Could the essential oil of Lippia alba provide a readily available and cost-effective anaesthetic for Nile tilapia (Oreochromis niloticus)?

We report the optimal concentration of the essential oil of Lippia alba (EOLA) for the induction and recovery of anesthesia in Nile tilapia (Oreochromis niloticus) during handling. Groups of 10 juveniles were separately subjected to a concentration of EOLA: 0 (control group), 10, 20, 50, 100, 200, 300, or 500 µL L-1. The plasma cortisol levels were significantly decreased in anesthetized fish 4 h after stress of handling. The plasma glucose levels were significantly increased 1 and 4 h after stress of handling in fish exposed to EOLA. Sensory analysis showed that tasters did not detect differences through a blind test in fillet taste and odor between exposed and non-exposed fish. The ideal concentration to promote the best anesthesia and recovery times and to reduce plasma cortisol 4 h after handling is 500 µL L-1.     

尼罗罗非鱼致病性类志贺邻单胞菌(Plesiomonas shigelloides)的分离鉴定及其病理学观察

【目的】2013年5月广东番禺某养殖场罗非鱼出现大量死亡现象,临床症状表现为鱼体体色发黑、体表出血、鳞片脱落、鳍条溃烂等,解剖发现腹腔有大量腹水、胆囊肿大、肝呈黄色、脾脏呈暗红色。为确定病原,【方法】从具以上临床症状的病鱼组织中分离获得可疑菌株1株,编号PYS1。采用形态特征、生长特性、理化特征、16S rRNA基因序列分析等理化及分子生物学技术鉴定该菌株种类。通过人工回归感染及组织病理学研究确定该菌株的致病性,并开展药物敏感性试验筛选其敏感药物。【结果】结果表明PYS1菌株为类志贺邻单胞菌(Plesiomonas shigelloides),在16S rRNA基因序列构建的分子进化树中与其他鱼源类志贺邻单胞菌聚为一支。药敏试验结果表明该菌株已呈现多重耐药性,仅对少数检测抗生素(头孢曲松、头孢洛克和头孢唑啉等)敏感。人工回归感染结果显示PYS1菌株可使尼罗罗非鱼出现与自然发病鱼相似症状,其对尼罗罗非鱼半致死量为1.425×108CFU/尾,石蜡切片显示其对感染鱼的肠、肝、脾、肾和心脏等组织均可造成损伤。【结论】证明类志贺邻单胞菌为上述养殖场尼罗罗非鱼发病的病原,且为首次报道该菌对尼罗罗非鱼的致病性。     

四个奥利亚罗非鱼群体的微卫星分析

应用筛选到的19对微卫星引物,对四个不同来源的奥利亚罗非鱼（Oreochromis aureus）群体（奥利亚罗非鱼83系、奥利亚罗非鱼02系、奥利亚罗非鱼05系和红色奥利亚罗非鱼）的基因组DNA进行PCR扩增,分析其群体遗传结构和亲缘关系。根据几个群体在19个位点上的PCR扩增图谱,统计计算各群体的遗传多样性指数。四个群体的平均观测遗传杂合度值在0．154—0．391间;平均预期杂合度在0．181—0．428间;平均多态信息含量值在0．1513—0．3882间,说明它们的遗传多样性水平较低。遗传偏离指数D的评估结果显示这4个群体有多个位点存在不同程度的Hardy—Weinberg遗传平衡偏离。运用MicroChecker软件进行零等位基因预测,结果显示除红色奥利亚罗非鱼群体外,其他3个群体中均可能存在零等位基因位点。各群体零等位基因的位点数分别为：83系1个,02系3个,05系7个,红奥群体为0。零等位基因位点的存在可能是导致位点发生Hardy—Weinberg遗传平衡偏离的原因之一。4个群体中,05系群体与83系群体间的遗传相似性系数最高（0．9422）,遗传距离最小（0．0596）,说明两者亲缘关系最近;83系群体与红奥群体的遗传相似性系数最低（0．6977）,遗传距离最大（0．3599）,可推断两者亲缘关系最远。根据群体间的遗传距离采用UPGMA法进行聚类,结果表明：83系首先与05系聚类为一支,然后与02系群体聚类,最后与红奥群体聚类。聚类结果说明红奥群体与其他三个群体亲缘关系最远;83系群体与05系群体亲缘关系最近,与02系群体次之。     

Ingestion of suspended bacteria by fish: a modified approach

The ingestion of suspended bacteria by common carp larvae and juvenile tilapias was quantified by counting of fluorescently labelled bacteria (FLB) in guts of experimental fish under an epifluorescence microscope.     

奥利亚罗非鱼DMRT1,DMO基因片段的克隆及序列分析

根据其他鱼类DMRT基因中的保守序列设计了一对简并引物,利用RT-PCR扩增了雌雄奥利亚罗非鱼的DMRT基因,并对其扩增产物进行了克隆与测序。结果在雌雄奥利亚罗非鱼个体中获得了两个不同的片段,分别命名为DMO,DMRT1基因。序列同源性分析表明,奥利亚罗非鱼DMRT1,DMO cNA系列的同源性为61.78%,氨基酸同源性为86%,说明了DMRT基因存在性别差异。与尼罗罗非鱼、红鳍东方豚、虹鳟、青鱼将等鱼类DM保守区相比,氨基酸序列同源性为86%-100%,这充分显示了DM-RT基因在进化上的高度保守性。     

几种淡水鱼的胃腺细胞显微与超微结构的研究

尼罗非鲫的胃腺细胞和一般硬骨鱼类的泌酸胃酶细胞结构不同,属典型的泌酸细胞,与哺乳动物的壁细胞十分相似,细胞内充满微管泡系和线粒体,但是没有发现胃蛋白酶原颗粒,粗面内质网也极少,乌鳢,鲇和黄颡鱼的胃腺细胞则为典型的泌酸酶原细胞,除有微管泡系和线粒体外,还有丰富的胃蛋白酶原颗 和粗面内质网,用显示盐酸的Western方法证明这两类胃腺细胞都能分泌盐酸,但对检测色氨酸的Adams方法,两者都呈阴性反应,未能证明乌鳢胃细胞中胃蛋白酶原的存在,可能乌鳢的胃蛋白酶成分中色氨酸的含量不占多数,故未能检出。这两类胃腺细胞结构和功能的不同,与整个消化道结构的差别相一致,可能与它们的食性不同有关。微管泡系是两类胃腺细胞共有的结构,是泌酸的结构基础,由一系列短管的囊泡组成,在鱼类中,泌酸过程可能有顶浆分泌和局部分泌两种形式,泌酸活动中细胞顶膜,微管泡系以及高尔基体之间膜的转移关系和泌酸形式有关。     

The protective influence of ascorbic acid against the genotoxicity of waterborne lead exposure in Nile tilapia Oreochromis niloticus (L.)

The present study investigated the effects of lead (Pb) and ascorbic acid (AA) on Nile tilapia Oreochromis niloticus using the micronucleus (MN) and nuclear abnormality (NA) tests for periods of 7, 14 and 21 days. The MN frequencies in the erythrocytes, gill, liver and fin cells were analysed comparatively to evaluate the sensitivity and suitability of these different cell types. The NA shapes in erythrocytes were scored into blebbed nuclei (BL), lobed nuclei (LB), notched nuclei (NT) and binuclei (BN). It was observed that fish showed significant sensitivity to the different treatments. In general, the highest value of both MN and NA cells were significantly increased in the Pb-treated group followed by the combination of the Pb and AA-treated group. On the other hand, the MN and NA frequencies in erythrocytes were the most sensitive to the treatment and could provide more valuable information than those in gill, liver and fin cells. The frequencies of each NA shape in erythrocytes of all treatments were observed in the following ranked order NT > LB > BN > BL. The results demonstrated the efficacy of AA in reducing genotoxicity in fish induced by Pb. They showed the sensitivity and suitability of MN and NA frequencies in erythrocytes as pollution biomarkers.     

Fine structure of chloride cells in freshwater- and seawater-adapted Oreochromis niloticus (Linnaeus) and Oreochromis mossambicus (Peters)

Ultrastructural features of branchial chloride cells in Oreochromis niloticus (Linnaeus) and O. mossambicus (Peters) adapted to both fresh water and sea water were compdred. In freshwater adapted fish of both species chloride cells showed similar morphological features. Multicellular complexes made of a mature chloride cell and one or more accessory cells sharing a single apical crypt have been observed. Whereas high percentages of 0. mossambicus survived at maximum salinity only a few individuals of 0. niloticus showed the capacity to adapt to sea water. In the seawater-adapted individuals of 0. niloficus and 0. rnossambicus the chloride cells showed a two- and three-fold increase in sizei. respectively. Most chloride cells are organized in large multi-cellular complcxcs with apical interdigitations of accessory cells and 'leaky junctions'. These results indicate that the difference in euryhalinity of the species studied is related to functional rather than structural differences.