Morphobiochemical Adaptations to the Littoral Environment in Some Atlantic Gastropods

The morphobiochemical adaptations to the drying and feeding of four species of littoral mollusks collected in a confined area of the Atlantic coast have been analyzed: Tectarius striatus, Siphonaria pectinata, Phorcus atratus, and P. sauciatus. It was established that these mollusks differ strongly from each other morphologically and biochemically, thus demonstrating a variety of adaptations to the same environmental conditions. It was noted that T. striatus is the most adapted to live in the tidal zone. It is assumed that the survival of P. atratus and P. sauciatus in the conditions of drying is to some extent maintained by the green pigment (biliverdin) concentrated in the soft tissues, as its quantity increases as the mollusks remain without water.     

Morphobiochemical Adaptations to Life on Littoral in Some Sedentary Gastropods

Adaptations to attachment, respiration, nutrition, and pollution of sedentary gastropods with cowl-shaped shell living in littoral conditions and prone to the influence of abiotic factors are analyzed. Weight properties of individual parts of the radular apparatus related to scrapping mode of nutrition are discussed. The content of hemoglobin in radular tissues of some representatives of Patellidae, Acmaeidae, and Siphonariidae families is comparatively evaluated.     

Ecological Aspects of Some Coral-Boring Gastropods and Bivalves of the Northwestern Red Sea

More than 17 molluscan species were obtained from burrows incoral substrata at Al-Ghardaga (Hurghada on maps) on the RedSea coast, six of which in particular bore into livingcolonies.The species reported in this paper belong to the families Mytilidae,Coralliophilidae, and Gastrochaenidae. The direction of boringin living corals is to the outside, the borers keeping pacewith the growing coral layer to maintain their burrows open.Coral growth is generally of a higher rate than that of borers,and burrows are accordingly mostly much larger than their inhabitants.There is evidence in such cases that burrows form initiallyby growth of coral around the settling young. Boring of Lithophagaspecies is mostly due to the abrasive action of the shell whichmoves straight and posteroventrally without any rotation. Incoralliophilids,boring is also executed mechanically by the turning movementsof the shell. Boring in dead coral is directed inwards, andburrows are nearly as large as the borers. The latter avoidthe blocking of their burrows (e.g., by a living coral incrustation)either by great siphonal extension (Rocellaria) or the freeends of the shell may be strengthened to maintain the capabilityof boring in the opposite direction (Lithophaga laevigata).Both L. luevigata and Modiola chmamomeus bore mainly mechanicallyby the rocking movements of the shell. Chemical boring is stilla possibility,particularly in the posterior narrow region ofburrows of Modiola lodging the extended pallial siphons whichare deprived of any effective mechanical devices for boring.Therole of boring algae in rarefying bored coral material hasalso to be included as an indirect chemical factor.     

Calcium Dynamics in Land Gastropods

In land gastropods, calcium is precipitated in the shell, inconnective calcium cells which are largely distributed throughthe whole connective tissue, in epithelial calcium cells ofthe digestive gland, and in the calcium gland cells of the skinand the mantle collar. Calcium is taken up from the externalmedium by food and by absorption through the sole skin. To adaptto terrestrial life, these animals have to eliminate appreciableamounts of calcium for their protection and their reproduction.During the egg laying period, a calcium flux occurs throughthe epithelium of the reproductive tract in order to supplythe egg shell and the egg fluids. This egg calcium is takenup by the embryo. The maintenance of a positive calcium balancebetween its uptake and the loss is due to an important reservoirof easily mobilizable calcium in the form of calcium carbonate.This reservoir consists of the connective calcium cells whichare constantly able to accumulate or release calcium as longas calcium is locally available or required. The epithelialcalcium cells of the digestive gland are loaded with calciumphosphate; they are not a major calcium storage compartment,but have an essential function in detoxification. All of thecalcium movement occurring across cell membranes and throughepithelia concerns only calcium ions. All calcium movement canbe regarded either as on-off systems or as reversible systems,both of which are certainly controlled by complex processes     

Annotated Checklist of the Terrestrial Gastropods of Nepal

This is the very first checklist of the terrestrial gastropods of Nepal. It includes 138 species and six subspecies, of which 22 species are endemic and four are introduced. It highlights 34 species recorded for the first time in Nepal and provides new distribution records for another 30 species.     

Organic Matrix and Secondary Metabolites in Nacre

Marine Biotechnology - Nacre, also called mother-of-pearl, is a naturally occurring biomineral, largely studied by chemists, structural biologists, and physicists to understand its outstanding and...     

Absorption of Some Amino Acids by Sporophytes Isolated from Polytrichum formosum and Ultrastructural Characteristics of the Haustorium Transfer Cells

The absorption of ¹⁴C-labelled amino acids (glycine, threonineand -aminoisobutyric acid) by the isolated sporophyte of Polytrichumformosum takes place mainly in the haustorium. The isolationof the sporophyte does not alter the absorption capacity ofits haustorium nor its ultrastructure, in particular that ofits peripheral transfer cells. amino acids, transfer cells, sporophyte, Polytrichum formosum, haustorium     

Penetration of the Shell and Feeding on Gastropods by Octopus

The behavior of the octopus when feeding upon shelled molluscsis described in four steps: selection of prey, boring a holein the shell, secreting into the borehole, and pulling out thebody oC the mollusc and eating it. Selection of some gastropodprey is determined by a firm, deep, either partial or completeobstruction in the aperture of the shell. Selection of otherprey, gastropods, pelecypods, and amphineurans, may be basedupon resistance by the mollusc to the application of force bythe octopus. Drilling of the hole is done by the radula. Sincethe octopus will drill and secrete into empty shells with obstructionsin the apertures, metabolites from a live mollusc are unnecessary.This technique can be usedto collect the secretion. The frequencyof occurrence and the eflect of the secretion are discussed.The hypothesis that the octopus first tries by force to pullout the body and, failing to do so, drills a hole in the shellis experimentally supported. The conditions under which the octopus drills or pulls out thebody of the mollusc are incompletely understood. The octopusmay drill two or more shells in succession without feeding uponthe previously drilled and weakened snail. No two steps in thebehavioral sequence are necessarily linked to each other. Thedrilling-feeding patterns are complex and plastic.     

Gastropods of rare families from the Tshegan Formation of Kazakhstan

Eight gastropod species, rare in the Tshegan Formation, are considered. These species and six families, which include these species, were only mentioned in faunal lists of this formation (Amitrov, 1994, 2005). Two new species, Periaulax tsheganica sp. nov. (Trochidae) and Pusillina kazakhstanica sp. nov. (Rissoidae), are described. Other six species of the families Diastomatidae, Marginellidae, Melanellidae, and Mathildidae are figured and compared with related species; their distribution is discussed.     

Heterogeneity of Proteinase Inhibitors in the Water-Soluble Organic Matrix from the Oyster Nacre

We extracted proteinase inhibitors from the nacre of the oyster Pinctada margaritifera with water. Mixing the nacre powder with water for 20 h led to a water-soluble fraction [0.24% (wt/wt) of nacre]. After dialysis of the water-soluble matrix through 6- to 8-kDa and 0.5-kDa membranes, the proteinase inhibitors were divided into low and high molecular weight fractions that contained inhibitors of papain, bovine cathepsin B, and human cathepsin L. We studied the heterogeneity of the inhibitors after separating the low molecular weight fraction according to charge and hydrophobicity. After multistep purification, mass spectrometry analysis revealed that a potent inhibitory fraction contained several molecules. This observation demonstrates the difficulties encountered in attempting to isolate individual metabolites from the complex mixture of molecules present in nacre matrix. Interestingly, the low molecular weight fraction contained specific inhibitors that could discern between cathepsin B and cathepsin L. The nacre organic inhibitors were active against several cysteine proteinases, yet they were more specific in relation to serine proteinases, because only proteinase K was inhibited. These results demonstrate, for the first time, the presence of active proteinase inhibitors in the mollusc shell, and it is possible that these inhibitors may play a role in either protection of proteins involved in shell formation or in defense against parasites, or both.     

Morphofunctional Properties of Nutrition of Certain Predatory Gastropods

Spectra and modes of nutrition as well as morphobiochemical adaptations to nutrition in certain predatory gastropods have been considered. Hemoglobin content in the radular tissues as a function of nutrition mode was assessed.     

Correlated Evolution between Mode of Larval Development and Habitat in Muricid Gastropods

Larval modes of development affect evolutionary processes and influence the distribution of marine invertebrates in the ocean. The decrease in pelagic development toward higher latitudes is one of the patterns of distribution most frequently discussed in marine organisms (Thorson''s rule), which has been related to increased larval mortality associated with long pelagic durations in colder waters. However, the type of substrate occupied by adults has been suggested to influence the generality of the latitudinal patterns in larval development. To help understand how the environment affects the evolution of larval types we evaluated the association between larval development and habitat using gastropods of the Muricidae family as a model group. To achieve this goal, we collected information on latitudinal distribution, sea water temperature, larval development and type of substrate occupied by adults. We constructed a molecular phylogeny for 45 species of muricids to estimate the ancestral character states and to assess the relationship between traits using comparative methods in a Bayesian framework. Our results showed high probability for a common ancestor of the muricids with nonpelagic (and nonfeeding) development, that lived in hard bottoms and cold temperatures. From this ancestor, a pelagic feeding larva evolved three times, and some species shifted to warmer temperatures or sand bottoms. The evolution of larval development was not independent of habitat; the most probable evolutionary route reconstructed in the analysis of correlated evolution showed that type of larval development may change in soft bottoms but in hard bottoms this change is highly unlikely. Lower sea water temperatures were associated with nonpelagic modes of development, supporting Thorson''s rule. We show how environmental pressures can favor a particular mode of larval development or transitions between larval modes and discuss the reacquisition of feeding larva in muricids gastropods.     

Host-Symbiont Relationships in Hydrothermal Vent Gastropods of the Genus Alviniconcha from the Southwest Pacific

Hydrothermal vent gastropods of the genus Alviniconcha are unique among metazoans in their ability to derive their nutrition from chemoautotrophic γ- and -proteobacterial endosymbionts. Although host-symbiont relationships in Alviniconcha gastropods from the Central Indian Ridge in the Indian Ocean and the Mariana Trough in the Western Pacific have been studied extensively, host-symbiont relationships in Alviniconcha gastropods from the Southwest Pacific remain largely unknown. Phylogenetic analysis using mitochondrial cytochrome c oxidase subunit I gene sequences of host gastropods from the Manus, North Fiji, and Lau Back-Arc Basins in the Southwest Pacific has revealed a new host lineage in a Alviniconcha gastropod from the Lau Basin and the occurrence of the host lineage Alviniconcha sp. type 2 in the Manus Basin. Based on 16S rRNA gene sequences of bacterial endosymbionts, two γ-proteobacterial lineages and one -proteobacterial lineage were identified in the present study. The carbon isotopic compositions of the biomass and fatty acids of the gastropod tissues suggest that the γ- and -proteobacterial endosymbionts mediate the Calvin-Benson cycle and the reductive tricarboxylic acid cycle, respectively, for their chemoautotrophic growth. Coupling of the host and symbiont lineages from the three Southwest Pacific basins revealed that each of the Alviniconcha lineages harbors different bacterial endosymbionts belonging to either the γ- or -Proteobacteria. The host specificity exhibited in symbiont selection provides support for the recognition of each of the host lineages as a distinct species. The results from the present study also suggest the possibility that Alviniconcha sp. types 1 and 2 separately inhabit hydrothermal vent sites approximately 120 m apart in the North Fiji Basin and 500 m apart in the Manus Basin.     

Green Fluorescence of Cytaeis Hydroids Living in Association with Nassarius Gastropods in the Red Sea

Green Fluorescent Proteins (GFPs) have been reported from a wide diversity of medusae, but only a few observations of green fluorescence have been reported for hydroid colonies. In this study, we report on fluorescence displayed by hydroid polyps of the genus Cytaeis Eschscholtz, 1829 (Hydrozoa: Anthoathecata: Filifera) found at night time in the southern Red Sea (Saudi Arabia) living on shells of the gastropod Nassarius margaritifer (Dunker, 1847) (Neogastropoda: Buccinoidea: Nassariidae). We examined the fluorescence of these polyps and compare with previously reported data. Intensive green fluorescence with a spectral peak at 518 nm was detected in the hypostome of the Cytaeis polyps, unlike in previous reports that reported fluorescence either in the basal parts of polyps or in other locations on hydroid colonies. These results suggest that fluorescence may be widespread not only in medusae, but also in polyps, and also suggests that the patterns of fluorescence localization can vary in closely related species. The fluorescence of polyps may be potentially useful for field identification of cryptic species and study of geographical distributions of such hydroids and their hosts.     

Osteogenic Potency of Nacre on Human Mesenchymal Stem Cells

Nacre seashell is a natural osteoinductive biomaterial with strong effects on osteoprogenitors, osteoblasts, and osteoclasts during bone tissue formation and morphogenesis. Although nacre has shown, in one study, to induce bridging of new bone across large non-union bone defects in 8 individual human patients, there have been no succeeding human surgical studies to confirm this outstanding potency. But the molecular mechanisms associated with nacre osteoinduction and the influence on bone marrow-derived mesenchymal stem cells (BMSC’s), skeletal stem cells or bone marrow stromal cells remain elusive. In this study we highlight the phenotypic and biochemical effects of Pinctada maxima nacre chips and the global nacre soluble protein matrix (SPM) on primary human bone marrow-derived stromal cells (hBMSCs) in vitro. In static co-culture with nacre chips, the hBMSCs secreted Alkaline phosphatase (ALP) at levels that exceeded bone morphogenetic protein (rhBMP-2) treatment. Concentrated preparation of SPM applied to Stro-1 selected hBMSC’s led to rapid ALP secretions, at concentrations exceeding the untreated controls even in osteogenic conditions. Within 21 days the same population of Stro-1 selected hBMSCs proliferated and secreted collagens I–IV, indicating the premature onset of an osteoblast phenotype. The same SPM was found to promote unselected hBMSC differentiation with osteocalcin detected at 7 days, and proliferation increased at 7 days in a dose-dependent manner. In conclusion, nacre particles and nacre SPM induced the early stages of human bone cell differentiation, indicating that they may be promising soluble factors with osteoinductive capacity in primary human bone cell progenitors such as, hBMSC’s.     

宁夏枸杞异型绒毡层发育的超微结构特点

采用半薄和超薄切片技术对宁夏枸杞(Lycium barbarum L.)异型绒毡层的来源、结构及发育特点进行了研究,结果表明:(1)枸杞异型绒毡层由药隔绒毡层和药壁绒毡层组成,两种绒毡层除了来源、形态及分布位置不同外,其分化、成熟和降解时间,以及细胞质组成、分泌物成分等均有差异.(2)小孢子母细胞期间,药隔绒毡层细胞电子密度大,具有很强的脂质性质,光滑内质网和脂质小泡很丰富;而药壁绒毡层细胞中的核糖体和粗糙内质网较多.四分体后期,两种绒毡层细胞均含有很丰富的核糖体、粗糙内质网和分泌团.减数分裂前,两种绒毡层的细胞壁出现松散并呈絮状.之后,由于不同发育时期绒毡层细胞的不同分泌物在絮状细胞壁中的分布,致使二者的细胞壁都出现了一系列变化.(3)从小孢子早期开始,两种绒毡层细胞的质膜都发生了局部解体.分析推测,在母细胞期间药隔绒毡层具有较高的糖和脂类合成率,药壁绒毡层具有较高的蛋白质类合成率;在四分体后期,药隔绒毡层具有加强胼胝质酶合成和分泌的功能;而两种绒毡层絮状松散的细胞壁和局部解体的质膜有利于绒毡层的较大颗粒分泌物大量、顺利地分泌出绒毡层细胞.     

Ultrastructural Characteristics of Interneuronal Connections of the Central Nervous System of Bivalve Molluscs

Ultrastructure and peculiarities of interneuronal contacts are studied in visceral ganglia of two species of bivalve molluscs, Anadara broughtoni and Mactra sulcatoria. Gap, desmosome-like, symmetrical, and classic synaptic junctions between neuronal bodies and their main processes are described. The major part of interneuronal junctions in the ganglia of the molluscs studied are symmetrical. Complex synaptic complexes formed by specialized and non-specialized junctions are observed.