Mikhail Solovyev

A comparative study on microbiota from the intestine of Prussian carp (Carassius gibelio) and their aquatic environmental compartments, using different molecular methods

The aim of this study was to evaluate, via various molecular methods, the possible correlations between microbial community structure of Prussian carp and the environmental compartments of their habitat.

Variations in the activity of digestive enzymes along the intestine of the burbot Lota lota expressed by different methods.

The activities of major digestive hydrolases (proteases, amylase, lipase and esterases) along the intestine were studied in the burbot Lotalota (L.) using different methods of activity expression. The enzyme activities were determined both in the whole gut segments and in the isolated mucosa, and then expressed in terms of tissue mass and protein content in the samples. Further, the cumulative activities of these enzymes in the pyloric caeca were compared with those in the rest of the intestine to estimate the overall contribution of these regions to digestion. The data obtained suggest the essential role of the pyloric caeca in the digestion of the burbot. In addition, the variations in the pH values along the intestine and the changes in the enzyme activities with incubation temperature were examined. The study proved the method of enzyme activity expression to be a key factor influencing the outcome of the experiment.

Feeding habits and ontogenic changes in digestive enzyme patterns in five freshwater teleosts

Feeding habits and the activity of digestive enzymes (total alkaline proteases, α-amylase and lipase) from dace Leuciscus leuciscus, roach Rutilus rutilus, Prussian carp Carassius auratus gibelio, perch Perca fluviatilis and pikeperch Sander lucioperca fry were studied in the Malye Chany Lake-Kargat Estuary (western Siberia, Russia). The diet of fry from all studied species was mainly composed of chironomid larvae and zooplanktonic organisms (i.e. cladocera and copepoda), whereas carnivorous species such as P. fluviatilis and S. lucioperca also preyed on fry from other fishes while detritus and microalgae were also important in the diet of ommivorous species. When comparing diet similarity (Sørensen-Dice index, Q(S)) among fry at different stages of development, both omnivorous and carnivorous species showed a high level of similarity (0.67 < Q(S) < 0.89 and 0.73 < Q(S)< 0.89, respectively). Diet similarity values were in agreement with the overall digestive activity profile analysed by cluster analysis. Diet similarity suggested potential trophic competition when zooplanktonic and benthic prey began to decline towards autumn. The analysis of pancreatic digestive enzymes revealed a correlation among their activities and fry feeding habits with α-amylase:total proteases (A:P) values higher than 1 in omnivorous species and lower (A:P ≤ 1) in carnivorous species.

pH values and activity of digestive enzymes in the gastrointestinal tract of fish in Lake Chany (West Siberia)

Optimum pH of various digestive enzymes and physiological pH values were determined in the gastrointestinal tract of fish species, such as goldfish Carassius auratus gibelio, ide Leuciscus idus, wild carp Cyprinus carpio, perch Perca fluviatilis, and zander Sander lucioperca. Physiological values of pH in the stomach of perch and zander and in different parts of the intestine of all studied fish species range within 3.5–4.5 and 6.5–7.2, respectively. The maximum values of the activity of alkaline protease and nonspecific lipase and esterase are recorded at pH 8–9; the maximum acid protease activity is recorded at pH 2–3. The optimum pH activity of alkaline protease and nonspecific lipase and esterase do not correlate with actual pH value in the digestive tract of fish. Two peaks of α-amylase activity are observed at pH 7 and 9.

DNA extraction protocols may influence biodiversity detected in the intestinal microbiome: a case study from wild Prussian carp, Carassius gibelio.

&NA; In this investigation, we examined the influence of different DNA extraction protocols on results obtained for intestinal microbiota of Prussian carp. We showed that significant differences were observed in numbers of reads, OTUs, Shannon index and taxonomic composition between two different DNA extraction protocols for intestine of Prussian carp (Carassius gibelio), and differences were also evident between microbial communities in the intestinal mucosa and intestinal content. Statistical analyses of 25 published articles also revealed a significant relationship between methods of DNA extraction and bacterial diversity in fish intestine of freshwater species. Microbial diversity, community structure, proportions of read numbers derived from each OTU and the total number of OTUs obtained by different DNA extraction protocols could lead to a bias in results obtained in some cases, and therefore researchers should be conservative in conclusions about community structures.

Dependence of pH values in the digestive tract of freshwater fishes on some abiotic and biotic factors

The values of pH in the digestive tracts of 20 freshwater fish species inhabiting various Russian Federation waterbodies were studied. Only in six species (Coregonus lavaretus, Coregonus migratorius, Catostomus catostomus, Carassius gibelio, Rutilus rutilus, Leuciscus leuciscus) out of 20 species, the differences in pH values between different regions of the intestine were significant. Feeding habits, feeding frequency, and gut fullness in fish affected pH values. Temperature was one of the most important factors affecting pH values. During cold seasons (spring and fall; average water temperature: 8–10 and 5–6○C, respectively), the pH values in fish guts were higher than that in the summer seasons(water temperature 22–25°C) for C. gibelio, Perca fluviatilis, Cyprinus carpio, L. leuciscus, and R. rutilus from the Chany Lake. Similar results (lower pH values in intestine at higher water temperatures) were also obtained for C. gibelio in warmer years in comparison to colder years in the same waterbody and in L. leuciscus and P. fluviatilis in the different waterbodies with different water temperatures. It is hypothesized that dependence of pH in fish gut on temperature may serve as a regulatory mechanism for maintaining the activities of hydrolytic enzymes at the required level for their successful functioning.

Physiological pH values in the digestive tract of perch Perca fluviatilis from different habitats

Physiological pH values are determined in the gastrointestinal tract of the perch Perca fluviatilis from lakes Chany and Baikal. Values of pH are detected to vary significantly along the digestive tract. Such factors as a segment of the digestive tract, presence/absence of food, season of the year, and habitat affect pH values. Environmental temperature is the main factor affecting pH values that is confirmed by the decrease in pH values upon water temperature rise in spring, lower pH values in summer compared to other seasons, and lower pH in fish from the waterbody (Lake Chany) with higher temperature of water.

Behaviour of Early Life Stages in the Siberian Sturgeon

In this chapter, field data and laboratory studies on the behaviour and development of Siberian sturgeon at early-life intervals have been reviewed and the available information assessed under two different points of view, the biological/ecological approach and the aquaculture one. In this context, data on sturgeon behaviour have been correlated to different ecologically relevant environmental factors that may play a role in the distribution, recruitment and survival of young fish in the wild. In addition, behavioural data have been also considered under a hatchery scope, since fish behaviour may help to define an explicit criterion to assess the quality and fitness of fish, detect abnormal situations during rearing and optimise culture conditions. Four behavioural phases (swimming-up, rheotactism, schooling and, foraging and active dispersal) are observed from hatching to the juvenile phase. Different behavioural patterns are associated with an early-life interval and might allow fish to occupy different river habitats, directly influencing their distribution, survival and recruitment. In hatchery conditions, these phases may be used for evaluating larval quality and the stage of development.

Weaning in Siberian Sturgeon Larvae

In this chapter we have revised the available information regarding feeding practices with Siberian sturgeon larvae from the onset of exogenous feeding to the early juvenile stage, data gathered from published studies and compared and/or complemented with current practices from French hatcheries. Different feeding strategies based on feeding larvae with inert diets (crumble or micropellets) or combining them with a period of feeding based on live preys (Artemia nauplii) is also discussed, since the transition to one feed to another is still a very critical moment for the life of the animal, which requires gradual and specific dietary protocols for the success of the process in terms of growth performance, survival and fry quality. Although Siberian sturgeon larval rearing may be considered easier when compared to other sturgeon and freshwater species, special attention is needed for optimizing larval feeding in order to maximize larval performance, since this phase of the productive cycle has a considerable impact on the economic profitability of the activity.

Diet and other environmental factors shape the bacterial communities of fish gut in an eutrophic lake

The aim of this work was to study the gut microbial diversity from eight species of wild fish with different feeding habits, digestive physiology (gastric vs agastric) and provide comparative structural analysis of the microbial communities within their environment (food items, water, sediments and macrophytes).