Sperm structure of Limoniidae and their phylogenetic relationship with Tipulidae (Diptera, Nematocera)

The sperm ultrastructure of a few species of Limoniidae (Limonia nigropunctata; L. nubeculosa; Chionea n. sp.; C. alpina; C. lutescens) was studied. The two species of Limonia have a monolayered acrosome with crystallized material, a three-lobed nucleus in cross section, a ring of centriole adjunct material and a flagellum which consists of a 9+9+1 axoneme and a single mitochondrial derivative. The central axonemal tubule is provided with 15 protofilaments in its tubular wall, while the accessory tubules have 13 protofilaments and are flanked by the electron-dense intertubular material. The three species of Chionea share a monolayered acrosome, a nucleus with two longitudinal grooves, a centriole adjunct material which surrounds the centriole and the initial part of the axoneme. The axoneme is of conventional type, with 9+9+2 microtubular pattern, with accessory tubules provided with 13 protofilaments and intertubular material. However, in C. lutescens the accessory tubules start with 15 protofilaments and transform into a tubule with 13 protofilaments. These data are discussed in the light of the phylogenetic relationship between Limoniidae and Tipulidae. For this purpose, the sperm ultrastructure of Nephrotoma appendiculata was also considered comparatively.     

Differentiation and diversification of follicular cells in polytrophic ovaries of crane flies (Diptera: Nematocera: Tipulomorpha and Trichoceridae)

To gain insight into the evolution of differentiation pathways that are involved in the follicular cells' morphogenesis in dipteran ovaries we have undertaken the comparative morphological analysis of the follicular cell behavior in crane flies, representatives of more ancestral nematocerous flies. This analysis revealed that initially the organization of the follicular epithelium in the species under study shows significant similarities to that reported in the ovaries of true flies (Brachycera), indicating that the ancestors of dipterans must have evolved a common and specific system of the early patterning of their follicular epithelium. On the other hand, in contrast to Drosophila and other advanced brachycerans, the follicular cells in the studied nematoceran ovaries do not exhibit any migratory activity. Instead, they were found to change their relative position but only within the epithelial layer. These "translocations" appeared to depend merely on cell shape changes. Although the "immobility" of the follicular cells in the ovaries of crane flies results in the lower number of their specialized subgroups when compared with the true flies, the functional homology between particular subsets of follicular cells can be postulated. We suggest that the anterior polar cells and the micropyle forming anterior terminal follicular cells in crane fly ovaries have their counterparts in the brachyceran anterior polar cells and border cells, respectively.     

Checklist of the infraorder Tipulomorpha (Trichoceridae,Tipuloidea) (Diptera) of Finland

A checklist of the infraorder Tipulomorpha: families Trichoceridae, Pediciidae, Limoniidae, Cylindrotomidae and Tipulidae (Diptera) recorded from Finland.     

First record of Trichoceridae (Diptera) in the maritime Antarctic

During the austral summer of 2006–07, abundant Diptera were found in the sewage system of the Base Científica Antártica Artigas on King George Island. These are here identified as Trichocera (Saltrichocera) maculipennis (Diptera: Trichoceridae), a Holarctic species widely distributed in the Northern Hemisphere which has been introduced to some sub-Antarctic islands, but never been recorded in the maritime Antarctic. The distribution of the fly on King George Island indicates that it has been introduced by human agency. Although its origin is unclear, adult specimens have distinctive morphological features rarely represented in autochthonous populations in Europe. To date, larvae have been found only in the Artigas Base sewage system, but adults have been observed around the buildings and more widely in the vicinity. Given the species’ natural northern range, habitats and feeding preferences, it is likely to have good preadaptation permitting survival in the natural terrestrial ecosystems of the maritime Antarctic. We recommend that urgent eradication efforts are made.     

New data on the distribution of winter gnats (Diptera,Trichoceridae) in Russia

Six species of winter gnats are recorded for the first time in the fauna of Russia: Trichocera (Trichocera) inexplorata (Dahl, 1967), T. (Saltrichocera) antennata Starý, 1999, T. (S.) calva Starý, 1999, T. (S.) dahlae Mendl, 1971, T. (S.) recondita Starý, 2000, and T. (S.) sparsa Starý et Martinovský, 1996. One species, Trichocera arctica Lundström, 1915, is transferred to the subgenus Saltrichocera. Females of T. (S.) dahlae Mendl, 1971 are described and illustrated for the first time. Occurrence of several winter gnat species in the territory of Russia is confirmed and their ranges are described.     

Feeding ecology of the freshwater detritivore Ptychoptera paludosa (Diptera, Nematocera)

1. We examined selected aspects of the nutritional ecology of larval Ptychoptera paludosa and their role in nutrient cycling in the Breitenbach, a first-order stream in Hesse, Germany.
2. Food preference experiments demonstrated significant preference for sediments with a high organic matter content and live bacteria.
3. pH was circumneutral in all sections of the gut.
4. Enzymatic activity (β-glucosidase and amino-peptidase) in different parts of the gut was measured using 4-methylumbelliferyl-β- D -glucopyranoside (MUF-Glc) and leucine-4-methylcoumarinyl-7-amide (Leu-MCA). β-glucosidase activity was highest in the hindgut.
5. The mean larval gut passage time was between 7 and 8 h.
6. The egestion rate of last instar larvae was about 0.35 mg dry weight (DW) faeces per larva h^–1 and about 1.25 mg ash-free dry weight (AFDW) faeces per mg larval AFDW day^–1.
7. Larval faeces contained at least 4–18 times more organic matter than the average in the sediments in which they were feeding, that is, larvae fed selectively, extracting organic matter from sediments.
8. P. paludosa larvae are important in the dynamics of detritus in slow-flowing reaches of the Breitenbach. They gather organic material from the sediment to a depth of 3 cm, and release it as faeces onto the sediment surface. A total of 770 g DW faeces m^–2 yr^–1, comprising about 16% organic matter, was produced by the Ptychoptera population.     

Redescription of the neotropical Psychodidae (Diptera,Nematocera) described by Rapp and Curran

Five neotropical Psychodidae collected by Curran and described cursorily by Rapp, are redescribed and figured from the type material. Their affinities are discussed. One of Curran's species is placed in synonymy.     

Species of crane flies (Diptera,Tipulidae) new for Tuva and Russia

11 species of crane flies are recorded for Tuva for the first time, among them five are also new to the Russian fauna.     

Redescription of the neotropical Psychodidae (Diptera,Nematocera) described by Knab,Dyar and Coquillet

The remarkable neotropical Psychodidae described by Knab, Dyar and Coquillet, hitherto unrecognisable, are re-defined and figured from the type material. Lectotypes are selected, and affinities discussed.     

Origin and development of the tergotrochanteral muscle in Chironomus (Diptera: Nematocera)

The origin and the development of the tubular tergo-trochanteral muscle (TTD) was studied by light and electron microscopy in Chironomus (Diptera: Nematocera). Unlike the flight muscles, the TTD was found to develop from myoblasts located around a larval axon, without contribution from a larval muscle. The myoblasts fuse together to form myotubes. Innervation of the TTD arises from the larval axon. The myotubes send out sarcoplasmic extensions towards the axon branches issued from the larval axon. The first differentiated synapses are described. The TTD begins to grow later than the flight muscles. The implications of this developmental lag are discussed.     

Revision of the fossil cylindrotomidae (Diptera,Nematocera) from florissant and White River,USA

Fossil species of the genusCyttaromyia Scudder (Diphtera, Cylindrotomidae) described by Scudder in 1877 and 1894 from the Eocene of White River Basin and the Lower Oligocène of Florissant, Colorado, are revised.Cyttaromyia fenestrata Scudder from White River andCyttaromyia princetoniana Scudder are redescribed; the remaining species: C.cancellata Scudder, C.clathrata Scudder and C.oligocena Scudder are regarded as junior synonyms of C.princetoniana.     

Biology of epiphytic Chironomidae (Diptera:Nematocera) in chalk streams

Submerged macrophytes are a conspicuous feature of chalk stream ecosystems, supporting large populations of diatoms and invertebrates, including larvae of the nematocerous family Chironomidae. Close temporal and spatial association is evident between chironomid larvae and diatoms, and diatoms are frequently a major component of the food of midge larvae. Larvae provided with food that is rich in diatoms survive better and grow and develop more quickly than larvae that are supplied with food that is predominantly fine organic detritus. First instar larvae selectively feed on diatoms but it is likely that selection is on the basis of particle size, rather than for diatoms per se. Three species of epiphytic larvae (2 Cricotopus spp. and Eukiefferiella ilkleyensis) transfer to a diet that is predominantly of fresh plant material (Ranunculus calcareus leaves) in the third and fourth instar. The life cycle strategies of many species of Orthocladiinae equip them to exploit temporarily favourable environmental conditions very rapidly and effectively. This fact helps to explain the coexistence of species with similar strategies of resource utilization, as part of the normal epiphytic fauna of chalk streams.     

Male Genital Allometry in Scathophagidae (Diptera)

Male genital structures are extremely divergent across species and sexual selection is largely responsible. Many sexually selected traits show positive allometry and have high phenotypic coefficients of variation (CV). Sexually-selected genital traits that come into contact with females during copula may be an exception to this general pattern. We compared the within species size allometry of the genital claspers, mandibular palps, and testes in a comparative study across the Scathophagidae. We additionally compared the levels of phenotypic variation in these traits and in hind tibia length. Within species, claspers typically displayed negative allometry and had low CV, indicative of stabilizing selection. In contrast, testis size was more like sexually selected display traits, typically being positively allometric and having very large CV. Palps tended to be positively allometric or isometric, and intermediate in levels of phenotypic variation, much like leg length. In spite of intraspecific stabilizing selection on the genital claspers, there has been major divergence of these characters across species. Co-ordinating editor. F. Stuefer     

X-ray induced visible alterations in the giant chromosomes of Phryne cincta (Nematocera,Diptera)

In order to induce chromosomal rearrangements, males were exposed to x-rays and then mated to non-irradiated females. The number of each type of structural alteration was determined by examination of the polytene chromosomes of the F1 progeny. -- A comparison of the results with similar studies made on Drosophila revealed a significantly greater sensitivity in Phryne. Parallel to that an extremely high frequency of small inversions was ascertained in Phryne, and the observed ratio of inversions to translocations was the inverse of that which would be expected from purely mathematical considerations based on the lengths of the different chromosomes. These facts allow the conclusion that the paternal pronuclear chromosomes in Phryne are highly spiralized. Besides, the kinetochore-to-translocation-breakpoint distance was measured in both of the chromosomes involved in each reciprocal translocation and the differences (kinetochore-break distance differences) were registered and from them the arrangement of the chromosomes in the pronucleus of Phryne deduced. The data obtained support the assumption of an ordered, polar-field type of orientation. In Drosophila, in contrast, the comparable data showed that the pronuclear chromosomes are not spiralized and are randomly arranged (Bauer, 1939). -- These results seem to indicate that a close correlation exists between the different radiation sensitivities of Drosophila and Phryne and the different states of spiralisation and arrangements of their chromosomes in the pronucleus stage. It is hypothesized that the influence of the maternal genome on the degree of spiralization of the paternal chromosomes could account for differences in the pronuclear chromosome structure of both species.     

Two aberrant species of Holorusia Loew (Diptera: Tipulidae)

A number of features of the two aberrant, sexually dimorphic, Asiatic crane-flies Holorusia carmichaeli and H.pluto are described for the first time. The possible adaptive significance of abdominal modifications in H.carmichaeli is discussed.