E. D. Pavlov

Cytological status of the gonads and the level of thyroid and sex hormones in juvenile Black Sea trout, Salmo trutta labrax , of two phenotypic forms

Cytological state of gonads and hormonal status was studied in juvenile (15-month-old) Black Sea trout Salmo trutta labrax of the two phenotypic forms (resident and migratory). The differences in the rates of hametogenesis in the compared forms were revealed. It is shown that the spermatogenesis in the resident form is more intensive; on the other hand, the ovogenesis is slower. The levels of thyroxin and testosterone in blood are significantly higher in the groups of fish with intensively running gametogenesis. It is found that the concentration of triiodothyronine is slightly slower in the resident form than in the migratory. The correlation between levels of thyroid and sex steroid hormones is revealed.

The state of gonads of resident sockeye salmon Oncorhynchus nerka from the Tolmachev Reservoir

Morphology of gonads and structure of sex cells in females and males of the resident sockeye salmon Oncorhynchus nerka—kokanee—from Tolmachevskoe Reservoir are investigated. Anomalies in structure of sex cells and structure of oocytes are found. Partial or mass resorpbion of cells in the ovaries of males and testes of males is found, leading to sterility of gonads. The relationship between anomalies found in structure of the sex system of kokanee, changes in biological parameters of fish and the increase of the population abundance is discussed.

State of gonads in juvenile triploid trout Oncorhynchus mykiss under conditions of South Vietnam after artificial sex inversion

Gonad morphology and structure of sex cells in juvenile triploid trout Oncorhynchus mykiss of the Donaldson breed incubated and reared at a trout plant under climatic conditions of South Vietnam have been studied. Anomalies in the structure of sex gonads and oocyte structure were found, and partial resorption of sex cells was detected. It was shown that sex inversion in triploid (unisexual) fingerlings of rainbow trout passed successfully on the whole since many sex gonads of these fish simultaneously had both female and male sex cells and sometimes were sterile. The connection of anomalies found in the structure of sex system of trout with species rearing under unusual for it climatic conditions and artificial sex inversion is discussed.

Anomalies in ovarian condition of manybar goatfish Parupeneus multifasciatus (Mullidae) from the coastal zone of south Central Vietnam

We describe anomalies in oocyte structure of manybar goatfish Parupeneus multifasciatus from the coastal zone of southern Central Vietnam. The anomalies are registered in the majority of cells (>80%) from ovarian fragments of several individuals. The abnormal cells are at the periods of maturation, vitellogenesis, and, sometimes, previtellogenesis. Possible effect of pollutants on oocyte morphology is discussed.

State of gonads of yearlings of triploid rainbow trout Oncorhynchus mykiss exposed to androgenic hormone under high-mountain conditions of South Vietnam

Changes in the morphology of gonads under the effect of methyltestosterone in juveniles of triploid rainbow trout Oncorhynchus mykiss incubated and cultivated in a trout farm under climatic conditions of South Vietnam have been studied. It was shown that the effect of the androgenic hormone intensifies the formation and development of testes in triploid rainbow trout at an age of 1+, decreasing the proportion of sterile individuals and the proportion of fish with anatomical and cytological anomalies in the structure of gonads. The relationship between the found anomalies in the structure of the genital system of trout and its triploidization, hormonal effect, and abiotic environmental conditions is discussed.

Influence of surfagon on rheoreaction of juvenile rainbow trout

The rheoreaction of juvenile rainbow trout (aged 2 months) was studied 30–40 days after a single injection of surfagon (synthetic analogue of gonadotropin-releasing hormone). Individuals subjected to surfagon preferred to move against the water current both in normal and migratory state, while control (not injected) individuals preferred to move downstream. Surfagon strongly modified the rheoreaction of individuals in normal and migratory state.

Effect of methyltestosterone on physiological state and rheoreaction of rainbow trout Parasalmo mykiss (=Oncorhynchus mykiss) under unfavorable keeping conditions

The effect of methyltestosterone given with feed during one and two months on the state of gonads, the level of thyroid, and sex steroid hormones in blood and on rheoreaction is studied in juvenile rainbow trout Parasalmo mykiss (=Oncorhynchus mykiss) raised under unfavorable conditions (tropics, Vietnam). In comparison with the control, in the experimental group, the part of sterile specimens was higher (83 vs. 35%), the part of males was lower (17 vs. 40%), while females and hermaphrodites were absent. At prolonged starvation (12 days), the experimental specimens demonstrated lower increase of the level of thyroid and sex steroid hormones in blood than that in the control specimens. Methyltestosterone modified the behavior of rainbow trout in water flow: delivery of the hormone in food during 1 month increased the part of fish moving against the flow and suppressed movement both upstream and downstream during 2 months. Thus, methyltestosterone negatively influences the physiological condition and adaptation capacity of rainbow trout.

Cytological state of gonads and level of thyroid and sex steroid hormones in black sea trout Salmo trutta labrax Pall.

Cytological state of the gonads and hormonal state of hatchery Black Sea trout before differentiation into resident and anadromous forms (parr) at an age of 15 months have been examined. It has been shown that the hormonal changes associated with the choice of life strategy in the Black Sea trout females and males are pronounced to different degrees. As compared with the resident and anadromous individuals, the female parr display a low rate of oogenesis and similar hormonal status, while characteristic of the male parr are an intermediate rate of spermatogenesis, a low level of thyroid hormones and estradiol, and a medium testosterone level. As has been found, the undifferentiated Black Sea trout individuals predominantly develop into the resident form.

Diurnal dynamics of thyroid and sex steroid hormones in the blood of yearlings of the resident form of Black Sea trout Salmo trutta labrax

The diurnal dynamics of the content of thyroid and sex steroid hormones is investigated in the blood of the resident form of Black Sea trout in summer. The maximums and minimums of concentration of the investigated hormones do not coincide over 24 h, except for the decrease in the level of T3 and testosterone before dawn. The dynamics of the investigated hormones is controlled to a high extent by the sex of fish in the morning and in the daytime.

Content of thyroid and sex steroid hormones in young-of-the-year of Black Sea trout Salmo trutta labrax from two spatial groups for different duration of starvation

The content of thyroid and sex steroid hormones is determined in fish-farm juveniles of Black Sea trout, 5.5 months old, from the bottom and pelagic spatial groups differing in the probability of future selection of the resident or anadromous life strategies, respectively. Differences in the concentration of the aforementioned hormones are found in young-of-the-year corresponding to those in the migratory and resident forms of yearlings of trout. In the juveniles from the pelagic group at the age 0+, the level of triiodothyronine, thyroxine, and testosterone is higher than in specimens from the bottom group. Prolonged starvation results in a higher content of triiodthyronine, thyroxine, and testosterone in the blood of juveniles from both spatial groups. The concentration of estradiol-17β increases in pelagic specimens and decreases in bottom specimens.