Application of probiotics in trout farms in North-West Russia

In recent years, various probiotic and immunomodulating drugs have been actively used in aquaculture. The group of probiotics includes preparations of the Vetom series, created on the basis of the spore-forming bacteria Bacillus subtilus and Bacillus licheniformis. Recently, a large positive experience has been accumulated in the use of Vetom 1.1 in fish farming. The drug is actively used in trout cage farms in Karelia and the Leningrad region. Vetom 1.1 was administered orally with food at a dosage of 50–75 mg/kg ichthyomass per day for 10 days. An improvement in the epizootic state of fish was observed: regeneration of the affected fins and branchial epithelium, normalization of the blood state. Biocomplex Multibacterin (previously in research — Multibacterin OMEGA-10) is a functional food based on lactobacillus (Lactobacillus acidophilus). The drug has a high antagonistic activity against microorganisms — pathogens of bacterial etiology, stimulates the synthesis of immunoglobulins, improves metabolic processes in the body of animals, and stimulates regeneration processes. Multibacterin is recommended for introduction into trout feed in case of toxicosis, bacterial and fungal infection at a dosage of 0.1 ml/kg of ichthyomass for 10 days. The study of the effect of the Multibacterin biocomplex on the state of rainbow trout of different age groups, reared under different conditions, was carried out. With the introduction of the probiotic Multibacterin into the feed, a decrease in the death of fish was noted to 9.5% versus 20% in the control. An improvement in the state of the branchial epithelium was revealed, and the development of the regenerative process on the affected branchial lobes was noted. These preparations help to maintain the immunity of fish and can be recommended for use in aquaculture.

Ultrastructure of the gills ciliary epithelium of Limnoperna fortunei (Dunker 1857), the invasive golden mussel

Background Limnoperna fortunei is a bivalve mollusk originally from southern Asia that invaded South America in the 1990's. Its high efficiency in pumping and filtering water and the capacity to promote strong adhesion to different substrates allowed the adaptation of this invasive species, associated with several environmental and economic damages. A deep understanding of the biology and ecology aspects of L. fortunei is necessary to outline effective strategies to manage its invasion. Mollusk gills are important structures responsible for several biological functions including breathing and feeding. In this work, we characterized the ultrastructure of L. fortunei gills and its ciliary epithelium using transmission and scanning electron microscopy. This is the first report of the L. fortunei gills ciliary epithelial cells visualized with high resolution and detailed morphology. Results The analysis showed a highly organized and large amount of ciliary structures (frontal cilia, laterofrontal cilia, and lateral cilia) on the entire length of the branchial epithelium. Mitochondria, smooth endoplasmic reticulum and glycogen granules were abundantly found in the epithelial cells of the gills, suggesting that all this energetic apparatus could be related to the morpho-functional structure of the cilia. Vesicles possibly containing mucus could also be observed in these cells, suggesting that they might be related to L. fortunei mechanism of selection and/or rejection of captured particles suspended in water. Conclusions Our data suggest the mechanism used by this mollusk for particles capture and selection, which could contribute to a better understanding of important aspects of invasion and decide on more efficient and economic strategies of population control.

Ultrastructure of intracytoplasmic Rickettsia-like infection of the gills of the teleost Archosargus probatocephalus (Sparidae) in northeastern Brazil

A histopathological survey was conducted to investigate the presence of microparasites in fish Archosargus probatocephalus in a river near Maceió, Brazil. Light microscope observations of fragments of gill showed the presence of small cysts containing numerous myxospores that were morphologically identified as Henneguya. Transmission electron microscopy observations further revealed several gill cells containing groups of prokaryotic cells within large cytoplasmic vacuoles. Each infected host cell displayed a single vacuole containing a variable number of Rickettsia-like cells (up to 11), some of which presented the dumbbell shape characteristic of binary fission. The Rickettsia-like cells were pleomorphic, without a nucleus and with chromatin dispersed in the cytoplasm. They had a thin electron-dense wall of Gram-negative type. The morphology of these prokaryotic was similar to those of the order Rickettsiales and was described as a Rickettsia-like organism. Histopathological evaluation showed that several vacuole membranes had a lysed appearance. Some had ruptured, thus allowing direct contact between the Rickettsia-like organism and the cytoplasm of the host cell. The rupturing of the branchial epithelium may have contributed towards reduction of the surface area of the gills, but it is not possible to say that this was the cause of the host’s death.

Hormonal regulation of aquaporin 3: opposing actions of prolactin and cortisol in tilapia gill

Aquaporins (Aqps) are expressed within key osmoregulatory tissues where they mediate the movement of water and selected solutes across cell membranes. We leveraged the functional plasticity of Mozambique tilapia (Oreochromis mossambicus) gill epithelium to examine how Aqp3, an aquaglyceroporin, is regulated in response to osmoregulatory demands. Particular attention was paid to the actions of critical osmoregulatory hormones, namely, prolactin (Prl), growth hormone and cortisol. Branchial aqp3 mRNA levels were modulated following changes in environmental salinity, with enhanced aqp3 mRNA expression upon transfer from seawater to freshwater (FW). Accordingly, extensive Aqp3 immunoreactivity was localized to cell membranes of branchial epithelium in FW-acclimated animals. Upon transferring hypophysectomized tilapia to FW, we identified that a pituitary factor(s) is required for Aqp3 expression in FW. Replacement with ovine Prl (oPrl) was sufficient to stimulate Aqp3 expression in hypophysectomized animals held in FW, an effect blocked by coinjection with cortisol. Both oPrl and native tilapia Prls (tPrl177 and tPrl188) stimulated aqp3 in incubated gill filaments in a concentration-related manner. Consistent with in vivo responses, coincubation with cortisol blocked oPrl-stimulated aqp3 expression in vitro. Our data indicate that Prl and cortisol act directly upon branchial epithelium to regulate Aqp3 in tilapia. Thus, within the context of the diverse actions of Prl on hydromineral balance in vertebrates, we define a new role for Prl as a regulator of Aqp expression.

Effects of the organophosphorous methyl parathion on the branchial epithelium of a freshwater fish Metynnis roosevelti

Gills are vital structures for fish, since they are the main site for gaseous exchange as well as partially responsible for osmorregulation, acid-basic balance, excretion of nitrogenous compounds and taste. Chemicals in the water may alter the morphology of branchial cells of fish that are, therefore, a useful model for environmental impact and ecotoxicology studies. In order to investigate the effects of an organophosphorous compound, methyl parathion, on the gills of the fish, samples of Metynnis roosevelti were exposed to lethal (7ppm) and sublethal (1ppm) doses of Mentox 600 CE. Through light and scanning electron microscopy, shrinking of the branchial epithelium, followed by detachment and hyperplasia were observed. Externally, the branchial filaments presented the gradual disappearance of microridges. Even in sublethal doses, the organophosphorous reduced the health and fitness of these fish, as consequence of secondary effects derived from changes in the branchial epithelium, impairing oxygenation and ionic balance of the organism.

Immunolocalisation of aquaporin 3 in the gill and the gastrointestinal tract of the European eel Anguilla anguilla (L.)

SUMMARY The expression of a putative water channel protein, aquaporin 3 (AQP-3),has been localised within branchial and intestinal tissues from the `silver'life stage of the European eel Anguilla anguilla, using a specific polyclonal antibody directed against the C-terminal of the amino acid sequence. Western blots using the AQP-3 antiserum identified the presence of a major immunoreactive protein of 24 kDa in extracts of gills from both freshwater (FW) and 3 week seawater (SW)-acclimated eels. SW acclimation induced a 65 % reduction in AQP-3 protein abundance in the gill extracts. AQP-3 immunoreactivity was apparent throughout the branchial epithelium from both FW and SW-acclimated fish, but especially so within the chloride cells,which also stained heavily with specific antisera for the β-subunit of the Na, K-ATPase. AQP-3 immunoreactivity not only colocalised with Na,K-ATPase within the basolateral tubular network but also stained the apical regions of the chloride cell where Na, K-ATPase was absent. Although there were no obvious differences in expression between the chloride cells of FW and SW-acclimated fish, considerably higher intensities of immunoreactivity were apparent near the periphery of the non-chloride cells of FW fish, especially within cells forming the base of the primary filaments and the branchial arch. AQP-3 immunoreactivity was also detected in intra-epithelial macrophage-like cells within the intestine of FW and SW-acclimated eels and in the mucous cells of the rectal epithelium of SW-acclimated fish. These results suggest that AQP-3 may play an important functional role in osmoregulation the teleostean gill but is unlikely to be responsible for the increases in intestinal water absorption that occur following SW acclimation.