Chaoborus flavicans Meigen (Diptera, Chaoboridae) is a complex of lake and pond dwelling species: a revision

Chaoborus flavicans (Meigen) is a widespread and much studied lacustrine phantom midge. As larvae, these insects are important aquatic predators. Based on the available type material, morphology of immature stages and adults, their aquatic habitat, and DNA barcodes, C. flavicans is shown to be a composite of at least four species, with three of these named here. Chaoborus flavicans is primarily a lake-dwelling species with a Holarctic range. Chaoborus albipes (Johannsen, 1903 stat. rev.) and C. posio Salmela sp. n. are pond-dwelling Holarctic and north European species, respectively. The position of the larval subordinate mandibular tooth at the vertex of the second and fourth teeth is a synapomorphy of the Chaoborus flavicans species complex. We present an identification key to fourth instar larvae, pupae, and adult males. We also designate the lectotype and paralectotypes of Sayomyia rotundifolia Felt, 1904 (syn. nov. of C. albipes). We hypothesize that a fourth species of the species complex is present in Japan. Our revision indicates that Holarctic shallow ponds contain a hidden diversity of predators (C. albipes and C. posio sp. n.).

Toxic Effects of Fine Plant Powder Impregnated With Avermectins on Mosquito Larvae and Nontarget Aquatic Invertebrates

The toxic effects of an avermectin-impregnated fine plant powder (AIFP) against larval Aedes aegypti L. (Diptera: Culicidae), Culex modestus Ficalbi (Diptera: Culicidae), and Anopheles messeae Falleroni (Diptera: Culicidae), as well as selected nontarget aquatic invertebrates, were studied under laboratory conditions. The possibility of trophic transfer of avermectins (AVMs) through the food chain and their toxic effects on predaceous species fed AIFP-treated mosquito larvae was also evaluated. Among mosquitoes, Anopheles messeae were the most sensitive to AIFP, while Cx. modestus exhibited the least sensitivity to this formulation. Among nontarget aquatic invertebrates, the greatest toxicity of AIFP was observed for benthic species (larval Chironomus sp. Meigen (Diptera: Chironomidae), whereas predators (dragonflies, water beetles, and water bugs) exhibited the lowest AIFP sensitivity. AIFP sensitivity of the clam shrimp Lynceus brachyurus O. F. Muller (Diplostraca: Lynceidae), the phantom midge Chaoborus crystallinus De Geer (Diptera: Chaoboridae), and the mayfly Caenis robusta Eaton (Ephemeroptera: Caenidae) was intermediate and similar to the sensitivity of the mosquito Cx. modestus. However, these nontarget species were more resistant than An. messeae and Ae. aegypti. Solid-phase extraction of mosquito larvae treated with AIFP and subsequent high-performance liquid chromatography (HPLC) analysis of the extracts revealed an AVM concentration of up to 2.1 ± 0.3 μg/g. Feeding the creeping water bug Ilyocoris cimicoides L. (Hemiptera: Naucoridae) on the AIFP-treated mosquito larvae resulted in 51% mortality of the predaceous species. But no toxicity was observed for Aeshna mixta Latreille (Odonata: Aeshnidae) dragonfly larvae fed those mosquito larvae. The results of this work showed that this AVM formulation can be effective against mosquito larvae.

Temporal Variations of Water Quality Parameters, Phytoplankton, And Invertebrates In Environmental Change Hotspots: A Case of Lake Wamala, Uganda

Lake Wamala (Uganda) is a small shallow lake (maximum mean depth = 4.5m) that has periodically undergonefluctuations in depth and area because of changes in rainfall, temperature and wind speed. No study, however,has been done to assess how these changes, in addition to catchment degradation, which are likely to intensify in future, have affected aquatic productivity processes. Data on Secchi depth (SD), turbidity, conductivity, dissolved oxygen (DO), total phosphorous (TP), soluble reactive phosphorus (SRP), soluble reactive silicon (SRSi), ammonia (NH4-N), nitrite nitrogen (NO2-N), nitrate nitrogen (NO3-N), Chlorophyl a, composition and abundance of algae, and invertebrates were compared between periods 1998-2000 and 2011-2013. Results showed a twofold increase in conductivity and TP, a threefold increase in SRSi, chlorophyll a > 25 ?g l-1, and persistence by low water transparency (SD < 0.7 m). In consequence, algal biomass increased by >70%, with emergence of new species, especially among the dinoflagellate and euglenophyte groups. Although rotifers, which are known to have capacity to withstand stressful habitat conditions, dominated the zooplankton, their density decreased by >80%. The phantom-midge, chaoborus, and the midge, chironomid, larvae dominated macro-invertebrate, but did not show clear trends between the two periods.