples, which can be achieved by sampling for 20 min over 200-m reaches for stream sites and 500- to 1,000-m reaches for riverine and estuarine sites. Also, we suggest collecting during periods of low wave action and disturbance by boat wake to reduce the amount of sample residue. This research will enhance project planning and budgeting of future studies using the SFPE method to monitor coastal tropical aquatic systems.

The effects of subsampling and sampling frequency on the use of surface-floating pupal exuviae to measure Chironomidae (Diptera) communities in wadeable temperate streams.

Community, diversity, and biological index metrics for chironomid surface-floating pupal exuviae (SFPE) were assessed at different subsample sizes and sampling frequencies from wadeable streams in Minnesota (USA). Timed collections of SFPE were made using a biweekly sampling interval in groundwater-dominated (GWD) and surface-water-dominated (SWD) streams. These two types of stream were sampled because they support different Chironomidae communities with different phenologies which could necessitate sampling methodologies specific to each stream type. A subsample size of 300 individuals was sufficient to collect on average 85% of total taxa richness and to estimate most metrics with an error of about 1% relative to 1,000 count samples. SWD streams required larger subsample sizes to achieve similar estimates of taxa richness and metric error compared to GWD streams, but these differences were not large enough to recommend different subsampling methods for these stream types. Analysis of sample timing determined that 97% of emergence occurred from April through September. We recommend in studies where estimation of winter emergence is not important that sampling be limited to this period. Sampling frequency also affected the proportion of the community collected. To maximize the portion of the community, collected samples should be taken across seasons although no specific sampling interval is recommended. Subsampling and sampling frequency was also assessed simultaneously. When using a 300-count subsample, a 4-week sampling interval from April through September was required to collect on average 71% of the community. Due to differences in elements of the chironomid community evaluated by different studies (e.g., biological condition, phenology, and taxonomic composition), richness estimates are documented for five sampling intervals (2, 4, 6, 8, 10, and 12 weeks) and five subsample sizes (100, 200, 300, 500, and 1,000 counts). This research will enhance future studies by providing guidelines for tailoring SFPE methods to study specific goals and resources.

Assessing macroinvertebrate biodiversity in freshwater ecosystems: advances and challenges in DNA-based approaches.

Assessing the biodiversity of macroinvertebrate fauna in freshwater ecosystems is an essential component of both basic ecological inquiry and applied ecological assessments. Aspects of taxonomic diversity and composition in freshwater communities are widely used to quantify water quality and measure the efficacy of remediation and restoration efforts. The accuracy and precision of biodiversity assessments based on standard morphological identifications are often limited by taxonomic resolution and sample size. Morphologically based identifications are laborious and costly, significantly constraining the sample sizes that can be processed. We suggest that the development of an assay platform based on DNA signatures will increase the precision and ease of quantifying biodiversity in freshwater ecosystems. Advances in this area will be particularly relevant for benthic and planktonic invertebrates, which are often monitored by regulatory agencies. Adopting a genetic assessment platform will alleviate some of the current limitations to biodiversity assessment strategies. We discuss the benefits and challenges associated with DNA-based assessments and the methods that are currently available. As recent advances in microarray and next-generation sequencing technologies will facilitate a transition to DNA-based assessment approaches, future research efforts should focus on methods for data collection, assay platform development, establishing linkages between DNA signatures and well-resolved taxonomies, and bioinformatics.

Using the Sediment Quality Triad to characterize baseline conditions in the Anacostia River, Washington, DC, USA.

The Sediment Quality Triad (SQT) consists of complementary measures of sediment chemistry, benthic community structure, and sediment toxicity. We applied the SQT at 20 stations in the tidal portion of the Anacostia River from Bladensburg, MD to Washington, DC to establish a baseline of conditions to evaluate the effects of management actions. Sediment toxicity was assessed using 10-day survival and growth tests with the freshwater amphipod, Hyalella azteca and the midge, Chironomus dilutus. Triplicate grabs were taken at each station for benthic community analysis and the Benthic Index of Biotic Integrity (B-IBI) was used to interpret the data. Only one station, #92, exhibited toxicity related to sediment contamination. Sediments from this station significantly inhibited growth of both test species, had the highest concentrations of contaminants, and had a degraded benthic community, indicated by a B-IBI of less than 3. Additional sediment from this station was tested and sediment toxicity identification evaluation (TIE) procedures tentatively characterized organic compounds as the cause of toxicity. Overall, forty percent of the stations were classified as degraded by the B-IBI. However, qualitative and quantitative comparisons with sediment quality benchmarks indicated no clear relationship between benthic community health and contaminant concentrations. This study provides a baseline for assessing the effectiveness of management actions in the Anacostia River.

Symbiotic Harpellales (Trichomycetes) in Tasmanian aquatic insects.

Surveys for symbiotic fungi in the guts of aquatic insect larvae (Trichomycetes: Harpellales) in Tasmania, Australia, resulted in the discovery of four new species: two in Gripopterygidae (Plecoptera) nymphs, Plecopteromyces leptoperlarum and P. trinotoperlarum, and two associated with Diptera larvae, Smittium magnosporum in Thaumaleidae and Stachylina dolichospora in Chironomidae. Previously described species of Harpellales from other localities are reported and new host records summarized. A key to all Tasmanian species of Harpellales is provided.