Leonard C. Ferrington

Global diversity of non-biting midges (Chironomidae; Insecta-Diptera) in freshwater

Chironomidae are common inhabitants of most aquatic habitats, and often dominate aquatic insect communities in both abundance and species richness. Species occur in all continents, including Antarctica, and most major oceanic islands that have been investigated. The family is divided into 11 subfamilies and 22 nominal tribes. Although individual species occur in a wide range of habitats from terrestrial to fully aquatic, a total of 339 genera and 4,147 species are unambiguously aquatic in their immature stages. Greatest species and generic richnesses occur in the Palaearctic Region and Nearctic Region, respectively, but this pattern may largely reflect historical patterns of past taxonomic research efforts.

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.

Trichomycetes in Argentinean aquatic insect larvae

Investigations of larval aquatic Diptera (Chironomidae, Simuliidae, Culicidae), Coleoptera (Scirtidae), and Plecoptera (Gripopterygidae, Notonemouridae) in Buenos Aires Province and three Provinces...

Winter Growth, Development, and Emergence of Diamesa mendotae (Diptera: Chironomidae) in Minnesota Streams

ABSTRACT Diamesa mendotae Muttkowski is commonly observed emerging during winter at low air temperatures from Minnesota streams, but little is known about the winter dynamics of this and other winter-emerging aquatic insects. Biweekly collections of surface-floating pupal exuviae indicated that this species emerged from October through May, when water temperatures were less than ≈10C. Emergence occurred continuously through winter, with a lull during January and February. Development of larvae from in situ growth enclosures supported emergence data and indicated that the reduction and halt of emergence in the spring was related to increasing water temperatures (>10°C), which were unsuitable for the growth or survival of the larvae. Development continued through January when water temperatures were at their lowest for the study stream and therefore did not explain the mid-winter lull in emergence. Growth rates of D. mendotae were not greater than other chironomid taxa at similar temperatures, indicating that lower critical thermal limits for growth allow this species to dominate ground-water influenced streams during the winter in Minnesota. The results of this study show that D. mendotae is well suited for growth and development at low temperatures and provides an assessment of important factors that regulate this species at low water and air temperatures.

Lower lethal temperature for adult male Diamesa mendotae Muttkowski (Diptera: Chironomidae), a winter-emerging aquatic insect

Abstract The supercooling point (SCP) and lower lethal temperature (LLT50) of male adult Diamesa mendotae Muttkowski (Diptera: Chironomidae) were determined from field-collected individuals. SCP determined using surface-contact thermometry did not differ statistically from previously reported values for a previous generation of this species. The LLT50 was determined by exposing individuals to −10, −15, −20, −25, and −30°C for one minute. Mean survivorship was 96.7, 91.2, and 71.2% for tests at −10, −15, and −20°C, respectively. Exposure to −25 and −30°C resulted in 100% mortality in all tests. Results show that males of D. mendotae are freeze-intolerant with a mean SCP of −21.6°C which is only 0.1°C lower than its linear interpolated estimated LLT50 of −21.5°C. Our results confirm that a low SCP, rather than freeze tolerance, is a mechanism that facilitates emergence and adult activity of this species during winter conditions. The implications of SCP and LLT50 with regard to life cycle dynamics are discussed.

Biological Assessment of Cannon Creek, Missouri by Use of Emerging Chironomidae (Insecta: Diptera)

Abstract A biological assessment was done to determine the impact of heavy metal discharge from the Schuykill Metals Recycling Plant (SMCP) on Cannon Creek, Missouri, its receiving stream. The relationship between sediment chemistry and chironomid emergence was examined. Twenty-four heavy metals and nutrients from the SMCP discharge effluent were examined in Cannon Creek from above the effluent, at the effluent, and below the effluent. Five heavy metals (barium, cadmium, lead, manganese, and zinc) and sodium varied significantly between sites. Changes in community composition, mean abundance of emerging chironomids, and Kansas Biotic Index Values were used to detect impairment by heavy metals and nutrients in Cannon Creek. Concentrations of lead and zinc in Cannon Creek were at levels potentially lethal to chironomids, yet mean abundance of emerging chironomids actually increased with the increase of heavy metals and nutrients and showed a strong and positive correlation with barium and sodium, and a weaker correlation with increases in lead and cadmium. Chironomid diversity patterns did not correlate with the concentrations of heavy metals in Cannon Creek. Community similarity between sites was greatest between the reference site and the site at the SMCP discharge effluent. Low similarity between sites was attributed to gross changes in stream morphology rather than to any effects from the SMCP effluent. Finally, the KBI tolerance values to heavy metals for chironomids in Cannon Creek were above those encountered in the reference condition for the Western Cornbelt Plains Ecoregion, indicating minimal impairment.

Effect of sex and age on the supercooling point of the winter-active Diamesa mendotae Muttkowski (Diptera: Chironomidae)

Supercooling points (SCP) of adult Diamesa mendotae Muttkowski, 1915 (Diptera: Chironomidae) were determined at 3, 5, 9, 12 and 17 days post-collection. Supercooling points were recorded using surface contact thermometry and a cooling rate of ca. 1°C min−1. Female SCPs averaged −22.81, −23.76, −23.85, −23.65, and −20.87°C on each date post-collection and did not differ significantly. Male SCPs were statistically similar and averaged −21.75, −23.53, −23.68, −23.66, and −22.92°C on each date post-collection. Paired comparisons of female/male SCPs on each date post-collection did not show significant differences over time. The overall mean SCP of D. mendotae (−23.05°C) is substantially lower than values of −5.3°C and −5.7°C published for adults and larvae of Belgica antarctica Jacobs 1900 collected at Palmer Station (Antarctica) and −14.2°C for larvae of Paraclunio alaskensis Coquillett 1900 collected at Vancouver Island, British Columbia. In addition, the SCP of this species appears to be lower than that of other winter-active insect species reported in the literature. Although no adults survived after the SCP was recorded, further studies are necessary to determine if D. mendotae is a freeze-intolerant insect. Nevertheless, our results suggest that a low SCP could be used as a mechanism to facilitate emergence and adult activity of this species during winter conditions.

Temporal and Taxonomic Patterns of Mouthpart Deformities in Larval Midges (Diptera: Chironomidae) in Relation to Sediment Chemistry

Abstract Entire benthic communities of larval chironomids were sampled in the spring and fall of 1987 from the trace metals-impacted Empire Lake reservoir system, Cherokee County, Kansas. The frequency and severity of mouthpart deformities were calculated for each sample date at the subfamily level and analyzed for correlation with zinc, cadmium and lead concentrations in sediments of the lake. None of the trace metals was significantly predictive of mouthpart deformation, nor was location within the watershed. However, significant taxonomic and temporal patterns in deformation were observed independent of individual trace metals and sampling location. Larval mouthparts were approximately five times as likely to be deformed and three times as severely deformed in the subfamily Chironominae relative to larvae of the subfamily Tanypodinae (frequency = 14.9% vs. 3.1%; Mouthpart Deformity Score, MDS = 30.2 vs. 9.9) (p < 0.01). Similarly and regardless of taxon, the mouthparts of midge larvae present in the sediments for the greatest duration (i.e., overwintering generations) were more frequently (10.7% vs 2.4%) and severely (MDS = 22.2 vs. 1.8) deformed than summer populations (p < 0.01). These levels of frequency and severity are far above those found in unimpacted habitats elsewhere indicating that while individual metal concentrations were not predictive of either the frequency or severity of deformities, clearly the Empire Lake watershed is impacted by some toxicant. Furthermore, the differential temporal and taxonomic responses suggest that both the frequency and severity of mouthpart deformities at the subfamily level can be successful bioindictor tools and more work needs to be done to elucidate their value.

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.

Habitat and sediment preferences ofAxarus festivus larvae

During fall draw-down of a reservoir in northeast Kansas it was observed that larvae ofAxarus festivus were restricted to highly weathered Pennsylvanian Shale outcrops and surrounding coarse sediments with high-clay content derived from erosion of the shale outcroppings. Larvae constructed burrows into the outcrops and eroded coarse sediments, which they used to filter feed by setting up currents through the burrows. Burrows were widely distributed over the outcrops, with average densities ranging from 372–2,351 burrows m−2. However, closer inspection revealed that burrows were more common at apices of individual shale strata, where weathering of the outcrop was most advanced. Here burrows were more uniformly distributed and densities ranged to 4,166 burrows m−2. 73% of burrows contained larvae. Burrows were generally U-shaped, and averaged 1.8 mm in diameter and 42 mm in total length. Laboratory experiments revealed that 4th instar larvae removed from burrows could construct new burrows in weathered shale, but preferentially used old empty burrows if available. When given choices among alternative sediment combinations of sandvs. finely-ground shale, sandvs. coarsely-ground shale, and finely-ground shalevs. coarsely-ground shale, larvae exhibited statistically significant preferences for the finely-ground shales (P<0.001), coarsely-ground shales (P<0.001), and coarsely-ground shales (P<0.01), respectively. It is concluded that larvae (1) actively select shale or high-clay content sediments, (2) can differentiate among sediments with differing physical properties and (3) exhibit behavioral choices for sediment types that guide them toward shale outcrops.