Early stages of Margaritifera margaritifera glochidiosis in Atlantic salmon: Morphopathological characterization

Freshwater mussels of the order Unionida encyst into the fish mucosa to metamorphose and complete their life cycle, causing a parasitic disease known as glochidiosis. This parasitic stage represents a bottleneck for the survival of naiads, particularly for critically endangered species as Margaritifera margaritifera; however, little is known about the events occurring during this critical stage. Therefore, this study aimed to histologically characterize the development of M. margaritifera glochidiosis in Atlantic salmon to get insight into the pathogenesis of this interaction. Fish exposed to glochidia were sampled during the first 44 days post-exposure, and organs were observed by stereomicroscopy and light microscopy. Glochidia attached to the gills by pinching the lamellar epithelium, whereupon an acute proliferative branchitis engulfed most of the larvae. However, during the first 14 days, a severe detachment of unviable glochidia occurred, associated with the presence of pleomorphic inflammatory infiltrate and epithelial degeneration. In the cases where larvae remained attached, a chronification of the lesions with none to scarce inflammation was observed. These results provide key information to better understand the complex host–parasite interaction during the early stages of glochidiosis and provide valuable information to optimize artificial rearing of naiads in conservation of threatened freshwater mussel populations.     

Non‐spherical pearl layers in the Polynesian ‘black‐lipped’ Pinctada margaritifera: The non‐nacreous deposits compared to microstructure of the shell growing edge

Cultivated pearls frequently exhibit morphological irregularities making obvious that mineral deposition was irregularly distributed onto nucleus surface. Taking advantage of experimental cultivations with short durations (from 10 days to few months), these irregular deposits predating occurrence of the nacre were investigated in Polynesian pearls by biochemical characterizations and a series of physical methods. Diversity in the resulting data suggests that various in‐depth alterations of the biomineralization mechanism may have occurred during the grafting process, leading to diversity in the biochemical pathways to nacreous deposition. This allows a precise discussion of current views about pearl formation. The “reversed shell theory” is formally disproved through point to point comparison with development of the shell growing edge. Similarity of pearl formation with “regeneration” or “shell repair” is also discussed, emphasizing the differences between these concepts.     

Freshwater nucleated pearl quality is influenced by host mussel growth traits in Hyriopsis cumingii

Hyriopsis cumingii is one of the most important freshwater pearl mussels in China. Recently, this species can produce freshwater nucleated pearls of high quality. Here, we investigated whether nucleated pearl quality is influenced by the growth traits of the host mussel or other factors like cultivation period. We implanted host mussels with a spherical nucleus consisting of a small piece of mantle tissue from donor mussels. After 24 and 36 months of culture, host mussel growth traits including body weight and shell length, height, width and weight were recorded. These factors were then correlated with the quality traits of the pearls they produced, such as nacre thickness, size, weight, lustre and colour. Results indicated pearls obtained at 36 months after seeding were significantly larger in terms of nacre thickness, size and weight compared to those harvested at 24 months. In particular, nacre thickness (r = 0.33–0.48, P = 0.00), pearl size (r = 0.39–0.43, P = 0.00) and pearl weight (r = 0.35–0.47, P = 0.00) were showed to be significantly correlated with host mussels shell length, body weight and shell weight at 24 or 36 months. Larger and heavier host mussels tended to produce bigger pearls. In contrast, host mussels did not affect pearl colour. Cumulatively, our results suggest that longer culturing times and a larger host mussel may help produce better quality nucleated pearl. This information can help guide selective breeding programs designed to improve pearl quality produced by H. cumingii.     

Phenotypic indicators for cultured pearl size improvement in the black‐lipped pearl oyster (Pinctada margaritifera): towards selection for the recipient growth performance

The black‐lipped pearl oyster, Pinctada margaritifera, is the most important farmed species in French Polynesia and the basis of the most valuable export industry. Mass production of black pearls relies on a surgical operation requiring tissue from a donor pearl oyster to be grafted, together with a nucleus made of shell, into the gonad of a recipient oyster. Improving pearl size through family selection remains one of the main challenges for future aquaculture development. This study analyses the relative contribution of donor and recipient oysters to pearl size. To this end, hatchery‐produced donor oysters of two batches, large and small (based on shell height), were used to supply grafts for recipients, which were then monitored individually for their growth performance by recording shell height, width, and thickness, and total live weight (flesh + shells) every 6 months (four biometric measurement times) over 20 months of culture. Pearls issued from the two batches of donors showed no significant differences in nacre weight or thickness. In contrast, recipient oyster shell height and total weight were increasingly positively correlated with these pearl size parameters over the culture period, becoming significant at 8 months post‐grafting. Potential therefore exists to use shell height and oyster weight as phenotypic indicators for selective breeding of recipient oysters with high growth performance to increase pearl size in P. margaritifera.     

琯溪蜜柚砂囊粒化的无损检测

摘 要：柑橘砂囊粒化是柑果成熟期与采后贮藏期的常见生理性病害，严重影响果实品质。本文采用1.5 T 高场磁共振成像仪对采后贮藏30 d的琯溪蜜柚[Citrus grandis (L.) Osbeck]果实进行磁共振扫描检查，并以同层断面解剖图为对照，评估磁共振成像（MRI）应用于柑橘砂囊粒化症无损检测的有效性。结果表明， MRI检测中，T2WI能够显著区分果肉组织与海绵层组织的信号差异，其信号强度可代表果实组织相对含水量；T2WI信号在砂囊粒化部位强度显著降低，病变组织的失水特征清晰，与解剖结果一致。T2WI对砂囊粒化的确诊率100%，显著优于T1WI成像的识别率41.7%（χ2 = 5.76，P = 0.016）；T2WI和T1WI均能显示种籽照影，但T2WI对果肉组织影像的分辨率优于T1WI，因此MRI的T2WI分析可作为一种无损检测方法，对柚商品果实上市前砂囊粒化症发生程度以及种籽有无进行评估。     

北海珍珠养殖区与非养殖区春、秋季磷的形态特征及其相关性

利用2008年9月和2009年4月对北海珍珠养殖区和非养殖区的调查资料,对该海区磷的循环特征及其生态效应进行了分析研究.研究结果表明,该海区磷的储量不高,无论是养殖区还是非养殖区均表现为有机态磷和无机磷含量明显偏低.除颗粒态磷外,所有形态磷均表现为秋季明显高于春季,突出体现了生物释放的补充影响作用.在磷的形态转化上,春...     

Evaluation of landrace topcross hybrids of pearl millet for arid zone environments

Pearl millet (Pennisetum glaucum (L.) R. Br.) cultivars for marginal, arid environments need to combine the adaptation to stress conditions of indigenous landraces with an improved yield potential and disease resistance, to allow them to both perform well in farmers fields and to meet the requirements for cultivar release. This paper evaluates landrace-based topcross hybrids (adapted landraces crossed on high-yielding male-sterile lines), as a quick and efficient way of achieving this objective. Topcross hybrids showed a consistent increase in biomass production across all test environments, including the harsh arid zone environments. Depending upon the plant type of the male-sterile used to make the hybrid, this was expressed as increased grain yield only, or increased grain and fodder yields. The downy mildew (Sclerospora graminicola) reaction of the topcross hybrids was determined by the reaction of the male-sterile line used, with the resistant male-sterile producing resistant topcross hybrids and vice-versa. Topcrossing adapted landraces on high-yielding male-sterile lines thus provides an opportunity to improve disease resistance and grain and/or fodder yields, with no apparent loss of adaptation to the marginal environments in which the landraces have evolved.ICRISAT Journal Article no. 1575     

Characterization of seed producing pearl millet x elephantgrass hexaploid hybrids

Summary Successful widespread use of a forage or biomass plant depends largely on its ease of establishment. Elephantgrass (Pennisetum purpureum Schum.) is used for both forage and biomass production, due to its high dry matter production, aggressiveness, perenniality, and forage quality. However, lack of high quality seed has limited the use of elephantgrass and its hybrids to pearl millet (P. glaucum L. R.Br.). Development of a seed-propagated pearl millet x elephantgrass hexaploid cultivar, which would combine desirable characteristics from both of these species, would be highly desirable. The objectives of this study were to characterize morphological and seed-related traits from the selfed progeny of seven hexaploid hybrids, and to determine whether seed size had any influence on these traits. Traits studied included number of tillers, height, leaf length and width, panicles per plant, days to flowering, panicle length, seed set, seed production, and weight of 100 seeds. Genetic differences were found among the progeny of the seven hybrids. Differences were also found between plants derived from large- and small-seed lots within families. Plants descended from larger seed had better growth and seed-related characteristics, which resulted in more desirable plants. These hexaploid hybrids showed potential for direct seeding into the field for biomass or forage production.     

Wheat x pearl millet hybridization: consequence and potential

Summary Eight grain pearl millet (2n=14) accessions were crossed as male to hexaploid spring wheat cv. Fukuho (2n=6x=42). An average of 80% wheat pistils showed pearl millet pollen tube entry in the ovules, compared to 56% in wheat x maize cv. Seneca 60 cross. Of the 15 embryos, obtained through in vitro immature seed culture from wheat x pearl millet crosses, 3 plantlets were produced and grown to maturity. These three were of the somatic chromosome constitution 2n=42, 21 and 22, respectively. Haploid wheat plant (2n=21) apparently originated from pearl millet chromosome elimination during embryogenesis. The 22 chromosome plant had retained a single pearl millet chromosome at tillering stage, but this chromosome was eliminated from pollen mother cells prior to and also during gamete formation. The significance and potential uses of this wide cross is discussed.