New mitogenomes from the genus Cricotopus (Diptera: Chironomidae, Orthocladiinae): Characterization and phylogenetic implications.

Cricotopus is a large and diverse genus of non-biting midges composed of several subgenera. Complete mitogenome sequences are available for very few Cricotopus species. The subgenus Pseudocricotopus unites species with unusual morphological structures in adult male and pupal stages, however, molecular methods are needed to verify the placement of this subgenus within Cricotopus. We obtained mitogenomes of C. (Pseudocricotopus) cf. montanus and nine other Cricotopus species for phylogenetic analysis, coupled with two Rheocricotopus species and one Synorthocladius species as outgroups. The structure of the mitogenome was similar among these Cricotopus species, exhibiting A+T bias and retaining ancestral gene order. Mutation rate, estimated as Ka/Ks, varied among genes, and was highest for ATP8 and lowest for COI. The phylogenetic relationships among species of Cricotopus, Rheocricotopus and Synorthocladius was reconstructed using Bayesian inference and maximum likelihood estimation. The phylogenetic trees confirmed placement of subgenus Pseudocricotopus, represented by Cricotopus cf. montanus, within Cricotopus. Our study increases the library of chironomid mitogenomes and provides insight into the properties of their constituent genes.

Mimes of the past: Eocene midges of the tribe Pseudochironomini (Chironomidae, Diptera) reveal their peculiarities.

This is the first study focused on Eocene dipterans of the tribe Pseudochironomini (subfamily Chironominae, family Chironomidae), based on unique materials from Baltic amber. Two new genera and three new species: Eomicromimus gen. nov. with Eomicromimus polliciformis sp. nov. and Eomicromimus serpens sp. nov., and Eoriethia gen. nov. with Eoriethia ursipes sp. nov. are presented. The systematic position of the new taxa is discussed, and an amended key to the identification of adult males of extinct and extant Pseudochironomini genera is provided. The presented analysis of the morphology of the tribe's fossil members allowed us to verify the concepts regarding the origin/homology of male diagnostic structures crucial in defining new taxa, their phylogeny, and to consolidate the terminology used in chironomid research. A new habitual name for Chironomidae, "mime midges", is also proposed.

A new desiccation-resistant midge from ephemeral rock pools in South Africa, Polypedilum (Pentapedilum) cranstoni sp. nov. (Diptera: Chironomidae).

One newly described species of Chironomidae, Polypedilum (Pentapedilum) cranstoni sp. nov., was discovered in ephemeral rock pools from the Maloti-Drakensberg mountains in South Africa. Desiccation-resistant larvae were obtained from bottom sediments of rock pools that had been dry for the previous several months. After rehydration, ex situ adults emerged and were collected. The morphology and diagnostic characters of the new species (male and female adults) are described here together with an analysis based on their COI gene sequence.

A new species, Cricotopus cataractaenostocicola, living in a cyanobacterial colony on vertical rocky substrates with trickling water film in Japan (Diptera: Chironomidae).

Trickling water on nearly vertical rocky substrates is a common feature of mountainous regions of Japan. The thin water film is inhabited by discoid colonies of the cyanobacteria Nostoc. This species resembles the North American Nostoc parmelioides Ktzing, which forms ear-like colonies in stream beds and is inhabited by symbiotic chironomid larvae. The Nostoc colony in Japan was inhabited by a chironomid larva inside a ring-shaped burrow in the colony. Morphological analyses suggested that these individuals belong to a new species closely related to Cricotopus spp. symbiotic with Nostoc parmelioides. Here, we described the chironomid species Cricotopus cataractaenostocicola sp. nov. The species was distinguished from other congeneric species mainly by the morphology of male hypopygia. It has an anal point and long setae on the outside of the gonocoxite, and does not have setae near the apex of the inner lobe in the gonocoxite. Almost all the Nostoc colonies contained one large larva or pupa. The outer layer of the chironomid-symbiotic Nostoc colony had an elastic hardness. The 3D computer tomography (3DCT) scan showed a connected network of internal passages that are sufficiently wide to be traversed by the larvae, suggesting that cavities are present for the larvae to pass through. Future studies should investigate the formation of cavities and their purpose. As pioneers in the observation of living organisms using 3DCT, we provided the CT data to the Natural History Museum in Vienna.

Chironomids are commensals of the larvae and pupae of Blephariceridae and Simuliidae from the North Caucasus (Diptera: Chironomidae: Orthocladiinae).

Illustrated morphological descriptions of chironomid larvae from subfamily Orthocladiinae Cardiocladius sp. 1, which as commensals live between ventral suckers of Blephariceridae larvae, as well as larvae and pupae of Eukiefferiella claripennis group inhabited of Simuliidae pupal cocoons, are given. DNA barcodes of these chironomid species and sequences of their hosts, three species of Liponeura Loew (Blephariceridae) and one species of Simulium aff. variegatum (Simuliidae), are provided.

External morphology of larva and polytene chromosomes of Clunio marinus Haliday, 1855 (Diptera, Chironomidae, Orthocladiinae) from two localities of the Atlantic coast.

The larva of Clunio marinus Haliday is described based on field and reared material, collected along the coast of Vigo (Spain) and Helgoland (Germany). C. marinus can be easily distinguished from other known European Clunio species on the basis of some species-specific features found in fourth instar larvae. Comparison with related known Clunio species from Europe with comments on their larval morphology are given. The characteristics of the polytene chromosomes of C.marinus from Vigo are presented. The comparative external morphological analysis of the larvae from the two localities shows a certain differentiation at the external morphological level. The reasons for this differentiation are discussed.

Molecular phylogeny of Japanese marine Tanytarsini chironomids (Chironomidae: Chironominae).

Tanytarsini is a large tribe of Chironomidae with at least 11 recorded marine species grouped in three genera. In this study, we performed a phylogenic analysis using molecular data from 13 Tanytarsini genera, including all Japanese marine species in a large tribe of Chironominae, to estimate their phylogenetic positions and evolutionary history. The phylogenetic reconstruction grouped the marine species in two clades. One clade was composed of five marine Tanytarsus and two marine Pontomyia species within a larger clade of Tanytarsus. Pontomyia is considered to have morphologically specialized and adapted to marine environments by rapid evolution, although it formed a clade with Tanytarsus. The only one species of Tanytarsus, T. pelagicus, clustered as a member of the second clade, which was mainly composed by species of the genus Paratanytarsus. Thus, we redescribe T. pelagicus as Paratanytarsus pelagicus.

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.

Drivers of diversity and altitudinal distribution of chironomids (Diptera: Chironomidae) in the Ecuadorian Andes / Controladores de diversidad y distribución altitudinal de quironómidos (Diptera: Chironomidae) en los Andes ecuatorianos

Introduction: Chironomids (Diptera: Chironomidae) are the most globally diverse and widely distributed aquatic insects. Despite their prevalence in lotic systems, little is known about the ecology and diversity of tropical species relative to other aquatic insect taxa, particularly at the immature stages. Objective: Characterize chironomid diversity across an elevational gradient in Southwestern Ecuador and water quality parameters associated with their composition. Methods: Samples were collected using a Surber net in forty rivers within four watersheds in the Ecuadorian Andes comprised of montane and dry lowland forest and spanning an elevational gradient of 3 120 m.a.s.l. Various physic chemical variables were measured including oxygen, conductivity, total dissolved solids, temperature, and pH. Results: Generally, environmental variables were strongly correlated with the composition of chironomid communities. Variation in the chriomid communities was most strongly associated with oxygen, conductivity and pH. The presence of Parametriocnemus, Cricotopus f4, Cricotopus sp3., Cricotopus (Isocladius), Oliveiriella, Onconeura, Alotanypus and Pentaneura was associated with lower temperatures, high dissolved oxygen and low conductivity while assemblages of Cricotopus sp., Rheotanytarsus, Tanytarsus, and Chironomus were associated with high conductivity and low concentrations of dissolved oxygen. The RELATE analysis showed that local environmental characteristics are determine the composition of the chironomid community. Conclusions: Similarity among local environmental factors was strongly correlated to similarity among Chironomidae assemblages, especially with variables such as oxygen concentration, pH and conductivity, whose variables are highly correlated to land use and dominant vegetation in the watersheds sampled.

Introducción: Los quironómidos (Diptera: Chironomidae) son los insectos acuáticos de mayor diversidad y distribución mundial. A pesar de su prevalencia en los sistemas lóticos, se sabe poco acerca de su ecología y diversidad, especialmente de especies tropicales en relación con otros taxones de insectos acuáticos, particularmente en etapas inmaduras. Objetivo: Caracterizar la diversidad de quironómidos a través de un gradiente altitudinal en el suroeste de Ecuador, además de identificar los parámetros fisicoquímicos asociados con su composición. Métodos: Las muestras se recolectaron utilizando una red Surber en cuarenta ríos dentro de cuatro cuencas hidrográficas en los Andes Sur del Ecuador, en ecosistemas de bosques montanos y secos de tierras bajas abarcando un gradiente altitudinal de 3 120 m.s.n.m. Se midieron las variables fisicoquímicas: oxígeno, conductividad, sólidos disueltos totales, temperatura y pH. Resultados: En general, las variables ambientales se correlacionaron fuertemente con la composición de las comunidades de quironómidos. La variación en la comunidad de quironómidos se asoció fuertemente con el oxígeno, la conductividad y el pH. La presencia de los géneros Parametriocnemus, Cricotopus f4, Cricotopus sp3, Cricotopus (Isocladius), Oliveiriella, Onconeura, Alotanypus y Pentaneura se asoció a temperaturas bajas, alto oxígeno disuelto y baja conductividad, mientras que Cricotopus sp., Rheotanytarsus, Tanytarsus y Chironomus se asociaron con alta conductividad y bajas concentraciones de oxígeno disuelto. El análisis RELATE mostró que las características ambientales locales determinan la composición de la comunidad de quironómidos. Conclusiones: La similitud entre los factores ambientales locales se correlacionó fuertemente con la similitud entre los conjuntos de Chironomidae, especialmente con variables como la concentración de oxígeno, el pH y la conductividad, cuyas variables están altamente correlacionadas con el uso de la tierra y la vegetación dominante en las cuencas hidrográficas muestreadas.

Histological description of immature Chironomus columbiensis (Diptera: Chironomidae): A potential contribution to environmental monitoring.

Chironomids have been widely used in environmental monitoring and toxicity assays. Assessment criteria for chironomids range from the molecular-biochemical level to the population level. However, the use of markers to evaluate cellular and anatomical changes in organs and systems of individuals under contaminant exposure is still incipient. In this study, we conducted a histological description of the main systems and organs of immature Chironomus columbiensis. We used fourth instar larvae, obtained from a standardized culture, and confirmed this state through morphological and molecular methods. Larvae were fixed in Duboscq solution for insects during 48 hr, dehydrated in increasing dilutions of ethanol, and embedded and mounted in historesin to obtain 3 µm sections. The digestive, nervous, excretory, and integumentary systems and the fat body and testicles were analyzed through longitudinal and transversal sections, stained with hematoxylin-eosin (HE), and further photographed and described through light microscopy. This is the first description of internal morphology performed for C. columbiensis and can help in future histopathological analysis, because through bioaccumulation some of these organs are contaminant targets. It can even be a great taxonomic tool, since the characteristics of the histological pattern of C. columbiensis presented differences compared to other descriptions made in chironomids.

Incidence of deformities and variation in shape of mentum and wing of Chironomus columbiensis (Diptera, Chironomidae) as tools to assess aquatic contamination.

Constantly, aquatic ecosystems are under pressure by complex mixtures of contaminants whose effects are not always easy to evaluate. Due to this, organisms are sought in which early warning signs may be detected upon the presence of potentially toxic xenobiotic substances. Thereby, the study evaluated the incidence of deformities and other morphometric variations in the mentum and wing of Chironomus columbiensis exposed to water from some of the Colombian Andes affected by mining, agriculture, and cattle raising. Populations of C. columbiensis were subjected throughout their life cycle (24 days) for two generations (F1 and F2). Five treatments were carried out in controlled laboratory conditions (water from the site without impact, site of mining mercury, mining mercury + cyanide, cattle raising, and agriculture) and the respective control (reconstituted water). Thereafter, the percentage of deformities in the mentum was calculated, and for the morphometric analysis 29 landmarks were digitized for the mentum and 12 for the wing. As a result, four types of deformities were registered in the C. columbiensis mentum, like absence of teeth, increased number of teeth, fusion and space between teeth, none of them detected in the individuals from the control. Additionally, the highest incidence of deformity in F1 occurred in the treatment of mining mercury, while for F2 this took place in the treatments of mining mercury + cyanide, cattle raising and agriculture. Differences were also found with respect to the morphometric variations of the mentum and wing of C. columbiensis among the control and the treatments with water from the creeks intervened. The treatments of mining mercury + cyanide and agriculture had the highest morphological variation in the mentum and wing of C. columbiensis. The results suggest that the anthropogenic impacts evaluated generate alterations in the oral apparatus of the larval state of C. columbiensis and in the adult state provoke alterations in the wing shape (increased width and reduced basal area). These deformities may be related to multiple stress factors, among them the xenobiotics metabolized by the organisms under conditions of environmental contamination.

Body Length Determines the Diet and Niche Specialization of Non-Biting Midge Predator (Tanypodinae) Larvae in Shallow Reservoirs.

The functional traits of species respond to environmental gradient changes, which, in turn, are responsible for the niche specialization of species. We analyzed the niche specialization of several Tanypodinae taxa (predatory non-biting midge, 4th instar, n = 693) along the depth zones of the water in six shallow tropical reservoirs. We measured the body length and diet composition of seven Tanypodinae larvae genus. Community-weighted mean (CWM) traits index was utilized to calculate the niche distribution of body length and diet composition. We analyzed the niche distribution of predator larvae, through a simple linear analysis of CWM index and the depth of the water, and by establishing correlations between body length and diet composition. In our study, it was found that the consumption of oligochaete (b = 0.30, SE ± 0.04, t = 7.02, p = 0.0001, R2 = 0.45) and the body length (b = 0.64, SE ± 0.11, t = 5.44, p = 0.0001, R2 = 0.33) increased in deeper zones. We observed a strong and positive relationship between oligochaete consumption and a longer body (r = 0.91, p = 0.0001). We inferred that changes in habitat characteristics, from littoral to deeper zones of the reservoirs, are expected to have influenced the selection of larvae traits predators. We concluded that body length determines the diet consumption and accurately reflects the niche distribution of Tanypodinae assemblages. The functional trait approach proved to be an efficient tool for the analysis of the ecological processes that determine the structure of a non-biting midge predator assemblage.

Characterization of cadmium and calcium fluxes along the gut, malpighian tubules, and anal papillae of the dipteran Chironomus riparius.

Chironomids are often one of the dominant organisms in significantly polluted freshwater. Many invertebrate studies have characterized whole-organism mechanisms of toxicity, for example, assessing cadmium (Cd) uptake via calcium (Ca) channels. However, with the use of the scanning ion-selective electrode technique and an innovative Cd-selective microelectrode, we analyze this relationship at the organ level using a realistic concentration of Cd and Ca in the hemolymph (blood). Generally, Cd fluxes follow the same directional pattern as Ca, although Ca fluxes are approximately 5 times higher than those of Cd. These results correlate well with previous studies indicating that chironomids have a higher affinity for Ca over Cd, which affords them tolerance to Cd toxicity. When saline Ca concentration was increased to 10 times physiological levels, Cd fluxes from the gut lumen into the cells of the midgut regions were reduced by 50 to 80%. Transport of Cd from hemolymph to tissue for the posterior midgut, Malpighian tubule, and proximal ceca was also reduced by approximately 50%. The present results indicate that Cd fluxes into or across the gut and Malpighian tubules are reduced by high Ca, suggesting that Cd may be transported in some cells by similar mechanisms. However, Cd was actively excreted at the anal papillae after a 48-h waterborne exposure to Cd, but this process was independent of Ca and instead may involve a P-glycoprotein-related pump to detoxify Cd. Environ Toxicol Chem 2018;37:2542-2549. © 2018 SETAC.

Mouthpart deformities in Chironomidae (Diptera) as bioindicators of heavy metals pollution in Shiroro Lake, Niger State, Nigeria.

In this study, mouthpart deformities in Chironomid larvae (Diptera) were investigated in relation to sediment contamination in the Shiroro Lake in Nigeria. Metals and chironomids were sampled monthly at three stations (A-C) between August 2013 and January 2014. Across the stations, zinc ranged (3.9-75mg/g), manganese (1.29-1.65mg/g), lead (0.00-0.10mg/g), iron (101-168mg/g) and copper (0.13-0.17mg/g). The metal ions did not differ significantly (P > 0.05) between the sampling stations. However, zinc and iron ions were significantly different between the sampling seasons (P < 0.05). Thirteen chironomid species were recorded, with Chironomus sp., Polypedilum sp. and Ablabesmyia sp. dominating the assemblage structure. Mouthpart deformities were significantly higher at Station A compared with Station C, and seasonally significantly higher during dry season compared with wet season. Elevated incidences of deformity were recorded in Chironomus spp larvae as compared to other genera therefore for further studies in this region assessments should be based solely on Chironomus species and ignoring the rest. Strategies need to be developed to reduce the contaminations and the biological effects.

The Cricotopus (Oliveiriella) (Diptera: Chironomidae) of the High Altitude Andean Streams, with Description of a New Species, C. (O.) rieradevallae.

The genus Oliveiriella (Chironomidae, Orthocladiinae) was erected by Wiedenbrug & Fittkau (1997). The adults have characteristic black spots on their wings and other characteristics similar to the genus Cricotopus. Pupal skins are very characteristic with strong short spines in the anal lobe instead of setae, while larvae are distinguishable by the long anal papillae and the intense blue color of their body. However, Andersen et al (2013) consider Oliveiriella as a subgenera of Cricotopus. In this paper, using the sequences of the cox1 gene, we conclude that Oliveiriella should be considered a subgenus within Cricotopus, confirming its status in Andersen et al (2013). Furthermore, we describe Cricotopus (Oliveiriella) rieradevallae Prat & Paggi sp. n. from the Saltana river (Ecuador). The adult males, females, and preimaginal stages of the two species of subgenus Oliveiriella known from South America Cricotopus (O.) almeidai n. comb. from Peru, Brazil, and Argentina and Cricotopus (O.) sanjavieri n. comb. from Argentina are compared with those of Cricotopus (O.) rieradevallae sp. n. from Ecuador. The differences allow the distinction of the three species. The cox1 gene reveals that at least three different undescribed species of the same subgenus are present in the high-altitude tropical Andes. The morphology of the available pupae and pupal exuviae reveals the presence of several morphotypes that are candidates to be described as new species. A key used to distinguish these pupal morphotypes is provided, including the three described species. Additionally, the distribution of the subgenus is discussed.

Thermal survival limits of young and mature larvae of a cold stenothermal chironomid from the Alps (Diamesinae: Pseudodiamesa branickii [Nowicki, 1873]).

The threats posed by climate change make it important to expand knowledge concerning cold and heat tolerance in stenothermal species from habitats potentially threatened by temperature changes. Thermal limits and basal metabolism variations were investigated in Pseudodiamesa branickii (Diptera: Chironomidae) under thermal stress between -20 and 37 °C. Supercooling point (SCP), lower (LLTs) and upper lethal temperatures (ULTs), and oxygen consumption rate were measured in overwintering young (1st and 2nd instar) and mature (3rd and 4th instar) larvae from an Alpine glacier-fed stream. Both young and mature larvae were freezing tolerant (SCPs = -7.1 °C and -6.4 °C, respectively; LLT100 -20 °C) and thermotolerant (ULT50 = 31.7 ± 0.4, 32.5 ± 0.3, respectively). However, ontogenetic differences in acute tolerance were observed. The LLT50 calculated for the young larvae (= -7.4 °C) was almost equal to their SCP (= -7.1 °C) and the overlapping of the proportion of mortality curve with the CPIF curve highlighted that the young larvae are borderline between freezing tolerance and freezing avoidance. Furthermore, a lower ULT100 in the young larvae (of ca. 1 °C), suggests that they are less thermotolerant than mature larvae. Finally, young larvae exhibit a higher oxygen consumption rate (mgO2 /gAFDM/h) at any temperature tested and are overall less resistant to oxygen depletion compared to mature larvae at ≥10 °C. These findings suggest that mature larvae enter into a dormant state by lowering their basal metabolism until environmental conditions improve in order to save energy for life cycle completion during stressful conditions.

A new species of Dicrotendipes (Diptera: Chironomidae) from Florida.

A new species of Dicrotendipes is described in all life stages from Florida. Adults of this new species are nearly identical to D. modestus (Say); pupae are similar to D. modestus, D. neomodestus (Malloch) and D. tritomus (Kieffer); while the larvae are unique and were keyed by Epler (1992, 1995, 2001) as Dicrotendipes sp. A. The taxonomic status of D. modestus and D. pulsus (Walker) is discussed.

Revision of early taxa of Australian gall midges (Diptera: Cecidomyiidae).

Australian Cecidomyiidae described by Schiner (1868), Skuse (1888, 1890), Koebele (1893), Felt (1915), Edwards (1916) and Rübsaamen (1916), totalling 111 species and three subgenera, are revised. Chastomera Skuse, 1888 is confirmed to be a junior synonym of Haplusia Karsch, 1878 and Gonioclema Skuse, 1888 and Necrophlebia Skuse, 1888 are declared nomina dubia. Twenty-two species are placed to genus, an additional four species are placed to supertribe or subfamily, all of them redescribed. The remaining species are declared junior synonyms or nomina dubia. Diadiplosis koebelei (Koebele, 1893) is a new junior synonym of Diadiplosis plumbea (Skuse, 1888). Dasineura tomentosa Dorchin, 2011 is a new junior synonym of Dasineura frauenfeldi (Schiner, 1868). Sphenolasioptera Kolesik & Gagné gen. nov. (Cecidomyiinae: Lasiopterini) is erected to contain Sphenolasioptera vastatrix (Skuse, 1888) n. comb. The following genera are recorded from Australia for the first time: Ledomyia Kieffer (Cecidomyiinae: Ledomyiini), represented by L. vitulans (Skuse), n. comb.; Bremia Rondani (Cecidomyiinae: Aphidoletini), represented by B. actiosa (Skuse) n. comb. and B. oreas (Skuse) n. comb.; Divellepidosis Fedotova & Sidorenko (Porricondylinae: Porricondylini), represented by D. pallidina (Skuse) n. comb. and D. indubitata (Skuse) n. comb. Additions are made to the key to genera of Cecidomyiinae of Australia and Papua New Guinea (Kolesik 2014) to accomodate Bremia, Ledomyia and Sphenolasioptera.

The taxonomic implication of frontal tubercles in Polypedilum subgenera diagnoses, with re-description of Polypedilum isigabeceum Sasa & Suzuki (Diptera, Chironomidae).

Polypedilum isigabeceum Sasa et Suzuki, 2000 was described as belonging to subgenus Polypedilum s. str. However, if we accept the conclusion of Sæther et al. (2010), the species might be placed into Kribionympha with P. unagiquartum Sasa, 1985 because of the presence of distinct frontal tubercles in the adult males. However, other taxonomic characters do not support their treatment. P. isigabeceum is re-described and reconfirmed to be assigned to the subgenus Polypedilum s. str. The taxonomic meaning of frontal tubercles is discussed for defining the subgeneric rankings within genus Polypedilum.

The species of the genus Diamesa (Diptera, Chironomidae) known to occur in Italian Alps and Apennines.

Some rare species from Italian Alps, belonging to the genus Diamesa Meigen, 1835 (Diptera, Chironomidae) are here redescribed as adult males, because only old, incomplete descriptions are available for these taxa. Terminology of male genitalia is reviewed, diagnostic features are illustrated in detail, and notes on biology and geographical distribution of the examined species are provided. An identification key to the known adult males is presented.