Variation in clearance and ingestion rates by larvae of the black-lip pearl oyster (Pinctada margaritifera, L.) feeding on various microalgae

Clearance rate (CR) and ingestion rate (IR) of different sizes (89, 125 and 188 μm shell length) of Pinctada margaritifera larvae were determined when feeding on various microalgae. The microalgae tested were the diatoms, Chaetoceros muelleri and C. simplex, and flagellates, Tahitian Isochrysis aff. galbana, Pavlova lutheri and P. salina at 5 or 10 cells μL^–1. Both CR and IR of microalgae tested in this study increased with increasing larval size; but at all larval sizes, diatoms resulted in lower CR and IR. Of the microalgae tested, P. margaritifera larvae showed greatest CR and IR with the two Pavlova spp. Maximum CR for P. salina was 10.5, 21.2 and 29.7 μL h^–1 for larvae with shell lengths of 89, 125 and 188 μm, respectively. The highest IR values for P. margaritifera larvae with shell lengths of 89, 125 and 188 μm were 8.7, 81.0 and 165.7 cells·larva^–1 h^–1, respectively. CR and IR of P. salina were approximately five times higher than those recorded for C. muelleri and C. simplex.     

Growth and Survival of Blackslip Pearl Oyster Larvae Fed Different Densities of Microalgae

This paper reports on an experiment to determine growth and survival of blacklip pearl oyster, Pinctada margaritifera (L.), larvae fed a 1:1 mixture of Isochrysis aff. galbana clone T-ISO and Pavlova salina at six different densities (1, 2, 5, 10, 20 and 30 × 10³ cells ml^-1. Larval growth and survival were assessed every four days over a 20–day period. Exponential and logistic regression models were fitted to the growth and survival responses, respectively. Overall growth of larvae fed 5 × 10³ cells ml^-1 was significantly greater (p > 0.01) than growth of larvae reared at other algal densities. The optimal food ration for maximum larval growth was 20 × 10³ cells ml^-1, which resulted in larvae with antero-posterior shell length of 230 m after 20 days. These larvae were significantly larger (p > 0.05) than those in all other treatments at the end of the experiment. Survival of larvae fed 0, 1 and 2 × 10³ cells ml^-1 was significantly lower than that of larvae in all other treatments at the end of 15 days (p > 0.01). Maximal survival (8%) over the 20 day period was shown by larvae fed 10 × 10³ cells ml^-1, while lower survival was shown by larvae fed 2 × 10³ cells ml^-1 (2%) and 1 × 10³ cells ml^-1 (0%).     

A protocol for stocking hatchery reared freshwater pearl mussel Margaritifera margaritifera

• 1. Freshwater pearl mussel (Margaritifera margaritifera L.) populations are under serious threat of extinction throughout their geographical range and only a few remnant populations are recruiting to adulthood. Consequently, M. margaritifera is classified as endangered on the International Union for Conservation of Nature Red List.
• 2. Several institutions across many countries have set up Ark sites at hatcheries to culture and rear young M. margaritifera from population remnants, with the intention of stocking these juveniles into rivers. The release location must fulfill the habitat requirements for the full life‐cycle of the species, so they can contribute to the next generation and thus the long‐term recovery of the species. However, little research or advice exists about how to decide if river environments are suitable for stocking.
• 3. A protocol is presented for determining whether a M. margaritifera population will benefit from stocking hatchery reared juveniles and how to identify suitable areas. Stocking locations are considered from catchment scale to microscale using water quality (reach), macrohabitat (site) and microhabitat, including physicochemical properties of the substratum (spots).
• 4. A case study of the River Esk in north‐east England, is incorporated to exemplify the myriad of considerations surrounding attempts to conserve M. margaritifera, and describes how implementation of the protocol can structure and assist stocking programmes. Copyright © 2010 John Wiley & Sons, Ltd.

     

解剖采集的珠母贝精子的激活条件

解剖成熟珠母贝（Pinctada margaritifera)并采集其精子，在不同pH、盐度和温度条件下进行激活实验。结果显示，水温25℃、盐度34、pH8.5以下时，珠母贝精子的激活率与活力均很低，pH9.0-10时激活率与活力均较高，pH9.5时的激活率最高；在水温20℃，盐度34时珠母贝精子只能在pH9.5-10激活，且激活率与活力均比25℃时低。在水温25℃，pH9.5时，精子在盐度10-45能激活，盐度25-35时激活率和活力很高；在水温20℃,pH9.5时，精子只能在盐度20-40时激活。当盐度相同，20℃时的激活率与活力比25℃时低，在pH9.5或10的氨海水中，珠母贝精子在水温5-45℃时能激活，在25-30℃时激活率较高。当温度相同，pH9.5时的激活率比pH10.0时高。解剖得到的珠母贝精子的适宜激活pH9.5、适宜盐度为25-35、适宜温度为25-30℃。     

A critical reflection on the success of rearing and culturing juvenile freshwater mussels with a focus on the endangered freshwater pearl mussel (Margaritifera margaritifera L.)

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The impact of publication on freshwater pearl mussel conservation: To conceal or to reveal the location of threatened habitats?

• 1. The freshwater pearl mussel, Margaritifera margaritifera, is a threatened species. One of the threats faced by this species is direct extermination by poachers, and therefore some researchers conceal information on the locations of pearl mussel habitats. For example, some researchers do not publish the names of the rivers where pearl mussels occur, whereas other researchers do.
• 2. Concealing the names of rivers containing pearl mussels makes them unknown not only to potential offenders but also to administrators, nature conservation practitioners, and ordinary citizens. As a result, no protection measures are undertaken, which is all the more regrettable as damage to pearl mussel habitats can occur accidentally.
• 3. Concealing details of the location of pearl mussel habitats in publications has an adverse impact on the work of specialists, as they do not have access to enough information to study and analyse the biology and distribution of these molluscs.
• 4. One river with pearl mussels in the Gulf of Finland was initially described anonymously (as ‘River B’). Unfortunately, the river was subject to severe human impact, and the largest aggregation of pearl mussels was almost exterminated in the process of constructing a new electric supply line.
• 5. Concealing information on pearl mussel habitats in the Russian section of the Baltic Sea basin was also shown to have been a poor decision. Although the threat from potential poachers was insignificant because of the low commercial value of pearl mussels, the authorities remained uninformed about the existence of valuable habitats.
• 6. The question of whether the locations of pearl mussel habitats should be concealed or revealed in scientific publications does not have an unambiguous answer and should be considered on a case‐to‐case basis; however, the cases for which disclosure is reasonable seem to be more numerous.

     

An alien fish threatens an endangered parasitic bivalve: the relationship between brook trout (Salvelinus fontinalis) and freshwater pearl mussel (Margaritifera margaritifera) in northern Europe

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点纹十二卷的组培与快繁研究

点纹十二卷是一种重要的小型盆栽观赏植物。该文以点纹十二卷叶腋间的健壮幼芽为外植体,对其组培快繁技术进行了研究。结果表明:其最适的分化增殖培养基为MS+6-BA 1.5mg/L+NAA 0.01mg/L;诱导生根培养基为1/2MS+NAA 0.1mg/L+IBA 0.1mg/L。     

Recruitment of the threatened mussel Margaritifera margaritifera in relation to mussel population size,mussel density and host density

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The effects of dietary supplements of polyunsaturated fatty acid on pearl oyster,Pinctada margaritifera L., gonad composition and reproductive output

Black‐lip pearl oyster, Pinctada margaritifera broodstock was collected from the wild. Egg production, hatching rate and larval development were compared between oysters induced to spawn within 2 days after collection in the wild (T1), oysters fed a pure microalgae diet during 24 days before spawning (T2) and oysters fed the same microalgal diet in which 10% of the algae were replaced with 2 μm polyunsaturated fatty acid (PUFA)‐rich microspheres (T3). Administration of lipid microspheres resulted in larger sized eggs, a higher percentage of D‐larvae and larger sized 48‐h‐old larvae (P<0.05). The total and neutral lipid contents of the gonad increased after oysters were fed with microalgae only or with supplementary diet. The major neutral and polar fractions of saturated fatty acid (SFA) were 16C and 18C fatty acids, and not influenced by the diet (P>0.05). The gonads of oysters fed supplementary PUFA contained more docosahexaenoic acid (DHA) and less monounsaturated fatty acids. Higher level of DHA in gonads of T3 was associated with oogenesis and embryogenesis success. The n‐3/n‐6 ratio in the neutral lipid fraction provides a good indication of the spawning condition and predicting egg size and hatching rate.