Living macromolluscs from a paleo-reef region on the northeastern Venezuelan continental shelf

Drowned reefs, fossil reefs or paleo-reefs, are important ecologically as areas of high biodiversity, foraging, shelter environment, and as areas supporting the spawning aggregations of economically important reef fish species. This is particularly significant when the structures are situated in a wide soft-bottom continental shelf. The presence of limestone structures, fossil reefs and pinnacles dating from circa 8 to 9 ka, to the north of the Paria Peninsula in north-eastern Venezuela, has been known to local fishermen for decades. Using echograms obtained during acoustic fisheries evaluations and the scarce previously available information, an improved location map of hard-bottom structures was made. Benthic samples to study macromolluscs were taken at depths between 54 and 93 m using an unmodified 2-m beam trawl. Four trawl samples were located over fossil reef areas while another four were situated in soft-bottom valleys between limestone structures. Fossil reefs in the area showed a highly patchy distribution. A total of 91 species from 43 Bivalvia, Gastropoda and Scaphopoda families were found, Gastropoda being the dominant class with 49 species. Paleo-reef-covered areas showed higher species richness and only 21% of the species found were common to both substrates. Gastropods Tonna maculosa and Polystira albida were the most abundant species and occurred in both substrate types. Bivalve life habits, a mixture of organism–substrate relationships, shell fixation, mobility and feeding type, differed significantly according to bottom type. Six species are recorded for the first time for eastern Venezuelan waters. Bottom heterogeneity plays an important role in marine ecosystems, providing shelter to fish populations and may be significant as breeding and nursery areas. Its presence in a region with biogeographical interest, situated in the confluence of three major provinces and with oceanographic conditions varying seasonally from upwelling dominated to Orinoco River discharges, makes this the area of interest and it should be evaluated as a possible Marine Protected Area.     

飞云江、鳌江流域的淡水贝类

报告了 １９８４ 年在飞云江、鳌江流域淡水贝类的调查结果。标本经鉴定有 ４９ 种（含未定种 ５种）,其中腹足纲３２ 种（含未定种２ 种）,瓣鳃纲１７ 种（含未定种 ３ 种）。分析了该流域的常见种和偶见种,广生种和狭生种。探讨了该流域淡水贝类的分布区划和经济意义。     

流式细胞术比较研究4种双壳贝类血细胞的分群

应用流式细胞术对太平洋牡蛎(Crassostrea gigas)、海湾扇贝(Argopecten irradians)、虾夷扇贝(Patinopecten yessoensis)和毛蚶(Scapharca subcrenata)4种双壳贝类的血细胞分类进行了比较。根据其血细胞的前向角散射光(FSC)和侧向角散射光(SSC)特性的不同将血细胞分群,FSC和SSC二维图分析发现太平洋牡蛎、海湾扇贝和虾夷扇贝的血细胞都可分为3个亚群,即透明细胞、小颗粒细胞和大颗粒细胞,而毛蚶的血细胞只可区分为透明细胞和颗粒细胞2个亚群。同时还对这4种双壳贝类各种血细胞所占比例进行了比较研究,发现各亚群细胞所占比例差异很大。     

AVAILABILITY OF PHOSPHORUS FROM SELECTED INORGANIC PHOSPHATES TO JUVENILE ABALONE,HALIOTIS DISCUS HANNAI INO.

ＩＮＴＲＯＤＵＣＴＩＯＮＳｔｕｄｉｅｓｏｎｐｈｏｓｐｈｏｒｕｓｍｅｔａｂｏｌｉｓｍｉｎｆａｒｍｅｄｓｐｅｃｉｅｓｈａｖｅｂｅｃｏｍｅａｐｏｐｕｌａｒｒｅｓｅａｒｃｈｓｕｂｊｅｃｔｒｅｃｅｎｔｌｙ ,ｄｕｅｔｏｔｈｅｉｎｃｒｅａｓｅｄｐｕｂｌｉｃｃｏｎｃｅｒｎｏｎｔｈｅｉｍｐａｃｔｏｆｐｈｏｓｐｈｏｒｕｓｄｉｓｃｈａｒｇｅｆｒｏｍｌｉｖｅｓｔｏｃｋａｎｄａｑｕａｃｕｌｔｕｒｅｓｙｓｔｅｍｓｏｎｔｈｅｅｎｖｉｒｏｎｍｅｎｔ (Ｓｋｏｎｂｅｒｇｅｔａｌ.,1 997;ＥｙａａｎｄＬｏｖｅｌｌ,1 997) .Ｐｈｏｓｐｈ…     

Palaeoenvironmental history of the Holocene volcanic crater lake Lago d'Averno (central southern Italy) inferred from aquatic mollusc deposits

The mollusc record from Lago d'Averno, central southern Italy, provides a detailed 1600‐yr record of changes in water quality in response to bradyseismic movements and salinity fluctuations. Bradyseismic vertical land movements and human impact in Roman times led to several transgressions from the Mediterranean Sea, 1 km distant, making the lake a valuable resource for documenting the effect of episodic marine transgressions of a freshwater lake. Low‐oxygen‐tolerant freshwater molluscs suggest that, at around 900–500 bc the lake had a slowly decreasing medium freshwater quality, resulting from contamination of volcanic origin. Disappearance of the obligate freshwater snails and transgression of low‐salinity‐tolerant marine species indicate that, after 500 bc, continuous subsidence resulted in episodic marine transgressions from the nearby sea. The construction of a canal that connected the lake with the sea, in 37 bc, is marked by a considerable increase in the number of shells and by arrival of brackish‐water‐intolerant marine species. Species diversity increased considerably when the area was partly depopulated towards the end of the Roman Empire around ad 400. When the land was slightly uplifted around ad 600–750, the water quality of the lake became less favourable for marine molluscs. Copyright © 2000 John Wiley & Sons, Ltd.     

印太交汇区海洋软体动物生物多样性研究进展

印太交汇区珊瑚礁大三角是全球海洋生物多样性最高的区域,孕育了印度-西太平洋海域接近60％的软体动物种类,同时也有很高比例的特有物种.该海域是全球软体动物生物多样性研究的热点区域.已有不同国家的学者相继对印太交汇区软体动物的多样性、分类与系统演化等方面开展了研究,并取得了一系列重要的成果.基于此,本文从软体动物的生物多样...     

Growth rates of the infaunal bivalve Soletellina alba (Lamarck, 1818) (Bivalvia: Psammobiidae) in an intermittent estuary of southern Australia

Caging and a mark–recapture design were used to estimate the growth rate of the brittle, infaunal bivalve Soletellina alba in the Hopkins River estuary. The growth of both caged and uncaged individuals was monitored at three sites near the mouth of the estuary over 180 days. Growth rates did not differ for caged and uncaged bivalves, or for bivalves subject to different amounts of handling, or between sites. Growth did differ between consecutive time intervals, which was attributable to negligible growth occurring during the colder months of autumn/winter. Comparisons of the condition (as indicated by total mass for length³) of S. alba were inconsistent between sites for caged and uncaged bivalves and for those subject to different amounts of handling. Soletellina alba is a rapidly growing bivalve with mean growth rates for the three time intervals being 0.04±0.002 mm day⁻¹ in summer, 0.02±0.001 mm day⁻¹ in autumn and 0.03±0.001 mm day⁻¹ from summer to winter. Using existing literature, it was shown that a significant relationship exists between maximum shell length and onset of sexual maturity in bivalve molluscs. This relationship predicts that S. alba should reach the onset of sexual maturity at 15.8 mm length. Therefore, it appears that it may be possible for juvenile S. alba (<1 mm) to grow, reach sexual maturity and reproduce in between annual mass-mortality events caused by winter flooding.     

Predation by Octopus vulgaris in the Mediterranean

Abstract. Octopus vulgaris consumes at least 22 molluscan and several crab species in the Mediterranean off the coast of France. Collections of prey discards in octopus middens and in areas inhabited by octopuses revealed that molluscs comprise an estimated 80% of the O. vulguris diet. Octopus predation is probably an important source of mortality for many of these prey species, causing up to 60 % of the mortality within the size ranges sampled. O. vulgaris does not selectively consume particular sizes of its three most important prey species, the bivalves Pilaria chione and Venus verrucosa and the abalone Haliotis tuberculata. Analysis of octopus drill holes on the two bivalve species showed that their locations were nonrandom, whereas the distribution of drill holes in the abalone was not distinguishable from random.     

Population dynamics and fishery management of the paua,Haliotis iris

A population model is developed and used in conjunction with the results of a study of an unexploited population of paua (Haliotis iris Martyn) to examine the historical pattern of recruitment and yield per recruit. As H. iris cannot yet be aged, the population model uses size rather than age classes, but is structurally similar to the Leslie matrix model. Simulations suggest that the observed population size structure resulted from a short (about 5 year) period of high recruitment, preceded and followed by longer periods of low recruitment. Yield per recruit analysis shows that the present minimum legal size for the fishery (127 mm) provides close to the maximum yield per recruit for most stocks, although yield per recruit could be increased in some areas by a reduction in minimum legal size.