Group-synchronous Oocyte Development Research Articles

Aspectos reprodutivos das fêmeas de Leporinus lacustris Campos, 1945 (Characiformes, Anostomidae) em uma planície de inundação Neotropical

Abstract: Aim This study evaluates the reproduction and fecundity of Leporinus lacustris in upper Paraná River floodplain environments with the objectives to (i) recognize the germ cells of folliculogenesis and oogenesis; (ii) characterize reproductive phases; (iii) investigate oocyte diameter and evaluate if this species has group synchronous or asynchronous oocyte development and if spawning is total or batch; (iv) estimate batch fecundity; (v) establish the relationship between fecundity/ovary weight, standard length, and total weight; (vi) verify the reproductive areas of this species in the upper Paraná River floodplain. Methods Sampling was carried out using gillnets in rivers, and open and closed lagoons, in March, June, September, and December 2013, 2014, 2015, 2016, 2018, and 2019 and March and September 2017. A total of 442 females were sampled and 111 subsampled, each of which had an ovary removed and fixed in Bouin solution. A subsample of 20 ovaries in the spawning capable phase were fixed in a 4% buffered formaldehyde solution to estimate the diameter of the oocytes and fecundity. The ovaries were dehydrated, embedded in historesin, cut, stained, and evaluated as regards folliculogenesis, oogenesis, development phases, and reproduction areas. Results The germ cells recorded were differentiated oogonia, primary and secondary growth oocytes, fully-grown and mature oocytes, and post-ovulatory follicles that permitted the recognition of the reproductive phases. Oocyte diameter information revealed that the species has group synchronous oocyte development, determinate fecundity and batch spawning, and eliminates an average of 38,490 oocytes. Conclusions The fact that Leporinus lacustris is reproductively successful in the Baía River and in the Fechada, Guaraná, Patos, Garças, Ventura and Ressaco do Pau Véio lagoons strengthens the importance of the areas of environmental protection of the islands and lowlands of the Paraná River, Ilha Grande National Park and Ivinheima River State Park.

Can the Life History Trait Divergence of Two Extremes of a Cold-Water Genus Distribution Offer Evidence for Their Vulnerability to Sea Warming?

Cold- and deep-water species such as Molva species show low resilience to anthropogenic pressures, and they become particularly vulnerable at the warm edges of their distribution. In this study, the poorly documented Mediterranean ling (Molva macrophthalma) population from the northwestern Mediterranean Sea was analysed. This area is considered a cul-de-sac in a sea-warming hotspot, where M. macrophthalma shows a low population health status and is experiencing a climate-related reduction in abundance. Several life-history traits (length at maturity, reproductive cycle, fecundity style, oocyte recruitment pattern, and breeding strategy) are here described for the first time to evaluate the reproductive performance (oocyte diameter and production) in relation to the fish condition status (the HSI and relative condition index). Additionally, the results are compared with those of a population of a similar species, the blue ling (Molva dypterygia), inhabiting the cool edge of its distribution, hypothesised to have a higher condition status. Our results indicate that M. macrophthalma is a capital breeder with restricted secondary growth recruitment and group-synchronous oocyte development. In relative terms, the stressed southern M. macrophthalma exhibited a worse condition, a lower investment in reproduction, a smaller size at maturity, larger but fewer primary growth oocytes, and a smaller size-standardized production of secondary growth oocytes than the northern M. dypterygia. Significant differences in the secondary growth oocyte recruitment were also found. These findings reinforce the environment’s role in shaping the reproductive potential and condition status. Altogether, this study suggests high sensitivity to anthropogenic pressures for both species, and, especially for Mediterranean ling, it shows the importance of introducing monitoring and conservation measures to ensure the sustainability of its populations.

Reproduction and Maturation of Sea Bass, Lateolabrax japonicus, after Transportation from Net-Cages to Indoor Tanks.

To determine whether the reproductive processes of sea bass, Lateolabrax japonicus, proceed normally after transportation from an outdoor net-cage into indoor tanks, we examined changes in the gonadosomatic index (GSI), histological gonadal tissue, and plasma levels of sex hormones (testosterone and estradiol-17ß) during their annual reproductive cycle. We also measured maturation and spawning across two sea water salinity levels (full and low salinity). Fecundity was estimated by the relationship between egg number and body size in female sea bass. Monthly changes in the GSI, histological gonadal tissues, and oocyte size showed both male and female sea bass reach final maturation in January and February, respectively, indicating that the spermiation of males occurs earlier than the spawning of females. The histological results indicated that the sea bass is a multiple spawner, similar to many marine teleosts, exhibiting group-synchronous oocyte development. Female maturation and spawning were enhanced in lower salinity seawater (29.6-31.0 psu) compared to that of normal salinity (34.5-35.1 psu). These results confirm that sea bass reproduction can occur successfully in captivity and imply that fertilized eggs can be collected from February to March. Additionally, our results show that lower salinity enhances oocyte maturation and spawning of female sea bass.

Assessing effects of aromatase inhibition on fishes with group-synchronous oocyte development using western mosquitofish (Gambusia affinis) as a model

Exposure to certain anthropogenic chemicals can inhibit the activity to cytochrome P450 aromatase (CYP19) in fishes leading to decreased plasma 17β-estradiol (E2), plasma vitellogenin (VTG), and egg production. Reproductive dysfunction resulting from exposure to aromatase inhibitors has been extensively investigated in several laboratory model species of fish. These model species have ovaries that undergo asynchronous oocyte development, but many fishes have ovaries with group-synchronous oocyte development. Fishes with group-synchronous oocyte development have dynamic reproductive cycles which typically occur annually and are often triggered by complex environmental cues. This has resulted in a lack of test data and uncertainty regarding sensitivities to and adverse effects of aromatase inhibition. The present study used the western mosquitofish (Gambusia affinis) as a laboratory model to investigate adverse effects of chemical aromatase inhibition on group-synchronous oocyte development. Adult female western mosquitofish were exposed to either 0, 2, or 30 μg/L of the model nonsteroidal aromatase inhibiting chemical, fadrozole, for a complete reproductive cycle. Fish were sampled at four time-points representing pre-vitellogenic resting, early vitellogenesis, late vitellogenesis/early ovarian recrudescence, and late ovarian recrudescence. Temporal changes in numerous reproductive parameters were measured, including gonadosomatic index (GSI), plasma sex steroids, and expression of selected genes in the brain, liver, and gonad that are important for reproduction. In contrast to fish from the control treatment, fish exposed to 2 and 30 μg/L of fadrozole had persistent elevated expression of cyp19 in the ovary, depressed expression of vtg in the liver, and a low GSI. These responses suggest that completion of a group-synchronous reproductive cycle was unsuccessful during the assay in fish from either fadrozole treatment. These adverse effects data show that exposure to aromatase inhibitors has the potential to cause reproductive dysfunction in a wide range of fishes with both asynchronous and group-synchronous reproductive strategies.

Condition and reproductive strategy of the Argentina sphyraena, a cold-water species in the Mediterranean Sea

We evaluate the condition and reproductive status of the lesser silver smelt, Argentina sphyraena in the north-western Mediterranean Sea. We describe for the first time several life history traits of this species, i.e. condition, reproductive cycle, fecundity, breeding strategy, oocyte recruitment and egg quality, and evaluate the links between these traits. We also contrast condition and reproduction parameters in two study areas with different environmental conditions: the Gulf of Lion and the Balearic Sea. Our results indicate that A. sphyraena is a capital breeder with group-synchronous oocyte development and determinate fecundity. Energy requirements for reproduction are mostly met by lipids stored in the mesentery which is the main fat deposit and a good indicator of condition; this means that condition can be estimated visually and easily using a fat scaling technique. Our results show that, in terms of condition and reproduction, this species performs better in the colder and more productive Gulf of Lion than in the warmer and less productive Balearic Sea, as evidenced by the amount of stored energy and reproductive strategy. These findings suggest that suboptimal environmental conditions may have a negative impact on the condition and reproduction strategy of cold-water species, which will ultimately affect their abundance and distribution.

Life history traits of a poorly known pelagic fish, Aethotaxis mitopteryx (Perciformes, Notothenioidei) from the Weddell Sea

Amongst the nototheniid subfamily Pleuragramminae, Aethotaxis mitopteryx is an infrequently collected high Antarctic species with an array of morphological and physiological adaptations supporting an evolutionarily derived benthopelagic lifestyle. The present study deals with some poorly known life history traits of this species, counting on 79 specimens collected in the Weddell Sea during 2014 and 2015 austral summer. Annulation pattern in sagittal otoliths were used to assess population age structure and growth rate, while macroscopic and histological analyses of gonads were performed to estimate reproductive status and features of gametogenesis. The sex ratio of the sampled population was close to parity, with females significantly larger than males. Based on the von Bertalanffy growth model, females attained a larger maximum size (40 vs. 27 cm) at a lower rate (0.05 vs. 0.12 years−1) than males. Individual longevity was remarkable in both sexes, females and males attaining 62 and 32 years of age, respectively. Females showed group synchronous oocyte development and presumed high reproductive effort, as indicated by the large size of residual hydrated oocytes in regressing individuals (4.6–4.8 mm). Body sizes at sexual maturity were 33 and 19 cm in females and males, corresponding to 32 and 11 years of age, respectively. All specimens were caught far from the reproductive season. From an evolutionary perspective, it appears that the process of pelagization similarly influenced the life strategies of the species within the clade Pleuragramminae, which shared high reproductive effort linked to early sexual maturity, slow somatic growth and long life span.

Reproductive characteristics of northern pike, Esox lucius (Actinopterygii: Esociformes: Esocidae), in the Anzali Wetland, southwest Caspian Sea

Background. Temporal variability in fish reproductive features is influenced by environmental and spatial variations. Given the wide distribution of northern pike, Esox lucius Linnaeus, 1758, in the northern hemisphere, important reproductive features such as the initiation of the spawning activity are likely to vary with latitudinal gradients. The overall goal of the presently reported study was to answer basic questions regarding the reproductive biology of the pike and to discuss changes in the timing of the onset of spawning activity in relation to geographical locations and the water temperature in the Anzali Wetland compared to higher latitudes. Materials and methods. Monthly samples (537 specimens in total) were collected from the Anzali Wetland (southwest of the Caspian Sea) from July 2012 through July 2013. Samples were macro- and microscopically examined, and their maturity stages were identified, so that spawning season, monthly distribution of maturity stages, oocytes development, spawning strategy, length at 50% maturity, and fecundity were estimated. Results. The gonadosomatic index, oocyte size-frequency distribution, and histological examination suggested a relatively short spawning season, from February through March. The short annual spawning period and the oocyte size-frequency distribution demonstrated that pike is a total spawner with group synchronous oocyte development. The length at 50% maturity was 28.5 and 33.9 cm FL for males and females, respectively. Absolute fecundity values ranged from 4423 to 48471 oocytes, with mean (± standard error) of 16481 ± 2705 oocytes and the relative fecundity was estimated as 26.9 ± 1.6 oocytes per gram of mature female. Conclusion. The most important findings of this study are: the earlier initiation and relatively shorter duration of the reproductive activities of pike in the south Caspian region compared to northern geographical regions. The results emphasize the need for specific management strategies based on seasonal measures for pike such as: fish size limits, limitation of catches during the spawning season, limitation of the boat number, and closure of the spawning area during spawning months.

Aspects of reproductive biology of wild-caught polar cod (Boreogadus saida) from Svalbard waters

Polar cod (Boreogadus saida) is considered a key species in the Arctic marine ecosystems. Yet detailed or even basic knowledge regarding its biology and adaptations, especially during the polar night, is in many cases poor. Data are presently unavailable in Western literature on the gonad development of polar cod and its reproductive biology in wild specimens. Accordingly, gonad development of wild-caught polar cod from fjords of the Svalbard archipelago was studied across seasons (April, August, September, November and January). Histological analyses of polar cod showed strong indication of a group-synchronous oocyte development with determinate fecundity and iteroparity. Females started gonadal development prior to April and had not yet reached the final stage of maturation in January. Testes matured more rapidly, with males ready to spawn in January. Furthermore, our data show that polar cod were able to reach sexual maturity at age 1+. Based on our data and previous reports, we hypothesise that polar cod is a total spawner.

Reproductive biology of Black Anglerfish (Lophius budegassa) in the northwestern Mediterranean Sea

Gonadal morphology and reproductive biology of the Black Anglerfish (Lophius budegassa) were studied by examining 4410 specimens collected between June 2007 and December 2010 in the northwestern Mediterranean Sea. Ovaries and testes presented traits common among fishes of the order Lophiiformes. Spawning occurred between November and March. Size at first maturity (L50) was 33.4 cm in total length (TL) for males and 48.2 cm TL for females. Black Anglerfish is a total spawner with group-synchronous oocyte development and determinate fecundity. Fecundity values ranged from 87,569 to 398,986 oocytes, and mean potential fecundity was estimated at 78,929 (standard error of the mean [SE] 13,648) oocytes per kilogram of mature female. This study provides the first description of the presence of 2–3 eggs sharing the same chamber and a semicystic type of spermatogenesis for Black Anglerfish. This new information allows for a better understanding of Black Anglerfish reproduction—knowledge that will be useful for the assessment and management of this species.

Reproductive condition and ovarian atresia in the common kilka (<i>Clupeonella cultriventris</i>) from the Caspian Sea years after a dramatic outbreak of the comb jelly fish (<i>Mnemiopsis leidyi</i>)

SUMMARY: To assess the reproductive condition of the common kilka, Clupeonella cultriventris, the somatic condition and reproductive characteristics were studied by histological analysis. A total of 800 specimens from the Bandar Anzali coast on the Caspian Sea were sampled. The gonadosomatic index (GSI) for females and males attained maximum values in May in the first period of sampling and in March-April in the second period, suggesting temporal variations in spawning activity. The pattern of oocyte frequency distribution demonstrated that the common kilka is a batch spawner with group-synchronous oocyte development. The estimated relative batch fecundity was 6718 oocytes g–1. A low level of atresia (4.7%) during the spawning season showed that this species was in optimal somatic condition. This weakens the hypothesis that abundance of the ctenophore (Mnemiopsis leidyi) in the Caspian Sea, as a food rival for kilka, influences the body condition and subsequently the reproductive capability of this species.

Some aspects of reproductive biology of Gobius paganellus (Gobiidae) on the north-eastern coasts of Tunisia (Bizerta lagoon)

The rock goby, Gobius paganellus one of the most common gobiid fish in Bizerta lagoon (north-east of Tunisia), is a gonochoric species that belongs to the Gobiidae family. This study provides the first detailed information of its reproductive biology in lagoon environments. Gobius paganellus was sampled monthly from January 2005 to December 2006 involving 1486 specimens. Total length distribution ranged between 38 and 125 mm. The maximum recorded total lengths were, respectively, 122 mm and 125 mm for female and male. Over the entire population, the sex-ratio was unbalanced in favour of females. According to months, a predominance of females sex-ratio was recorded during the spawning period while according to body size, males were dominating among larger size-classes. In both sexes, the variation of the gonadosomatic index (GSI) was independent of size. Macroscopic and microscopic examination of the gonads added to the monthly monitoring of gonadosomatic index and hepatosomatic index showed that gonads development begins in October and spawning period extends from December to March. The cyclic pattern of gonads development was determined by histology. Results indicated that G. paganellus exhibits a group-synchronous oocyte development. The sizes of first sexual maturity related to 50% of mature individuals were 78.3 mm (CI95: 77–84 mm) for males and 79 mm (CI95: 75–85 mms) for females. The discussion part underlined the impacts of some environmental factors and antropization of this lagoon on sexual cycle of G. paganellus.

Seasonal and Tidally Driven Reproductive Patterns in the Saltmarsh Topminnow, Fundulus jenkinsi

Fundulus jenkinsi is recognized federally and within a number of northern Gulf of Mexico states as a Species of Concern. Little is known about its life history, but a detailed reproductive histology study of F. jenkinsi can provide the foundation needed to quantify reproductive parameters in this rare species in need of conservation. Monthly gonadosomatic index (GSI) of male and female F. jenkinsi indicated a spawning season from April through August. However, ovarian histological analysis suggested March through August was a more accurate spawning season. The multiple oocyte stages within F. jenkinsi in the spawning capable reproductive phase indicates batch spawning, similar to other members of its family. Many estuarine members of the family Fundulidae exhibit a semilunar spawning pattern, yet the oocyte composition of ovaries of F. jenkinsi suggested spawns occur multiple days around the time of spring tides both within a population and on the individual level. Spawning did not occur on neap tides, and no late secondary growth vitellogenic oocytes (SGl) were found in the majority of females captured during neap tide. The lack of SGl oocytes in females during the spawning season suggests the necessity for establishing a new sub-phase within the spawning capable phase, termed the redeveloping sub-phase. This new sub-phase is applicable to other batch spawning species with group synchronous oocyte development. This work contributes to a better understanding of the importance of intertidal saltmarsh habitat to F. jenkinsi, as spawning intensity appears to increase with tidal height and marsh inundation.

Differences in female individual reproductive potential among three stocks of winter flounder, Pseudopleuronectes americanus

Potential annual fecundity (PAF) and skipped spawning of winter flounder, Pseudopleuronectes americanus, were compared among the three stocks in United States waters and between two spawning seasons. Winter flounder have group-synchronous oocyte development and determinate fecundity. These characteristics enable estimation of PAF just prior to spawning by enumeration of the late-vitellogenic cohort of oocytes, in this case employing the autodiametric method. There was a low level of down-regulation, which was limited to fish in the earlier stages of vitellogenesis. Estimates of PAF increased substantially with female size and age, ranging from <0.5million to >5million eggs per female. Fecundity at size decreased with increasing latitude. On average, fish from the Southern New England (SNE) stock had the highest individual fecundities at length and Gulf of Maine (GOM) the lowest, but differences varied among the years. Fecundity at length of fish from Georges Bank (GB) was intermediate to these two stocks and displayed less variability at size; however, GB fish grow faster so they had the highest relative fecundity at age. Skipped spawning also exhibited geographic differences; it was infrequent (<2%) overall, but observed in the two coastal stocks (GOM more than SNE) in both years and was not observed in the GB stock. Fecundity at size between the two years was more similar for SNE fish, but all three stocks were synchronized with higher PAF in 2011 than 2010. Comparisons to previously published estimates suggest fecundity is highly variable in this species. Overall, different rates of reproductive productivity exist among individuals of the three stocks.

Population structure and reproductive patterns of the NW Mediterranean deep-sea macrourid Trachyrincus scabrus (Rafinesque, 1810)

Macrourid fish are one of the most abundant marine species on continental margins worldwide. Although they play an important role in the ecosystem, little is known about their overall biology. We report here a large data set of the most abundant macrourid in Mediterranean waters, Trachyrincus scabrus, showing the main population and reproductive characteristics. The study was based on 3,239 specimens collected between 300 and 1,500 m depth on the northwestern Mediterranean in 2003–2004 and 2008–2009. The population showed a depth-related structure with the largest individuals at 1,100 m depth and the smallest (i.e., immature) at shallower depths. Macroscopic and microscopic analyses of the gonads showed that T. scabrus has a highly seasonal reproductive pattern. Spawning females were found during winter when the organic matter fluxes were highest on the continental slope. T. scabrus is a batch spawner with group-synchronous oocyte development and present low average fecundity of 14,191 oocytes.

Profiles of sex steroids, fecundity, and spawning of the curimatã-pacu Prochilodus argenteus in the São Francisco River, downstream from the Três Marias Dam, Southeastern Brazil

The present study evaluated for the first time sex steroid profiles and fecundity in females of Prochilodus argenteus from two sections of the São Francisco River Brazil, downstream from the Três Marias Dam, which influences characteristics of their water habitat. The model species in the study, P. argenteus, is an important commercial and recreational species in Brazil. In the region closest to the dam (section 1), females did not reach final oocyte maturation, failed to spawn, and displayed lesser circulating concentrations of testosterone, 17(-hydroxyprogesterone (17(-P) and 17β-estradiol (E2) than those farther downstream of the dam (section 2). The endocrine and fecundity deficiencies probably are attributed to lower water temperature and oxygen concentration in (section 1). The follicular atresia rate in the region closest to the dam (26%) was greater than those fish captured farther downstream of the dam (13%), after the Abaeté River (section 2). Variations in testosterone, E2 and 17(-P concentrations in section 2, followed gonadal maturation which are typical features of species which have seasonal reproduction, group-synchronous oocyte development, and are single batch spawners such as P. argenteus. Results document the first evidence of endocrine and reproductive dysfunctions caused by inadequate water conditions in a wild population of the migratory species P. argenteus in the São Francisco River, downstream from the Três Marias dam.

Fecundity estimation of Atlantic cod ( Gadus morhua) and haddock ( Melanogrammus aeglefinus) of Georges Bank: Application of the autodiametric method

Haddock, Melanogrammus aeglefinus (L.), and Atlantic cod, Gadus morhua (L.), are species of major commercial interest in the Northwest Atlantic and their spawning strategy is characterized by group-synchronous oocyte development and determinate fecundity. Recent advances in image analysis systems and the development of the autodiametric method have led to rapid assessment and accurate estimation of the annual egg production of an individual or its potential fecundity. In this study we estimated the corresponding autodiametric calibration curves for Atlantic cod and haddock of Georges Bank and used these to estimate potential fecundity of these two species near the southern limits of their geographic distribution. In addition, we explored the relationships between potential fecundity and different condition indices for these populations and found the hepatosomatic index to significantly increase the explanatory power of the fecundity–length relationship which is in agreement with previous studies on the influence of nutritional state on egg production.

A review of spawning induction, larviculture, and juvenile rearing of the fat snook, Centropomus parallelus

The fat snook, Centropomus parallelus, is a commercially valuable marine fish species with potential for aquaculture. This paper describes the development of technology for mass production of fat snook juveniles at the Experimental Fish Hatchery of the Universidade Federal de Santa Catarina, focusing on research about reproduction, larviculture, and juvenile rearing. Induced spawning of wild fat snook was first achieved in 1991 with a single injection of human chorionic gonadotropin (hCG). There was a substantial increase in egg quality when broodstock was conditioned in maturation rooms and induced to spawn. Different dosages of luteinizing hormone-releasing hormone analogue (LHRHa) with saline injection and colesterol implant were also tested. As fat snook exhibits group-synchronous oocyte development, females could be induced to spawn (with 35-50 mug kg(-1) of LHRHa) once a month, resulting in up to four consecutive spawnings. Results of larval culture were highly variable at the beginning; survival rates were frequently around 1% until the juvenile stage. Several experiments were conducted to evaluate the effect of environmental factors and feeding quality on survival and growth. With the improvement of the spawning induction technique and better larviculture practices, survival rates increased to 10-30%. Studies on the particular requirements of juveniles in terms of stocking density, feeding, nutrition, and environmental factors were also performed in order to improve growth rates and feed utilization. The present study demonstrates the feasibility of mass production of fat snook juveniles. However, further research is needed to develop cost-effective grow-out technology.

Broodstock condition, egg morphology and lipid content and composition during the spawning season of captive striped trumpeter, Latris lineata

The striped trumpeter, Latris lineata, is a pelagic marine fish found in southern Australia that is currently being developed as an aquaculture species. Striped trumpeters are multiple spawners with group synchronous oocyte development and spawn in the wild from late winter to early spring. By shifting light and temperature regimes, it is possible to manipulate broodstock to spawn in captivity outside of their normal ambient season. Broodstock condition, egg morphology and biochemistry were examined over a spawning season for three groups of broodstock held under ambient or photothermal-manipulated (PTM) conditions. Using a Torry Fish Fatmeter the muscle fat of male and female striped trumpeter broodstock held under ambient conditions was found to decrease over a season by 25% and 40%, respectively. Five general trends were observed in eggs spawned during both ambient and PTM seasons. First, overall egg volume remained unchanged. Second, the egg oil droplet volumes decreased to < 80% of those measured at the start of the spawning season. Third, there was a decrease in the triacylglycerol (TAG) fraction of egg total lipid and a concomitant increase in the proportion of polar lipid (PL). Fourth, the relative proportions of egg monounsaturated fatty acids (MUFA) decreased over a breeding season, probably as they were depleted because of the energy requirements of vitellogenesis. Fifth, proportions of the essential fatty acids (EFA), 20:4n-6 (arachidonic acid, ARA), 20:5n-3 (eicosapentaenoic acid, EPA) and 22:6n-3 (docosahexaenoic acid, DHA) was typical of marine fish eggs (1.8%, 10.1% and 20.9% of total fatty acids, respectively), and remained unchanged or were elevated in eggs over a season. Data suggest that holding broodstock under PTM or ambient conditions results in similar temporal changes in egg biochemistry, albeit more truncated during the PTM season. Despite ongoing feeding by striped trumpeter during spawning, the total energetic cost of vitellogenesis results in a depletion of lipid in the muscle that is in turn reflected in egg biochemistry. Finally fatty acid requirements for striped trumpeter larvae determined during the live feeding period are not too dissimilar from average egg fatty acid profiles, supporting the theory that egg values can provide a basis for estimating dietary requirements.

흰점독가시치 (Siganus canaliculatus)의 생식소 발달 및 생식주기

Annual reproductive cycle of Siganus canaliculatus was studied based on monthly variation of gonadosomatic index (GSI) and histological changes of gonads. Samples were monthly collected by a set net along the southern coast of Jeju Island, Korea from January to December, 1996. Variation of the monthly mean GSI values showed similar trends in female and male. The GSI values increased from June and reached a peak in the spawning season in July <TEX>$(9.65{\pm}1.96\;in\;females,\;10.00{\pm}4.27\;in\;males)$</TEX>, and decreased rapidly thereafter. Female hepatosomatic index (HSI) values ranged from <TEX>$1.26{\pm}0.22\;(in\;April)\;to\;2.34{\pm}0.39$</TEX> (in July), and male HSI values ranged from <TEX>$1.27{\pm}0.21\;(in\;April)\;to\;1.87{\pm}0.30$</TEX> (in October). Annual reproductive cycle was classified into the following successive stages: in female, growing stage (from February to June), mature stage (from June to July), ripe and spawning stage (from July to August), recovery stage (from August to March); and in male, growing stage (from January to June), mature stage (from June to July), ripe and spent stage (from July to August), and recovery stage (from August to April). Based on these data, this species has a group-synchronous oocyte development and one spawning season a year.

Ovary maturation stages and oocyte features in three species of the neotropical fish Hemiodus (Müller, 1842)

Macro- and microscopic ovarian features of Hemiodus microlepis, H. ternetzi and H. unimaculatus were analyzed. Based on these features we proposed an ovarian maturation scale. The nine stages of the preliminary macroscopic fieldwork scale were reduced to five after microscopic analysis of ovaries. The microscopic analysis indicated a group-synchronous oocyte development common to the three species that were characterized as iteroparous synchronous spawners with a total spawning type. The remarkable thickness of the zona radiata layer and the large size of vitellogenic oocytes of Hemiodus ternetzi distinguished this species from the others.