Gonad Somatic Index Research Articles

The comparative toxicity of rainfall overflows and a municipal effluent plume in Elliptio complanata using a novel qPCR array approach

Municipal effluents have the potential to disrupt the endocrine system involved in reproduction in aquatic organisms. The purpose of this study was to develop a novel a quantitative polymerase chain reaction (qPCR) array for the freshwater mussel Elliptio complanata to compare the toxic properties of municipal effluents and rainfall overflows. Mussels were caged for 3 months at upstream and downstream sites of a municipal effluent discharge point and 2 rainfall overflow sites in the Saint-Lawrence River. The data revealed that exposure to municipal effluents and overflow sites lead to increased expression of vitellogenin (VTG) in male mussels, altered sexual differentiation in females, gene expression involved in oxidative stress (superoxide dismutase, glutathione S-transferase) and DNA damage (chromosome mismatch and repair of covalently-bound DNA adducts). Mussels at the downstream site accumulated also large amounts of heterotrophic bacteria but not at the overflow sites. However, mussels at the overflow sites had decreased expression in ABC transporter gene expression. Scaling analysis revealed that the following gene expression were related to effects at higher level of biological organization such as total RNA levels, gonad mass and gonad somatic index: DNA repair of covalent DNA adducts, mistmach chromosomal recombination during meiosis and undifferentiated cells in gonads. In conclusion, exposure to rainfall overflow sites have similar effects to municipal effluents based on VTG and oxidative stress responses at the transcriptomic levels only but the effects at the DNA integrity and sexual differentiation were involved in adverse outcome pathways of urban pollution in Elliptio complanata mussels.

TO THE METHODOLOGY FOR SEPARATION OF MIGRATING POPULATION COMPLEXES OF THE OKHOTSK SEA PINK SALMON IN THE PACIFIC WATERS AT KURIL ISLANDS USING THE GONAD-SOMATIC INDEX

New method is proposed for operational differentiation of pink salmon runs with different time of spawning and different state of gonads measured quantitatively with a gonad-somatic index. Results of this new method and traditional methods of differentiating are compared. The conception of spatial niches in the Pacific waters adjacent to Kuril Islands for certain temporal groupings of the Okhotsk Sea pink salmon is critically revised on the base of these new results. The runs cannot be separated using any fixed value of the gonad-somatic index. The zones of different groupings could be spatially overlapped. The method is tested on the data of trawl survey conducted aboard RV Professor Kaganovsky in May-July 2018, during anadromous migration of pink salmon, and shows a high compliance with the regional groupings ratio determined on the data of pink salmon catch in the Okhotsk Sea and their escapement to rivers. Tendency of the late-maturing forms of pink salmon to migrate through the southern Kuril waters is confirmed, whereas the portion of early-maturing pink has increased toward the Ocean.

Impacts of different feeding modes on the gonadal development, total edible yield, and nutritional composition of male Chinese mitten crab (Eriocheir sinensis)

This study analyzed the tissue indices, proximate composition, fatty acid and amino acid composition of edible tissues of male E. sinensis under three feeding modes (formulated diets (FD), natural diets (ND), and traditional diets (TD)). The results showed that different feeding modes had no impacts on the overall gonadal development, as no significant difference was found in gonadsomatic index among three treatments. For edible yield, three modes all had similar levels of the meat yield, hepatosomatic index, and total edible yield. Although different feeding modes did not affect the individual edible yield and gonadal development, significant differences were detected in the nutritional composition of males from three modes. For proximate composition, significant differences were found in the total lipids of gonads and the carbohydrate of hepatopancreas and meat. For fatty acids, crabs from ND had a higher proportion of monounsaturated fatty acids. In gonads and hepatopancreas, FD had a higher proportion of long-chain polyunsaturated fatty acids. For amino acids, FD had higher amino acid contents, while ND had the lowest. Except tryptophan, the essential amino acids scores of the meat were all greater than 100. As there was no significant difference on meat quality and meat yields between three feeding modes, this study suggests that the formulated diet could replace the natural diet and traditional diet towards sustainable crab farming in future.

Addition of lemuru fish oil in feed on the gonadal maturity level of female silver barb, Rasbora argyrotaenia

The development of aquaculture technology to produce silver barb is constrained by the low fecundity and long space of reproduction periodicity. As a consequence, feed manipulation is necessary to improve fecundity and gonadal maturity. Fecundity and gonadal maturity could be developed through additional fat from lemuru fish oil. Lemuru fish oil contains high Omega-3 that frequently used in the vitellogenesis process. The objectives of this study were adding lemuru fish oil in feed to increase the gonadal maturity level of the female silver barb. This research applied a completely randomized design (CRD) method which consist of five treatments (0%,2%,4%,6%,8%) in adding the different concentration of lemuru fish oil in feed and four replications for each. The feeding was done three times a day, at 4% biomass in 42 days of treatment. The parameters observed in this study were the gonadal maturity level in morphology as well as histology, gonad somatic index (GSI), gonad index (GI) of the female silver barb. The results of this study indicated that the addition of lemuru fish oil at 4% concentration in feed was able to accelerate 60% of the population of female silver barb gonadal maturity in the level of III and IV.

SOME BIOLOGICAL ASPECTS OF SKIPJACK TUNA (Katsuwonus pelamis LINNAEUS, 1758) DI PERAIRAN TOLI-TOLI WATERS, CENTRAL SULAWESI

Skipjack tuna (Katsuwonus pelamis) was one of the export commodities, where the demand tends to increase. The high level of skipjack tuna exploitation leads to overfishing, so sustainable fisheries management was required. The objective of the research was to study the several aspects of biology including of length of weight relationship, sex ratio maturity stage, gonad somatic index (GSI), Length at first capture and length at first maturity. The research was conducted in February - December 2015 in Toli-toli, Central Sulawesi. The results showed that the skipjack tuna growth pattern was allometrically positive, where growth weight was faster than the length increase. The length of the first time capture skipjack tuna of pole and line was bigger than length at first maturity, it means the mostly skipjack tuna caught have already spawned. The spawning season was occur throughout the year with spawning peaks in April and September, fecundity ranging from 450,570 - 1,707,390eggs.

Chu kỳ sinh sản của điệp (giống Chlamys, họ Pectinidae) phân bố tại đảo Nam Du, tỉnh Kiên Giang

Scallops, belonging to Pectinidae family, were collected from Nam Du Island, Kien Giang province from September 2017 to August 2018 to study the reproductive biology, especially reproductive cycle. Gonadal somatic index (GSI) of scallops reached high values from September to November and from January to March, in which, the maximum value was recorded in November (8.29±2.51%) and January (8.91±2.69%). Female scallops presented high GSI from September to November, from January to February and in June, in which highest GSI occurred in January (12.48 ± 4.05%) and November (9.59 ± 4.22%). The positive relationship between GSI and egg volume of female scallops was observed in January, June, September and November. The results showed that scallops in Nam Du Island could spawn all year round; however, highest spawning synchronization occurred in January, June and November.

ЗАКОНОМЕРНОСТИ ПОЛОВОГО СОЗРЕВАНИЯ ТИХООКЕАНСКОЙ СЕЛЬДИ CLUPEA PALLASII (VAL.) НА ПРИМЕРЕ КОРФО-КАРАГИНСКОЙ ПОПУЛЯЦИИ

Analysis of field and laboratory identifications stages of gonad maturity was carried out for 1960–2017. The dynamics of the gonad size and weight and of the gonad-somatic index during maturation were studied. The size structure and the condition of herring oocytes in the ovaries of different stages of maturity was figured out. Seasonal maturation was considered.

Identification of neuropeptides from eyestalk transcriptome profiling analysis of female oriental river prawn (Macrobrachium nipponense) under hypoxia and reoxygenation conditions.

The oriental river prawn, Macrobrachium nipponense, is a commercial freshwater prawn species in China. It is highly sensitive to hypoxia, and this has posed a challenge to its intensive culturing. To date, the effects of hypoxia on reproduction in female prawns are not entirely clear, as are the underlying mechanisms of the effects of hypoxia. In this work, comparative transcriptome and gene expression analyses of the eyestalk were performed in M. nipponense females under hypoxia and reoxygenation conditions. Sequencing and de novo assembly of the combined reads yielded 43,583 unigenes with an average length of 1726bp. A total of 711 genes were found to be differentially expressed in the eyestalk under the hypoxia and reoxygenation conditions. With the help of functional and pathway enrichment analysis of the differentially expressed genes, a novel set of transcripts that were associated with several important functions, such as hormone biosynthesis and progesterone-mediated oocyte maturation, were identified. Additionally, ten neuropeptides were identified based on the differentially expressed transcripts, and they were validated by quantitative real-time polymerase chain reaction (qRT-PCR) and reverse transcription PCR (RT-PCR) analyses. Three neuropeptide genes were expressed in the neural tissue and ovary of the prawns; this indicates that they were involved in reproductive processes. In particular, RNA interference (RNAi) short neuropeptide F dramatically promoted ovary maturation, as indicated by the gonad somatic index. While the present findings do indicate that hypoxia affects reproductive function in M. nipponense females, in-depth functional analyses of the candidate neuropeptides should be conducted in the future to understand their role in hypoxia adaptation and the associated mechanisms that affect the reproductive capacity of this species.

GONAD DEVELOPMENT OF SANDFISH (Holothuria scabra) FED WITH VITAMIN E-SUPPLEMENTED DIET

The experiment was conducted to evaluate the effect of vitamin E on the gonad development of sandfish, Holothuria scabra. Four experimental diets were formulated to contain different levels of vitamin E, i.e. 0, 150, 300, and 450 mg/kg diet. Dry diets were prepared at the same protein level (14%). The experiment was arranged in a completely randomized design with four treatments and three replicates. Before the experiment started, the internal organs of broodstock were removed (evisceration) by injecting KCl 1 N reagent into their body, and the gonads were observed to determine the sex of each broodstock. Mean total length and body weight of broodstock after the internal organ removal were 10.95 ± 0.37 cm and 61.12 ± 2.28 g, respectively. Three broodstock (one male and two females) were allocated into each plastic bucket with a volume of 150 L. Each plastic bucket was equipped with aeration and flow-through water system. Broodstock fed with experimental diet once daily at 3% of total biomass for 90 days. The results showed that vitamin E has significant effects on percentage of gonad maturation stages and gonad somatic index (GSI) (P<0.05). Vitamin E at 300 mg/kg diet was the best for gonad maturation of sandfish broodstock. Furthermore, 55.5% and 11.1% of broodstock fed a diet containing 300 mg vitamin E/kg diet reached gonad maturity stage-III and stage-IV, respectively, with GSI of 12.21%.

Characterization of TRH/GnRH-like peptides in the sea cucumber, Holothuria scabra, and their effects on oocyte maturation

Thyrotropin/Gonadotropin-releasing hormone (TRH/GnRH) is a neurohormone that plays important roles in regulation of several physiological processes of invertebrate species, including echinoderms. The aims of this study were to characterize for the first time a TRH/GnRH-like peptide in the sea cucumber, Holothuria scabra. We have isolated a full-length cDNA for a TRH/GnRH preprohormone gene from the radial nerve cord of H. scabra. We found that H. scabra (hs)TRH/GnRH precursor comprised two types of peptides, namely, the short TRH/GnRH-like peptides and the long TRH/GnRH-like peptides. The expression of hsTRH/GnRH gene, was intense in radial nerve cord, nerve ring and mature ovary by using RT-PCR. By in situ hybridization the transcripts of hsTRH/GnRH was detected at a high level within the late stages (oocyte stages 3 and 4). In the functional assays, injections of the short TRH/GnRH-like peptides could significantly accelerate gonadal development as reflected by increased gonadal-somatic index (GSI), and stimulated gametogenesis, as reflected by significantly increased oocyte proliferation. Taken together, our new discovery of the TRH/GnRH-like peptides in H. scabra contributes important new insights into the evolution of TRH/GnRH neuropeptide system in this sea cucumber species, and these neuropeptides could be potentially applied in the sea cucumber aquaculture.

Saros Körfezi’ndeki (Kuzey Ege Denizi, Türkiye) Kupes Balığının (Boops boops Linnaeus, 1758) Üreme Zamanı ve Ağırlık-Boy İlişkisinin Belirlenmesi

Bu çalışma Ocak 2014-Aralık 2015 tarihleri arasında Saros Körfezi’nde yürütülmüştür. Türün üreme zamanı gonadların aylık ağırlık değişimleri dikkate alınarak GSI (Gonadosomatik indeks) = (Gonad Ağırlığı / Vücut ağırlığı - Gonad Ağırlığı) × 100 eşitliğinden, ağırlık-boy ilişkisi ise W = aLb denklemi kullanılmak suretiyle elde edilmiştir. Üreme zamanının Mart ve Mayıs ayları arasında olduğu gözlemlenmiştir. Dişi bireyler için ağırlık-boy ilişkisi W = 0.0085TL3.11, erkek bireyler için W = 0.0095TL3.07 olarak hesaplanmıştır.

Control performance of fish short term reproduction assays with fathead minnow (Pimephales promelas)

The fish short-term reproduction assay (FSTRA) is an in vivo screen to assess potential interactions with the fish endocrine system. After a 21-day exposure period vitellogenin (VTG) and secondary sexual characteristics are measured in males and females. Egg production and fertility are also monitored daily throughout the test. This paper presents data from 49 studies performed to satisfy test orders from the United States Environmental Protection Agency's Endocrine Disruptor Screening Program. Data Evaluation Records were used to collate the typical control variability and performance of test parameters in FSTRAs conducted in different laboratories with fathead minnow (Pimephales promelas). We also examine the statistical power of FSTRA endpoints and assess whether available historical control data (HCD) assist evidence-based interpretation of the endpoints. Statistically significant inter-laboratory differences were found for all endpoints except survival. HCD could therefore be usefully developed on a laboratory-by-laboratory basis to aid interpretation of new study data. Reliable HCD ranges could be developed for survival, body weight/length, gonadal somatic index, fertilisation success, and male tubercle score, and used in association with stated test acceptability criteria to interpret FSTRA data. In contrast, high intra- and inter-laboratory control variability for VTG and fecundity means that HCD for these endpoints are of limited use during study interpretation.

Reproductive Cycle of the Edible Sea Urchin Paracentrotus lividus (Echinodermata: Echinoidae) in the Aegean Sea

The sustainable management of fisheries resources requires extensive knowledge of their reproductive biology, which is scarcely the case for marine invertebrates. Sea urchins are among the most intensively harvested invertebrates, since their gonads, or “roe”, constitute a highly appreciated gastronomic delicacy, causing a severe decline in natural populations worldwide. In the Mediterranean, the typical commercial echinoid species is Paracentrotus lividus; its biology, however, has not been adequately studied in the Aegean Sea. Within this context, the present study examined the reproductive biology of the edible sea urchin, P. lividus, in the Aegean Sea (Pagasitikos Gulf) over a two-year period. Adult specimens were randomly collected by SCUBA diving (3–5 m) at monthly intervals to determine the gonad-somatic index, fecundity, and gametogenesis through the morphological and histological examination of the gonads. An annual reproductive cycle was defined in both years with a clear spawning peak in early spring, conforming to previous reports from other Mediterranean populations. A discrete secondary spawning period was also detected in early winter, as the species undergoes a second gametogenic event. These results are indicative for the increased reproductive potential of P. lividus in its south distributional range, suggesting a relevant revision of the official fishing season of the species.

Seasonal fluctuations of metal bioaccumulation and reproductive health of local oyster populations in a large contaminated estuary

Despite of much evidence of trace metal pollution in the Pearl River Estuary (PRE), the seasonal dynamics of metal bioavailability as well as the potential impacts of metal pollution on the local marine organisms in this estuary is poorly understood. In the present study, the accumulation of trace metals and reproductive states of three populations of oyster Crassostrea hongkongensis, a keystone bivalve species in the PRE, were for the first time investigated throughout a one-year field study. Significant temporal fluctuations of metal accumulation were observed in the somatic tissues of oysters, suggesting seasonal variations of metal bioavailability in the PRE. A major feature of the seasonal variations was the increased levels of metal bioaccumulation in the summer season for the contaminated sites nearby the major river inlets. High riverine inputs accompanied by relatively lower salinity in summer may greatly contribute to such variations. Furthermore, oyster populations from two contaminated sites had a poor reproductive condition in comparison with the reference oyster population, as reflected by a significant decrease of gonad-somatic index (GSI) and gonad cover area (GCA), as well as an obvious change of sex ratios. Gonadal metal accumulation of Cu, Zn, Ni, Co and Pb in the contaminated oysters was much higher than that in the relatively uncontaminated oysters. Especially, the concentrations of these metals in the gonad during the breeding season had significantly negative correlations with the gonad condition indexes (GSI and GCA). Our results suggested strong seasonal fluctuations of bioavailability of trace metals in this highly contaminated estuary as well as an adverse effect of metal pollution on the reproduction of local oyster populations.

Sizes and Aspects of Reproductive Caung Fish (Arius Sagor) in The Water of Cileureum River Water in Cilacap District

Arius sagor is a fish that grow and thrive in tropical waters, and an abundance of demersal fish resources in the waters of Indonesia, particularly in Cibeureum estuaries. The purpose of this research to determine the size of Arius sagor on various habitat types and determine gonad somatic index Arius sagor in estuaries Cibeureum, CilacapRegency. This research was carried out from December 2014 to January 2015 in estuaries Cibeureum, Cilacap Regency. The research method used purposive random sampling method based on different types of habitat. The number of samples obtained by 90 consisted of 32 females and 58 male fish. Fish length and weight data on different habitat types were analyzed by using ANOVA and Tukey test using, the gonad somatic index analyzed descriptively. The results of the analysis show that there is a real or significant differences (P <0.05). The length of Arius sagor on habitat types 1 and 2, and 2 and 3. While the weight of the fish is different in each habitat type 1 and 2, 1 and 3, 2 and 3. The ranged of the gonad somatic index value 1.10% - 2.33% (male) and 1.15% - 1.77% (female). The results showed that the value of the IGS Arius sagor is in phase II.

Maturity and Spawning of Flying Fish (Hirundichthys oxycephalus Bleeker, 1852) in Makassar Strait, South Sulawesi

Flying fish, Hirundichthys oxycephalus Bleeker 1852 is one species with important social economic values. There are strong indications that this species is over-exploited in the waters of the Makassar Strait. This study aimed to analyse the spawning season, spawning frequency, level of productivity, and the length at first maturity. The spawning season analysis was based on GML (gonad maturity level) and GSI (gonad somatic index) distribution, while spawning frequency analysis was based on the distribution of egg diameter and gonad histology. Determination of size at first maturity used a formula based on the relationship between fish length and a 50% proportion of mature gonads. Determination of productivity level refers to the reproduction index criteria. The study found that flying fish begin to spawn between the months of February-March, with a spawning peak from June to July, and the spawning season ends around September-October. Flying fish spawn partially around 3-4 times in one season, with mature gonads starting to be found at a fork length of 151.5 mm. The flying fish productivity was classified as high, indicating potentially high resilience.

First contribution to the description of reproductive structures of Nelsonia goldmani (Rodentia: Cricetidae)

Nelsonia is a genus of rodent endemic to Mexican highlands with only two species: N. neotomodon (Western diminutive woodrat) and N. goldmani (Goldman´s diminutive woodrat). These species are taxonomically interesting because the few internal and external morphological differences were reported between them. Unfortunately, the scarcity of specimens and preserved internal organs available of these species limits the information to perform taxonomic studies. Hence, the objective of this study was to describe the reproductive structures in one specimen of N. goldmani collected in the biogeographic region known as Transmexican Volcanic Belt, located in the highlands of the central Mexico. We describe the external structures of the phallus and take nine measurements. The baculum was measured and described after using the classical methodology to clear, stain and preserve the whole phallus. The spermatozoa and inner testes were described using light microscopy, scanning electron microscopy, and histological techniques. Testicular volume was 319.64 mm3 and 1.34% of gonad somatic index. The phallus was relatively simple externally, laterally cylindrical, and dorsally resembling an elongated bottleneck. The baculum is an osseous structure with a cartilaginous part in its distal section. The sperm has a total mean length of 182.58 µm with an asymmetric head, a slight depression in its base and a large recurved hook. The histological analysis of testes indicated active spermatogenesis. We found important differences in the features and form of the phallic and baculum between N. neotomodon and N. goldmani. In N. goldmani some phallic forms were different, and some features measurements were greater than N. neotomodon. The external structures and the internal position of the baculum differ between the two species. In addition, the sperm size in N. goldmani was greater than other rodents, even those of larger corporal size like some species phylogenetically close as Neotoma genus.

Effect of protein and lipid levels in diets for adult sea urchin Paracentrotus lividus (Lamarck, 1816)

Paracentrotus lividus gonads are considered a prized seafood delicacy due to its organoleptic features. The increasing market demand for sea urchin depleted several wild stocks, thus aquaculture can play an important role in supplying high-quality animals. Nevertheless, the success of this activity largely depends on the development of nutritionally balanced diets capable of producing excellent gonads. In this study, four extruded diets formulated with low or high protein (30 and 50% dry matter (DM), LP and HP, respectively) and lipid (6 and 11% DM, LL and HL, respectively) levels were fed to wild-caught individuals (4.5 cm diameter) for 15 weeks. Twelve homogeneous groups of 15 individuals were randomly distributed by mesh cages (45 urchins/m2) within 250 L tanks in a recirculating aquaculture system (RAS) at 18 °C and a 12 L:12 D photoperiod regime. Sea urchins fed the LP/LL diet were compared to wild specimens with similar maturation stage.All experimental diets were well accepted by sea urchins and resulted in similar final body weight (42–43 g). No significant differences were observed in specific growth rate or protein efficiency ratio among diets. The HP diets led to a decrease of dry matter and energy intake resulting in the lowest feed conversion ratio (FCR). Weight gain, whole body composition and nutrient gain remained similar among dietary treatments. The gonad somatic index (GSI) varied between sex but was similar among dietary treatments (19–23%) and was higher than values observed in wild specimens (6–7%). Females had significantly higher total concentration of carotenoids than males, irrespectively of the dietary treatments. Dietary treatments and sex did not affect gonad texture (firmness and resilience) or colour parameters (brightness, redness, yellowness, chroma or hue angle), but affected gonad composition. Total carotenoid content in gonads was not affected by diets and resulted in lower values compared to wild specimens. These had higher levels of echinenone, β-cryptoxantin and β-carotene and showed higher redness and firmness values when compared to the LP/LL diet, irrespectively of the sex. Gonad lipid content and n-3 PUFA were higher in female than in male, whilst protein content showed an opposite trend, suggesting some sex related differences in the metabolic use of nutrients.This study clearly shows that it is possible to enhance sea urchin gonad yield in relation to wild animals in a RAS at 18 °C. All diets were effective in promoting gonad growth, but the diet with the lowest protein (30% DM) and lowest lipid (6% DM) level resulted in the highest gonad yield in both sexes.

Androgenic Modulation in the Primary Ovarian Growth of the Japanese eel, Anguilla japonica.

Anguilla japonica seedling production is urgently required for eel aquaculture due to the species' severely dwindling population. This study aimed to understand androgenic modulation of the primary ovarian growth, a critical development phase in females, in this semelparous fish. Through histological analysis, primordial to primary follicle transition was observed before hormone injection, and eels injected with SPH + MT showed greater synchronous follicle development than those injected with SPH alone. An in vivo experiment revealed a positive correlation (p < 0.05, r = 0.94) between the mRNA expression of arα and increasing gonadal somatic index (GSI) < 0.75% before SPH injection. Another positive correlation was seen between arβ expression and GSI (p < 0.05, r = 0.97) after weekly SPH injections for three weeks. fshr expression was high in the SPH + MT-injected group. Significantly high fshr mRNA levels were found after weekly MT injections for two weeks (p < 0.05), whereas the expression levels dropped after flutamide injection. arα and arβ expressions revealed different patterns before and after SPH induction. In this study, androgen modulation was found with regard to ARs expressions during primary growth and the primordial to primary follicle transition prior to hormone induction. This modulation continuously affected fshr expression and vitellogenic development after SPH induction during ovarian growth in the Japanese eel.

A Convenient Alternative Method for Quantifying Endocrine Disrupting Effect of Chemicals Using Secondary Sexual Characteristics of Medaka (Oryzias latipes): The Node Count Method

An efficient and convenient method that effectively quantify the endocrine disrupting effect of chemicals by using secondary sexual characteristics (SSCs) of the S-rR strain medaka (Oryzias latipes) was developed and demonstrated in this study. Gonad somatic index (GSI) and gonadal morphology are the main gross morphological characters in fish used to detect the effects of endocrine disrupters; however, their low sensitivity has been identified as their weakness. The method we proposed in the present study involved counting the number of nodes in the second-last ray of the anal fin, could be an efficient and convenient alternative method to OECD guidelines that require counting all number of papillary processes and joint plates with the papillary processes on every ray of the anal fin. The S-rR strain medaka was exposed to 17β-estradiol at three different concentrations (16, 32, or 64 ng･l-1) for three consecutive generations. Exposure was initiated on fertilized eggs and performed approximately for 70 days for each generation. At the termination of exposure, three characters: number of nodes in the second-last ray, maximum number of papillary processes on a ray, and number of rays with papillary processes, were observed. The results showed that the number of nodes represents a viable quantitative indicator for assessing endocrine disrupting chemicals (EDCs). Furthermore, it was confirmed that the node count method was an efficient and convenient alternative method to OECD guidelines that allows better understanding of the biological significance of the SSCs of medaka.