V. V. Kuz’mina

The influence of zinc and copper on the latency period for feeding and the food uptake in common carp, Cyprinus carpio L.

In order to know the effect of zinc and copper pollution on in fish feeding behavior, the latency period for feeding and food uptake of common carp, Cyprinus carpio L., yearlings were examined. It was shown that exposure to these metals (1 μmol/l) increased the search reaction time (the time taken to leave the starting chamber after its front wall was raised, t(1)), as well as latency period for feeding (t(2)). The significant increase of the first index was observed in 6h. In the presence of zinc the differences from the control were considerable within the period from 30 to 54 h. In the presence of copper, these differences remained significant throughout the time of observation. The second parameter increased in the course of the experiment, too. A significant increase of t(2) was noted already at 3h in the presence of both metals. The food uptake (the quantity of eaten midge larvae Chironomus sp for 3 min of observation) of fish in this condition gradually decreased significantly in 3h after the start of the exposure. At the end of the experiment, the food uptake decreased by 46% and 60% and feeding reaction rate increased by 93% and 114% as compared to the control in the presence of zinc and copper, respectively. These results show that fish latency period for feeding and the food uptake are useful as parameters for evaluating metal toxicity.

Influence of pH upon the activity of glycosidases and proteinases of intestinal mucosa, chyme and microbiota in fish

It is shown that amylolytic and proteolytic activity of the intestinal mucosa, the chyme and the intestinal flora in the fishes, zander Zanderlucioperca (L.), perch Perca fluviatilis L., bream Abramis brama (L.) and roach Rutilus rutilus (L.), belonging according to their feeding habits to different ecological groups at the same pH values as well as in the pH range from 5.0 to 10.0 considerably varies. The glycosidase pH optimum of the mucosa and intestinal microbiota is 7.0, whereas that of the chyme varies from 6.0 (in roach) to 8.0 (in bream). pH optimum of the mucosa proteinases in all fish species is 10.0, whereas that of the chyme and the bacterial flora can be observed in all the range of pH values.

[Activities of proteinases in invertebrate animals--potential objects of fish nutrition. Effects of temperature, pH, and heavy metals].

Differences in the degree of separate and combined effects of temperature, pH, and heavy metals (zinc, copper) on the trypsin-and chymotrypsin-like proteinase activities have been established in the whole body of some invertebrate animals—potential objects of fish nutrition: pond snail Lymnaeae stagnalis, orb snail Planorbarius purpura, zebra mussel Dreissena polymorpha, oligochaetes Tubifex sp. and Lumbriculus sp. in total, chironomid larvae Chironimus sp. and Ch. riparus, as well as crustacean zooplankton. It has been shown that enzymes of the potential prey at low temperature can compensate the low activity of intestinal proteinases of fish bentho- and planktophages.

Effect of Thyroid Hormones on Activity Dynamics of Enzymes of Intestinal Mucosa of Juvenile Roach Rutilus rutilus

The effect of thyroid hormones on activity dynamics of enzymes (proteinases and glycosidases) of intestinal mucosa of juvenile roach Rutilius rutilus was investigated. Application of substances increasing and decreasing the level of thyroid hormones in blood plasma significantly influences the growth rate and the activity of proteinases and glycosidases functioning in the intestinal mucosa. In most cases, the activity level of trypsin-like proteinases and the activity of glycosidases in the fish exposed to triiodothyronine were significantly higher than in the control. The activity level of chymotrypsin-like proteinases in fish form the group with exposure of exogenous triiodothyronine only in the end of the experiment surpassed the values of this parameter in the control fish. In the fish developing at deficiency of thyroid hormones, the growth rate and proteinases activity were significantly lower in comparison with the control.

The effects of geomagnetic storms on proteinase and glycosidase activities in fish intestinal mucosa

It has been demonstrated that the glycosidase activity of cyprinoid fishes (carp and crucian carp) exposed to a geomagnetic storm for up to 20 h considerably decreases; however, the proteinase activity is weakly altered (a statistically significant decrease in the enzyme activity has been observed only in fasting fish). An in vitro study of the effects of individual half hour intervals of the geomagnetic storm that correspond to the main and recovery phases on the same enzyme activities demonstrates the opposite trend. Independently of the experimental conditions, geomagnetic storms have been shown to influence the enzyme system of fasting fish negatively.

The effect of magnetic fields on the activity of proteinases and glycosidases in the intestine of the crucian carp Carassius carassius

It has been demonstrated by the example of the crucian carp (Carassius carassius) that a 1-hour stay of fish in a combined magnetic field with resonance parameters for calcium ions decreases the proteolytic and amylolytic activities of their intestinal enzymes. It has been found that a 1-hour exposure to a combined magnetic field with resonance parameters for potassium ions has almost no effect on the activity of proteinases, but it decreases the amylolytic activity. It has been noted that the activity of proteases and glycosidases is lower under hypomagnetic conditions. Upon the inversion of the vertical component of the geomagnetic field, the proteolytic activity of the intestinal mucosa in C. carassius decreases, while the amylolytic activity becomes higher compared to the control. Possible effects of magnetic fields on the activity of digestive hydrolases in fish are discussed.

The dependence on temperature and pH of the effects of zinc and copper on proteolytic activities of the digestive tract mucosa in piscivorous fish and their potential preys

The dependence of the effects of zinc and copper on the activities of proteinases of the stomach and intestinal mucosa on temperature and pH in four species of boreal piscivorous fish (pike Esox lucius, zander Zanderlucioperca, perch Perca fluviatilis and burbot Lota lota) as well as in some of their potential preys (kilka Clupeonella cultriventris, ruff Gymnocephalus cernuus, perch and roach Rutilus rutilus) was investigated. Species-specific differences of the effects of these heavy metals upon the activities of proteinases depending on temperature and pH were demonstrated. It was revealed that the stomach mucosa proteinases were more tolerant to the effects of the studied factors than the intestinal mucosa proteinases, especially true for pike. The effects of the heavy metals on the whole body proteinases of the fishes’ potential preys were mostly dependent on temperature than on pH. At pH 3.0, the negative action of zinc and copper on the fish digestive tract mucosa proteolytic activity to a considerable degree was compensated by the high activity of the hemoglobinlytic proteinases, probably, cathepsine D.

Effects of temperature, pH, and heavy metals (copper, zinc) upon proteinase activities in digestive tract mucosa of typical and facultative piscivorous fish

Species-specific differences and effects of natural (temperature, pH) and anthropogenic (zinc, copper) factors upon activities of casein-and hemoglobinlytic proteinases have been studied in the gut mucosa in pike (Esox lucius), zander (Stizostedion lucioperca), burbot (Lota lota) and perch (Perca fluviatilis). It is revealed that the intestine mucosa proteinase activities differ considerably from those ones in the fish stomach mucosa and that studied factors affect these activities to different extents. The stomach mucosa proteinases are most tolerant to the effects of studied factors, which is especially true for pike. The least tolerant are the intestine caseinlytic proteinases (except for the enzymes in perch). The effects of temperature, pH, and heavy metals depend on fish species, factors’ combinations (mono-factor, bi-factor, or multi-factor action) and on factor variability.

Influence of diurnal rhythms of feeding during intestine total amylolytic activity and activity of alkaline phosphatase in juvenile fish

The total amylolytic activity and activity of alkaline phosphatase in the intestine mucosa of larvae and fries of roach, blue bream, and perch change both during the process of individual development and during the day. Maximal intensities of juvenile feeding was observed primarily in the morning and evening hours. The pattern of diurnal alkaline phosphatase activity correlates to a greater extent to intensity of juvenile feeding, in comparison to the pattern of total amylolytic activity. In planktivorous blue bream, such regularity is more pronounced than in benthivorous roach. The total amylolytic activity in fries of roach, blue bream and perch correlates to fish type of feeding.

Regulation of the Fish Alimentary Behavior: Role of Humoral Component

Based on our own personal experimental data and literature data, role of some metabolites and hormones in regulation of the fish alimentary behavior is considered. The main statements of the synthetic theory of regulation of the alimentary behavior are presented.