• Animal cells and systems
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• v.5 no.1
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• pp.37-44
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• 2001

Gonadal development, reproductive cycle, gonad index, meat weight rate, and first sexual maturity of the top shell, Omphalius rusticus were Investigated monthly by histological observations. Specimens were collected from the west coast of Korea during the period from January to December in 1999. O. rusticus is dioecious and oviparous. The gonad is widely situated on the surface of the digestive g1and located in the posterior spiral meat part in the shell. The ovary and the testis were composed of a number of oogenic follicles and several spermatogenic follicles, respectively. Ripe oocytes were approximately 120-130 $\mu$m in diameter. The meat weight rate peaked in June (27.7%), and then rapidly decreased in September (19.5%). Monthly changes in the gonad index in both sexes reached the maximum in June, and then sharply decreased in September. Percentages of first sexual maturity of female and male snails ranging from 9.0 to 9.9 mm in shell heights were 58.3% and 54.5%, respectively, and 100% in those over 11.0 mm in both sexes participated in reproduction. Reproductive cycle of this species can be categorized into five successive stages: in females, early active (October to April), late active (December to June), ripe (April to September), spawning (July to September) and recovery (September to January): in males, early active (November to March), late active (December to June), ripe (April to September), spawning (July to September) and recovery (September to December). Gonadal development, gametogenesis, reproductive cycle, and spawning were closely related to the seawater temperature.

• Development and Reproduction
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• v.25 no.3
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• pp.145-155
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• 2021

Reproductive cycle of the blue-striped angelfish, Chaetodontoplus septentrionalis were histologically investigated. Fish were monthly collected in the coastal waters of Munseom, Seogwipo, Jeju-Island from February to December 2018. The gonadosomatic index (GSI) increased from May and maintained high values in August. The reproductive cycle of female fish can be classified by the characteristics observed during gonadal development as followed: growing stage (November to June), early mature stage (May to June), mature and spawning stage (June to September), and degenerative and recovery stage (September to December). In the male, testicular development period was similar to that of ovarian development period, but mature and spawning period was one month longer from June to October. Fecundity of mature female ranged from 4,601 to 22,840 and was correlated positively with total length and body weight. The histological analysis of gonadal development indicated that the C. septentrionalis was summer-spawning type and is considered a multiple spawner during spawning season.

• Development and Reproduction
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• v.15 no.3
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• pp.257-263
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• 2011

Gonadal development and reproductive cycle of Aplysia kurodai inhabiting the coastal waters of Jeju Island, Korea were investigated based on monthly changes of gonadosomatic index, gametogenesis, and developmental phases of ovotestis. A. kurodai was simultaneous hermaphrodite; the ovotestis generally embedded in the posterior dorsal surface of the brownish digestive gland. The ovotestis is composed of a large number of follicles, and both oocytes and sperm are produced in the same follicles. In the sampling periods, the adult A. kurodai population have characteristic of seasonal pattern present during only 10 months. The reproductive cycle can be grouped into the following successive stages in the ovary: inactive (December to February), active (December to April), mature and spawning (April to September). The gonadal development of A. kurodai coincided with rising temperature, and spawning occurred from April to September, when the temperature was high. The histological observations of the ovotestis suggested that this species have a single spawning season that extend over six months.

• Development and Reproduction
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• v.10 no.1
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• pp.33-39
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• 2006

Gonadal development and reproductive cycle of the North Pacific seastar, Asterias amurensis captured from the Gosung, Gyeongsangnamdo, between November 2003 and February 2005, was investigated monthly changes of gonadosomatic index(GSI), gonadal development and oocyte size-frequency distribution. Monthly changes of GSI values showed similar trends in female and male. GSI values were reached the maximum in March($3.88{\pm}3.04$ in female, $0.87{\pm}0.57$ in male), and then gradually decreased. Based on the monthly changes of GSI, histological observation of gonadal development, reproductive cycle was divided into following successive stage: growing stage(October to January), mature stage(February to March), spent stage(March to April), degeneration and resorption stage(April to May), recovery stage(July to September). based on these result, this species seemed to have a synchronous oocyte development and one spawning season a year.

• Development and Reproduction
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• v.17 no.4
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• pp.353-361
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• 2013

The objective of this study was to characterize the reproductive cycle of the chameleon goby, T. trigonocephalus. Gonadal development was investigated using a histological method. Specimens were collected monthly, from April 2009 to March 2010. The gonadosomatic index (GSI) of females began to increase in April, reaching the maximum in May, and declined sharply in August. In males, the GSI began to increase in April and reaching the maximum in July. The annual reproductive cycle of T. trigonocephalus can be divided into four successive stages in females: the growing (November-March), maturing (April-May), ripe and spawning (June-July), and recovery (August-October) stages. Males passed through growing (November-March), maturing (April-June), ripe and spermiation (July-August), and recovery (September-October) stages. These results indicate the spawning season is from June to July. The relationship between fecundity (Fc) and body length (BL) was $Fc=86.1511BL^{2.6506}$. Fecundity was ranged from 3,448-9,654 eggs in a BL of 4.8-7.2 cm and it was increased as BL increased.

• Fisheries and Aquatic Sciences
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• v.2 no.2
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• pp.142-148
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• 1999

Monthly changes in the gonad index (GI), egg-diameter composition, gonadal development, reproductive cycle of the ark shell, Scapharca subcrenata, were investigated by histological method and morphometric data. This species is dioecious and oviparous. The gonad is located among the subregion of mid-intestinal gland, digestive diverticula and the outer fibromuscular layers compacted by the fibrous connective tissues and muscle fibers. The gonad index sharply increased in May, reached the maximum value in June, and then gradually decreased from July to December. The reproductive cycle of this species can be divided into six successive stages: early active stage (January to May), late active stage (June to July), ripe stage (June to August), partially spawned stage (July to September), degenerative stage (August to December), and resting stage (January to April). S. subcrenata spawns once a year between July and early September, and the main spawning occurred between July and August when the water temperatures were above $20^{\circ}C$. This evidence suggest that timings of maturation and spawning are closely related to water temperatures. Even though the spawning period was once a year, it is assumed that the number of spawning frequencies (broods) may occur more than twice during the spawning season.

• Animal cells and systems
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• v.3 no.4
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• pp.375-383
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• 1999

Gonadal development, gametogenesis, reproductive cycle, and first sexual maturity of Reishia clavigera were investigated monthly from July 1998 to June 1999 through cytological and histological observations. R. clavigera had separate sexes, and was an internal fertilizer. The ma1e penis was located near the two tentacles. The ovary and testis were composed of a great number of oogenic lobules and spermatogenic tubules, respectively. The size of ripe oocyte ranged from 130 to 140 ${\mu}$m in diameter. The peripheral cytoplasm of the germinal vesicle of the ripe oocyte in many cases were surrounded by smaller yolk granules, while the eccentric cytoplasm was occupied with larger ones. The reproductive cycle of R. clavigera could be classified into five successive stages: early active, late active, ripe, spawning, and recovery. Spawning of females occurred from early July to August when the seawater reached above 24.8$^{\circ}C$. Spawning of males occurred from early June to August in the water above 22.8$^{\circ}C$. Minimum size for sexual maturity of both sexes was above 10.0 mm in shell height. Each egg capsule was a cylinder or spindle in shape, 4-6 mm in length and 1-2 mm in width. Colors of newly spawned egg capsules showed yellowish white or pale yellow, while those with veliger larvae showed pale black, and released larvae or dead egg capsules showed black violet. The fecundity in an egg capsule ranged from 70 to 91 eggs (mean＝80.28 eggs).

• Korean Journal of Fisheries and Aquatic Sciences
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• v.41 no.4
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• pp.253-260
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• 2008

Gonadal development, gametogenesis, reproductive cycle, spawning, relative weight of flesh, and onset of sexual maturity of the murex shell, Ceratostoma rorifluum, collected from the rocky intertidal zone of Daehang-ri, Buan-gun, Jeollabuk-do, Korea were investigated monthly from January to December 2005 both cytologically and histologically. The gonads were widely placed on the digestive gland located in the posterior spiral fleshy part in the shell. C. rorifluum had separate sexes, and was an internal fertilizer. The sex ratio of females to males was approximately 1:1. The ovary and testis contained a great number of oogenic follicles and spermatogenic tubules, respectively. The oogonia and fully ripe oocytes were $15-19{\mu}m$ and $150-160{\mu}m$ in diameter, respectively, and the cytoplasm of the ripe oocytes contained a number of yolk granules. The relative weight of flesh reached a maximum in August($39.35{\pm}0.40%$), and then decreased rapidly in November($32.75{\pm}1.20%$). The percentages of female and male snails at first sexual maturity with shell heights ranging from 12.1-14.0 mm were 60.0% and 52.9%, respectively, while 100% of the snails of both sexes with shell heights over 18.1 mm were reproductively active. Based on the gonadal development and histological observations, the reproductive cycle of the snail could be categorized into five successive stages: early active(December to May), late active(March to July), ripe(June to September), spawning(July to October), and recovery(October to March). C. rorifluum spawned once a year between July and October, and the majority of spawning occurred in September when the seawater temperature exceeded $23.5^{\circ}C$.

• Journal of Aquaculture
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• v.20 no.4
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• pp.212-218
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• 2007

Reproductive biology (sexual maturity and reproductive cycle) of starry flounder Platichthys stellatus were examined by histological methods. From March 2004 to February 2005, 144 females and males were sampled. Gonadosomatic index (GSI) of female and male were peaked in May and February, respectively. Monthly changes of hepatosomotic index (HSI) showed a negative correlationwith those of the GSI. Changes of condition factor (CF) in female were correlated with gonad maturation, while that of male were no difference all the year round. Based on monthly GSI and gonadal development the reproductive cycle of starry flounder could be divided into four stages: growing stage (September to November), maturation stage (September to February), ripe and spent stage (March to May), and recovery and resting stage (June to August). Biological minimum size of female was 1,074 g. The relationship between fecundity (F) and body weight (BW) of the fish was expressed as $F\;=\;455.86BW^{1.2006}$.

• Development and Reproduction
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• v.27 no.3
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• pp.101-115
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• 2023

Environmental factors impact oyster growth, condition, and gonadal development, which is linked to gamete characteristics observed through histology. The reproductive cycle of bivalves is related to energy storage and utilization. Therefore, in this study, the year-round growth change and gonadal development of oysters were observed using histological analysis, and the biochemical composition changes were confirmed. The oysters used in this study are being nurtured in Gadeok-do, and 40 oysters were randomly sampled monthly from March 2021 to February 2022. Result of histological analysis of gonads, oysters were showed early development from December to February, late development from March and April, mature and ripe from May to July, spawned from August to October, and spent from November to December. Condition index values of oysters decreased in summer and autumn and increased again when entered the spent after spawning. The protein content of oysters was high in May, the maturity period, and the lipid content decreased during the spawning period. In addition, EPA and DHA, the major fatty acids of oysters, were low during the spawning period and high during the maturation period. As a result, this study suggested a close relationship between changes in oyster growth, biochemical composition, and the reproductive cycle.