G. I. Izvekova

Infection of mollusks and fish by the trematode Apophallus muehlingi (Jagerskiold, 1898) and its interrelations with intermediate hosts

In the Rybinsk Reservoir (Upper Volga basin), a sharp decrease in the occurrence of Apophallus muehlingi (Jagerskiold) parthenites was found in the population of the Ponto-Caspian snail Lithoglyphus naticoides Pfeiffer in 2009–2010. In the muscles of cyprinid underyearlings (ide Leuciscus idus (L.) and dace Leuciscus leuciscus (L.)), interspecific differences in protein content were revealed following their infection by metacercariae in the experimental environment. The helminth infection caused an increase in glycogen content in both fish species. A reduction of motor activity induced by muscle damage might be the main reason for the observed changes in biochemical characteristics.

Occurrence of partenites in mollusks and the influence that metacercaria of Apophallus muehlingi (Jagerskiold, 1898) and Posthodiplostomum cuticola (Nordmann, 1832) has on some biochemical parameters in fish

A heavy parasitic load from trematode partenites of Apophallus muehlingi (Jagerskiold, 1898) was observed in the mollusk population of Lithoglyphus naticoides (Pfeiffer) after its natural invasion into the Rybinsk Reservoir. An elevated concentration of glycogen was detected in the muscles of infected fish, both in the natural populations and under experimental conditions. Interspecific differences were found for the protein concentrations when elevated concentrations were observed in the muscles of the infected roach, and no differences were discovered for the goldfish (both infected and parasite-free). The ties between the biochemical parameters and motor activity are discussed for the infected fish.

Diversity of microbial communities of the intestinal mucosa and intestinal contents of fish from Lake Chany (Western Siberia)

The diversity of microbial communities associated with the intestinal mucosa and the intestinal contents of fish with different nutritional profiles have been investigated. Differences in the intestinal microbiota of fish with different dietary preferences have been revealed using group-specific primers for the main large taxa of bacteria. Representatives of the phyla Planctomycetes, Vernicomicrobia, and Cyanobacteria have been detected in the intestinal contents of all investigated nonpredatory (crucian carp, roach, and dace) and predatory (pikeperch, pike, and perch) fish. Representatives of the phylum Firmicutes were detected in the intestinal mucosa and intestinal contents of predatory fish species, but not in those of the nonpredatory fish.

Activity of digestive enzymes and distribution of the trematode Bunodera luciopercae (Müller) in the intestine of juvenile perch infected with plerocercoids of Triaenophorus nodulosus (Pallas)

It is revealed that the infection of Triaenophorus nodulosus (Pallas) with plerocercoids affects both the activity of digestive hydrolases and the localization of trematodes in the intestine of juvenile perch. Infected fish exhibit a higher proportion of Bunodera luciopercae (Müller) marites in the posterior intestinal segment compared to noninfected specimens. Moreover, in young fish with cestode-induced liver damage, the activities of digestive hydrolases decreases, particularly in the anterior segment of the digestive tract.

Hydrolytic activity of symbiotic microflora enzymes in pike (Esox lucius L.) intestines

This study has revealed the existence of microflora which is, to different degrees, associated with the intestinal mucosa of pike. A total of 82 bacterial strains have been isolated. These microorganisms produce enzymes that hydrolyze the major food substrates (proteins and carbohydrates). These enzymes are produced by the pool of various microorganisms living in the intestines, as well as by separate strains isolated in pure cultures. These strains produce enzymes with different levels of activity. Most of the isolated strains (68%) produce proteases. The calculated values of the C/P factor (the ratio of carbohydrase to protease activity) indirectly testify to the autochthonous nature of the microflora associated with the intestinal mucosa of pike. Presumably, the contribution that the microflora enzymes make to the enzymatic activity of the pike intestine is substantial, but it is difficult to estimate now.

The activity of digestive enzymes of the pike Esox lucius L. Infected with the cestode Triaenophorus nodulosus (Pallas)

It has been shown that protease activity increases and amylase activity decreases from the first to the fifth intestinal segment of pike, while lipase and esterase activities vary within fairly narrow limits. The level of proteolytic enzyme activities increases in pikes infected with Triaenophorus nodulosus (Pallas), but the invasion has no effect on amylase, lipase, or esterase activities. The T. nodulosus infection of pike had no substantial influence on glycogen or protein content in the hepatopancreas of fish. However, it was noted that the ratio of protease and amylase activities in the intestines changed toward an increase in the share of proteases and the share of protein in the hepatopancreas of infected fish.

Lysozyme content in the organism of pike infected with cestodes

It was found that parasitizing Triaenophorus nodulosus (Pallas, 1781) affects the lysozyme content in the intestinal mucosa of pike. It is suggested that the parasite suppresses lysozyme production immediately in its locality, which may favor its successful dwelling in the hosts’ intestines. The insignificant variations of lysozyme content in the liver and blood serum of pike in the spring, summer, and autumn, on the one hand, and pronounced changes in this characteristic in the intestinal mucosa, on the other, make it possible to consider that the latter changes are related to the presence of a parasite in the intestine.

Proteinase Activity in the Intestine of Ruff Gymnocephalus cernuus (L.) (Pisces) Depending on the Sum Length of Cestodes Proteocephalus cernuae (Gmelin) Parasitizing the Gut

It is revealed that the infection of ruff with cestodes Proteocephalus cernuae affects the activity of its intestinal proteolytic enzymes. The influence of cestodes on the activity of intestinal proteinases depends on the sum length of the worms occupying the gut. Proteinase activity decreases at a smaller total length of the worms and increases at larger total length, with serine proteinases being mostly involved. The essential share of activity is presented with metalloproteinases, which can indirectly evidence the important role of microbiota in the digestion of ruff. The small share of cysteine proteinases in both uninfected and infected fish may indicate minor intestinal damages caused by the attachment structures of cestodes.

Seasonal changes in pH values in the intestine of fish from Lake Chany (West Siberia)

The pH values are determined in the digestive tract of nine fish species in Lake Chany (West Siberia). Seasonal changes in pH values are found along the intestine of fish. Intestinal pH values decrease in summer as the temperature rises and increase during the cold season as the temperature drops. The hypothesis has been advanced that temperature-dependent pH changes in the intestine may serve as a regulatory mechanism that maintains the activity of hydrolytic enzymes at the level required for successful digestive processes due to some adaptive modifications of the medium where these enzymes operate.

Effect of metacercarial infection on some physiological traits of roach underyearlings

The influence of infection with trematode metacercariae on some physiological and biochemical characteristics has been studied in the underyearlings of roach. The parameters that were studied are found to depend on the parasite localization. The body length and weight values of infected underyearlings with muscular localization of metacercariae are lower than in uninfected fish and the glycogen content is higher. On the contrary, individuals with infected eyes display greater body length and weight when coupled with lower glycogen content in comparison with parasite-free fish. The infection with metacercariae has no effect on the activity of glycosidases. Different glycogen levels in the underyearlings with muscular and ocular localization of metacercariae are presumably linked with the locomotor activity of the fish.