Experimental evidence for neonicotinoid driven decline in aquatic emerging insects

There is an ongoing unprecedented loss in insects, both in terms of richness and biomass. The usage of pesticides, especially neonicotinoid insecticides, has been widely suggested to be a contributor to this decline. However, the risks of neonicotinoids to natural insect populations have remained largely unknown due to a lack of field-realistic experiments. Here, we used an outdoor experiment to determine effects of field-realistic concentrations of the commonly applied neonicotinoid thiacloprid on the emergence of naturally assembled aquatic insect populations. Following application, all major orders of emerging aquatic insects (Coleoptera, Diptera, Ephemeroptera, Odonata, and Trichoptera) declined strongly in both abundance and biomass. At the highest concentration (10 µg/L), emergence of most orders was nearly absent. Diversity of the most species-rich family, Chironomidae, decreased by 50% at more commonly observed concentrations (1 µg/L) and was generally reduced to a single species at the highest concentration. Our experimental findings thereby showcase a causal link of neonicotinoids and the ongoing insect decline. Given the urgency of the insect decline, our results highlight the need to reconsider the mass usage of neonicotinoids to preserve freshwater insects as well as the life and services depending on them.

Physiological responses of freshwater insects to salinity: molecular-, cellular- and organ-level studies

ABSTRACT Salinization of freshwater is occurring throughout the world, affecting freshwater biota that inhabit rivers, streams, ponds, marshes and lakes. There are many freshwater insects, and these animals are important for ecosystem health. These insects have evolved physiological mechanisms to maintain their internal salt and water balance based on a freshwater environment that has comparatively little salt. In these habitats, insects must counter the loss of salts and dilution of their internal body fluids by sequestering salts and excreting water. Most of these insects can tolerate salinization of their habitats to a certain level; however, when exposed to salinization they often exhibit markers of stress and impaired development. An understanding of the physiological mechanisms for controlling salt and water balance in freshwater insects, and how these are affected by salinization, is needed to predict the consequences of salinization for freshwater ecosystems. Recent research in this area has addressed the whole-organism response, but the purpose of this Review is to summarize the effects of salinization on the osmoregulatory physiology of freshwater insects at the molecular to organ level. Research of this type is limited, and pursuing such lines of inquiry will improve our understanding of the effects of salinization on freshwater insects and the ecosystems they inhabit.

Absolute Population Estimates by Sampling a Unit of Aquatic Habitat

Methods for quantitative sampling of open marine and freshwaters are described, including fishing nets, plankton nets, pump samplers, the Patalas–Schindler volume sampler, and specialized methods for freshwater insects. Specialist methods for sampling freshwater floating, emergent, and submerged vegetation are described. Methods for quantitatively sampling the bottom fauna in the various substrates found in streams, rivers, lakes, and the sea bed are reviewed. The use of various poisons and anaesthetics for sampling fish are described.

Trichoptera in the Faroe Islands

In this paper the literature on Trichoptera in the Faroe Islands is reviewed and occurrence of species in recent research on freshwater insects is added. The first record of Trichoptera dates from 1782, without any recognisable species. Today, 20 species are known from the islands, but their frequency of occurrence differs between the Northern Islands and the other islands. A difference in topography of the island groups has previously been hypothesized as an explanation, and data presented in this paper support this hypothesis.