论晚二叠世的“克氏蛤”

系统评述目前世界上出现的晚二叠世克氏蛤类标本,并描述采自贵州,云南藏东的有关化石１属３种。其中１新属１新种,右壳足丝凹口特征在克氏蛤类研究中具有重要意义。晚二叠世的Ｃｌａｒａｉｏｉｄｅｓ ｇｅｎ．ｎｏｖ．以足丝凹口内端明显向腹方或后腹方扩展膨大成足丝凹湾而不同于早三叠世的Ｃｌａｒａｉａ．后者似由前者演化而来,它们在二叠－三叠系界线附近发生替代,可能与古生代末的绝灭事件相关。     

Predatory blue crabs induce byssal thread production in hooked mussels

Abstract. Blue crabs (Callinectes sapidus) prey on hooked mussels (Ischadium recurvum) growing epizoically on oyster clumps in estuaries along the Louisiana coast. In prey size‐selection experiments, blue crabs preferred small mussels (<30‐mm shell length) to larger mussels, possibly because handling time increased with mussel size. When crabs were given a choice of solitary mussels versus mussels in clumps on oysters in the laboratory, mortality was lower by 86% in clumped mussels. However, no size selection by crabs occurred with mussels in clumps, likely because smaller mussels escaped predation in crevices between larger mussels or oysters. When individuals of two size classes of mussels were exposed to water containing the scent of crabs and of mussels consumed by blue crabs, an increase in byssal thread production was induced in all mussels, but byssal thread production rate was higher for small mussels than for large mussels. We conclude that increased predation risk for small mussels has resulted in higher size‐specific production of byssal threads, and that predator‐induced production of byssal threads, which may increase clumping behavior, may reduce their risk of mortality to predatory blue crabs.     

COMPETITIVE INTERACTIONS BETWEEN THE OPPORTUNISTIC MACROALGAE CLADOPHORA VAGABUNDA (CHLOROPHYTA) AND GRACILARIA TIKVAHIAE (RHODOPHYTA) UNDER EUTROPHIC CONDITIONS1

In a eutrophic embayment (Waquoit Bay, Massachusetts), Cladophora vagabunda (L.) van den Hoek occurs in thick (sometimes > 1 kg dry wt -m^?2), nearly monospecific unattached mats in deeper regions (2 m), whereas Grac-ilaria tikvahiae McLachlan is largely restricted to shallow (<1 m) areas. We explored these distribution patterns, investigating competitive interactions between these opportunistic species by varying the limiting resource, photon flux density (PFD), and species composition under conditions of N sufficiency in microcosms. Under lower biomass loadings, neither species showed a difference in growth rates in single- and mixed-species stands. With a 25% increase in initial biomass loading, Gracilaria tikvahiae had significantly higher growth rates under saturating PFD and consistently showed greater performance when grown in single-species rather than in mixed-species stands. While growth rate was 2×greater for C. vagabunda in single-species than in mixed-species stands at saturating PFD, this pattern was reversed under limiting irradi-ances. In mixed-species stands at high PFD (comparable to shallow regions of the bay), the growth rate of G. tikvahiae was over 4×higher than that of C. vagabunda. Cladophora vagabunda grew at a faster rate than G. tikvahiae only in the low PFD, mixed-species treatment. Results of this study suggest that the observed distributional patterns of these macroalgae are due in part to interspecific exploitative competition but that tolerance of low PFD by C. vagabunda has led to dominance of these species in distinctive regions of the embayment.     

A REVIEW OF THE MACROBENTHIC FAUNA OF THE MHLATHUZE ESTUARY: SETTING THE ECOLOGICAL RESERVE

Summary

This paper reviews historical and current ecological information on macrobenthos from the Mhlathuze Estuary before and after development of the Richards Bay Harbour. The fauna is described in terms of the potential influence of a change in freshwater inflow to the system and the requirements for the setting of an Ecological Reserve. Over 95% of the species recorded were primarily marine and to a lesser extent estuarine in origin. Fauna typical of sheltered, soft-bottomed marine environments inhabited the estuary, whereas estuarine fauna was limited to the canalised sections of the Mhlathuze River. Certain areas were characterised by opportunistic species indicative of disturbed or organically enriched sediments while others sustained a high diversity of more sensitive climax species, several of which are endemic to southern Africa. The majority of species belonged to the Class Polychaeta but the estuarine mudcrab Paratylodiplax blephariskios dominated the benthic biomass. The pre-feasibility stage of the Ecological Reserve Determination indicated that a reduction in freshwater input would negatively impact upon the already reduced estuarine component at the head of the estuary. Conversely, if freshwater flow to the estuary is augmented, sediment transport via the river could increase without there being an. improved catchment management policy in place.     

Does peripheral dislodgement contribute to heterozygote deficiencies in blue mussels?

Differential loss of heterozygous individuals that move to the periphery of mussel aggregations, where they are at greater risk for dislodgement, has been proposed as an explanation for observed heterozygote deficiencies in blue mussels. To test the dislodgement hypothesis, correlations between heterozygosity and mussel motility, as well as characteristics of byssogenesis and byssal thread attachment strengths, were determined in a wild and a farmed population of blue mussels (Mytilus edulis) from New Hampshire, USA. Although both populations exhibited a heterozygote deficit as measured by three microsatellite loci, no relationship was found between heterozygosity and increased motility in either population. Similarly, no relationship was found between heterozygosity and byssogenesis or attachment strength. Hence, differential dislodgement is highly unlikely as a possible contributor to the loss of heterozygous individuals.     

Effects of Environmental Factors on Byssal Thread Formation in Some Members of the Family Mytilidae from the Sea of Japan

The ability to attach repeatedly to a substrate (glass, boulders, sand) in three common mussel species of the upper sublittoral zone of the Sea of Japan, Grayan's mussel Crenomytilus grayanus, the Korean mussel Mytilus coruscus, and northern horse mussel Modiolus modiolus, was studied under experimental conditions. It was found that during 120 h of the experiment C. grayanus and M. modiolus produced more byssal threads than M. coruscus. A decrease in the water temperature from 20 to 0°C slowed the rate of production of byssal threads down to full passivity in some experimental mollusks. This was more typical of M. coruscus and less typical of C. grayanus. Renewed threads differed in their length, thick, size of the adhesive plate, and strength. M. coruscus formed the shortest, thickest, and strongest threads with rather a large adhesive disk. The observed differences are discussed from the position of morphophysiological adaptations of species for colonization of different natural substrata under contrasting conditions of the upper sublittoral zone.     

利用质谱技术结合EST库搜索鉴定厚壳贻贝新型足丝蛋白

贻贝利用足丝粘附于水下各种基质表面.作为一种具有优异粘附性能的生物材料,贻贝足丝蛋白在新型水下粘附剂及表面保护涂层的研制与开发中具有重要的仿生学意义.目前,已报道的贻贝足丝蛋白分子达11种,但是仍然有更多的足丝蛋白分子不为人知.为进一步探讨贻贝足丝蛋白的分子多样性,并从中筛选具有特殊生物学功能的足丝蛋白分子,本文采用鸟枪法-液相色谱-质谱/质谱技术（shotgun-LC-MS/MS）对厚壳贻贝足丝蛋白进行了蛋白质组学分析.将厚壳贻贝足丝分为足丝纤维和足丝盘两部分,每一部分均采用醋酸-尿素溶液,以及醋酸-盐酸胍溶液进行蛋白质抽提;抽提后的足丝蛋白经胰蛋白酶酶解,利用线性离子阱四级杆质谱（LTQ）进行鸟枪法质谱分析.二级质谱图（MS/MS）用以搜索公共数据库中的贻贝表达序列标签（expressed sequence tag,EST）数据库.采用上述方法,获得14种贻贝新型足丝蛋白的高可信度结果及其所匹配的部分或全长cDNA序列;经结构域分析,发现上述新型贻贝足丝蛋白分子的序列中多数包含各种类型的结构域,包括胶原蛋白结构域、C1Q结构域、C1Q结合结构域、微管蛋白辅助折叠结构域、蛋白酶拮抗结构域、VWA结构域、几丁质酶结构域等.在此基础上,对上述新型足丝蛋白在贻贝足丝形成以及粘附方面的功能进行了推测.上述结果对进一步了解贻贝足丝的分子组成以及粘附机理奠定了基础.     

Toxigenic algae and associated phycotoxins in two coastal embayments in the Ebro Delta (NW Mediterranean)

Harmful Algal Bloom (HAB) surveillance is complicated by high diversity of species and associated phycotoxins. Such species-level information on taxonomic affiliations and on cell abundance and toxin content is, however, crucial for effective monitoring, especially of aquaculture and fisheries areas. The aim addressed in this study was to determine putative HAB taxa and related phycotoxins in plankton from aquaculture sites in the Ebro Delta, NW Mediterranean. The comparative geographical distribution of potentially harmful plankton taxa was established by weekly field sampling throughout the water column during late spring–early summer over two years at key stations in Alfacs and Fangar embayments within the Ebro Delta. Core results included not only confirmed identification of HAB taxa that are common for the time period and geographical area, but also provided evidence of potentially new taxa. At least 25 HAB taxa were identified to species level, and an additional six genera were confirmed, by morphological criteria under light microscopy and/or by molecular genetics approaches involving qPCR and next generation DNA pyrosequencing. In particular, new insights were gained by the inclusion of molecular techniques, which focused attention on the HAB genera Alexandrium, Karlodinium, and Pseudo-nitzschia. Noteworthy is the discovery of Azadinium sp., a potentially new HAB species for this area, and Gymnodinium catenatum or Gymnodinium impudicum by means of light microscopy. In addition, significant amounts of the neurotoxin domoic acid (DA) were found for the first time in phytoplankton samples in the Ebro Delta. While the presence of the known DA-producing diatom genus Pseudo-nitzschia was confirmed in corresponding samples, the maximal toxin concentration did not coincide with highest cell abundances of the genus and the responsible species could not be identified. Combined findings of microscopic and molecular detection approaches underline the need for a synoptic strategy for HAB monitoring, which integrates the respective advantages and compensates for limitations of individual methods.     

Dynamics of byssal thread production in <Emphasis Type="Italic">Crenomytilus grayanus</Emphasis> and <Emphasis Type="Italic">Modiolus modiolus</Emphasis> (Bivalvia) upon reattachment to substrate

It was established that the process of repeated attachment to a substrate in bivalve mollusks Crenomytilus grayanus (Grays mussel) and Modiolus modiolus (the northern horse mussel) involved several successive stages which took in vitro about one month at a water temperature of 19 ± 2°C. Comparison with Grays mussel revealed that the northern horse mussel had a higher rate of byssal thread production and a greater thread number by the end of the complete formation of the byssus complex. The observed differences are explained by the adaptation of mollusks to habitation in different biotopes.Original Russian Text Copyright © 2004 by Biologiya Morya, Selin, Vekhova.