Der Ort der Osmoregulatorischen Salzaufnahme bei den Schwimmkäfern Dytiscus marginalis und Acilius sulcatus

Short-term experiments with hypo-osmotic, radioactive sodium chloride solutions revealed that larval Dytiscus marginalis L. and Acilius sulcatus L. (Coleoptera, Dytiscidae) take up these ions into the hemolymph almost exclusively through the intestine by drinking. Out of 20 Acilius larvae whose mouth had been occluded, 7 were also able to ingest the external solution through the anus. The results of fine-structural investigations lead to the conclusion that the ileum, which is lined by a highly differentiated transporting epithelium throughout its entire length, is the main site of ion absorption. Both the rectum, which lacks the rectal papillae, and the rectal caecum possess a thin epithelium showing no structural indications of any substantial active transport function.     

Entwicklung und Bau der Doppelspermien bei den DytiscidenAcilius sulcatus L.,Dytiscus marginalis L. undHydaticus transversalis Pont. (Coleoptera)

Zusammenfassung BeiAcilius sulcatus undDytiscus marginalis wurde die Spermiogenese bis zu den reifen Doppelspermien, beiHydaticus transversalis wurden nur die reifen Doppelspermien untersucht. Die Konjugation der Spermien dieser Arten erfolgt als letzter Schritt erst im distalen Teil des Hodenausführungsganges. Voraussetzungen für ihr Zustandekommen sind sowohl lokale Differenzierungen der Spermienmembran, alsauch spezifische polysaccharidhaltige Beläge, von denen nach dem Aussehen sowie nach Zeitpunkt und Ort ihres Auftretens vier unterschieden werden können, die teils schon im Zystenlumen, teils erst nach Eindringen des Spermienvorderendes in tiefe Fächer der Zystenwandzellen gebildet werden. Die mit allen Belägen versehenen Einzelspermien treten zusammen mit abgeschnürten Resten der Zystenwandzellen in den Ausführungsgang ein, dessen Epithel die Plasmareste der Zystenwandzellen phagozytiert. Die Beläge der Spermien sind nach der Konjugation verändert. Damit muß als letzte Bedingung für das Zustandekommen des Aneinanderhaftens noch eine Reaktion im Ausführungsgang stattfinden. Weiterhin wurde die Entwicklung des als microtubular border beschriebenen Strukturelements im Schwanz verfolgt und als centriole adjunct identifiziert, welches sich aus Kernmaterial herleitet und zu einem Geißelbegleitkörper modifiziert hat. Schließlich wird auf anscheinend regelmäßige und in zeitlich abgestimmter Folge auftretende Beziehungen des Endomembransystems zu den sich differenzierenden Strukturen der Spermatide hingewiesen.

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Development and structure of the conjugate sperm of the dytiscidaeAcilius sulcatus L.,Dytiscus marginalis L. andHydaticus transversalis pont. (Coleoptera)

Summary Spermiogenesis and structure of the double sperm have been investigated inAcilius sulcatus andDytiscus marginalis whereas only mature double sperm have been studied inHydaticus transversalis. The conjugation of the sperm in these species is accomplished as a last step in the distal part of the vas deferens. Preconditions for the pairing are local differentiations of the sperm membrane in combination with specific layers of polysaccharids. According to their aspect as well as the chronological order and place of their appearance four such layers can be discerned. These are formed in part still in the lumen of the cyst, in part not earlier than after the anterior ends of the sperm have deeply entered into recesses of the surrounding cyst wall cells. Single sperm supplied with all layers and cytoplasmic remnants pinched off from the cyst wall cells enter the vas deferens where the cytoplasmic remainders are phagocytised by its epithelial cells. The layers of the sperm are transformed after conjugation. Thus as a last precondition for the occurrance of pairing a reaction in the vas deferens must take place. Furthermore, the development of the structural element of the tail described as microtubular border has been traced and identified as a centriole adjunct derived from nuclear material and modified to a body accompanying the flagellum. Finally, it is pointed out that apparently regular relationships in temporally correlated sequence exist between the endomembranous system and differentiating structures of the spermatid.

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Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.

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För die rasterelektronenmikroskopischen Aufnahmen der Abb. 9 danke ich Frau L. Schulz, Homburg, verbindlichst. Die Teilbilder 16g u. h konnten mit einem Siemens Elmiskop 102 aufgenommen werden. För die Anfertigung dieser Aufnahmen bin ich Frau Dr. C. Weichan, Berlin, zu Dank verpflichtet.     

Gene amplification in the oocytes of dytiscid water beetles

A conspicuous mass of extrachromosomal DNA (Giardina's body) is found in oogonia and oocytes of Dytiscid water beetles. Since in older oocytes this DNA is associated with numerous nucleoli, it seemed probable that the ovary might contain extra copies of the genes for ribosomal RNA (rRNA). This hypothesis has been confirmed by centrifugation and molecular hybridization studies. —In Dytiscus marginalis and Colymbetes fuscus a high density satellite DNA is found in somatic cells and in sperm. Hybridization experiments show that all of the rDNA, i.e., those sequences complementary to rRNA, are located in this satellite, although quantitatively they make up only a small fraction of the satellite. In both species the DNA isolated from ovariole tips is enriched with respect to the satellite. A parallel enrichment of the rDNA has been shown in ovariole tips of Colymbetes, but for technical reasons has not been examined in Dytiscus. —The following model is proposed. In somatic cells and sperm the rDNA is part of an extensive region of high density DNA in one or more chromosomes. In oogonia and oocytes the entire high density region is replicated extrachromosomally and appears cytologically as Giardina's body.     

Diving beetles (Dytiscidae) as predators of mosquito larvae (Culicidae) in field experiments and in laboratory tests of prey preference

Field experiments were performed in artificial ponds to evaluate how the density of predatory diving beetles (Dytiscidae) would affect the population levels of mosquito larvae (Culicidae). Mosquitoes colonizing the ponds were predominantly species of the genus Culex. In 2000, most of the dytiscids colonizing the ponds were small (Hydroporus spp.), and these predators had no impact on the size of larval mosquito populations, not even in ponds with added dytiscids. In 2001, larger beetles (Ilybius, Rhantus, and Agabus spp.) were more common, and there were significantly fewer mosquito larvae in ponds with the highest numbers of dytiscids. There was a negative correlation between numbers of diving beetles in the ponds and the mean body length of mosquito larvae. In neither year could dytiscid densities be maintained above a certain level owing to emigration. In laboratory tests, there were marked differences between three common dytiscid species in regard to preferences for Daphnia and Culex species as prey: Colymbetes paykulli Erichson chose mosquito larvae more often, whereas both Ilybius ater (De Geer) and I. fuliginosus (Fabricius) preferred Daphnia spp. All of the tested dytiscids consumed large numbers of prey. Since some dytiscid species can efficiently decrease populations of mosquito larvae, they are probably important in the natural control of these dipterans.     

Field observation of foraging behavior by a group of adult diving beetles Agabus (Gaurodytes) bipustulatus preying on an adult Lissotriton boscai

Adult dytiscids prey on a variety of items including other invertebrates but also larger prey such as frogs and fish. Observations of anuran larvae predation are common. However, there have been no reports concerning predation on caudata post‐metamorphosis by dytiscids. Here we describe a predation event by a group of adult diving beetles of the species Agabus (Gaurodytes) bipustulatus (Linnaeus, 1767) on an adult Lissotriton boscai (Lataste in Tourneville, 1879). This report represents the first observation of foraging behavior of adult diving beetles preying on and consuming a living post‐metamorphic newt.     

Speciation and mitochondrial DNA diversification of the diving beetles Agabus bipustulatus and A. wollastoni (Coleoptera, Dytiscidae) within Macaronesia

Diversification of populations of two morphologically similar diving beetles within the Agabus tristis group, A. wollastoni and A. bipustulatus, was investigated, with partial mtDNA cytochrome b (Cyt b) sequences, allozymes and landmark‐based morphometrics. The Madeiran endemic A. wollastoni was collected from 11 localities. Population genetic and morphological variation was compared to Scandinavian localities of the widespread west Palearctic A. bipustulatus, recorded also from the Azores. Agabus wollastoni and European A. bipustulatus specimens representing eight and 13 localities respectively, were used in evaluating their phylogenetic relationship. Maximum parsimony analysis of the Cyt b sequences showed that both the A. bipustulatus and A. wollastoni specimens form well‐supported monophyletic groups. Three lines of evidence suggest that Agabus wollastoni has speciated through a few founders: (1) a well‐supported mtDNA line; (2) the mean heterozygosity of A. wollastoni is lower when compared to A. bipustulatus on the mainland; and (3) several uncommon alleles of A. bipustulatus are missing in A. wollastoni. The Azorean A. bipustulatus population was drastically affected by the colonization event, since several loci have become fixed with a resulting lower mean heterozygosity. The colonization was relatively recent, as the mtDNA lineage represented in the Azores is deeply nested within the A. bipustulatus clade. Population structure shows moderate inbreeding of A. wollastoni, and extensive substructuring at all localities with moderate gene‐flow between them. Morphological variation in A. wollastoni showed significant differentiation among several populations. Island colonizations, population structure of A. wollastoni, and an observed pattern of variation of the α‐glycerophosphate dehydrogenase locus are discussed. © 2003 The Linnean Society of London, Biological Journal of the Linnean Society, 2003, 79, 653–666.     

Responses of Acilius sulcatus (Coleoptera: Dytiscidae) to chemical cues from perch (Perca fluviatilis)

In this study we tested the hypothesis that the presence of chemical stimuli from a hungry predator would initiate anti-predator responses, while stimuli from a satiated predator would not. We used chemical stimuli released from starved perch (Perca fluviatilis) and from satiated perch (predator). As prey we used adult Acilius sulcatus (Coleoptera: Dytiscidae). The reaction of the beetles to different predator conditions was tested during daytime. We also tested the reaction to starved perch during the night. A. sulcatus activity decreased when it was exposed to stimuli released from starved perch during daytime when visibility was poor, due to the presence of artificial vegetation. There was, however, no reaction to satiated perch under the same experimental conditions. These results indicate that A. sulcatus can discriminate between chemical cues from hungry and satiated fish predators. When visibility was good and the concentration of chemical cues was constant, the beetles did not react to starved perch in the daytime, but their activity decreased at night in response to stimuli released from starved perch. Visual as well as chemical cues seem to be important for detecting a potential predator. When visibility is good, beetles seem to rely on visual stimuli, while in darkness they seem to use chemical stimuli to detect the presence of predators. Received: 4 October 1996 / Accepted: 7 February 1997     

Weight–length relationships of some fish species of the Iberian Peninsula

This study reports weight–length relationships (WLR) for Salmo trutta (Linnaeus, 1758), Phoxinus phoxinus (Linnaeus, 1758), Chondrostoma Chondrostoma miegii (Steindachner, 1866), Barbus graellsii (Steindachner, 1866), Barbatula barbatula (Linnaeus, 1758) and Gobio gobio (Linnaeus, 1758). Specimens were collected by electrofishing during summer between 1996 and 1998. The b values in the WLR W = aL^b varied between 2.97 and 3.42. To the best knowledge of the authors, this study presents the first reference on WLRs for four of the species in Spanish waters.     

Taxonomic composition and species diversity of insect assemblages in grass–shrub cover of peat bogs in Belarus

The species composition and diversity of insect assemblages in the grass–shrub cover has been studied. A total of 374 species from 10 orders have been revealed. Coleoptera, Diptera, Heteroptera, and Auchenorryncha prevailed. Each order was dominated by two to eight species. These species are Cixius similis Kirschbaum, 1868; Neophilaenus lineatus (Linnaeus, 1758); Lepyronia coleoptrata (Linnaeus, 1758) (Auchenorryncha); Lygus pratensis (Linnaeus, 1758); Kleidocerys resedae (Panzer, 1797); Stictopleurus crassicornis (Linnaeus, 1758) (Heteroptera); Lochmaea suturalis (Thomson, 1866); Cyphon padi (Linnaeus, 1758); Plateumaris discolor (Herbst, 1795) (Coleoptera); etc. The assemblages were characterized by low species diversity and distribution of species abundance. The most similar entomocomplexes were those in biotopes dominated by herbs, on the one hand, and dwarf shrubs, on the other. The regression analysis has shown a significant relation between the species richness and diversity of insects and the species composition of plants and their projective cover. The multivariate analysis with various methods (CCA and PCA) demonstrated the influence of these factors on the spatial distribution of certain species and their preferences to particular habitats.     

Length–weight and length–length relationships for 10 pelagic fish species from the Adriatic Sea (Croatia)

Length–weight and length–length relationships are described for 10 of the most important and most frequent small, middle‐size and large pelagic fish species from the Adriatic Sea, namely Sardina pilchardus Walbaum 1792, Sardinella aurita Valenciennes 1847, Sprattus sprattus Linnaeus 1758, Engraulis encrasicolus Linnaeus 1758, Belone belone Linnaeus 1761, Scomber scombrus Linnaeus 1758, Scomber japonicus Houttuyn 1780, Thunnus thynnus Linnaeus 1758, Auxis rochei Risso 1810 and Sarda sarda Bloch 1793. Length–length equations for converting size measurements: standard length (SL) and fork length (FL) to total length (TL) and vice versa, were linear.     

Confirmed occurrence of the Cusk-eel <Emphasis Type="Italic">Ophidion barbatum</Emphasis> (Osteichthyes: Ophidiidae) from the Coast of Tunisia (Central Mediterranean)

This paper reports the second record but also the first substantiated record of cusk-eel Ophidion barbatum (Linnaeus, 1758) from the northern coast of Tunisia, 168 mm in total length and weighing 18.3 g. The specimen is described including morphometric measurements and counts. Differences from its close relative species O. rochei (Linnaeus, 1758) are pointed out that confirm the occurrence of O barbatum in the Tunisian waters. This finding constitutes the northernmost extension range of the species in the area.     

Development of microsatellite markers for an extremely limited distributed rare diving beetle species,Acilius kishii,and a widely distributed species,Acilius japonicus (Coleoptera: Dytiscidae)

Acilius kishii Nakane, 1963 (Coleoptera: Dytiscidae) is an endangered diving beetle species distributed in only one location, Lake Yashaga‐Ike, Honshu Island, Japan. Acilius japonicus, which is related to A. kishii, is distributed widely in northern Honshu Island and Hokkaido Island in Japan. In this study, we identified 14 microsatellite loci for A. kishii and A. japonicus, including both polymorphic and monomorphic loci, using the next‐generation sequencing method. We observed that 5 and 10 loci showed polymorphisms in 31 and 32 individuals of A. kishii and A. japonicus, respectively. The observed and expected heterozygosities were 0.00–1.00 and 0.00–0.74, respectively. These microsatellite loci could be useful for future conservation genetic studies, including monitoring of genetic diversity and extinction risk of A. kishii.     

The Mercury Content and Antioxidant System in Insectivorous Animals (Insectivora,Mammalia) and Rodents (Rodentia,Mammalia) of Various Ecogenesis Conditions

This study is aimed at analyzing the total mercury in the tissues of mammals adapted to a semiaquatic or subterranean lifestyle and at analyzing the possible role of their antioxidant system in heavy metal detoxication. The water shrew Neomis fodiens Pennant, 1771, European mole Talpa europaea Linnaeus, 1758, muskrat Ondatra zibethicus Linnaeus, 1766, and water vole Arvicola terrestris Linnaeus, 1758 were the species under study. Our results indicate that mercury accumulation in the tissue depends on the age, tissue type, and diet of the species. The highest mercury content was recorded in water shrew tissues compared to other species. Age-dependent accumulation of the toxicant in the animals is reported. A correlation between mercury accumulation and catalase activity in the kidneys of the animals studied was found.     

Musculature of the Male Abdominal Segments and Terminalia in <Emphasis Type="Italic">Musca autumnalis</Emphasis> De Geer, 1776 and <Emphasis Type="Italic">Pyrellia rapax</Emphasis> (Harris, 1780) (Diptera,Muscidae: Muscini)

The structure of the abdominal and pregenital segments and genitalia of males was studied in Pyrellia rapax (Harris, 1780) and Musca autumnalis De Geer, 1776 (Muscidae, Muscini). The musculature of these species is compared with that in Musca domestica Linnaeus, 1758 (Muscidae) and Scathophaga stercoraria (Linnaeus, 1758) (Scathophagidae), previously investigated by O.G. Ovtshinnikova. Morphological analysis of sclerites and muscles of abdominal and pregenital segments and genitalia of males in Pyrellia rapax, Musca autumnalis, and M. domestica demonstrates processes of reduction in Musca as compared with P. rapax and S. stercoraria.     

Koi herpesvirus infection in experimentally infected common carp Cyprinus carpio (Linnaeus, 1758) and three potential carrier fish species Carassius carassius (Linnaeus, 1758); Rutilus rutilus (Linnaeus, 1758); and Tinca tinca (Linnaeus, 1758) by quantitative real‐time PCR and in‐situ hybridization

Only single cells in the carrier fish species Carassius carassius (Linnaeus, 1758) for koi herpesvirus (KHV) are infected in contrast to large numbers in the susceptible species common carp Cyprinus carpio (Linnaeus 1758). Several species of the family Cyprinidae have been described as virus carrier species, showing no clinical signs of a KHV disease but able to transmit the virus to other susceptible fish. In this study, 72 common carp Cyprinus carpio (Linnaeus, 1758), 36 tench Tinca tinca (Linnaeus, 1758), 36 crucian carp Carassius carassius (Linnaeus, 1758) and 36 common roach Rutilus rutilus (Linnaeus, 1758) were experimentally infected with KHV (isolate “Israel”) by immersion and kept at 20°C. The fish were euthanized at 12 timepoints over a period of 90 days and virus DNA was quantified in tissues by a real‐time TaqMan PCR. Whereas KHV‐DNA was found in Cyprinus carpio for up to 90 days, the virus DNA was detectable only in single individuals of Rutilus rutilus, Tinca tinca and Carassius carassius for up to 25 days after experimental virus exposure. Tissue samples of Cyprinus carpio and Carassius carassius were screened by in‐situ hybridization. Positive signals were found in various organs of the common carp tested crucian carp. In the latter species a much smaller number of virus‐positive stained cells was detected compared to the infected carp.     

Introgression and species demarcation in western European Leuctra fusca (Linnaeus, 1758) and L. digitata Kempny, 1899 (Plecoptera: Leuctridae)

The compilation of a DNA barcoding library of Norwegian stonefly (Plecoptera) species revealed that Leuctra fusca (Linnaeus, 1758 Linnaeus, C. (1758), Systema naturae Per Regna Tria Naturae: Secundum Classes, Ordines, Genera, Species, Cum Characteribus, Differentiis, Synonymis, Locis. Stockholm: Laurentius Salvius. [Google Scholar]) and Leuctra digitata Kempny, 1899 (Leuctridae) share haplotypes in northernmost Scandinavia. Phylogenetic analyses of the mitochondrial (mt) DNA barcode marker COI and the nuclear marker 28S show that the shared haplotypes must result from the introgression of a L. fusca mitochondrion into a L. digitata population on at least two occasions. Although mt introgression is widespread in animals, this represents the first documented case in Plecoptera. This study also included specimens of L. cf. fusca from the Sierra Nevada massif in Spain, a population previously known as L. carpentieri Despax, 1945. Their mt haplotypes are ca. 13% different from other European L. fusca. However, their 28S alleles are compatible with their morphological identification as L. fusca. In view of the possibility of mt introgression, the taxonomic status of this population remains undecided.     

Abundance,population dynamics and production of Chironomidae (Diptera) in an ul traoligotrophic lake in South Greenland

Macrozoobenthos of the ultraoligotrophic Lake 95 (61°N, 46°W, 8 ha, z_max=18 m, ) is composed of about 14 taxa dominated by 12 Chironomidae species. Abundance, life cycle, biomass and production were estimated for the six dominant taxa. Abundance declined fromca. 4150 at 2.5 m depth toca. 1400 ind m^–2 at 16 m depth and averagedca. 3200 ind m^–2 on a lakewide basis. By numbers,Heterotrissocladius changi andH. oliveri dominated the average fauna.H. changi was common at the 2.5 m and 5 m depth stations, whereasH. oliveri dominated from 5 m depth downwards. Chironomids showed mainly a 1-yr life cycle, but apparently bothHeterotrissocladius species had two contemporary cohorts with emergence in midsummer and late autumn/early spring, respectively. Average annual ratio was 4.2 and 4.6 forH. oliveri andH. changi, respectively. Annual production varied from 0.3 g ash-free dry weight (AFDW) m^–2 y^–1 at 16 m depth to 1.6 g AFDW m^–2 y^–1 at 2.5 m depthH. changi contributed 45%, fiveMicropsectra spp. 17% andH. oliveri 15% to total average production, which on a lakewide basis wasca. 1.1 g AFDW or 25 kJ m^–2 y^–1. Lake 95 thus belongs at the very low end of measured lake zoobenthic productions, which range from 10 kJ m^–2 y^–1 in Arctic lakes toca. 1600 kJ m^–2 y^–1 in highly eutrophic shallow lakes.     

The Noctuoidea (Lepidoptera) described by Linnaeus

Linnaeus described 166 nominal species of Noctuoidea, of which 144 (86.7%) are currently used as valid names, 18 are synonyms, one is a homonym and three taxa remain unknown. Seven taxa were described solely from illustrations in contemporary literature. Lectotypes are designated for 139 (87.4%) of the 159 remaining taxa, 122 of them from the Linnaean collection in London, 13 from the Queen Ludovica Ulrica's collection in Uppsala, Sweden, and four from other contemporary collections. Two Linnaean senior synonyms are introduced: Hada plebeja comb. nov. (Linnaeus, 1761) for the current H. nana (Hufnagel, 1766) and Oeonistis altica (Linnaeus, 1768) comb. nov. for Oe. entella (Cramer, 1779). Erebus occiduus (Linnaeus, 1758) syn. nov. is a junior subjective synonym of E. crepuscularis (Linnaeus, 1758); L. marmorides (Cramer, 1775) Stat. rev. should be reinstated for Letis occidua auct. In two species pairs the Linnaean names have been interpreted incorrectly. The lectotype designation of Phalaena prasinana Linnaeus, 1758, by Lempke (1947) is invalid because the specimen is not syntypic. According to the new lectotype, Pseudoips prasinanus (Linnaeus, 1758) comb. nov. replaces P. faganus (Fabricius, 1781), and Bena bicolorana (Fuessly, 1775) comb. nov. is available for the other species. Abrostola triplasia (Linnaeus, 1758) Stat. rev. replaces A. trigemina (Werneburg, 1864), and for the other species A. triparlila (Hufnagel, 1766) should be reinstated. One neotype designation [Eilema complanum (Linnaeus, 1758)], one lectotype designation [Xylena exsolela (Linnaeus, 1758)], and precedence of a junior synonym [Ophideres fullonia (Clerck, 1764)] over its unused senior synonym are to be referred to the ICZN; until their decision the current usage must be followed. The identity of Mesapamea secalis (Linnaeus, 1758) stat. rev. corresponds to current usage, but, under presence of syntypic material, the recent neotype designation by Lempke (1988) will be referred to the ICZN. The revision is mainly based on the discovery that the insect pins and the way specimens are prepared give evidence of the authenticity of the material. Contrary to the views of earlier authors, Linnaeus had his labels with the specific name pinned against the bottom of the drawers by the specimen pin. Because the labels have been moved twice during subsequent curations, their present position is less indicative of the authenticity than has been previously suggested. The origin of the so-called n-labels is discussed.     

A laboratory study of predation on lake-dwelling triclads

Summary Predation on four species of triclads was investigated by exposing them to likely predators in the laboratory. The only serious littoral predators would seem to be dragonfly nymphs and adult Dytiscus marginalis. Although fish devoured triclads to some extent it is argued that predation by these in nature is unlikely. The slow movement and distastefulness of triclads contribute to their protection.

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Zusammenfassung Als raubtierhafte Beute wurden vier Trikladen-Arten untersucht, indem these im Laboratorium geeigneten Raubtieren ausgesetzt wurden. Die Libellennymphe und die Dysticus marginalis-Imago sind in der Uferregion des Sees anscheinend die einzigen Raubtiere von Belang. Zwar haben auch Fische Trikladen einigermassen verschlungen; dass jene in der Natur von Trikladen futtern, wird aber hier bezweifelt. Zu den Schutzmitteln der Trikladen tragen die langsame Bewegung und der unangenehme Geschmack bei.