Studies on the growth of Ophicephalus striatus Bloch

Summary Growth ofOphicephalus striatus was studied from zones on the scales as these were found to be suitable for age determination. Lenght estimates obtained from the scale reading were further substantiated by back-calculations. Thevon Bertalanffy equation was employed to find out theoretical values of length in respect of various year classes. The theoretical values agreed with the observed values very closely.Length-weight relationship showed that the weight of fish increases slightly faster than the cube of the length. Thevon Bertalanffy equation gave a good fit to weight-age data.     

The growth of the freshwater murrel,Ophicephalus punctatus Bloch

Summary The growth of O. punctatus has been studied from the zones on the opercular bones and scales. Size estimates obtained from the opercular bones and scales were further substantiated by length frequency distribution and back-calculations. A close agreement in length-age relationship was obtained by various methods. These observations provide adequate evidence towards the validity of age determination in O. punctatus.Growth rate differs markedly in the two sexes. Males grow faster than the females. To study the changes in length with age, von Bertalanffy growth equation and Gompertz curve were used. The theoretical lengths obtained from the von Bertalanffy equation agreed very closely with the observed lengths.There is sexual difference in the weight-length relationship of O. punctatus. Modal weight of each year class obtained according to age reading showed that growth in weight is faster in males. The theoretical growth equation gives a good fit for weight-age data. O. punctatus is generally a fish of the impounded waters. The interrelationship between pond environment and growth characteristics has been discussed.     

Serological examination of a rhabdovirus isolated from snakehead (Ophicephalus striatus) in Thailand with ulcerative syndrome

A rhabdovirus has been isolated from snakehead (Ophicephalus striatus) in Thailand showing an ulcerative syndrome. The virus did not exhibit any serological relationship to VHSV, IHNV, RVC, PFRV or EVX.

Zusammenfassung

Serologische Untersuchung eines Rhahdovirusisolates vom Schlangenkopffisch (Ophicephalus striatus) mit ulcerativem Syndrom in Thailand
Von einem Schlangenkopffisch (Ophicephalus striatus) mit dem ulcerativem Syndrom wurde ein Rhabdovirus in Thailand isoliert, das keine serologische Verwandtschaft zu VHSV, IHNV, RVC, PFRV und EVX aufweist.

Résumé

Examen sérologique d'un rhabdovirus isolé de Ophicephalus striatus avec syndrome ulcératif en Thaïlande
En Thaïlande un rhabdivirus a été isolé de Ophicephalus striatus montrant un syndrome ulcératif. Le virus ne montrait aucune relation sérologique avec VHSV, IHNV, RVC, PFRV ou EVX.     

Food selection and growth of young snakehead Channa striatus

Food selection and growth of young snakehead Channa striatus were studied in the laboratory and in a field trial. In the laboratory, first-feeding snakehead larvae of 6–7 mm total length (TL) with a mouth opening of 0.55 mm selected for Artemia nauplii, and against formulated feed. Fish began feeding on formulated feed at 12mm TL when their mouth width reached 1.0mm. In both laboratory and field trials, snakehead diets changed as fish size increased. For fish 15–20 mm TL, cladocerans and copepods were 96.5% of their diet. With fish 30–40 mm TL, zooplankton consumption was greatly reduced while benthic organism consumption increased. Fish 45–50 mm TL fed exclusively on benthic invertebrates. Diet shift from zoo-plankton to benthic invertebrates was not due to reduced zoo-plankton availability, but was instead related to changes in gill raker structure. Low density of benthic invertebrates in the field trial caused reduced fish growth rates when fish switched diets from zooplankton to benthos. Our results indicate that snake-head can take Artemia nauplii as a larval starter food, then accept formulated feed at ≥12 mm TL. Zooplankton can serve as food for snakehead < 40 mm, but formulated feed should be provided for larger fish which are unable to catch zoo-plankton.     

Horizontal transmission of epizootic ulcerative syndrome (EUS)-associated virus in the snakehead Ophicephalus striatus under simulated natural conditions

Natural transmission of the epizootic ulcerative syndrome (EUS) was conducted on na?ve snakeheads Ophicephalus striatus (also known as Channa striata) kept (A) in aquifer water, (B) in lakewater, (C) cohabiting with EUS snakeheads in lakewater, and (D) cohabiting with apparently healthy snakeheads in lakewater during the 1994 to 1995 EUS season. The results showed that EUS-like lesions developed in 6 to 14 d among na?ve snakeheads cohabiting with EUS snakeheads and with apparently healthy snakeheads in lakewater (Treatments C and D). Among na?ve fish exposed to lakewater (Treatment B), similar lesions developed in 16 to 21 d, while na?ve fish in aquifer water (Treatment A) did not develop EUS-like lesions. EUS signs began as Grade I (slight) lesions that gradually progressed to Grades III-IV (severe) 3 to 5 d from lesion onset, similar to the naturally affected EUS fish. The virus was recovered from some but not all naturally EUS-affected snakeheads, snakeheads with healing lesions and apparently healthy snakeheads, but not from na?ve snakeheads. The results provide evidence of a waterborne horizontal transmission of the EUS-associated virus. This is the first report of a successful horizontal transmission of the EUS-associated virus from apparently healthy snakeheads to na?ve fish under natural conditions and of virus recovery in tissue culture from naturally exposed experimental fish.     

Four New Species of Myxosporidia from the Indian Fresh Water Fish Ophicephalus punctatus Bloch

SYNOPSIS. Four new species of Myxosporidia have been described from Ophicephalus punctatus , a fresh water fish of North India: Myxobolus aligarhensis n. sp., M. ophicephali n. sp., Unicauda basiri n. sp., and Henneguya zahoori n. sp. Observations have been made on some stages of their life-cycle other than the spores.     

A new record ofAchlya klebsiana from snakehead,Channa striatus,with fungal infection in Myanmar

This is the first record of the discovery in Myanmar ofAchlya klebsiana, belonging to the family Saprolegniaceae.     

Babesiosoma ophicephali n. sp. from the Freshwater Teleost Ophicephalus punctatus Bloch

SYNOPSIS. Babesiosoma ophicephali n. sp. (Babesiidae; Haemosporidia), from the red blood cells of the freshwater teleost fish Ophicephalus punctatus Bloch, collected from suburbs of Calcutta, is described. Giemsa-stained films of blood from the caudal region of 20 fishes were examined, and 2 fishes were found to be infected. The genus Babesiosoma is described for the first time in India. The systematic position of the parasite is discussed in detail.     

Seasonal changes in the biochemical composition of the freshwater murrel,Ophicephalus punctatus Bloch

Summary Seasonal variations in various biochemical constituents in the tissues of Ophicephalus punctatus showed that. the fat content in the muscle was highest during November–January and lowest during June–October. Liver contained more fat than the muscle and its seasonal cycle was marked by two well defined peaks. Changes in the ovarian fat were also well defined seasonally. The moisture content in all the tissues varied inversely with the fat. Protein values in different tissues did not show as much fluctuations as fat. In muscle, protein remained high throughout the year except in January. In liver and gonads very low protein values were recorded during the winter months. Seasonal changes in the ash content were not very well marked in any of the three tissues.The seasonal variations in all the biochemical constituents seem related to the feeding intensity of the fish and the maturation of its gonads. Maximum and minimum values of fat fell in accordance with the high and low food intake. In the pre-spawning phase, more fat was stored in the muscle at first but subsequently the fat was mobilized in the liver and finally in the gonads. Peak ripeness was associated with an accumulation of greater protein and fat in the gonads (ovaries). During the spawning months the various constituents were depleted and the post-spawning phase of the fish was marked by minimal values of most of the biochemical constituents, excepting moisture and ash.     

Seroprevalence of Toxoplasma gondii in cats from Colombo, Sri Lanka

Cats are essential in the life cycle of Toxoplasma gondii because they are the only hosts that can excrete the environmentally resistant oocysts in nature. Nothing is known of the prevalence of Toxoplasma gondii in cats from Sri Lanka. Serum samples from 86 cats from Colombo, Sri Lanka, were tested for antibodies to T. gondii using the modified agglutination test; antibodies were found in 26 (30.2%) cats with titers of 1:25 in 4, 1:50 in 4, 1:100 in 3, 1:400 in 2, 1:800 in 3, 1:1,600 in 4, and 1:3,200 or higher in 6 cats. Seropositivity increased with age and was higher in stray cats versus pet cats. This is the first report of seroprevalence of T. gondii in cats from Sri Lanka.     

Achievement of reproductive intentions in Sri Lanka, 1982-1985: a longitudinal study.

The achievement or reproductive intentions of Sri Lankan women was examined by using longitudinal data for the period 1982-85. Aggregate consistency between reproductive intentions and behavior was almost perfect, but at the individual level there were inconsistencies. Among those who wanted to have no more children, 23 per cent reported a birth in the intersurvey period of 3 years and 2 months, while failures to have a wanted birth stood at 36 per cent. There was a clear declining trend in the former type of inconsistencies in Sri Lanka, but the latter type has increased, possibly due to a continuing decline in family size ideals or due to deferred childbearing. Even though inconsistencies existed, expressed fertility intentions in 1982 significantly influenced the fertility outcome. The study also has a methodological focus on whether to include sterilized women when fertility intentions and behavior are examined longitudinally, but no specific problems were found with their inclusion. Results indicate that, apart from the intention variable, age, marital duration, family size, and education of husband and wife variables all influenced fertility in the follow-up period.     

Seasonal variations of calcium and phosphorus in the juveniles of freshwater murrel,Ophicephalus punctatus Bloch

Summary In young O. punctatus seasonal variations in calcium and phosphorus showed a direct correlation. Both of these minerals showed a bimodal cycle. High values occurred during pre- and post-monsoon months and low values during winter and monsoon months. These changes seem to be related to the feeding intensity and growth of the fish.     

Characterization of Bioactive Actinomycetes Isolated from Kadolkele Mangrove Sediments,Sri Lanka

Exploring untapped microbial potentials in previously uncharted environments has become crucial in discovering novel secondary metabolites and enzymes for biotechnological applications. Among prokaryotes, actinomycetes are well recognized for producing a vast range of secondary metabolites and extracellular enzymes. In the present study, we have used surface sediments from ‘Kadolkele’ mangrove ecosystem located in the Negombo lagoon area, Sri Lanka, to isolate actinomycetes with bioactive potentials. A total of six actinomycetes were isolated on modified-starch casein agar and characterized. The isolates were evaluated for their antibacterial activity against four selected bacterial strains and to produce extracellular enzymes: cellulase, amylase, protease, and lipase. Three out of the six isolates exhibited antibacterial activity against Staphylococcus aureus, Escherichia coli, and Bacillus cereus, but not against Listeria monocytogenes. Five strains could produce extracellular cellulase, while all six isolates exhibited amylase activity. Only three of the six isolates were positive for protease and lipase assays separately. Ac-1, Ac-2, and Ac-9, identified as Streptomyces spp. with the 16S rRNA gene sequencing, were used for pigment extraction using four different solvents. Acetone-extracted crude pigments of Ac-1and Ac-2 were further used in well-diffusion assays, and growth inhibition of test bacteria was observed only with the crude pigment extract of Ac-2. Further, six different commercially available fabrics were dyed with crude pigments of Ac-1. The dyed fabrics retained the yellow color after acid, alkaline, and cold-water treatments suggesting the potential of the Ac-1 pigment to be used in biotechnological applications.     

Seasonal variations in the cyanophils of the pituitary gland in correlation with reproductive cycle of Channa striatus (Bloch)

Seasonal changes in the cyanophils of the proximal pars distalis of the pituitary gland of C. striatus are conspicuous, and they closely follow the reproductive cycle. There is a poor concentration of their glycoproteinaceous contents during the resting phase and higher concentration during the maturation phase. The cyanophils also undergo a process of hypertrophy, granulation, followed by degranulation and vacuolisation during the spawning phase. They almost empty their contents during the post-spawning period.     

Isolation and molecular characterization of Toxoplasma gondii from chickens from Sri Lanka

The prevalence of Toxoplasma gondii in free-ranging chickens is a good indicator of the prevalence of T. gondii oocysts in the soil because chickens feed from the ground. The prevalence of T. gondii in 100 free-range chickens (Gallus domesticus) from Sri Lanka was determined. Antibodies to T. gondii were assayed by the modified agglutination test (MAT). Antibodies were found in 39 chickens with titers of 1:5 in 8, 1:10 in 8, 1:20 in 4, 1:40 in 5, 1:80 in 5, 1:160 in 5, 1:320 in 2, 1:640 or more in 2. Hearts and brains of 36 chickens with MAT titers of 1:5 or more were bioassayed in mice. Tissues of 3 chickens with doubtful titers of 1:5 were pooled and fed to a cat; the cat shed T. gondii oocysts in its feces. Tissues from 61 chickens with titers of less than 1:5 were pooled and fed to 2 T. gondii-free cats; the cats did not shed oocysts. Toxoplasma gondii was isolated from 11 of 36 seropositive chickens by bioassay in mice. All 12 T. gondii isolates were avirulent for mice. Genotyping of 12 isolates using the SAG2 locus indicated that 6 were type III, and 6 were type II. This is the first report of genetic characterization of T. gondii from any host in Sri Lanka.     

Pollen morphology of some selected plant species from Horton Plains,Sri Lanka

The pollen morphology of four species: Gaultheria leschenaultii (Ericaceae), Psychotria zeylanica (Rubiaceae), Rubus leucocarpus (Rosaceae) and Symplocos bractealis (Symplocaceae) from Horton Plains, Sri Lanka was investigated using LM and SEM. Psychotria zeylanica is endemic to Sri Lanka and the other three taxa are common in Horton Plains. Gaultheria leschenaultii has tetrads with 3-colporate, coarsely granular to granulo-rugulate pollen grains; in the polar region and at the colpus margin the exine is smooth with micro-rugulate structure. Psychotria zeylanica has 3- (or 4-) colporate, reticulate-spinulose to granular pollen grains. Rubus leucocarpus has 3-colporate, striate-perforate pollen grains and Symplocos bractealis has 3- (or 4-) colporate pollen grains with a verrucate-perforate exine. Pollen grains of these four species are very indicative of human impact and palaeoclimate.