Stable isotope proxies for evaluating biodiversity in stream biota

Differences in δ¹³C and δ¹⁵N values in stream biota are caused by several environmental conditions. Variations in abundance, species richness and the assemblage structure of stream biota are also caused by several environmental conditions. Hence, abundance, species richness and the assemblage structure of stream biota are expected to be strongly correlated with the differences in value of stable isotopes. In this study, the gaps in δ¹³C and δ¹⁵N between periphyton and charr are discussed in terms of the abundance, genus richness, and assemblage of benthic invertebrates at each site. Gaps in δ¹³C between periphyton and charr were strongly correlated with some aspects of mountainous area and the genus richness of benthic invertebrates at each site. The gaps in δ¹⁵N between periphyton and charr were strongly correlated with the abundance and assemblage structure of benthic invertebrates at the location tested. The δ¹³C values of predators were correlated with some aspects of mountainous area and the assemblage structure of the benthic invertebrates. The δ¹⁵N values of predators were correlated with genus richness and the assemblage structure of the benthic invertebrates. These results suggest that the value gaps in δ¹³C and δ¹⁵N can be used to assess biodiversity and could provide indices for estimating the biodiversity in a stream.     

Stoichiometry of aerobic mineralization (O/C) of aquatic macrophytes leachate from a tropical lagoon (São Paulo –Brazil)

The temporal variation of stoichiometry between consumed oxygen and oxidized carbon was investigated for the aerobic mineralization of leachates from aquatic macrophytes. Seven species of aquatic plants, viz. Cabomba piauhyensis, Cyperus giganteus, Egeria najas, Eichhornia azurea, Salvinia auriculata, Scirpus cubensisand Utricularia breviscapa, were collected from Òleo lagoon located in the floodplain of Mogi-Guacu river (São Paulo State, Brazil). After being collected, the plants were washed, oven-dried and triturated. In order to obtain the leachate, the fragments were submitted to an aqueous extraction (cold). Mineralization chambers were incubated at 20 °C containing leachates dissolved in water samples from Òleo lagoon to a final concentration of ca. 200 mg l^–1on carbon basis. The chambers were maintained under aerobic conditions; the concentrations of the organic carbon (particulate and dissolved) and the dissolved oxygen were measured during approximately 80 days. Elemental analysis of the detritus and the concentrations of the remaining material (DOC and POC) were used to determine the amounts of mineralized organic carbon. The data were analyzed with first-order kinetics models, from which the daily rates of consumption (carbon and oxygen) and the stoichiometry (O/C) were determined. In the early phase of mineralization the O/C rates increased before reaching a maximum, after which they tended to decrease. For the mineralization of leachates from C. giganteus, S. auriculata and U. breviscapa, the decrease was relatively slow. For all substrata the initial values were smaller than 1, and ranged from 0.42 (S. cubensis) to 0.81 (C. piauhyensis). The maximum values were within the range from 0.58 (U. breviscapa) to 23.1 (E. najas) and at their highest 26th (C. piauhyensis) and 106th (C. giganteus) days. These variations are believed to be associated with the chemical composition of the leachates, with their transformations and alterations of metabolic pathways involved in the mineralization.     

A comparison of phenetic and phylogenetic methods applied to the systematics of Oligochaeta

A comparative study of naidid subfamilies shows that a combination of ordination, Jaccard/Average Linkage cluster analysis and Wagner parsimony provides a useful basis for a rational phylogeny but that this does not differ markedly from the original proposed by Sperber nearly four decades ago. Hennig rules, modified by Wiley, permit a preliminary phylogeny and classification of the Annelida to be made by hand. An error in earlier versions suggested that the Dorydrilidae lacked prostate glands, and this is corrected.     

Some new species of Haplotaxidae (Oligochaeta) from Guinea and remarks on the history of the family

Three new species of Haplotaxidae collected by Dr. A. Villiers in a cave near Kindia, Guinea, are described. One species belongs to the genus Metataxis Righi, 1985 (M. carnivorus sp. nov.) which is distributed in Western Africa and Eastern America. Another new species is similar to Lycodrilus kraepelini Michaelsen, 1914 incertae sedis: a new genus Villiersia is proposed for both species (V. guanivora sp. nov., V. kraepelini nov. comb.).A third species, of which only immature specimens are available, is tentatively attributed to the genus Haplotaxis: it is remarkable because of its peculiar setae and commissural vessels (H. villiersi sp. nov.).The three species appear to feed on bat guano and, occasionally, on aquatic arthropods. Metataxis, Tiguassu and Villiersia belong to the section of Haplotaxidae endowed with paired sperm sacs and ovisacs.The relations of Haplotaxidae with other families are discussed and it is suggested that the passage from the haplotaxid condition to that of sparganophilids and more advanced lumbriciforms is connected to a change of reproductive strategy and to an enhanced metabolism.     

Elektronenmikroskopische Untersuchung eines Mechanorezeptors von Evertebraten (Priapuliden,Oligochaeten)

Zusammenfassung Rezeptoren von Priapulus caudatus und Rhynchelmis limosella werden elektronenmikroskopisch untersucht. Ihre Strukturen stimmen in folgenden Merkmalen überein: Apikal steht eine Zilie, die von regelmäßig angeordneten Mikrovilli umgeben wird. Das Cytoplasma der Mikrovilli ist zentral verdichtet und im übrigen Bereich von Filamenten ausgefüllt, die im Perikaryon wurzeln. Im distalen Teil der Zelle liegt ein reich entwickeltes glattes E. R., darunter folgen Tubuli. Die Zellen werden reich innerviert.Aufgrund der strukturellen Übereinstimmung mit Mechanorezeptoren anderer Tiergruppen wird den Rezeptoren der untersuchten Formen ebenfalls eine mechanorezeptive Funktion zugeschrieben.

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Electron microscopic observations on a mechanoreceptor of invertebrates (Priapulida, Oligochaeta)

Summary Epidermal receptor cells of Priapulus caudatus and Rhynchelmis limosella have been investigated with the electron microscope. The following structural peculiarities characterize these cells: an apical cilium is surrounded by regularly arranged microvilli, which contain filaments extending into the cytoplasm of the cell body. The central part of the microvilli is electron dense. The apical part of the cell contains abundant tubules of smooth E. R., below which microtubules are located. The cells are richly innervated.These elements are interpreted to represent mechanoreceptors because they have the above mentioned structures in common with mechanoreceptors of other invertebrate groups.

Für die Überlassung eines Arbeitsplatzes im Anatomischen Institut und im Institut für Pharmakognosie Kiel danken wir Herrn Prof. Dr. W. Bargmann und Herrn Prof. Dr. O. Moritz.     

Dispersal ability rather than ecological tolerance drives differences in range size between lentic and lotic water beetles (Coleoptera: Hydrophilidae)

Aim In aquatic ecosystems, standing (lentic) and running (lotic) waters differ fundamentally in their stability and persistence, shaping the comparative population genetic structure, geographical range size and speciation rates of lentic versus lotic lineages. While the drivers of this pattern remain incompletely understood, the suite of traits making up the ability of a species to establish new populations is instrumental in determining such differences. Here we explore the degree to which the association between habitat type and geographical range size results from differences in dispersal ability or fundamental niche breadth in the members of the Enochrus bicolor complex, an aquatic beetle clade with species across the lentic–lotic divide. Location Western Mediterranean, with a special focus on North Africa, the Iberian Peninsula and Sicily. Methods DNA sequences for four loci were obtained from species of the E. bicolor complex and analysed using phylogenetic inference. Dispersal and establishment abilities were assessed in lentic–lotic species pairs of the complex, using flight wing morphometrics and thermal tolerance ranges as surrogates, respectively. Results There were clear differences in range size between the lotic and lentic taxa of the complex, which appears to have had a lotic origin with two transitions to standing waters. Only small differences were observed in temperature tolerance and acclimation ability between the two lotic–lentic sister species studied. By contrast, wing morphometrics revealed clear, consistent differences between lotic and lentic Enochrus species pairs, the latter having a higher dispersal capacity. Main conclusions We hypothesize that there have been two habitat shifts from lotic to lentic waters, which have allowed marked expansions in geographical range size in western Mediterranean species of the E. bicolor complex. Differences in dispersal rather than in establishment ability appear to underlie differences in geographical range extent, as transitions to lentic waters were associated with changes in wing morphology, but not in thermal tolerance range. In this lineage of water beetles, selection for dispersal in geologically short‐lived lentic systems has driven the evolution of larger range sizes in lentic taxa compared with those of their lotic relatives.     

Estimating linear temporal trends from aggregated environmental monitoring data

Trend estimates are often used as part of environmental monitoring programs. These trends inform managers (e.g., are desired species increasing or undesired species decreasing?). Data collected from environmental monitoring programs is often aggregated (i.e., averaged), which confounds sampling and process variation. State-space models allow sampling variation and process variations to be separated. We used simulated time-series to compare linear trend estimations from three state-space models, a simple linear regression model, and an auto-regressive model. We also compared the performance of these five models to estimate trends from a long term monitoring program. We specifically estimated trends for two species of fish and four species of aquatic vegetation from the Upper Mississippi River system. We found that the simple linear regression had the best performance of all the given models because it was best able to recover parameters and had consistent numerical convergence. Conversely, the simple linear regression did the worst job estimating populations in a given year. The state-space models did not estimate trends well, but estimated population sizes best when the models converged. We found that a simple linear regression performed better than more complex autoregression and state-space models when used to analyze aggregated environmental monitoring data.     

Twenty-one new microsatellite markers for the ecologically important midge Heterotrissocladius marcidus,and their use in studies of alpine lakes

Heterotrissocladius marcidus (Walker, 1856) (Diptera: Chironomidae) inhabits aquatic habitats across the Holarctic and Oriental regions, including remote alpine glacial lakes. It is thus a promising species for studies of population structure and genetic diversity in these highly vulnerable habitats. Here, 21 polymorphic microsatellites for H. marcidus are described, obtained using 454 GS-FLX pyrosequencing. The number of alleles per locus varied from 2 to 9 and no significant linkage disequilibrium was observed. To test applicability, 40 individuals were used from two lakes in the Tatra Mts (Western Carpathians). Observed and expected heterozygosity varied from 0 to 0.9 and 0.102 to 0.888, respectively. In both populations, three loci deviated significantly from Hardy–Weinberg equilibrium after Bonferroni correction, probably due to presence of null alleles or undetected biological processes. Application of microsatellites was tested on six alpine lake populations. Bayesian cluster analysis assigned individuals to lakes of their origin and revealed limited gene-flow between them. Five loci were successfully cross-amplified in the related midge Macropelopia sp. (Tanypodinae) and two in Pseudodiamesa branickii (Nowicki, 1873) (Diamesinae). The microsatellites described herein proved to be useful for genetic studies of alpine populations, and can provide important data for management and conservation of these threatened habitats.