• Korean Journal of Environmental Biology
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• v.41 no.3
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• pp.298-307
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• 2023

The annual reproductive cycle of two species, Upogebia major (de Haan 1841) and Austinogebia wuhsienweni (Yu 1931), of the female mud shrimp from the west coast of Korea was investigated using histology. The collected samples were divided into adult and juvenile groups to understand the mature period of age class based on the carapace length(CL). Juvenile Upogebia(CL<25mm) were mostly inactive gonad with early (62%-100%) and late (10%-38%) development stages during the year, whereas the adult shrimp showed a seasonal pattern of gonad maturation(CL≥25 mm). The early and late developmental stages of oocytes were observed in adult Upogebia from November to March and mature eggs appeared from April to October. In adult Ausitnogebia (CL≥15 mm), fully grown oocytes were consistently observed during the study period, in which the ripe stage was found between January and June. On the other hand, most juvenile Austinogebia (CL<15 mm) maintained an immature state in the gonad. Both species of the mud shrimp reproduced from ovigerous females in the adult population and their egg-bearing period was distinguished from January to April for U. major and from July to September for A. wuhsienweni.

• Fisheries and Aquatic Sciences
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• v.4 no.4
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• pp.208-218
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• 2001

We have investigated the gonad index (GI), gonadal development, reproductive cycle, first sexual maturity, sex ratio, the number of spawned eggs and spawning frequency of the Manila clam, Ruditapes philippinarum. Samples were collected from the intertidal zone of Komso Bay, Korea from January to December in 1999. Monthly changes in the gonad index (GI) and condition index showed a similar pattern in the reproductive cycle. The spawning period was once a year between early June and early October, there was a spawning peak between July and August when seawater temperature was over $20^{\circ}C$. The reproductive cycle of this species can be categorized into five successive stages; early active (February to March), late active (April to May), ripe (April to August), partially spawned (June to October), and spent/inactive stage (August to March). Percentages of first sexual maturity of female and male clams of l5.1-20.0mm in shell length were $56.3\%$ and $60.0\%$, respectively, and $100\%$ for the clams >25. mm. The sex ratio of individuals >15.1 mm in shell length was about 1:1 $(\chi^2= 0.02,\;p>0.05)$. Number of the eggs released from each clam by the induction increased as the size of clam in terms of shell length increased. Mean number of the eggs from the second induction of the spawning was $75.35-84.30\%$ $(average\;79.81\%)$ of the number of the eggs released in the first spawning. Our data indicated that R. philippinarum in Komso Bay has one major spawning peak with over two minor spawning, and the interval of each spawning was estimated to be approximately 15-17 (average 16.5) days.

• Journal of Aquaculture
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• v.21 no.4
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• pp.252-258
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• 2008

Gonadal development and reproductive cycle of the ark shell Scarpharca subcrenata were investigated by histological observations. Samples were collected monthly from March 2007 to February 2008 in the Yeoja Bay, Yeosu, Jeollanam-do, Korea. S. subcrenata was dioecious. The gonads consist of a number of oogenic follicle and acinus. Monthly changes in the gonad index reached a maximum in June and a minimum in September. Monthly changes in the condition index reached a maximum in April and a minimum in September. The reproductive cycle of this species can be divided into five successive stages: early active stage (January to April), late active stage (March to June), ripe stage (May to August), spent stage (July to September) and recovery and resting stage (September to March). The main spawning of S. subcrenata occurred in July and August in Yeoja Bay. The sex ratio of female to male was not significantly different from 1:1.

• The Korean Journal of Malacology
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• v.16 no.1_2
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• pp.35-41
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• 2000

We investigated the gonad index (GI), gonadal development, the reprodutive cycle and first sexual maturity of the venus clam, Cyclina sinensis by histological observation. Samples were collected from the intertidal zone of Komso Bay, Chollabuk-do, west coast of Korea, from April 1998 to March 1999. This clam is dioecious and oviparous. Monthly changes in the gonad index (GI) showed a similar pattern to the reproductive cycle. Ripe oocytes are about 90-100 ㎛ in diameter. The spawning period was between early July to September, and the main spawning occurred between July and August when the sea water temperature was over 20$\^{C}$ The reproductive cycle of this species can be divided into five successive stages: early active stage (February to April), late active stage (March to June), ripe stage (April to August), partially spawned stage (July to October), and spent / inactive stage (September to February). Percentages of first sexual maturity of female and male clams measuring 26.1-30.0 ㎜ in shell length were 53.3% and 62.5%, respectively, and 100% for the clams > 41.0 ㎜. It is assumed that both sexes begin reproduction at about two years age.

• Journal of the Korean Society of Food Science and Nutrition
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• v.22 no.3
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• pp.291-299
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• 1993

The lipid components of the gonad of sea urchin Hemicentrotus pulcherrimus, ark shell Scapharca bro-ughtonii and "Gaebul" (Korea name, a worm) Urechis unicinctus were investigated. The total lipid (TL) contents of the sea urchin, the ark shell and the "Gaebul" were 6.10, 0.67 and 0.79%, respectively. The percentages of phospholipid (PL) in TL were higher in the "Gaebul"(72.4%) and ark shell(64.9%) compared to the sea urchin (41.7%). The major lipid classes of PL were phosphatidylcholine and phosphatidylethanolamine, and the former was rich in the sea urchin (56.2%) and the latter in the "Gaebul"(34.4%). In the class of non-polar lipid (NL), the major lipid classes were different from species ; the sea urchin was rich in triglyceride(TG, 89.0%), the ark shell rich in TG (69.2%) and cholesterol (ST 26.8%) and the "Gaebul"rich in ST (70.7%). The prominent fatty acids of the sea urchin were 16 : 0, 14 : 0, 20 : 5n-3, 20 : 4n-6 and 20 : 4n-6 and 20 : 2NMID(non-methylene interupted dien). The percentage of 20 : 4n-6 was the highest of the investigated invertebrates, accounting for 19.8% in PL, but 22 : 6n-3 was not detected in the sea urchin. In case of the ark shell, the prominent fatty acids were 16 : 0, 18 : 0, 20 : 5n-3, 22 : 6n-3 and 22 : 2NMID, especially 22 : 6n-3(9.58%) was richer compared to that of the "Gaebul". The prominent fatty acids of the "Gaebul"were 20 : 5n-3, 16 : 0, 18 : 0 20 : 1n-9, 16 : 1n-7 and 14 : 0. The percentage of 20 : 5n-3 (22.0%) was highest in the PL of the "Gaebul"among the three invertebrates. These differences in the lipid components of all the sample is considered to be due to the different food habits and environmental condition of the invertebrates.

• Journal of Aquaculture
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• v.8 no.4
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• pp.327-341
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• 1995

A Study was conducted by using a histological method to examine gonadal development in diploid and triploid mud loach, Misgurnus mizolepis. Shape of ovaries from both groups looked like a single mass however, size of triploid ovary was significantly smaller than that of diploid ovary. Testis of triploid was also similar that of diploid in shape, but it was smaller than that of diploid. Ovarian development and oogenesis in diploid were significantly more rapid than those process in triploid, and first matured eggs were observed 100-days after hatching (SL, 5.68cm). Triploid ovary from hatching to 9-month-old had external appearance of undeveloped gonad and a few of oocytes of perinucleolus stage. However, normal matured eggs like those of female diploid were observed in one 5year-old triploid fish ovary examined. Although testicular development and sperrnatogenesis of diploid were prosperous sexually, testicular development of triploid were rather retarded compare to their male diploid counterpart in spermatogenesis.

• Journal of Aquaculture
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• v.13 no.3
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• pp.245-251
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• 2000

Carapace width (CW) of main size class of the snow crab was 70~90 mm for females and 80~100 mm for males. The CW holds a stronger relation with body weight than that of carapace length (CL). The number of eggs attached to the pleopods was in the range of 35,000 and 114,000 eggs in crabs with 65 and 88 mm CW, respectively). The logistic maturity curve on morphometric measurements and gonad examination, defined by the presence of egg brooding in wide abdomen of the female and spermatophores inside the vasa deferentia of the male indicated that 50 % of crabs attained gonadal maturity at 54.2 mm and 58.8 mm CW for females and males, respectively. In the relationship between CW and body weight, a sharp break at 53~55 mm CW indicates that morphological changes associated with maturity have occurred.

• Ocean and Polar Research
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• v.27 no.3
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• pp.351-358
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• 2005

Reproductive condition of the tropical blacklip pearl oyster, Pinctada margaritifera collected during the period July through September 2003 from Chuuk Lagoon, Federated State of Micronesia was investigated using histology. The level of gonad development for each pearl oyster was determined with an average score of five microscopic fields, and the average score was used as the maturity index (ML). All wild pearl oysters collected in July did exhibit fully ripe eggs in their ovaries ($45{\sim}50{\mu}M$ in diameter), indicating that they were ready for spawning. In mid August most wild pearl oysters were in spawning and M1 dropped dramatically from mid- to late September, suggesting that the wild pearl oyster completed spawning during this period. In contrast, the cultivated pearl oysters collected in mid-September held ripe eggs in the ovaries and only a few of them spawned, indicating that gonad maturation of the cultivated pearl oyster was somewhat slower than that of the wild pearl oyster in Chuuk Lagoon during the summer period. Histological analysis also indicated that spawning of the pearl oyster is rather incomplete and they may spawn continuously during summer.

• Journal of Animal Reproduction and Biotechnology
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• v.35 no.3
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• pp.279-288
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• 2020

Changes of gonadal morphology and mRNA expression patterns of vitellogenin were investigated in Siberian sturgeon Acipenser baerii (Chondrostei) during its early gonadal maturation period. Early differentiations and morphological transitions of both ovaries and testes appeared to occur actively until the age of 3 years, however from then on, the maturation patterns to full maturity were largely gender-dependent, in which males showed a faster progression of maturation than did females while females experienced a steady-state progress with a lagged interval before entering the final maturation. Expression of vitellogenin mRNAs are closely correlated with transitional patterns of gonadal appearances. In both females and males, hepatic mRNA levels of vitellogenin exponentially increased in the earliest interval (up to 1-year-old). However, in subsequent periods, vitellogenin expression in females continued to increase with age, whereas in males, the expression stabilized at a younger age. Nevertheless, at the age older than or equal to 7-year-old, fully matured individuals showed a quite low level of vitellogenin expression in both females and males. Collectively, results from this study could be useful as a fundamental guideline to address the gonad maturation of this sturgeon species, which is helpful for making practical decisions about farming practices and management for caviar production on local sturgeon farms.

• Fisheries and Aquatic Sciences
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• v.23 no.2
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• pp.3.1-3.8
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• 2020

Background: The IGF system plays important roles in controlling growth, development, reproduction, and aging of organisms. Methods: To estimate maturation of the Pacific oyster Crassostrea gigas, we investigated the expression of insulin-like growth factor (IGF) system components and sex-specific genes. To determine the role of the IGF system in the growth and spawning period of female and male oysters, we examined mRNA expression levels of the C. gigas insulin receptor-related receptor (CIR), IGF binding protein complex acid labile subunit (IGFBP_ALS), and molluscan insulin-related peptide (MIP), as well as those of vitellogenin (Vg) and receptor-type guanylate cyclase (Gyc76C) in gonads of C. gigas collected between April and October, when sex can be determined visually in this species. Results: We found that MIP, IGFBP_ALS, and CIR mRNA expression levels were dependent on sex and month and were greater in males than in females. CIR and Vg mRNA expression levels were very similar among females, whereas IGF system components and Gyc76C were very similarly expressed among males. The highest expression values were observed in May, when oysters are mature; CIR and Vg mRNA expression levels were highest in females, and those of MIP, IGFBP_ALS, CIR, and Gyc76C were highest in males. Interestingly, we observed a 1:1 proportion of females to males during this period. Conclusion: Our results suggest that IGF system components, as well as Vg and Gyc76C, are associated with sexual maturation in C. gigas.