Live coral repels a common reef fish ectoparasite

Coral reefs are undergoing rapid changes as living corals give way to dead coral on which other benthic organisms grow. This decline in live coral could influence habitat availability for fish parasites with benthic life stages. Gnathiid isopod larvae live in the substratum and are common blood-feeding parasites of reef fishes. We examined substrate associations and preferences of a common Caribbean gnathiid, Gnathia marleyi. Emergence traps set over predominantly live coral substrata captured significantly fewer gnathiids than traps set over dead coral substrata. In laboratory experiments, gnathiids preferred dead coral and sponge and tended to avoid contact with live coral. When live gnathiids were added to containers with dead or live coral, significantly fewer were recovered from the latter after 24 h. Our data therefore suggest that live coral is not suitable microhabitat for parasitic gnathiid isopods and that a decrease in live coral cover increases available habitat for gnathiids.     

Experimental transmission and pathogenicity of some zoosporic fungi toTilapia fish

Seventeen fungal species belong to six genera were recovered from the four organs ofTilapia fish and the most common wereSaprolegnia ferax, S. diclina, Achlya dubia, A. americana, A. racemosa andA. flagellata, Dictyuchus sterile,Pythium undulatum andAphanomyces sp. Severe infection followed by death of all fish was incited byS. parasitica andS. ferax through experiment I. 30–70% ofT. nilotica andT. galileae were killed through experiment II byS. parasitica andS. ferax. T. galileae was more susceptible to fungal infection thanT. nilotica.     

7种甲真菌病致病菌的侵袭力比较

目的观察红色毛癣菌、白念珠菌、红酵母、短帚霉、串珠镰刀菌、烟曲霉、绳状青霉是否具有侵犯离体甲板的能力,并比较其侵袭能力的强弱。方法将无菌甲板接种于红色毛癣菌、白念珠菌、红酵母、短帚霉、串珠镰刀菌、烟曲霉、绳状青霉7种真菌的3种不同培养基(固体沙氏培养皿、液体沙氏试管及生理盐水试管)中,定期用NaOH溶甲法分析甲板受侵程度。结果某些非皮肤癣菌性丝状真菌侵犯体外甲板的能力与红色毛癣菌基本相同,但丝状真菌比酵母菌强,酵母菌中白念珠菌比红酵母强。同一种真菌在固体培养基上对甲板的侵袭力远比在液体培养基中或生理盐水中强。结论一定条件下,某些非皮肤癣菌也能直接侵犯甲板。真菌侵犯甲的能力与其形成菌丝的能力及其与甲板接触的稳定性成正比。     

Isolation and pathogenicity of a Bacillus sp. associated with a septicaemic condition in some tropical freshwater fish species

Observations made over a three-year period at the Fish Diseases Laboratory of the African Regional Aquaculture Centre (ARAC), Nigeria, revealed the gradual emergence of a new, highly infectious septicaemic condition in some widely cultivated freshwater fish species. The broad host range included: Heterobanchus bidorsalis, Clarias gariepinus, “Heteroclarias” (a hybrid of these two species, male and female respectively), Chrysichthys nigrodigitatus, and Cyprinus carpio. Clinical signs and pathological lesions associated with the condition were tyical, irrespective of the fish species affected; natural outbreaks apeared to be associated with stress due to environmental factors. The bacterium isolated from moribund and freshly-dead fishes was identified as a Bacillus sp., based on the observed cultural, morphological and biochemical characteristics. Fish reinfection trials confirmed that the isolate was the causative agent of the condition. Antibiotic sensitivity tests showed that the organism was sensitive to tetracycline hydrochloride.     

Diversity of the Chlamydia trachomatis common plasmid in biovars with different pathogenicity

The 7.5-kb plasmid of Chlamydia trachomatis (CT) is believed to encode essential genes and might have a role in CT pathogenicity. Accordingly, analysis of plasmid-linked mutations in isolates from biovars with different pathogenic properties should help in identifying which plasmid-encoded genes, if any, may be involved in modulating virulence. For this purpose, the plasmid present in a low-virulence isolate (trachoma biovar, serotype D) was cloned and sequenced. Nucleotide changes were experimentally checked against the sequence of the plasmid variant from the highly virulent strain L2/434/Bu (LGV biovar). By aligning our data with two published sequences of different trachoma and LGV variants a general consensus structure was determined, comprising eight major open reading frames (ORF) and a number of points where there is consensus only between isolates of the same biovar (biovar-specific mutations). The degree of variation between different isolates is less than 1%. In particular, comparison of serotype-D and -L2 plasmids shows mutations which are generally silent or lead to few (one to four), often conservative, amino acid changes in ORFs 1, 2, 4, 5, 6, and 7. The protein encoded by ORF8 is completely conserved. In contrast, the polypeptide variants encoded by ORF3 show nine amino acid changes, seven of which are due to biovar-specific mutations.     

Role of iron in the pathogenicity of Vibrio damsela for fish and mammals

Abstract The ability to obtain iron of 14 isolates of Vibrio damsela with different degrees of virulence for mice and turbot ( Scophthalmus maximus ) has been evaluated in artificial and natural iron-restricted environments. All strains were capable of utilizing haemoglobin (Hb) and ferric ammonium citrate (FAC) as the sole iron sources in vitro. However, only virulent V. damsela strains were able to resist the bacterioslatic and bactericidal effects of human and turbot sera, their growth being enhanced by the addition of Hb and FAC. The inhibitory effect of these sera on the growth of the non-pathogenic strain (ATCC 35083), however, was reversed by heat treatment (56°C for 60 min). The role of iron-availability on the virulence was investigated in iron-overloaded animals. The iron-treatment before the infection resulted in a significant reduction in the LD₅₀ of virulent strains. This fact demonstrates a positive correlation between iron availability in host fluids and degree of virulence in the species Vibrio damsela .     

Aggression and welfare in a common aquarium fish, the Midas cichlid

Many species of fishes are aggressive when placed in small aquaria. Aggression can negatively affect the welfare of those individuals toward whom it is directed. Animals may behave aggressively in order to defend resources such as food, shelter, mates, and offspring. The decision to defend depends on the distribution of resources and on ecological factors such as number of competitors, amount of available space, and amount of habitat complexity. This study tested the effects of these factors on aggression in a common aquarium fish, the Midas cichlid (Amphilophus citrinellus). The study found that time spent behaving aggressively was not associated with small-scale differences in group size or available space. Aggression was significantly lower in a large aquarium with a complex habitat. Aquaria of sizes typically used in the companion animal (pet) hobby did not provide optimal welfare for cichlids housed with aggressive conspecifics. The public should be aware that this and similar species require larger aquaria with complex habitat, which elicit more natural behavior.     

Iron uptake by Pasteurella piscicida and its role in pathogenicity for fish.

We evaluated the iron uptake mechanisms in Pasteurella piscicida strains as well as the effect of iron overload on the virulence of these strains for fish. With this aim, the capacity of the strains to obtain iron from transferrin and heme compounds as well as their ability to overcome the inhibitory activity of fish serum was analyzed. All the P. piscicida strains grew in the presence of the iron chelator ethylene-diamine-di (O-hydroxyphenyl acetic acid) or of human transferrin, which was used by a siderophore-mediated mechanism. The chemical tests and cross-feeding assays showed that P. piscicida produced a siderophore which was neither a phenolate nor a hydroxamate. Cross-feeding assays as well as preliminary chromatographic analysis suggest that this siderophore may be chemically related to multocidin. All the P. piscicida isolates utilized hemin and hemoglobin as an iron source, since the virulence of the strains increased when the fish were preinoculated with these compounds. This effect was stronger in the avirulent strains (50% lethal dose was reduced by 4 logs when fish were pretreated with hemin or hemoglobin). Only the pathogenic P. piscicida isolates were resistant to the bactericidal action of the fresh fish serum. The nonpathogenic strains grew in fish serum only when it was heat-inactivated or when it was supplemented with ferric ammonium citrate, hemin, or hemoglobin. In all the strains, at least three iron-regulated outer membrane proteins (IROMPs) (105, 118, and 145 kDa) were increased when the strains were cultured in iron-restricted medium.(ABSTRACT TRUNCATED AT 250 WORDS)     

Differential effects of native vs. invasive predators on a common Caribbean reef fish

Predators may have consumptive (lethal) and non-consumptive (sub-lethal) effects on prey. Non-consumptive effects include altered behavior and reduced growth and fecundity. Native prey may not recognize non-native predators as a threat, and therefore may suffer pronounced effects. Additionally, non-native predators may elicit different behavioral responses from prey compared to native predators. Theory predicts that consumptive effects should be greater for non-native predators (due to prey naiveté), and non-consumptive effects should be greater for native predators (due to predator recognition). To test these hypotheses, I monitored bicolor damselfish (Stegastes partitus) in the presence of invasive predatory Pacific lionfish (Pterois spp.), a native predator (graysby, Cephalopholis cruentata), and an egg predator (bluehead wrasse, Thalassoma bifasciatum). Body size and location of lionfish and graysby were monitored on reefs in the Bahamas. Bicolor fecundity was measured as the number and size of egg-masses that individual fish laid. Bicolor fecundity was negatively correlated with lionfish density but not graysby or bluehead density. Neither predator had a detectable effect on bicolor body size, but lionfish density was negatively correlated with the size of mature adult damselfish. I observed behavioral responses of bicolors to the two piscivores, to bluehead wrasse, and to two herbivorous fishes (Acanthurus coeruleus, Scarus spp.) as non-aggressive controls. Bicolors changed behavior (feeding and aggression) in the presence of all native fishes, but not in the presence of lionfish. Thus, differential effects exist between native and non-native predators, and invasive lionfish pose a non-consumptive threat to bicolor damselfish via reduced growth and fecundity.     

Levels of common antigens in determining pathogenicity of Curvularia eragrostidis in different tea varieties

AIMS: Pathogenicity of Curvularia eragrostidis, a foliar fungal pathogen of tea was studied in 24 commercially cultivated tea varieties by analysing the antigenic patterns of host and pathogen with the help of immunoserological techniques. METHODS AND RESULTS: Initial testing by cut shoot inoculation technique followed by whole plant inoculation technique showed that among the varieties tested, TV12 was the most susceptible and TV25 most resistant. Antigen preparations from tea varieties, fungal pathogens (C. eragrostidis and Lasiodiplodia theobromae) and a nonpathogen (Gliocladium virens) were compared by immunodiffusion, immunoelectrophoresis and indirect ELISA to detect common antigens shared by host and pathogen. Common antigens were detected by immunodiffusion and immunoelectrophoresis only among susceptible varieties and the pathogens. Such antigens were not found between the pathogens and the resistant varieties and also between nonpathogens and tea varieties. However, ELISA revealed the presence of low level of common antigens between all combinations. A certain minimum level of antigens was present for compatible host-pathogen interaction. Indirect labelling of antibodies with fluorescein isothiocyanate (FITC) showed that cross-reactive antigens were found to be concentrated mainly in the epidermal cells and also spread throughout the cortical cells. CONCLUSION: Pathogenicity of C. eragrostidis to different varieties of tea was found to be related to the level of common antigens present between host and pathogen. SIGNIFICANCE AND THE IMPACT OF THE STUDY: Indirect ELISA proved to be valuable in screening commercially cultivated varieties of tea for their susceptibility to C. eragrostidis.     

Domestication and absolute ownership of fish in the English common law

The English common law has, for the purpose of describing the rights of ownership of animals, divided them into two classes, those the subject of absolute ownership and those the subject of a limited property right. In this system, fish have long been regarded as the subject of a limited property right, one dependent on possession.
The principles underlying those concepts follow the Roman law concepts applicable to the proprietorship of animals and adopted in much of Europe. Those principles were further developed and adapted over many centuries in England, but more significantly in the common law countries outside of England, over the last century. They are principles that have a limited relationship to domestication. Drawing on the recent decisions outside of England it is possible to refashion the commonly presented tests as to the absolute ownership of animals. Based on those decisions, it may be asserted, that a person may absolutely own an animal that is a member of a population of animals that have had a long association with humans, or are exploited by a community in a recognized manner, other than by hunting. When applied to fish, particularly those from stock enhancement, sea ranching and aquaculture escapes, those principles raise a number of questions. Does the aquaculturist remain the owner of the fish that have escaped? Is it possible to retain ownership of stock enhancements and sea ranched fish? In some cases they may also raise an issue as to the liability for those fish at large.     

Ultrastructure of the tegument of the metacercaria of Timoniella imbutiforme

The spinous body tegument of the metacercaria of Timoniella imbutiforme (Molin, 1859) is described in detail and found to comprise an outer tegumental syncytium connected to subjacently situated subtegumentary 'cells'. There are four types of secretory bodies in the outer syncytial layer as well as serrated overlapping spines and mitochondria. The subtegumentary 'cells' are characterized by the presence of four secretory body types as well as giant bodies which may be involved in the elaboration of the secretory bodies or spine material. The normal configuration of the somatic muscles of T. imbutiforme show that the muscular machinery necessary for activity once the larval stage becomes excysted is already in place. The sensory endings are found to be of the uniciliate type occurring in groups of up to eight in raised domes distributed over the body. Secretory gland cells are numerous and possess long ducts connected to the basal lamina of the outer syncytial layer via septate desmosomes.     

Phenotypic characteristics and pathogenicity of Aeromonas genomospecies isolated from common carp (Cyprinus carpio L.)

AIMS: To evaluate the relationship between the genomospecies, phenotypic profile and pathogenicity for carp of 37 motile Aeromonas strains. METHODS AND RESULTS: Aeromonas strains were identified to genomospecies level by the 16S rDNA restriction fragment length polymorphism (RFLP) method and characterized phenotypically by the API 20E and API Zym systems and by conventional tube or plate methods. 16S rDNA RFLP analysis showed that the strains belonged to five species, Aeromonas bestiarum (5), Aerom. salmonicida (13), Aerom. veronii (11), Aerom. sobria (6) and Aerom. encheleia (2). Most strains of Aerom. bestiarum (80%) and Aerom. salmonicida (85%) could be separated by growth at 4 and 42 degrees C, autoagglutination after boiling, reaction for lipase (C14) and naphthol-AS-BI-phosphohydrolase. All strains of Aerom. veronii corresponded to Aerom. veronii biotype sobria and could be separated from Aerom. sobria by citrate utilization, growth at 37 and 42 degrees C, amygdalin and cellobiose fermentation. All strains of Aerom. bestiarum and most strains of Aerom. salmonicida (76.9%) and Aerom. veronii (63.6%) were pathogenic for carp. CONCLUSIONS: The biochemical identification of carp Aeromonas strains is not entirely clear. Some association between Aeromonas species, phenotypic profile and specific disease signs was observed. SIGNIFICANCE AND IMPACT OF THE STUDY: The results will be useful for ichthyopathology laboratories in the diagnosis of motile aeromonad septicaemia in carp.     

Characterization of 16 microsatellite loci for a common coral reef fish,the fierce shrimpgoby Ctenogobiops feroculus

We developed 16 pairs of primers for microsatellite loci of the fierce shrimpgoby, Ctenogobiops feroculus. Analysis of 35–40 gobies per locus from five islands in French Polynesia indicated that allele frequency varied from two to 30 per locus, while observed heterozygosity ranged between 0.05 and 0.98. These microsatellites should provide insight into patterns of dispersal and connectivity among populations of this common coral reef fish.     

The lateral musculature of the common bully, Gobiomorphus cotidianus, a freshwater fish from New Zealand

A histochemical and ultrastructural study has shown that the myotome of the common bully, Gobiomorphus cotidianus , is composed of three muscle fibre types: white, pink and small diameter fibres. There are no red fibres. Both white and pink fibres have characteristics similar to these fibres found in other teleosts. The small diameter fibres are located in the position usually occupied by red fibres and are identified by their small size and poor staining characteristics. At the ultrastructural level these small fibres are seen to have few mitochondria and a poorly developed sarcoplasmic reticulum. It is suggested that the small diameter fibres are a type of tonic muscle used for positioning the trunk.     

Toward a more humane intracerebral pathogenicity index that does not compromise virus pathogenicity ratings

Determination of the intracerebral pathogenicity index (ICPI) of a virus requires tracking sick animals until death or until the eighth day of the standard observation period. A more humane procedure would be to painlessly kill sick animals, but such intervention in the standard protocol could compromise the rating of the virus. In this paper, a modified scoring system is proposed, whereby humanely killed animals are given a score that, on average, does not alter the ICPI. The variance of an animal's contribution to the optimum modified ICPI is never greater than the variance of its contribution to the standard ICPI.