Spawning Stage Research Articles

Половая структура поселений двустворчатого моллюска Macoma calcarea (Gmelin, 1791) в районах с разным гидрологическим режимом

The influence of changes in environmental conditions on the reproductive cycles of benthic organisms (sexual structure, size of puberty, stages of gonad maturity, oocyte size) of the bivalve mollusk Macoma calcarea in the western part of the Spitsbergen archipelago (Grenfjord Bay) and the eastern part of the Barents Sea (coastal archipelago) was studied New Earth). In a settlement of M. calcarea in the warmer waters of Grenfjord, intensive reproductive processes were observed. In this area, females reach sexual maturity with a shorter shell length than males and individuals from other areas of the Barents Sea; In terms of sex ratio, females dominate over males, and a large number of juveniles are noted. Females at the spawning stage were found only near Novaya Zemlya. The diameter of the oocytes varied from 30 to 200 µm depending on the stage of maturity. In the mollusks M. calcarea, the breeding season is extended in time in both study areas.

Reproductive cycle of the temperate sea cucumber Holothuria tubulosa in the northeastern Aegean Sea

AbstractObjectiveThe aim of this study was to determine the reproductive cycle and spawning frequency of the sea cucumber Holothuria tubulosa in the northeastern Aegean Sea.MethodsThe study covered a period of 12 months, beginning in October 2018 and concluding in September 2019. During this period, sea cucumber samples were collected monthly. Macroscopic and histological examinations of gonadal tubules were conducted to provide credible information for fishery management and aquaculture.ResultThe sex ratio of the sampled population was 1:1.3, with 95 males and 130 females. The drained body weights at 50% maturity were 70.90 g for females and 70.80 g for males. The total length at 50% maturity was estimated at 18.58 cm for females and 18.05 cm for males. Gonad maturation was initiated in March and progressed to spawning stages between July and August. From September to February, the gonads were in postspawning and recovery stages. A strong linear correlation was determined between the gonad index and the seawater temperature in the area.ConclusionThe information provided is expected to improve stock management, enforce fishery regulations, and support controlled breeding programs. These measures aim to preserve the natural populations of Holothuria tubulosa and guarantee the long‐term viability of the species in the wild.

Histological study of the sex ratio and reproductive cycle of the mangrove oyster Crassostrea tulipa (Lamarck, 1819) in the Saloum Delta (Senegal)

The mangrove oyster Crassostrea tulipa has considerable socio-economic value in Senegal, as in many other West African countries. To better understand its biology, the objective of this study was to determine the sex ratio and the evolution of gonadal development stages of oyster populations in the Saloum Delta. To this end, a monthly sampling of 30 oysters between 34.19 mm and 96.68 mm height was carried out between January 2021 and January 2022. The part of the flesh that encloses the gonads was removed and fixed using Davidson's solution. After dehydration, paraffining and inclusion of the materials, 7 μm thick sections were made using a microtome. These sections were stained with Haris’s hematoxylin and eosin and the slides were observed under an optical microscope (Olympus BX41 microscope).The results showed a predominance of females over males, with a sex ratio of 1 in 2.85. The results also revealed that reproduction was continuous over the year and that spawning was asynchronous: Individuals at the spawning stage were more frequent in the warm season. These results will contribute to a better management of natural stocks and to improve oyster farming.

Polystyrene Nanoplastics Disrupt Hepatic Vitellogenin Metabolism and Impair the Reproduction Process in Female Zebrafish

Abstract For this study, 240 adult healthy female zebrafish were divided into 12 tanks (20 fish per tank) and exposed to 0 (control, T0), 0.1 (T1), 1 (T2), and 10 (T3) mg/L synthesized polystyrene nanoplastics (PS-NPs, nanoplastics synthesized in the chemistry laboratory of the Faculty of Basic Sciences at Zabol University) for 4 weeks. At the end of the experiment, exposure to PS-NPs had no significant effect on the survival of female zebrafish (P>0.05). A significant decrease of hepatic vitellogenin (Vtg) was seen in female zebrafish exposed to PS-NPs (P<0.05). The level of 17-β-estradiol (E2) and testosterone (T) were notably declined in female zebrafish of all PS-NPs-exposed groups (P<0.05). Glucose was notably increased in female zebrafish of all PS-NPs-exposed treatments (P<0.05). There was a significant increase in cortisol levels in all PS-NPs-exposed treatments (P<0.05). No significant difference was seen in lactate levels between different treatments (P>0.05). A significant enhancement in aspartate aminotransferase (AST), alanine transaminase (ALT) and alkaline phosphatase (ALP) was observed in female zebrafish of all PS-NPs-exposed treatments compared to the control (P<0.05). The present results demonstrate that PS-NPs impair the reproduction process so that none of the female zebrafish broodstock exposed to different doses of PS-NPs reached the spawning stage.

Introduksi Teknologi DNA Barcoding kepada Staf UPTD Perikanan Budidaya Air Payau dan Laut Karang Intan

Partners in community service activity are UPTD Brackish and Marine Aquaculture, Karang Intan, one of the centers under South Kalimantan Province that specializes in the hatchery of local fish such as snakehead (Channa striata), common carp (Cyprinus carpio), and climbing perch (Anabas testudineus). The problem in the partner is fish farming that still relies on seeds from nature, which causes several problems, such as slow seed growth, decreased production quality, disease attacks and hereditary abnormalities that are getting higher due to interbreeding. Based on these problems, the team collaborated with the UPTD for Brackish and Marine Aquaculture, Karang Intan, to improve the genetic quality of fish by introducing DNA barcoding techniques, especially at the spawning stage. The introduction of DNA barcoding technology is carried out through (1) classical counseling and group discussions, 2) training and assistance covering technical aspects of DNA barcoding (fish DNA isolation, DNA amplification, visualization of PCR products with electrophoresis, to the sequencing). Based on the evaluation, 100% of the participants were enthusiastic and realized the importance of DNA barcoding techniques to produce superior broodstock and fish fry, especially for snakehead, common carp, and climbing perch commodities.

Osmoregulation pattern, condition factor, and gonadal maturity level of sea urchins in the various ecosystems of Panjang Island, Jepara, Indonesia

Abstract. Suryanti S, Anggoro S, A’in C, Widyorini N. 2024. Osmoregulation pattern, condition factor, and gonadal maturity level of sea urchins in the various ecosystems of Panjang Island, Jepara, Indonesia. Biodiversitas 25: 502-509. Panjang Island has a diversity of ecosystems. It is also famous for its abundance of echinoids, especially sea urchins. Currently, research on sea urchins in Panjang Island is mostly limited to studies on the abundance and maturity of gonads. This study investigates the osmoregulation patterns, condition factors, and maturity indices of sea urchin gonads in different ecosystems that are sea urchin habitats on Panjang Island, Jepara, Indonesia. Sampling is done randomly, while the research method is a case study. The results showed that there are 2 species of sea urchins found on Panjang Island, namely Diadema setosum Leske, 1778 and Echinothrix calamaris Pallas, 1774. Analysis of osmoregulation patterns showed that sea urchins at station 1 were hyperconformers, while sea urchins at stations 2 and 3 were hypo-conformers. Sea urchins at 3 stations had a positive allometric growth pattern (b>3) and a high condition factor (K>1). The average Gonadosomatic Index (GI) calculation result was 8.72%, while the type of ecosystem of the research stations influenced the color and texture of different gonads. Sea urchins are in immature, mature, and spawning stages, so the sea urchins on Panjang Island were partially spawned.

Biology of kawakawa Euthynnus affinis in the East China Sea: Growth, reproduction, and stable isotope ratios

This study elucidated the age–growth relationship, maturation body size, and stable isotope ratios of kawakawa Euthynnus affinis in the East China Sea. A total of 396 individuals were collected, of which 266 were captured off the west coast of Kyushu and 130 around Okinawa. Ages were determined from otolith analysis, and the estimated von Bertalanffy growth functions were FLt = 1007{1 – exp[–0.107(t + 3.835)]} near Kyushu and FLt = 640{1 – exp[–0.381(t + 1.111)]} around Okinawa, where FLt is fork length (mm) at age t for ages 0.25 to 5. The estimated fork lengths of the fish near Kyushu were larger than those around Okinawa. The smallest fork length of a fish in the spawning stages was about 440 mm. Mature females and males were observed from May to October near Kyushu and from March to July around Okinawa. Females in the spawning stages were observed from July to September near Kyushu and from April to June around Okinawa. The δ15N of fish captured near Kyushu (12.39‰ ± 0.55‰, mean ± standard deviation) was higher than that of those captured around Okinawa (9.94‰ ± 1.39‰). This suggests that the kawakawa caught in each area occupy distinct habitats, although some mixing of individuals between the two habitats might occur.

Faktor-Faktor Budidaya Kerang Mutiara di Desa Maijuring Kecamatan Aru Tengah Kabupaten Kepulauan Aru

Pearl cultivation began to develop, especially in Maluku Province. With the increasing cultivation of pearl mussels, the demand for pearl seeds is also increasing, but this is also hampered by a lack of supply of seeds from wild catches or obstacles during seed production, namely high mortality at the spawning stage and in general the growth and survival of shellfish species is greatly influenced. by important factors, namely temperature and food availability and other important factors, on this basis the author conducted research which aims to determine the factors of pearl oyster cultivation in Maijuring Village, Aru Tengah District, Aru Islands Regency. The type of research used is Qualitative Descriptive analysis. With sea water samples and 5 pearl oyster cultivators. The sampling technique used is purposive sampling which uses the criteria of people who cultivate pearl oysters. The data collection techniques used are observation, documentation and interviews. The data analysis technique used is SWOT analysis. The results of the research show that in Maijuring Village there are several factors in cultivating pearl oysters, namely water quality, feed availability, water temperature, water depth, water salinity, water pH, population density, cultivation land maintenance such as water quality which is influenced by temperature, namely 26.9, pH namely 7.76, and salinity 34.42, and depth 20-30m. from the surface.

Structural and functional characterization of an egg-laying hormone signaling system in a lophotrochozoan – The pacific oyster (Crassostrea gigas)

The egg-laying hormones (ELHs) of gastropod mollusks were characterized more than forty years ago. Yet, they have remained little explored in other mollusks. To gain insights into the functionality of the ELH signaling system in a bivalve mollusk – the oyster Crassostrea gigas, this study investigates the processing of its ELH precursor (Cragi-ELH) by mass spectrometry. Some of the ELH mature peptides identified in this study were subsequently investigated by nuclear magnetic resonance and shown to adopt an extended alpha-helix structure in a micellar medium mimicking the plasma membrane. To further characterize the ELH signaling system in C. gigas, a G protein-coupled receptor phylogenetically related to ecdysozoan diuretic hormone DH44 and corticotropin-releasing hormone (CRH) receptors named Cragi-ELHR was also characterized functionally and shown to be specifically activated by the two predicted mature ELH peptides and their N-terminal fragments. Both Cragi-ELH and Cragi-ELHR encoding genes were mostly expressed in the visceral ganglia (VG). Cragi-ELH expression was significantly increased in the VG of both fully mature male and female oysters at the spawning stage. When the oysters were submitted to a nutritional or hyposaline stress, no change in the expression of the ligand or receptor genes was recorded, except for Cragi-ELHR only during a mild acclimation episode to brackish water. These results suggest a role of Cragi-ELH signaling in the regulation of reproduction but not in mediating the stress response in our experimental conditions.

Biological aspect approach in sustainable management of coral catshark Atelomycterus marmoratus (Anonymous [Bennett], 1830) in Bali Strait, Indonesia

Abstract. Lelono TD, Bintoro G, Harlyan LI, Setyanto A, Rihmi MK, Rudianto D. 2023. Biological aspect approach in sustainable management of coral catshark Atelomycterus marmoratus (Anonymous [Bennett], 1830) in Bali Strait, Indonesia. Biodiversitas 24: 5873-5882. Coral catshark (Atelomycterus marmoratus) is a shark species that thrives in many coral reefs. to evaluate the biological aspects of A. marmoratus and their type of growth curve for a time series to support their sustainability. Sampling was performed from August 23rd, 2019, to March 31st, 2020. The morphological analysis was performed by recording or photographing to reduce possible errors. Then, the length-weight relationship, sex ratio, length at first captured and matured, and spawning ratio were evaluated. The present study demonstrated that the coral catshark captured in the cohort that produces two cohorts only happens in February. The sex ratio is 41.6% male and 48.4% female, which is considered healthy, whereas the remaining percentage is so severely damaged that its gender cannot be determined. The FISAT-II software analysis results in a von Bertalanffy growth formula of Lt = 76.21 (1-e-2.01(t+0.0596)) with t max = 1.49/ year and L max = 77.39 cm. They grow steadily or tend to slow down after they reach the age of 1.5 years, with an asymptotic length of 77.39 cm. The Lc value (67.5 cm) is more significant than their Lm value (53 cm), indicating that their sustainability is highly possible to maintain because only fish that have passed the spawning stage are captivated. The spawning potential rate (SPR) is 35%, with M = 0.66, E = 1.85, and F = 0.78. These results indicate that the exploitation rate of coral catshark is moderate because 20% < SPR < 40%. In conclusion, the A. marmoratus length-weight relationship is categorized as negative allometric, where the length grows faster than the weight.

Study on reproductive endocrine disturbance and DNA damage mechanism of female Ruditapes philippinarum under Benzo[a]pyrene stress

The reproductive toxicity of polycyclic aromatic hydrocarbons (PAHs) in aquatic organisms has attracted increasing attention from scholars. Currently, research in this field primarily focuses on vertebrates such as zebrafish and other model species. However, there is still a significant knowledge gap in the toxicity of PAHs to invertebrates and its potential mechanisms. Benzo[a]pyrene (B[a]P) is one of the most representative PAHs. In this study, female Ruditapes philippinarum (R. philippinarum) was treated with B[a]P concentrations of 0, 0.8, 4, and 20 μg/L to investigate reproductive indicators in the proliferative, growth, mature, and spawn stages. Transcriptomics was used to investigate the expression of genes associated with the reproductive endocrine system, DNA repair, autophagy, apoptosis, and ovarian development at different reproductive stages. Our results suggested that B[a]P disrupted the endocrine system by interfering with the production of steroid hormones and the transmission of estrogen signals in female R. philippinarum. The structure of the ovarian DNA duplex is severely damaged under the stress of B[a]P, and a series of cellular responses caused by DNA damage are also interfered. Additionally, we observed a reduction in the gonadosomatic index (GSI) and mature oocytes numbers after B[a]P exposed. Tissue section indicated that severe damage to the ovarian structure at mature and spawn stages. In conclusion, this study combined transcriptomic and toxicological to explore the negative effects on ovarian development induced by B[a]P, focusing on reproductive endocrine disturbance and DNA damage.

Optimizing flow regime for the Four Major Chinese Carps by integrating habitat suitability within reservoir operation

The construction of dams has brought many benefits to human society. However, it has also altered the natural hydrological regime, affected aquatic organisms’ habitat conditions and decreased important fishery resources. In the post-dam construction era, it has become crucial to evaluate the ecological flow requirements for all stages of fish life and ensure the provision of dynamic flow pulsation, particularly during the spawning stage. Here, we proposed a Reservoir Operation Model for Fish Habitat across Life Stages (ROM-FHLS) to reconcile the apparent contradiction between fish habitat preservation and hydropower generation in the Yangtze River Basin. Compared with the conventional outflow conditions, our model demonstrated significant improvements in power generation and suitable habitat area during the migration, spawning and incubation, and juvenile periods. Specifically, we observed average increases of 15.2%, 13.1%, and 6.7% in power generation, and enhancements of 16.5%, 17.3%, and 1.8% in suitable habitat area, respectively. Our approach advocates for the comprehensive protection of fish throughout their entire life cycle while highlighting the feasibility of enhancing fish habitats without compromising power generation. Furthermore, we proposed an outflow scheme that incorporates pulsation patterns into reservoir operations to effectively stimulate fish spawning activities. This study presents a fresh perspective on comprehending the intricate interplay among dam-controlled hydrological processes, river hydrodynamic environment, and fish behavior. The findings have the potential to enhance fish spontaneous reproduction and aid in the recovery of aquatic populations in large dammed rivers.

Fatty acid composition and energy allocation in muscle and gonad tissues indicate that the female mackerel icefish Champsocephalus gunnari is an income breeder.

The energy density and fatty acid composition profiles of the muscle and gonad tissues of female mackerel icefish Champsocephalus gunnari from the South Orkney Islands in Antarctica were investigated throughout ovarian development to better understand the reproductive allocation strategy and the role of specific fatty acids in the reproductive process. Energy density in gonads increased from resting to spawning stages as the ovaries developed (19.60-25.10 kJ g-1 dry mass [DM]). In contrast, energy density in muscles remained constant throughout ovarian development (20.13-22.87 kJ g-1 DM), suggesting that the spawning events of the C. gunnari rely on energy income from feeding rather than on the energy stored in body. In addition, the variation in fatty acid composition between muscle and gonad tissues may reflect the role of main FAs as energy source. These results suggest that C. gunnari may utilize an income breeding strategy.

Impacts of sublethal concentrations of 17 α-ethinylestradiol (EE2) on growth, reproductive performance, and survival in red cherry shrimp Neocaridina davidi (Crustacea, Atyidae) during consecutive spawnings

This study was conducted for the first time to investigate the long-term impacts of sublethal concentrations of 17 α-ethinylestradiol (EE2) on growth, survival, and reproductive performances in a model shrimp, the red cherry (Neocaridina davidi), females during five successive spawning steps for 7.5 months. Females were distributed in eighteen aquariums and continuously exposed to EE2 at six nominal concentrations of 0 (control), 0.02, 0.2, 2, 20, and 200 μg/L. Growth indices increased up to 0.2 μg/L and then sharply declined up to 200 μg/L. Most reproductive indices significantly decreased at levels > 0.02–0.2 μg/L with increasing EE2 levels. The highest absolute, relative, and actual fecundity values were recorded in the control, with the lowest value at 200 μg/L. With increasing EE2 levels, mean egg volume showed an increasing trend from the third spawning event onwards. Except for the time required to reach the first spawning, inter-spawning intervals considerably decreased with increasing EE2 levels at > 0.2 μg/L, especially from the third spawning stage onwards. Survival of exposed females significantly decreased with increasing EE2 levels. Unlike the body size, the juvenile's survival rates in all exposed treatments were considerably lower than the control. Females at concentrations 0.02–0.2 μg/L gained more body weight and length but produced fewer eggs with lower hatching percentages during five consecutive spawns. The results suggest that EE2 depending on the concentrations can cause unbalanced growth, reduce reproductive performances, especially from the third stage of spawning onwards, and reduce survival rates in brooders and subsequent offspring. In terms of growth, survival, and reproductive indices over successive spawns in ecotoxicology studies, the concentrations of 0.02–0.2 μg/L can be considered as chronic levels, but higher levels may have detrimental effects.

Fisheries and Biology of Otolithes ruber (Bloch & Schneider, 1801) Catch of Small-scale Fisherfolk in San Miguel Bay, Philippines

Otolithesruber (Bloch & Schneider, 1801) is one of the major fish catches in San Miguel Bay and its processing is a seasonal livelihood among coastal villages. This study documented and described the O. ruber catch of small-scale fisherfolks around the Bay through on-board survey and observation. Fishing trips from 10 September to 19 November 2018 demonstrated that fisherfolks used bottom-set gill nets and commonly explored the middle to the mouth of the Bay off Mercedes and Siruma to catch O. ruber and other species. The analysis of 434 composite fish samples bought from the fishing trips identified 222 female and 212 male fish individuals with TL of 19.14 + 0.11 cm and body weight of 70.76 + 1.46 g. The majority were already mature to spawning stages and gonads had no apparent lesions. The population’s reproductive capacity, based on the presence of numerous spermatocytes and oocytes, was presumed to be realized, but this may fail due to uncontrolled illegal fishing.

Dose-dependent inhibitory effects of glyphosate on invasive Pomacea canaliculata reproductive and developmental growth under oxidative deposition

Glyphosate (GLY) is the most widely used herbicide worldwide, and its effects on animals and plants have attracted increasing attention. In this study, we explored the following: (1) the effects of multigenerational chronic exposure to GLY and H2O2, alone or in combination, on the egg hatching rate and individual morphology of Pomacea canaliculata; and (2) the effects of short-term chronic exposure to GLY and H2O2, alone or in combination, on the reproductive system of P. canaliculata. The results showed that H2O2 and GLY exposure had distinct inhibitory effects on the hatching rate and individual growth indices with a substantial dose effect, and the F1 generation had the lowest resistance. In addition, with the prolongation of exposure time, the ovarian tissue was damaged, and the fecundity decreased; however, the snails could still lay eggs. In conclusion, these results suggest that P. canaliculata can tolerate low concentrations of pollution and in addition to drug dosage, the control should focus on two time points, the juvenile and early stage of spawning.

Numerical modeling of pre-spawning and spawning migrations of the representative of the family hexagrammidae: the case of the arabesque greenling

This paper presents a spatio-temporal model of greenling dynamics during pre-spawning and spawning mass migrations. The developed model is based on original verified long-term observations and data on industrial fishing in the Peter the Great Bay (Sea of Japan), and the equations of the dynamics of the density of males/females and the mass daily movements of fish are written in terms of the transfer equations. These equations are written in the form of the modified Patlak-Keller-Segel equations, according to which the flow of objects/substances is directed along the gradients of stimulus introduced. It is believed that in the pre-spawning season, adaptation in morpho-physiological (biochemical thermoregulation and a number of other endogenous processes) and behavioral responses of fish to sufficiently long and energy-consuming spawning can occur, where the stimulus for mass movements of fish is optimal environmental conditions for spawning events. During the spawning period, selected sites will be found in convenient and well-aerated embayments located at the bottom of reservoir in the coastal area. Modeling of stimuli-related movements is performed based on information about the preferred water depths of the fish's pre-spawning area and relevant features relating to a selection of suitable bedding sites. It is assumed that the intensity of daily motion is proportional to their linear size (the larger the fish becomes, the faster it is). The equations for the spawning stage take into account the spatial competition of males, but in natural conditions it is observed only in the vicinity of spawning areas. Being away from these areas, males continued to look for new sites good for the spawn. For females, their movement is provoked by males that assembled in schools, the signal of which can be certain chemical elements released by males (for example, mucus secretion from males) or visual contact. The diffusion of fish distribution and the viscosity of the habitat (velocity diffusion) are taken into account. The initial distribution of fish is given according to the average distribution of fish in July over a long-term observation period in the Peter the Great Bay.

Reproductive condition of the black-lip pearl oyster Pinctada margaritifera during the lunar phase.

This study analyzed the relationship between the lunar phase and the reproductive cycle of Pinctada margaritifera inhabiting Weno Island, Chuuk Lagoon, Micronesia. We measured indicators of maturity (gonadosomatic index [GSI]and sexual maturation-related genes) and investigated changes in the gonadal maturity stages (GMS) of P. margaritifera over lunar cycle. GSI was higher around the full moon. GMS of P. margaritifera were classified as the early gametogenesis stage, ripe and spawning stage, and spent and degenerating stage. A large percentage of oysters was observed in the ripe and spawning stage at the first quarter moon in female and the full moon in male as well as in the spent and degenerating stages at the third quarter moon in both sexes. In addition, the expression of doublesex- and mab-3-related transcription factor 2 (DMRT2) in the male P. margaritifera black-lip pearl oyster was the highest during the full and third quarter moon phases, whereas no difference in expression was observed with the lunar phase in females. In contrast, the expression of vitellogenin (VTG) was the highest in female P. margaritifera during the first and third quarters. No difference in expression was observed according to the lunar phase in males. The results suggest that the lunar phase directly affects the expression of sexually mature gonads in P. margaritifera black-lip pearl oyster.

Variability of physiological and biochemical parameters of the blood of beluga females (Huso huso) in the conditions of artificial reproduction

The results of a study and analysis of the physiological and biochemical parameters of the blood of beluga females (Huso huso) during the spawning period were presented in the article. The data were obtained in the laboratory of molecular genetics and physiology of the Volga-Caspian branch of the VNIRO (CaspNIRKH) in the period 2020–2022 during the monitoring of artificial reproduction. We studied females of the V stage of gonads maturity of natural (domesticated stocks) and artificial parameters of blood in beluga females during the spawning period was calculated using descriptive statistics based on parametric and nonparametric criteria. A comparative analysis of females of domesticated stocks and broodstocks revealed an unreliable (p > 0.05) trend of excess of the studied physiological and biochemical parameters in the blood of individuals of artificial generation, with the exception of beta-lipoproteins. The established ranges of blood components characterized the heterogeneity of the functional state of spawners at the spawning stage. There was a positive correlation (p < 0.05) between cholesterol and total lipids (r = +0.56), cholesterol and beta-lipoproteins (r = +0.74), beta-lipoproteins and total lipids (r = +0.44),hemoglobin and total serum protein (r = +0.58). The recorded dynamics testified to a unidirectional regularity in the consumption of fish biochemical components for the formation of reproductive products. The results obtained are necessary to assess the “quality” of beluga spawners in order to optimize the technologies for obtaining physiologically high-grade juveniles under conditions of artificial reproduction.

Changes in Tissue Distribution of Tetrodotoxin and Its Analogues in Association with Maturation in the Toxic Flatworm, Planocera multitentaculata.

The toxic flatworm, Planocera multitentaculata, possesses highly concentrated tetrodotoxin (TTX), also known as pufferfish toxin, throughout its life cycle, including the egg and larval stages. Additionally, TTX analogues, 5,6,11-trideoxyTTX and 11-norTTX-6(S)-ol, have also been detected in the flatworm. The high concentration of TTX in the eggs and larvae appears to be for protection against predation, and 11-norTTX-6(S)-ol in the pharyngeal tissue in the adults is likely used to sedate or kill prey during predation. However, information on the role of 5,6,11-trideoxyTTX, a potential important biosynthetic intermediate of TTX, in the toxic flatworm is lacking. Here, we aimed to determine the region of localization of TTX and its analogues in the flatworm body, understand their pharmacokinetics during maturation, and speculate on their function. Flatworm specimens in four stages of maturity, namely juvenile, mating, spawning, and late spawning, were subjected to LC-MS/MS analysis, using the pharyngeal tissue, oocytes in seminal receptacle, sperm, and tissue from 12 other sites. Although TTX was consistently high in the pharyngeal tissue throughout maturation, it was extremely high in the oocytes during the spawning period. Meanwhile, 5,6,11-trideoxyTTX was almost undetectable in the pharyngeal part throughout the maturation but was very abundant in the oocytes during spawning. 11-norTTX-6(S)-ol consistently localized in the pharyngeal tissue. Although the localization of TTX and its analogues was approximately consistent with the MS imaging data, TTX and 11-norTTX-6(S)-ol were found to be highly localized in the parenchyma surrounding the pharynx, which suggests the parenchyma is involved in the accumulation and production of TTXs.