Plasma Sex Steroid Levels Research Articles

Disruption of gonadal maturation in cultured Senegalese sole Solea senegalensis Kaup by continuous light and/or constant temperature regimes

A major problem in the development of Senegalese sole Solea senegalensis intensive culture is the poor control on reproduction, in part due to the lack of knowledge on the precise role of photoperiod and temperature. Thus, gonadal maturation was evaluated by assessing the sequential changes in plasma levels of 17β-estradiol (E 2), 11-ketotestosterone (11-KT), and testosterone (T) in both female and male cultured Senegalese sole (F1 generation) exposed to various combinations of constant or naturally-fluctuating daylength and water temperature. Under natural photoperiod (NP; 36° N), exposure to constant temperature (t0; 18–20 °C) disrupted gonadal development, as indicated by a lower incidence (in comparison with naturally-fluctuating water temperature; 14–24 °C) of females at advanced maturation (from February to April: 12 vs. 33%) and running males (from February to May: 46% vs. 57%), and the reduced mean (± S.E.M.) sex steroid plasma levels (female peak E 2 levels: 2.9 ± 0.28 vs. 1.8 ± 0.3 ng ml − 1 ; male peak T levels: 1.5 ± 0.14 vs. 0.9 ± 0.06 ng ml − 1 ). Therefore, the onset and progression of gonadal development in this species seem to be strongly (“proximally”) influenced by fluctuating water temperature. When compared to NP and t0, exposure to continuous light (LL) under t0 significantly reduced steroid production (female peak E 2 levels: 1.8 ± 0.28 vs. 0.5 ± 0.05 ng ml − 1 ; male peak 11-KT levels: 9.4 ± 1.06 vs. 5.4 ± 1.33 ng ml − 1 ) and subsequently gonadal development (lower proportions of females at intermediate [46 vs. 6%] and advanced maturation [12 vs. 0%] from February to April and of RM [46 vs. 33%] from February to May). Thus, the seasonal changes of daylength would be crucial for normal gonadal development, being its cueing effects of higher magnitude than those of water temperature. The present report constitutes the first systematic study focused on the environmental control of reproductive events in Senegalese sole.

Winter profile of plasma sex steroid levels in free-living male western diamond-backed rattlesnakes, Crotalus atrox (Serpentes: Viperidae)

Recent field studies on the reproductive ecology of western diamond-backed rattlesnakes ( Crotalus atrox) from populations in southern Arizona showed significant differences in the concentration of plasma sex steroids (testosterone, T; 5α-dihydrotestosterone, DHT; and 17β-estradiol, E2) throughout the active season (March–October), and peak levels were coincident with the two mating periods (late summer and early spring). There is, however, no information on levels of sex steroids during winter. Similar to most snakes, hibernating individuals of C. atrox are typically inaccessible, but in southern Arizona, where environmental conditions are typically mild during winter, adult males frequently bask at or near the entrances of communal dens. Basking activity, therefore, offers a unique logistical opportunity to assess the complete annual profile of plasma sex steroid levels in males of a temperate reptile in nature. From November to February, we measured levels of plasma T, DHT, and E2 in adult male C. atrox that were located basking at communal dens. Additionally, cloacal, core body, and ambient air temperatures were obtained to investigate potential relationships between body temperatures and levels of sex steroids. Mean levels of T, DHT, and E2 were relatively high, and the concentration hierarchy was T > DHT > E2. Mean levels of T, DHT, and E2 showed no significant variation across the four months of sampling; however, E2 levels decreased progressively. In the annul cycle, sex steroid levels during winter were not basal when compared to values obtained during the active season. Mean cloacal temperatures of basking males were significantly higher than core body temperatures of non-basking males (inside dens) from November–December, and in February, which suggests that one function of winter basking is to elevate body temperatures. Steroid levels, nonetheless, were not significantly correlated with cloacal temperatures. We suggest that future field studies of male C. atrox should: (a) investigate sex steroid levels in non-basking individuals and (b) test whether elevated levels of sex steroids during winter facilitate the large increases that occur in early spring, which are coincident with the second mating season. Our findings on the reproductive biology of C. atrox and other viperids are discussed in the context of the associated–dissociated model of reproduction.

Testicular development and plasma sex steroid levels in cultured male Senegalese sole Solea senegalensis Kaup

Testicular development and plasma levels of sex steroids (11-ketotestosterone (11-KT), testosterone (T) and 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P)) were investigated for the first time in cultured male Senegalese sole Solea senegalensis. The germ cell dynamics and gonadosomatic index ( I G) were monitored. Based on the relative abundance of the different types of germ cells present, the spermatogenetic cycle was divided into five stages: early (I; spermatogonia (SPG)), mid (II; SPG, spermatocytes (SPC) and spermatids (SPD)), and late spermatogenesis (III; SPC, SPD, and spermatozoa (SPZ)), functional maturation (IV; SPD and SPZ), and recovery (V; SPD, SPZ, and SPG). During summer, fish had stage I and V testes and the lowest values in plasma levels of sex steroids and I G. Testicular recrudescence seemed to begin in autumn, as denoted by the first increase in I G and in the levels of 11-KT and T, and the appearance of testes at stage II and III. During winter, the levels of 11-KT and T peaked and soon began to decrease, the I G slightly declined and the proportion of running males (RM) gradually increased. In spring, levels of 11-KT and T continued to decline, the I G slightly increased and the proportion of RM peaked concomitantly with the occurrence of stage IV testes. Plasma levels of 17,20β-P did not change significantly throughout testicular development. Transformation of SPD into SPZ followed a group-synchronous fashion, a phenomenon which parallels asynchronous oocyte development reported in females. This mechanism would be consistent with the observed small quantity of sperm that can be manually stripped at any one time and other aspects of S. senegalensis reproductive biology.

Plasma Sex Steroid Levels and Steroidogenesis in the Gonad of the Self-fertilizing Fish Rivulus marmoratus

The mangrove killifish, Rivulus marmoratus, is the only known self-fertilizing vertebrate. This species is sexually dimorphic; sexually mature individuals are either hermaphrodite or primary and secondary males. Although the mangrove killifish has a unique reproductive strategy, there has been no study on the reproductive endocrinology of this species. Thus we investigated plasma sex steroid hormone levels and steroidogenesis in the gonads of R. marmoratus by enzyme linked immunosorbent assay (ELISA). Plasma 17β-estradiol (E2) and 11-ketotestosterone (11-KT) were detected both in hermaphrodite and in primary male. Ovarian follicles (follicle-enclosed oocytes) from hermaphrodites, which were categorized into early yolk stage and late yolk stage, and testis tissue of primary males were cultured with different concentrations of 17α-hydroxyprogesterone (OHP) or testosterone (T) for 24 h. Production of T, E2, 11-KT and 17α-20 β-dihydroxy-4-pregnen-3-one (17α,20β-P) in the medium from tissue culture were measured by ELISA. Early and late ovarian follicles of hermaphrodites and testis pieces of primary males synchronously secreted E2, 11-KT, and 17α,20β-P following incubation with OHP or T. We conclude that both hermaphrodite and primary male of the mangrove killifish secrete estrogen, androgen, and progestin synchronously.

Breast cancer, menopause, and long-term survivorship: critical issues for the 21st century

Breast cancer accounts for 33% of all incident cancers in women in North America, and there are an estimated >2 million breast cancer survivors in the United States today. Ovarian hormones are intimately involved in the initiation and promotion of breast cancer development, with targeted endocrine therapies being the most widely used as anticancer treatment. It is not surprising that these treatments frequently cause persistent menopausal symptoms in breast cancer survivors. In addition, adjuvant chemotherapy often induces premature menopause in younger patients with breast cancer. Some women at high risk for the development of breast cancer (e.g., precancerous breast disease, carriers of deleterious hereditary predisposition genes) experience vasomotor symptoms as a result of tamoxifen therapy or preventive oophorectomy. Clinical management of menopausal symptoms in these settings is complicated by the relative prohibition of hormonal therapies and the fact that breast cancer-directed therapies often exacerbate these menopausal symptoms. Thus, this special population of women requires unique management strategies and deserves separate consideration.

Non-invasive assessment of reproductive status and cycle of sex steroid levels in a captive wild broodstock of Senegalese sole Solea senegalensis (Kaup)

Senegalese sole, Solea senegalensis, intensive culture is currently limited mainly due to the low control on reproduction in captivity. Comprehensive knowledge of reproductive biology and physiology for this species is needed in order to improve tank spawning success. This work describes for the first time the seasonal profiles of plasma levels of sex steroids (17β-estradiol, testosterone, 11-ketotestosterone, and 17,20β-dihydroxy-4-pregnen-3-one [17,20β-P]) in a S. senegalensis captive wild broodstock held under natural conditions, during two consecutive reproductive cycles. Changes in apparent maturation in females, dynamics of sperm release in males, and the condition factor ( K) were monitored. Six maturation stages were established for females according to apparent size of the ovary and external abdominal swelling: early, intermediate and final ovarian development (F2+, F3+ and F4+, respectively), and partially spawned, mid spawned and spawned out or regressed (F3−, F2−, and F1−, respectively). During summer, F1− and non-running males (NRM) were predominant in association with low K and plasma steroid levels. At the end of summer, a new cycle of gonadal development started, denoted by the increase in reproductive parameters ( K and steroid levels) and the appearance of F2+. By middle autumn, some females reached advanced maturation stages (F3+ and F4+) while the proportion of running males (RM) showed a maximum. An occasional spawning could be registered during this season (November 2002). Towards the end of winter and beginning of spring, ovarian development reached its maximum. At this point, the proportion of F3+, F4+ and RM, K (specially in females), and steroid concentrations were the highest in concordance with the starting of the main spawning period (lasting from January to June 2003 and from March to June 2004). Throughout this period, concomitantly with oocyte and sperm release, the proportion of F3−, F2−, F1− and NRM progressively increased, while steroid levels and K progressively declined (concentration of steroids could fluctuate under a decreasing trend). The relatively elevated levels of 17,20β-P correlating with some parts of the spawning periods makes it a candidate for the role of the maturation-inducing steroid in S. senegalensis. Seasonal variations of measured parameters were consistent with the reproductive cycle of this species in the wild, and comparable to those found in other asynchronous multi-spawning fish.

Disparate effects of constant and annually-cycling daylength and water temperature on reproductive maturation of striped bass ( Morone saxatilis)

Adult striped bass ( Morone saxatilis) were exposed to various combinations of constant or anually-cycling daylength and water temperature. Constant conditions (15 h days, 18 °C) were those normally experienced at spawning and cycling conditions simulated natural changes at Chesapeake Bay latitude. Females exposed to constant long (15 h) days and cycling water temperature (TEMPERATURE group) had blood plasma levels of sex steroids (testosterone [T] and estradiol-17β [E 2]) and vitellogenin (Vg), and profiles of oocyte growth, that were nearly identical to those of females held under a natural photothermal cycle (CONTROL group). Several fish from these two groups were induced to spawn fertile eggs. Females constantly exposed to warm water (18 °C), with or without a natural photoperiod cycle (PHOTOPERIOD and STATIC groups, respectively), had diminished circulating levels of gonadal steroid hormones and Vg, impaired deposition of yolk granules in their ooplasm, and decreased oocyte growth, and they underwent premature ovarian atresia. Males exposed to cycling water temperature (CONTROL and TEMPERATURE groups) spermiated synchronously during the natural breeding season, at which time they also had had high plasma androgen (T and 11-ketotestosterone [11-KT]) levels. The timing of spermiation was highly asynchronous among males in groups of fish held constantly at 18 °C (STATIC and PHOTOPERIOD groups) and this asynchrony was associated with diminished plasma androgen levels. Termination of spermiation by males exposed to cycling water temperature coincided with a sharp decline in levels of plasma androgens about a month after water temperature rose above 18 °C. In contrast, most males held constantly at 18 °C sustained intermediate levels of plasma androgens and spermiated until the end of the study in late July. The annual cycle of water temperature clearly plays a prominent role in the initiation, maintenance, and termination of the striped bass reproductive cycle. In females, a decrease in water temperature below values experienced at spawning appears to be required for vitellogenesis and oocyte growth to proceed normally. Constant exposure of males to spawning temperature disrupts synchronous spermiation but also delays testicular regression, which may be useful for spawning fish after the natural reproductive season.

Existence of an extra-retinal and extra-pineal photoreceptive organ that regulates photoperiodism in gonadal development of an Osmerid teleost, ayu ( Plecoglossus altivelis)

Ayu ( Plecoglossus altivelis) is an Osmerid teleost whose gonadal development exhibits clear photoperiodism: it is stimulated and prevented under short and long photoperiod, respectively. However, the photoreceptor organ involved in this process remains to be identified. In the present study, we examined whether gonads of ophthalmectomized (Ex) and pinealectomized (Px) ayu respond to short photoperiod to test whether photoreceptors other than lateral eyes and pineal complex are involved in the photoperiodic response of gonadal development. Gonadosomatic index (GSI) and plasma levels of sex steroids (testosterone and 11-ketotestosterone for males and testosterone and estradiol 17-β for females) were significantly increased in the Ex+Px ayu kept under short photoperiod in both males and females as compared with the initial control. On the other hand, there were no significant increases in GSI and sex steroids in the Ex+Px ayu kept under long photoperiod. Histological observation of gonads in the Ex+Px ayu revealed that oocytes undergoing final maturation in females and proliferation of germ cells in males were observed under short photoperiod but not under long photoperiod. These results indicate that extra-retinal and extra-pineal photoreceptive organ regulates photoperiodic gonadal development in this species.

Growth, sex differentiation and gonad and plasma levels of sex steroids in male‐ and female‐dominant populations of Dicentrarchus labrax obtained through repeated size grading

Starting from 66 days post hatching (dph), European sea bass Dicentrarchus labrax were graded successively to create a fast growing (L‐extreme) and a slow growing (S‐extreme) population. The L‐extreme population grew significantly larger (ANOVA, n = 89–101, P < 0·01) attaining twice the wet mass of the S‐extreme population at 300 dph (130·9 ± 1·8 v. 66·7 ± 0·9 g, mean ± s.e.). When the two populations were sexed, the L‐extreme consisted of 96·5% and the S‐extreme of 30·2% females, while the ungraded control had 59·2% females. Sex differentiation began first in females at a total length (LT) of 97 ± 4 mm and wet mass of 9·4 ± 1·2 g (150 dph), and was completed when fish reached 166 ± 6 mm and 53·4 ± 6·4 g (250 dph) in both sexes. Precocious maturation in males was positively correlated to growth. Gonad oestradiol (E2) was significantly higher in the female‐dominant population at the onset of ovarian differentiation (ANOVA, n = 10, P < 0·05) and in the plasma after the appearance of the first primary oocytes (P < 0·01). Gonad testosterone (T) increased in both populations after sex differentiation (ANOVA, n = 10, P < 0·05), while plasma levels were significantly higher in the male‐dominant population (P < 0·001). Both gonad and plasma 11‐keto testosterone (11‐KT) were significantly higher in the male‐dominant population (ANOVA, n = 10, P < 0·01) reaching maximal values at spermiation. The results suggest that E2 is closely related with ovarian differentiation and the onset of oogenesis, while T and 11‐KT is more related to spermatogenesis and precocious maturation.

Diminished aromatase immunoreactivity in the hypothalamus, but not in the basal forebrain nuclei in Alzheimer’s disease

In previous studies we have shown in Alzheimer’s disease (AD) an enhanced nuclear estrogen receptor (ER) α expression in the cholinergic basal forebrain nuclei, i.e. the vertical limb of the diagonal band of Broca (VDB) and the nucleus basalis of Meynert (NBM), and in a number of hypothalamic nuclei, i.e. the supraoptic nucleus (SON), the infundibular nucleus (INF), the medial mamillary nucleus (MMN). We aimed at determining whether the increase in nuclear ERα seen in AD patients was related to a rise in local production of estrogens by aromatase (P-450arom), which is a key enzyme that catalyzes the biosynthesis of estrogens from precursor aromatizable androgens. We confirmed for the first time the presence of aromatase mRNA in neurons and glial cells in the human NBM and the tuberomamillary nucleus by RT–QPCR using laser microdissection. Enhanced aromatase immunoreactivity (ir) was indeed observed in the NBM in AD. However, in contrast a decreased aromatase-ir was found in the SON, INF and MMN of AD patients. In addition, P-450arom-ir was clearly diminished in ependymal and choroid plexus cells in AD. While an increase in aromatase-ir was found in the NBM and SON during normal aging, a decrease in staining was observed in the MMN. No sex differences in young control, elderly control or AD patients were present in any of the nuclei studied. In conclusion, brain P-450arom-ir and the relationship of its regulation with plasma sex steroid levels, estrogen and androgen receptors in the human hypothalamus and basal forebrain are region-specific.

Endocrine correlates of intra-specific variation in the mating system of the St. Peter's fish ( Sarotherodon galilaeus)

The Challenge Hypothesis postulates that androgen levels are a function of the social environment in which the individual is living. Thus, it is predicted that in polygynous males that engage in social interactions, androgen levels should be higher than in monogamous animals that engage in parental care. In this study, we tested this hypothesis at the intra-specific level using a teleost species, Sarotherodon galilaeus, which exhibits a wide variation in its mating system. Experimental groups of individually marked fish were formed in large ponds with different operational sex-ratios (OSR) to study the effects of partner availability on blood plasma levels of sex steroids [11-ketotestosterone (11-KT), testosterone (T), and 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P)] and gonadosomatic index (GSI). Polygyny mostly occurred in the female biased OSR groups. 17,20β-P and gonadosomatic index did not differ among OSR groups. However, 11-KT was high in male biased OSR and positively correlated with aggressive challenges, thereby supporting the central postulate of the Challenge Hypothesis. The results of T were the inverse of those of 11-KT, probably because 11-KT is metabolized from T. 11-KT levels of polygynous males did not differ neither from those of monogamous males, nor from those of males that participated in parental care. These results do not support the expected relationships between polygyny, parental care, and androgen levels. The differences from expectations for 11-KT may be related to the fact that in S. galilaeus, the mating and the parenting phase are not clearly separated and thus, males may still fight and court while they are brooding.

Variation of plasma sex steroid concentrations in wild and captive populations of Hermann’s tortoise ( Testudo hermanni hermanni) in Southern France

Plasma levels of sex steroids in both males and females of the endangered Hermann’s tortoise ( Testudo hermanni hermanni) were measured throughout their active period in a wild population in the Massif des Maures, France, and in a nearby captive population at Le Village des Tortues in Gonfaron. Both plasma progesterone and testosterone were elevated in males at emergence from winter dormancy, and plasma progesterone levels were significantly higher in wild than in captive males. Plasma testosterone in males then fell to the lowest levels (10 ng ml −1) during the nesting season from April to June followed by an elevated plateau during summer, with levels reaching 80 ng ml −1, presumably concomitant with spermiogenesis. Plasma testosterone increased in all females during autumn, an indication of follicular growth, and remained high on emergence from hibernation, to peak during April, although levels were lower in the captive population. Plasma progesterone also peaked during April and May, presumably related to ovulation, but, again, these changes were less marked in the captive than in the wild females. Measurements of testosterone, progesterone and 17β-oestradiol in the captive females during their period of oviposition in spring suggested that some females did ovulate and lay eggs, whereas others did not. Differences in sex steroid levels between captive and wild populations of Hermann’s tortoise may indicate a problem with ovulation and/or with stress in a proportion of captive females.

Effects of a phytosterol mixture on male fish plasma lipoprotein fractions and testis P450scc activity

Plant sterols (phytosterols) have been identified as one potential source of reproductive effects in fish living downstream of pulp mills. β-Sitosterol, the predominant plant sterol in pulp mill effluent, has previously been shown to decrease plasma sex steroid and cholesterol levels and in vitro gonadal steroid production in fish. In this study, male brook trout ( Salvelinus fontinalis) and goldfish ( Carassius auratus) were exposed to a phytosterol mixture (72% β-sitosterol) via Silastic intraperitoneal implants to help elucidate the mechanisms of action of phytosterols on steroid depression. As cholesterol is exogenously supplied for gonadal steroidogenesis, changes in plasma cholesterol fractions were examined. In male brook trout, low-density lipoprotein cholesterol and triglyceride levels decreased significantly, 43 and 50%, respectively, in phytosterol-treated fish. It is improbable, however, that these decreases are linked to depressed gonadal steroidogenesis in fish. The activity of P450scc, which converts cholesterol to pregnenolone (the first step in the steroidogenic pathway), was not affected in testis mitochondria isolated from brook trout or goldfish. Further investigation of the mechanisms of action of phytosterols is required.

Consenso sobre el diagnóstico y tratamiento de la pubertad precoz central

The beginning of puberty is marked by breast growth in girls and testicular enlargement in boys. These occur at the age of 10.5 +/- 2.0 years in females and 11.5 +/- 2.0 years in males. Recent but controversial publications suggest that these events are being observed at younger ages, at least in the USA. There are no studies demonstrating that this is true in Chile. For this reason we still consider that puberty is precocious when it occurs before 8.0 years in girls and before 9.0 years in boys. True or central precocious puberty (CPP) must be distinguished from peripheral or pseudoprecocious puberty (PPP), from premature telarche and from premature adrenarche. We suggest that the workup of a patient with premature development should include an LHRH test to demonstrate if the hypothalamic-pituitary axis is activated, plasma levels of sex steroids, bone age and pelvic ultrasound in girls. All children with CPP should have a CAT scan or MNR of the brain, since a lesion of the central nervous system is observed in 15% of the girls and 50% of the boys with CPP. Additional studies are needed in cases of PPP. The aim of treating CPP is to avoid adult short stature that results from premature fusion of the epiphysis and to avoid eventual emotional and psychological stress. Treatment consists of monthly intramuscular injections of a depot preparation of LHRH analogs. Suppression of pituitary and gonadal activity produces regression of secondary sex characteristics and slowing down of growth velocity and bone maturation. The opportunity, duration of treatment and their effect on final stature are discussed.

The existence of extra-retinal and extra-pineal photoreceptive organ regulating gonadal development of ayu, Plecoglossus altivelis

The photoreceptors regulating photoperiodic gonadal development of ayu, Plecoglossus altivelis, are not known. In this study, we examined whether the gonads of ophthalmectomized and pinealectomized (Ex+Px) ayu respond to short photoperiod. Gonadosomatic index (GSI) and plasma levels of sex steroids were significantly increased in Ex+Px ayu kept under short photoperiod in both males and females. On the other hand, there were no significant increase in GSI and sex steroids in Ex+Px ayu kept under long photoperiod. The histological observation of the gonads revealed that oocytes undergoing final maturation in females and proliferation of germ cells in males were observed only in Ex+Px ayu kept under short photoperiod. Altogether, our results strongly suggest unknown photoreceptive organ regulates photoperiodic gonadal development of ayu.

Methyltestosterone induces male sensitivity to both primer and releaser pheromones in the urine of ovulated female masu salmon

We investigated the optimum term of 17α-methyltestosterone (MT) -treatment for behavioral test and changes of plasma sex steroids levels in MT-treated immature male masu salmon, Oncorhynchus masou parr. Behavioral responses of MT-treated fish to the urine of ovulated or immature females were observed in an experimental trough. After 5 min of behavioral tests, plasma sex steroids levels were measured by RIAs. MT-treated fish showed specific behavioral responses to the ovulated female urine. MT-treated fish without exposure to the urine showed no clear changes in plasma 17,20β-dihydroxy-4-pregnene-3-one (DHP). However, plasma DHP in MT-treated fish increased when they were exposed to the urine.

The effects of photoperiod manipulation on the reproduction of black sea bass, Centropristis striata

The black sea bass, Centropristis striata, is a potential candidate for commercial aquaculture in the United States. One of the most significant constraints limiting commercial production of black sea bass is the lack of a reliable supply of eggs and larvae. A narrow window of annual spawning prevents year-round availability of juveniles for grow out. The present study reports on the use of photoperiod manipulation to alter the timing of spawning in C. striata and increase availability of larvae. Adult black sea bass were maintained under a simulated natural (SNP) or an accelerated long day (ALD) photoperiod regimen. Water temperature was adjusted from 14 to 20 °C to correspond to seasonal changes in daylength. Reproductive development was monitored by histological analysis of gonadal biopsies and plasma levels of sex steroids (estradiol-17β, testosterone and 11-ketotestosterone). Females in both regimens were induced to spawn by implantation of 25 μg luteinizing hormone-releasing hormone analogue (LHRHa) when follicle diameters exceeded 500 μm. Acceleration of the photoperiod advanced the annual cycle of circulating gonadal steroids in both sexes without altering the profile. The onset of spermiation in males was unaffected by photoperiod manipulation, but follicle growth and spawning in females were advanced approximately 2 months by exposure to the ALD regimen. Of interest, the ALD photoperiod regimen accelerated the time frame of sexual succession from female to male without reducing the mean volume of eggs produced per female. These findings suggest that photoperiod manipulation can be used to alter the timing of reproduction in black sea bass and increase the supply of eggs for commercial aquaculture.

Plasma vitellogenin levels in male common carp Cyprinus carpio and crucian carp Carassius cuvieri of Lake Kasumigaura

: In order to investigate the possible influence of estrogenic environmental endocrine disruptors on the reproductive activity of fish in Lake Kasumigaura, plasma levels of vitellogenin (VTG), a biomarker of estrogen exposure, were measured in wild and cultured male common carp Cyprinus carpio and wild crucian carp Carassius cuvieri. Testicular histology and plasma steroid hormone levels were also examined. Fish were collected from June 1998 to August 1999. Plasma VTG levels in most fish examined were below a detection limit (40 ng/mL) throughout the sampling period, and a small amount of VTG (43.5 ng/mL–1680 ng/mL) compared to that in females was detected in some fish. Active spermatogenesis in the testis and increased levels of plasma sex steroids were observed in most of the fish examined. Thus, no marked influence of estrogenic chemicals was detected in the reproductive activity of male common carp and crucian carp in Lake Kasumigaura collected from the sampling sites in the present investigation.

Members of opposite sex mutually regulate gonadal recrudescence in the lizardCalotes versicolor (Agamidae)

Adult males and females of the seasonally breeding lizard Calotes versicolor were subjected to various social situations under semi-natural conditions to explain the role of socio-sexual factors in gonadal recrudescence. They were grouped as: (i) males and females, (ii) males and females separated by a wire mesh, (iii) same sex groups of males or females, (iv) castrated males with intact females and (v) ovariectomized (OvX) females with intact males from postbreeding to breeding phase. Specimens collected from the wild during breeding season served as the control group. Plasma sex steroid levels (testosterone in male and 17b-estradiol in female), spermatogenetic activity and vitellogenesis were the criteria to judge gonadal recrudescence. In intact males and females that were kept together, gonadal recrudescence and plasma sex steroids levels were comparable to those in wild-caught individuals. Gonadal recrudescence was at its least in all male and all female groups, and plasma sex steroids were at basal levels. Association with OvX females initiated testicular recrudescence but spermatogenetic activity progressed only up to the spermatid stage while males separated from females by wire mesh showed spermatogenetic activity for a shorter period. Females grouped with castrated males and those separated from males by wire mesh produced vitellogenic follicles. However, the total number and diameter of vitellogenic follicles, and plasma estradiol levels were lower than in the females grouped with intact males. The findings indicate that association with members of the opposite sex with progressively rising titers of sex steroids is crucial in both initiating and sustaining gonadal recrudescence in the lizard. Thus, members of the opposite sex mutually regulate gonadal recrudescence in the C. versicolor.

Potential Classification of Sex and Stage of Gonadal Maturity of Wild White Sturgeon Using Blood Plasma Indicators

Because white sturgeon Acipenser transmontanus show no readily discernible external signs of gender, management agencies use surgical biopsies to determine the sex and stage of gonadal maturity of individuals. This procedure is highly invasive and can be difficult under field conditions. Therefore, gonadal tissue and blood were collected from white sturgeon captured in tribal and commercial fisheries (fishery fish) and by fish and wildlife agencies (oversize fish) in the Columbia River basin to develop a method of determining sex and stage of maturity using the blood plasma indicators testosterone (T), 11-ketotestosterone (KT), estradiol (E2), and calcium (Ca2+). The sex and stage of maturity was determined by histology or by visual examination in maturing fish. Plasma sex steroid levels were measured by radioimmunoassay, and plasma Ca2+ was measured spectrophotometrically. White sturgeon showed sex- and maturity-specific levels of steroids and Ca2+. Stepwise discriminant function analysis (DFA) was used to choose the best variable(s) for predicting sex and stage of maturity, and quadratic DFA was conducted to classify fish into two groups of sex or four groups of sex and stage of maturity. In the classification of the fishery plus oversize fish, plasma T and E2 were the best predictors of sex and stage of maturity. Of the 151 females and 106 males, 85% of the females and 79% of the males were correctly classified; 88, 72, 98, and 96% of the immature females, immature males, maturing females, and maturing males, respectively, were correctly classified. The greatest error of misclassification occurred with immature males classified as immature females. In the analysis of immature fishery fish only, plasma T and fork length led to the correct classification of 88% of the females and 86% of the males. In the analysis of oversize fish only, 100% of the females and 95% of the males were correctly classified using plasma T and E2; 93, 100, 98, and 100% of the immature females, immature males, maturing females, and maturing males, respectively, were correctly classified using these variables. The derived classification functions for the prediction of sex or sex and maturity may replace the need for surgical biopsies if the error associated with the misclassification of immature fish is acceptable.