Late Vitellogenic Oocytes Research Articles

Chronic exposure to gestodene impairs reproductive system in adult female zebrafish (Daniarerio)

Gestodene (GES) is widely used in human therapy and animal husbandry and is frequently detected in aquatic environments. Although GES adversely affects aquatic organisms at trace levels, its effects on the reproductive biology of fish remain inconclusive. In this study, female zebrafish (Danio rerio) were exposed to environmentally relevant levels of GES for the evaluation of the effects of GES on the reproductive system by using endpoints including gene expression, plasma steroid concentrations, histological and morphological analyses, copulatory behavior, and reproductive output. Adult female zebrafish exposed to environmentally relevant concentrations of GES (4.0, 40.2, and 372.7 ng/L) for 60 d demonstrated stagnant ovarian oocyte development, evidenced by an increase in the percentage of perinuclear and atretic oocytes and a decrease in the percentage of late vitellogenic oocytes. GES-exposed females were less attractive to males and had lower copulatory intimacy than females in control. Consequently, spawning (44.3–49.2 %) and egg fertilization rates (27.9–32.0 %) were decreased. The decreased survival of fertilized eggs and hatching rates were accompanied by increased malformations. These negative effects were associated with abnormal transcriptional levels of gonadal steroid hormones, which were regulated by genes (Hsd17β3, Hsd11β2, Hsd20β, Cyp19a1a, and Cyp11b). Overall, our findings suggest that GES impairs the reproductive system of zebrafish, which may threaten population stability.

Influence of Hormonal Stimulation on the Oocyte Chromosome Apparatus of the Common Frog

Late vitellogenic oocytes of the common frog, Rana temporaria, represent a promising model for studying the behavior of meiotic chromosomes, since at the diplotene stage, they unite into a karyosphere, which in R. temporaria is believed to have an extrachromosomal capsule – unlike in Xenopus laevis, a classic model object of cell biology and developmental biology. However, in comparison with Xenopus, the strict breeding seasonality of R. temporaria significantly limits the possibility of using its oocytes as an experimental model. By adapting classical hormonal stimulation protocols proposed for anurans including Xenopus, we were able to obtain R. temporaria oocytes with a fully developed karyosphere outside the breeding season, namely in December–January. We observed pronounced changes in the chromosomal apparatus of oocytes with a double injection of human chorionic gonadotropin (hCG) at a dose of 500 IU. In this case, chromosomes undergo compaction and aggregation, leading to the formation of a characteristic chromosomal “knot” (karyosphere), the morphological features of which corresponded to those in R. temporaria oocytes at the beginning of the natural breeding season. Based on the proposed protocol for the use of hCG for out-of-season stimulation of oogenesis in R. temporaria, it can be further refined to obtain more stable results and improve the quality of oocytes.

Exposure to difenoconazole induces reproductive toxicity in zebrafish by interfering with gamete maturation and reproductive behavior.

Difenoconazole (DCZ) is a triazole fungicide that negatively affects aquatic organisms and humans. However, data regarding the reproductive toxicity of DCZ are insufficient. In this study, we used zebrafish (from 2 h post-fertilization [hpf] to adulthood) as a model to evaluate whether DCZ at environmentally relevant concentrations (0.1, 1.0, and 10.0 μg/L) induces reproductive toxicity. After exposure to DCZ, egg production and fertilization rates were reduced by 1.0 and 10.0 μg/L. A significant decrease in gamete frequency (late vitellogenic oocytes and spermatozoa) was observed at 10.0 μg/L. The concentrations of 17β-estradiol (E2), testosterone (T), and vitellogenin (VTG) were disrupted in females and males by 1.0 and 10.0 μg/L. Exposure to 10.0 μg/L DCZ significantly inhibited the contact time between female and male fish, which was mainly achieved by affecting male fish. The transcription of genes involved in the hypothalamus-pituitary-gonad (HPG) axis was significantly changed after treatment with DCZ. Overall, these data show that the endocrine-disrupting effect of DCZ on the zebrafish HPG axis inhibited gamete maturation and disrupted reproductive behavior, reducing fertility.

Evidences for Red Pigment Concentrating Hormone (RPCH) and Beta-Pigment Dispersing Hormone (β-PDH) Inducing Oocyte Meiotic Maturation in the Chinese Mitten Crab, Eriocheir sinensis.

Red pigment concentrating hormone (RPCH) and pigment dispersing hormone (PDH) are crustacean neuropeptides involved in broad physiological processes including body color changes, circadian rhythm, and ovarian growth. In this study, the full-length cDNA of RPCH and PDH were identified from the brain of the Chinese mitten crab Eriocheir sinensis. The deduced RPCH and PDH mature peptides shared identical sequence to the adipokinetic hormone/RPCH peptides family and the β-PDH isoforms and were designated as Es-RPCH and Es-β-PDH, respectively. Es-RPCH and Es-β-PDH transcripts were distributed in the brain and eyestalks. The positive signals of Es-RPCH and Es-β-PDH were localized in the neuronal clusters 6, 8, 9, 10, and 17 of the brain as revealed by in situ hybridization. The expression level of Es-RPCH and Es-β-PDH mRNA in nervous tissues were all significantly increased at vitellogenic stage, and then decreased at the final meiotic maturation stage. The administrated with synthesized Es-RPCH peptide results in germinal vesicles shift toward the plasma membrane in vitellogenic oocyte, and significant decrease of the gonad-somatic index (GSI) and mean oocyte diameter as well as the expression of vitellogenin mRNA at 30 days post injection in vivo. Similar results were also found when injection of the Es-β-PDH peptide. In vitro culture demonstrated that Es-RPCH and Es-β-PDH induced germinal vesicle breakdown of the late vitellogenic oocytes. Comparative ovarian transcriptome analysis indicated that some reproduction/meiosis-related genes such as cdc2 kinase, cyclin B, 5-HT-R and retinoid-X receptor were significantly upregulated in response to Es-RPCH and Es-β-PDH treatments. Taken together, these results provided the evidence for the inductive effect of Es-RPCH and Es-β-PDH on the oocyte meiotic maturation in E. sinensis.

Efficiency of fresh fish and clam meat as a maturation diet in Sebae clownfish, Amphiprion sebae (Bleeker 1853)

The influence of different combinations of fresh fish and clam meat as feed on gonadal development and maturation in Amphiprion sebae was evaluated in a 60-day study. The study used four different combinations of diet viz. control diet (C: commercial feed with 50 % protein (C)), Treatment 1 (T1: fresh fish alone (F)), Treatment 2 (T2: fresh fish in combination with squid meat (FSQ)) and Treatment 3 (T3: fresh fish in combination with clam meat (FCM)). The experiment was conducted in triplicate, with Clown fish (mean weight: 15 g) stocked in tanks of 200 L capacity. The stocked fish were fed on alternate days with the respective assigned diets. On completion of the 60 days study period, maturation of the fish was assessed based on gonado-somatic index (GSI), fecundity and histology. The present study found highest GSI in fish fed with a diet of fresh fish and clam meat on alternate days (0.493 %), followed by fish fed with a diet of fresh fish and squid meat in alternate days (0.349 %) while the lowest GSI was observed in the group fed with the control diet (0.100 %). Average fecundity observed for A. sebae during the present study was 2204±137.4 eggs. Among the different diets, fish fed fresh fish and clam meat (T3) on alternate days had better gonadal development. On 60 th day, the ovary of T3 showed late vitellogenic oocytes with an appearance of yolk vesicles. Thus, it could be concluded that fresh fish in combination with clam meat can be used as maturation diet for marine ornamental fish A. sebae to attain early maturation in captivity.

Exposure to Boscalid Induces Reproductive Toxicity of Zebrafish by Gender-Specific Alterations in Steroidogenesis.

Boscalid is a succinate dehydrogenase inhibitor fungicide and is frequently detected in surface water. Due to the frequent detection of boscalid, we evaluated its impact on the reproduction of adult zebrafish following a 21 d exposure to 0, 0.01, 0.1, and 1.0 mg/L. Following exposure to boscalid, the fertility of female zebrafish and fertilization rate of spawning eggs were reduced in a concentration-dependent manner up to a respective 87% and 20% in the highest concentration. A significant 16% reduction in the percentage of late vitellogenic oocytes was noted in ovaries, and a significant 74% reduction in the percentage of spermatids in testis was also observed after treatment with 1.0 mg/L. 17β-Estradiol (E2) concentrations decreased significantly in females (34% decrease) but significantly increased in males (15% increase) following 1.0 mg/L boscalid treatment. The expression of genes (such as era, er2b, cyp19a, and cyp19b) related to the hypothalamus-pituitary-gonad-liver (HPGL) axis was significantly altered and positively correlated with E2 concentrations in female and male zebrafish (p < 0.05). Molecular docking results revealed that the binding modes between boscalid and target proteins (ER and CYP19) of zebrafish were similar to that of the reference compounds and the target proteins. The binding energies indicate that boscalid may have a weak estrogen-like binding effect or CYP19 inhibition, potentially altering the HPGL axis, thereby reducing E2 concentrations and fecundity in females. In contrast, boscalid caused significant induction of E2 steroidogenesis and subsequent feminization of gonads in males, indicating gender-specific adverse outcome pathways.

Gonadal development and intersex condition of marbled lungfish, Protopterus aethiopicus (Heckel, 1851), in contaminated sites in Lake Victoria, Uganda

The first evidence of the impact of environmental contamination on populations of Protopterus aethiopicus (Heckel, 1851) in terms of body indices, cellular development (histology) and intersex condition in Lake Victoria, Uganda is provided. Specimens were obtained from the more polluted swampy areas receiving wastes from residential and industrial settings (Ggaba, n = 11; Port Bell, n = 10; and Jinja, n = 7), and rural, less polluted areas (Bukakata, n = 3; Kasensero, n = 4; and Bale, n = 2), and gonadosomatic indices, growth condition factor and the morphometric body characteristics were determined. Fish specimens in less polluted sites had better condition and shapes, regardless of sex, compared with those in more polluted sites of the lake. Most lungfish collected had a total length of 45–55 cm. Irrespective of sex of fish and level of pollution at collection sites, samples (n = 26) collected inshore (1 063.42 g ± 109.32 SE) were heavier than those collected (n = 11) offshore (680.09 g ± 108.85 SE), F (1, 35) = 6.288, p = 0.019. Mean values of gonadosomatic indices were significantly higher in less polluted sites, compared with chemically contaminated urban sites (F (5, 31) = 2.783, p = 0.034), suggesting better growth performance in the former. Spermatogenic cell development progressed as spermatogonia, spermatocytes, spermatids and spermatozoa among males. For oogenic cells, development was through chromatin nucleolar, perinucleolar, cortical alveolar, early vitellogenic and late vitellogenic oocytes. Histological examinations revealed group asynchronous gonadal development and intersex condition among P. aethiopicus populations in Lake Victoria.

Role of GnRH and GnIH in paracrine/autocrine control of final oocyte maturation

The control of oocyte growth and its final maturation is multifactorial and involves a number of hypothalamic, hypophyseal, and peripheral hormones. In this study, we investigated the direct actions of the gonadotropin-releasing hormone (GnRH) and the gonadotropin-inhibitory hormone (GnIH), which are expressed in the ovarian follicles, on final oocyte maturation in zebrafish, in vitro. Our study demonstrates the expression of GnRH and GnIH in the ovarian follicles of zebrafish (Danio rerio) at different stages of development and provides information on the direct action of these hormones on final oocyte maturation. Treatment with both GnRH and GnIH peptides stimulated the germinal vesicle breakdown (GVBD) of the late-vitellogenic oocyte. Both the GnRH and GnIH treatments showed no significant change in the caspase-3 activity of pre-vitellogenic and mid-vitellogenic oocytes, while they displayed different responses in the late-vitellogenic follicles. The GnRH treatment increased caspase-3 activity, whereas the GnIH reduced caspase-3 activity in the late-vitellogenic follicles. We also investigated the effects of GnRH and GnIH on the hCG-induced resumption of meiosis and caspase activity in vitro. GnRH and GnIH were found to have a similar effect on the hCG-induced resumption of meiosis, while they showed the opposite effect on caspase-3 activity. Furthermore, we investigated the effects of concomitant treatment of GnRH and GnIH peptides with hCG. The results demonstrated that the presence of both GnRH3 and GnIH are necessary for the normal induction of final oocyte maturation by gonadotropins. The findings support the hypothesis that GnIH and GnRH peptides produced in the ovary are part of a complex multifactorial regulatory system that controls zebrafish final oocyte maturation in paracrine/autocrine manner working in concert with gonadotropin hormones.

Induced maturation and fertilized egg production of the red‐spotted grouper, Epinephelus akaara , using adaptive physiology of photoperiod and water temperature

As a preliminary investigation into the effects of environmental factors on gonadal development using adaptive physiological characteristics, we examined the involvement of photoperiod and water temperature in the ovarian development of the redspotted grouper, Epinephelus akaara. During October 2014 (non-breeding season), the photoperiod and water temperature were adjusted to 12L:12D and 18°C respectively. Every 3 weeks, daylight was increased as follows a 13L:11D and 14L:10D in the photo-thermal treatment group, and the control group was maintained under natural conditions. After 9 weeks, water temperature was increased to 23°C in the photo-thermal treatment group. In photo-thermal treatment group, GSI increased significantly after 9 weeks (1.36 ± 0.19) and 12 weeks (3.31 ± 0.20) compared with the control group. At 12 weeks after photo-thermal treatment, all fishes matured into   ovaries containing late vitellogenic oocytes. The expression of FSH β and LHβ mRNAs also increased significantly. However, in the control group, the ovarian development was maintained at an immature stage. Based on these results, we demonstrate that exposure to long photoperiod and high water temperature can induce the sexual maturation of immature red-spotted grouper during the non-breeding season.

Gonadal recrudescence and annual reproductive hormone pattern of captive female Spotted Scats (Scatophagus argus)

The Spotted Scat (Scatophagus argus), an important euryhaline fish inhabiting mangrove and coastal regions of Indo-Pacific waters, is both an ornamental and food fish in India. Detailed insight into maturation of Spotted Scat when maintained in aquaculture systems, therefore, needs to be elucidated. Lack of information on annual maturation dynamics of female scat collected from their natural habitat and reared in earthen ponds is the basis of this study. Oocytes were classified into five developmental stages: pre-vitellogenic, vitellogenic, late-vitellogenic, ripe, and follicular atresia. Ovarian maturity stages were subsequently categorized as immature (Stage 1), vitellogenesis (Stage 2), maturing (Stage 3), mature (Stage 4), and spent (Stage 5). In oocytes in primary, secondary and tertiary yolk stages, there are greater concentrations of E2 in vitellogenic females between March and June. Significant increases of E2, T, and 17-OHP paralleled the increase of diameter of late–vitellogenic oocytes in maturing females during July. The completion of vitellogenesis and initiation of germinal vesicle migration in the cytoplasm were evident in mature females (Stage 4) with a decreasing trend of sex steroids in and subsequent to the month of August. There were 50 % of oocytes in the final oocyte maturation stage (FOM) (490–620 μm) until completion of Stage 4 in September. The results of this study indicate there is complete ovarian maturation in female scats captured in their natural habitat and maintained in an earthen pond, which may be important information for hatchery management for induction of spawning of Spotted Scat in aquaculture systems.

Seasonal and spatial changes in sex hormone levels and oocyte development of bonefish (Albula vulpes)

Bonefish (Albula vulpes) support an economically important fishery, yet little is known regarding the reproductive biology of this species. Blood and oocyte samples were collected from wild female bonefish (Albula vulpes) during (February and April, 2017) and outside (September, 2017) the spawning season in Grand Bahama Island, The Bahamas. Fish reproductive state was evaluated using histological analysis of the oocytes and determination of sex hormone levels of 17β-estradiol and testosterone in the plasma. The presence of three different cohorts of oocytes in bonefish females suggests group-synchronous ovarian development. Levels of 17β-estradiol were low in individuals sampled outside of the spawning season relative to fish sampled during spawning months. Testosterone levels did not change as female bonefish entered the spawning season. Within the spawning season, bonefish are commonly found along shallow water flats, or in pre-spawn aggregations (PSA). The diameters of late vitellogenic oocytes collected from PSA fish were significantly larger than those from the flats fish. Levels of 17β-estradiol did not differ between PSA and flats fish; however, testosterone levels were significantly higher in fish from the PSA. These results indicate that as bonefish are transitioning to the PSA from flats habitats, vitellogenesis is still occurring. However, when and where final maturation commences in reproductively active bonefish remains unclear.

Life history traits of rare Antarctic dragonfishes from the Weddell Sea

AbstractThe life history traits of bathydraconids, deep-living fishes distributed all around the Antarctic continent, are poorly known. In particular, very few data are available on the relatively rare genera Akarotaxis and Bathydraco. With the aim to fill this gap, sagittal otoliths and gonads were analysed to assess individual age and reproductive features of Akarotaxis nudiceps (Waite, 1916), Bathydraco macrolepis Boulenger 1907 and Bathydraco marri Norman, 1938 collected in the Weddell Sea. Based on the annual growth increment patterns, age estimates ranged between 6–11, 5–11 and 8–11 years for A. nudiceps, B. macrolepis and B. marri, respectively. Most of the gametogenetic processes could be described based on gonad histology for both sexes. Females shared the reproductive features commonly reported in notothenioids, such as group-synchronous ovary development and prolonged gametogenesis. Total fecundity estimates were comparable between the two species of Bathydraco (1500–2500 eggs/female), whereas that of Akarotaxis was one order of magnitude smaller (200–250 eggs/female). Consistently, the mean size of late vitellogenic oocytes showed an opposite trend, being 1.6–1.8 mm in Bathydraco and 2.2 mm in Akarotaxis.

Modulation of reproductive exhaustion usingUlva clathratain Pacific white shrimpLitopenaeus vannamei(Boone, 1931) broodstock during commercial maturation

Ulva clathrata meal (2%) was supplemented in a fresh maturation diet for Litopenaeus vannamei broodstock in a commercial larval facility and its effects on reproductive performance, histology and histochemistry of gonad, and biochemical composition of gonad, hepatopancreas, and muscle were analysed. Females that were given Ulva in the diet had reduced mortality compared to controls, with no differences in males. Females fed Ulva also had bigger oocytes but only those in late vitellogenesis (+7%, p < 0.01) and postvitellogenesis (+15%, p < 0.01); they also had a higher proportion of late vitellogenic oocytes in maturation stage II, and a bigger area occupied by cortical rods. No significant differences were found for the proportion of previtellogenic or early vitellogenic oocytes per maturation stage or as a result of Ulva. Females fed Ulva had higher levels of lipids in ovary (+35%, p < 0.05), with no significant differences in biochemical reserves in hepatopancreas or muscle. The total number of eggs (+5%, p < 0.01), nauplii per spawn (+18%, p < 0.01), and hatching rate (+13%, p < 0.01) during the productive cycle were higher for Ulva fed shrimp. Individual follow-up of marked females during the productive cycle showed a decreased reproductive exhaustion in females fed Ulva over consecutive spawns. Apparently, U. clathrata stimulates advanced vitellogenesis by improving lipid accumulation in gonads, and this in turn increases reproductive performance: inclusion of this algae in shrimp diet could be used to decrease reproductive exhaustion during production.

Gonadal histology and gametogenesis of the Antarctic limpet Nacella concinna (Patellogastropoda, Nacellidae) collected at Potter Cove, 25 de Mayo (King George) Island, during austral summer

The limpet Nacella concinna is one of the most widely distributed gastropods along the Antarctic Peninsula. This species has been a useful tool in ecological and physiological studies for understanding Antarctic trophic interactions. Although the reproduction of limpets has been thoroughly studied, very little is known about gametogenesis in the genus Nacella. The purpose of this study is to describe the gonadal morphology and gametogenesis in N. concinna observed by light microscopy and to determine its chromosome complement. All the limpets were sexually mature at the time of sampling. Oocytes were separated by trabeculae with abundant glycogen reserves. There was a predominance of late vitellogenic oocytes. Many previtellogenic oocytes were pyriform in shape. Oogonia were clustered near the ovary wall or the trabeculae. Only two meiotic stages were found: metaphase I and anaphase I, both of which showed a regular arrangement of chromosomes. The oviduct contained mature oocytes surrounded by sperm. Testicular tubules were filled with spermatozoa. The elongated head of the spermatozoon resembles that of other Nacellidae members. One of the bivalents is heteropycnotic. The haploid complement is n = 4 and the sex determination system is XO/XX. Although N. concinna has been commonly characterized as a broadcast-spawner, its unique spawning behavior, the presence of oocytes at anaphase I and spermatozoa within the oviduct suggests internal fertilization.

Dynamics of oogenesis in ghost shrimp Callichirus major (Crustacea: Axiidea): a morphofunctional and histochemical study

Callichirus major, popularly known as ghost shrimp, is a species of great importance in the fishing industry, because of its use as live bait. This study aimed to describe the different stages of the developing ovaries in C. major. Shrimps were collected along the Corujão beach, Piuma, Brazil (20°50'41.6“S 40°44'15.7“W), and the gonads were dissected for histological and histochemical analysis. The ovary consists of two elongated filaments covered by a connective tissue that divides the organ into lobules, where somatic and germ cells are found. It was possible to classify five types of germ cells: Oogonia (Oog), previtellogenic oocyte (Oc1), early vitellogenic oocyte (Oc2), late vitellogenic oocyte (Oc3) and mature oocyte (Oc4) based on their vitellogenic stage, cytoplasmic, nuclear and morphometric characteristics. The histochemical analysis demonstrated an intense reaction for proteins and polysaccharides in peripheral cytoplasm of Oc3 comparing to others cell types. According to size, volume, color intensity and distribution of oocyte types the gonads were classified into: immature, developing, developed and spent, being in females at this last stage, observed empty follicles and oocytes in reabsorption process. During oogenesis was observed a gradual increase in cytoplasmic acidophilia due to accumulation of yolk granules and the intense histochemical reaction in periphery of Oc3, which indicate the beginning of an extravitellogenic source of nutrients. Based on the microscopic analysis of the vitellogenesis, shrimp C. major showed the initial short phase of oocyte growth following with a fast vitellogenic cycle.

Dynamics of ovarian maturation throughout the reproductive cycle of the Neotropical cichlid fishCichlasomadimerus(Teleostei, Cichliformes)

In this study, we analyzed gene expression profiles, plasma steroids concentrations, and gonadal morphology throughout the reproductive cycle of female Cichlasoma dimerus (Heckel, 1840), a monogamous cichlid fish exhibiting social hierarchies. Fish were analyzed at six phases encompassing their annual cycle, namely resting (during the nonreproductive period), prespawning, 30 h post spawning, 4 days post spawning, 10 days post spawning, and subordinate (during the reproductive period). The histological and histomorphometric analysis showed that C. dimerus exhibits asynchronous ovarian development. Similar to resting females, subordinate females showed low gonadosomatic index, reduced expression levels of vitellogenin (vtgAb), zona pellucida (zpB), gonadal aromatase (cyp19a1A), and low concentrations of plasma sex steroids, thus indicating that social intimidation by dominant conspecifics elicited reproductive arrest. In reproductively active females, a direct positive correlation between plasma estradiol, vtgAb expression, percentage of late vitellogenic oocytes, and gonadosomatic index was observed. These parameters were maximal at the prespawning phase, decreased at 30 h post spawning and 4 days post spawning, and then reached a peak at 10 days post spawning. Our results indicate that female C. dimerus become spawning capable after 10 days post spawning, coincidently with the shortest time interval between successive spawns recorded in captivity.

Erratum to: Histomorphological study of ovarian atresia over the reproductive cycle of Octopus vulgaris from Galician waters (NW Spain)

Atresia has been poorly examined in cephalopods. We here provide a histological description of this process along the whole ovary development for Octopus vulgaris. Additionally, we related its occurrence to morphometric parameters, and its seasonal cycle was further analysed. Atresia occurred all year round in immature and mature females and in previtellogenic and vitellogenic oocytes. However, more mature females were more prone of being atretic. This occurred mainly in spring when females had atretic previtellogenic oocytes in mature macrostages. By contrast, vitellogenic atresia occurred mainly from spawning to post-spawning females. Furthermore, two types of phagocytic cells were identified as responsible for the reabsorption during atresia. The phagocytic follicle cells only occurred in yolk-bearing oocytes; and within the two haemocyte populations only the smaller ones seemed to be involved in engulfing atretic oocytes. Additionally, advanced atresia in post-spawning females showed yellow–brown bodies as a possible result of follicle cell apoptosis and highlighting the end of the reproductive cycle. Given the pattern of atresia, the reproductive strategy of this species is based on an asynchronic ovary development and a synchronous ovulation during spawning. We further suggest that potential fecundity for this species should be measured on late vitellogenic oocytes in pre-spawning females.

Comparative Study of Reproductive Development in Wild and Captive-Reared Greater Amberjack Seriola dumerili (Risso, 1810)

The greater amberjack Seriola dumerili is a large teleost fish with rapid growth and excellent flesh quality, whose domestication represents an ambitious challenge for aquaculture. The occurrence of reproductive dysfunctions in greater amberjack reared in captivity was investigated by comparing reproductive development of wild and captive-reared individuals. Wild and captive-reared breeders were sampled in the Mediterranean Sea during three different phases of the reproductive cycle: early gametogenesis (EARLY, late April-early May), advanced gametogenesis (ADVANCED, late May-early June) and spawning (SPAWNING, late June-July). Fish reproductive state was evaluated using the gonado-somatic index (GSI), histological analysis of the gonads and determination of sex steroid levels in the plasma, and correlated with leptin expression in the liver and gonad biochemical composition. The GSI and sex steroid levels were lower in captive-reared than in wild fish. During the ADVANCED period, when the wild greater amberjack breeders were already in spawning condition, ovaries of captive-reared breeders showed extensive atresia of late vitellogenic oocytes and spermatogenic activity ceased in the testes of half of the examined males. During the SPAWNING period, all captive-reared fish had regressed gonads, while wild breeders still displayed reproductive activity. Liver leptin expression and gonad proximate composition of wild and captive greater amberjack were similar. However, the gonads of captive-reared fish showed different total polar lipid contents, as well as specific lipid classes and fatty acid profiles with respect to wild individuals. This study underlines the need for an improvement in rearing technology for this species, which should include minimum handling during the reproductive season and the formulation of a specific diet to overcome the observed gonadal decrements of phospholipids, DHA (22:6n-3) and ARA (20:4n-6), compared to wild breeders.

Impact of methoprene on oogenesis of the freshwater crab Travancoriana schirnerae Bott, 1969 (Decapoda: Gecarcinucidae)

The current study investigated the impact of methoprene during different phases of oogenesis in the freshwater crab Travancoriana schirnerae Bott, 1969 (Decapoda: Gecarcinucidae), a non-target organism abundant in the wetlands of Wayanad, Kerala, India. Sublethal doses of methoprene impaired ovarian growth as evidenced by reduction in gonadosomatic values, fall in mean oocyte diameter and histopathological changes in all the phases of oogenesis. A significant drop in the proportion of mature oocytes in the experimental crabs were noticed, i.e. methoprene treatment delayed the growth of avitellogenic oocytes to previtellogenic and previtellogenic to early, middle or late vitellogenic stages. Reduction in proliferation of oogonia in the germinal zone and ruptured oolemma in chromatin nucleolus and perinuclear stage oocytes was persistent. Histopathological changes in the primary vitellogenic oocytes include karyoplasmic clumping, perinuclear space atresia, shrinkage and vacuolation of ooplasm, reduction in size of yolk globules and vacuolated globules and degeneration of follicle epithelium. Methoprene negatively affected yolk platelet formation as evidenced by the irregularly fused and distorted yolk platelets of late vitellogenic oocytes. The observed cellular deformities possibly suggest the direct effects of methoprene on the oocytes through general metabolism and growth or through hormones controlling ovarian growth.

REPRODUCTIVE CYCLE, GAMETOGENESIS AND EMBRYONIC DEVELOPMENT OF NITIA TERETIUSCULA (BIVALIVA: UNIONIDAE), FROM THE RIVER NILE, AT SOHAG GOVERNORATE, EGYPT

The present study dealt with the description of the reproductive and gametogenic cycles and the embryonic development of the freshwater mussel Nitia teretiuscula from the River Nile. Macro and micro-anatomy showed that the present species is dioceous and gonadosomatic indices showed that the species is semiannual and had two gonadal growth periods, a short period of gonadal growth from January to March and a long period from April to August. Visceral indices revealed a reciprocal relationship with the gonadosomatic indices of both the two sexes. The recorded sex ratio of females to males was (1.5: 1). The oogenesis displayed five developmental stages; oogonia, previtellogenic oocytes, vitellogenic oocytes, late vitellogenic oocytes and mature ova. Also, spermatogenesis illustrated five developmental stages: spermatogonia, primary spermatocytes, and secondary spermatocytes, spermatids; which clustered to form sperm morula and finally metamorphosed to spermatozoa. Within the gills of females (marsupia), brooding of embryos was occurred till the formation of glochidia larvae. The unfertilized eggs were released from the gonads with distinct germinal vesicle. The fertilized eggs had two polar bodies and a fertilization cone. Successive cleavages were observed. Spiral cleavage, non-ciliated blastula and D-shaped larvae were recorded.