额尔齐斯河贝加尔雅罗鱼单殖吸虫群落多样性及感染情况

研究贝加尔雅罗鱼(Leuciscus baicalensis)感染的单殖吸虫的群落多样性及感染情况,为额尔齐斯河鱼类寄生虫病防治提供基础资料。2009年8月到2016年7月,剖检贝加尔雅罗鱼296尾,共感染了6种单殖吸虫,分别为号筒指环虫(Dactylogyrus tuba Linstow,1878)、双髻指环虫(D. sphyra Linstow, 1878)、小刺指环虫（D. micracanthus Nybelin,1937）、多小枝指环虫（D. ramulosus Malewitzkaja,1941）、普氏三代虫（Gyrodactylus prostate Erergns,1963）和斯氏拟双身虫（Paradiplozoon skrjabini Achmerov,1974）;贝加尔雅罗鱼单殖吸虫的总感染率为20.27 %,平均感染强度为3.05只/尾(1~18只/尾),平均感染丰度为(0.62±2)只/尾;混合感染率相对较低,仅占2.36%;各单殖吸虫的感染率均小于10%,平均感染强度均小于5,其中小刺指环虫为优势种;在5个体长段中,在14cm≤L＜16cm体长段感染单殖吸虫的种类、感染率及感染强度均达到最高;体长段之间的多样性指数、优势度指数、均匀度指数及丰富度指数结果相差不大,不同体长段宿主中单殖吸虫种群的分布类型均为聚集分布;体长段14cm≤L＜16cm与16cm≤L感染强度差异显著,其余体长段之间的感染强度差异均不显著。     

A role for the protease falcipain 1 in host cell invasion by the human malaria parasite

Cysteine proteases of Plasmodium falciparum are required for survival of the malaria parasite, yet their specific cellular functions remain unclear. We used a chemical proteomic screen with a small-molecule probe to characterize the predominant cysteine proteases throughout the parasite life cycle. Only one protease, falcipain 1, was active during the invasive merozoite stage. Falcipain 1-specific inhibitors, identified by screening of chemical libraries, blocked parasite invasion of host erythrocytes, yet had no effect on normal parasite processes such as hemoglobin degradation. These results demonstrate a specific role for falcipain 1 in host cell invasion and establish a potential new target for antimalarial therapeutics.     

Quorum sensing is required for full virulence of Vibrio campbellii towards tiger grouper (Epinephelus fuscoguttatus) larvae

The link between quorum sensing in Vibrio campbellii and its virulence towards tiger grouper (Epinephelus fuscoguttatus) was investigated using V. campbellii wild type and quorum‐sensing mutants with inactive quorum sensing or constitutively maximal quorum‐sensing activity, and signal molecule synthase mutants. The results showed that wild‐type V. campbellii is pathogenic to grouper larvae, causing more than 50% mortality after 4 days of challenge. Furthermore, the mortality of larvae challenged with the mutant with maximally active quorum sensing was significantly higher than that of larvae challenged with the wild type, whereas a higher survival was observed in the larvae challenged to the mutant with a completely inactive quorum‐sensing system. Grouper larvae challenged with either the signal molecule synthase triple mutant, the harveyi autoinducer‐1 (HAI‐1) synthase mutant and the autoinducer‐2 (AI‐2) synthase mutant showed higher survival than larvae challenged with the wild type. In contrast, larvae challenged with the cholerae autoinducer‐1 (CAI‐1) synthase mutant showed high mortality. This indicates that HAI‐1 and AI‐2, but not CAI‐1, are required for full virulence of V. campbellii towards grouper larvae. Our data suggest that quorum‐sensing inhibition could be an effective strategy to control V. campbellii infections in tiger grouper.     

Different carbon sources affects biofloc volume,water quality and the survival and physiology of African catfish <Emphasis Type="Italic">Clarias gariepinus</Emphasis> fingerlings reared in an intensive biofloc technology system

A 6-week experiment was performed to compare different carbon sources, i.e. sucrose, glycerol and rice bran, to a nitrogen ratio of 15:1 in a biofloc-based African catfish Clarias gariepinus culture system. Catfish survival, growth, whole-body proximate composition, body indices, liver histopathology and glycogen content were measured. Each treatment was triplicated in glass aquaria with each replicate containing 50 fish (500 fish/m³) with an initial weight ± SD of 5.06 ± 0.05 g. Glycerol significantly increased total biofloc production, and both the sucrose and glycerol treatments generally had lower nitrogenous levels, compared to the control. These levels spiked at week 2 in the rice bran treatment, leading to significantly lower survival compared to all other treatments. At both weeks 3 and 6, liver histopathology of fish in the rice bran treatment revealed substantial vacuolation and less glycogen while the highest was in fish from the glycerol treatment. Fish growth was unaffected among the treatments, but survival was highest in the glycerol treatment. Rice bran appears unsuitable for C. gariepinus, likely due to being a slower-releasing carbon source. Instead, glycerol is recommended based on significantly higher biofloc production and subsequently improved water quality and survival of C. gariepinus during their nursery culture.