Female Spawning Research Articles

БИОЭКОЛОГИЯ И РАЗВИТИЯ КАЛИФОРНИЙСКОЙ ЩИТОВКИ (QUADRASPIDIOTUS PERNICIOSUS COMST.) В УЗБЕКИСТАНЕ

Dangerous coccids are widespread in Uzbekistan. Of these, the californian shield insect is a quarantine pest. It damages many plants. It damages apple, pear, plum, quince, peach, almonds, hawthorn, elm, poplar and others. Diapausing larvae of the first age overwinter, covered with a dark gray or black shield. In spring, it feeds intensely, molts and forms a shield similar to that of an adult female. After the second molt, adult females are formed. After mating, the female spawns larvae of strollers, which spreads along branches and leaves, and can also settle on fruits. It gives rise to the next generation

Identifying peak breeding season and estimating size at first maturity of mud crab (Scylla olivacea) from a coastal region of Bangladesh

Recently mud crab (Scylla olivacea) has emerged as a potential export commodity. Its farming is increasing rapidly in Bangladesh because of its lucrative price and high demand in international market. However, the farming or fattening of mud crab is totally dependent on capture of wild crablets. A huge quantity of mud crabs is being caught indiscriminately from nature and thus putting intense pressure on its wild stock, which is a major concern of conservation. Imposing ban at peak breeding season and setting a legal capture size are considered effective management tools for safe migration and spawning of berried females. There is contradictory information on breeding season of mud crab in Bangladesh. Thus, it is crucial to identify the peak breeding season of it and to formulate conservation policies to protect the berried crabs. Live crabs were collected year-round from the river adjacent to southwest part of Sundarbans. Although mud crab breeds throughout the year, March–April was identified as the peak breeding season of it. The second peak was observed in August–September. The highest abundance of crablets (1–2 months age) was recorded in May–June, and the lowest in January–February. Immature crablets were found all through the year that proves that mud crab is a continuous breeder. The highest amount of GSI value (11.6) was observed in February–March, which indicates that the breeding is very near. The size at first maturity (M50) was estimated as 95.5 mm CW which lied at size class 91–100 mm (CW). The findings from the study will assist in fixing up the banning time and thus protecting the mother crabs; and will assist in formulating police to conserve and protect juvenile crabs in the sense that the minimum legal capture size of crabs will allow the adults to mate and spawn at least once before their capture.

Myricetin Possesses Anthelmintic Activity and Attenuates Hepatic Fibrosis via Modulating TGFβ1 and Akt Signaling and Shifting Th1/Th2 Balance in Schistosoma japonicum-Infected Mice.

Schistosomiasis is a zoonotic and debilitating parasitic disease caused by Schistosoma japonicum. Praziquantel remains the choice for treating schistosomiasis, but its efficacy could be hampered by emergence of resistance. In this study, using large-scale drug screening, we selected out myricetin, a natural flavonol compound, having a good anti-schistosome effect. We found that myricetin exhibited dose and time-dependent insecticidal effect on S. japonicum in vitro, with an LC50 of 600 μM for 24 h, and inhibited female spawning. The drug mainly destroyed the body structure of the worms and induced apoptosis of the worm cells, which in turn led to death. In addition, oral administration of myricetin in mice infected with S. japonicum showed a deworming effect in vivo, as evidenced by a significant reduction in the liver egg load. H&E staining, quantitative RT-PCR, and Western blotting assays showed that myricetin significantly alleviated liver fibrosis in mice infected with S. japonicum. Myricetin also effectively inhibited the expression of TGFβ1, Smad2, phospho-Smad2, Smad3, phospho-Smad3, ERK, phospho-ERK, Akt, and phospho-Akt in the liver of infected mice, suggesting that myricetin attenuated liver fibrosis in mice via modulating TGFβ1 and Akt signaling. Flow cytometric analysis of Th subtypes (Th1/Th2/Th17/Treg) in the mouse spleen further revealed that myricetin significantly increased the percentage Th1 cells in infected mice and reduced the proportion of Th2 cells and Th17 cells. Immunology multiplex assay further showed that myricetin attenuated S. japonicum-induced rise in the plasma levels of IL-4, IL-5, IL-10, IL-13, and IL-17A in infected mice while increasing the plasma contents of IFN-γ, IL-12, and IL-7. In conclusion, our study provides the first direct evidence that myricin possesses potent anti-schistosome activities in vitro and in vivo, and offers new insights into the mechanisms of action by myricetin. The present findings suggest that myricetin could be further explored as a therapeutic agent for S. japonicum.

Both Dietary Ratio of n-6 to n-3 Fatty Acids and Total Dietary Lipid Are Positively Associated with Adiposity and Reproductive Health in Zebrafish.

ABSTRACTBackgroundControversial findings have been reported in human and animal studies regarding the influence of n–6 (ω-6) to n–3 (ω-3) fatty acid ratios on obesity and health. Two confounding factors may be related to interactions with other dietary lipid components or sex-specific differences in fatty acid metabolism.ObjectiveThis study investigated main and interactive effects of total dietary lipid, ratio of n–6 to n–3 fatty acids, and sex on growth, adiposity, and reproductive health in wild-type zebrafish.MethodsMale and female zebrafish (3 wk old) were fed 9 diets consisting of 3 ratios of n–6 to n–3 fatty acids (1.4:1, 5:1, and 9.5:1) varied within 3 total lipid amounts (80, 110, and 140 g/kg) for 16 wk. Data were then collected on growth, body composition (determined by chemical carcass analysis), and female reproductive success (n = 32 breeding events/diet over 4 wk). Main and interactive effects of dietary lipid and sex were evaluated with regression methods. Significant differences within each dietary lipid component were relative to the intercept/reference group (80 g/kg and 1.4:1 ratio).ResultsDietary lipid and sex interacted in their effects on body weight (P = 0.015), total body length (P = 0.003), and total lipid mass (P = 0.029); thus, these analyses were stratified by sex. Female spawning success decreased as dietary total lipid and fatty acid ratio increased (P = 0.030 and P = 0.026, respectively). While total egg production was not associated with either dietary lipid component, females fed the 5:1 ratio produced higher proportions of viable embryos compared with the 1.4:1 ratio [median (95% CI): 0.915 (0.863, 0.956) vs 0.819 (0.716, 0.876); P < 0.001].ConclusionsFurther characterization of dietary lipid requirements will help define healthy balances of dietary lipid, while the sex-specific responses to dietary lipid identified in this study may partially explain sex disparities in the development of obesity and its comorbidities.

Сравнительная оценка гормональных индукторов искусственного нереста самок африканского клариевого сома

Сравнительная оценка гормональных индукторов искусственного нереста самок африканского клариевого сома

Screening of Biomarkers Related to Ovarian Maturation and Spawning in Blunt Snout Bream (Megalobrama amblycephala) Based on Metabolomics and Transcriptomics.

In fish breeding practices, gamete maturity of females is vital to reproductive success. For some species, it is possible to estimate the female maturation status based on abdomen observation, but quite difficult for some species which mature at big size. To screen out the potential biomarker in fish blood relating to female maturation, we employed the approach integrating the UPLC-MS/MS and RNA-seq techniques to investigate the metabolites and genes reflecting the sexual maturation and spawning of female blunt snout bream Megalobrama amblycephala. The study included four groups, 1-year-old immature female individuals, 2-year-old immature female individuals, 2-year-old sexually mature female individuals, and 2-year-old sexually mature female individuals after 24h of successful spawning. The upregulated metabolites in mature females were involved in "steroid hormone biosynthesis," "metabolic pathways," "glycerophospholipid metabolism," etc. compared with those of immature individuals. As the key intermediate of steroid hormone biosynthesis, 17α-hydroxypregnenolone exhibited the highest level in 2-year-old mature females than in the immature females. Meanwhile, the metabolites (i.e., dodecanoic acid and myristic acid) participating in fatty acid synthesis exhibited much lower levels in the females after spawning than those before spawning. In addition to the metabolites, the genes involved in ovarian steroidogenesis were significantly upregulated in the 2-year-old immature females compared to the 1-year-old immature females, indicating that the ovarian steroidogenesis plays important roles in ovarian development of M. amblycephala at the early stages. The significant upregulation of genes (i.e., itpr1, camk2, and mekk2) involved in the "GnRH signaling pathway" was observed in the mature females compared with the immature females, which indicated that the estrogen levels increased after female maturation in M. amblycephala. Moreover, many genes (e.g., gck, creb1, tf2-9, ryr2, asgr1, and creb1) regulating insulin secretion and thyroid hormone synthesis were significantly downregulated after female spawning. The dynamics of gene expression and metabolites observed in this study provide novel cues for guiding fish practical artificial reproduction.

Drivers of male sound production and effective communication distances at fish spawning aggregation sites

AbstractWhile monitoring fish sounds has enhanced our understanding of spatio-temporal patterns of spawning and acoustic communication, data interpretation often fails to account for environmental effects on acoustic recordings, resulting in uncertainty of whether measures of detected fish sounds correspond to rates of sound production, specific behaviours, and abundance. In this study, we applied acoustic propagation modelling and detection theory to estimate rates of sound production of territorial, male Gulf grouper (Mycteroperca jordani) from passive acoustic recordings and evaluate effective communication distances. To assess behavioural drivers, environmentally calibrated, hourly estimates of sound production rates were compared to diver observations of courtship, spawning, and numbers of females encountered within male territories. Rates of sound production increased before sunset and were correlated to observed rates of spawning and females encountered, indicating that sound production is largely driven by female presence and increased opportunities to spawn. The mean effective communication distance was estimated to be &amp;lt;21 m, supporting the importance of short-range communication within the observed behaviours. Our findings corroborate that fish sounds can be used to infer measures of reproductive activity and the relative abundance of both sexes during spawning periods once properly calibrated for environmental effects and detection capabilities.

Distribution and Life History of Spawning Capelin in Subarctic Alaska

AbstractCapelin Mallotus villosus is a coldwater, marine forage fish that responds quickly to environmental fluctuations; however, little is known about Capelin in Alaskan waters. The objective of the current study was to better understand the distribution and life history of spawning Capelin in northern Norton Sound, Alaska. Surveys were conducted from May through July 2018 to locate and estimate the size of nearshore Capelin aggregations prior to spawning, identify the location and timing of spawning events, characterize spawning habitat, and collect actively spawning fish to examine life history characteristics (e.g., body size, age, fecundity, etc.). Most (85.9%) of the nearshore aggregations were less than 12 m2 in surface area. Spawning Capelin were collected in Norton Sound between June 15 and June 21. At spawning locations, gravel and coarse sand accounted for over 70% of the proportional weight of sediment collected within a beach, and all sediment samples contained Capelin eggs. Spawning males were larger than spawning females in TL (mean ± SD = 148.8 ± 6.7 mm versus 137.0 ± 8.4 mm, respectively) and total weight (21.2 ± 2.9 g versus 13.7 ± 3.0 g), and both sexes were predominately age 3 (age range = 2–4 years). Absolute fecundity was 9,219 ± 4,529 eggs, and the gonadosomatic index was 1.09 ± 0.32% for males and 21.69 ± 8.21% for females. Nearshore aggregation sizes in Norton Sound were smaller than those reported for Newfoundland, but spawning behavior, timing, and water conditions were similar to observations from other Capelin spawning regions (e.g., Greenland), as were size, age, fecundity, and gonadosomatic index estimates. Although the results from the current study update baseline information on spawning Capelin in northern Norton Sound, continued research on their distribution and life history is needed to better understand ecosystem function in the North Pacific Ocean.

Nests placements and spawning in the endangered horseshoe crab Tachypleus tridentatus (Leach, 1819) (Merostomata: Xiphosurida: Limulidae) in Sabah, Malaysia

Abstract Horseshoe crab populations are declining worldwide, and Tachypleus tridentatus (Leach, 1819) has recently been classified as Endangered in the IUCN Redlist. Among the keys for species survival is successful reproduction. Although there are reports on the reproduction, particularly details on the spawning behaviour, of the American species, Limulus polyphemus (Linnaeus, 1758), information on Southeast Asia species is very scant. This field study reports the nesting activities of T. tridentatus at Jambongan Island, Sabah, Malaysia. Observation were carried out on 16 spawning pairs that were spotted during full and new moon from April-July 2016 in Sabah. Nest placements, number of nests, number of eggs, time spent at each nest, and nest widths, depth, and distance from the highest tide line were recorded for each pair. Tachypleus tridentatus generally laid an average of 967 ± 54.1 eggs/nest (171–2,282) in as many as nine nests on the intertidal zone between 125 and 940 cm from the highest tide. The first nest was dug once the tide began rising, followed by the consecutive nests towards the highest tide line with nest depths ranging between 13 and 22 cm. The complete spawning session (first nest to the last) ended in less than two hours. Time spent in spawning correlates positively with the number of nests and the total number of eggs laid by each spawning female. The spawning area, which is made up mainly by fine and medium-size sediment grains, also experience stable temperature, salinity, and dissolved oxygen conducive for egg-laying and larval development for successful reproduction. The details of spawning are important for planning successful future conservation initiatives for the species, especially in tropical regions.

Effect of Garcinia kola seeds supplemented diet on growth performance and gonadal development of Oreochromis niloticus juveniles breed in ponds

BackgroundDespite the favorable geo-climatic potential of Cameroon, the national production of tilapia remains low due to poor tilapia growth reported by fish farmers. One of the underlying reasons is the early female maturation at a very small size and precocious breeding in earthen ponds, resulting in overpopulation which leads to stunted growth and therefore to the production of unmarketable fish size. Studies have shown that dietary supplementation of G. kola enhanced growth in young Clarias gariepinus and Oreochromis niloticus. It was also reported that G. kola inhibited spawning in Tilapia adult females. Therefore, this study sought to assess the effects of Garcinia kola as growth promoter and inhibitor of gonadal development in young Oreochromis niloticus.MethodsA total of 108 juveniles weighing 13.32 ± 0.62 g were randomly distributed in 9 hapas of 12 fishes each (9 females and 3 males) and fed for 70 days with three isonitrogenous diets, 40% crude protein with increasing Garcinia kola supplementation levels of 0 (normal diet), 6% and 10% (experimental diets). Physico-chemical parameters of the water (temperature, dissolved oxygen, pH, nitrate, nitrite, ammonia, and transparency) were measured twice a week. Every 14 days, fish were harvested, counted, and weighed. At the end of the experiment, three fish of each sex per replicate were sacrificed and their gonad and liver collected and weighed. Data were statistically analyzed using one-way analysis of variance repeated measure followed by Newman-Keuls multiple tests.ResultsThe results showed that all physico-chemical parameters of the water were within the recommended values for Tilapia culture. Tilapia fed 6% Garcinia kola supplemented diet displayed higher final body weight in males (38.60 ± 3.50 g) and females (36.77 ± 3.62 g) compared to those receiving normal diet (36.23 ± 1.36 g and 25.87 ± 3.32 g; respectively to the final body weight in males and females). The gonadosomatic index and hepatosomatic index indicated no significant variation in males while in females, these were significantly low in the experimental fish compared to control fish.ConclusionThe results of this study demonstrated that supplementation of G. kola seeds in diets of young Tilapia improved growth performance and impaired gonadal development in females.

Identification and Function of GnRH-like Peptide in the Pacific Abalone, Haliotis discus hannai.

Gonadotropin-releasing hormone (GnRH) is an important regulator of reproductive function in various vertebrates and invertebrates. In the present study, we have identified the GnRH-like peptide cDNA and peptide from the cerebral ganglion (CG) of the Pacific abalone, Haliotis discus hannai. Pacific abalone GnRH-like peptide (hdhGnRH-like peptide) cDNA encodes precursor, which possesses the typical organization of the known mollusk GnRH-like peptide precursors, including a hydrophobic signal peptide, GnRH-like peptide, and a cleavage site followed by a GAP-like peptide region. Three hdhGnRH-like peptides, pQNYHFSNGWHAamide (hdhGnRH-11amide), pQNYHFSNGWHA (hdhGnRH-11OH), and pQNYHFSNGWHAG (hdhGnRH-12OH), were determined from the acid/acetone extract of the CG by mass spectrometry (LC-MS/MS) analysis. The hdhGnRH-like peptide mRNA expression was detected not only in the CG but also in gonads, and hdhGnRH-11amide was also detected in the extract of gonads. The mRNA expression of hdhGnRH-like peptide in the CG was lower in spawned males than in non-spawned animals, while no change in hdhGnRH-like peptide mRNA expression was shown in both ovulated and non-ovulated abalone. The hdhGnRH-11amide induces spawning and ovulation of both mature males and females in a concentration-dependent fashion following intramuscular injection. These results indicate that three hdhGnRH-like peptides are yielded from a single hdhGnRH-like peptide precursor, and that at least hdhGnRH-11amide is involved in the control of reproduction of the Pacific abalone.

Riverine characteristics and adult demography influence female lake sturgeon (Acipenser fulvescens) spawning behavior, reproductive success, and ovarian quality

Abiotic conditions and demographic factors can influence the timing of spawning. Behavioral plasticity allows females to select spawning conditions that are conducive to offspring development; however, reproductive costs associated with delaying spawning are not well understood. In this study, factors influencing timing of female spawning, residence time (RT), and reproductive success (RS) during two seasons were determined, and plasma testosterone concentrations were used to quantify atretic rates in a wild, lake sturgeon (Acipenser fulvescens) population. For the 123 females monitored, RT ranged from 1 to 23 days and was influenced by arrival date, temperature, discharge, and male number, with the latter having the largest influence. RS varied due to arrival date, temperature, discharge, male number, male length, and operational sex ratio. Two females had testosterone levels indicative of atresia and RS estimates lower than yearly means; however, most females had normal ovaries, suggesting little reproductive costs of plasticity in spawning ground residency time. Results demonstrate the multitude of factors influencing female reproductive behavior and RS, highlighting the importance of abiotic and demographic conditions to recruitment in wild populations.

Effect of sand texture on nest quality and mating success in a fish with parental care

Nest quality is an important aspect of courtship and mate choice, offering females direct benefits through offspring survival and, if it reflects male genetic quality, also indirect ones. Nest characteristics may thus affect both male mating success and reproductive success. Using the sand goby, where males build nests by covering mussel shells or stones in sand, we tested the role of nest material in male nest site choice, nest construction, and female mate choice. We examined the effect of sand texture (coarse or fine, depending on grain size) in two different settings: (A) when the male was free to choose between nest sites in different sand textures and other males were absent, and (B) when the male was denied a choice of sand texture and another male was present behind a partition. In (B), we also examined the effects of sand texture on female preference. In (A), males took up nest sites equally often in coarse and fine sand, but nests built in fine sand had greater sand cover. In (B), there was no difference in nest sand cover, but a greater number of males, and in particular males that weighed less and had been assigned coarse sand, refrained from building a nest at all. This suggests that sand texture does affect nest building in sand gobies, manifesting itself directly through nest sand cover, or indirectly through failure to build a nest. Moreover, we found that females preferred to spawn in well-covered nests regardless of sand texture. Nests offer eggs and offspring protection from predators and inclement weather, but building material may affect both the properties of the nest and the quality of the construction. Here, we presented male sand gobies with nest sites in either fine-grained or coarse-grained sand, assessed the sand cover of the nest, and allowed females to spawn. We found that grain size influenced the amount of sand cover on the nest and affected the fraction of males that refrained from building a nest. Female spawning decision depended on the amount of sand cover, but neither males nor females expressed a preference for sand texture. Our results show that nest material is an important but indirect aspect of mating success, which may influence habitat utilization in the wild.

Continuous but not intermittent noise has a negative impact on mating success in a marine fish with paternal care

Anthropogenic underwater noise is a global pollutant of increasing concern but its impact on reproduction in fish is largely unknown. Hence, a better understanding of its consequences for this important link to fitness is crucial. Working in aquaria, we experimentally tested the impact of broadband noise exposure (added either continuously or intermittently), compared to a control, on the behaviour and reproductive success of the common goby (Pomatoschistus microps), a vocal fish with exclusive paternal care. Compared to the intermittent noise and control treatments, the continuous noise treatment increased latency to female nest inspection and spawning and decreased spawning probability. In contrast, many other female and male pre-spawning behaviours, and female ventilation rate (proxies for stress levels) did not differ among treatments. Therefore, it is likely that female spawning decisions were delayed by a reduced ability to assess male acoustic signals, rather than due to stress per se and that the silent periods in the intermittent noise treatment provided a respite where the females could assess the males. Taken together, we show that noise (of similar frequency range as anthropogenic boat noise) negatively affects reproductive success, particularly under a continuous noise exposure.

Age, Growth, Natural Mortality, and Reproductive Seasonality of Knobbed Porgy from Southeastern United States Waters

AbstractThe Knobbed Porgy Calamus nodosus, an important secondary species in reef fish catches of the southeastern United States, was recently the subject of a fishery closure due to the porgy complex quota being exceeded. Knobbed Porgy (n = 448) were aged using sectioned sagittal otoliths. Opaque zones on otolith sections were annular, forming in March–July (peaking in May). Knobbed Porgy ranged from 1 to 21 years, and the largest fish measured 507 mm TL. Body size relationships relating TL, FL, and total body weight (W) for Knobbed Porgy were TL = 1.07·FL + 22.93 (n = 3,173; r2 = 0.97), FL = 0.91·TL − 12.54 (n = 3,173; r2 = 0.97), W = (1.38 × 10−5)TL3.03 (n = 12,732; r2 = 0.92), and W = (7.99 × 10−5)FL2.79 (n = 3,199; r2 = 0.90). Mean length at age was significantly different between Knobbed Porgy collected in North Carolina through southeast Florida (northern region) and those collected in the Florida Keys (southern region). The von Bertalanffy growth equations for Knobbed Porgy were Lt = 412[1 − e−0.20(t + 1.97)] (n = 448) for all regions combined, Lt = 403[1 − e−0.38(t + 0.0001)] (n = 117) for northern region fish, and Lt = 326[1 − e−0.42(t + 1.61)] (n = 331) for southern region fish. Age‐varying estimates of natural mortality were 0.36–0.79 year−1 (ages 2–21) for the northern region and 0.42–0.67 year−1 (ages 1–12) for fish from the Florida Keys. Hydrated oocytes were present during February–April in macroscopically staged ovaries (n = 148) for fish from the Florida Keys, and gonadosomatic index data indicated that the month of peak spawning in females was April. The updated life history information should be useful to fishery managers in formulating effective management strategies.

Reproductive biology of the invasive sharpbelly, Hemiculter leucisculus (Basilewsky, 1855), from the southern Caspian Sea basin

The sharpbelly, Hemiculter leucisculus , an invasive species, has expanded its range throughout much of Asia and into the Middle East. However, little is known of its reproductive information regarding spawning pattern and season that could possibly explain its success as an invasive species. This research is the first presentation of its reproductive characteristics, which was conducted based on 235 individuals collected monthly throughout a year from Sefid River, in the southern Caspian Sea basin. Age, sex ratio, fecundity, oocytes diameter and gonado-somatic index were calculated. Regression analyses were used to find relations among fecundity and fish size, gonad weight (Wg) and age. The mature males and females were longer than 93.0 and 99.7mm in total length, respectively (+1 in age). The average egg diameter ranged from 0.4mm (April) to 1.1mm (August). Spawning took place in August, when the water temperature was 23 to 26°C. Average gonado-somatic index values for females at the beginning of the reproduction period (March) and in ripe mature spawning females (August) were 2.90% and 16.97%, respectively. The averages of absolute and relative fecundities were 19978.6 and 607.1 eggs, respectively. The absolute fecundity was significantly related to body weight, ovary weight and age. A potentially high reproductive capacity, comparatively small eggs, short time of eggs’ development, fast sexual maturation, short life span, tolerance to a wide range of environmental conditions, all promote the invasion of this invasive sharpbelly in freshwater ecosystems of the temperate climate zone.

Existence of an egg-laying hormone-like peptide in male reproductive system of the giant freshwater prawn, Macrobrachium rosenbergii

The giant freshwater prawn, Macrobrachium rosenbergii, is an important aquaculture species. A better understanding of the molecular components of reproduction in this species would help to advance the prawn production. In the present study, we demonstrated the presence of an egg laying hormone (ELH)-like peptide in the male reproductive system. First, an antibody to the abalone (a)ELH was generated, and by Western blot it was shown to specifically bound to a protein from the male M. rosenbergii reproductive tissues with a similar size to molluscan ELH. This aELH-like peptide was localized in spermatogonia in the testes of all three male morphotypes: blue claw, orange claw and small males. Moreover, the aELH-like peptide was detected in the epithelium of the spermatic duct and its associated smooth muscle cell layers and on the outer surface of spermatozoa. As well, the aELH-like peptide was detected in the spermatophore located in the female thelycum at 4–6 h post-mating, indicating that it was transferred to the female during copulation. Taken together, we suggest that this aELH-like peptide could be as a male inducing factor that helped to accelerate female spawning. Liquid chromatography of crude extracts and immunoblot analysis suggested that the aELH-like peptide could be further purified for ultimate characterization.

The Characteristics of the Amur Sturgeon, Acipenser schrenckii, Spawners from a Warm-Water Cage Farm during Long-Term Exploitation

The cultivation, biological, and production parameters of domesticated Amur sturgeon spawners of age 8 to 24 years from a warm-water cage farm are described. Female Amur sturgeons of three generations, bred from native spawners in cages, reach first maturity at ages of 8–10 years; males reach first maturity at ages of 6–7 years. Females have a larger body weight, length, girth, and fatness than those of males in all the age groups from 8 to 24 years. Males produce 40–350 mL of high-quality milt per one stripping session; first-maturing females produce 0.7–2.3 kg of roe. Most females (75%) spawn annually or biennially. Some females at ages of 17–23 years can produce a maximum of 7.0–10.5 kg of roe. The mean amount of roe collected from one female at ages of 8–24 is 3.82 kg, with a fecundity of 200 000 eggs (a maximum of 520 000 eggs), a relative working fecundity of 7500 eggs/kg (maximum 13 500 eggs/kg), and an oosomatic index of 14.5% (maximum 24.5%). During six to eight spawning seasons, an average of 22–31 kg of roe was obtained from the females of age 21 and 24 years, which accounts for 90–98% of their body weight. In 27% of the females, the amount of roe was 29–43 kg, or 103.0–137.5% of their body weight. The females adapt well to technological operations. Their survival rate for the period of exploitation is 65%.

The sunray venus clam, Macrocallista nimbosa, exhibits asynchronous spawning

The reproductive cycle of the sunray venus (SRV) clam, Macrocallista nimbosa, was initially described over 40 years ago and was labeled as a “fall spawner” based on that study. Interest in the SRV clam as an alternative bivalve species for Florida shellfish aquaculture was established a decade ago but due to it’s reputation as an unreliable spawner, production of this clam has stalled. This study was conducted to provide a more thorough description of the reproductive cycle, including detail-oriented reproductive staging in an effort to determine the cause of reported spawning difficulties. Regardless of sex, M. nimbosa follicles were observed to be continual spawners. It was not uncommon to observe follicles in four of the six gametogenic stages simultaneously. Spawning was generally protracted with no long period of inactivity. A single hermaphrodite suggested possibility of protandry. Although spawning and gametogenesis were continuous, bimodal spawning peaks were seen; however, these peaks occurred asynchronously. These observations lend credence to reports of unreliable spawning and limited egg production during thermal induction. Continuously collected environmental data indicated that spawning in females followed increased turbidity (used as a phytoplankton proxy). This observed increase in spawning in females reiterates the role of diet in gametogenic production. It may be necessary to adjust currently established hard clam feeding practices during maturation in order to increase egg production and optimize spawning potential in this species. Further research into the optimization of temperature, concentration and types of microalgal species fed during maturation is suggested.

Triggers of spawning and oocyte maturation in the commercial sea cucumber Cucumaria frondosa

The present study investigated methods to trigger spawning and artificially induce oocyte maturation in the commercial cold-water suspension-feeding sea cucumber Cucumaria frondosa. Spawning occurred after exposure to live phytoplankton, commercial phytoplankton paste, and conspecific sperm. Live phytoplankton at 1 × 105 cells ml−1 induced the highest proportion of females to spawn (mean of 56%); promoted the greatest oocyte release (mean of 19,200 oocytes female−1), best quality of eggs and highest survival of embryos (65%; 20 d post fertilization). More concentrated live phytoplankton (1 × 106 cells ml−1) triggered 43% of the females to release ~16,100 oocytes female−1 and survival rates 20 d post fertilization were lower (50%). Both phytoplankton paste treatments (1 × 105 and 1 × 106 cells ml−1) yielded intermediate results in terms of percent spawning females (26%), abundance of oocytes released (11,000 and 7300 oocytes female−1, respectively), quality of eggs, and survival of embryos (44 and 50%, respectively). Sperm from conspecific (2 and 10 × 106 spermatozoa ml−1) induced the lowest proportion of females to spawn (16%) with release of 3000 and 1700 oocytes female−1, respectively; furthermore, all embryos died within 10 d post fertilization. Results for males were slightly different: spawning was more frequent (63%) in the sperm treatment at 2 × 106 spermatozoa ml−1 followed by live phytoplankton at 1 × 106 and 1 × 105 cells ml−1 (43%), and phytoplankton paste at 1 × 105 cells ml−1 (46%); the lowest spawning success was observed for phytoplankton paste at 1 × 106 cells ml−1 and conspecific sperm at 10 × 106 spermatozoa ml−1 (26%). Thermal shock, desiccation, potassium chloride (injection or bath), and serotonin (injection) did not induce spawning in C. frondosa. When oocytes isolated from mature ovaries were exposed to three different concentrations of 1-Methyladenine (1-MA), Dithiothreitol (DTT), 2,3-Dimercapto-1-propanol (BAL), and L-cysteine (L-cyst), DTT at 10−1 M induced the highest proportion of oocytes (48%) to shed follicle cells (i.e. ovulate); whereas other treatments induced only 2–6% of ovulation, similar to the control (seawater). All oocytes that shed follicle cells remained unfertilizable. Overall, live phytoplankton emerged as the most suitable spawning trigger for C. frondosa, a Dendrochirotida that produces maternally-provisioned oocytes. In the context of expanding sea cucumber aquaculture, this finding provides a tool to maximize the availability of gametes in this cold-water species, with possible applicability to similar commercial dendrochitotids.