Erythrocytes of olive £ounder, Paralichthys olivaceus (Temminck et Schlegel), were treated with serial concentrations of formalin (37% formaldehyde) to investigate in vitro haemolysis and methaemoglobin formation. In addition, the short-term toxicity of formalin concentrations of 0,100, 212 and 300 ppm was also studied by clinical tests in which ¢sh were subjected to 3-h bath exposure. There was no haemolysis of ¢sh erythrocytes exposed to formalin concentrations ranging from 31.3 to 2000 ppm. Methaemoglobin formation, however, was induced at concentrations greater than 500 ppm. Red blood cell count, haemoglobin, haematocrit, mean corpuscular haemoglobin concentration and percentage of immature erythrocytes were also markedly elevated in all formalin-exposed groups (Po0.05). Formalin exposure also caused signi¢cant increases in alkaline phosphatase, aspartate aminotransferase, lactate dehydrogenase, potassium, chloride, magnesium and inorganic phosphorus (Po0.05). However, total protein decreased signi¢cantly in the formalin-exposed groups (Po0.05). No signi¢cant diierences in white blood cell count, mean corpuscular volume, mean corpuscular haemoglobin, albumin, glucose, total cholesterol, high-density lipoprotein cholesterol, free cholesterol, alanine aminotransferase, calcium, creatinine and total bilirubin were observed in the formalinexposed groups (P40.05).

Effects of formalin on haematological and blood chemistry in olive flounder, Paralichthys olivaceus (Temminck et Schlegel)

Identification of potential fish stocks and lifetime movement patterns of Mugil liza Valenciennes 1836 in the Southwestern Atlantic Ocean

This paper characterizes the pattern of ectoparasite and endoparasite communities in an assemblage of 35 sympatric fish from different trophic levels in a tributary from the Amazon River system, northern Brazil. In detritivorous, carnivorous, omnivorous and piscivorous hosts, the species richness consisted of 82 ectoparasites and endoparasites, but protozoan ectoparasites such as Ichthyophthirius multifiliis, Piscinoodinium pillulare and Tripartiella sp. were dominant species predominated, such that they were present in 80% of the hosts. The taxon richness was in the following order: Monogenea > Nematoda > Digenea > Crustacea > Protozoa > Acanthocephala = Cestoda > Hirudinea. Among the hosts, the highest number of parasitic associations occurred in Satanoperca jurupari, Aequidens tetramerus, Hoplerythrinus unitaeniatus, Hoplosternum littorale, Cichlasoma amazonarum, Chaetobranchus flavescens, Squaliforma emarginata, Chaetobranchopsis orbicularis and Hoplias malabaricus. A weak positive correlation between ectoparasite abundance and length of the hosts was observed. Ectoparasite communities of detritivorous, carnivorous and omnivorous hosts were similar, but these differed from the communities of piscivorous hosts. Larval endoparasite species with low host specificity were the main determinants of the parasite infracommunity structure of the fish assemblage. Fish assemblage had few species of helminth that were specialist endoparasites, while many were parasites at the larval stage, infecting intermediate and paratenic hosts. Finally, carnivorous and omnivorous hosts harbored endoparasite communities that were more heterogeneous than those of detritivorous and piscivorous hosts. This result lends supports to the notion that the feeding habits of the host species are a significant factor in determining the endoparasites fauna.

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Patterns of the parasite communities in a fish assemblage of a river in the Brazilian Amazon region.

Diseases of Marine Animals Transmissible to Man

Formalin is an effective chemotherapeutic agent for combating several infectious conditions affecting fish of aquacultural importance and ornamental fish. It is applied as bath, flush or flowing treatment method and has proved to be effective against a variety of fish parasites and microbes. The toxicity of formalin on the behavior and respiration of the popular aquarium Zebra fish Danio rerio was evaluated 96 hour LC50 value was found to be 30ppm. Abnormal behavior and swimming movements, reduced opercular beats, increased mucus secretion and mortality were recorded due to formalin toxicity on zebrafish. Oxygen consumption of zebrafish exposed to sub-lethal concentration of formalin showed a time dependent decrease with 62.4% reduction at the end of 96 hours. The need for judicious use of fish chemotherapeutants like formalin and their impact on fish life are discussed.

Toxicity of formalin on behaviour and respiration in Danio rerio

The prevalence and mean intensity of metazoan parasite infection, the community characteristics (richness index, dominance index, evenness index and Shannon index of diversity) and the qualitative similarity of the metazoan parasite fauna among the species and families of the fishes were determined of 13 fish species of freshwater fishes of Kerala belonging to seven families. The metazoan parasite fauna of this geographical area is very diverse; it consisted of 33 species of parasites belonging to seven major taxa: ten species of Monogenea, nine Digenea, two Cestoda, six Nematoda, three Acanthocephala, two Copepoda and one Isopoda. Prevalence of infection ranged from 32.9% (Puntius vittatus) to 87.1% (Mystus oculatus) and mean intensity from 3.8 (Puntius vittatus) to 27.6 (Aplocheilus lineatus). The infra- and component communities of parasites were somewhat characteristic. The dominance pattern of the major taxa was in the order Digenea > Nematoda > Monogenea = Acanthocephala > Cestoda = Copepoda > Isopoda. Macropodus cupanus harboured the richest fauna and Puntius vittatus had the least rich fauna. The parasite fauna of A. lineatus was the most heterogeneous and that of M. cavasius, the most homogeneous. The diversity of the parasite fauna was the greatest in M. cavasius and the least in A. lineatus. The parasite faunas of A. lineatus and M. cupanus and of M. cavasius and M. oculatus were similar. However, in spite of the taxonomic nearness and the similarity of the habits and habitats of the four species of cyprinids (P. amphibius, P. filamentosus, P. sarana and P. vittatus), their parasite fauna were qualitatively very dissimilar–of the seven species of parasites encountered in them only one was shared by the four host species. The cyprinid, Rasbora daniconius, had its own characteristic component community of parasites consisting of six species none of which was shared by the other four cyprinids. The richest parasite fauna was that of the family Cyprinidae followed by that of Channidae and the poorest of Belonidae. The most homogeneous parasite fauna was that of Bagridae and the most heterogeneous that of Cyprinodontidae. The parasite fauna of Cyprinodontidae and Belontidae were qualitatively very similar. The results indicate that the freshwater fishes of the southwest cost of India harbour a rich and diverse metazoan parasite fauna, which is as rich and diverse as that of the marine fishes of this area. The results also suggest that carnivorous/omnivorous fish species harbour richer and more heterogeneous component communities of parasites than herbivorous species implying that the feeding habits of fishes is a major factor deciding their parasite faunas.

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Community ecology of the metazoan parasites of freshwater fishes of Kerala

Exposure of fishSarotherodon mossambicus (Peters) for 24 h to 80 ppm formalin induced lowering of total erythrocyte count and increase in haemoglobin and haematocrit. Erythrocyte constants and indices of exposed fish were higher than of the control fishes. The sum total of the effect of sublethal concentration of formalin on the peripheral blood ofSarotherodon mossambicus was macrocytosis and hyperchromia.

S. Radhakrishnan

Papers

Community ecology of the metazoan parasites of freshwater fishes of Kerala

Haematological effects of sublethal concentration of formalin onSarotherodon mossambicus (Peters)