Gonadal Growth Research Articles

Region-Wide Reproductive Disruption, Masculinization and Aromatase Suppression in Marine Fish Collected from a Coastal Hypoxic Zone.

One of the most dramatic global changes due to human activities over the last half century has been the marked increase in the extent of seasonal coastal hypoxia (dissolved oxygen, DO < 2 mg O2/L) which now affects over 400 regions and covers a total area of about 250,000 sq.km. The long-term impacts on marine ecosystems of this dramatic worldwide increase in coastal hypoxia are unknown. Here we show widespread reproductive disruption in Atlantic croaker collected from hypoxic sites 120 km apart in the extensive hypoxic region in the northern Gulf of Mexico, the second largest hypoxic region in the world. Gonadal growth and gamete production were impaired in croaker from hypoxic sites compared to fish from reference normoxic sites. Male germ cells were detected in 16-24% of croaker ovaries collected in the hypoxic region, but were absent in croaker ovaries from normoxic sites. In addition, the sex ratio was skewed towards males at the hypoxic sites. The masculinization and other reproductive disruptions were associated with declines in neuroendocrine function as well as ovarian and brain expression of aromatase, the enzyme that is critical for ovarian differentiation in fish. A similar incidence of intersex and decline in ovarian aromatase expression was observed in croaker after chronic laboratory exposure to hypoxia, indicating that masculinization of ovaries is a specific response to hypoxia and is due to decreased aromatase activity. The results suggest that severe reproductive impairment can occur over large coastal regions in marine fish populations exposed to seasonal hypoxia, with potential long-term impacts on population abundance. (poster)

The influence of temperature and presence of predators on growth, survival and energy allocation for reproduction in the Catarina scallop Argopecten ventricosus

Environmental factors are known to modify the life history of marine ectotherms. In a 16-month laboratory experiment, we investigated the influence of temperature and presence of predators on life-history parameters including shell growth, survival and the energy investment in reproduction and body mass of the short-lived (2–3 years) scallop Argopecten ventricosus. In parallel, A. ventricosus was maintained in the field at the Pacific coast of Baja California, México, to compare growth, survival and reproductive effort under natural conditions. For the laboratory treatments, scallops were reared at simulated field temperatures (SFT), 5 °C above SFT and in the presence of predators. Elevated water temperatures caused higher growth and gonad production, although at the cost of increased mortality. Presence of predators induced energy allocation to muscle rather than gonad growth, deferred spawning and extended survival. Field scallops exhibited higher growth, higher reproductive investment and were able to reproduce twice, whereas all laboratory scallops died after the first spawning. The natural variability of environmental parameters such as food and temperature may thus support optimal growth in the field, and when animals are protected from predators, reproduction in the second year of life.

Extensive reproductive disruption, ovarian masculinization and aromatase suppression in Atlantic croaker in the northern Gulf of Mexico hypoxic zone.

The long-term impacts on marine ecosystems of the recent dramatic worldwide increase in the incidence of coastal hypoxia are unknown. Here, we show widespread reproductive disruption in Atlantic croakers collected from hypoxic sites approximately 120 km apart in the extensive northern Gulf of Mexico continental shelf hypoxic zone. Gonadal growth and gamete production were impaired in croakers from hypoxic sites compared with fish from reference normoxic sites east of the Mississippi River Delta. Male germ cells were detected in approximately 19 per cent of croaker ovaries collected in the hypoxic region, but were absent in ovaries from normoxic sites. In addition, the sex ratio was skewed towards males at the hypoxic sites. The masculinization and other reproductive disruptions were associated with declines in neuroendocrine function, as well as ovarian and brain expression of aromatase (the enzyme that converts androgens to oestrogens). A similar incidence of ovarian masculinization and decline in ovarian aromatase expression were observed in croaker after chronic laboratory hypoxia exposure, indicating that ovarian masculinization is a specific hypoxia response and is due to decreased aromatase activity. The results suggest severe reproductive impairment can occur over large coastal regions in marine fish populations exposed to seasonal hypoxia, with potential long-term impacts on population abundance.

Echinoderm Phylogeny Including Xyloplax, a Progenetic Asteroid

Reconstruction of the phylogeny of the five extant classes of the phylum Echinodermata has proven difficult. Results concerning higher-level taxonomic relationships among echinoderms are sensitive to the choice of analytical parameters and methods. Moreover, the proposal of a putative sixth class based on a small enigmatic disc-shaped echinoderm, Xyloplax, from the deep seas of the Bahamas and New Zealand in the 1980s further complicated the problem. Although clearly an echinoderm, Xyloplax did not have clear affinity among known groups. Using molecular sequence and developmental data from recently collected Xyloplax adults and embryos, we show that rather than representing an ancient distinct lineage as implied by its status as a class, Xyloplax is simply a starfish that is closely related to the asteroid family Pterasteridae. Many members of the Pterasteridae and all Xyloplax inhabit deep or polar seas and brood young. Brooding pterasterids and Xyloplax hold their young in specialized adult chambers until the young reach an advanced juvenile stage after which they are released as free-living individuals. We hypothesize that the unique morphology of Xyloplax evolved via progenesis--the truncation of somatic growth at a juvenile body plan but with gonadal growth to maturity. Although the overall phylogeny of extant echinoderms remains sensitive to the choice of analytical methods, the placement of Xyloplax as sister to pterasterid asteroids is unequivocal. Based on this, we argue that the proposed class and infraclass status of Xyloplax should be suppressed.

Development of natural growth regimes for hatchery-reared steelhead to reduce residualism, fitness loss, and negative ecological interactions

Wild steelhead (Oncorhynchus mykiss) typically spend two or more years in freshwater before migrating to sea, but hatchery steelhead are almost ubiquitously released as yearlings. Their large size at release coupled with life history pathways that include both male and female maturation in freshwater present ecological risks different from those posed by hatchery populations of Pacific salmon. Yearling hatchery reared steelhead that fail to attain minimum thresholds for smoltification or exceed thresholds for male maturation tend to ‘residualize’ (i.e., remain in freshwater). Residuals pose ecological risks including size-biased interference competition and predation on juvenile salmon and trout. Three hatchery populations of steelhead in Hood Canal, WA were reared under growth regimes designed to produce a more natural age at smoltification (age-2) to aid in rebuilding their respective natural populations. Mean smolt sizes and size variability at age-2 were within the range of wild smolts for two of the three populations. The third population reared at a different facility under similar temperatures exhibited high growth rate variability and high male maturation rates (20% of all released fish). Experimentally comparing age-1 and age-2 smolt programs will help identify optimal rearing strategies to reduce the genetic risk of domestication selection and reduce residualism rates and associated negative ecological effects on natural populations. Investigations of Winthrop National Fish Hatchery summer-run steelhead will measure a) selection on correlated behavioral traits (‘behavioral syndromes’), b) degree of smoltification, c) changes in hormones that regulate gonad growth at key developmental stages, and d) conduct extensive post-release monitoring of fish reared under each growth regime.

Patterns of investment in reproductive and somatic tissues in the loliginid squid Loligo forbesii and Loligo vulgaris in Iberian and Azorean waters

The veined squid, Loligo forbesii, is found throughout the northeast Atlantic, including the waters off the Iberian Peninsula, and is a socio-economically important cephalopod species, sustaining several small-scale commercial and local artisanal fisheries. This study uses Iberian and Azorean trawl survey and fishery landings data from 1990 to 1992 and employs additive modelling to examine the relationships amongst somatic growth, season and gonad growth, in an attempt to determine the relative importance of intrinsic (e.g. nutritional state and body size) and extrinsic (temperature and daylight) factors which contribute to maturation in L. forbesii. We compare the results with those from a comparative analysis of contemporaneous data on Loligo vulgaris from the Iberian coast, and with a re-analysis of previously published results for L. forbesii in Scottish waters. Reproductive organ weight in both sexes of L. forbesii from all ports shows seasonal patterns with a fall/winter peak in maturation, as is expected with the animals’ year-long life cycle. Two maturity peaks (spring and winter) were found for both Azores L. forbesii males and females, possibly evidence of two breeding cohorts, with males maturing approximately 1 month earlier than females in both seasons. For L. vulgaris, three annual peaks in reproductive weight were identified. With the exception of L. forbesii males from Scottish waters, in all study animals, the partial effect of mantle length and mantle weight on reproductive weight is positive up to large body sizes. The relationship between nutritional status and reproductive weight is also generally positive. Geographic variation in the relationships, as seen between Scottish males and samples from the other study areas, is hypothesised to be largely attributable to local differences in environmental conditions (productivity, food availability, temperature, upwelling), although differences between L. forbesii from the Azores, Scotland and mainland Europe may also relate to previously documented genetic differences.

Agar-based pellets as feed for sea urchins (Paracentrotus lividus): rheological behaviour, digestive enzymes and gonad growth

The algal polysaccharide agar has long been used as a food binder due to its structure, rheological behaviour, stability and interactions – properties that help to generate firm, round, disk-shaped pellets that may be used in recirculating sea urchin-rearing systems. Three algae-based diets (Ulva lactuca, Gracilaria gracilis, Cystoseira sp.) containing 3% and 6% agar were tested on the sea urchin Paracentrotus lividus in order to examine the effect of varying percentages of agar on pellet stability in water and sea urchin gonad growth. The kinetics of water absorption and solute leaching of pellets were measured by immersing quadruplicate samples of the pellets in water for 1, 2, 3, 4, 5 and 6 days. Our results show that the pellets had good water stability, were readily consumed by sea urchins and the presence of agar did not hamper sea urchin gonad growth. Animals fed Ulva-containing pellets reached a more advanced gametogenic stage with respect to animals fed Cystoseira- and Gracilaria-containing pellets. Moreover, the presence of agarase activity in the digestive system indicated that agar may be an energy source. Pellets are relatively low cost and easy to prepare and store. They may represent a useful resource for rearing sea urchins under intensive conditions.

Genetic variation in cue sensitivity involved in avian timing of reproduction

1. Annual variation in the timing of avian reproduction is associated with predictive cues related to ambient temperature. Understanding how these cues affect timing, and estimating the genetic variation in sensitivity to these cues, is essential to predict the micro-evolutionary changes in timing which are needed to adapt to climate change. 2. We carried out a 2-year experiment with great tits Parus major of known genetic background, which were kept in pairs in climate-controlled aviaries with simulated natural photoperiod and exposed to a seasonal change in temperature, where the two treatments differed by 4 °C. We recorded the dates of laying the first and last eggs and timing of moult, as well as physiological proxies associated with reproduction: plasma luteinizing hormone (LH), prolactin, and gonadal size at four-weekly intervals. 3. The temperature treatments did not affect first-egg dates, nor gonadal growth or plasma LH and prolactin concentrations. However, birds terminated egg laying, regressed their testes and started their moult earlier at higher temperatures. 4. There were marked family differences in both the start of egg laying, with sisters from early laying maternal families laying early, and in the termination of laying, indicating that there is heritable variation in sensitivity to cues involved in timing. 5. Our experiment, the first to use genetically related individuals in an experimental design with a natural change in photoperiod and biologically realistic temperature differences, thus shows that genetic adaptation in cue sensitivity is possible, essential for species to be able to adapt to a warming world.

Prior residency advantage for Atlantic salmon in the wild: effects of habitat quality

Prior residency advantages have been explained by an asymmetry between the ‘owner’ and the ‘intruder’ in fighting ability (resource-holding potential) or motivation (value asymmetry (VA)). Here, we tested for the extent of prior residence effects in individually tagged Atlantic salmon juveniles being released in two bouts (4 days apart) during spring along a natural stream, and recaptured 3 months later. A prior residency advantage was detected both in terms of body growth, energy density and male gonad size. As we controlled for effects of initial body size, which correlates with dominance, these findings are in accordance with the VA hypothesis. The growth advantage of first arrivals also increased with local shelter abundance in the stream, which can be expected if a higher resource value of the habitat results in a higher defence motivation. We also found a prior residence effect on spatial distribution, with the second arrivals within each release site being recaptured further downstream. No effect on apparent survival rates was found. The observed reduced growth and energy density may have fitness consequences for the second arrivals, both in terms of lower winter survival rates and later age at maturity. For mature male parr, both decreased body and gonad growth may give an additional disadvantage through reduced fertilization rates during breeding. These costs may help to explain the tendency for stationary behaviour of stream salmonids, as the potential benefits of moving into less crowded areas would be reduced by the risk of becoming an intruder. Prior residence effects may therefore have influenced the evolution of movement behaviour in these organisms.

A Standardized Terminology for Describing Reproductive Development in Fishes

AbstractAs the number of fish reproduction studies has proliferated, so has the number of gonadal classification schemes and terms. This has made it difficult for both scientists and resource managers to communicate and for comparisons to be made among studies. We propose the adoption of a simple, universal terminology for the phases in the reproductive cycle, which can be applied to all male and female elasmobranch and teleost fishes. These phases were chosen because they define key milestones in the reproductive cycle; the phases include immature, developing, spawning capable, regressing, and regenerating. Although the temporal sequence of events during gamete development in each phase may vary among species, each phase has specific histological and physiological markers and is conceptually universal. The immature phase can occur only once. The developing phase signals entry into the gonadotropin‐dependent stage of oogenesis and spermatogenesis and ultimately results in gonadal growth. The spawning capable phase includes (1) those fish with gamete development that is sufficiently advanced to allow for spawning within the current reproductive cycle and (2) batch‐spawning females that show signs of previous spawns (i.e., postovulatory follicle complex) and that are also capable of additional spawns during the current cycle. Within the spawning capable phase, an actively spawning subphase is defined that corresponds to hydration and ovulation in females and spermiation in males. The regressing phase indicates completion of the reproductive cycle and, for many fish, completion of the spawning season. Fish in the regenerating phase are sexually mature but reproductively inactive. Species‐specific histological criteria or classes can be incorporated within each of the universal phases, allowing for more specific divisions (subphases) while preserving the overall reproductive terminology for comparative purposes. This terminology can easily be modified for fishes with alternate reproductive strategies, such as hermaphrodites (addition of a transition phase) and livebearers (addition of a gestation phase).

Geographic, population, and seasonal patterns in the reproductive parameters of the sea urchin Paracentrotus lividus

Generalized additive models were used to synthesize the data from 52 publications on the gonad growth and spawning seasonality of Paracentrotus lividus and identify spatial and temporal patterns in the reproductive processes. According to our results, Atlantic populations spawn in spring and develop large gonads (6.4 ± 0.2% of fresh body weight (mean ± SE)), which increase in size toward higher latitudes. While in the Mediterranean, the gonads are smaller (3.1 ± 0.1%), possibly as the result of successive spawnings which impede nutrients accumulating in the gonads. Differences were also observed between habitats: gonad production was higher in seagrass meadows in the Mediterranean and in subtidal rocky substrates in the Atlantic. Food availability might cause these variations as well as the negative correlation observed between depth and the gonad index for rocky substrates. Sex and body size do not seem to influence greatly gonad growth.

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.

Cloning and sequence analysis of a vasa homolog in the European sea bass ( Dicentrarchus labrax): Tissue distribution and mRNA expression levels during early development and sex differentiation

Vasa is a protein expressed mainly in germ cells and conserved across taxa. However, sex-related differences and environmental influences on vasa expression have not been documented. This study characterized the cDNA of a vasa homolog in the European sea bass, Dicentrarchus labrax ( sb-vasa), a gonochoristic fish with temperature influences on gonadogenesis. The 1911 bp open reading frame predicted a 637-amino acid protein with the eight conserved domains typical of Vasa proteins. Comparisons of the deduced amino acid sequence with those of other vertebrates and invertebrates revealed the highest homology (68–85%) with those of other teleosts. An updated tree with the full-length sequences for Vasa proteins in 66 species belonging to six different phyla was constructed, establishing the evolutionary relationships of Vasa amino acid sequences. European sea bass vasa was highly expressed in gonads with little or no expression in other tissues. Real time RT-PCR quantification of the temporal expression of sb-vasa from early development throughout sex differentiation showed that mRNA levels were high in unfertilized eggs, decreased during larval development and increased again during the period of germ cell proliferation. Rearing of fish at high temperature resulted in further increased sb-vasa levels, most likely reflecting temperature effects on both somatic and gonadal growth. Differences in expression were also found well before sex differentiation and persisted until the end of the first year, with higher levels present in females. These differences in expression demonstrate the implication of vasa during the initial stages of fish sex differentiation and gametogenesis and suggest that, through its helicase activity, it might be implicated in the translational regulation of mRNAs involved in the specification and differentiation of gonadal-specific cell types.

Gonadal development in male and female domesticated whiteleg shrimp, Litopenaeus vannamei, in relation to age and weight

Cultivation of whiteleg shrimp ( Litopenaeus vannamei) is now entirely based on closed life-cycle populations, yet few studies have analyzed gonadal development in domesticated shrimp during grow-out in ponds. To determine the effect of age and weight on morphometric, histological, and biochemical variables associated with male and female gonadal development, shrimp from the same cohort, at ages of 6, 8, 10, and 12 months were examined using body weight as a covariable in an ANCOVA design. An additional comparison between two grow-out conditions in 1-year-old shrimp was done to separate the effect of size as a result of initial stocking densities. Age-related growth of gonads was clearly dependent on somatic growth for females but not for males, although differential somatic growth produced by stocking densities explained differences in growth of gonads for both sexes. Increase in oocyte diameter and differentiation associated with age and grow-out condition were independent of body weight. Age-related female gonadal development was accompanied by increases in lipid and protein concentrations, independent of body weight. Maturation of male reproductive organs (testicle, vas deferens, terminal ampoule, and spermatophore) was sequential and depended mainly on age, although body weight could explain differences caused by different grow-out conditions. An age-related decrease in concentration of lactate occurred in all male reproductive organs and could indicate a metabolic adjustment of sperm anaerobic metabolism and lactate clearance associated with gonadal development. We highly recommend waiting for optimal reproductive potential of females at 12 months to enhance spawning frequency and larval quality. At this age, body weight seems to be of secondary importance, although optimal conditions of cultivation are necessary to have adequate growth and balanced nutrition.

Long-Term Outcome of Pituitary-Gonadal Axis and Gonadal Growth in Patients With Hypospadias at Puberty

Reports of pubertal hormonal and gonadal status in patients with hypospadias are scarce. We evaluated the pituitary-gonadal axis and gonadal growth in patients with hypospadias at puberty. We retrospectively reviewed serum luteinizing hormone, follicle-stimulating hormone, testosterone and testicular volume at puberty (age 15 years or greater) in the medical charts of patients with hypospadias treated since 1986 and followed at our institution. Enrolled in this study were 43 patients with a mean age at evaluation of 17.6 years (range 15.1 to 22.8). Of these patients 14 and 29 were treated for mild and severe hypospadias, respectively. Six patients with severe hypospadias underwent bilateral orchiopexy for bilateral undescended testes. All patients were Tanner stage 4 to 5 at evaluation. Of 14 mild hypospadias cases we noted hypergonadotropic hypogonadism, hypogonadotropic hypogonadism, decreased luteinizing hormone and decreased testosterone in 1 each (7% each). Of 23 severe hypospadias cases without bilateral undescended testes we noted hypergonadotropic hypogonadism, partial androgen insensitivity syndrome and decreased testosterone in 2 (9%), 1 (4%) and 1 (4%), respectively. Of 6 patients with severe hypospadias and bilateral undescended testes we noted hypergonadotropic hypogonadism in 1 (17%) and increased luteinizing hormone with normal testosterone in 2 (33%). Testicular volume less than 10 ml with increased follicle-stimulating hormone was identified in 7 of 43 patients, including 1 of 14 (7%) with mild hypospadias, 3 of 23 (13%) with severe hypospadias without bilateral undescended testes and 3 of 6 (50%) with severe hypospadias and bilateral undescended testes. Our study revealed endocrine dysfunction in patients with mild and severe hypospadias at puberty even without an undescended testis. Of these patients those with severe hypospadias and an undescended testis may be at higher risk for impaired spermatogenesis.

Effects of nutrition on somatic growth and reproductive strategy of the sea urchin Pseudechinus huttoni

This study aimed to understand how resource allocation to somatic and gonadal tissues of the sea urchin Pseudechinus huttoni was influenced by nutritional status using several methods. Urchins in the laboratory were fed kelp (Macrocystis pyrifera) four days a week as the low-quality diet group, or a mixture of kelp and cockle flesh (Austrovenus stutchburyi) once a week, as the high-quality diet group. The experiment lasted for one year. The gonad, gut, lantern, test, lantern muscle indices and gametogenic stage were measured at 3 weeks and 6 and 12 months after the start of the experiment. A high-quality diet led to higher gonad (only in females) and gut indices but lower lantern, lantern muscles and test indices. Females allocated a higher percentage of energy to the gonad when fed a high-quality diet but a higher percentage of energy to the test when fed a low-quality diet. Dietary condition had no influence on gametogenic stages; however, the urchins fed a high-quality diet had larger oocytes. The gonadal growth appears not to have priority over somatic growth in P. huttoni and more energy resources are allocated to the test when food is limited.

Growth, hatch size and maturation in a southern population of the loliginid squidLoliolus noctiluca

Age, growth and cost of reproduction were examined for the small near-shore loliginid squidLoliolus noctilucain Tasmanian waters, near the southern limit of its distribution. The effects of several factors on hatch size were also evaluated by comparing the statolith natal ring size (NR) from individuals collected in different locations, seasons and years. The life cycle ofL. noctilucawas less than six months. July-hatched females grew faster than their May-hatched counterparts, indicating a faster growth in winter-hatched compared with autumn-hatched individuals. There was considerable variation in NRs as function of location, season, year and sex, with females displaying NRs considerably larger than males in any location and year. Immature and maturing females displayed poorer body condition than mature counterparts, suggesting that gonad growth does not affect the mantle or fin growth. A good condition was maintained also in spent individuals indicating thatL. noctilucacontinued to invest in somatic organs throughout the spawning period. A reproductive strategy closer to ‘multiple spawning’, than to ‘single spawning’ was proposed for this species.Loliolus noctilucawas used as a model to explore the possible effects of climate change on near-shore loliginid populations.

Photoperiodic Modulation of Clock Gene Expression in the Avian Premammillary Nucleus

The premammillary nucleus (PMM) has been shown to contain a daily endogenous dual-oscillation in dopamine (DA)/melatonin (MEL) as well as c-fos mRNA expression that is associated with the daily photo-inducible phase of gonad growth in turkeys. In the present study, the expression of clock genes (Bmal1, Clock, Cry1, Cry2, Per2 and Per3) in the PMM was determined under short (8 : 16 h light/dark cycle) and long (16 : 8 h light/dark cycle) photoperiods relative to changes associated with the diurnal rhythm of DA and MEL. Constant darkness (0 : 24 h light/dark cycle) was used to assess the endogenous response of clock genes. In addition, light pulses were given at zeitgeber time (ZT) 8, 14 and 20 to ascertain whether clock gene expression is modulated by light pulse stimulation and therefore has a daily phase-related response. In the PMM, the temporal clock gene expression profiles were similar under short and long photoperiods, except that Per3 gene was phase-delayed by approximately 16 h under long photoperiod. In addition, Cry1 and Per3 genes were light-induced at ZT 14, the photosensitive phase for gonad recrudescence, whereas the Clock gene was repressed. Gene expression in established circadian pacemakers, the visual suprachiasmatic nucleus (vSCN) and the pineal, was also determined. Clock genes in the pineal gland were rhythmic under both photoperiods, and were not altered after light pulses at ZT 14, which suggests that pineal clock genes may not be associated with the photosensitive phase and reproductive activities. In the vSCN, clock gene expression was phase-shifted depending on the photoperiod, with apexes at night under short day length and during the day under long day length. Furthermore, light pulses at ZT 14 induced the Per2 gene, whereas it repressed the Bmal1 gene. Taken together, the changes in clock gene expression observed within the PMM were unique compared to the pineal and vSCN, and were induced by long photoperiod and light during the daily photosensitive phase; stimuli that are also documented to promote reproductive activity. These results show that Cry1 and Per3 are involved in the photic response associated with the PMM neuronal activation and are coincident with an essential circadian mechanism (photosensitive phase) controlling the reproductive neuroendocrine system.

Seasonal variations and alterations of sex steroid levels during the reproductive cycle of male roach ( Rutilus rutilus)

Seasonal variations of plasma steroid concentrations i.e. progesterone (P), 11-ketotestosterone (11-KT) and 17-β-estradiol (E2) were determined immunoenzymatically during a whole reproductive cycle in male roach ( Rutilus rutilus) caught in a reference site. Plasma 11-KT concentrations were significantly correlated with gonad growth, expressed as the gonado-somatic index ( R 2 = 0.60; p < 0.05) and highest concentrations (757 ± 99 pg ml −1) coincided with the final testis maturation in March. E2 and P concentrations peaked once during the reproductive cycle. E2 synthesis was significantly induced during the spawning period while P concentration peaked at the very start of the gametogenesis (June) thus suggesting specific roles of these steroids in the reproductive cycle. Comparison of reference levels were then made with plasma steroid concentrations from male roach sampled in polluted areas in the North of France. A significant decrease of E2 (50–60%) and 11-KT (76–84%) was measured, indicating that endocrine disrupting compounds may have interfered with the normal sex steroid synthesis. Contrary to the E2 and 11-KT sex steroids, plasma P concentration was not significantly affected in fish inhabiting impacted areas.

An experimental assessment on the effects of photoperiod treatments on the somatic and gonadal growth of the juvenile European purple sea urchinParacentrotus lividus

Determining the optimum light conditions for sea urchins reared in land-based systems is vital for the future use and assessment of possible commercial systems of sea urchin farming. The effects of two different light regimes, complete darkness and a long day photoperiod of 16 h light:8 h darkness, on the somatic and gonadal growth of the European sea urchin Paracentrotus lividus (19.5–23.0 mm) was investigated using the commercial UrchinPlatter™ System over a 6-month period (5 March to 5 September). Hatchery-produced P. lividus were transported to the Aquaculture Fisheries Development Centre (AFDC, University College, Cork UCC). Before arrival at the AFDC, sea urchins were reared on a diet of Laminaria digitata. Females were the predominant species of the animal group, displaying a reproductive Stage III (growing stage) where gametogenesis was commencing. Results show that darkness supports higher somatic growth than the photoperiod treatment. Feeding rates were higher for sea urchins reared under darkness with gonadal growth increasing for both experimental treatments. Individuals reared under darkness had a higher per cent change in gonad index from the initial sample taken at the beginning of the experiment.