Stages Of Gonadal Development Research Articles

Age and reproduction of the southern king croaker Menticirrhus americanus in subtropical South Atlantic environments

Menticirrhus americanus were sampled (n = 393) from two beaches (P1 is an estuarine beach near the mouth of the Paranaguá Estuarine Complex, and P2 is a beach adjacent to the Paranaguá Estuarine Complex) in the subtropical region of the western South Atlantic waters between August 2015 and June 2016. This study aimed to identify the spawning season and the age structure for M. americanus using two sampling methods. For sampling at the P1 beach, seine, line, and pole were used, while samples from the P2 beach were obtained from the artisanal fishers. Females were numerically dominant in all sampling months at both sites except for February when the males became dominant. The species exhibited a protected reproductive season with multiple spawning peaks between August and December. Males and females were captured at all gonadal development stages and ages between 1 and 6 from both sites. At first maturity, the length of the females was 16.3 cm, and the mean age at first maturity was 1.3 years. Individuals aged between 1 and 3 years were dominant (68%). The results suggested that young and adults of the M. americanus use the same habitats throughout their ontogeny.

Global expression response of genes in sex-undifferentiated Nile tilapia gonads after exposure to trace letrozole

The aromatase inhibitor letrozole can be found in rivers, effluents, and even drinking water. Studies have demonstrated that letrozole affects various metabolic pathways and may cause reproductive toxicity, especially in fish exposed during development. However, studies on the effect of a low concentration of letrozole at the whole-gonad transcriptomic level in the early stage of fish sexual development have not been investigated. The aim of our study was to explore the potential effects of a low concentration of letrozole on the gonad transcriptome of Nile tilapia at an early stage of sexual development. In this study, 9 dpf (days postfertilization) Nile tilapia were exposed to trace letrozole for 12 days. Letrozole exposure from 9 dpf to 21 dpf persistently altered phenotypic sex development and induced the male-biased sex ratio. The transcriptome results showed that 1173 differentially expressed genes (DEGs) were present in the female control vs 1.5 μg/L letrozole-treated female comparison group and that 1576 DEGs were present in the 1.5 μg/L letrozole-treated female vs male control comparison group. Differentially expressed gene enrichment analysis revealed several crucial pathways, including the drug metabolism-cytochrome P450 pathway, the ErbB-PI3K/Akt/mTOR pathway, and the calcium signalling pathway. Further analysis of these identified DEGs indicated that some key genes correlated with metabolism and epigenetic regulation were significantly affected by letrozole, such as UDP-glucuronosyltransferase (Ugt), glutathione S-transferase omega-1 (Gsto1), lysine-specific demethylase 6bb (Kdm6bb, original name is Kdm6a), jumonji and AT-rich interaction domain containing 2 (Jarid2b, original name is Jarid2), growth arrest and DNA damage inducible gamma (Gadd45g), and chromobox protein 7 (Cbx7). The qRT-PCR validation results for twelve DEGs showed that the Pearson’s correlation of the log10fold change values between the qPCR and RNA-Seq results was 0.90, indicating the accuracy and reliability of the RNA-Seq results. Our study is the first to report the effect of letrozole on the transcriptome of gonads from fish during early-stage sexual development. These findings will be useful for understanding the toxic effects and molecular mechanisms of letrozole exposure at the early stage of gonad development on the sexual development of aquatic organisms.

Reproductive Biology of Land Crabs (Gecarcoidea lalandii) in Ly Son Island, Quang Ngai Province – Vietnam

The reproductive biology of the land crab Gecarcoidea lalandii was documented for the Ly Son Island, Quang Ngai Province, Vietnam. Approximately 30 crabs, collected every month in the 12-month period from August 2019 to July 2020, were analyzed gonadal development stages, sex ratio, spawning season, fecundity and size at first sexual maturity. Results showed that number of male and female crab in nature was not significantly different. Gonadal of the crab passed through five stages of maturation. The crab spawns continuously during the spawning season. In nature, the crab can mature whole year-round with a higher proportion from January to August and the peak maturation from June to July. The spawning season is of this species is only on the raining period from June to July. Length at first sexual maturity of the crab was 53.91 mm of carapace width for female and 50.39 mm male crab. The absolute fecundity varied in 473,000-820,000 eggs ind-1 and highly related to body weight. The current findings provide the scientific foundation for fishery resource management and artificial breeding of the land crab in Ly Son.

Reproductive biology of Indian halibut, Psettodes erumei from the northern Persian Gulf and Oman Sea (Teleoststei: Psettodidae)

The reproductive biology of Indian halibut, Psettodes erumei , a commercially valuable flatfish species, in the northern Persian Gulf and Oman Sea was studied. A total of 433 specimens were collected monthly from October 2016 to November 2017, and their length, weight, sex, gonad and liver weight, and maturity status were recorded. Monthly variations in Gonado-somatic index showed two obvious peaks in the spawning period in both sexes. Observations from the seasonal maturation curve, the frequency distribution of the female gonadal development stages and the condition factor confirmed recent findings that the spawning periods have two peaks, a higher peak in April-May (spring) and a lower peak in October (autumn). The size at first maturity of females was estimated to be 38.20 cm in total length. The absolute fecundity ranged from 18072 to 332171 eggs while the relative fecundity ranged from 22 to 161 eggs/g. Absolute fecundity was positively correlated with body related parameters (total length/weight) and with gonad weight. Combined, the information provided in this study could be useful for resource managers to set seasonal closure during peak spawning periods and implement minimum size limits above the size at first maturity to let the fish spawn at least once before capture.

Similarities between bovine and human germline development revealed by single-cell RNA sequencing.

The germ cell lineage ensures the creation of new individuals and perpetuates the genetic information across generations. Primordial germ cells are pioneers of gametes and exist transiently during development until they differentiate into oogonia in females, or spermatogonia in males. Little is known about the molecular characteristics of primordial germ cells in cattle. By performing single-cell RNA-sequencing, quantitative real-time PCR, and immunofluorescence analyses of fetal gonads between 40 and 90 days of fetal age, we evaluated the molecular signatures of bovine germ cells at the initial stages of gonadal development. Our results indicate that at 50 days of fetal age, bovine primordial germ cells were in the early stages of development, expressing genes of early primordial germ cells, including transcriptional regulators of human germline specification (e.g. SOX17, TFAP2C, and PRDM1). Bovine and human primordial germ cells also share expression of KIT, EPCAM, ITGA6, and PDPN genes coding for membrane-bound proteins, and an asynchronous pattern of differentiation. Additionally, the expression of members of Notch, Nodal/Activin, and BMP signaling cascades in the bovine fetal ovary, suggests that these pathways are involved in the interaction between germ cells and their niche. Results of this study provide insights into the mechanisms involved in the development of bovine primordial germ cells and put in evidence similarities between the bovine and human germline.

Reproductive performance of Macrobrachium acanthurus (Crustacea, Palaemonidae) females subjected to unilateral eyestalk ablation

AbstractThe present study investigated the effects of eyestalk ablation on the reproductive performance of females from the native caridean shrimp Macrobrachium acanthurus. The reproduction parameters fertility, fecundity, egg volume, larvae size, loss of embryos and number of females with viable eggs/larvae were evaluated. Females presenting carapace length of 12–15 mm and spent stage of gonadal development were divided into two groups, one undergoing unilateral eyestalk ablation and the other remaining intact. The specimens were kept in aquarium until ovarian maturation, then brought together with males for mating (proportion of two females for each male). Fecundity and fertility were greater in intact females (1,741 eggs and 1,045 larvae) than in ablated ones (1,373 eggs and 741 larvae). Ablation also reduced the percentage of females with viable eggs (68% intact versus 49% ablated) and larvae (82% intact versus 64% ablated), besides increasing the loss of embryos. Egg volume and shape (ellipsoid) and larvae size were similar, as was the duration of embryonic development. The results of this study suggest that, although ablated females exhibit a high rate of survival, their reproductive performance is reduced; therefore, the ablation technique is not recommended in M. acanthurus farming, so as to protect the animals from physiological stress.

Broodstock conditioning, spawning, embryonic and early larval development of a novel baby clam species for aquaculture in the southeast Pacific: Tawera elliptica (Lamarck, 1818)

Tawera elliptica is a small size (baby) clam with an export fishery in southern Chile. The species is dioecious with external fertilization and without sexual dimorphism. The aim of this work was to optimize broodstock conditioning, induce spawning and describe embryonic development until the early larval stage in a hatchery. Broodstock were conditioned at 3 treatments (with/without sand; water circulation) for 48 days. The clams were fed with a mixed diet of macroalgae, with a daily ration of 250,000 cells/ml. Broodstock response was quantified using condition index and gonad development stages (histological techniques). For spawning induction, physical and biological methods were tested. The best response was achieved in males with physical induction. Histological analysis showed that the water circulation system treatment exhibited the highest percentage of maximum maturity. A fertilization ratio of 500:1 sperm:oocyte was used. The incubation was carried out in 3-L containers with filtered seawater at 10.7 ± 0.9°C without aeration. Observations, measurements and the duration of each embryonic and larval stage were recorded. The oocyte has a prominent gelatinous layer (= jelly coat) that disappears between the gastrula and trochophore stages. The status of the D-larval stage was reached at 107 h post fertilization with a mean valve length of 91.4 ± 8.9 µm. This is the first record of the complete embryonic development of this baby clam until the early larval stage and the conditioning in a water circulation system for 48 days are suitable for the species.

Providing recombinant gonadotropin-based therapies that induce oogenesis from previtellogenic oocytes to produce viable larvae in a teleost, the flathead grey mullet (Mugil cephalus)

Under intensive captive conditions, wild-caught flathead grey mullet (Mugil cephalus) females remained arrested in previtellogenic stages of gonadal development and no sperm could be obtained from males. With the aim to induce oogenesis from previtellogenesis to oocyte maturation, induce the release of sperm and obtain fertilized eggs, female and male flathead grey mullet were treated with Mugil cephalus single-chain recombinant gonadotropins (rGths), follicle-stimulating (rFsh) and luteinizing (rLh) hormones. In Experiment 1, fish were treated with a weekly dose of rFsh (15 μg kg−1), which in females significantly (P < 0.001) increased plasma concentration of 17β-estradiol and induced vitellogenic oocyte growth up to a maximum mean diameter of 425 ± 19 μm after 9 weeks of treatment. In Experiment 2, fish were treated with weekly injections of both rFsh and rLh at different doses (from 2.5 to 12 μg kg−1). Oocyte diameter reached 609 ± 5 μm, from which final oocyte maturation and ovulation was induced with 30 μg kg−1 of rLh and 40 mg kg−1 of progesterone. Good quality sperm (> 75% motile spermatozoa) was obtained from males in both experiments, and in Exp. 2 the addition of rLh induced the production of higher quantities of sperm that were used to fertilise the eggs. Although fertilisation was low (0.4%), these fertilized eggs with embryo development produced viable larvae (71% hatching). In comparison, control females remained arrested at previtellogenesis and control males did not produce sperm. The study demonstrated that both rGths are effective to induce the process of oogenesis in female flathead grey mullet and to obtain flowing sperm from males, adding more data to confirm the roles of the Gths in teleost gametogenesis. This is the first report, in a teleost species, of the use of rGths (rFsh and rLh) to induce oogenesis from previtellogenesis through to maturation to obtain eggs and larvae. This advance provides the bases for the development of therapies for the use in the aquaculture of teleost of commercial interest or the conservation of endangered species.

Gonadal development, reproductive investment and fecundity of Aegla castro Schimitt, 1942 (Crustacea, Anomura)

ABSTRACT Aegla castro, is an endemic anomuran crab from Brazil found in headwater streams of the Atlantic Forest on the Paranapanema River basin. This study aims to evaluate the gonadal maturity of A. castro based on macroscopic and microscopic analyses. Crabs were collected in Mauá da Serra (23º57’ S; 51º06ʹ W), Paraná, Brazil in the winter and spring of 2015, and summer, autumn, and spring of 2016. Individuals had their gonads analysed and categorized into stages of development. Stage1, ovaries are macroscopically undetectable through abdominal transparency, while ovaries of stages 2 and 3 could be detected through abdominal transparency and have characteristic colour and length in relation to the abdominal somites. Ovaries have pre-vitellogenic and vitellogenic oocytes in all stages of development, with germ cells and structural epithelium characteristic of these gonadal maturation phases. Spermatogenesis in males begins in spring, with the production of spermatozoa in autumn and spermiation in winter. Aegla castro has seasonal reproduction. The macroscopic stages of gonadal development correspond to the histological gonadal maturation, indicating that the macroscopic observation of the gonads of live animals is feasible in studies of the reproductive cycle of aeglids.

Features of Changes in the Functional State of Sturgeon during Maturation in Closed Water-Supply Installations

The dynamics of physiological and biochemical parameters of blood and urine in the process of gonad maturation in females of the sterlet × beluga hybrid (Acipenser ruthenus L., 1758 × Huso huso L., 1758) grown using CWSI technology is studied. It is shown that, when this technology is applied, features in functional changes that accompany the gonadogenesis of female hybrids appear, distinguishing them from those of fish from natural populations. At the same time, the direction of the generative exchange aimed at the formation of gametes is generally the same as in females from natural populations. However, the evidence of this process, reflecting its intensity at different stages of gonad development, is not as distinct as in females migrating to spawn. Possible reasons for high levels of the studied physiological and biochemical parameters in blood of females of the hybrid after the end of their artificial wintering are discussed.

Oocyte analysis of species Arca noae Linnaeus, 1758 (Mollusca: Bivalvia) from Adriatic Sea

Noah’s ark shellfish is a commercially important species in the Adriatic Sea, but its populations are overexploited. The objective of this study was to complete the information on reproduction for potential commercial breeding. Previous attempts at ark cultivation resulted in high post-transfer mortality due to mechanical stress from individuals’ detachment from the natural environment. A different approach involving the culture of broodstock for aquaculture operations should be considered. Accurate prediction of spawning events and comparison of the main spawning season and peak in several populations could help to identify a favorable location and period for the collection of hatched gametes and transfer to growing sites. Thus, females of two distinct populations from the Middle Adriatic Sea were investigated. The range of oocyte size at each gonadal developmental stage, the monthly distribution of oocyte frequency and the variation in the monthly mean value of oocyte diameter during 2013 and 2014 were determined. Gametogenesis was not fully synchronous between localities. The period of spawning in Pasman Channel lasts longer and new gametes develop faster. Based on the results we could estimate the periods of gamete release in the studied sites, which may indicate a favorable location and period for the collection of hatched gametes for aquaculture purposes.

Population structure and reproduction of Steindachneridion melanodermatum (Siluriformes: Pimelodidae), a large catfish endemic to Neotropical ecoregion

The population structure and reproductive biology of the surubim of Iguaçu, Steindachneridion melanodermatum, a large endemic and endangered catfish from Iguaçu River basin, were evaluated. In total, 182 specimens of this species were sampled from September 2010 to December 2016 in the Lower Iguaçu River, including some tributaries. The determination of the cycle and reproductive period was undertaken by assessing the mean variation in the values of the gonadosomatic index (GSI) of females and males, as well as by the frequency distribution of the stages of gonadal development on the basis of macroscopic and microscopic analyses. The total length and bodyweight ranged from 21 to 102cm and from 82.8 to 15670g respectively. The reproductive period of this species was from June to September (winter and early spring), and may extend until November, with GSI peaking in August for males and September for females. The size at first maturation (L50) corresponded to 39.5cm for females and 43.9cm for males. Spawning in this species was associated with lower water temperatures, and high discharge and dissolved oxygen concentration. Our findings are crucial in assisting the development of effective measures and specific criteria for the conservation of this endangered species.

Reproductive Strategy of Dosinia ponderosa (Gray, 1838) (Veneridae) in Puerto Libertad, Sonora, Mexico

The reproductive strategy of Dosinia ponderosa at a site of the eastern coast of the Gulf of California, Puerto Libertad, Sonora is reported. Samples of visceral mass were taken from 30 clams that were collected monthly from March 2015 to March 2016, and the length and weight of the tissue without shell of each organism were recorded. Through histological analysis, the gonadal index were calculated, and the reproductive stages of the ponderous dosinia were determined. Six oocyte substages and five gonadal development stages for females and five for males are described. The sex ratio was 1:1, and no undifferentiated specimens were found. The sexual maturity phase was observed throughout the year, with two reproductive peaks in June–July and October–November. No correlation was observed between the reproductive activity and temperature or primary productivity.

Regulation of mucosal lectins in the oyster Crassostrea virginica in response to food availability and environmental factors

ABSTRACT Lectins are a large and diverse group of sugar-binding proteins involved in nonself recognition and cell-to-cell interactions. Suspension-feeding bivalves, such as the oyster Crassostrea virginica, are capable of using these molecules to bind cell surface carbohydrates of food particles, allowing particle capture and selection. The aim of this project was to assess whether the expression of mucosal lectins in C. virginica is constant or changes with the season, and to determine whether lectin expression is linked to environmental parameters and/or internal biological factors (gametogenesis). A total of 130 oysters were placed in submerged cages at a tidal estuary and monitored for changes in lectin gene expression over a 1-year period. In parallel, environmental parameters prevailing at the field site, including seawater physicochemical characteristics (temperature, salinity and dissolved oxygen), particulate organic matter and chlorophyll contents, were also monitored. Throughout the study, oysters were dissected and the gills were collected and used for the assessment of the expression of three different lectin genes (CvML, CvML3914 and CvML3912). Remaining tissues were processed for histology and the classification of the gonad development stage. Results showed that when food is abundant, such as during the spring bloom, lectin gene expressions are low, and inversely lectin levels increase with lower food levels. These findings suggest that oysters increase lectin expression to enhance the capture and ingestion of scarce food, while during spring, enough food is already being ingested and lectins are not needed. Furthermore, results showed that as the energy demands of oysters increase (gonad maturation), lectin gene expressions also increase to enhance selective ingestion of nutritious food particles. This study, therefore, demonstrates the seasonality of lectin gene expression in C. virginica, and suggests that lectin regulation is related to the reproduction process and abundance of high-quality food.

Equilibrium reproductive strategy of the peacock bass Cichla kelberi facilitates invasion into a Neotropical reservoir.

The reproductive strategy of the non-native predator cichlid Cichla kelberi was determined to explain its success after more than 60 years of being introduced into an isolated reservoir in southeastern Brazil. This was one of the first-known translocations of the genus Cichla out of its natural range. Macro- and microscopy characteristics of the gonadal development stages and the maturation phases, along with the reproductive features (size at first maturation size, gonado-somatic index and sex ratio), were described. It was hypothesized that the stable conditions of the reservoir, with low connectivity, weakly defined spatial gradient and slight seasonal changes in environmental variables, favour the equilibrium strategy that enables predators to have high offspring survivorship because of great parental investment in individual progeny. Sex ratio was well balanced, with males and females reaching first maturity between 30.0 and 28.6 cm total length (LT ), respectively. The stages of oocyte (primary and secondary growth, vitellogenic and atresia) and spermatocyte (spermatogonia, spermatocytes, spermatids and spermatozoa) development were identified. Five phases of gonadal development (immature, developing, spawning capable, regressing and regenerating) were described for both sexes. A long reproductive season was found, with spawning peaks in August/September and, to a lesser extent, in April/May. Parental care and spawns in parcels (batch spawns) corroborated the raised equilibrium strategy that was effective in this isolated reservoir. This species developed reproductive mechanisms that fit to different environmental conditions, with multiple spawning being associated with lentic environments and asynchronous development of oocytes, which are released over long periods. The reproductive plasticity in reservoirs may be one of the main factors inherent to the successful of colonization and establishment of the peacock bass in the environments in which they were introduced.

Comparative transcriptome analysis of three gonadal development stages reveals potential genes involved in gametogenesis of the fluted giant clam (Tridacna squamosa)

BackgroundGonad development and differentiation is an essential function for all sexually reproducing species, and many aspects of these developmental processes are highly conserved among the metazoa. However, the mechanisms underlying gonad development and gametogenesis remain unclear in Tridacna squamosa, a large-size bivalve of great ecological value. They are protandrous simultaneous hermaphrodites, with the male gonad maturing first, eventually followed by the female gonads. In this study, nine gonad libraries representing resting, male and hermaphrodite stages in T. squamosa were performed to identify the molecular mechanisms.ResultsSixteen thousand four hundred ninety-one unigenes were annotated in the NCBI non-redundant protein database. Among the annotated unigenes, 5091 and 7328 unigenes were assigned to Gene Ontology categories and the Kyoto Encyclopedia of Genes and Genomes (KEGG) Pathway database, respectively. A total of 4763 differentially expressed genes (DEGs) were identified by comparing male to resting gonads, consisting of 3499 which were comparatively upregulated in males and 1264 which were downregulated in males. Six hundred-ninteen DEGs between male and hermaphroditic gonads were identified, with 518 DEGs more strongly expressed in hermaphrodites and 101 more strongly expressed in males. GO (Gene Ontology) and KEGG pathway analyses revealed that various biological functions and processes, including functions related to the endocrine system, oocyte meiosis, carbon metabolism, and the cell cycle, were involved in regulating gonadal development and gametogenesis in T. squamosa. Testis-specific serine/threonine kinases 1 (TSSK1), TSSK4, TSSK5, Doublesex- and mab-3-related transcription factor 1 (DMRT1), SOX, Sperm surface protein 17 (SP17) and other genes were involved in male gonadal development in Tridacna squamosal. Both spermatogenesis- (TSSK4, spermatogenesis-associated protein 17, spermatogenesis-associated protein 8, sperm motility kinase X, SP17) and oogenesis-related genes (zona pellucida protein, Forkhead Box L2, Vitellogenin, Vitellogenin receptor, 5-hydroxytryptamine, 5-hydroxytryptamine receptor) were simultaneously highly expressed in the hermaphroditic gonad to maintain the hermaphroditism of T. squamosa.ConclusionAll these results from our study will facilitate better understanding of the molecular mechanisms underlying giant clam gonad development and gametogenesis, which can provided a base on obtaining excellent gametes during the seed production process for giant clams.

The effects of stocking density on physiological traits in Holothuria forskali broodstock

The high demand of sea cucumbers in international markets, mostly based in Asia, has left a deep impact on the natural stock of many species, leading to an investment in aquaculture techniques in order to mitigate these impacts. This study aimed to determine the effects of stock density in rearing broodstock of Holothuria (Panningoturia) forskali Delle Chiaje, 1823, a common species in the Mediterranean Sea and eastern Atlantic with commercial value. To do so, two different density treatments were selected: 1 kg/m2 and 2 kg/m2. The trial took place over five months and individuals were fed a mixture of frozen microalgae (Tetraselmis sp. and Phaeodactylum tricornutum). At the end of the trial, the effects of stock density on the individuals’ condition were assessed by analysing different variables, namely their fresh and gutted weight, evisceration and mortality rates, gonadosomatic index and oocyte size and even biochemical content, such as protein and lipid content in muscle bands. No significant differences were found between density treatments regarding any of the parameters assessed, aside from mean oocyte diameter. Individuals from the lower-density treatment presented a smaller mean oocyte diameter, supplied with fewer oocytes, than individuals in both the higher-density treatment and the baseline group. Regardless of this one difference, all trial individuals were able to maintain their elevated gonadal developmental stage for a full period of five months past their reproductive peak, with female holothurians subjected to the higher-density treatment showing signs of increasing vitellogenic reserves, a considerable advantage in aquaculture broodstock rearing.

Acute and chronic effects of environmental realistic concentrations of simvastatin in danio rerio: evidences of oxidative alterations and endocrine disruptive activity

Due to their wide use, pharmaceuticals can be discarded, metabolized and excreted into the environment, potentially affecting aquatic organisms. Lipid-regulating drugs are among the most prescribed medications around the world, to control human cholesterol levels, in more than 20 million patients. Despite this massive use of lipid-regulating drugs, particularly simvastatin, the role of these drugs is not fully characterized and understood in terms of its potential toxicological effects at the environmental level. This work intended to characterize the toxicity of an acute (120 h post-fertilization) and chronic (60 days) exposure to the antihyperlipidemic drug simvastatin (in concentrations of 92.45, 184.9, 369.8, 739.6 and 1479.2 ng L−1), in the freshwater species zebrafish (Danio rerio). The concentrations hereby mentioned were implemented in both exposures, and were based on levels found in wastewater treatment plant influents (11.7 ± 3.2 μg L−1), effluents (2.65 ± 0.8 μg L−1) and Apies River (1.585 ± 0.3 μg L−1), located in Pretoria, South Africa and, particularly in the maximum levels found in effluents from wastewater treatment plants in Portugal (369.8 ng L−1). The acute effects were analysed focusing on behavioural endpoints (erratic and purposeful swimming), total distance travelled and swimming time), biomarkers of oxidative stress (the activities of the enzymes superoxide dismutase, catalase, glutathione peroxidase), biotransformation (the activity of glutathione S-transferases) and lipid peroxidation (levels of thiobarbituric acid reactive substances). Animals chronically exposed were also histologically analysed for sex determination and gonadal developmental stages identification. In terms of acute exposure, significant alterations were reported in terms of behavioural alterations (hyperactivity), followed by a general reduction in all tested biomarkers. Also, the analysis of chronically exposed fish evidenced no alterations in sex ratio and maturation stages. In addition, the analysis of chronically exposed fish evidenced no alterations in terms of sexual characteristics, suggesting that the chronic exposure of Danio rerio to simvastatin does not alter the sex ratio and maturation stages of individuals. This assumption suggests that simvastatin did not act as an endocrine disruptor. Moreover, the metabolism, neuronal interactions and the antioxidant properties of SIM seem to have modulated the hereby-mentioned results of toxicity. Results from this assay allow inferring that simvastatin can have an ecologically relevant impact in living organisms.

Reproductive Characters of the Ricefield Eel (Monopterus albus Zuieuw) in Babakan Village, Karang Lewas District, Banyumas, Central Java

One of the villages in Banyumas Regency which provides a high potential habitat for ricefield eel (Monopterus albus Zuieuw), a protogynous hermaphrodite, is Babakan. However, information concerning their reproduction cycles is lacking. This research aimed to understand the reproductive characters including Gonad Maturity Level (GML), Gonad Maturity Index (GMI), fecundity, egg diameter, and to examine the correlation of body length with both GML and GMI of the fish. We applied the survey method with purposive sampling design. The sampling was done once in a month for four times from November 2017 to March 2018. There were 30 samples for each sampling time (total of 120 eels). The results showed that the ricefield eels underwent intersex phase at a body length of 30.5-30.7 cm. The fish less than 30.5 cm were females, and those more than 30.7 cm was a male. The ricefield eel sex based on stages of gonad development was GML I (there were oocytes equipped with nucleus and cytoplasm), GML II (the presence of cortical alveoli stage), GML III (the stage of vitellogenesis), and GML IV (mature stage). The presence of degenerated oocytes and testicular lobes characterized their intersex stage. A testicular lobe characterized the male stage. The dominant GML during November, December, January, and March were GML I and II, GML I and II, GML III, and GML IV, respectively. Fecundity of the ricefield eels during the research was between 207 and 370 eggs, with an average of 252 eggs. The egg diameter of 0.22-2.5 mm indicated that the ricefield eel was on the batch spawner. The highest GMI of the eels occurred in January between 00017 and 0.0242 during the entire month of sampling. The body length of the fish did not correlate to their GML. On the other hand, their body length correlated to their GMI.

First comparative assessment of the reproductive cycle of three species of Chiton on a temperate rocky shore of the southeastern Pacific

AbstractThe present study provides the first assessment of the reproductive cycle of three common and widespread species of the genus Chiton, sympatric in rocky shores of Coquimbo, northern Chile (~30°S): C. granosus, C. cumingsii, and C. magnificus. From specimens seasonally sampled during a 2‐year period, a histological study was performed in order to describe the gonad structure and stages of gonadal development for each species. The morphological structure of the gonad was similar in the three species, with sexual cells developing from the gonad wall towards its center. The three species were gonochoric and iteroparous, with asynchronous gamete maturation at population level; in all seasons, sexual maturity was evident in small to large individuals of each species (≥25 mm in total length for C. cumingsii and C. granosus, and ≥47 mm for C. magnificus).