Waltraud Klepal

Bio: Waltraud Klepal is an academic researcher from University of Vienna. The author has contributed to research in topics: Idiosepius & Siboglinidae. The author has an hindex of 18, co-authored 54 publications receiving 775 citations.

Mechanisms of cadmium toxicity in terrestrial pulmonates: Programmed cell death and metallothionein overload

Abstract: A sublethal dose of cadmium (Cd 2+ ) administered via the diet during short-term exposure over 10 d induced programmed cell death in the hepalopancreas of the terrestrial pulmonate snail Helix pomatia. Condensed cell residues were predominantly phagocytosed by calcium cells, suggesting a specific function of these epithelial cells in metal detoxification or in clearing the organ of cellular debris from cell death. The considerable cell loss recorded by histological analysis was accompanied by enhanced cell proliferation. Intoxication with Cd was further associated with the pronounced abundance of residual bodies, predominantly recorded in excretory cells, and with pathological changes in the endoplasmic reticulum. During long-term Cd exposure, mortality increased with increasing Cd concentrations in the diet, as demonstrated by feeding experiments in the laboratory. Lethal effects of Cd appeared to he correlated with Cd overloading of the Cd-specific metallothionein isoform (Cd-MT), isolated and characterized previously from the animal's hepatopancreas. Stoichiometrie analysis shows that the capacity of Cd-MT to bind six molar equivalents of Cd corresponds to a tissue Cd concentration of approximately 4 μmol/g dry weight. At this tissue concentration, all high-affinity metal-binding sites of Cd-MT are occupied by Cd 2+ . Cadmium exposure beyond this level gives rise to progressive destabilization of Cd-MT cluster structure in votro, resulting in increasing proportions of weakly bound, or even unbound, Cd 2+ ions. Our results suggest that in vivo, the observed overburdening of Cd-MT with Cd 2+ reduces the viability of affected animals.

Mechanisms of Adhesion in Adult Barnacles

Abstract: Barnacles belong to the phylum Crustacea (following the taxonomy of Newman, 1987), which makes them segmented animals with jointed limbs, an exoskeleton that periodically moults, and a complex lifecycle involving metamorphosis between larval and adult forms. The group of crustaceans to which barnacles belong, the Cirripedia, has a unique larval form — the cyprid. This life history stage is adapted to locate a spot on which to permanently settle, develop, grow, and survive for the rest of its life. Barnacles have a worldwide distribution and various lifestyles, from parasitic species on the gills of decapod crustaceans to free-living groups. The free-living groups are adapted to permanently attach via cement onto other living organisms, rocks or man-made materials, and barnacle “fouling” on marine installations and cargo ships is increasingly of economic concern (Adamson and Brown, 2002). Within the free-living barnacles, a further division is recognized between acorn (Order Sessilia) and stalked (Order Pedunculata) forms. Certain stalked species are termed “pleustonic” due to a lifestyle at the air/water interface (see Bainbridge and Roskell, 1966) and these are the species which will be emphasized in this chapter (Fig.9.1A-C). Open image in new window Fig.9.1 (A) Lepas anatifera showing capitulum (cap) and peduncle (p), scale bar 1 cm; (B) pleustonic species L. Anatifera attached to glass and Dosima fascicularis with glue fl oat; (C) D. Fascicularis with fl oat (f), scale bar 1 cm; (D) transverse section of peduncle in L. Anatifera stained using AZAN (Kiernan, 1999) showing position of the cuticle lining of the peduncle (c), circular and longitudinal muscle layers (mu), ovarioles (o), hemocoelic space (h) and glue gland cells (g), scale bar 500 µm; (E) schematic of glue apparatus in L. Anatifera including the position of the ovarioles/glue glands (o/g) in the peduncle and principal canal (pc); (F) schematic of detailed glue glands in L. Anatifera including mature cement gland (mcg), young cement gland (ycg), lumen (lu) of the principal canal, vacuole (vac), collector canal (cc), secondary canal (sc), intracellular canal (ic), large nucleus with numerous nucleoli (n). Schematic in B is reproduced with permission from Ankel (1962) and drawings in E and F are reprinted with permission of Lacombe and Liguori (1969)

Unusual adhesive production system in the barnacle Lepas anatifera: an ultrastructural and histochemical investigation.

Abstract: Adhesives that are naturally produced by marine organisms are potential sources of inspiration in the search for medical adhesives. Investigations of barnacle adhesives are at an early stage but it is becoming obvious that barnacles utilize a unique adhe- sive system compared to other marine organisms. The current study examined the fine structure and chemis- try of the glandular system that produces the adhesive of the barnacle Lepas anatifera. All components for the glue originated from large single-cell glands (70-180 lm). Staining (including immunostaining) showed that L-3,4-dihydroxyphenylalanine and phosphoserine were not present in the glue producing tissues, demonstrat- ing that the molecular adhesion of barnacles differs from all other permanently gluing marine animals studied to date. The glandular tissue and adhesive secretion primarily consisted of slightly acidic proteins but also included some carbohydrate. Adhesive proteins were stored in cytoplasmic granules adjacent to an in- tracellular drainage canal (ICC); observations impli- cated both merocrine and apocrine mechanisms in the transport of the secretion from the cell cytoplasm to the ICC. Inside the ICC, the secretion was no longer con- tained within granules but was a flocculent material which became ''clumped'' as it traveled through the canal network. Hemocytes were not seen within the ad- hesive ''apparatus'' (comprising of the glue producing cells and drainage canals), nor was there any structural mechanism by which additions such as hemocytes could be made to the secretion. The unicellular adhesive gland in barnacles is distinct from multicellular adhe- sive systems observed in marine animals such as mus- sels and tubeworms. Because the various components are not physically separated in the apparatus, the bar- nacle adhesive system appears to utilize completely dif- ferent and unknown mechanisms for maintaining the liquid state of the glue within the body, as well as un- identified mechanisms for the conversion of extruded glue into hard cement. J. Morphol. 000:000-000, 2012. 2012 Wiley Periodicals, Inc.

Adhesive mechanisms in cephalopods: a review

Abstract: Several genera of cephalopods (Nautilus, Sepia, Euprymna and Idiosepius) produce adhesive secretions, which are used for attachment to the substratum, for mating and to capture prey. These adhesive structures are located in different parts of the body, viz. in the digital tentacles (Nautilus), in the ventral surface of the mantle and fourth arm pair (Sepia), in the dorsal epidermis (Euprymna), or in the dorsal mantle side and partly on the fins (Idiosepius). Adhesion in Sepia is induced by suction of dermal structures on the mantle, while for Nautilus, Euprymna and Idiosepius adhesion is probably achieved by chemical substances. Histochemical studies indicate that in Nautilus and Idiosepius secretory cells that appear to be involved in adhesion stain for carbohydrates and protein, whilst in Euprymna only carbohydrates are detectable. De-adhesion is either achieved by muscle contraction of the tentacles and mantle (Nautilus and Sepia) or by secretion of substances (Euprymna). The de-adhesive mecha...

Biodiversity of the Mediterranean Sea: estimates, patterns and threats

Abstract: Trabajo presentado en el 39th CIESM Congress, celebrado en Venecia, Italia, del 10 al 14 de mayo de 2010

The Biodiversity of the Mediterranean Sea: Estimates, Patterns, and Threats

Abstract: The Mediterranean Sea is a marine biodiversity hot spot. Here we combined an extensive literature analysis with expert opinions to update publicly available estimates of major taxa in this marine ecosystem and to revise and update several species lists. We also assessed overall spatial and temporal patterns of species diversity and identified major changes and threats. Our results listed approximately 17,000 marine species occurring in the Mediterranean Sea. However, our estimates of marine diversity are still incomplete as yet—undescribed species will be added in the future. Diversity for microbes is substantially underestimated, and the deep-sea areas and portions of the southern and eastern region are still poorly known. In addition, the invasion of alien species is a crucial factor that will continue to change the biodiversity of the Mediterranean, mainly in its eastern basin that can spread rapidly northwards and westwards due to the warming of the Mediterranean Sea. Spatial patterns showed a general decrease in biodiversity from northwestern to southeastern regions following a gradient of production, with some exceptions and caution due to gaps in our knowledge of the biota along the southern and eastern rims. Biodiversity was also generally higher in coastal areas and continental shelves, and decreases with depth. Temporal trends indicated that overexploitation and habitat loss have been the main human drivers of historical changes in biodiversity. At present, habitat loss and degradation, followed by fishing impacts, pollution, climate change, eutrophication, and the establishment of alien species are the most important threats and affect the greatest number of taxonomic groups. All these impacts are expected to grow in importance in the future, especially climate change and habitat degradation. The spatial identification of hot spots highlighted the ecological importance of most of the western Mediterranean shelves (and in particular, the Strait of Gibraltar and the adjacent Alboran Sea), western African coast, the Adriatic, and the Aegean Sea, which show high concentrations of endangered, threatened, or vulnerable species. The Levantine Basin, severely impacted by the invasion of species, is endangered as well. This abstract has been translated to other languages (File S1).

Ecological Causes for the Evolution of Sexual Dimorphism: A Review of the Evidence

Abstract: Can sexual dimorphism evolve because of ecological differences between the sexes? Although several examples of this phenomenon are well known from studies on birds, the idea has often been dismissed as lacking general applicability. This dismissal does not stem from contradictory data so much as from the difficulties inherent in testing the hypothesis, and its apparent lack of parsimony, in comparison to the alternative explanation of sexual selection. The only unequivocal evidence for the evolution of sexual dimorphism through intersexual niche partitioning would be disproportionate dimorphism in trophic structures (e.g., mouthparts). This criterion offers a minimum estimate of the importance of ecological causes for dimorphism, because it may fail to identify most cases. A review of published literature reveals examples of sexually dimorphic trophic structures in most animal phyla. Many of these examples seem to be attributable to sexual selection, but others reflect adaptations for niche divergence between the sexes. For example, dwarf non-feeding males without functional mouthparts have evolved independently in many taxa. In other cases, males and females differ in trophic structures apparently because of differences in diets. Such divergence may often reflect specific nutritional requirements for reproduction in females, or extreme (sexually selected?) differences between males and females in habitats or body sizes. Ecological competition between the sexes may be responsible for intersexual niche divergence in some cases, but the independent evolution of foraging specializations by each sex may be of more general importance. If ecological causation for dimorphism can be demonstrated in so many cases, despite the inadequacies of the available criteria, the degree of sexual size dimorphism in many other animal species may well also have been influenced by ecological factors. Hence, it may be premature to dismiss this hypothesis, despite the difficulty of testing it.

Histochemistry, Theoretical and Applied.

Abstract: municable disease control to the newer responsibilities of the hazards of ionizing radiation and medical defense against atomic attack. The individual topics are adequately developed with emphasis, in the majority, on brevity of presentation rather than complete and exhaustive detail. References are listed after each chapter for the reader desiring more definitive information. \"Epidemiologic Methods and Inferences\" by Dr. Dienfeld and \"Official and Voluntary Health Agencies\" by Dr. Hilleboe are two chapters which offer especially well-organized, succinct, and effective discussions of their respective subjects. The editors state in their preface that they are presenting \". . a new way to look at preventive medicine for the medical students, general practitioners, specialists, and professional workers in official and voluntary health agencies.\" In the opinion of the reviewer, the authors have achieved their purpose by editing a book which is more an introductory text than a reference tome.