Longevities of Adult Chironomidae (Diptera) from Two Streams in Iceland

Mean annual air temperatures are predicted to increase by several degrees in the Arctic. This increase in temperature will likely impact organisms adapted to current conditions. Studies of longevities of winter-active Chironomidae from cold, groundwater-fed streams in Minnesota demonstrate that winter-emerging species are long-lived as adults when incubated at cold or sub-freezing air temperatures post emergence. It is unknown if this holds for species emerging in sub-arctic latitudes during warm months, or if warm air temperatures affect the adults of species emerging from cold and geothermally heated streams. The goal of this study was to determine the effects of exposure to air temperatures predicted by climate change models on the longevities of Chironomidae emerging from both cold and geothermally heated larval environments. Chironomidae were trapped at emergence from two groundwater-fed streams with contrasting (warm and cold) thermal regimes at the Hengladalir valleys in the Hengill alpine geothermal area in southwestern Iceland over 4 days in July 2018. Adults (N=102) were randomly divided into two treatments and incubated at either 20°C or 6°C for 28-32 days to determine influence of source stream and incubation temperature on adult longevity. These temperatures were selected to simulate current and predicted water and air temperatures that adult chironomids are likely to be exposed to with climate change. Adults incubated at 6°C survived longer than adults incubated at 20°C irrespective of source stream. All adults incubated at 20°C died within 1-5 days post-emergence. Longevities of taxa incubated at 6°C ranged from 13 to more than 32 days. Species of Diamesa exhibited the greatest longevities, with 41.7% surviving more than 28-32 days post-emergence at 6°C. We were unable to determine maximum longevity for Diamesa within the 6°C treatment because surviving adults had to be sacrificed at the termination of the experiment on day 32. However, the minimum longevity we report is similar to longevities determined for other Diamesa species and indicates that Diamesa species in Iceland are also long-lived under cold air temperatures. We suggest there may be a difference in longevity between sex, with females living longer than males at cold temperatures. By contrast, we found that both sexes of Diamesa and all other chironomid taxa that we tested are susceptible to warm air temperatures regardless of stream of origin. Therefore, warming climatic temperatures could potentially lead to shortened adult lifespans for these sub-arctic taxa.

Short comment on Chironomidae (Insecta: Diptera) from Brazil’s Federal District

There is much left to learn about the diversity of Chironomidae in Brazil. To help to resolve this problem, a preliminary study of the Chironomidae present in a stream located in center of Brazil was proposed. The aim of this research was to provide a first record of the Chironomidae assemblage at Sarandi stream, in the Brazilian Cerrado. Samples were taken using a handheld D-net from the stream in October 2009. The samples were transported to the laboratory where the material was processed and the Chironomidae specimens were slide mounted, counted and identified to genera. Ninety individuals belonging to 15 genera were found, Chironomini was the richest tribe, with seven genera, while Tanytarsini showed the highest abundance of individuals (55.6%). Overall, Rheotanytarsus (20%), Tanytarsus ortoni-group (16.7%) and Lopescladius (14.4%) were the most abundant genera.

Chironomus calligraphus Goeldi, 1905 and C. hawaiiensis Grimshaw, 1901 are sibling species

Although Spies et al.’s (2002) thorough analysis of a small sample of the then available specimens of Chironomus calligraphus Goeldi,1905 suggested two distinctly different haplotypes in the mitochondrial COII gene, the corresponding morphological and cytological evidence kept the authors from concluding that there were two species involved. Further obstacles were unusual aspects of the molecular data and the occurrence of both these haplotypes in samples from the Brazilian type locality by Fittkau (1965) from which he had fixed a neotype. This neotype is slide mounted and can no longer yield molecular data. The present author’s analysis of additional material, including the available BARCODE sequences, has confirmed the existence of two forms, perhaps consistent with those found in the COII analysis, and with largely overlapping geographic distributions. One of these forms occurs in Hawaii where it is morphologically indistinguishable from C. hawaiiensis Grimshaw, 1901. It is recommended to apply this name, which takes nomenclatural precedence to the form found in Hawaii, and the name C. calligraphus to the form found to be more common in Fittkau’s type-locality samples.

The 21st International Symposium on Chironomidae

The 21st International Symposium on Chironomidae was originally scheduled for Tsukuba, Japan in July 2021. However, the COVID-19 pandemic is far from ending and Tokyo Summer Olympic Games were postponed to 2021. Many international conferences including the International Congress of Entomology or the Congress of the International Society of Limnology were also reported to next year. The organizing committee wishes to welcome the whole community of chironomid researchers to Tsukuba under safer and the best possible conditions. For this reason, the organizing committee decided to postpone the symposium to summer 2022. As many colleagues agreed, a physical meeting will yield more fruitful exchanges in our field rather than an online symposium. This is also one point that motivated our decision to postpone the 21st International Symposium on Chironomidae to 2022. As soon as the new dates for the Symposium are fixed, we will make a new announcements in the Chironomus Journal, on the Chironomid Home Page and in the Chironomidae list server ([email protected]). We wish you all good health and look forward to welcome all of you in Tsukuba!

Evidence of parthenogenetic populations from the Paratanytarsus laccophilus species group (Diptera: Chironomidae) in the Alaskan Arctic

Parthenogenesis, reproduction without fertilization, is not common in the Chironomidae (Diptera), a family of insects with more than 6,000 described species. Nonetheless, parthenogenetic species and strains have been documented in at least three subfamilies (the Chironominae, Orthocladiinae, and Telmatogoninae), spanning 17 genera and ~30 species. One such species, Paratanytarsus laccophilus Edwards 1929, is known to be parthenogenetic in a small portion of its range in Finland, with most other European populations of this species showing evidence of sexual reproduction. We present evidence of parthenogenetic populations from the Paratanytarsus laccophilus species group in the Nearctic, specifically a High Arctic site near Utqiaġvik (formerly Barrow), Alaska. During May-July of 2015 and 2016, we sampled emerging adult chironomids and pupal exuviae daily to document insect emergence phenologies. Across 15 local populations, all 623 pupal exuviae collected from the P. laccophilus species group were female. Larvae reared from two populations under controlled temperature treatments emerged as female adults (N=37). When isolated, these reared female adults oviposited, and eggs hatched successfully. These progeny were reared for another 12-13 days, reaching second instar larvae when they were preserved at the end of our field season. Taken together, this evidence strongly indicates parthenogenesis from the P. laccophilus species group at this location. This species was not previously documented at Utqiaġvik. Although parthenogenetic, their emergence at this location was highly synchronized. In the harsh environment of arctic Alaska, the fitness rewards of parthenogenesis are likely great. Indeed, chironomid parthenogenesis in the northern hemisphere is most commonly documented from far-northern extremes and in extreme habitats.

First record of Nubensia nubens (Edwards, 1929) (Diptera: Chironomidae) for Bulgaria

Nubensia nubens (Edwards 1929) is reported for the first time in Bulgaria from two lowland rivers, tributaries of the Danube (eastern Europe). Larvae of the species were found incidentally in samples collected for an ichthyological study, in the gut contents of Neogobius melanostomus (Pallas 1814) (Actinopterygii: Gobiidae), and in a benthic sample. The habitat conditions at the corresponding sites differed from those of previous records. Our finding underlines the potential of non-standard supporting methods, such as analyzing fish gut contents for discovering rare species that are hard to record by standard hydrobiological methods.

Description of the adult and immature stages of Clunio ponticus Michailova, 1980 (Diptera, Chironomidae), from the Black Sea, Varna, Bulgaria

The mature and immature stages of Clunio ponticus Michailova, 1980 are diagnosed and described based on associated material recently collected in the marine littoral zone of Varna, St-Konstantin and Helena Resorts, Black Sea (eastern Bulgaria). Male and female adults, pupae and larvae of C. ponticus can be easily distinguished from other known European Clunio species on the basis of some atypical features found in the male and female adults, pupal exuviae and fourth instar larvae. In addition, the biological cycle (reproduction and emergence) of C. ponticus is not synchronized with lunar periodicity (new and full moon) as for some other known Clunio species from Europe, but closely related to the typology of the intertidal zone along the coastline of the Black Sea. This indicates that this species is a local biogeographic representative of the ‘Pontus Region’, which includes the eastern coastline of the Black Sea. Remarks on related known Clunio species from Europe with comments on the ecology and geographical distribution of C. ponticus are given.