Prespawning Period Research Articles

Polysubstrate monooxygenase activity and sex hormones in pre- and postspawning rainbow trout ( Salmo gairdneri)

The hepatic microsomal cytochrome P-450 content and polysubstrate monooxygenase (PSMO) activities as well as plasma levels of sex hormones in gonadally mature rainbow trout ( Salmo gairdneri) were studied. The plasma level of testosterone in prespawning female fish exceeded that of male fish. In both sexes, the testosterone level was at its highest in March and decreased considerably before the spawning time. The 17 β-estradiol content in female fish showed similar changes. The hepatic cytochrome P-450 content was at its lowest in prespawning fish in March, and significantly lower in females than in males. The sex difference in the cytochrome P-450 content disappeared after spawning. The absorption maximum of the reduced cytochrome-CO-complex varied from 449–450 nm without any correlation to the sex of the fish or the cytochrome P-450 content. In PSMO activities (benzo[ a]pyrene, 7-ethoxycoumarin, aminopyrine and ethylmorphine as substrates), a significant sex difference could be observed during the prespawning period. In all cases the activity was lower in females than in males. The 7-ethoxy-resorufin deethylase activity did not, however, show any sex difference. Benzo[ a]pyrene hydroxylase and 7-ethoxyresorufin deethylase activities in both sexes increased gradually during the pre- and postspawning times, being at their highest level in June. However, aminopyrine demethylase activity increased considerably during the prespawning period, and then decreased during and after spawning. The results indicate that changes in monooxygenase activities are dependent on the substrate used and the state of spawning, refering to the presence of multiple forms of cytochrome P-450 in the rainbow trout liver. Prior to spawning the rainbow trout is probably most sensitive to direct acting chemicals and most resistant to activation requiring compounds due to the much lowered levels of cytochrome P-450 and several monooxygenase activities.

Changes in serum concentrations of steroid hormones, thyroxine, and vitellogenin during spawning migration of the chum slamon, Oncorhynchus keta

Changes in serum concentrations of various steroid hormones (estradiol-17β, androgens, 17α,20β-dihydroxy-4-pregnen-3-one (17α,20β-diOHprog)), thyroxine and vitellogenin during the spawning migration (from the coastal sea to the spawning ground) of male and female chum salmon ( Oncorhynchus keta) were investigated. In females, estradiol-17β levels were high during the early phases of the migration (sea and prespawning period), but significantly decreased in fish at the time of the spawning period (oocyte maturation and ovulation). The changes in estradiol-17β levels coincided with those of serum vitellogenin levels. High levels of androgens were observed throughout the sampling period. Serum 17α,20β-diOHprog levels were extremely low during the early phases of spawning migration, but elevated dramatically in mature or ovulating females. In males, serum concentrations of androgens were high during the early phases of the migration, but sharply declined around the time of the spawning period (spermiation). Similar to females during final maturation, the serum levels of 17α,20β-diOHprog in males rapidly increased during spermiation, although the magnitude of the elevation in males was smaller than in females. Serum thyroxine levels were highest both in females and males collected in the coastal sea, and the levels decreased during the spawning migration. These findings are discussed in relation to anadromous migration and sexual maturation of chum salmon.

Dispersion of Rock Bass along the South Shore of Lake Ontario

Abstract From 1972 through 1981, 7,008 rock bass Ambloplites rupestris were tagged at sites along the southern shore of Lake Ontario; 854 tags (12.2%) were returned by anglers or recovered in the tagging program. Mean time and distance between tagging and recapture were 238 days and 15.5 km. Mean distance between release and recapture sites increased with time. One fish was taken 241 km from the release point. Rock bass tagged and recaptured in the prespawning period dispersed further than those tagged and recaptured after spawning. The predominantly eastward current along the southern shore of Lake Ontario had little overall effect on rock bass movements, but localized current patterns were reflected in dispersal. When dispersal from sites influenced by a thermal power-plant discharge was compared to that from control sites, slightly more rock bass stayed in warmer plume areas than in nonplume areas, although few remained long in any one location. As has been found with other animal species, dispersal of...

Seasonal changes in the epidermis of the winter flounder, Pseudopleuronectes americanus

Profound cyclical changes were observed in the epidermal thickness and in the concentrations of goblet cells and epidermal melanophores in an inshore population of winter flounder, Pseudopleuronectes americanus Walbaum. There is sexual dimorphism which is particularly prominent in the thickness of the epidermis during the pre-spawning period in the spring. At this time the male develops a significantly thicker lower epidermis. During and shortly after the spawning period (lower skin), or somewhat earlier (upper skin), there is a significant thinning of the epidermis in both sexes. Significant increases occur in goblet cell frequency, those of females being greater than males, during autumn and early winter and the April/May pre-spawning period. Goblet cell frequencies decrease in mid-winter (January–March) when general activity is low, and in the thin summer epidermis. These observations are compared with data from other teleosts and discussed in relation to hormones possibly affecting the epidermal structure of teleosts and in relation to known hormonal cycles in winter flounder.

Reproductive rhythm in tench, Tinca tinca (L.), in fluctuating temperatures

Experiments were conducted in heated and control ponds, aimed at determining variations in individual reproductive rhythms in tench, Tinca tinca (L). The number of spawnings of a population per season, varying from 3 to 9, showed a positive correlation with the sum of diurnal temperatures higher than 10°C, although the percentage of females participating in spawnings depended upon the pattern of temperature changes during this time. The variability of individual reproductive rhythms increased in seasons with greater temperature fluctuations. In consequence, the number of pausing females (not participating in spawnings) also increased, thereby lowering the increase of absolute fecundity resulting from the increased number of spawnings in higher temperatures. Similarly, duration of the prespawning period depended more upon the pattern of temperature changes at this time than upon temperature level.

Accumulation of mutagenic activity in bile fluid of river Rhine fish

Thyroid hormones (THs) are involved in regulation of many life history traits of fishes. Development, growth, reproduction and shaping the adult phenotypes were found to be regulated by THs. Regulatory evolution is one of the main factors driving morpho-ecological diversification and speciation. We tested a hypothesis whether closely related but ecologically diverged species may have a diverse level of THs. We compared seasonal levels of plasma concentrations of triiodothyronine (T3) in two cyprinid species, benthophagous bream Abramis brama and zooplanktivorous blue bream Ballerus ballerus. Significant differences in T3 concentrations were detected. B. ballerus had substantially reduced T3 levels as compared to most other species of fish. Two hypotheses explaining the thyroid divergence are discussed. Despite differences in absolute T3 concentrations, both species manifest similar seasonal cycling with increased plasma T3 levels in warmer seasons and decreased T3 in colder seasons. Several peaks of plasma T3 level were registered: at pre-spawning periods, at mid-summer and in the early autumn. The pre-spawning peak noted in cyprinids was a novel observation. Significant positive correlations were detected between water temperature and plasma T3 concentrations, as well as between the duration of daylight and T3 plasma concentrations in both species.

The Organization of the Pre-Spawning Behaviour in the Cichlid Fish Aequidens Portalegrensis (Hensel)

This study was aimed at obtaining insight into: a) how the communicative activities carried out by this substrate laying cichlid fish during the several days lasting pre-spawning period, function in facilitating pair formation, spawning and broodcare, and b) how the behavioural mechanism controlling the performance of these activities is structured. Both sexes use largely the same activities. The causational problems were primarily approached through statistical analysis of quantitative observations, regularly made on interacting males and females between their first confrontation and spawning. On the basis of the temporal association between the various activities, the latter could be classed into three groups, or clusters, which became successively dominant in the course of the pre-spawning period. On the ground of further observations, and on the results of experiments, a closer specification of the factors underlying these clusters was attempted. It was concluded that they are primarily due to internal factors or interactions between such factors, which can however be activated by specific external stimuli. The cluster appearing in the earliest phase of the encounter is simultaneously controlled by tendencies to attack and to escape; this behaviour subserves the defense of the territory. Absence of overt aggression in the response of the female appeases the agonistic behaviour of the male and causes the appearance of behaviour of the second cluster. In the control of this cluster a sexual system is involved beside the agonistic systems. Most of the activities of this cluster are instrumental in preparing a nest site; moreover their performance is likely to have a priming effect on the sexual factor. When this factor has become dominant over the agonistic ones, the fishes concentrate their behaviour on a hard substrate and the activities of the third cluster appear, culminating in oviposition and fertilizing.

Cholesterol esterification and lipids in blood plasma of the char ( Salmo alpinus L.) during sexual maturation

1. 1. The initial rate of cholesterol esterification and the concentration of triacylglycerols in plasma were generally lower in prespawning than in immature chars. No typical pattern of variation of plasma cholesterol could be observed. 2. 2. The observed variations in plasma cholesterol esterification and lipids may be caused by reduced feeding in the prespawning period. 3. 3. The initial rate of cholesterol esterification in plasma was positively correlated with the concentrations of triacylglycerols and unesterified cholesterol in plasma, respectively.

Responses of two different types of pituitary gonadotrophs of the loach, Misgurnus anguillicaudatus, to gonadectomy and to exogenous sex steroids

In the proximal pars distalis of the pituitary gland of the loach, Misgurnus anguillicaudatus, two basophilic cell types with different localities, staining properties, and cytological characteristics are discernible other than thyrotrophs and somatotrophs. Ultrastructural changes of these two types of basophils, termed the globular and the vesicular cells according to their ultrastructural features, were examined in loaches of both sexes which had been subjected to bilateral gonadectomy and to treatment with sex hormones during the late prespawning period. Complete gonadectomy stimulated the globular cells to show dilation of the rough endoplasmic reticulum and a decrease in the amount of cytoplasmic granules. The changes were less intense in males than in females 60 days after gonadectomy. The vesicular cells did not show evident alterations following ovariectomy in females but did respond to castration in males with an enlargement of the cytoplasmic vesicles characteristic of the cell type. After six injections of estradiol (50 μg/fish) to females during a month, the globular cells became atrophic with accumulation of cytoplasmic granules, while the vesicular cells exhibited rather slight changes of their activity including an activation of the Golgi apparatus. Similar administrations of testosterone (100 μ/fish) to males elicited regressive changes of both the globular and the vesicular cells, and shrinkage to a lamellar form of cytoplasmic vesicles in the latter cells is particularly notable. The results were discussed in terms of the possible existence of two distinct types of pituitary gonadotrophs in the loach, each of which may play a role at different stages of the sexual cycle of the fish of each sex.

Annual variations of some carbohydrate and lipid parameters in the fish Spicara chryselis during captivity

Abstract o 1. The yearly variations of blood glucose and ketone bodies, free fatty acids (FFA) in plasma, and liver glycogen concentration have been analyzed in Spicara chryselis C.V.(F. Centracantidae) during captivity. 2. The physical conditions and changes (salinity, water temperature and light) in the aquarium were, for all practical purposes, equal to those of the open sea, due to the use of an open-circuit aquarium. 3. The spawning period in May represented the pivot point in the metabolic changes, and in autumn, storage of fats and carbohydrates was evident. 4. The blood glucose increased during the prespawning period (March–April), in July, and in the autumn. 5. The glycogen content was low during spawning, and increased sharply during the storage period. 6. The FFA increased during the prespawning period, and also in the fattening period, November. 7. The ketone bodies presented a peak during summer that could be related to greater activity of the fish.

Effects of melatonin and prolactin treatment on the hypophysial-ovarian system in the catfish, Heteropneustes fossilis (Bloch)

The effects of daily administration of melatonin or ovine prolactin for 20 days were evaluated with respect to the response of the hypophysial-ovarian system in the catfish. Heteropneustes fossilis, during the prespawning and spawning periods. In the prespawning period, daily treatment with melatonin (20 or 100 μg/fish) or prolactin (100 or 250 μg/fish) significantly inhibited vitellogenesis and induced follicular atresia in the ovary, whereas at the level of the pituitary, only the higher dose of melatonin (100 μg/fish) brought about a significant reduction in the number of gonadotrophs. In the spawning period, melatonin (20 or 100 μg/fish) and prolactin (100 or 250 μg/fish) treatment induced significant ovarian regression, and the higher doses of melatonin (100 μg/fish) and prolactin (250 μg/fish) alone significantly reduced the number of pituitary gonadotrophs. Cessation of treatment with melatonin or prolactin resulted in restoration of activity in the pituitary and ovaries. Evidence is presented to show that the inhibition exerted by melatonin or prolactin is tentative and that this inhibitory influence is abolished following withdrawal of treatment.

Photoperiod and Temperature Control in the Regulation of Reproduction in the Female Catfish Heteropneustes fossilis

The annual reproductive cycle of the catfish Heteropneustes fossilis is divided into the preparatory period (February–April), prespawning period (May–June), spawning period (July–August), and postspawning period (September–January). Ovarian recrudescence, which normally occurs during the prespawning period, can be advanced by photothermal manipulations. During the postspawning and preparatory periods, the tempo of ovarian recrudescence is much faster at 30 C than at other temperatures (ambient, 25 or 34 C) regardless of photoperiod (14L + 10D, 12L + 12D, or 9L + 15D).Warm temperature (30 C) postpones the postspawning ovarian regression only up to the first week of October regardless of photoperiod. The ovarian cycle is regulated by a circannual rhythm which can be activated 5 mo earlier, but its activity cannot be prolonged beyond October by photoperiodic and temperature manipulations.Interruption of the night of a short day (6L + 18D) treatment by 1 h of light between 0000 and 0100 induces ovarian recrudescence that is significantly greater than that obtained in the control group exposed to 7L + 17D. Scanning of the major part of the dark period (1800–0500) to determine the duration of the photo-inducible phase shows that it lies between 0000 and 0500 with peaks from 0000 to 0100 and from 0400 to 0500. Even 1 h of light in a regimen of 1L + 23D presented between 1900 and 0500 produces significant ovarian recrudescence with peaks between 2200 and 0100. These results clearly demonstrate the possible involvement of a circadian mechanism for photoperiod measurement in the catfish.Precociously gravid catfish obtained as early as April by photothermal treatment have been induced to spawn in the laboratory by administration of ovine luteinizing hormone (LH). Ripe eggs after fertilization hatched into seemingly normal fry. Further, the spent fish when subjected to the same photothermal treatment developed a fresh crop of yolky eggs within 1 mo; such gravid females have been again induced to spawn with LH. This process has been repeated so that the same set of fish have been spawned 4 times between April and July of the same year. Thus, it is possible to get catfish fry not only early but also 2.6 times more than that usually available from each female during the spawning season. The aquacultural potentialities of this laboratory discovery are discussed.

Maintenance of spermatogenesis and seminal vesicles in the hypophysectomized catfish, Heteropneustes fossilis (Bloch): effects of ovine and salmon gonadotropin, and testosterone.

The effects of 20-day treatment with ovine luteinizing (LH) and follicle-stimulating hormone (FSH), partially purified salmon gonadotropin (SG-G100), and testosterone were investigated by evaluating the maintenance of spermatogenesis in the testes and secretory activity in the seminal vesicles of the catfish, Heteropneustes fossilis, after hypophysectomy during the prespawning period. Low doses of LH (0.1 or 1 μg per fish) neither maintained spermatogenesis in the testes nor secretory activity in the seminal vesicles, whereas a higher dose of LH (10 μg per fish) maintained spermatogenesis qualitatively, and sustained the seminal vesicles in a moderately secretory state. One microgram of SG-G100 per fish partially maintained spermatogenesis but the seminal vesicles showed poor maintenance. Ten micrograms of SG-G100 per fish not only sustained spermatogenesis qualitatively and quantitatively, but also induced spermiation; the seminal vesicles, though enlarged, contained little secretion, indicating possible reduction through spermiation. FSH did not maintain spermatogenesis in the testes or secretory activity in the seminal vesicles. Testosterone (10, 100, or 500 μg per fish) had a dose-dependent maintenance response in the testes and seminal vesicles; with 500 μg of testosterone the maintenance of testes and seminal vesicles was similar to that in initial intact controls, with no indication of spermiation.

Some effects of external factors upon the reproductive behavior of the grass frog Rana t. temporaria L. (Ranidae, Anura).

The reproductive period of Rana temporaria can be subdivided into a prespawning period and a spawning period. During the prespawning period only a few Rana temporaria, most of them males, are active in the spawning biotope. There is no calling activity, and deposition of spawn rarely occurs. The time of onset of the prespawning period is variable. In this period the frogs are highly responsive to a drop in the temperature of air and water, burying themselves in the bottom or leaving the spawning waters.By contrast, many animals participate in the spawning period. Migration to the spawning ground takes place chiefly at night. The frogs engage in mating activity immediately upon arrival, and both males and females depart as soon as they have spawned, migrating away in directions corresponding to those of the immigration. During the spawning period there is no demonstrable response of the grass frogs to weather conditions. Rana temporaria begins its spawning period at the so-called "set time" only in meteorologically normal years. When meteorological conditions are unusual, the spawning period can begin as much as 10 days earlier or later.Possible external timing signals for the onset of migration include temperature in combination with day length, and a drop in atmospheric pressure accompanied by rainfall.

Response of the pituitary of the catfish, Heteropneustes fossilis (Bloch), to bilateral ovariectomy.

Hypophyseal response to bilateral ovariectomy was studied in the catfish, Heteropneustes fossilis, during the prespawning (May) and the spawning (July) periods. During the prespawning period, a significant increase in the number of granulated PAS-positive basophils in the proximal pars distalis of the castrates was recorded on day 45 post-ovariectomy; thereafter a gradual degranulation of basophils was observed. However, in the spawning period a dramatic increase in the number of granulated basophils of the castrates was seen on day 8 post-ovariectomy and the number decreased thereafter. This differential response of the hypophysis to ovariectomy is discussed.

Seasonal changes in the hypothalamo‐hypophyseal‐ovarian system in the catfish, Heteropneustes fossilis (Bloch)*

The annual reproductive cycle of the catfish, H. fossilis (Bloch) is divided into the preparatory period (February‐April), the prespawning period (May‐June), the spawning period (July‐August) and the postspawning period (September‐January). During the early postspawning period (September‐November), the hypothalamo‐hypophyseal‐ovarian system shows a gradual regression. In January, the hypothalamic nuclei, the pars magnocellularis (PMC), the pars parvocellularis (PPC) of the nucleus preopticus (NPO), and the nucleus lateralis tuberis (NLT) show renewed activity, as shown by a significant increase in their nuclear diameters and an accumulation of neurosecretory material (NSM) in their cell bodies. The hypophysis and the ovary remain quiescent. During the preparatory period, all the hypothalamic neurons studied indicate decreased activity but simultaneously show an accumulation of NSM in their cell bodies. The number of granulated basophils in the proximal pars distalis (PPD) of the hypophysis remains low but ovarian weights increase, presumably due to the multiplication of oogonia. In the prespawning period, there is a marked accumulation of NSM in the cell bodies of the hypothalamic neurons and at the same time the number of granulated basophils in the PPD of the hypophysis dramatically increases with concomitant increase in vitellogenic activity in the ovary. During the spawning period, the hypothalamic neurons continue to store NSM in their cell bodies and simultaneously there is a tremendous increase in the number of granulated basophils in the PPD of the hypophysis and the ovary has a large proportion of yolky primary oocytes. Spawning is associated with a significant degranulation of the granulated basophils in the PPD of the hypophysis. The significance of the results is discussed in relation to the environmental and hormonal regulation of seasonal ovarian activity.

Biological Changes in Coastal Capelin from the Over-Wintering to the Spawning Condition

Regular research vessel surveys in Trinity Bay, Nfld., during 1967–68 indicated that significant biological changes occurred in coastal capelin from the over-wintering to the spawning period. During their over-wintering period in February–March mature capelin had a high fat content, a low feeding intensity, a low nematode incidence, and were heavy at length. The gonads were in a resting stage, secondary sexual characteristics were absent, and the sexes were integrated. During the prespawning period in April–May the feeding intensity increased and the gonads and secondary sexual characteristics began to develop, whereas the fat content declined. At this time the schools were segregated by sex. By the start of the spawning season in mid-June the capelin had ceased feeding, the fat content was low, and the weight at any particular length was less than that during the over-wintering period. The incidence of nematodes was high and the sexes were readily distinguished by the conspicuous secondary sexual characteristics. These changes are discussed in relation to the seasonal distribution pattern of coastal capelin in Trinity Bay and the feasibility of a commercial fishery.

Effects of blinding and/or total darkness on ovarian recrudescence or regression during the appropriate periods of the reproductive cycle of the catfish,Heteropneustes fossilis(Bloch)∗∗

Abstract Three experiments were performed wherein intact and blind catfish were subjected to various photoperiodic regimes during the preparatory, the prespawning and the spawning period to ascertain the role of eyes in the perception of photoperiodic stimulus. In the first experiment, conducted during the prespawning period, intact and blind catfish were subjected to laboratory photoperiod (12 hr/day) or total darkness. The results indicate that ovarian recrudescence occurs in spite of the absence of eyes and light. But the tempo of ovarian recrudescence is slower in the blind animals than in the sighted animals. The results of second experiment where intact and blind catfish were subjected to total darkness for 163 days during the preparatory period show that ovarian recrudescence takes place in all the groups regardless of the presence or absence of eyes and/or of light. The magnitude of ovarian enlargement was greater in the intact control and intact catfish exposed to total darkness than in the corresponding blind groups. In the third experiment conducted during the spawning period, decreasing photoperiod induced a more precipitous ovarian regression in the presence than in the absence of eyes. Eyes, though important receptors for photoperiodic perception, are not indispensable. The presence of a self‐operating internal mechanism regulating reproduction in the catfish is envisaged. The significance of these findings is discussed.

Seasonal reproductive activity in the testes and seminal vesicles of the catfish, Heteropneustes fossilis (Bloch)

AbstractA seasonal study of the seminal vesicles in relation to that of the testes had been conducted in the catfish, H. fossilis. The annual reproductive cycle of the catfish has been divided into (i) Preparatory period (February–April), (ii) Prespawning period (May–June), (iii) Spawning period (July–August) and (iv) Postspawning period (September–January). Testes exhibit initiation of spermatogenesis in the mid‐preparatory period, but significant increase in weight of the testes accompanied by active spermatogenesis occurs during the prespawning period. In the spawning period, the testes are maximally enlarged and their seminiferous tubules are packed with spermatozoa. Following spawning, the testes gradually regress in the postspawning period. The seminal vesicles show initiation of secretory activity during the preparatory period but their recrudescence lags behind that of the testes by about a month. The seminal vesicles attain maximum weight and secretory activity during the spawning period. Thereafter, the seminal vesicles regress precipitously and sooner than the testes.The histochemical and biochemical studies on the seminal vesicles indicate that the secretion contains mucoproteins, acid mucopolysaccharides, primary proteoses, besides traces of phospholipids and native proteins.

PERMEABILITY OF CELLS AND ITS IMPORTANCE IN ASSESSMENT OF FISHES AGE

The article presents analysis of material and results of their own studies on changes in the permeability of cellular structures, organs and tissues in carp, which is of great importance in determining age-related indicators. The cells permeability in liver and gonads estimation was carried out under the experimental base of VNIIR on two carp genotypes during the pre-spawning period. The carp groups taken for analysis differed significantly in their genotypes. In females of the Khrapunov group the fecundity was 2023.0 thousand units, while the number of oocytes filled with yolk was only 0.7%, in the Ostashevsky ones - 1370.0 thousand units and 8.6%, respectively. During estimation the chemical composition of the generative tissue in females and males it was established that the cholesterol and lecithin content in males is higher than that of females, while feeding dependence is observed, especially on the amount of protein in the diet. For example, in females on protein diet contained less glycogen in gonads than on females on carbohydrate diet. Lecithin and cholesterol are higher in males than in females, which corresponds to increasing the Gyurdy Ratio (estimation of cell membrane strength). In spermatogenesis the content of phospholipids and cholesterol in the liver was decreased less than during ovogenesis. This indicates a lower level of synthetic processes in the milts compared with the ovaries. The cholesterol content in sperm is higher than in caviar in 19.6 times, and phospholipids almost doubled. With increasing age, the Gyordy Ratio for caviar decreases, for sperm it increases, the percentage of caviar fertilization increases. As the body age metabolism deteriorates, cellular permeability decreases (the ratio of lecithin and cholesterol changes significantly). At the same time, the permeability of cells in different organs and tissues varies and depends on living conditions, especially feeding and to some extent on the origin. In fish the gross productivity decreases as growth slows down and more energy is spent on adaptation to environmental conditions.