欧盟双壳贝类卫生管理体系研究

对欧盟双壳贝类卫生管理体系法规概况、贝类养殖监控体系的内容和特点进行了分析,提出了建立符合中国特色的贝类卫生管理体系的框架：建立包括原料标签在内的可追溯体系;建立中国特色的HACCP体系;建立出口示范基地。     

Membrane potential as the sum of ionic and metabolic components

The resting potential of a molluscan neuron can be separated experimentally into two components: one which depends on ionic gradients and permeabilities in accordance with the Goldman equation, and a second which depends on the electrogenicity of active sodium transport.     

Paramyosin and contraction of catch muscles

The isotonic shortening of glycerol-extracted preparations of molluscan catch muscles is inhibited at pH's and ionic strengths at which extracted paramyosin crystallizes. The isometric tension development is hardly altered under the same conditions. Consequently, the "catch mechanism" is explained on the basis of the crystallization of paramyosin.     

Evolution of paleozoic marine invertebrate communities

Communities of Paleozoic shelf invertebrates underwent varied rates of change in faunal composition. Notable changes took place during Late Devonian-Early Mississippian time and were most noticeable in ofishore brachiopod-dominated communities. Near-shore molluscan communities remained relatively stable throughout the Paleozoic.     

Myosin rod phosphorylation and the catch state of molluscan muscles

"Catch" is a prolonged state of tension in molluscan smooth muscles shown by mechanical measurements to be associated with the level of protein phosphorylation. Myosin isolated from these muscles is unusual in being phosphorylated in the rod portion by an endogenous kinase, like certain nonmuscle myosins. These findings suggest that the myosin rod is a target for phosphorylation and that this reaction may control the transition from catch to relaxation.     

Salicylate: a structure-activity study of its effects on membrane permeability

Salicylate atnd benzoate, and their anlalogs, reversibly increase the membrane potetntial and conductance of identified molluscan neurons by increasing potassium conductance and decreasing chloride conductance. The relative potencies of these compounds were closely correlated with their octanol-water partition coefficients and their pK(a) values.     

Fossil molluscan larvae: a new biostratigraphic tool

Fossil molluscan larvae are less facies dependent and have a wider geographic range than their adult counterparts. They are also easily recovered from cores and small samples. With proper documentation, the study of fossil larvae can considerably enhance the biostratigraphic potential of macrofossils.     

A catastrophic death assemblage and paleoclimatic implications of pliocene seabirds of Florida

A deposit of fossil seabirds from the late Pliocene of Florida includes more than 130 skeletons of an extinct cormorant that is related phylogenetically to Recent species currently restricted to the eastern north Pacific. Evidence suggests the birds died in a single catastrophic event, perhaps a red tide. The fossil cormorant, along with other extinct seabirds and marine mammals, supports molluscan evidence for cold-water upwelling along the Florida Gulf Coast during the Pliocene. A decline in species richness of marine vertebrates throughout the Pliocene of Florida coincides with cessation of upwelling after emergences of the Panamanian Land Bridge.     

我国贝类出口遭遇的技术性贸易壁垒及应对措施

对我国贝类出口欧美遭遇的技术性贸易壁垒进行了分析,研究了欧美发达国家贝类卫生控制体系的现状,提出我国贝类应对技术性贸易壁垒的途径是建立出口贝类养殖加工及卫生控制标准化体系,从贝类养殖、加工到卫生控制3个层面采取组合控制措施,以突破欧美国家的"禁运"。     

Tertiary climatic change in the marginal northeastern pacific ocean

Analysis of distributional patterns of shallow-water molluscan faunas of the middle latitudes of the marginal northeastern Pacific Ocean discloses a sharp reversal during the Miocene of the progressive climatic deterioration. A low point in the Tertiary cooling trend during the Oligocene was followed by climatic warming that culminated during the middle Miocene, as illustrated by a series of zoogeographic profiles.     

Precambrian Mollusc-like Fossils from Inyo County, California

Probable molluscan fossils have been discovered in the Reed Dolomite, White-Inyo Mountain area, Inyo County, California. They consist of small orthoconic shells with relatively large bilaterally symmetrical protoconch-like initial termini. Some individuals have a 'U-shaped" (in transverse section) internal structure. The fossils occur at least 900 meters below the strata containing the earliest known olenellid trilobites and are therefore considered Precambrian.     

Living nautilus embryos: preliminary observations

Nautilus, long recognized as the most primitive living cephalopod, provides insight into molluscan evolution. Despite many attempts, embryos have not been observed until now. This report details the surface morphology and extraembryonic circulatory pattern. It was found that development, as in other extant cephalopods, is direct, without larval stages. There appears to be no embryonic protoconch associated with shell ontogeny.     

Ionic mechanisms of cholinergic excitation in molluscan neurons

Acetylcholine appears to be an excitatory transmitter at synapses on two different types of molluscan nerve cells: the so-called D- and CILDA neurons. The action of this substance is different in the two cases. In D-neurons, this compound increases the permeability of the subsynaptic or somatic membrane to chloride ions, and through a net efflux of this anion, depolarizes the cell. In CILDA neurons, on the other hand, acetylcholine depolarzies the cell by increasing its permeability to sodium ions.     

Species specific effect of acetylcholine on bivalve rectums

The pharmacology of acetylcholine and 5-hydroxytryptamine on the rectums of Katelysia rhytiphora and K. scalarina was found to be similar, in general, to that of other bivalves. However, while acetylcholine causes a fast twitch in the rectum of K. rhytiphora, the activity and tone of the K. scalarina rectum are depressed except at high concentrations of the drug. The two species can be distinguished by these responses, and, therefore, these rectums are useful experimental objects for studying the physiology of molluscan visceral muscle.     

Rostroconchia: a new class of bivalved mollusks

Four Paleozoic bivalved genera are assigned to the new molluscan class Rostroconchia: Eopteria, Euchasma, Conocardium, and Pseudoconocardium. These mollusks have ani uncoiled univalved larval shell; an untorted bivalved adult shell; no hinge teeth, ligament, or adductor muscles; and a fused, almost inflexible. hinge. Rostroconchianis developed separately from the pelecypods through the ribeirioids, but are regarded as more closely related to the Pelecypoda and Scaphopoda than to other known classes of mollusks.     

Membrane permeability: cation selectivity reversibly altered by salicylate

The effect of salicylate on the relative cation permeability of a membrane was investigated in large, identified molluscan neurons, with the use of intracellular recording techniques. Salicylate caused a reversible, dose-dependent decrease in the permeability of rubidium, cesium, sodium, and lithium ions relative to that of potassium ions. The results suggest that the changes in cation selectivity result from the adsorption of salicylate anions to the membrane with a subsequent increase in the density and field strength of anionic sites in the membrane.     

Anaerobiosis and a theory of growth line formation

Microstructural growth increments within the shells of numerous Recent and fossil molluscs are interpreted as reflections of alternating periods of shell deposition and dissolution, occurring during aerobic and anaerobic respiration, respectively. The acidic end products of anaerobic metabolism are neutralized by calcium carbonate from the shell, leaving a relatively insoluble organic residue at the mantle-shell interface. With the return of oxygenated conditions and resumption of aerobic respiration, this organic material is reincorporated within the shell. Inasmuch as metabolic changes are often synchronized with lunar or solar cycles (or both), we are led to the nearly paradoxical conclusion that, as a result of shell destructive processes, a relatively complete and detailed record of both short- and long-term growth is often preserved within the molluscan exoskeleton. Analyses of relationships between ambient oxygen concentrations and shell structural types may eventually prove useful, in paleoecological studies, for determination of dissolved oxygen gradients in Phanerozoic marine environments.     

Peptide regulation of bursting pacemaker activity in a molluscan neurosecretory cell

Vasopressin and related peptides (10(-9) to 10(-6) molar) induced bursting pacemaker potential activity and altered the current-voltage relations of the membrane in a specific molluscan neurosecretory cell. These effects long outlasted the period of application of the peptides. Sensitivity of the cell to these peptides was primarily localized on the axon hillock region. The observed effects do not resemble conductance changes evoked by conventional neurotransmitters, but rather suggest a membrane regulatory role for these peptides, and thus may be indicative of a new form of information transfer in the nervous system.     

Geographic variation in the molluscan recovery from the end-cretaceous extinction

Biotic recovery patterns after the end-Cretaceous mass extinction differ among the molluscan faunas of the North American Gulf Coast, northern Europe, northern Africa, and Pakistan and northern India. In contrast to the Gulf Coast, the other three regions lack a rapid expansion and decline of "bloom taxa" and have lower proportions of invaders early in the recovery phase. The anomalous Gulf Coast patterns, distinct from extratropical Europe and the tropical regions, provide evidence for the biogeographic and macroevolutionary complexity of biotic recoveries and may have implications for present-day biotas.     

Hemocyte-mediated shell mineralization in the eastern oyster

The growth of molluscan shell crystals is usually thought to be initiated from solution by extracellular organic matrix. We report a class of granulocytic hemocytes that may be directly involved in shell crystal production for oysters. On the basis of scanning electron microscopy (SEM) and x-ray microanalysis, these granulocytes contain calcium carbonate crystals, and they increase in abundance relative to other hemocytes following experimentally induced shell regeneration. Hemocytes are observed at the mineralization front using vital fluorescent staining and SEM. Some cells are observed releasing crystals that are subsequently remodeled, thereby at least augmenting matrix-mediated crystal-forming processes in this system.