Gonad Index Research Articles

Efectos de las dietas de granulado seco sobre el crecimiento y la supervivencia del erizo de mar comestible Arbacia stellata (Blainville, 1825) para una factibilidad del equinocultivo

The sea urchin, Arbacia stellata is part of a new biofood landscape for the global marine non-food organisms to be used as nutraceuticals. A 98-day feeding trial (a simple completely randomized experimental design) was performed using specimens of A. stellata (n= 88; 29.3 ± 0.2 mm and 14.5 ± 0.3 g mean initial test diameter and weight, respectively) to evaluate the efficacy of three isoproteic diets containing crustacean and vegetable protein sources in different combinations, for developing a low-cost dry formulated diet for promoting their growth (in test diameter and weight), gonadal yield and survival. Diet 1 (shrimp, Penaeus vannamei), Diet 2 (Sacha Inchi, Plukenetia volubilis) and Diet 3 (mixed diet) were prepared. Six individuals per treatment were used. They were fed 1% in relation to the average body weight per container (0.86-0.97 g), every 48 hours under ad libitum condition. Diets 2 and 3 produced a significantly better performance for growth in test diameter 31.58 ± 0.21 mm, SGR= 0.0066 ± 0.0001 mm mo-1 and 31.18 ± 0.35 mm, SGR= 0.0064 ± 0.0001 mm mo-1, respectively. Similar results of growth in weight were obtained with diets 2 and 3, 19.13 ± 0.52 g, SGR= 0.0413 ± 0.0019 g mo-1 and 19.08 ± 0.48 g, SGR= 0.0377 ± 0.0017 g mo-1, respectively. Feed conversion ratio and gonadal index were better with diets 2 and 3. In general, the lowest performance was obtained with diet 1. Survival was greater than 54% and the starved group died on day 42. This study indicates that plant-based diets and the combination of various protein sources in the diets produced remarkable biological responses to A. stellata growth.

Gonad development and recruitment pattern of the oysters Crassostrea ariakensis and Crassostrea sikamea in a subtropical bay in China

The extent of oyster stocks and their habitat loss experienced on the Chinese coasts suggests that oyster restoration will be necessary to rebuild direct fisheries and recover lost ecosystem services. Limited understanding of oyster biology and ecology is among the potential barriers to successful restoration along the Chinese coasts. At a natural oyster bed in Jiantiao Bay, Sanmen County, China, the study compared gonad development and spawn duration of the Sumonie oyster Crassostrea ariakensis and the Kumamoto oyster Crassostrea sikamea through histological sections from May 2020 to March 2021. Their temporal and vertical recruitment patterns were simultaneously observed along an increasing tidal elevation gradient (0.1 m, 0.6 m, 1.1 m, 1.6 m, 2.1 m). The gonad index did not differ between the oysters (P>0.05), with the maximum values in June–August, but C. sikamea had a longer spawning duration (May–December) than C. ariakensis (May–October). Crassostrea ariakensis recruited to only the lower 3 tidal zones (0.1 m, 0.6 m, 1.1 m), and its recruits varied linearly and significantly as an inverse function of tidal elevation. Significant 2nd degree polynomial fits best described the relationships for C. sikamea recruits and tidal elevation. The greatest recruits were commonly observed at the mid intertidal zones (0.6 m, 1.1 m and 1.6 m). An evident vertical settlement pattern emerged for C. sikamea at both 1-day and 3-day experiments; the greatest settlement rates occurred in the 1.6 m tidal zone, intermediate rates occurred in the 1.1 m and 0.6 m, the lowest rates occurred in the 0.1 m and 2.1 m. The study concluded that C. sikamea sustained longer spawning and recruitment durations than C. ariakensis, and a strong zonation pattern in recruitment emerged; C. sikamea achieved its maximum recruits in the mid-tidal zone, while the recruits of C. ariakensis linearly decreased with increasing tidal elevation.

Effect of dietary cholesterol on ovarian development of Chinese mitten crabs (Eriocheir sinensis)

This study was conducted to evaluate the effect of cholesterol (CHO) on ovarian development of Eriocheir sinensis through a feeding trial. Crabs (average weight 43.35 ± 0.05 g) were randomly fed with one of three diets: 0% CHO, 0.4% CHO and 1.6% CHO for 16 weeks. Results indicated that the hepatosomatic index (HSI) and gonad index (GSI) of crabs fed with 0.4% CHO diet were significantly higher than those in the control group. (P < 0.05). Meanwhile, 0.4% CHO can significantly increase the gene expression of vtg and vgr in ovary (P < 0.05), thus promoting the accumulation of Vtg. The protein expression of MEK1/2, ERK, p-ERK1/2, Cyclin B and CDC2 were significantly increased in the 0.4% CHO group, therefore dietary CHO might promote oocyte maturation by activating MAPK signal pathway and cooperating with maturation promoting factor (MPF). Further exploration results showed that 0.4% CHO was able to significantly up-regulate the protein expression of STAR and SR-B1 to promote the transport of CHO to ovary, thereby providing sufficient substrates for estradiol (E2) synthesis. In addition, the results in vivo and in vitro shown that CHO could regulate the activities of enzymes such as CYP11A1 and CYP19A1 through the cAMP-PKA-CREB/SF-1 signal pathway and then affects the level of E2 in the organism. In summary, supplementing the appropriate amount of CHO in the diet can improve the E2 level of the organism, thus increasing the accumulation of nutrients in the ovary, promoting the completion of meiosis, and finally achieving the purpose of promoting ovarian maturation.

Effects of Vitamin C and Squid Oil Supplementation on Gonad Maturation of Climbing Perch Broodstock (Anabas testudineus Bloch).

This study aims to determine the effectiveness of adding vitamin C and squid oil to commercial feed for broodstock fish (Anabas testudineus Bloch) on the speed of gonadal maturation and growth. The study was conducted for three months using a completely randomized design with 4 treatments and 3 replications. The test fish were 10 each in each treatment hapa, the treatment of feed A (Commercial feed =CF); B (CF + Vit c 2gr/kg; C (CF+ squid oil 3 ml/kg) and D (CF+ Vitamin C 2 g/kg + Squid oil 3 ml/kg). Feed was given in the morning and evening satiation for 30 days. The results showed that the commercial feed added with a combination of vitamin C 2000mg/kg feed and squid oil as much as 3mg/kg feed (Treatment D) gave the best gonadal maturity level. This is indicated by the average Gonadosomatic Index (GSI) of 4.20% and the average HepatoSomatic Index (HSI) of 3.91%, higher than other treatments. Supported by statistical test results showed very significant differences in somatic gonadal index, hepatosomatic index, egg diameter and absolute fecundity. Meanwhile, growth and condition factors did not show significant differences. There is a tendency that if the dose of vitamin C and squid oil is increased again, it will be able to increase the gonad maturity of the broodstock of climbing perch.

Examination of the role of resveratrol in attenuating oxidative damage induced by starvation stress in the marine mussel, Mytilus coruscus, through regulation of the sirt1-mediated signaling pathway

Aquatic animals, such as the marine mussel, Mytilus coruscus, are regularly subjected to starvation due to conditions of food scarcity brought about by environmental change. Silent mating type information regulation 2 homolog 1 (sirt1) is triggered during animal starvation and participates in inflammation and stress responses. However, the function of sirt1 in Mytilus remains unknown; thus, exploring the effects of sirt1 will improve the understanding of the resistance of Mytilus to starvation. In this study, Mytilus coruscus were fasted for 9 days and treated with 20 μM resveratrol. The results indicated that sitr1 mRNA expression levels in the gonads and gills of mussels increased significantly after 3 days of starvation and significantly decreased after 9 days of starvation. 20 μM resveratrol significantly up-regulated sirt1 expression in the gonads and gills of mussels starved for 9 days. The condition factor and gonadal index considerably decreased in mussels under starvation stress. The activities of antioxidants SOD, CAT, GSH, GPX, and AKP were elevated after fasting for 3 days, but were reduced after starvation for 9 days, accompanied by histopathological damage in the gills and gonads. Resveratrol alleviates histological damage caused by starvation stress by enhancing antioxidant activity and reducing MDA production. Additionally, resveratrol decreased the mRNA expression levels of tlr4, myd88, and nfkb and increased the mRNA expression levels of ampk, foxo, and gadd45. Overall, the results suggest that resveratrol-induced sirt1 expression exerts a protective effect on mussels risking starvation by regulating TLR4/NFκB and AMPK/FOXO signaling pathways. This study might give us fresh insight into the effects of sirt1 on the response to starvation stress in mussels.

A metabolomic approach to study triptolide-induced ovarian damage in rats

Triptolide (TP) is the major active ingredient of Tripterygium wilfordii Hook, a traditional Chinese herb that possesses various pharmacological activities and has been used to treat autoimmune and inflammatory diseases for thousands of years. However, the clinical application of TP is limited due to its multiorgan toxicity, and in particular, its negative impact on female fertility. To date, the specific toxic mechanisms on reproduction induced by TP remain unclear. In the current study, an LC-MS/MS-based metabolomic approach was adopted to study TP-induced reproductive toxicity and its mechanism. Histopathological examination of the ovaries showed that TP significantly induced follicular atresia and decreased the numbers of corpus luteum in rats, as well as reducing the gonadal index and destroying the microstructure of the ovary. Immunohistochemical staining revealed that TP significantly induced apoptosis of rat follicle cells. Metabolomics analysis revealed that 67 and 74 small molecule metabolites in the ovaries and serum, respectively (fold-changes > 1.5, p < 0.05), were significantly different in TP-treated rats compared to CON group rats. Target profiling identified the metabolites arachidonic acid, prostaglandin D2, prostaglandin H2 and prostaglandin E2 as potential serum biomarkers for TP-induced ovary damage.

Effects of Dietary Lipid Levels on Growth and Gonad Development of Onychostoma macrolepis Broodfish

To assess the lipid requirements of O. macrolepis broodstock, five iso-nitrogenous diets (39 g kg−1) with five lipid levels, 50 (5 L), 70 (7 L), 90 (9 L),110 (11 L), and 130 (13 L; g kg−1), were made. A total of 105 three-year-old individuals (50.11 ± 2.86 g per fish) were divided into five groups (triplicate per group) and were fed with the diets, respectively, for eight weeks. Then, the fish were sampled, and items were determined. The results showed that growth rate and feed efficiency ratio were not significantly affected by diets (p &gt; 0.05). A clear dose–response effect of dietary lipid was observed on somatic indexes of gonad indexes of the O. macrolepis brookstock, with the highest values corresponding to fish fed 9 and 11 g kg−1 lipids, in contrast, gonad indexes were reduced as dietary lipid moved away from this level. The other somatic indexes, such as viscerosomatic index, perivisceral fat index, etc., were not significantly affected by diets (p &gt; 0.05). The content of crude lipid and crude protein in carcass, hepatopancreas, and gonad were not significantly affected by dietary lipid levels (p &gt; 0.05). The gonad fatty acids of 16:0 and 22:6n-3 decreased and 18:2n-6 increased with the increasing lipid level, being significantly altered by diets (p &lt; 0.05). The histological features of the gonad showed no significant difference among the five diets (p &gt; 0.05). The relative expression of sex steroid-synthesizing proteins (fshr, 3β-hsd, 17β-hsd, aro., and star.) in the gonad of fish was most significantly highly expressed in the 9 L and 11 L groups (p &lt; 0.05). The results suggested that a proper dietary lipid level of 90–110 g kg−1 could maintain gonad development of O. macrolepis broodstock without affecting growth performance.

Sexual reproduction and biometry of the non-zooxanthellate papillose cup coral Paracyathus pulchellus

Basic information on the reproductive biology of many scleractinian corals species is limited or entirely lacking, particularly from temperate zones, though it is essential for a better understanding of their ecology. This study describes the morphological aspects and the annual cycle of gametogenesis and biometric parameterss of the papillose cup coral Paracyathus pulchellus collected at Palinuro (Italy, Southern Tyrrhenian Sea), filling a knowledge gap about the reproductive biology of a widespread Mediterranean and Northern Atlantic coral. Samples of P. pulchellus were collected by SCUBA diving between 5- and 10-meters depth during 18 monthly collections from June 2010 to December 2011. Sexually active polyps displayed either oocytes or spermaries, indicating that P. pulchellus was gonochoric. The sex ratio of sexually active polyps was 1:1. Gametogenesis began with undifferentiated germ cells arose in the gastrodermis that migrated towards the mesoglea of the mesentery where they completed the development. During spermatogenesis, spermary diameter increased from 25 to 83 µm. Oocyte diameter ranged from 9 to 146 µm and during oogenesis the nucleus/cytoplasm ratio decreased due to the accumulation of yolk. The nucleus migrated to the periphery of the oocyte adhering closely to the cell membrane. No embryo was observed in the coelenteric cavity of the polyps, suggesting an external development of planktotrophic larvae due to the small-sized mature oocytes and a possible broadcast spawning reproductive mode. Gonadal index of both females and males increased significantly from August until November and fertilization took place from November to January. Only sexually inactive individuals were observed from February to April, suggesting a quiescence period in both males and females. Seasonal variations in water temperature and photoperiod may have a key role in regulating gametogenesis. The analysis of the main biometric parameters (polyp width, height, dry skeletal mass, volume, surface/volume ratio and bulk skeletal density) showed a negative correlation between size and skeletal density, and no sexual dimorphism.

Gonad indices, morphology and muscle fatty acid compositions of male and female golden mahseer (Tor putitora) sampled from lake Bhimtal (Himalaya) at different seasons of the year

Adult male and female golden mahseer (n = 10–12) were collected during summer, monsoon, pre-winter and winter for evaluating gonadal seasonality, condition factor (CF), viscera-hepatosomatic index (VHSI), hepatocyte density (HD) and muscle fatty acid (FA) profile. In summer and monsoon, all males, but only 67% and 71% of females, were spawning capable in respective seasons. In pre-winter, males were mostly in regressing, but females were in regenerating phases. In winter, 50% of males and 14% of females were in the early spawning capable phase. VHSI and HD, in males only, were respectively highest and lowest in winter, indicating their nutrient recovery starting in pre-winter and completing in winter. Seasonal muscle FA profile of females only was linked to gonadal status, where C20:1, C22:1, C18:3n-6, C18:3n-3, C20:4n-3, C22:6n-3, total n-3 and n-6 FAs were depleted in peak spawning seasons. Overall, it was found that their spawning peak falls in summer and monsoon, but few early and late spawners were detected in winter and pre-winter, respectively. Males and females exhibited a different reproduction-linked nutrient allocation pattern; hepatic nutrient dynamic was prominent in males, but muscle FA dynamic was pronounced in females. CF dynamic was similar in both sexes.

Reproductive Cycle and Sexual Group Maturity of Buccinum osagawai (Neogastropoda: Buccinidae)

This study was performed to obtain information on the basic reproductive ecology and biological resource management of Buccinum osagawai. Samples were collected from August 2018 to October 2019 with a drum-shaped net at a depth of 150–250 m along the continental shelf in Jumunjin, on the east coast of Korea. The species showed gonochorism and a lack of external sexual dimorphism. The overall sex ratio (F:M) was 1:1.2 (n = 549, F = 250, M = 299); as the size of the individuals increased, the proportion of males tended to decrease. The development pattern of the oocyte was synchronous, in which a dominant group of oocytes was identified within the same ovary. The size of the ripe oocyte was 82.3 (±22.6) × 125.5 (±22.0) μm. The spermatocyte development pattern was group-synchronous, in which multiple stages of germ cell populations were simultaneously identified within the same spermatogenic acinus. The gonad index (GI) for both males and females showed the highest value during June, after which it decreased sharply, and after August it was below 2.0. The main spawning season was from June to July, and the GI and stages of gonadal development did not show a pattern of seasonal changes. The main gonadal active season was from May to July, and both male and female gonadal development and maturation took place over a short period, whereas the recovery period after spawning was longer. At least 60.5% of the group, considering both males and females, showed maturity at 50.1 mm SH or more. Furthermore, the size of 50% group maturity was shown at approximately 50.0 mm SH.

Reproductive cycle of two marine sentinel bivalve species (Donax trunculus and Scrobicularia plana) in the Agadir bay, Southern Morocco

The reproductive cycle of two marine sentinel bivalve species, Donax trunculus and Scrobicularia plana, was studied from monthly random samples. A total of 1200 specimens were collected from January to December 2019 in two different sites of Agadir bay (Agadir beach; AG and Oued Souss estuary; OS). The analysis was based on the temporal variation of condition index, gonadal index, sex-ratio, and maturity stages of gonads through histological observation. We also studied the environmental parameters and their impact on the reproduction of those species. Results indicate that the sex-ratio was slightly unbalanced in favor of females in AG (▪= 1: 1.3) and males in OS (▪= 1: 0.9). Stages of gonad development maturity were identified as five stages: undifferentiated, developing, ripe, spawning, and spent. The spawning period occurred from March to July for S. plana, and from May to August for D. trunculus; the two species had one annual gonadal cycle. During the microscopic observations, no parasitic infection was detected. The physico-chemical parameters; especially temperature, dissolved oxygen, pH, and precipitation, influenced the gonads maturity and the spawning process in the studied species.

Gonad traits in the sea urchin Mesocentrotus nudus fed on the kelp Eisenia bicyclis: Gametogenesis promotion and lack of sea urchin-like taste

Perennial Eisenia bicyclis kelp beds are one of the main fishing grounds for the sea urchin Mesocentrotus nudus, whose gonad is highly valued. However, little is known about the gonad quality of sea urchins fed on this species of kelp. Feeding with two other kelp species, the biennial Saccharina japonica blade or sporophylls of the annual Undaria pinnatifida, is known to improve the gonad quality of M. nudus. The present study investigated the dietary effects of blades of E. bicyclis on gonad quality of M. nudus in comparison with feeding on S. japonica blade or U. pinnatifida sporophylls. The gonad index of urchins fed E. bicyclis (UEB) increased from 8.2 to 16.9, similar to those fed on S. japonica (USJ), which was significantly lower than those fed on sporophylls of U. pinnatifida (UUP). Of UEB, 69% had premature gonads, indicating that UEB gonads were significantly advanced to maturation compared with those of USJ or UUP, most of which were still in the growing stage. The uncoupling of gonad size and advance to maturation is not explained by the high protein content in E. byciclis, suggesting that unknown substances in E. bicyclis can promote gonad maturation. UEB gonads improved color, texture and contents of glutamic acid, alanine, and arginine similar to results obtained with USJ. However, the methionine and valine contents of UEB gonads were below the threshold of detection, explaining the lack of sea urchin-like taste of the gonads. Many unpleasant odors were detected from the gonads of UEB. In conclusion, gonad flavor of UEB is inferior compared with that of USJ or UUP. Further research is required to understand the details of gametogenesis under dietary supplementation with the species-specific compounds present in E. bicyclis.

Reproduction and population dynamics of the invasive bivalves Mytilopsis sallei and Isognomon bicolor on the Northeast coast of Brazil

Knowing the reproductive biology and population dynamics of invasive species are essential for environmental conservation and protection of native species. The success of these invasive species is directly linked to their reproductive strategy. Therefore, this study aimed to describe the reproductive cycles and evaluate population parameters of the invasive bivalves Mytilopsis sallei and Isognomon bicolor, and to estimate if those characteristics would favor their population growths in the northeast coast of Brazil. The bivalves were sampled monthly from June 2016 to May 2017, respectively from the Sanhauá River estuary and Jacarapé beach, State of Paraíba, Northeast Brazil. Through histological analyses, reproductive parameters were determined in order to identify sex, gonadal development, minimum size at maturity, and mean gonadal index. The asymptotic growth (L∞) and growth rate (K) parameters were estimated using the von Bertalanffy growth curve, and recruitment patterns and cohorts were projected based on shell length frequency distributions. Mytilopsis sallei presented more than 50% spawning individuals in most months, while animals showing gametogenic gonads were predominant during the season of greatest precipitation. Isognomon bicolor had ripe gonads (about 30%) and spawning individuals (more than 40%) in all months of the year, but unlike M. sallei, it had the highest concentration of ripe individuals in the months of greatest precipitation. Both species showed equal and high growth rates (K = 1.1 yr-¹) and analysis of the cohorts indicated that these populations are established and expanding. The results confirmed the great invasive potential of the two species in their local environments (estuary and marine) in Northeast Brazil and, therefore, their harmful potential for the conservation of native species and the environment in the invaded areas.

Long-day photoperiods affect expression of OPN5 and the TSH-DIO2/DIO3 pathway in Magang goose ganders

This study sought to understand the regulation mechanism of OPN5 through the TSH-DIO2/DIO3 pathway mediated photoperiod on the breeding activity of short-day breeding birds. In this study, the reproductive activity of Magang goose was regulated by artificial light, and the reproductive activity of the ganders were determined according to the daily laying rate of female geese. The testicular development and the serum reproductive hormone concentrations of ganders were measured during the reproductive period (d 0), the reproductive degeneration period (d 13 and 27) and the resting period (d 45). The mRNA and protein expression patterns of OPN5, the HPG axis reproductive genes, and TSH-DIO2/DIO3 pathway related genes were examined. Results showed that the laying rate of geese and the gonadal indices (GSI) decreased gradually after the photoperiod increased. Histological observation found that the spermatogenic function of the testis was normal on d 0 and 13, while degeneration occurred by d 27 and 45. Serum testosterone, FSH, and LH concentration showed a slight increase on d 13, followed by a sharp decrease on d 27 and 45 (P < 0.01), while PRL concentrations were low on d 0 and 13, and increased rapidly on d 27 and 45 (P < 0.01).The expression pattern of GnRH, FSH, LH, and THRβ mRNA were similar, with high levels on d 0 and 13 and a decreasing trend on d 27 and 45 (P < 0.05 or P < 0.01); and GnRHR mRNA levels were higher on d 13 (P < 0.05), but then had decreased by d 27 and 45 (P < 0.01). The expression pattern of GnIH and GnIHR was similar, which was opposite to that of GnRHR. VIP, PRL, and PRLR increased gradually and peaked on d 45 (P < 0.01). The expression trend of TRH, TSHβ, and DIO2 was similar to that of GnRHR, and the expression abundance increased on d 13, and then decreased on d 27 and 45. GnRH protein expression was significantly higher than during the other 3 periods (P < 0.01) while the GnIH protein levels were extremely low on d 0, had gradually increased by d 13, and significantly increased by d 27 and 45 (P < 0.01). The protein expression trends of THR and DIO2 were similar to that of GNIH. DIO3 protein expression was low on d 0 and 13, and increased by d 27 and 45. These results suggest that when the photoperiod increased, the hypothalamus OPN5 gene and protein were upregulated and the pituitary TSHβ, TSHR, and hypothalamus THRβ, TRH, and DIO2 were downregulated, and thus the reproductive activity of geese was inhibited.

Gonadal cycle, reproductive indices and detection of parasitism in the clam Ameghinomya antiqua in natural beds of importance for fisheries.

The clam Ameghynomia antiqua is a highly important resource for fisheries due to its high catches volume. It is the bivalve mollusc with the highest fisheries landings from natural beds on the Pacific coast of southern South America; however, studies of the reproductive conditions of this species are scarce and date back many years. The object of the present work was to evaluate the reproductive characteristics of the species, analysing its gametogenic and gonadal cycle, and reproductive indices, in fishery locations that present the natural beds with the highest fisheries catches, as well as parasite loads in the species. The gonads of the individuals were sampled monthly over a year and classified into one of three states called: “in development”, “ripe” and “spawned”. Synchrony between the sexes was observed in the indicators of the Gonadosomatic Index and Condition Index in each of the locations, although no synchrony was observed between locations. In the gametogenic cycle, the "ripe" state was observed in females in spring-summer, followed by rapid recovery to new development of the gonads; in males the "ripe" state was observed throughout the year. It was observed that males entered the “spawned” state one month ahead of females. The presence of digenean parasites in the state of metacercariae was detected in the gonads and mantle. No significant differences were found in the prevalence or intensity of infection when analysed by sex and month. The metacercariae were identified, by sequencing of three DNA regions, as belonging to the clade shared by species of the genus Parvatrema and close to the Gymnophalloides; both these genera belong to the family Gymnophallidae of the superclass Digenea. Infection was observed to reduce the gonadal tissue, in some cases causing castration. This is the first record of the presence of these parasites of A. antiqua, with genetic identification at genus level. These results are relevant for act proper management of this resource, which is important for fishing.

Long-term exposure of the Mediterranean mussels, Mytilus galloprovincialis to polyethylene terephthalate microfibers: Implication for reproductive and neurotoxic effects

As one of major types of microplastics (MPs), microfibers (MFs) are widely found in the marine ecosystem and can induce diverse impacts on various marine organisms. Sedentary species, such as mussels, can act as bioindicators for monitoring marine contamination. Hence, in this study, we used mussels (Mytilus galloprovincialis) to examine the toxicity of polyethylene terephthalate (PET) MFs of 100 μm size at concentrations of 0.0005, 0.1, 1, 10, and 100 mg/L for 32 days. PET MFs accumulated only in the stomachs and intestines of the mussels and caused digestive tubule atrophy. After exposure to PET MFs, no alteration in the mortality rate, shell height, length, and weight of the mussels was observed. However, the gonadal index decreased with increasing concentrations of PET MFs. This is because PET MFs decrease the sex hormones estradiol and testosterone in mussels, even at environmentally relevant concentrations. Furthermore, chronic exposure to PET MFs increased the activities of antioxidant-related (catalase and superoxide dismutase) and neurotoxicity-related (acetylcholine esterase) enzymes in the digestive gland and gill tissues of mussels. In addition, cellular immune parameters of apoptosis and DNA damage were observed in mussel hemocytes. Thus, this study demonstrates the risks of MPs in real marine environments by assessing how long-term exposure to low concentrations of PET MFs can cause potential sublethal impacts and reproductive failure in mussels.

Evaluation of the reproductive cycle and gonadal development in the climbing perch, Anabas testudineus (Bloch, 1792) in captivity

The climbing perch Anabas testudineus, the most demanded indigenous fish species of India, were used for the evaluation of reproductive strategy and gonadal development at first maturation under the controlled laboratory condition. In both sexes, four distinct gonadal developmental stages namely preparatory, pre-spawning, spawning, and post-spawning were identified based on the gonadosomatic index (GSI), hepatosomatic index (HSI), gonadal morphology, and the levels of serum sex hormones. The spawning stage was identified from July and August and the fecundity ranged from 6500–11000 eggs. The GSI exhibited a significant increase from preparatory to pre-spawning and spawning stages, and maintained high until August. The HSI was maintained the same during preparatory, pre-spawning, and spawning stages while increased in post-spawning stage in both sexes. Serum estrogen and testosterone levels increased significantly during pre-spawning, and spawning stages in both sexes. Fecundity showed a positive correlation with the length, weight, and ovary weight. Histological sections showed that male A. testudineus were group-synchronous spawners. Both sexes showed discrete reproductive cycles characterized by distinct changes in gonadal size, sex hormones and gonadal indices. This study will bridge the gap of insufficient knowledge to support the best practices suitable for the A. testudineus culture and survival under captivity.

Modest Dietary Protein Requirement for Sea Urchin Gonad Production Demonstrated by Feeding Trials with Consideration of Protein Leaching

This study is aimed at revealing the dietary protein requirement for gonad production in the sea urchin Mesocentrotus nudus, with consideration of protein leaching from diets during seawater immersion. Feeding trials were performed on M. nudus using two diet types with low capacities for protein leaching: starch diets (STG) containing 0–40% gluten in 10%, 5%, and 4% increments (experiments 1–3) and alginate diets (ALG) containing 5–25% gluten in 5% increments (experiment 4). The protein content in the diets was determined after they were immersed in seawater for 24 h or 72 h. The gonad indices of urchins fed STG with 11.4–19.3% protein were significantly higher than those fed STG with 7.8% protein. The protein requirement was estimated to be 12% based on a broken-line regression analysis of urchins fed STG in experiments 1–3. In experiment 4, the gonads became larger as dietary protein content increased from 4.5% to 12.0%, and the sizes were similar to those of urchins fed ALG with 12.0–21.1% protein. The estimated value of 12% was much lower than that reported previously (&gt;20%), indicating that the protein requirement for sea urchin gonad production is modest when the protein-leaching problem is addressed.

Reproductive cycle of the golden carpet shell (Polititapes aureus) in the Ria Formosa lagoon (southern Portugal)

AbstractThe present study described the gametogenesis and assessed the pattern of energy storage throughout the reproductive cycle of the golden carpet shell (Polititapes aureus) from the Ria Formosa lagoon (southern Portugal). Monthly sampling was performed for two years (March 2016–February 2018) and the study was based on gonad histology, complemented by the estimation of the mean gonadal index, body condition index and biochemical composition. The species’ reproductive cycle presented a seasonal pattern, with a resting period mainly between October and January and gametogenesis beginning around February–March. The spawning season of P. aureus was shorter in 2016 (June–September) than in 2017 (May–October). Furthermore, ripe individuals were very scarce (1.3%) in 2017 compared with the previous year (11.4%). Mean gonadal index (GI) reflected the species’ reproductive cycle and the body condition index (CI) and biochemical composition of the individuals exhibited high variation between years. Regarding the biochemical composition, proteins ranged between 190.6 and 595.2 μg mg−1, glycogen from 5.7 to 102.6 μg mg−1 and total lipids between 31.6 and 80.7 μg mg−1. The reproduction of P. aureus was strongly influenced by fluctuations in both seawater temperature and chlorophyll a, as reflected through the temporal variation in the gonadal cycle, condition index and biochemical composition. Overall, the information gathered in this study is valuable to propose scientifically based harvesting management measures for the long-term sustainable exploitation of this shellfish resource, further reinforcing the importance of implementing adaptive fishery management strategies to cope with global climate change.

Effects of stocking density on ovarian development and maturation during the rearing period in Shan-ma ducks

Stocking density critically affects the growth and subsequent performance of animals in modern poultry production. This study investigated the effects of stocking density on ovarian development, ovarian maturation, and the mRNA expression of key genes in the reproductive axis during the rearing period of Shan-ma ducks. The experiments involved 180 healthy 7-wk-old Shan-ma ducks and randomly divided into low stocking density (LSD; n = 30, density = 5 birds/m2), medium stocking density (MSD; n = 60, density = 10 birds/m2) and high stocking density groups (HSD; n = 90, density = 15 birds/m2), for rearing. After examining ovarian development and measuring hormone levels in the plasma and expression levels of key regulatory genes in the reproductive axis at 19 wk of rearing, analysis of the gonad index analysis, reflecting stocking density, uncovered statistically significant differences. The gonad index of the LSD group was significantly higher than those of the MSD and HSD groups (P < 0.01), while no significant difference was observed between the MSD and HSD groups. pre-ovulatory follicles (POFs) and small yellow follicles (SYFs) development was only apparent in the LSD group, with the large white follicles (LWFs) number of this group being significantly higher than that of the MSD group (P < 0.05). The blood levels of E2 (estradiol), P4 (progesterone), and T (testosterone) were significantly higher in the LSD group than in the MSD and HSD groups (P < 0.05 or 0.01). Also, the levels of both P4 and T were significantly higher in the MSD group than in the HSD group (P < 0.01). The gene expression levels of GnRHR, FSH, AMHR, and FSHR were significantly increased in the LSD group compared to the MSD and HSD groups (P < 0.05 or 0.01), while the expression levels of GnIHR and GDF9 were significantly decreased in the LSD and MSD groups compared to the HSD group (P < 0.05 or 0.01). Steroid biosynthesis pathway genes such as StAR, CYP11A1, 3β-HSD, CYP19A1, and BMP15 were significantly downregulated at greater stocking densities (P < 0.05 or 0.01). Likewise, the protein expression of StAR, 3β-HSD, and CYP19A1 was also significantly decreased (P < 0.05 or 0.01). These results demonstrate that both medium and high stocking densities suppressed the expression of the key reproduction-promoting factors, while the expression level of the key reproductive inhibitory factors was enhanced. Therefore, rates of ovarian development and maturation could be reduced by a high stocking density leading to a delay in reproduction performance during the rearing period of Shan-ma ducks.