The dipteran sperm tail: ultrastructural characteristics and phylogenetic considerations

The sperm tail from representatives of several families of Diptera has been examined by high resolution electron microscopy and a computer analysis that improved the visualization of recorded patterns. A considerable variability in sperm tail structure is found within Diptera, and is actually greater than that of any other insect order. The 'generalized insect sperm axoneme'. which is characterized as a 9+9+2 axoneme and by the accessory microtubules having 16 protofilaments, was found only in some dipterans; these are members of Mycetophilidae. From this fact we conclude that Mycetophilidae is likely to be the most primitive extant dipteran group. Another mycetophilid, Boletina , was seen to have accessory tubules with 15 protofilaments as have members of families Dixidae, Chironomidae, Culicidae, and Bibionidae. The last two families have spermatozoa of a type designated as 9+9+'1' there is a central rod rather than two microtubules. We regard this 9+9+'1'pattern with 15 protofilaments to represent a synapomorphic feature. Representatives of the neatoceran families Tipulidae and Trichoceridae have accessory tubules with 13 protofilaments as do examined members of several brachyceran families. Brachycera is hence likely to be derived from the vicinity of the tipulid family. The intertubular material is small in Mycetophilidae and most nematoceran groups, whereas in Tipulidae and Brachycera it is enlarged; here it bridges the space between the accessory tubules and contains various inclusions.     

Lost in translation – a history of systematic confusion and comments on the type species of Squalodon and Patriocetus (Cetacea,Odontoceti)

Abstract: The two odontocete taxa Squalodon grateloupii and Patriocetus ehrlichii, both the type species of their respective genera, have been at the centre of a great deal of taxonomic confusion. Originally regarded to be conspecific, these two taxa have been the subject of a bewildering taxonomic debate lasting for more than a century, which recently led to the suggestion to abandon these widely used names and replace S. grateloupii with the similar, yet independently and later proposed name S. gratelupi as the type species of Squalodon. Here, we attempt to summarise the events leading to the current confused situation in the hope of resolving this issue once and for all and argue that the name Squalodon grateloupii, as originally proposed, should be reinstated.     

Morphology and Infraciliature of Trochiliopsis australis N. Sp., Pelagohalteria viridis (Fromentel, 1876) N. G., N. Comb., and Strobilidium lacustris N. Sp. (Protozoa,Ciliophora)1

Three ciliate species from Australia and Norway were examined by silver impregnation, biometry, and scanning electron microscopy. Trochiliopsis australis n. sp. (order Nassulida, family Microthoracidae) differs from the single other known species of the genus, T. opaca, by its prominent ridges on the left side, the distinctly longer anterior segment of somatic kinety 2, and by the doubled total number of kinetosomes. Pelagohalteria n. g. (order Oligotrichida, family Halteriidae) differs from Halteria by the structure of the bristle complexes, which are composed of a vertically and a horizontally oriented row of kinetosomes. Two Halteria species belong to the new genus: P. viridis (Fromentel, 1876) n. comb., which is redescribed here, and P. cirrifera (Kahl, 1935) n. comb. Strobilidium lacustris n. sp. (order Oligotrichida, family Strobilidiidae) differs from its nearest relative, S. velox, by the smooth pellicle, the absence of symbiotic green algae, and by its larger size.     

APPLIED ISSUES Replacement of the native crayfish Astacus astacus by the introduced species Pacifastacus leniusculus in a Swedish lake: possible causes and mechanisms

1. The introduced North American crayfish Pacifastacits leniusculus is currently replacing the native crayfish Astacus astacus in a Swedish lake. Using field data from co-occurring populations on life-history traits and population size structure of the two species, this study evaluated possible mechanisms behind the replacement. 2. Pacifastacus showed a higher capacity for population increase; the species had a higher individual growth rate, reached sexual maturity at a smaller size and lower age, and had a higher per capita egg production than Astacus. 3. A higher frequency of non-lethal injuries in Astacus suggested the predominance of Pacifastacus in interference interactions. These results support a competitive exclusion hypothesis. 4. A dramatic change in relative abundance of the two species in recent years was the result of an almost complete cessation in recruitment of young-of-the-year (YOY) in Astacus. Poor recruitment in Astacus was probably caused by the combined effects of interspecific competition and predation, resulting in increased mortality among YOY Astacus, and by reproductive interference, suppressing the less common species. 5. The results support the hypothesis that the observed replacement of Astacus by Pacifastacus is governed by a combination of several interacting mechanisms, of which     

Ceratophyllum demersum hampers phytoplankton development in some small Norwegian lakes over a wide range of phosphorus concentrations and geographical latitude

1. Data on submerged and floating-leafed macrophytes, phytoplankton, nutrients (N, P) and calcium were collected from twenty-four small lakes ( 1 km²) over a wide range of latitudes in Norway. The majority of the investigated lakes were mesotrophic or eutrophic, and most of the lakes were markedly affected by diffuse and point-source runoff from agriculture. According to their macrophyte species composition, the majority of the lakes can be classified as Potamogeton lakes or Chara lakes, or a combination of these.
2. This study is consistent with the 'two alternative stable states' hypothesis. We observed clearwater lakes with dense macrophyte cover over a wider range of total P concentration than has been reported previously: from 30 to more than 700 mg P m^–3. The clearwater state was only observed in lakes with mean depths of less than 1.9 m.
3. Most clear lakes with high cover of submerged vegetation showed indications of N limitation.
4. In this study nearly all the macrophyte-dominated lakes with P concentrations above 30 mg m^–3 had dense stands of Ceratophyllum demersum (L.). This indicates that Ceratophyllum may also play an important role in stabilizing and maintaining a clearwater state at high P concentrations.     

Simple Methods for the Calibration of Light Measuring Equipment

Simple methods are described for

• a) absolute calibration of thermal radiation detectors (thermopiles, bolometers);
• b) absolute calibration at various wavelengths of photoelectric devices;
• c) obtaining the relative spectral sensitivity of the detector systems of spectrofluorimeters.

The procedures require no special standard lamp or other exotic equipment. The methods depend on the computation of the radiation characteristics of an ordinary tungsten lamp at various measured voltages and currents.     

The ciliated epidermis of Xenoturbella bocki (Platyhelminthes, Xenoturbellida) with some phylogenetic considerations

The epidermis of Xenoturbella bocki Westblad was studied by scanning and transmission electron microscopy. Two cell types predominate in the epidermis: multiciliated epidermal cells and non-ciliated or monociliated gland cells. A conspicuous feature is the dense ciliary coverage and the numerous gland cell openings. Xenoturbella has a characteristic pattern of axonemal filament termination in the distal tips of their cilia. Each epidermal cilium has the typical 9 + 2 patten through the major part of its shaft. Near the tip there is a shelf at which doublets 4–7 terminate. Doublets 1, 2, 3, 8 and 9 continue into the thinner distal part of the cilium. A similar shelf in cilia is known only from the turbellarian orders Nemertodermatida and Acoela, and hence may be an apomorphic feature which indicates a close relationship between Xenoturbellida, Nemertoder-matida and Acoela. The basal body is provided with a so-called basal foot which has a cross-striated appearance and an expanded distal plate that seems to act as a microtubule organizing center. Approximately 15–25 microtubuli radiate from the endplate of the basal foot to the basal bodies caudally. The arrangement of basal foot and ciliary rootlets in Xenoturbella differs from that of Acoela and related orders in that there are two striated rootlets only (an anterior and a posterior one), rather than one main rootlet and two lateral rootlets.     

Molecular evolution of rodent insulins

Several trees of amino acid sequences of rodent insulins were derived with the maximum-parsimony procedure. Possible orthologous and paralogous relationships were investigated. Except for a recent gene duplication in the ancestor of rat and mouse, there are no strong arguments for other paralogous relationships. Therefore, a tree in agreement with other biological data is the most reasonable one. According to this tree, the capacity to form zinc-binding hexamers was lost once in the ancestor of the hystricomorph rodents, followed by moderately increased evolutionary rates in the lineages to African porcupine and chinchilla but highly increased rates in at least three independent lines to other taxa of this suborder: guinea pig, cuis, and Octodontoidea (coypu and casiragua).      

Genotypic differences in embryonic life history traits of Folsomia quadrioculata (Collembola: Isotomidae) across a wide geographical range

1. Life history traits play a central role in adaptation to specific environmental conditions. Egg development time, hatchling, and egg batch size in 10 populations of the soil‐dwelling collembolan species Folsomia quadrioculata (Tullberg, 1871) from diverse habitats across arctic and temperate regions, ranging in latitude from 43 to 81°N were studied. 2. For all traits, 15 °C was used as the reference temperature. Phenotypic plasticity was studied by changing temperature to 10 and 20 °C in hatchling size, and to 20 °C in egg development time. The effect of latitude, climatic zone, and summer temperature at their sites of sampling was tested to address the hypotheses that populations from cooler areas would have (i) a faster temperature‐dependent egg development, (ii) a larger hatchling size, (iii) smaller egg batches and (iv) higher phenotypic plasticity 3. The first and fourth hypothesis were not supported, whereas the second and third were partly supported when including the whole latitudinal gradient, but not within regions. Plasticity showed a complex pattern, including large differences between populations from similar macroclimates and considerable similarity between some populations from contrasting climates. Small effects of latitude and macroclimatic variables emphasised that local climate and microhabitat should be taken into account when evaluating thermal conditions as possible drivers of population‐specific differences in soil‐dwelling ectotherms. 4. There was a trade‐off between egg batch and hatchling sizes. A weak correlation between the population mean egg development time and the mean hatchling size suggested that the populations are, or have been, exposed to differential selection.     

Miocene methane‐derived carbonates from southwestern Washington,USA and a model for silicification at seeps

Kuechler, R.R., Birgel, D, Kiel, S, Freiwald, A, Goedert, J.L., Thiel, V & Peckmann, J. 2011: Miocene methane‐derived carbonates from southwestern Washington, USA and a model for silicification at seeps. Lethaia, Vol. 45, pp. 259–273. Exotic limestone masses with silicified fossils, enclosed within deep‐water marine siliciclastic sediments of the Early to Middle Miocene Astoria Formation, are exposed along the north shore of the Columbia River in southwestern Washington, USA. Samples from four localities were studied to clarify the origin and diagenesis of these limestone deposits. The bioturbated and reworked limestones contain a faunal assemblage resembling that of modern and Cenozoic deep‐water methane‐seeps. Five phases make up the paragenetic sequence: (1) micrite and microspar; (2) fibrous, banded and botryoidal aragonite cement, partially replaced by silica or recrystallized to calcite; (3) yellow calcite; (4) quartz replacing carbonate phases and quartz cement; and (5) equant calcite spar and pseudospar. Layers of pyrite frequently separate different carbonate phases and generations, indicating periods of corrosion. Negative δ¹³C_carbonate values as low as ?37.6‰ V‐PDB reveal an uptake of methane‐derived carbon. In other cases, δ¹³C_carbonate values as high as 7.1‰ point to a residual, ¹³C‐enriched carbon pool affected by methanogenesis. Lipid biomarkers include ¹³C‐depleted, archaeal 2,6,10,15,19‐pentamethylicosane (PMI; δ¹³C: ?128‰), crocetane and phytane, as well as various iso‐ and anteiso‐carbon chains, most likely derived from sulphate‐reducing bacteria. The biomarker inventory proves that the majority of the carbonates formed as a consequence of sulphate‐dependent anaerobic oxidation of methane. Silicification of fossils and early diagenetic carbonate cements as well as the precipitation of quartz cement – also observed in other methane‐seep limestones enclosed in sediments with abundant diatoms or radiolarians – is a consequence of a preceding increase of alkalinity due to anaerobic oxidation of methane, inducing the dissolution of silica skeletons. Once anaerobic oxidation of methane has ceased, the pH drops again and silica phases can precipitate. □Biomarkers, carbonates, isotopes, methane, Miocene, silicification, Washington.