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The influence of temperature on sex determination has been reported previously on many crustaceans. The interpretability of temperature capability to regulate the steroidogenic pathway, which in turn governs the offspring sex of mud crab, still remains unclear. Thus, the aim was to determine the effects of temperature on sex percentage and steroidal pathway in purple mud crab, Scylla tranquebarica. In sex percentage analysis, the eggs (28°C and 30°C), larvae (28°C, 30°C and 32°C) and juveniles (26°C, 28°C, 30°C) were exposed to different temperatures. The results revealed that exposure to a higher temperature during larvae (32°C) and juvenile (30°C) stages probably initiated the maleness (58.7%) and femaleness (60.8%) mechanism respectively. In steroid hormone analysis, the eggs (26°C, 28°C, 30°C and 32°C), larvae (29°C, 30°C, 31°C and 32°C) and juveniles (26°C, 28°C, 30°C and 32°C) were exposed to different temperatures. The steroidal assay corroborated the results of the sex percentages, which found higher dihydrotestosterone (172.4 pg/g) and testosterone (580.2 pg/g) levels when the larvae were incubated at a higher temperature (32°C) while higher estrone (136.9 pg/g) and estradiol (540.7 pg/g) levels when the juveniles were reared at high temperature (30°C). In brief, the temperature plays a significant role to redirect the mud crab sex during the larval and juvenile stages. [ABSTRACT FROM AUTHOR]

Interest in the production of crustacean aquaculture has focussed primarily on mud crab species; however, mud crab production still relies on wild‐caught juveniles due to the low production of viable seeds of mud crab. Thus, the aim of this study was to enhance mass propagation of purple mud crab seed by studying the relation of temperature on growth performance of the early life stage of purple mud crab. Several data such as survival, incubation duration and morphometric measurements were evaluated after temperature was exposed on the egg, larval and crablet stages. For the egg stage, high hatching success (78.95% and 75.00%) was noted within a limited temperature range (28°C and 30°C respectively). Also, significant increment of final egg diameter (0.33 ± 0.05 mm) after the berried crab incubated at 30℃. For larval stage, the highest survival rate was found when the larvae were reared at 30℃ and 31°C with 68.79 ± 2.69 and 66.98 ± 2.63% respectively. The largest morphometric measurements for megalopa (CW: 2.80 ± 0.15 mm) and C1 (CW: 2.86 ± 0.12 mm) were observed at 31℃. The yielded total juvenile at the end of the larval experiment indicated the highest production was obtained for temperature 31°C (1,095 ± 47.3 individuals) followed by 30°C (1,002 ± 84.7 individuals). For the crablet stage, the crablets were able to survive in a wide range of temperatures (26°C–32°C) with >95% survival; however, the temperature 26℃–29°C indicated larger morphometric measurements (CW: 6.24–6.39 mm). In brief, the optimal temperature for egg, larval and crablet stages was recommended within 28℃–30℃, 30℃–31℃ and 26℃–29℃ respectively. [ABSTRACT FROM AUTHOR]

Keywords: egg; juvenile; larva; mud crab; temperature EN egg juvenile larva mud crab temperature 707 713 7 01/07/22 20220201 NES 220201 INTRODUCTION A series of morphological variations started in early juvenile as an adaptability process to ensure the capability of mating and reproducing during adulthood (Parvizi et al., 2017). If sexual dimorphism occurred, the line between male and female is widening with the course of juvenile growth gl Copulatory organs, chelae, and abdomen can be used to differentiate between male and female juveniles. The traits of large chela in male crabs are considered to be evolved due to intra-sexual selection, in which the male crabs fight aggressively to access the female crabs (Yoshino et al., 2011). Most findings of brachyuran crabs applied the abdominal width as secondary characters to define the sexual maturity of female crabs (Waiho et al., 2016a; 2016b). [Extracted from the article]

Pinfish ( Lagodon rhomboides Linnaeus) and pigfish ( Orthopristis chrysoptera L.) are relatively new, cultured species commonly used as marine baitfish in the south-eastern United States and currently have no defined protocols for egg incubation. Thus, experiments were conducted to determine efficient egg stocking densities during static and flow-through incubation that yielded higher quality larvae. Eggs of each species were incubated statically at 250, 500, 1000 and 2000 eggs L−1, and after incubation, egg hatching success, larval survival to first feeding, larval morphometrics and water quality were assessed. Stocking densities above 250 eggs L−1 led to significant reductions in pinfish hatching success and water quality degradation, evident from decreased dissolved oxygen and pH levels and increased nitrogenous wastes. Increased stocking densities for pigfish also resulted in significant water quality degradation, although hatching success was unaffected up to a density of 1000 eggs L−1. A high flow-through water exchange rate of 2000% daily resulted in significant reductions in nitrogenous wastes and greater stability in dissolved oxygen and pH levels during incubation when compared to static treatments of the same egg density. Additionally, the high exchange rate of 2000% was critical in maintaining high hatching success and larval survival to first feeding at stocking densities of 1000 eggs L−1 for pinfish and up to 4000 eggs L−1 for pigfish. No clear patterns in larval morphometrics were observed among stocking densities. Static incubation densities of 250 and 1000 eggs L−1 are recommended for pinfish and pigfish, respectively. [ABSTRACT FROM AUTHOR]

The ability of domesticated Penaeus monodon, Black Tiger shrimp, to spawn following tail-muscle injection of ds RNA was examined. Ablated domesticated female broodstock infected subclinically with gill-associated virus ( GAV) were injected with saline or a cocktail of five-ds RNAs targeting different regions in the GAV ORF1a/1b gene. To track changes in GAV infection loads, TaqMan real-time PCR was used to quantify mean viral RNA amounts in each of three pleopod clips collected at the time of injection (Day 0) and either immediately after a female spawned or on Day 11 when the trial was terminated. Over the trial, 4 of 19 (21%) saline-injected shrimp spawned and 12 of 25 (48%) ds RNA-injected shrimp spawned, with one spawning twice. Egg numbers varied from 25 600 to 459 800 for the saline-injected shrimp and from 4900 to 213 900 for the ds RNA-injected shrimp. Of these, one of the four egg batches hatched from saline-injected shrimp and 9 of the 13 egg batches hatched from ds RNA-injected shrimp. While variable, egg numbers and hatch rates recorded were typical of those obtained from domesticated broodstock at the commercial hatchery and particularly among females previously spawned. Mean GAV RNA amounts detected in pleopod samples increased in five of the eight saline-injected shrimp tested by 1.6-227.4-fold and decreased in 12 of the 15 ds- RNA-injected shrimp tested by −1.1 to −45.1-fold. The study demonstrated that tail-muscle injection of GAV-specific ds RNA does not adversely impact the ability of P. monodon to spawn. [ABSTRACT FROM AUTHOR]

In recent years, crayfish aquaculture industry has been developing rapidly in different regions of the world. Crayfish aquaculture is often carried out in dams, lakes and extensive pond systems. There is an increasing demand for crayfish juvenile in aquaculture sector. Therefore, it is important to know which factors affect reproductive efficiency in crayfish. In the present review, factors affecting the reproductive efficiency of crayfish are divided into two main sections, external and internal factors. Dietary lipids, phospholipids, highly unsaturated fatty acids, protein and amino acids, vitamins and carotenoids are important external factors affecting broodstock crayfish reproduction. In addition, various external (i.e. female size, stocking density, temperature, photoperiod, sex ratio) and internal (i.e. endogenous hormones) factors affect the reproductive efficiency in crayfish. This study reviews the present knowledge with the purpose of realizing the factors that are important to reach optimal crayfish nutrition, maturation and reproduction (i.e. pleopodal egg number and quality). This review will particularly be useful for crayfish farmers and crayfish hatchery units. [ABSTRACT FROM AUTHOR]

Bacterial communities in eggs and larvae of grass carp were analysed. During the early-developmental stages, grass carp harboured five bacterial phyla, i.e. Proteobacteria, Bacteroidetes, Verrucomicrobia, Planctomycetes and Firmicutes. However, the composition of bacterial communities varied among the different developmental stages. In eggs, the bacterial communities were dominated by Proteobacteria, while in larvae the dominant bacterial community was Bacterioidetes. With the exception of a large proportion (>50%) of uncultured bacteria, Sphingobacterium (14.75%) and Acinetobacter (13.11%) were the most abundant groups in eggs at the fertilization stage ( FS). However, Aermonas was the most abundant group, ranging from 40.54% to 61.76% in eggs at the cleavage ( CS), blastula ( BS), organ differentiation ( ODS) and hatching stages ( HS). In larvae after first ingestion ( OW), Chitinophagaceae (79.41%) formed the predominant bacterial community. Changes in the bacterial community were further confirmed by statistical analysis, which demonstrated significant differences in the bacterial communities of eggs at FS, eggs from CS to HS and OW. However, no significant difference was found in bacterial communities of eggs from CS to HS. Furthermore, the present study revealed that bacteria related to Chitinophagaceae persisted from CS to OW, suggesting that these bacteria form part of the autochthonous microbiota of the fish. [ABSTRACT FROM AUTHOR]

Brill ( Scophthalmus rhombus L.) is a flatfish considered of special interest for aquaculture diversification, but the high mortality observed during the early larval rearing is the main obstacle to commercial culture. The objective of this study was to contribute to the knowledge of nutrient utilization of early-hatched larvae, characterizing the changes in lipid and protein contents during embryogenesis and the yolk-sac larval stage of S. rhombus. Total lipid, lipid classes and fatty acid contents remained constant during embryogenesis and yolk-sac larval development, except for phosphatidylethanolamine and phosphatidylinositol, which increased in quantity during the yolk-sac larval stage. On the other hand, total protein (including non-protein nitrogen) and amino acids decreased their contents in both periods, especially at hatching. The decrease only in the serine, glutamic acid, proline and lysine contents during embryogenesis suggests a selective use of amino acids during this phase. Unlike embryogenesis, amino acids loss during hatching appears to be non-selective, and almost all amino acids (essential and non-essential) decreased. Our results suggest that there is higher catabolism of protein vs. lipid during embryogenesis and the yolk-sac larval stage of S. rhombus. [ABSTRACT FROM AUTHOR]

Both egg and larvae are different between freshwater and marine fish species. Freshwater fish species have generally larger and fewer eggs than marine species. Most freshwater fish species have demersal eggs that develop stuck to various substrata, such as plants or gravels, while eggs of most marine fish species develop in the water column. These differences have consequences for both the evaluation of the quality and the incubation of eggs of freshwater fish species compared with marine species. The larvae of many freshwater fish species are larger and more developed at hatching than their marine counterparts: thus, larval feeding regimes could be different and cannibalism may emerge sooner in certain freshwater fish species. The main differences of egg and larvae between freshwater and marine species are highlighted and the possible implications for aquaculture practices are discussed. [ABSTRACT FROM AUTHOR]

Eggs of seven females were sampled to analyse the lipid, protein and carbohydrate content during the embryonic development of the prawn Macrobrachium americanum. Sampling was performed from recently spawned eggs to hatching. A hundred of eggs were sampled every 48 h during the trial. Proteins, lipids and carbohydrates were quantified. Proteins were the most abundant component, followed by lipids and carbohydrates as only minor constituents. Lipid decreased significantly from 42% to 23% of the total composition, while proteins increased from 55% to 76% and carbohydrates varied inconsistently. The change in total energy per egg through time during the embryonic development is represented by the equation y=−0.0133 x+0.334; r2=0.94 ( y represents the energy content and x represents days). The main energy provider was lipids whose energy consumption is described by the equation y=−0.0158 x+0.203; r2=0.96. [ABSTRACT FROM AUTHOR]

The effects of exposing the eggs of Pacific threadfin and amberjack eggs (AEs) to different concentrations of hydrogen peroxide for 5 min on hatch rate and survival were assessed in a series of experiments using a petri dish model rearing system. Despite significant inter-batch variation in hatch rate, it was shown that eggs of both species could be safely exposed to up to 11 340 mg L−1 H2O2 for 5 min. Exposure to 34 230 mg L−1 H2O2 for 5 min was shown to be lethal to AEs at a late stage of development. In two further experiments, it was demonstrated that Pacific threadfin eggs were resistant to all tested concentrations of a range of polyvinylpyrrolidone iodine (PVP-I) concentrations and contact times (up to 1000 mg L−1 PVP-I for 10 min). The level of bacteria adhering to the eggs of both species was highly variable. Where eggs were heavily colonized (>104 cfu egg−1), hydrogen peroxide concentrations of at least 11 340 mg L−1, or PVP-I concentrations higher than 500 mg L−1 for 10 min, were required for effective sterilization. In less colonized batches, rinsing in sterile seawater or exposure to lower (550 mg L−1) concentrations of H2O2 was sufficient to result in high apparent levels of surface sterility (<1 cfu egg−1). [ABSTRACT FROM AUTHOR]

Unfertilized eggs of steelhead, Oncorhynchus mykiss (Walbaum 1792), were stored at a low temperature (∼0°C) with antibiotics (penicillin and streptomycin) for up to 22 days and fertility assessed. Unfertilized eggs of chinook salmon, Oncorhynchus tshawytscha (Walbaum 1792), were stored at a low temperature (∼0°C) either with or without antibiotics for up to 24 days and fertility assessed. There were no significant decreases in fertility under these conditions. Steelhead eggs were maintained at 4°C for up to 15 days with or without added bacteria and with or without gentamicin. Gentamicin inhibited bacterial growth during storage at 4°C and its use resulted in a less pronounced decline in fertility with storage. These results suggest that low temperatures and antibiotics play an important role in extending the period over which salmonid eggs can be successfully stored. [ABSTRACT FROM AUTHOR]

Loligo vulgaris is a commercially important squid throughout the Mediterranean region and is a candidate species in biomedical and aquaculture research. Some loligo species ( L. opalescens, L. forbesi, Sepiteuthis lessoniana) have now been cultured through some successive generations in closed, recirculating seawater systems. The effects of salinity on hatching European Squid ( L. vulgaris Lamarck, 1798) eggs were investigated during November 2004. The egg capsules were incubated directly in salinity of 32, 34, 36, 38, 40, 42 and 37 g L−1 (control group) at 19.8°C (SD 1.2°C), and a photoperiodicity of 12 h light:12 h dark for 16–23 days before hatching. In all treatments, the eggs were developed and hatched normally after 16–22 days at 32 g L−1, 17–22 days at 34, 18–21 days at 42 g L−1, 18–22 days at 36 and 40 g L−1, 19–22 days at 37 g L−1 and 19–23 h at 38 g L−1. In the experiments, the highest hatching rate and hatching success (HS) of the eggs were obtained at 38 g L−1 (hatching rate: 100% (SD 0%) and HS: 96.7% (SD 3.5%)) and the lowest hatching rate at 42 g L−1 (hatching rate: 3% (SD 6%) and HS: 0%). Dorsal mantle lengths (DML) of new hatchlings ranged from 2.08 to 2.80 mm. The present study showed that salinity affects the hatching rate and HS of eggs and first hatching time and DML of paralarvae in L. vulgaris. The squid eggs at stage 11 (I) can tolerate 5 g L−1 reduction and 3 g L−1 increase in salinity. [ABSTRACT FROM AUTHOR]

Embryonic development of common dentex ( Dentex dentex) was investigated at nine different constant water temperatures (8°C, 10°C, 12°C, 14°C, 16°C, 18°C, 20°C, 22°C and 24°C). The observed effects were compared using of regression analysis. Constant water temperatures between 12°C and 18°C were found to support successful embryonic development. A negative relationship between the rate of embryonic development and incubation temperature was observed. While embryonic development was completed within this range (12°C–18°C), there was no cell division at water temperatures of 8°C and 24°C. Total mortalities were observed at the 128 cleavage stage at a temperature of 10°C, and after the beginning of gastrulation at 20°C and 22°C. [ABSTRACT FROM AUTHOR]

Abstract The effects of temperature and salinity on the reproductive success of Arctic charr, Salvelinus alpinus (L.), were examined by holding broodstock under the following conditions from mid-May until the end of September: fresh water at ambient temperature (NFW; 8–16 °C); salt water (25–30‰) at ambient temperature (NSW; 4–10 °C); fresh water cooled to saltwater temperature (CFW; 4–10 °C); or salt water heated to freshwater temperature (HSW; 8–16 °C). The relative fecundity of females was similar among groups (P > 0.05; 2685 ± 706 eggs), but females reared in NSW produced significantly larger eggs than those raised in NFW. The highest spermatozoa concentrations were found in milt from males reared in SW and the highest milt glucose concentration was from males kept under coldwater conditions (CFW, NSW). Eggs from NSW and HSW females contained more proteins than eggs produced by NFW females. Eggs from NSW females also contained 40% more lipids than was observed in the other groups, and total energy content was 27% higher in eggs from NSW females than in eggs from NFW females. When FW was cooled (CFW), females produced eggs with protein contents similar to those in NSW, but the lipid contents remained 30% lower. Finally, the best survival at the eyed stage and at hatch was observed in families produced by NSW broodstock. Intermediate values were observed in families from NFW or CFW while the highest mortality occurred in families from the HSW group. All these results suggest that, under the experimental conditions used in the present study, coastal seawater conditions offered the most favourable summer rearing conditions with respect to the reproductive success of Arctic charr. [ABSTRACT FROM AUTHOR]