The protegulum and juvenile shell of a Recent articulate brachiopod: patterns of growth and chemical composition

Patterns of shell formation and the chemical composition of the shell deposited during early post-larval life were investigated in laboratory-reared cultures of the Recent articulate brachiopod Terebraralia transversa (Sowerby). A non-hinged protegulum averaging 148 pm in length is secreted by the mantle within a day after larval metamorphosis. The inner surface of the protegulum exhibits finely granular, non-fibrous material. A rudimentary periostracum constitutes the outer layer of the primordial shell. and concentrically arranged growth lines are lacking. By four days post-metamorphosis, a brephic type of juvenile shell develops from periodic additions of shell material to the anterior and lateral edges of the protegulum. Imbricated secondary fibers occur throughout the inner layer of the newly formed juvenile shell, and a rudimentary hinge apparatus is present posteriorly. The external surface of the shell exhibits concentric growth lines anterior to the caudally situated protegulum, and unbranched punctae begin to form in the subperiostracal region of the shell. At 23 days post-metamorphosis, the shell weighs an average of 1.7 μg and measures 318 μm in length. Electron microprobe analyses reveal that the protegulum is calcified. Minor amounts of sulfur, magnesium, iron, chlorine, aluminum, and silicon are also present in protegula and juvenile shells. Based on electron diffraction data, the mineral phase of juvenile shells consists of calcite, and protegula also appear to contain calcite.     

Alterations in the fine structure of cytoplasmic organelles in the hepatopancreatic cells of shell-regenerating snail,Helix pomatia L.

Summary The investigation of hepatopancreatic cells following damage to the shell revealed hypertrophic alterations of several Cytoplasmic organelles. The network of endoplasmic reticulum was extensively developed within both digestive and calcium cells. The arrangement of tubules exhibited a peculiar hexagonal pattern. It is suggested that the reticulum is of agranular type and may be engaged in the transport of lipids and calcium ions. Remarkable alterations were observed in mitochondria, apparently as the result of their hyperfunction. Mitochondria with reduced cristae, with two-layered transverse septum, and with bleb-like protrusions, occurred frequently. In the calcium cells, helically entwined fibres appeared among the fragments of disintegrated calcium spherites. The results of the investigation and the possible presence of collagen in the fibres originating from disintegrated spherites are discussed.This investigation was supported by grants from the Swedish Natural Science Research Council, which are gratefully acknowledged. The author wishes to thank Mrs. I. Rehnberg for technical assistance.     

Electroacupuncture inhibits CB1 upregulation induced by ethanol withdrawal in mice

CB1R play a role in alcohol withdrawal and in some effects of acupuncture. Interestingly, acupuncture has been used to alleviate alcohol withdrawal. Here, we investigated electroacupuncture (EA) effects during ethanol withdrawal on CB1R immunoreactivity. Male Swiss mice were daily injected with ethanol (2g/kg, i.p) (EtOH group), for 21 days. EA was performed daily during 4 days of ethanol withdrawal. The stimuli of 2 or 100 Hz were provided in two acupoints combination: Ea1 [(ST-36/Zusanli) and (PC-6/Neiguan)] or Ea2 [(DU-14/Dazhui) and (DU-20/Baihui)]. The specificity of the acupoints were assessed by the inclusion of three additional groups, Ea3 [(ST 25/Tianshu - acupoints used to other non-related disorders)], Sham1 and Sham2 (transdermic stimulation nearly to the respective acupoints). EtOH group were only handled during withdrawal and Saline group was chronically treated with Saline and handled similarly to EtOH group. One day after withdrawal the animals were perfused and their brains processed for immunohistochemistry. There was an increase of CB1R in the prefrontal cortex, striatum, hippocampus, amygdala and ventral tegmental area. The procedures used in the 2HzEa1 and 100HzEa2 groups were the most effective and specific to inhibit this CB1R upregulation. Therefore, EA inhibits CB1R upregulation seen in ethanol withdrawn mice. The specificity of acupoints stimulation depends of the encephalic nuclei, acupoints association and frequency of stimulation.     

大荔人所在层位贝壳的电子自旋共振年龄

大荔人属早期智人中较古老的类型 ,在人类起源研究中具有重要意义。采用电子自旋共振 (ESR)测年技术直接测定了采自大荔人所在层位的 3个贝壳样品的年龄 ,同时 ,进行了铀系测年分析 ,根据贝壳ESR的年龄结果 ,大荔人可能老于距今 250ka。     

Ordovician (Caradoc) Gastropoda of the Katkoyeh Formation, Kerman Province, Iran

Seven taxa of gastropods are described from the Ordovician (Caradoc) upper Katkoyeh Formation of the Kerman region, east-central Iran. Three are named species and four are under open nomenclature. The most abundant is the minute bellerophontiform Tritonophon peeli Horný, 1977, indicative of a shallow water plectonotid community. Shell material is not preserved in this species, but a small, simple bulbous protoconch is present. Two new species are Slehoferia pachyta and Nonorios kleistos, both with prominent thick-shelled conchs. Shell repair is documented in both of these forms, interpreted as a result of failed predation. Other micromorphic species occur in the samples, but only Tropidodiscus sp. and Nonorios? sp. are named. The Kerman assemblage is comparable directly with similar, closely coeval faunas in Bohemia, France, Portugal, Morocco, and Italy, corresponding with the Palaeozoic Mediterranean Province of northern peri-Gondwana.     

Three species of Mytilus and their hybrids identified in a Scottish Loch: natives, relicts and invaders?

Three species of the mussel, Mytilus, occur in the North Atlantic region, M. edulis, M. galloprovincialis and M. trossulus, and hybrid zones are present where their distributions overlap. M. edulis is a native species in the UK. M. galloprovincialis originated in the Mediterranean and its distribution extends northwards along the Atlantic seaboard to Scotland. Baltic Sea mussels have a M. trossulus ancestry but are highly introgressed by M. edulis. In recent decades, farming of mussels on long-line rope culture systems has been introduced into Scotland. On farms in Loch Etive, a form of mussel with a fragile shell and a different shape to either M. edulis or M. galloprovincialis has been increasing in frequency over recent years. Samples of fragile shelled, normal strong shelled and intermediate mussel types were sampled from two farms in 2006 and compared with samples of M. edulis, M. galloprovincialis and M. trossulus from other sources where their species identity is well established. Abundance relative to depth, shell strength, condition index and shell morphology were analysed together with 5 allozyme loci and one nuclear DNA genetic marker (Me 15/16). The fragile shelled mussels, and many of those classed as intermediate, were identified as a mixture of M. trossulus and M. trossulus x M. edulis hybrids. This identification was strongly supported by both morphological and genetic data and is the first record of the presence of M. trossulus in UK waters. M. trossulus in Loch Etive are most likely to be a post-glacial relict population restricted to the low salinity area of the Loch that has recently increased in abundance due to commercial mussel growing activity. In addition, individual mussels of all three species and their hybrids were detected amongst Loch Etive mussels. This is the first genetic demonstration of all three species and their hybrids occurring together in one location in the Atlantic region and provides a unique opportunity to study the processes of speciation, divergence, and introgression in the genus Mytilus.     

A novel role for dpp in the shaping of bivalve shells revealed in a conserved molluscan developmental program

During the molluscan evolution leading to the bivalves, the single dorsal shell was doubled. To elucidate the molecular developmental basis underlying this prominent morphological transition, we described the cell cleavage and expression patterns of three genes, brachyury, engrailed, and dpp in the Japanese spiny oyster Saccostrea kegaki, and examined the function of dpp in this species. The cleavage pattern of the S. kegaki embryo was nearly the same as the previously described pattern of other bivalve species, suggesting that the pattern itself is highly important for the establishment or the maintenance of the bivalve body plan. The expression pattern of a brachyury homolog in S. kegaki (SkBra) was similar to the pattern in gastopods even at the single cell level despite the deep divergence of gastropods and bivalves. Engrailed and dpp were previously found to be expressed around the shell anlagen in gastropods. Like that of gastropods, an engrailed homolog in S. kegaki (SkEn) was found to be expressed around the shell anlagen. However, the dpp homolog in S. kegaki (SkDpp) was expressed only in the cells along the dorsal midline. ZfBMP4 treatment experiments revealed the importance of dpp in establishing the characteristic shape of the bivalve shell anlagen.     

Characteristics of shell microstructure and growth analysis of the Antarctic bivalve <Emphasis Type="Italic">Laternula elliptica</Emphasis> from Lützow-Holm Bay,Antarctica

Growth performance of the Antarctic bivalve Laternula elliptica was examined both by shell microstructural observation and by applying a fluorescent substance, tetracycline, as a shell growth marker. The shell was composed of two calcareous layers: the thick outer layer was homogeneous or granular in structure and the thin inner layer was nacreous. The architecture of Antarctic L. elliptica was different from that of temperate L. marilina, and the ratio of thickness between the outer and inner layers appeared to be different. The growth rate of the nacreous layer was analyzed to be very low. High correlations were found between the major axis of chondrophore and both shell length and shell dry weight, respectively. It is suggested that the chondrophore is an appropriate growth indicator, and combining the information of growth increments with the fluorescent method may be useful in estimating the bivalve growth performance in the Antarctic sea.     

The shell matrix of the pulmonate land snail Helix aspersa maxima

In mollusks, the shell mineralization process is controlled by an array of proteins, glycoproteins and polysaccharides that collectively constitute the shell matrix. In spite of numerous researches, the shell protein content of a limited number of model species has been investigated. This paper presents biochemical data on the common edible land snail Helix aspersa maxima, a model organism for ecotoxicological purposes, which has however been poorly investigated from a biomineralization viewpoint. The shell matrix of this species was extracted and analyzed biochemically for functional in vitro inhibition assay, for amino acid and monosaccharides compositions. The matrix was further analyzed on 1 and 2D gels and short partial protein sequences were obtained from 2D gel spots. Serological comparisons were established with a set of heterologous antibodies, two of which were subsequently used for subsequent immunogold localization of matrix components. Our data suggest that the shell matrix of Helix aspersa maxima may differ widely from the shell secretory repertoire of the marine mollusks studied so far, such as the gastropod Haliotis or the pearl oyster Pinctada. In particular, most of the biochemical properties generally attributed to soluble shell matrices, such as calcium-binding capability, or the capacity to interfere in vitro with the precipitation of calcium carbonate or to inhibit the precipitation of calcium carbonate, were not recorded with this matrix. This drastic change in the biochemical properties of the landsnail shell matrix puts into question the existence of a unique molecular model for molluscan shell formation, and may be related to terrestrialisation.