Hatching Of Larvae Research Articles

Transcriptional Rearrangements Associated with Thermal Stress and Preadaptation in Baikal Whitefish (Coregonus baicalensis).

In this work, we describe the transcriptional profiles of preadapted and non-adapted one-month-old juvenile Baikal whitefish after heat shock exposure. Preadapted fish were exposed to a repeated thermal rise of 6 °C above the control temperature every three days throughout their embryonic development. One month after hatching, preadapted and non-adapted larvae were either kept at control temperatures (12 °C) or exposed to an acute thermal stress (TS) of 12 °C above the control temperature. In response to this acute stress, an increase in HSP gene expression (HSP-30, HSP-40, HSP-47, HSP-70, and HSP-90) and TRIM16 was detected, independent of preadaptation. The expression levels of genes responsible for the response to oxygen levels, growth factors and the immune response, HBA, HBB, Myosin VI, Myosin VII, MHC, Plumieribetin, TnI, CYP450, and LDB3 were higher in individuals that had previously undergone adaptation. Genes responsible for the regulation of metabolism, MtCK, aFGF, ARF, CRYGB, and D-DT, however, increased their activity in non-adapted individuals. This information on transcriptional profiles will contribute to further understanding of the mechanisms of adaptation of whitefish to their environment.

Embryonic and larval development of black jewfish, Protonibea diacanthus: A new candidate for aquaculture in northern Australia

Black jewfish Protonibea diacanthus is a large, commercially important fish distributed across the tropical Indo-Pacific. In Australia, there is an established commercial wild fishery for the species but it’s aquaculture potential has not been investigated. This research presents hatchery production of native P. diacanthus in Darwin, Australia and documents ontogeny of early life stages of this species over three trial runs. Wild P. diacanthus were induced to spawn with luteinizing hormone-releasing hormone analog (LHRHa) and eggs were released approximately 25–28 h after injection (0.88 ± 0.01 mm in diameter with oil globule 0.24 ± 0.01 mm). Larvae hatched 12 h after spawning. At one day post hatch (dph) larvae were 2.68 ± 0.01 mm standard length with 0.15 ± 0.01 mm oil globule diameter. Larvae mouths opened at 31 h post hatch (hph) and first feeding was seen at 57 hph. Swim bladder inflation (92 %) occurred between 40 and 62 hph. Larvae were progressively fed rotifers, Artemia and Otohime microdiet, and metamorphosis occurred between 20 and 25 dph, completing as they reached over 13 mm standard length. Tail biting cannibalism began with the onset of metamorphosis and caused significant mortality until approximately 24 dph when metamorphosed juveniles could be handled and moved to low stocking density systems. This study demonstrates that northern Australian P. diacanthus is amenable to hatchery production and provides important foundational knowledge for this emerging aquaculture species.

Effects of different temperatures on the embryonic development of the Lebranche mullet Mugil liza.

We herein investigated the influence of temperature on theembryonic development (from fertilisation to hatching) of Mugil liza larvae. For this purpose, oocytes (>600 μm) and sperm were obtained from breeding stock at the laboratory of marine fish culture (LAPMAR). After fertilisation, 1200 eggs were distributed in 12 cylindrical experimental units of 400 mL under four different temperatures 18, 22, 26 and 30 ºC, all in triplicate. Every 15 min until hatching, about 10 eggs were randomly sampled in each treatment. The eggs were visualized and photographed, and the classification of embryonic stages was performed. Temperature influenced the main events of the embryonic development of M. liza. More accelerated development was observed according to the increase in temperature until the gastrula phase. At temperatures of 22 and 26 °C, embryonic development occurred from fertilisation to hatching of the larvae. In the 18 °C treatment, it was verified that most of the embryos ceased development during the final phase of cleavage and the beginning of blastula formation, while in the 30 °C treatment patterns of embryo malformation were also verified, with erratic divisions of the blastomeres, resulting in irregular cells. Unlike what was observed at a temperature of 18 °C, none of the embryos incubated at 30 °C reached the blastopore closure phase, stopping in the gastrula. The larvae hatched in the treatments at 22 and 26 °C were viable and exhibited intense swimming, with a large amount of reserve material (yolk) and an evident drop of oil.

The Effect of Two Types of Pesticides, Chemocis ULV and Chemocis D, on the Development, and Hatching of Eggs and Larvae of Common Carp Cyprinus carpio (L.)

The Effect of Two Types of Pesticides, Chemocis ULV and Chemocis D, on the Development, and Hatching of Eggs and Larvae of Common Carp Cyprinus carpio (L.)

Embryonic death as a probable reason for the collapse of population densities in Lymantria dispar (Linnaeus, 1758) (Lepidoptera: Erebidae, Lymantriinae)

For the first time the causes of mass death of embryos in a population of Lymantria dispar (Linnaeus, 1758) with biochemical and molecular methods are investigated. In this study egg masses were collected in the territory of Russia from two populations, with low (the West Siberian population) and high (Trans-Ural) density and analyzed. Spring hatching of larvae from the eggs stored under constant laboratory conditions at 2º C was two times lower for insects of the Trans-Ural (TU) population compared to the West Siberian (WS) population (43 ± 6 % and 86 ± 7 % accordingly). The level of virus defined by PCR for TU and WS populations was 76±9 % and 36±6%, respectively. The major components of eggs were the same between populations. However, we found decreased concentrations of proteins important for embryogenesis in TU population, such as an arilforin-like molecule and no vitellin 2-like component. Field data were comparable to those of the laboratory, and in TU populations there was a decrease of density. The obtained results suggest that alteration in hormonal balance of the infected with nucleopolyhedrovirus (NPV) insects may lead to a decrease or absence of some key proteins of embryogenesis in eggs. It can influence hatching of larvae from eggs and, accordingly, population dynamics of the lepidopteran.

Climate‐influenced phenology of larval fish transport in a large lake

AbstractElucidating physical transport phenologies in large lakes can aid understanding of larval recruitment dynamics. Here, we integrate a series of climate, hydrodynamic, biogeochemical, and Lagrangian particle dispersion models to: (1) simulate hatch and transport of fish larvae throughout an illustrative large lake, (2) evaluate patterns of historic and potential future climate‐induced larval transport, and (3) consider consequences for overlap with suitable temperatures and prey. Simulations demonstrate that relative offshore transport increases seasonally, with shifts toward offshore transport occurring earlier during relatively warm historic and future simulations. Intra‐ and inter‐annual trends in transport were robust to assumed pelagic larval duration and precise location and timing of hatching. Larvae retained nearshore generally encountered more favorable temperatures and zooplankton densities compared to larvae transported offshore. Larval exploitation of nearshore resources under climate change may depend on a concomitant shift to earlier spawning and hatch times in advance of earlier offshore transport.

Analysis of survival and morphometric parameters of loach embryos and prelarvae under the action of the polyethyleneglycol derivative polymeric nanocarrier

Background. Our previous studies have shown a minor embryotoxic effect of polymeric poly(VEP-co-GMA)-graft-mPEG carrier on Missgurnus fossilis L. embryos and prelarvae. At the same time, it was found that a 3-day exposure to 10-15 M polymer carrier slowed developing, which is characterized by a delayed hatching of larvae. However, in the 10-day experiment on loach larvae exposed to polymeric carrier, anomalies and defects of development have not been identified. The aim of this work was to analyze the embryos and prelarvae survival, as well as determine the morphometric indicators of the loach embryos under the action of a PEG-modified polymer carrier. Materials and Methods. Ovulation in loach females (Misgurnus fossilis L.) was stimulated by intramuscular injection of female chorionic gonadotropin (500 units), eggs were obtained 36 h after stimulation, fertilized in Petri dishes with a suspension of sperm according to A. A. Neifach. The stages of development were observed visually under a binocular microscope MBS-9 with a photo camera in a real-time mode. The experimental embryos were incubated in Goltfreter’s solution with the addition of PEG-containing carrier to a final concentration of 10 and 100 μmol/L. The morphological development of the embryo groups was evaluated according to the T. Fujimoto deve­lopment tables (2004), and the morphological parameters (diameter and area of roes, blastomers, embryos, embryo sac and blastodisk) were measured using ImageJ and Photoshop (CC 2014v15) programs. Results. Addition of the 10 μmol/L PEG-containing carrier to the medium initiated significant positive changes in the survival of loach embryos and prelarvae, in contrast to exposure to 100 μmol/L carrier. A significant increase in the area and diameter of blastomers and the embryos themselves under the influence of 100 μmol/L PEG carrier was established, which may indicate swelling of the embryos and a disruption of water-salt exchange that causes the early death of embryos. Conclusions. (1) Low embryotoxicity of the PEG-polymer was confirmed on the studied model of the loach embryos. Based on the obtained data and the original data of J. Maes et al. (2) PEG is an attractive polymeric carrier for the delivery of a variety of compounds to both embryos and prelarvae as well as other model subjects. Despite the fact that we investigated only two concentrations of the PEG-containing carrier, it is quite likely that these concentrations of the carrier are (3) biologically active in themselves and, therefore, a thorough selection of the PEG-carrier concentration for each objective of the model is needed.

Oocyte size, early development and hybridisation in two sympatric Chilean species of Fissurella (Mollusca: Vetigastropoda) under laboratory conditions

ABSTRACT Fissurella latimarginata and Fissurella cumingi are two sympatric species found along the southwestern coast of South America. We conducted a comparative analysis of oocyte size and their coats between these species and investigated early development using chemically activated gametes. Additionally, heterologous fertilizations were conducted to assess the presence of a reproductive isolation barrier between the species. The mean diameter of the oocyte and gelatinous coat did not show significant differences between species, but there were differences regarding the vitelline coat. However, the practical utility of this trait as taxonomic character for species discrimination is hindered by variance overlap. Chemical activation of gametes enabled homologous fertilizations, resulting in the production of healthy and viable trochophore larvae. Early development, from fertilisation to hatch of these larvae, takes 28.5–45.5 h in both species. Heterologous fertilizations were also successful, resulting in the hatching of trochophore hybrid larvae, indicating effective interactions between the gametes of both species and viable postzygotic larval development. However, further research should focus on determining if there is asymmetry in gametic compatibility, obtaining veliger larvae, or even more advanced ontogenetic stages.

Diverging phenology of American lobster (Homarus americanus) larvae and their zooplankton prey in a warming ocean

Abstract We build on previous research describing correlative links between changes in the abundance of the copepod Calanus finmarchicus, a foundational zooplankton species of the pelagic food web, and diminishing recruitment of young-of-year American lobster (Homarus americanus) to benthic nurseries in the Gulf of Maine. Using parallel 31-year time series of lobster larvae and zooplankton collected on the New Hampshire coast between 1988 and 2018, we investigated how changes in phenology of stage I larval lobster and their putative copepod prey, C. finmarchicus, affect their temporal overlap and potential to interact during the larval season. We found that over the time series both the lobster egg hatch and first appearance of larvae began earlier in the season, a trend significantly correlated with ocean warming. The last appearance of larvae in late summer has been delayed, however, thereby extending the larval season. Even with the longer larval lobster season, the C. finmarchicus season has increasingly been ending before the peak abundance of stage I lobster larvae. The net effect is a widening mismatch in phenology of the two species, an outcome consistent with the hypothesis that changes in abundance and phenology of C. finmarchicus have contributed to recent declines in lobster recruitment.

Review of the distribution, population trends, threats, and conservation options for the endangered Zambezi flapshell turtles (<i>Cycloderma frenatum</i> Peters, 1854) in range states

The endangered Zambezi flapshell turtle, Cycloderma frenatum Peters, 1854, is endemic to southern and eastern Africa. Habitat ecology and usage are not well known for the Zambezi flapshell turtle, although its population has been reported to have undergone massive declines in recent years. This review examined the i) population trends, ii) habitat range shifts, and iii) threats and conservation options for the Zambezi flapshell turtle in its range states. The species is data deficient because of a lack of assessments of trends in population size and distribution. Trafficking, overfishing, poaching, habitat degradation, and infrastructural developments in riparian zones affect the distribution of the Zambezi flapshell turtle. Conservation options such as deterrent punishments and protection of aquatic habitats are important, although they need to be consistently implemented. Carefully managed harvest plans supported by captive breeding, highly controlled incubation of eggs, hatching of larvae, and remotely sensed tracing of specimens to curb trafficking are potentially effective conservation options for the Zambezi flapshell turtle. Inclusion in international wildlife trade regulations, integration of local ecological knowledge into management, and development of connectivity conservation strategies are priority actions for sustaining the Zambezi flapshell turtle populations across the shared basins where it is endemic.

Ginsenoside Rg1 modulates PI3K/AKT pathway for enhanced osteogenesis via GPER

BackgroundOsteoporosis is a systemic skeletal disorder characterized by decreased bone density and the degradation of bone tissue microarchitecture. Ginsenoside Rg1, derived from Panax ginseng, has been a part of traditional Chinese medicine in China for centuries, particularly for treating osteoporosis. However, there remains limited research on the osteogenic potential of Rg1 within the glucocorticoid-induced osteoporosis (GIOP) model and its specific mechanisms. PurposeThe primary objective of this study is to investigate the osteogenic potential of Rg1 within the GIOP model and explore the signaling pathways associated with its in vivo and in vitro effects. MethodsCell proliferation, differentiation and mineralization were evaluated by the Cell counting kit 8(CCK8) assay, alkaline phosphatase (ALP) test and Alizarin Red S staining, respectively. The qPCR technique was used to determine the relative expression of mRNA and the western blot was used to determine the relative expression of protein. In vivo experiments, spinal vertebrae staining in zebrafish larvae was accomplished by alizarin red S staining. ResultsZebrafish larvae's hatching, survival, malformation, and heart rate were unaffected by 50 μM of Rg1 in vivo, while the MEC3T3-E1 cell line's proliferation was unaffected by 50 μM of Rg1 in vitro. Meanwhile, Rg1 was shown to improve osteogenic differentiation or bone formation as well as the level of mRNA expression of osteogenic markers in vivo and in vitro. Treatment with Rg1 significantly increased the expression of G protein-coupled estrogen receptor (GPER) and pAKT. In addition, the GPER inhibitor G15 could significantly reduce the mRNA and protein expression levels of GPER and phosphorylated AKT, LY294002, a PI3K/AKT pathway inhibitor, markedly suppresses the expression of phosphorylated AKT, yet shows no significant impact on GPER expression. Both G15 and LY294002 can significantly blocked the Rg1-mediated enhancement of osteogenesis capacity in the GIOP model. In contrast, when both the agonists G1 of GPER and LY294002 were added, G1 increased the relative expression of mRNA and protein of GPER, but not the expression of osteogenic capacity and osteogenic markers. ConclusionsThis study investigates the mineralization effects and mechanisms of Ginsenoside Rg1 both in vitro and in vivo. For the first time, we propose that Rg1 might regulate osteogenesis by modulating AKT phosphorylation through mediating GPER expression within the PI3K/AKT pathway in the GIOP model. This discovery introduces novel targets and avenues for osteoporosis treatment.

The Cortisol Levels, Histology, and Fine Structure of Various Tissues of Fish Gambusia affinis (Baird and Girard, 1853) after Exposure to Lead.

Aquatic organisms demonstrate a high vulnerability to mortality when exposed to Pb, even at low concentrations. The objective of this investigation is to ascertain the histopathological alterations and cortisol concentrations in diverse tissues of Gambusia affinis, with a specific focus on the eggs and larvae, following exposure to varying concentrations of PbCl2. Adult specimens of G. affinis measuring 5-6 cm in length were obtained from a commercial fish breeding facility. A total of 8 fish with a 1 : 1 ratio of 4 pairs of broodstock were placed in an 8-liter aquarium. Following the adaptation phase, the broodstock underwent a spawning process that lasted for a duration of 7 days. Throughout the spawning process, assessments were conducted on the progression of the abdominal growth of the broodstock. Eggs ready to hatch and Gambusia larvae were taken and exposed to 0.1 mg/L PbCl2, 1 mg/L PbCl2, and control (without PbCl2) for 24 hours, with three replications. At the end of the experiment, histopathological analysis was conducted using the hematoxylin Ehrlich-eosin staining method and scanning electron microscopic (SEM) observation. The levels of Pb in gills were determined by employing atomic absorption spectrophotometer. The cortisol concentration in organ samples of fish was determined through the utilization of a cortisol ELISA Kit. The findings of this investigation demonstrated an important bioaccumulation occurrence of Pb within the gills of Gambusia fish that were specifically subjected to 0.1 and 1 mg/L PbCl2. The histological structures of eggs and larvae that were subjected to PbCl2 exhibited impairment in comparison to the control group. The present study observed a significant elevation in cortisol levels among fish specimens that were subjected to PbCl2 exposure. The findings of this investigation suggest that the occurrence of Pb is linked to a rise in cortisol concentrations in various organs of G. affinis larvae. Furthermore, the research indicates that the exposure to Pb has a notable impact on the histological alterations in the eggs and larvae of Gambusia fish, implying that they are undergoing stress as a result of the Pb exposure.

Development of spermatogonial cell transplantation in barramundi (Asian seabass: Lates calcarifer)

The selective breeding of farmed species is an essential task for sustainable aquaculture. Barramundi (Asian seabass: Lates calcarifer) is no exception in this respect, and artificial breeding is underway to establish strains with valuable genetic traits. For the long-term preservation of the many strains carrying diverse genetic characteristics, producing offspring derived from cryopreserved germ cells by transplantation into recipients is a powerful tool. Therefore, we aimed to develop a germ cell transplantation method, an essential step in obtaining the next generation derived from frozen germ cells in this study. First, testicular sections of various-sized fish (75 g–8 kg) were observed to identify the suitable maturation stages of donors. Immunocytochemistry with the antibody specifically recognizing the cell surface antigen of type A spermatogonia (ASGs) was performed. As a result, fish with <500 g of body weight possessed a higher number of ASGs, and their frequency of occurrence was also higher in their gonads. Although it was difficult to obtain sufficient amounts of testicular cell suspensions used for transplantation with conventional enzyme digestion, pretreatment using proteinase K was quite effective in dissociating the testicular tissues of this species. Next, 4–20 days post hatching (dph) larvae were sampled in a time-course manner. The development of their genital ridges was observed to identify the suitable developmental stages of larvae as recipients. By 16 dph, endogenous primordial germ cells were incorporated into the genital ridges and covered by somatic cell layers. This suggests that 16-dph or younger larvae are optimal for use as recipients. Lastly, we transplanted testicular cells, prepared using the above-mentioned optimal conditions, into the peritoneal cavity of 10–14 dph larvae. The transplantation success rate was compared for each total length of the recipient larvae. As a result, the transplantation success rates of 3.21 ± 0.093 mm, 4.00 ± 0.045 mm, and 5.01 ± 0.13 mm total length recipients were 77.2% ± 12.3%, 57.5% ± 4.7%, and 45.3% ± 4.9%, respectively. It was indicated by these results that donors weighing <500 g and larvae with a total length of about 3.2 mm are suitable for germ cell transplantation in barramundi.

Eggs Hatching of Betta Fish (Betta splendens) with The Addition of Ketapang Leaves (Terminalia cattapa Linn) at UPR Mitra Mina Sejahtera Indralaya, Ogan Ilir District

The limited number of fish seeds is still an obstacle in betta fish cultivation activities due to the low percentage of hatching and high mortality of larvae. This research aims to increase the percentage of egg hatching and survival of betta fish by stimulating ketapang leaves. This research was carried out in a controlled area at UPR Mitra Mina Sejahtera located in Griya Sejahtera Indralaya Housing, Ogan Ilir Regency from June to July 2022. The addition of ketapang leaves as much as 2 g per L (P2) can increase the hatching percentage at 96.97% and betta fish larval survival rate to 87.92%. The water quality obtained from this research is the temperature of P1 ranges from 26.4-27.3°C, P2 ranges from 26.7-27.2, control ranges from 26.5-27.1°C, pH P1 ranges from 6.5-6.9, P2 ranges from 6.5-6.7 and control ranges from 6.9-7.2 and dissolved oxygen P1 ranges from 1.03-1.09 mg per L, P2 ranges from 1.00-1.05 mg per L and control ranged from 1.04-1.10 mg per L.

Vaccination of cattle with the Babesia bovis sexual-stage protein HAP2 abrogates parasite transmission by Rhipicephalus microplus ticks

The apicomplexan parasite Babesia bovis is responsible for bovine babesiosis, a poorly controlled tick-borne disease of global impact. The widely conserved gametocyte protein HAPLESS2/GCS1 (HAP2) is uniquely expressed on the surface of B. bovis sexual stage parasites and is a candidate for transmission-blocking vaccines (TBV). Here, we tested whether vaccination of calves with recombinant HAP2 (rHAP2) interferes with the transmission of B. bovis by competent ticks. Calves vaccinated with rHAP2 (n = 3), but not control animals (n = 3) developed antibodies specific to the vaccine antigen. Vaccinated and control animals were infested with Rhipicephalus microplus larvae and subsequently infected with virulent blood stage B. bovis parasites by needle inoculation, with all animals developing clinical signs of acute babesiosis. Engorged female ticks fed on the infected calves were collected for oviposition, hatching, and obtention of larvae. Transmission feeding was then conducted using pools of larvae derived from ticks fed on rHAP2-vaccinated or control calves. Recipient calves (n = 3) exposed to larvae derived from control animals, but none of the recipient calves (n = 3) challenged with larvae from ticks fed on rHAP2-vaccinated animals, developed signs of acute babesiosis within 11 days after tick infestation. Antibodies against B. bovis antigens and parasite DNA were found in all control recipient animals, but not in any of the calves exposed to larvae derived from HAP2-vaccinated animals, consistent with the absence of B. bovis infection via tick transmission. Overall, our results are consistent with the abrogation of parasite tick transmission in rHAP2-vaccinated calves, confirming this antigen as a prime TBV candidate against B. bovis.

Monitoring the development of Ctenocephalides felis felis (Siphonaptera, Pulicidae) eggs from a laboratory colony in Brazil subjected to different adhesive substances.

This study aimed to evaluate the use of different adhesive substances in an method to monitor the development of C. felis felis eggs. Three adhesive substances were selected: cyanoacrylate, stick glue, and liquid silicone. The eggs were obtained from a laboratory colony and placed on a thin layer of adhesive substance on the lid of a Petri dish to prevent contact with the larval growth substrate. One hundred eggs were used for each adhesive substance. The development of the eggs was monitored for three consecutive days, during which larval hatching and egg characteristics were observed. Of the 100 eggs incubated for each adhesive substance, 64, 51, and 76 larvae hatched and survived from the stick glue, cyanoacrylate, and liquid silicone plates, respectively. After 30days of incubation, 59, 45, and 68 hatched adults were observed, respectively, in these groups. The mean hatching of larvae and adults between the liquid silicone and cyanoacrylate groups differed statistically (p<0.05). This study demonstrated positive results, and that liquid silicone was the most easily applicable adhesive substance on the plate and interfered less with egg development, therefore having the best larval recovery compared to incubated eggs compared to the other substances.

Nicotine and Cytisine Embryotoxicity in the Experimental Zebrafish Model.

Tobacco smoking is one of the most serious health problems. Potentially lethal effects of nicotine for adults can occur with as little as 30 to 60 mg, although severe symptoms can arise with lower doses. Furthermore, the route of administration also influences the toxicity. Cytisine is one of the most popular medications in nicotinism treatment. Like nicotine, cytisine is a plant alkaloid, signaling through nicotinic acetylcholine receptors. Our study evaluated the effects of cytisine in nicotine-induced embryotoxic effects using zebrafish larvae. We examined the teratogenicity of nicotine and cytisine alone or in combination. Nicotine increased mortality and delayed hatching of zebrafish larvae in a dose-dependent manner. Cytisine did not affect mortality in a wide range of concentrations, and hatching delay was observed only at the highest concentrations, above 2 mM. Administering compounds together partially reduced the adverse teratogenic effect induced by nicotine alone. The protective effect of cytisine against the nicotine effect, observed in zebrafish, will contribute to future studies or treatments related to nicotine addiction or prenatal nicotine exposure in humans.

Natural Spawning Technique of Koi Fish (Cyprinus carpio) in the Ciparanje Inland Fisheries Area, Sumedang, Indonesia

The Ciparanje inland aquaculture area has emerged as a hub for breeding ornamental fish, with koi fish being a prominent species. The increasing demand for koi fish has led to a surge in koi aquaculture businesses. What sets koi fish apart from some other fish species is their ability to breed throughout the year, unaffected by specific seasons. However, in their natural habitat, koi fish typically spawn at the onset of the rainy season, triggered by the enticing aroma of the soil. The growth of koi fish is influenced by various factors, including fish species, genetic characteristics, feeding efficiency, disease resistance, and environmental conditions such as water and feed quality, as well as stocking density. To ensure the production of top-quality koi fish fry, it is crucial to employ the appropriate spawning techniques. In this study, a participative approach was employed to investigate and report on the natural spawning procedures of koi fish in the Ciparanje inland aquaculture area, managed by Padjadjaran University. The natural spawning method implemented in this area encompasses several crucial processes, including the preparation of spawning ponds, selection of breeding stock, egg hatching, and larvae rearing. A total of 90,175 eggs were collected from the examined koi broodstock during the spawning activities, and an impressive 80% of these eggs successfully hatched. The calculated Hatching Rate (HR) reached 96.5%, indicating a high level of achievement in the hatching of koi fish larvae.

Fish sperm cryopreservation using biodegradable containers: New low-cost and environment-friendly methodology.

The containers used in cell cryopreservation are essential to maintain cell integrity and viability after thawing. This paper reveals the methodology of using biodegradable containers for fish sperm cryopreservation. Cryopreserved sperm in biodegradable containers showed high fertility capability. Biodegradable capsules could be alternative containers to plastic straws for sperm cryopreservation. Containers used to cryopreserve sperm are made with non-biodegradable plastic compounds, having a high monetary and environmental cost. Therefore, the development of biodegradable alternative containers for cell cryopreservation is necessary. Thus, this study aimed to evaluate the efficiency of hard-gelatin and hard-hydroxypropyl methylcellulose (HPMC) capsules as low-cost and biodegradable alternative containers for sperm cryopreservation. Sperm from 12South American silver catfish Rhamdia quelen were individually cryopreserved in plastic straws 0.25 mL (as control), hard-gelatin, and hard-HPMC capsules. The quality of post-thaw sperm cryopreserved in the different containers was checked by measuring spermatozoa membrane integrity, kinetic parameters, mitochondrial activity, fertilization, hatching, and normal larvae rates. The samples cryopreserved in straws showed a higher percentage of membrane integrity (68%) than those frozen in hard-gelatin (40%) and hard-HPMC capsules (40%). However, we did not observe differences between the samples stored in straws and hard capsules for the rest of the tested sperm parameters. Thus, based on the high sperm fertility capability, both capsules were efficient as cryopreservation containers for maintaining sperm functionality.

Verification of the Daily Periodicity of Microincrements Formation on the Otoliths of the Juvenilrs of the Ocellated Blenny &lt;i&gt;Opisthocentrus ocellatus&lt;/i&gt; (Stichaeidae) for a Retrospective Evaluation of the Period of Mass Hatching under the Conditions of Peter the Great Bay of the Japan Sea

Experiments were carried out on intravital otolith-tagging of juveniles of the ocellated blenny after transition to benthic life mode with Alizarin Red S. Marking at a dye concentration of 200 mg/L for 16–18 h at night, gave 100% formation of fluorescent marks with zero mortality of experimental individuals. Alizarin marks on the otoliths correspond to “stress” marks in the form of darker micro-increments, visible in transmitted light. The calculation of microincrements in the zone between two consecutive markings with an interval of 9 days confirmed the daily periodicity of their laying at this stage of development of the ocellated blenny. This allowed us to determine the period of hatching in natural conditions of juveniles in the Zhitkov Bay (Russky Island, the Peter the Great Bay, Japan sea). Hatching of larvae in 2017 in this species occurred, according to our estimates, from the last decade of March to the end of the second decade of April, with a peak in the first decade of April. Hatching begins even under the ice at a slightly negative water temperature of –1–0°C, but it proceeds mainly already at a temperature of 1–3°C, after the removal of ice from the bay. Taking into account the known timing of spawning of the ocellated blenny in the Peter the Great Bay (November–early December), we can state that the development of its eggs in this area is greatly slowed down at water temperatures below zero in December–March and can go on for 4–5 months, which is almost 3 times longer than the development time in more mild conditions of the south Hokkaido.