Strong genetic differentiation and postglacial origin of populations in the marine midge Clunio marinus (Chironomidae,Diptera)

The marine midge Clunio marinus (Chironomidae, Diptera) is characterized by a one‐dimensional distribution along the European Atlantic coast, where its lunar and circadian emergence rhythms are genetically adapted to the local tidal regimes, resulting in a series of ‘temporal races’. Clunio marinus is restricted to rocky coasts and thus the temporal races occur in different rocky patches. We studied 10 populations of Clunio marinus from five different regions, spanning the major rocky mainland coasts from Spain to Norway, using amplified fragment length polymorphisms (AFLP), microsatellites and mitochondrial cytochrome oxidase I (COI) sequences. Star‐like patterns of COI haplotypes within regions indicate postglacial colonization. A high degree of shared polymorphisms in AFLP markers suggests colonization from a single source, implying postglacial evolution of timing adaptations in relation to the local tidal regime. In contrast, no COI haplotypes are shared among regions. We hypothesize that different levels of differentiation of nuclear vs. mitochondrial markers in the source region were carried forward during postglacial expansion. Despite the recent origin of populations, all markers reveal distinct genetic differentiation between rocky coasts on a scale of 650–1150 km. Differentiation between rocky coasts is not correlated to timing adaptations, suggesting that geographic isolation is prevalent between rocky coasts and that this facilitated the evolution of local timing adaptations. At the same time there is little genetic differentiation within rocky coasts on a scale of 2–6 km; leaving open the possibility that within rocky coasts with large variation in tidal regimes, temporal adaptations evolved in the face of gene flow.     

Isolation of 10 polymorphic microsatellite loci in the marine midge Clunio marinus (Chironomidae, Diptera) and their efficient characterization by heteroduplex analysis

Ten polymorphic microsatellite loci were cloned and characterized for the marine midge Clunio marinus (Chironomidae, Diptera). The number of alleles ranged from three to 31, the observed heterozygosity ranged from 0.06 to 0.83. During preliminary tests for polymorphisms, we identified subtly differing alleles due to the heteroduplexes they formed on nondenaturing gels. This allowed for the use of unlabelled primers in standard lower resolution PAGE and thus saved time and money in primer testing.     

The flightless marine midge Pontomyia (Diptera: Chironomidae): ecology,distribution, and molecular phylogeny

Pontomyia Edwards, 1926 (Diptera: Chironomidae) is a genus of exclusively marine flightless midges. There are four described species from the Indo‐Pacific, and one undescribed species known only from females, pupal skins, and larvae from the Atlantic/Caribbean. They are poorly known owing to their small size (～1.0 mm), extremely short adult life (< 3 h), and unusual habitat for an insect (coastal lagoons, bays, or rock pools). We reviewed scattered literature on their biology and systematics, presented photomicrographs of the male hypogium, and updated the geographic distribution of each species. We carried out the first molecular study to elucidate relationships among and within three of the species. Results from our four‐gene phylogenetic reconstruction using combined gene tree and species tree approaches showed that Pontomyia natans, Pontomyia oceana, and Pontomyia pacifica are each well‐supported clades, with P. natans as sister to P. oceana + P. pacifica. Genetic distances based on mitochondrial cytochrome oxidase I are extraordinarily large within P. natans and P. pacifica, which suggests that they may be cryptic species complexes. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 162 , 443–456.     

Maritime midge radiations in the Pacific Ocean (Diptera: Chironomidae)

Maritime chironomid midges (Diptera) are diverse, yet these ‘pearls of the ocean’ are little known. Emphasizing Pacific Ocean taxa, we used six genetic markers (18S, 28S, CAD1, CAD4, FolCOI and COI) and fossil calibrations to produce Bayesian time-calibrated phylogenies to date eight independent marine transitions in three subfamilies. Deep nodes involve subfamily Telmatogetoninae (originating mid-Cretaceous, 101–128, 114 Ma), with sister genera Telmatogeton Schiner and Thalassomya Schiner splitting later in the Cretaceous (56–82, 69 Ma). Two transitions in Orthocladiinae involve Clunio Haliday and Pseudosmittia Edwards, dating from the upper Cretaceous, both with Eocene crown groups. In subfamily Chironominae, transitions to marine occur in two tribes. Four transitions occur within the otherwise nonmarine crown groups Kiefferulus Goetghebuer, Dicrotendipes Kieffer, Polypedilum Kieffer and Ainuyusurika Sasa & Shirasaka. Two separate robust clades in tribe Tanytarsini involve: (1) a minor radiation within Paratanytarsus dated to the mid-Eocene around 43 Ma; and (2) an unexpected but fully supported diversification in Pontomyia Edwards plus Yaetanytarsus Sasa dated to around 47 Ma, with separation of Pontomyia from Yaetanytarsus around 40 Ma. Crown Pontomyia, represented by three species, was estimated to have diverged around 19 Ma, whereas the crown radiation of Yaetanytarsus, with 12 sampled species, dates to the mid-Eocene. In a comprehensive global review we concisely document new synonymies and new combinations revealed by the study. The evolutionary timing estimate provides insights into the frequency of marine transitions and diversifications in the Chironomidae in association with dynamic oceanic changes during the Oligocene and Miocene.     

Oogenesis and chromosomal heterozygosity in the thelytokous midge,Lundstroemia parthenogenetica (Diptera,Chironomidae)

The thelytokous triploid midge Lundstroemia parthenogenetica (Diptera: Chironomidae:Chironominae), 3n = 9, is always found to be heterozygous for two inversions and a deletion. Parthenogenesis is maintained by an apomiotic restitutional oogenesis as found in the subfamily Orthocladiinae. This mechanism is compared with other groups exhibiting a restitutional or disordered first division. Possible modes of evolution of the apomictic restitutional system, origin of triploidy in apomictic forms, and chromosomal polymorphisms are discussed.     

Site specific differentiation in metal tolerance in the midge Chironomus riparius (Diptera,Chironomidae)

Metal tolerance in Chironomus riparius (Diptera) populations from contaminated streams was studied by comparing the effects of cadmium, zinc and iron on first generation laboratory reared midges. First instar larvae were exposed for four days, after which surviving larvae were counted and their length measured. Larvae from two highly polluted sites, kept under control conditions, grew substantially slower than those from other populations. All populations showed the same growth responses to increased zinc concentrations, but differences were found in the responses to both cadmium and iron. Since population differentiation was demonstrated in first generation laboratory animals, it is suggested that the differences between populations of C. riparius have a genetic basis.     

Karyotype of the midge Chironomus heterodentatus Konstantinov from the group Obtusidens (Diptera, Chironomidae)

The karyotype of Chironomus heterodentatus, belonging to the obtusidens-group described by Konstantinov from the Volga in 1956, was studied in detail. Combinations of chromosomal arms are AB, CD, EF and G (cytocomplex thummi). The Ch. heterodentatus karyotype cleary differs from those of other members of the obtusidens-group with a species-specific banding pattern in arms A, B, C and D. Chromosomal polymorphism on homo- and heterozygous inversions was found in arms, A, B, D, E and G. 19 inversion banding sequences and their 27 genotypic combinations have been recorded. The shortest arm G is highly polymorphic. Heterozygotes on the Balbiani ring activity were found in arm G along with homo- and heterozygotes on inversions. B-chromosomes with a frequency equal to 2.7-25.0% were recorded in some Volga populations.     

Particulate material and midge larvae (Chironomidae: Diptera) in an upland river

The density of midge larvae (Chironomidae), which dominate the stone-surface fauna (81.3 ± 4.9% of the community by number) in an upland stream in northeast England is regulated by the amount of particulate material available. The amount of material depends on the deposition of suspended particles and on epilithic algal growth. Spates, characteristic of this type of stream, result in scouring and denudation of rock surfaces, preventing the build-up of epilithic material and limiting larval densities by regulating the availability of food and tube-building material. Detritus is the main type of particle in suspension throughout the year (66 ± 6%); detritus and diatoms the chief epilithic kind (65 ± 4 and 29 ± 4% respectively). The probable effects of flow amelioration, resulting from the formation of the proposed Kielder Reservoir are discussed.     

Phenology and life history of Belgica antarctica, an Antarctic midge (Diptera: Chironomidae)

ABSTRACT.

• 1 An account of the life-history with emphasis on phenology and number of instars is presented for Belgica antarctica Jacobs, the southernmost holometabolous insect.
• 2 Contrary to earlier reports, Belgica has four instars, in common with most other chironomids. Mean head capsule lengths varied between different populations but no overlap was found between discrete size classes of successive instars.
• 3 Belgica overwinters in all four instars.
• 4 Relative frequency of different instars from samples taken through the season indicates that a 2-year life-span is the commonest pattern.
• 5 Emergence of adults is relatively synchronous. Belgica exhibits protandry, which may be established at the time of pupation.

     

Archaeochlus Brundin: a midge out of time (Diptera: Chironomidae)

Abstract. Archaeochlus , a plesiomorphic genus of Podonominae (Chironomidae), is revised and two new species (biko from Namibia and brundini from southwestern Australia) described. The systematic status of the genus and the tribe Boreochlini is reassessed. Biogeographic evidence, sustained by a fossil record, dates the genus at least to the Upper Jurassic. The ecology of early Chironomidae is suggested to be eurythermic and hygropetric rather than cold stenothermic in lotic waters.     

Sympatric species,Clunio marinus Hal. and Cl. balticus n. sp. (Dipt., Chironomidae), isolated by differences in diel emergence time

Summary Two populations of Clunio, an intertidal one and a sublittoral one, were found sympatric in the Kviturdvikpollen near Bergen, western Norway. The times of eclosion and the immediately following reproduction were strictly separated in each species by only a few hours' difference. The emergence time of the intertidal population was strictly correlated with the afternoon low water of spring tides; the population resembles the Helgoland (North Sea) population in nearly all its morphological and physiological characteristics. The sublittoral population emerged nearly every day (during the summer) just after sunset, independent of the tides, with only a slight increase in number during the time of the first and last quarters of the moon. The sublittoral population is similar to the populations from the Baltic Sea, especially in its characteristics of emergence control and sinking of the suffused egg masses. Cross-breeding experiments with stocks from both populations resulted in an intermediary emergence time of the first filial generation which was never observed in the field. Therefore, one can conclude that the sympatric populations are perfectly isolated in nature and that they have the well-defined rank of two species. The intertidal population belongs to the well-known Clunio marinus; the sublittoral population together with well-known open-sea populations of the Baltic Sea are classified as a new species, Clunio balticus n. sp.The author owes great thanks to Prof. Dr., D. Neumann for his guidance of this research, which is part of a doctoral thesis, and to the Biological Station of the Universityof Bergen for giving the author, generous opportunities for field research. Financial aid, was granted by the Deutsche Forschungsgemeinschaft     

Ultrastructure of the retrocerebral complex in the adult midge,chironomus riparius MG (Diptera : Chironomidae)

The organisation of the retrocerebral complex of adult Chironomus riparius Mg. (Diptera : Chironomidae) has previously been compared with that of the larva. The primary objective of the present work was to examine the ultrastructure of the components of the complex in neoimaginal male C. riparius to enable their further comparison with similar structures in other dipterans and determine whether this information supports the contention that the midge has a relatively primitive neuroendocrine system.The hypocerebral ganglion has a complex innervation, is composed of non- neurosecretory neurons and glial cells and, with the adjacent aortic wall, is the major neurohaemal site of the complex. The corpora cardiaca are not intimately associated with the ganglion. They are not apparently neurohaemal but are composed of cells containing granules with a bimodal size distribution. The corpora allata are of the pseudolymphoid type and are devoid of extracellular stromal channels. Peritracheal tissue persists into the neoimaginal midge but is apparently inactive and undergoing degeneration.The post-cerebral glands have been included in all previous accounts of the retrocerebral complex in chironomids but the present work confirms the view that they are not endocrine in nature despite their close proximity to the corpora cardiaca. Their ultrastructural appearance suggests that they may be functionally related to pericardial cells in other insects.It is concluded that the retrocerebral complex is indeed rather primitive both in its organisation and in the structure of its components.     

An ultrastructural study of the larval integument of the midge,Chironomus riparius meigen (Diptera: Chironomidae)

Summary The larval integument of the midge, Chironomus riparius Mg., is unusually thin although it conforms with the normal insect pattern. The cuticle of the post-cephalic segments is about 3 m thick and overlies an epidermis which has an irregular basal plasma membrane resulting in spaces occurring between it and the basement membrane. The ventral tubuli have a similar epidermis but the cuticle is somewhat thinner. The anal papillae have the thinnest cuticular covering with a uniquely folded epicuticle of variable thickness, and their epidermis has the characteristics of a transporting epithelium. No evidence of pore canals could be found in the cuticle of any part except the head capsule which has a remarkably smooth epicuticle and a distinct layer which may represent the exocuticle. There are no spaces between the basement membrane and basal plasma membrane of the epidermis in the head. Ultrastructural evidence would suggest that gaseous exchange can occur across most of the post-cephalic integument.The author is indebted to Mrs. L. Rolph and Mr. R.L. Jones for their technical assistance     

The winged Antarctic midge Parochlus steinenii (Gerke) (Diptera: Chironomidae) in the South Shetland Islands

The morphological variation of adult Parochlus steinenii (Gerke) is described from measurements of two populations from the South Shetland Islands. Morphologically, the population from Ardley Island is significantly larger than the population from Livingston Island, and in both populations variation in forefemur length is generally greater than variation in either antennal or wing length. The final instar larva of P. steinenii is described in detail. A consideration of the species' distribution in three geographically isolated areas, as well as of the greater morphological variation in polar as opposed to temperate populations, indicates that a flexible life history strategy in the larval stage may be important for survival in extreme environments.     

The emergence of midges (Diptera: Chironomidae) from a wet gravel-pit

SUMMARY. Emerging adult chironomids were captured from a wet gravel-pit in the Midlands in 1975 and 1976. The emergence period in 1976 was earlier than in 1975 and this change was attributed to the higher temperatures during the early part of 1976. Forty-seven species were identified of which twenty-one were found in both years. However, only eighteen species represented more than 5% of the monthly emergence from any one trap. The timing and location of emergence of the common species is discussed in relation to the physical parameters of substratum, depth of water and vegetation at each trap site. Similarity indices were used to compare samples from each trap site and revealed a progressive change in the chironomid assemblage with depth, caused by a succession of species and a change in the structure of the assemblage with 'equitability' decreasing with increasing depth. The predominant species in 1975 were Cricotopus sylvestris, C. intersectus and Procladius choreus with a number of Chironominae present in both May and June. A trap in the littoral zone caught maximum numbers earlier than traps in open water. In 1976 the above species were still predominant and Tanypus punctipennis and T. vilipennis were also numerous. The Chironominae became proportionally more abundant as the season progressed. The abundance of emerging midges was low compared with other surveys due to the restricted emergence period, imagines being abundant only in June, and also due to the low numbers emerging.     

Colonization and emergence of midges (Chironomidae: Diptera) in slow sand filter beds

Colonization by midges, and temporal changes in their community structure, were examined in slow sand filter beds. The replicated beds allow the development of communities to be traced from a known starting point.The filter beds (rectangular concrete containers filled with water) have a substratum of sand on which a rich coating of organic particles develops during passage of the water through the bed. The containers (ponds) are drained from time to time and the organic layer is then scraped off the sand surface. This occurs on average, once a month. The length of time the ponds were filled with water (bed run) during the present study ranged from 16 to 77 days.In long bed runs small midges with a short aquatic phase (Cricotopus sylvestris, Psectrocladius limbatellus, Tanytarsus fimbriatus) produced adults after 16–20 days; other, larger midges,e.g. Psectrocladius barbimanus and the Tanypodinae required a longer aquatic phase. Of the Tanypodinae, the smallAblabesmyia phatta, had the shortest duration of the four species found, and was much the most numerous member of this subfamily. Some Chironomini only appeared when the organic coating had developed over the sand surface. Midges of this tribe frequently failed to complete their larval development within the duration of bed runs and were thus trapped on the substratum at the time of cleaning. When ponds were drained after short bed runs the succession in community structure observed in long runs was arrested.Three small midgesC. sylvestris, P. limbatellus andT. fimbriatus, were collected in high numbers throughout the life of all beds, except towards the end of the longest runs in the study. This suggests that small size, short life cycles, and the ability to colonize clean substrata, are important characteristics for the development of primary chironomid communities in short-lived temporary habitats.     

Afrochlus Freeman: an African gondwanan midge and the phylogeny of the Podonominae (Diptera: Chironomidae)

The immature stages and male adult of Afrochlus harrisoni Freeman are described for the first time, from the type locality, a granite outcrop in Zimbabwe. A phylogenetic position within the subfamily Podonominae as sister to South African-western/central Australian genus Archaeochlus Brundin, suggested in 1966 by Brundin from the adult female alone, is confirmed by cladistic analysis of all life history stages combined. Within the Podonominae, the tribes Boreochlini and Podonomini erected by Brundin are monophyletic only if Trichotanypus Kieffer is transferred from the former to the latter. Little or none of the structure provided by the combined evidence from all stages is retrieved by cladistic analyses of characters derived solely from the adult stage. The implications of erection of monotypic genera for adult-only taxa are discussed.