Rate Of Gonadal Development Research Articles

Heritability estimates for gonadal development traits and their genetic correlations with growth and heat tolerance traits in the Fujian Oyster Crassostrea angulata

Improving the progress of breeding is the main purpose of breeders, and shorting the reproductive cycle is one of the ways to improve the breeding progress. Although the reproductive cycle of Crassostrea angulata can be shortened from one year to half a year by selecting precocious individuals, little is known about whether this selection will accelerate their gonadal development or disturb their selection for productive traits. Here, the heritability of gonadal development traits (gametogenic stage and egg diameter) and their genetic correlations with both growth traits (shell height at 4 and 12 months and total body weight at 12 months) and heat tolerance trait were estimated. The heritability for gametogenic stage was low (0.18 ± 0.09), while the egg diameter showed a high heritability (0.78 ± 0.30). These results suggest that selection for precocious individuals has little effect on the rate of gonadal development in the C. angulata, despite the effect may be greater in females than in males. The genetic correlations between gonadal development traits and both growth (-0.02–0.30) and heat tolerance traits (-0.08–0.34) were low and non-significant. These results suggest that selection for precocious individuals has negligible effects on their productive traits. Therefore, it is feasible to double the breeding efficiency of C. angulata by halving their reproductive cycle.

Temporal phase relation of circadian neural oscillations as the basis of testicular maturation in mice: A test of a coincidence model

To study the underlying mechanism of gonadal growth during the attainment of puberty and to test a coincidence model, 7 experimental groups of 2-week-old male mice, Mus musculus, were administered the serotonin precursor, 5-hydroxytryptophan, followed by the dopamine precursor, L-dihydroxyphenylalanine at hourly intervals of 6, 7, 8, 9, 10, 11 and 12 h (5 mg/100 g body weight per day for 13 days). At 11 days post-treatment, a suppression of gonadal activity was seen in the 7-h mice and a maximum suppression in the 8-h mice, along with a significantly increased degree of gonadal development in the 12-h mice, as compared with the controls. In addition to its known regulation of seasonal gonadal cycles, the relative position of two circadian neural oscillations may also affect the rate of gonadal development during the attainment of puberty in mice. Moreover, the present study provides an experimental paradigm to test the coincidence model of circadian oscillations.

Gamete viability as an indicator of reproductive endocrine disruption in fish

Xenobiotic pollutants may disrupt reproductive endocrine function by acting at the hypothalamus, pituitary, gonad or liver. Disruption at any of these sites may result in either changes in the rate of gonadal development or in the viability of the gametes. Production of high quality gametes is dependent upon the correct hormonal milieu throughout their development, and any disruption of hormonal balance may result in abnormal sperm or eggs. Such effects may be apparent at levels of pollutant lower than that which causes arrest of gametogenesis or decreased gonadosomatic index. In this paper the use of sperm motility, morphology and fertilising ability in males, and egg numbers, size and hatching success in females as monitors of endocrine disruption will be discussed. Data are presented to show that exposure of adult zebra danios ( Danio rerio) to 5 ng l −1 ethynylestradiol leads to arrest in development of the eggs produced at the early blastula stage and induces vitellogenesis in exposed males.

Social stimulation and regulation of body mass in female starlings

The influence of consexual social stimulation on the regulation of body mass in female European starlings,Sturnus vulgarisduring reproductive development was examined. Twenty-four pairs of birds were housed in three social stimulation treatments: (1) control, where birds were housed in visual isolation from their partner; (2) visual contact, pairs of birds were separated by a clear Perspex screen, preventing direct physical contact, but allowing birds to view each other; (3) complete contact, pairs of birds were housed with no intervening divider, allowing full interactions between birds. The influence of these treatments on gonadal development, body mass and energetic reserves was examined. The manipulation did not significantly influence degree or rate of gonadal development, but did influence total body mass; birds from the complete contact group increased body mass to a greater extent than the other groups. This between-group difference was attributable to changes in lean mass, rather than energetic reserves. However, within the complete contact group, subdominants increased their energetic reserves more than dominants. These results are, in part, consistent with differences in competition for food between the treatment groups influencing mass regulation, although changes in activity levels may also be important. Unlike previous studies, these results suggest that the social environment may influence the regulation of lean mass in addition to energetic reserves.

Broodstock management of Crassostrea gigas: Environmental influences on broodstock conditioning

Maximum larval survival is realized when broodstock are in an optimum stage of gonadal development and the efficiency of larval culture may be substantially improved by using only optimally conditioned broodstock. The conditioning requirement to bring broodstock into this optimum stage is dependent upon the stage of gonadal development at the commencement of conditioning and upon the rate of conditioning. The stage of gonadal development at the commencement of conditioning may be determined directly or inferred by understanding the annual cycle of gonadal development occurring in the broodstock. The rate of conditioning, on the other hand, is regulated by the conditioning environment. In the present study, we have observed the influence of three components of the conditioning environment: temperature, salinity, and supplemental feeding on the rate of gonadal development during hatchery conditioning of broodstock. The rate of gonadal development is a function of temperature intensity and time rather than accumulated thermal exposure. Salinity exerted a negative influence on the rate of development in oysters conditioned at salinity levels below 30 parts per thousand (ppt). Furthermore, when oysters conditioned at 20 ppt relative to 30 ppt were spawned and the larvae were reared under standardized hatchery conditions, larval survival was markedly reduced in the former. Fecundity of broodstock was 60% greater when fed an algal food supplement of the diatom Thalassiosira pseudonana relative to starved controls, although the rate of gonadal development and gamete viability was not significantly different. Using these empirically determined functions, a simplistic quatitative model may be employed to predict broodstock conditioning requirements in order to increase the proportion of optimally conditioned brood oysters.

Simulation of Temperature and Upwelling Effects on the English Sole (Parophrys vetulus) Spawning Season

Spawning times for English sole (Parophrys vetulus) in Oregon waters were estimated for 13 yr using data on adult female gonadal condition, and surveys of pelagic larvae and benthic juveniles of known ages. The spawning season for this species is extremely protracted and variable. Some spawning may occur in all months, but most occurs between September and April, with a peak lasting 1–3 mo within this period. Variations in the English sole spawning season appear to be largely accountable by variations in a continental shelf temperature index (developed from a relationship with Neah Bay sea level). The following three hypotheses about temperature control of spawning were described by mathematical relationships which were incorporated into a simulation model that was driven by the time series of the bottom temperature index: (1) the rate of gonadal development is inversely related to summer bottom temperatures; (2) spawning is inhibited by temperatures below about 7.8 °C; and (3) spawning is delayed by rapid increases in bottom temperature. The model in its present form can be used to simulate spawning activity for years void of empirical spawning records and to design laboratory experiments capable of validating cause-and-effect relationships.Key words: Oregon, English sole, spawning time, upwelling, shelf temperature, hypotheses, simulation model

The effects of the daily photoperiod on gonadal growth, neurohypophysial hormone content, and neurosecretion in the hypothalamo-hypophysial system of the Japanese quail ( Coturnix coturnix japonica)

The photoperiodic control of gonadal development was examined in the Japanese quail ( Coturnix coturnix japonica). Long (20 hours) daily photoperiods caused a quantitatively uniform growth of testes and ovaries to full reproductive condition, whereas no development occurred in birds held on 6-hour daily photoperiods. Arginine vasotocin and oxytocin were identified by pharmacological and chromatographic methods in both the pars nervosa and the median eminence. The concentrations of these peptides showed no significant correlations with the rate of gonadal development. Similarly, no significant changes were detected in the hypothalamic neurosecretory system under different photoperiodic regimes, although there appeared to be a trent towards a greater accumulation of stainable material in the reticular layer of the median eminence of birds held on short daily photoperiods. Dehydration resulted in a correlated depletion of neurosecretory material and neurohypophysial hormones from the median eminence and pars nervosa with a greater loss of arginine vasotocin than oxytocin from the pars nervosa.

Influence of Light and Temperature on the Reproductive Cycle of the Eastern Brook Trout, Salvelinus fontinalis (Mitchill)

Brook trout were exposed to photoperiods ranging from 4 to 20 hours per day and were held either at 8.5 °C or at 16°. The average diameter of the ova was used as an index of ovarian development while testicular maturation was determined from histological preparations.The gonadal cycles of both male and female trout were markedly affected by different photoperiodic regimes. The influence of long or short photoperiods depends upon the phase of gametogenesis in progress at the time and on the photoperiod in effect during earlier stages of the gonadal cycle. Evidence is presented which suggests that the maturation cycle of the gonads may be regulated by the normal seasonal changes of day length.An accelerated light regime can hasten the time of functional maturity in adult trout, but is without effect when applied to maturing fish in which gametogenesis is taking place for the first time. It is suggested that a stimulative effect of environmental factors is dependent upon maturation of the hypothalamic-hypophyseal mechanism.The rate of gonadal development is the same at 16° as it is at 8.5° provided the fish are exposed to natural day lengths. If fish are subjected to long or to short photoperiods, the gonadal response at 16° is quite different from that at 8.5°.