Waltraud Klepal

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

A sublethal dose of cadmium (Cd2+) administered via the diet during short-term exposure over 10 d induced programmed cell death in the hepatopancreas 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 be correlated with Cd overloading of the Cd-specific metallothionein isoform (Cd-MT), isolated and characterized previously from the animals hepatopancreas. Stoichiometric analysis shows that the capacity of Cd-MT to bind six molar equivalents of Cd corresponds to a tissue Cd concentration of approximately 4 micromol/g dry weight. At this tissue concentration, all high-affinity metal-binding sites of Cd-MT are occupied by Cd2+. Cadmium exposure beyond this level gives rise to progressive destabilization of Cd-MT cluster structure in vitro, resulting in increasing proportions of weakly bound, or even unbound, Cd2+ ions. Our results suggest that in vivo, the observed overburdening of Cd-MT with Cd2+ reduces the viability of affected animals.

Unusual Adhesive Production System in the Barnacle Lepas anatifera: An Ultrastructural and Histochemical Investigation

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 adhesive system compared to other marine organisms. The current study examined the fine structure and chemistry 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 μm). Staining (including immunostaining) showed that L‐3,4‐dihydroxyphenylalanine and phosphoserine were not present in the glue producing tissues, demonstrating 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 intracellular drainage canal (ICC); observations implicated 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 contained within granules but was a flocculent material which became “clumped” as it traveled through the canal network. Hemocytes were not seen within the adhesive “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 adhesive systems observed in marine animals such as mussels and tubeworms. Because the various components are not physically separated in the apparatus, the barnacle adhesive system appears to utilize completely different and unknown mechanisms for maintaining the liquid state of the glue within the body, as well as unidentified mechanisms for the conversion of extruded glue into hard cement. J. Morphol., 2012.

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 mechanism used by Idiosepius remains unknown.

The Osedax Trophosome: Organization and Ultrastructure

The polychaete family Siboglinidae, which is currently construed as comprising the Frenulata, Monilifera (composed of Sclerolinum), Vestimentifera, and Osedax, has become known for its specialized symbiont-housing organ called the trophosome. This organ replaced the digestive system of the worms and is located in the elongated trunk region in Frenulata, Sclerolinum, and Vestimentifera. Currently two types of trophosomes have been described: in the taxa Frenulata and Sclerolinum the bacteriocytes originate from endoderm, and in Vestimentifera they originate from mesoderm. In Osedax, a trophosome was described as lacking (Rouse et al., 2004), but bacteriocytes are located in Osedaxs characteristic root tissue. Here, we argue for a consistent name for the symbiont-housing tissue, namely trophosome, as in other siboglinids. In this study we provide morphological evidence that in Osedax the bacteriocytes are derived from somatic mesoderm. We show that the trophosome in Osedax is an apolar tissue composed of bacteriocytes and nonsymbiotic cells. As in vestimentiferans, a specific cell cycle was identified; however, in this case it is directed from the posterior to the anterior end of the worms instead of from the center toward the periphery. Comparison of all siboglinid trophosomes and re-evaluation of their body regions allows us to discuss whether the trophosomes are homologous and to hypothesize about the organization of the last common ancestor of Siboglinidae.

Morphology and Differentiation of Non-sensory Cuticular Structures in Mysidacea, Cumacea and Tanaidacea (Crustacea, Peracarida)

The non‐sensory cuticular structures of some peracarideans (Mysidacea, Cumacea, Tanaidacea) were examined by scanning electron microscopy. The various types of structures present in the adult specimens are listed and the relation amongst them is elucidated. Three ways of differentiation of the structures can be distinguished: 1) a differentiation in the complexity of the structures themselves, 2) a differentiation of their arrangement on the body. 3) a differentiation of their distribution on the various parts of the body. A highly differentiated type of arrangement (row) of a number of simple structures (e.g. teeth) may lead to a higher complex structure (comb), which is seen to be developed best on special regions of the body (e.g. the distal segments of thoracic legs). The function of the cuticular structures–by analogy with other taxonomic groups–is discussed.

Phototaxis in stage i nauplius larvae of two cirripedes

Abstract The positive phototaxis of newly hatched, dark-adapted nauplius larvae, stage I, of Balanus balanoides (L.) and Elminius modestus Darwin has been investigated using interference filters with a narrow band transmission. The spectral sensitivity curve expressed in reciprocal μW cm 2 required to give positive phototaxis shows a maximum between 520 and 530 nm and a marked shoulder at the shorter wavelengths. The number of photons/eye for threshold response has been calculated.

Mechanisms of Adhesion in Adult Barnacles

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)

Ultrastructure of the epidermis and cuticle during the moult-intermoult cycle in two species of adult barnacles☆

Abstract This work deals with the epidermal-cuticular events during the moult-intermoult cycle in two species of adult barnacle, Balanus balanoides (L.) and B. eburneus Darwin. Apolysis. epicuticle formation, early and late procuticle formation are described. During reproductive anecdysis that may last for 6 to 8 wk in B. balanoides the epidermis remains in the intermoult-apolysis stage. Some characteristics of this stage are also described. Variation in stage, ranging from intermoult to early procuticle formation, may be encountered in different epidermal regions in the same organism. This situation makes it impractical to identify an entire organism with a narrowly-defined stage of the moulting cycle. Several kinds of vesicles are observed in the epidermal cell during different portions of the moultintermoult cycle; their possible significance is discussed.

The morphology and histology of the cirripede pemis

The general morphology and detailed histology of the penis of two common boreo-arctic cirripedes, Balanus balanoides (L.) and B. balanus (L.) have been investigated. The penis is a highly extensible, annulated organ beset with four rows of sensory setae. The paired vesiculae seminales unite within the pedicel of the penis to give the single ductus. Distally, the exoskeleton is invaginated into this ductus. Circular muscles are present in the vesiculae seminales but do not continue into the penis. The histology of the ductus epithelium indicates a secretory nature as does that of a specialized group of cells, termed the ‘cushion’, towards the distal end: this group of cells is surrounded by circular muscle bands. Longitudinal muscles extend virtually the whole length of the penis; they give off fibres which are inserted at the junctions of the annulations. The muscles of the pedicel are described. Paired nerves in the pedicel give rise to four in the penis. The sensory innervation of the setae is described. The possible functional relations of the structure to the activities of the penis at copulation and during the emission of semen is discussed.

The organic and inorganic composition of some cirripede shells

Abstract The protein, chitin, calcium, and magnesium present in the shells of several species of cirripedes have been determined; the powdered shell material was also examined by differential thermal analysis (DTA). Chthamalus sp., in which lamina of epicuticular matter are present within the shell, show the greatest organic content. When the organic material is separated into its protein and chitin components the latter is present in similar quantities in all species; this reflects a similar quantity of the chitin-protein matrix. Reduction in the protein content of heavily eroded C. depressus seems to be due to the removal of protein by endolithic algae. The Ca Mg ratio increases from extreme hypobiotic to exposed C. depressus. There is a marked correlation between the Ca Mg ratio and the organic content and it is suggested that the magnesium is largely associated with protein rather than with the calcitic lattice. This receives support from the thermal analyses. Small quantities of quartz were detected by X-ray analysis.