Histomorphological observations on the liver in some freshwater teleosts.

Histomorphology of liver is studied in six species of teleost viz., Heteropneustes fossilis, Clarias batrachus, Puntius ticto, Danio malabaricus, Nandus nandus, Chana punctatus. The liver is a bilobed structure usually reddish brown in colour. There are accessory liver lobes in H. fossolis and C. batrachus. The histological examination shows compact mass of oval or polygonel hepatocytes, blood sinusoids and reticuloendothelial cells. In addition several patches of pigmented hepatocytes are also noticed. After partial hepatectomy the changes in liver structure are shrunken nature of hepatocytes, enlarged blood vessels and accumulation of lymphocytes near the cut portion. After biliary obstruction with the help of ligation of bile duct hepatocytes become turgid in appearance within seven days. There is fibrosis of blood vessels as well as bile spaces. The turgidity of hepatocytes increases fifteen days after the ligation so much so that some of them show necrotic appearance. There are numerous bile thrombi noticed after biliary obstruction.     

Comparative histomorphology of the Mauthner cells in some freshwater teleosts.

The histomorphological observations are made on the Mauthner cells in eight species of teleosts belonging to six different families. The cells are better developed in Channa punctatus, Heteropneustes fossilis, Labeo rohita, Danio, malabaricus and Puntius ticto. They are symmetrically situated in Nandus nandus and are found to be absent in Mastocembalus armatus. Their position, shape and size vary in different species. The axon cap is well developed in Channa punctatus, Heteropneustes fossilis and carps. The cell body sends lateral and ventral dendrites besides several small dendrites. The lateral dendrite emerges through the axon cap, turns dorsolateral and becomes myelinated to form Mauthner axon. The Mauthner axon extends in the spinal region upto the caudal peduncle and forms synapses with the spinal motoneurons of the front column. There are numerous synapses and end bulbs from the vestibular fibres and VIIIth nerve distributed on the perikaryan of the Mauthner cell body. It is suggested that the Mauthner cells are comparatively well developed in those species in which the tail fin is better utilized for swimming.     

Effects of osmolality and ions on the motility of stripped and testicular sperm of freshwater-and seawater-acclimated tilapia, Oreochromis mossambicus

A significantly higher concentration of testicular spermatozoa was obtained from freshwater Oreochromis mossambicus (9·9×10⁹ spermatozoa ml⁻¹) than seawater O. mossambicus (4·6×10⁹ spermatozoa ml⁻¹). The mean osmolality of the urine of freshwater fish (78·5 mOsmol kg⁻¹) was significantly different from that of seawater fish (304·8 mOsmol kg⁻¹). The mean length of the mid-piece of the spermatozoa together with the tail was more variable in freshwater O. mossambicus (8·80±0·23μm) than in seawater specimens (8·27±0·18 μm). Stripped sperm of freshwater O. mossambicus was highly contaminated by urine which was a good activator of sperm motility in O. mossambicus held in both fresh and sea water. The osmolality for initiation of motility in freshwater O. mossambicus spermatozoa was from 0 to 333 mOsmol kg⁻¹ while for seawater O. mossambicus spermatozoa it was from 0 to 1022 mOsmol kg⁻¹. The optimum osmolality for motility was from 70 to 333 mOsmol kg⁻¹ for freshwater O. mossambicus spermatozoa and from 333 to 645 mOsmol kg⁻¹ for seawater fish. In freshwater O. mossambicus spermatozoa, the presence of 20 mM CaCl₂ increased the permissive osmolality of NaCl from 184 to 645 mOsmol kg⁻¹. For seawater O. mossambicus spermatozoa, solutions of NaCl devoid of CaCl₂ were unable initiate motility, but the addition of 1·5 to 30 mM CaCl₂ to the NaCl solution (0–934 mOsmol kg₁) had a full motility initiating effect.     

Effect of metal mixtures on activity of two respiratory enzymes and their recovery in Oreochromis mossambicus (Peters).

Effects of sublethal doses of metal (Cu, Cd, Zn) mixtures on the activities of key respiratory enzymes (succinate dehydrogenase, SDH and glyceraldehyde dehydrogenase, GDH) and their recovery following withdrawal of treatments were studied in the freshwater fish O. mossambicus. On the basis of 96 hr LC50 Cu was highly toxic followed by Zn and Cd, and the trimetal combination (Cu+Zn+Cd) was extremely toxic than any other combination; combination of Zn+Cd was least toxic. A significant gradual decrease in SDH with a concomitant increase in GDH activity observed in liver, brain, muscle and gill of animals exposed to metal suggest a metabolic shift from aerobiosis to anaerobiosis due to metal action. Exposed individuals when transferred to metal impoverished water showed an improvement in SDH activity and decline in GDH activity suggesting slow reversal to aerobic metabolism. O. mossambicus needs more time for complete recovery.     

Acute and sublethal effects in an Indian major carp Cirrhinus mrigala exposed to silver nitrate: Gill Na+/K+-ATPase, plasma electrolytes and biochemical alterations

Due to prolonged use of silver in many applications, it enters into the freshwater and affects the aquatic organisms. Fingerlings of Cirrhinus mrigala were exposed to acute and sublethal concentrations of silver nitrate and the alterations of gill Na(+)/K(+)-ATPase, plasma electrolytes and biochemical parameters were assessed. The median lethal concentration of silver nitrate to the fish C. mrigala for 96 h was found to be 0.107 mg/l (with 95% confidence limits). 1/10th of LC 50 96 h value (0.0107 mg/l) was selected for sublethal study. During acute treatment branchial Na(+)/K(+)-ATPase activity was inhibited approximately 44.34% after 96 h of exposure. In sublethal treatment, silver nitrate could not produce a significant change in the activity of the enzyme at the end of 7th day. However, after 14th day, significant (p < 0.05) decrease was noted showing 22.52%-49.11% in rest of the study period. Silver intoxication resulted hyponatremia, hypokalemia, hypochloremia, and hypoproteinemia in both the treatments. Despite the decrease in these parameters, plasma glucose level was found to be increased in both the treatments to endure the silver toxicity. We suggest that the alterations in branchial Na(+)/K(+)-ATPase activity, plasma electrolytes, and biochemical parameters of fish may be useful in environmental biomonitoring and to assess the health of fish in freshwater habitat contaminated with silver.     

河川沙塘鳢对猎物种类和大小选择性研究

为了明确河川沙塘鳢(Odontobutis potamophila Günther)养殖宜投喂饵料生物的种类和规格, 通过室内外试验研究了沙塘鳢对生活习性不同8种饵料生物的种类选择, 对不同规格赤眼鳟(Squaliobarbus curriculus Richardson)的选择, 以及其不同生长阶段对饵料鱼大小的选择。研究结果表明, 沙塘鳢对麦鲮(Cirrhinus mrigala Hamilton)的选择指数显著大于其对剩余7种饵料生物的选择指数; 在无仿真水草条件下, 沙塘鳢对小规格饵料生物的选择指数显著大于对大、中规格饵料生物的选择指数; 在仿真水草条件下, 沙塘鳢对小规格饵料生物的选择指数显著大于其对大规格饵料生物的选择指数。在不同生长阶段中, 沙塘鳢全长与其捕食的饵料鱼全长呈现正相关关系; 沙塘鳢捕食的饵料鱼PPR值为0.23—0.73, 均值为0.49±0.1(均值±标准差); 随沙塘鳢规格的增加其捕食饵料鱼的PPR值降低, 捕食饵料鱼规格分布小于环境中饵料鱼规格分布。综上, 沙塘鳢养殖宜投喂饵料鱼麦鲮, 饵料鱼PPR值宜为0.38—0.6。     

东江下游惠州河段鱼类群落组成变化特征

2007～2010年先后5次对东江下游惠州(剑潭)河段鱼类群落进行调查,共采集到鱼类69种,分属于8目20科58属,主要以鲤科(39种)、鲿科(7种)、鳅科(5种)为主.鲮(Cirrhina molitorella)、鲨(Hemiculter leucisculus)、鲤(Cyprinus carpio)、赤眼鳟(Sq...     

Experimental transmission of Enteromyxum leei to freshwater fish

The myxosporean Enteromyxum leei is known to infect a wide range of marine fish hosts. The objective of the present study was to determine whether freshwater fish species are also receptive hosts to this parasite. Seventeen species of freshwater fish were experimentally fed E. leei-infected gut tissue from donor gilthead sea bream Sparus aurata obtained from a commercial sea bream cage farm. Four of the tested species, tiger barb Puntius tetrazona, zebra danio Danio rerio, oscar Astronotus ocellatus and Mozambique tilapia Oreochromis mossambicus, were found to be susceptible with prevalences ranging from 53 to 90%. The course of infection and pathology was limited to the gut mucosa epithelium and was similar to that observed in marine hosts. Little is known of the differences in physiological conditions encountered by a parasite in the alimentary tract of freshwater vs. marine teleost hosts, but we assume that a similar osmotic environment is maintained in both. Parasite infectivity may be influenced by differences in the presence or absence of a true stomach, acidic gastric pH and digestive enzyme activity both in the stomach and intestine. Variability in susceptibility among species may also stem from differences in innate immunity. Dimensions of spores produced in the donor sea bream and recipient freshwater species are variable in size, as previously observed in other captive marine host species.     

The relationship of p53 and stress proteins in response to bleomycin and retinoic acid in the p53 heterozygous mouse.

A single, i.p. dose of bleomycin was administered simultaneously with [35S]methionine to 4-month-old p53 wild type (+/+) and p53 heterozygous (+/-) C57BL/6 mice. Following a period of 3.5 h from dosing, the bone marrow nuclei were examined by two-dimensional PAGE and fluorography for induction of stress proteins (sps). Eight sps ranging from 22000 to 100000 Mr were synthesized in p53+/- and p53+/+ mice following elicitation by bleomycin. No quantitative or qualitative differences were observed in sp expression in these two groups of animals. In a second experiment, three doses of retinoic acid were given i.p. to p53+/- and p53+/+ mice over a 36 h period. The p53 isoforms in bone marrow nuclei from these mice were analyzed by PAGE for incorporation of [35S]methionine following retinoic acid injections. Quantitative and qualitative alterations in p53 isotypes were substantially increased in p53+/+ as compared with p53+/- mice. The increased complexity in the synthesis patterns in both groups of dosed mice consisted of additional isoforms possessing more acidic isoelectric values. In an in vitro binding assay, individual p53 isoforms demonstrated varying degrees of association with sps 25a, 70i, 72c and 90 which was consistently greater in p53+/+ mice. Both the synthesis and binding of isoforms were greater in G1 than in S+G2 phase, in both groups of animals, reflecting a cell cycle regulated mechanism for these events. Collectively, these data implied that the synthesis and the binding characteristics of p53 isoforms with sps were enhanced in the p53+/+ mice relative to the p53+/- mouse; however, sp labeling was not affected by p53 genotype.     

Impact of chronic phosalone toxicity on erythropoietic activity of fish, Oreochromis mossambicus.

Effect of multiple sublethal concentrations of Phosalone on whole animal and kidney oxygen consumption, haematological indices and serum enzymes of freshwater fish, Oreochromis mossambicus, were carried out over a 90 day exposure period. Significant changes were observed which have been indicating that the presence of hypoxic condition in the biosystem, gradual increase in the rate of synthesis of haemoglobin and disruption of liver function during the toxicity of phosalone.     

Investigational piscivory of some juvenile Australian freshwater fishes by the introduced Mozambique tilapia Oreochromis mossambicus

Experimental tanks were used to observe predatory effects in three different size classes of Mozambique tilapia Oreochromis mossambicus (one of the world's most widespread exotic species and generally regarded to be a herbivore or both herbivore and detritivore) when tested against 10 juvenile Australian freshwater fish species, and significant levels of predation against all were recorded. There was a general trend for larger O. mossambicus to kill more prey and this was also reflected in a separate series of experiments using juvenile barramundi Lates calcarifer over a range of size classes. Predatory effects by O. mossambicus broadly reflected the accepted models of predator–prey interactions, being that mortality (and survival) was closely related to relative body size and mouth gape limitation. Experimental evidence for piscivory in O. mossambicus was supported by field sampling that detected prey fish remains in 16% of all fish surveyed ( n = 176). The recognition of active piscivory by O. mossambicus in laboratory and field situations is the first such evidence, and suggests a need to re-evaluate the nature of their effects in introduced environments.     

Identification of teratogenic polymethoxy-1-alkenes from Cylindrospermopsis raciborskii,and taxonomically diverse freshwater cyanobacteria and green algae

Cylindrospermopsis raciborskii is among the most commonly recognized toxigenic cyanobacteria associated with harmful algal blooms (HAB) in freshwater systems, and specifically associated with multiple water-soluble toxins. Lipophilic metabolites from C. raciborskii, however, were previously shown to exert teratogenicity (i.e. inhibition of vertebrate development) in the zebrafish (Danio rerio) embryo model, specifically suggesting the presence of additional bioactive compounds unrelated to the currently known toxins. In the present study, a series of known teratogenic polymethoxy-1-alkenes (PMA) were identified, purified and chemically characterized from an otherwise well-characterized strain of toxigenic C. raciborskii. Although PMA have been previously identified in other cyanobacteria, this is the first time they have been identified from this recognized HAB species. Following their identification from C. raciborskii, the taxonomic distribution of the PMA was additionally investigated by chemical screening of a freshwater algal (i.e. cyanobacteria, green algal) culture collection. Screening suggests that these compounds are distributed among phylogenetically diverse taxa. Furthermore, parallel screening of the algal culture collection, using the zebrafish embryo model of teratogenicity, the presence of PMA was found to closely correlate with developmental toxicity of these diverse algal isolates. Taken together, the data suggest PMA contribute to the toxicity of C. raciborskii, as well as apparently several other taxonomically disparate cyanobacterial and green algal genera, and may, accordingly, contribute to the toxicity of diverse freshwater HAB.     

苏云金芽孢杆菌不同亚种菌株制剂毒力效价的研究

采用苏云金芽孢杆菌制剂美国标准品:Bacillus thuringiensis subsp. Kurstaki HD-1-S-1980(H_(3a3b))对不同亚种制剂:Bacillus thuringiensis subsp. Dendrolimus U菌株(H_(4a4b))和Bacillus thuringiensis subsp. Galleriae C88菌株(H_5a5b))进行了毒力效价的研究。以U菌株制备的标样与美国标准品对不同试虫进行了比较。生物测定的结果表明,U菌株标样的效价分别为18666.6IU/mg(试虫为马尾松毛虫Dendrolimus punctatus 2龄幼虫)、22956.5IU/mg(试虫为小菜蛾Plutella xylostella 2龄幼虫),均高于美国标样16000IU/mg的水平。其敏感度为小菜蛾大于马尾松毛虫。以U菌株和C88菌株生产的中试产品用美国标准品进行毒力测定,试虫为马尾松毛虫,其结果表明,U菌株产品毒力效价为36444.4IU/mg;C88菌株产品为28521.7IU/mg,两者均明显高于美国标准品。试验结果还表明,采用美国标准品及马尾松毛虫和小菜蛾为…     

Reproductive strategies of two invasive tilapia species Oreochromis mossambicus and Tilapia mariae in northern Australia

The reproductive biology of two invasive tilapia species, Oreochromis mossambicus and Tilapia mariae, resident in freshwater habitats in north-eastern Australia was investigated. Oreochromis mossambicus exhibited plasticity in some of its life-history characteristics that enhanced its ability to occupy a range of habitats. These included a shallow, weed-choked, freshwater coastal drain that was subject to temperature and dissolved oxygen extremes and water-level fluctuations to cooler, relatively high-altitude impoundments. Adaptations to harsher conditions included a decreased total length (L(T) ) and age (A) at 50% maturity (m50), short somatic growth intervals, early maturation and higher relative fecundities. Potential fecundity in both species was relatively low, but parental care ensured high survival rates of both eggs and larvae. No significant difference in the relative fecundity of T. mariae populations in a large impoundment and a coastal river was found, but there were significant differences in relative fecundities between several of the O. mossambicus populations sampled. Total length (L(T) ) and age at 50% maturity of O. mossambicus populations varied considerably depending on habitat. The L(Tm50) and A(m50) values for male and female O. mossambicus in a large impoundment were considerably greater than for those resident in a small coastal drain. Monthly gonad developmental stages and gonado-somatic indices suggested that in coastal areas, spawning of O. mossambicus and T. mariae occurred throughout most of the year while in cooler, high-altitude impoundments, spawning peaked in the warmer, summer months. The contribution these reproductive characteristics make to the success of both species as colonizers is discussed in the context of future control and management options for tilapia incursions in Australia.     

Biochemical and stress responses of rohu Labeo rohita and mrigal Cirrhinus mrigala in relation to acclimation temperatures

The biochemical and stress responses of two Indian major carps, rohu Labeo rohita and mrigal Cirrhinus mrigala were studied after acclimating them to four preset temperatures (26, 31, 33 and 36° C) for 30 days. The blood glucose and liver glycogen levels showed an inverse trend in both the species and were significantly different in L. rohita at higher temperatures. The decrease in the liver glycogen level of C. mrigala , however, was not significant. Plasma cortisol levels increased significantly whereas the ascorbic acid content in the brain and kidney of both the species decreased significantly with increasing temperatures. Total lipid content in the liver of both the species decreased significantly with increasing acclimation temperatures. The phospholipid concentration decreased in L. rohita with increasing acclimation temperatures, and in C. mrigala the values decreased up to 33° C and increased at 36° C. In C. mrigala , the cholesterol level decreased up to 33° C and then increased at 36° C, but the absolute value was lower in comparison to L. rohita . The cholesterol levels, however, were not significantly different in L. rohita . Triglycerides and free fatty acids concentrations decreased significantly with increasing acclimation temperatures in both the species. The present study indicates species-specific metabolic responses of L. rohita and C. mrigala to thermal acclimation.     

Phylogenetic relationships of freshwater bryozoans (Ectoprocta, Phylactolaemata) inferred from mitochondrial ribosomal DNA sequences

Most species of freshwater bryozoans (Ectoprocta: Phylactolaemata) have few morphological distinctions, and within phylactolaemates, the morphology of the statoblast has been used to determine evolutionary relationships. Here, two controversial phylogenies have been proposed for phylactolaemates with regard to the relationship of Lophopodidae to other families. Two plumatellid genera, Gelatinella and Hyalinella , are candidates for the ancestral type of lophopodids. In addition, the coexistence of spines on the surfaces of the statoblast has led to the suggestion that lophopodids are closely related to the family Cristatellidae. In this study, we analysed mitochondrial DNA sequences of the 12S and 16S rDNA genes of 10 phylactolaemate species. Our results suggest that plumatellids may not be a direct ancestral group of lophopodids and that cristatellids are not a sister group of lophopodids. Fredericella , which was previously thought to be an ancestral group, was revealed to be derived. In addition, our results suggest that Stephanella is the most basal phylactolaemate. Mapping morphological characteristics onto the sequence-based phylogenetic tree revealed convergent evolution of statoblast characters.     

The adaptation to salinity: Response of fish gill mitochondria to salinity stress

When a freshwater fish, Tilapia mossambica (now renamed Sarotherodon mossambicus) is exposed to a salinity stress, extensive changes are noted in the properties of the mitochondria isolated from the gill tissue. Our efforts were directed toward ascertaining the response of the gill mitochondria to an ion-osmotic shock to which the organism is exposed. Notable among them are the loss of ability to phosphorylate externally added ADP, decreased 45Ca++ uptake, lower transhydrogenase levels, and nonresponse to ATP + Mg++ for contraction. During this period there is a large influx of calcium into the mitochondria. Continued exposure to the stress situation reverses virtually all the changes to the freshwater levels.     

18S rRNA suggests that Entoprocta are protostomes,unrelated to Ectoprocta

The Ento- and Ectoprocta are sometimes placed together in the Bryozoa, which have variously been regarded as proto- or deuterostomes. However, Entoprocta have also been allied to the pseudocoelomates, while Ectoprocta are often united with the Brachiopoda and Phoronida in the (super)phylum Lophophorata. Hence, the phylogenetic relationships of these taxa are still much debated. We determined complete 18S rRNA sequences of two entoprocts, an ectoproct, an inarticulate brachiopod, a phoronid, two annelids, and a platyhelminth. Phylogenetic analyses of these data show that (1) entoprocts and lophophorates have spiralian, protostomous affinities, (2) Ento- and Ectoprocta are not sister taxa, (3) phoronids and brachiopods form a monophyletic clade, and (4) neither Ectoprocta or Annelida appear to be monophyletic. Both deuterostomous and pseudocoelomate features may have arisen at least two times in evolutionary history. These results advocate a Spiralia-Radialia-based classification rather than one based on the Protostomia-Deuterostomia concept. Correspondence to: J.R. Garey     

Analysis of catch data from 1968 to 1976 from nine fish landings in the Kenya waters of Lake Victoria

Fish landing data collected by the Kenya regional fisheries officers from Homa Bay, Kaloka, Karungu, Marenga, Wichlum, Kendu Bay, Usenge, Dunga and Ngegu from 1968 to 1976 were statistically analysed to determine trends in the traditional fisherman's catch in the Kenya waters of Lake Victoria. Over the nine years a significant decline occurred for total catch and catches of Haplochromis spp., Tilapia spp. and Protopterus aethiopicus. Engraulcypris spp. catch increased significantly; while catches of Bagrus docmac and Clarias mossambicus fluctuated and no clearly defined trend emerged, although B. docmac catch seemed to be declining.
Overall indications were that as the catch of traditionally preferred fish declined, Engraulicypris spp., B. docmac, C. mossambicus and recently introduced Lates niloticus were becoming more important to the total catch.     

Mutations in Chlamydomonas reinhardtii Conferring Resistance to the Herbicide Sulfometuron Methyl

Chlamydomonas reinhardtii mutants resistant to the herbicide sulfometuron methyl (SM) were isolated and characterized. Growth of C. reinhardtii is sensitive to inhibition by SM at a concentration of 1 micromolar. Four mutants resistant to 10- to 100-fold higher concentrations were isolated. All possess a form of acetolactate synthase (ALS) whose specific activity in cell extracts is 100- to 1000-fold more resistant to SM than is the specific activity of wild-type enzyme. Only one mutant had abnormally low ALS specific activity in the absence of SM. All mutations were inherited as single lesions in the nuclear genome and were expressed in heterozygous diploids. The mutations in two strains mapped to linkage group IX about 30 centimorgans from streptomycin resistance and on the same side of the centromere, and in genetic crosses between mutants no segregation was observed. Accordingly, all mutations are tentatively assigned to gene smr-1. Herbicide resistance appears to be suitable as a selectable marker for molecular transformation in this organism.