Morphological studies on the mantle of the fresh-water mussel Amblema (UNIONIDAE): Scanning electron microscopy

The scanning electron microscope has been used to describe the surface morphology of the mantle in mantle-shell preparations from the fresh-water mussel Amblema. In some regions (adductor muscle insertions), the mantle is firmly attached to the shell. In other areas (along the main course of the mantle), transient adhesions between the outer mantle epithelial cells and the nacre appear to temporally further compartmentalize the extrapallial fluid possibly as a prerequisite for the initial crystallization phenomenon. At the mantle edge, as well as at the isthmus, the periostracum was seen to extrude from the periostracal groove. At the siphonal edge, peculiar fingerlike processes were identified; these may represent primitive photoreceptors. The epithelial cells of the outer mantle epithelium are all microvillated whereas those of the inner mantle epithelium are both microvillated and ciliated. Specific differences in surface morphology are described for various regions of the outer mantle epithelium. These may be related to precise regionalized functional differences of this tissue. Several functions of the mantle, in addition to shell formation, and based on its various morphologies, are also discussed.     

A scanning electron microscopic study of the inorganic and organic matrices comprising the mature shell of Amblema, a fresh-water mollusc

The scanning electron microscope has been used to describe the morphology of the mature shell in a fresh-water bivalve. The structure of the organic and inorganic components within the nacre, the myostracum, and the prismatic layer is described. A transitional or intermediate zone, interposed between the prismatic layer and the nacre, was identified. In demineralized samples, the organic component of the nacre was found to consist of parallel matricial sheets interconnected by irregular transverse bridges. The structure of the mineral component of the nacre was found to vary with the method of specimen preparation. With polished-etched samples, brick-like units were seen. When shells were simply broken and fixed in osmium, the layers of nacreous material consisted of fusing rhomboidal crystals of aragonite which demonstrated subconchoidal fractures. On the inner surface of the shell, the rhomboidal crystals showed an apparent spiral growth pattern. The myostracum was characterized by regions of modified nacreous structure consisting of enlarged aragonite crystals with a pyramidal morphology. The peripheral aspect of the muscle scars was characterized by rhomboidal crystals, the latter fusing to form the typical nacreous laminae. The uniqueness of the anterior adductor scar is exemplified by the presence of pores, each pore walled by pyramidal units, for the insertion of adductor fibres. In most regions of the shell, the prismatic layer consisted of one prism unit thickness with a height of approximately 225–250 μm. However, in two specialized regions of the shell, this layer was seen to consist of multiple layers of stacked prisms. The organic matrices of the prismatic layer are arranged in a honeycomb-like arrangement and packed with mineralized spherical subunits.     

Morphological studies on the periostracum of the fresh-water mussel Amblema (uniondae): Light microscopy, transmission electron microscopy, and scanning electron microscopy

The structure of the periostracum in the fresh-water mussel Amblema has been described using light microscopy, transmission elec;ron microscopy, and scanning electron microscopy. The structure and evolutive course of the periostracum was studied along its entire length, from the periostracal groove until it forms the tough outer covering of the shell. At least five structurally and functionally distinct regions were identified. In addition, the periostracum itself was seen to be a multilayered structure consisting of three major layers which are themselves subdivided into minor layers. From these morphological observations, a regulatory role for the various periostracal layers in mineral trapping, nucleation, and the subsequent formation of the prismatic and nacreous layers of the shell can be postulated.     

Light microscopical studies of the acute toxic effects of N-nitrosodimethylamine on the marine mussel, Mytilus edulis

Mussels, Mytilus edulis, exposed to N-nitrosodimethylamine (DMN), 100 mg DMN/liter sea water, exhibited the following tissue responses: Congestion of the larger vessels in the Leydig cell tissue and infiltration of the tissue with numerous hemocytes, well-demarcated lesions composed of hemocytes in the Leydig cell tissue, degeneration of the epithelial lining of the ducts of the digestive diverticula, and congestion of the branchial vessels with numerous hemocytes accompanied by distortion of the cilia and the ciliated columnar epithelium of the gills. Furthermore, deposition of collagen-like material in the walls of the vessels was observed. DMN also induced spawning prior to the normal spawning time.     

Mucilage from a fresh-water red alga of the genus Batrachospermum

The gelatinous polysaccharides of a Batrachospermum species have been extracted from the alga. The major polysaccharide is acidic and has been separated from neutral polysaccharides by chromatography on DEAE-cellulose. The constituent sugars of the acidic polysaccharide include d- and l-galactose, d-mannose, d-xylose, l-rhamnose, d-glucuronic acid, and two O-methyl sugars, which have been characterized as 3-O-methyl-l-rhamnose (l-acofriose and 3-O-methyl-d-galactose. Partial acid hydrolysis of this polysaccharide has given a complex mixture of neutral and acidic oligosaccharides. The two preponderant acidic oligosaccharides contained galactose and glucuronic acid in 1:1 ratio, suggesting the presence of a repeating sequence of these two residues as a major structural feature of the polysaccharide.     

Electron microscope studies on the oocyte of the fresh-water mussel (Anodonta), with special reference to the stalk and mechanism of yolk deposition

An interesting relationship exists between the ovary and the developing oocyte in the fresh-water mussel. As the oocytes grow, they elongate and bulge into the ovarian cavity. In the early stages, the nucleus migrates from the attached region (“foot”) to the distal region of the cell. With continued growth and maturation the connection between the proximal “foot” and distal nucleated portion becomes reduced to a narrow stalk. Microtubules appear in the young oocytes as they start to elongate and become packed in the stalks of older oocytes. It is suggested that the microtubules function as supporting structures and possibly also as channels for the transfer of materials from one portion of the oocyte to the other. The fine structure of the oocyte reveals evidence that the developing yolk bodies or spheres are formed, in part at least, by the incorporation of many smaller “precursor yolk vesicles.” These appear in the region of the Golgi complex and are presumed to be derived from the Golgi saccules. The oocyte contains an unusually well developed endoplasmic reticulum whose cisternae are filled with a rather conspicuous material.     

The effect of some pesticides on the rhythmic activity of adductor muscle of fresh-water mussel larvae

The effect of some pesticides on the rhythmic and tonic activity of adductor muscle of fresh-water mussel (Anodonta cygnea) larvae was investigated in short-term experiments. In the examined concentration range, Dimecron-50 does not influence the rhythmic activity of adductor muscles, while high concentrations of Gramoxone (is greater than 1 ml/l), Thimet-10 G (is greater than 5 x 10(-1) g/l) and Hungaria L-7 (is greater than 10(-1) g/l) cause a slight increase in it. These substances also induce a prolonged tonic contraction of a small proportion (10%) of larvae. Hungaria L-7 makes an exception, causing considerable contracture (30%). The concentrations inhibiting the TA activation by 50% are: 6x 10(-1) ml/l Dimecron-50; 2.5 x 10(-1) ml/l Gramoxone; 10(-1) g/l Hungaria L-7 and 8x 10(-2) g/l Thimet-10 G, while the 50% inhibition of the nonspecific ACh activation is resulted by 2 x 10(-1) ml/l D-50. It is concluded that contamination of environmental waters with Dimecron-50, Thimet-10 G or Hungaria L-7 may be injurious also for Pelecypoda larvae, that may contribute to the unbalancing of the water ecosystem.     

Effect of some insecticides on the periodic activity of the fresh-water mussel (Anodonta cygnea L.).

The effect of the insecticides Hungaria L-7, Dimecron-50, Thimet-10 G and Satox 20 WSC containing lindane, phosphamidon, phorate and trichlorfon, respectively, as active ingredient was investigated on the survival and pumping behaviour of the fresh-water mussel Anodonta cygnea L. The shortening of active periods was used as indicator of the sublethal effects. Hungaria L-7, Thimet-10 G and Satox 20 WSC caused significant inhibition of the filtering activity, while Dimecron-50 was less effective. Fifty per cent shortening of active periods required 6 X 10-3 g/l Hungaria L-7, 8 X 10-3 g/l Thimet-10 G and 2 X 10-2 ml/l Satox 20 WSC. Thimet and Satox were lethal at 10-1 g/l and 1 m/l concentrations, respectively. Although the mechanism of the effect can be different with various substances, the results have shown, that monitoring of the activity of mussels can be a suitable test for the biological indications of water pollution.     

Experimental studies on the marine algae Iridaea and Gigartina

Field and laboratory studies of the economically important marine algae Iridaea cordata (Turner) Bory and Gigartina exasperata Harvey & Bailey (Rhodophyta: Gigartinales) have been made in order to establish information essential to the aquaculture of these species. The development of a simple and successful method for experimental transplantation of these species which permits periodic removal, measurement, and photography of the transplanted algae is described and its feasibility for successfully transplanting these algae to habitats in which they do not occur naturally, demonstrated. The growth rates of such transplanted algae and the maximum size which they attain are comparable to those of plants in the population from which the transplanted algae were taken.In field experiments, the optimum depth for maximum growth rates was 3–5 m below M.L.L.W. Laboratory experiments using a crossed-gradients (light and temperature) incubator indicated that optimum growth rates are obtained at temperatures of 10–14 °C and light intensities of 8.9–16.0 × 10³ erg/cm² sec (cool-white fluorescent); such light intensities are substantially higher than the optimum for many of the red algae that have been grown in laboratory culture. These results support the biological feasibility of cultivating these algae in the inland waters of the Pacific Northwest.     

瓦氏黄颡鱼2种寄生车轮虫形态分类

采用国际上使用的"统一特定描述"和"齿体定位描述"方法对寄生在瓦氏黄颡鱼(Peleteobagrusvachelli)鳃上的适度车轮虫(Trichodina modesta)和马氏车轮虫(T.mastu)2种车轮虫的虫体外形、附着盘、齿体、辐线、中央颗粒、核器、口围绕体等形态特征进行了较为详细的描述,并分别与已报道的其他适度车轮虫、马氏车轮虫种群及相似种的形态特征进行了比较。实验证实了瓦氏黄颡鱼为适度车轮虫的寄主新纪录。     

鄱阳湖8种淡水蚌脂肪含量及脂肪酸组成研究

鄱阳湖是我国第一大淡水湖,孕育着丰富的我国淡水双壳类特有种(共17属58种),其中蚌科占67%,达13属39种[1],资源开发潜力巨大.Labieniec[2]、Goff[3]、蔡华芳[4]等对淡水蚌的研究集中于DNA生物制剂或蛋白饲料的开发利用.而国内对淡水蚌的研究多见于三角帆蚌(Hyfiopsis cum-mingii)、褶纹冠蚌(Cristaria plicata)等少量几种珠母贝的育珠研究[4].     

Cryopreservation of the Mediterranean mussel (Mytilus galloprovincialis) spermatozoa

The effects of cryoprotectants, cooling rate and freezing on the mussel Mytilus galloprovincialis sperm were evaluated. At the end of each step of the experimental protocol, motility and fertilization ability of sperm were analyzed, compared to fresh semen. Five cryoprotectants were tested in their toxicity level: dimethylsulfoxide, ethylene glycol, 1-2 propylene glycol at 5%, 7%, 10%, 15% and 20% concentration; glycerol and methanol at concentration of 5%, 7% and 10%. The incubation times were 10, 20 and 30 min at 20 ± 1 °C. Only dimethylsulfoxide, ethylene glycol and 1-2 propylene glycol at 5%, 7% and 10% were chosen for the following pre-freezing step. Five adaptation/chilling rates were analyzed: 10 min at 20 ± 1, −2, −1, −0.5 and −0.25 °C/min and the last one was used for testing the best freezing procedure among seven gradients. Particularly, two rapid rates, three slow rates and two double step rates were conducted.Thawing results showed that M. galloprovincialis sperm are very sensitive to rapid pre-freezing and freezing protocols and only a slow procedure assured good motility and fertilization percentages.     

Electron microscopic autoradiography of serotonin uptake in the ganglia of the fresh-water mussel (Anodonta cygneak L.).

After in vitro incubation, the uptake of labelled serotonin was investigated by electron microscopic autoradiography in the ganglia of fresh-water mussel (Anodonta cygnea L.) The labelled serotonin was primarily taken up by the axons of the neurons. The silver grains could always be localized over axons containing eccentric dense-core vesicles with a diameter of 100--200 nm. The results suggest (a) the possibility of the electron microscopic identification of serotonin-containing neurons, and (b) the direct role of the eccentric dense-core vesicles in the storage of serotonin.