• The Korean Journal of Malacology
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• v.29 no.2
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• pp.113-120
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• 2013

The reproductive cycle, gonad index, condition index, and the sex ratio in female and male Coecella chinensis, which were collected from the coastal waters of Namhae, the South Coast of Korea, were investigated by histological analysis and morphometric data. Monthly variations of the gonad index and condition index of this species showed similar patterns to that of the reproductive cycle. The reproductive cycle in female and male C. chinensis can be classified into six successive stages: early active stage (April), late active stage (May), ripe stage (June), partially spawned/spent stage (June to August), degeneration stage (August) and inactive stage (September to March). According to monthly changes in relative frequency distributions of ovarian egg diameters of this species, in particular, a number of ripe eggs ranging about 70 ${\mu}m$ appear in June, however, in July and August, although the mode of egg diameters ranging about 50 ${\mu}m$ appear about 80%, these ripe eggs ranging from 60 ${\mu}m$ to 70 ${\mu}m$ are gradually decreased during the period from June to August. Therefore, the spawning period of this species is continued from June to August with a peak between July and August when the seawater temperature exceeds about $24.5^{\circ}C$. The sex ratio of female and male individuals was not significantly different from 1:1 (${\chi}^2$=1.20, p>0.05). No hermaphrodites were found.

• The Korean Journal of Malacology
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• v.20 no.1
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• pp.35-43
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• 2004

To know the effects on temperature and body size on the clearance rate (CR) of a small tidal flat bivalve, Coecella chinensis, laboratory experiments were performed with 20 individuals of different sizes (ranging from 7 to 25 mm) at 3 different temperatures (10, 15, $20^{\circ}C$). The relationship between body size and CR was determined by an allometric equation. The CR of C. chinensis varied greatly ranging from 0.003 to 0.103 L/individual/hr. Both temperature and body size affected significantly on the CR of C. chinensis. The CR at $20^{\circ}C$was 1.5 times higher than that at $15^{\circ}C$ and 2.8 times than $10^{\circ}C$. The temperature coefficient ($Q_10$) between 10 and $15^{\circ}C$ was higher than that between 15 and $20^{\circ}C$, which indicates that C. chinensis changes its CR more rapidly in lower temperature range. As body size increased, the CR increased more than 10-fold at all temperatures. The CR relative to flesh dry weight (FDW) were fitted well to the power function: CR = a ${\times}$ $(FDW)^b$. The exponent value (b) of the fitted equation ranged from 0.64 to 0.70, which are similar to those of other bivalves. The weight-specific CR ($CR_w$) was still affected by body size (p < 0.05). This implies that smaller individuals require more energy per unit biomass for growth, and the energy requirement for growth decreases as body size increases.

• The Korean Journal of Malacology
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• v.30 no.4
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• pp.333-342
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• 2014

Ultrastructural studies of oogenesis in oocytes, oocyte degeneration associated with the follicle cells in female Coecella chinensis were investigated for clams collected from Namhae, Geongsangnam-do, Korea. In this study, vitellogenesis during oogenesis in the oocytes occured by way of endogenous autosynthesis and exogenous heterosynthesis. Of two processes of vitellogenesis during oogenesis, the process of endogenous autosynthesis involved the combined activity of the Golgi complex, mitochondria and rough endoplasmic reticulum. whereas the process of exogenous heterosynthesis involved endocytotic incorporation of extraovarian precursors at the basal region of the oolema of the early vitellogenic oocytes prior to the formation of the vitelline coat. It is assumed that the follicle cells were involved in the development of previtellogenic and early vitellogenic oocytes and appear to play an integral role in vitellogenesis in the early and late vitellogenic oocytes by endocytosis of yolk precursors, and also they were involved in oocyte degeneration by assimilating products originating from the degenerated oocytes, thus allowed the transfer of york precursors needed for vitellogenesis (through phagocytosis by phagolysosomes after spawning). Follicle cells presumably have a lysosomal system for breakdown products of oocyte degeneration. and for reabsorption of various phagosomes (phagolysosomes) in the cytoplasm for nutrient storage during the period of oocyte degeneration.

• Proceedings of the Korean Society of Fisheries Technology Conference
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• 2003.05a
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• pp.391-392
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• 2003

There were many studies on the dependence of clearance rate on temperature and the body size of bivalves (Winter, 1973; Bayne et al., 1976; Yukihira et al., 1998), Most of these studies dealt with relatively large species, especially commercially important species. Studies with smaller but ecologically important species were relative rare(Werner and Hollibaugh, 1993). (omitted)

• Journal of Aquaculture
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• v.10 no.3
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• pp.227-237
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• 1997

Five species of intertidal clams including Ruditapes philippinarum, Tegillarca granosa, Solen strictus, Heteromacoma irus, and Coecella chinensis were tested for the presence of the protozoan parasite, Perkinsus sp. using fluid thioglycollate medium (FTM) fortified with antibiotics and histological techniques. Each individual clam was placed in a test tube filled with 10ml FTM, placed in totally dark place, and incubated over a week. After incubation the clam tissues were stained with Lugol's iodine solution and examined under a light microscope to find out any hypnospores of Perkensus sp. in the tissues. Cross-sections of the clams were also embedded in paraffin, sliced to 3um, and stained with Harry's hematoxylene and Picro eosine to observe the presence of tomont or trophozoites. Perkinsus sp. were found in the presence of tomont or trophozoites. Perkinsus sp. were found in the tissues of R. philippinarum collected from Kangjin and Wando, along the south coast of Korea. However, Perkinsus sp. was not found in four other species of clams nor R. philippinaurm collected from Kimnyong and Waido in Cheju. A size-dependent Perkinsus sp. infection was found in R. philippinarum collected rom Kangjin and Wando the clams smaller than 15mm in shell width do not exhibit and Perkinsus sp. while other clams greater than 20mm in shell width exhibit almost 100% infection. To determine the number of Perkinsus sp. in the clams, FTM cultured clam tissues were digested with 2M NaOH solution and the number of hypnospores in the tube were counted. The number of hypnospores counted from the tissues indicated that each Manila clam contains 100,000 to 3,500,000 Perkinsus cells or 20,000 to 1,000,000 cells per gram tissue wet weight. The results of cell counts also suggests that such a high occurrence of Perkinsus sp. in the clam may cause mortality, as already reported from other studies of Perkinsus spp.

• Parasites, Hosts and Diseases
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• v.59 no.4
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• pp.341-353
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• 2021

Acanthoparyphium shinanense n. sp. (Digenea: Echinostomatidae) is described from chicks experimentally infected with the metacercariae encysted in 2 brackish water clam species, Ruditapes philippinarum and Coecella chinensis, in the Republic of Korea. The metacercariae were round to oval, armed with 23 collar spines, and 0.216 (0.203-0.226) mm in diameter. From 5 chicks experimentally infected each with 200 metacercariae, 34 juvenile (5-day-old worms) and 104 adult flukes (7-day-old worms) were harvested from their small intestines, with the average worm recovery rate of 13.8%. The adult flukes were 3.18 (2.89-3.55) mm long and 0.68 (0.61-0.85) mm wide, with an elongated, posteriorly tapering body, and a prominent head collar armed with 23 collar spines arranged in a single uninterrupted row. The posterior testis of A. shinanense was longitudinally elongated, which is similar to Acanthoparyphium spinulosum Johnston, 1917 but unique from the other closely related species, including Acanthoparyphium tyosenense Yamaguti, 1939, Acanthoparyphium kurogamo Yamaguti, 1939, and Acanthoparyphium marilae Yamaguti, 1934. The eggs of A. shinanense were larger than those of A. spinulosum, and the anterior extent of 2 lateral groups of vitellaria was slightly more limited in A. shinanense than in A. spinulosum. Molecular analysis of nuclear and mitochondrial genes revealed low homology with A. spinulosum from USA (96.1% in 5.8S rRNA) and Ukraine (97.9% in 28S rRNA), Acanthoparyphium n. sp. from USA (98.0% in 28S rRNA), and Acanthoparyphium sp. from Australia, Kuwait, and New Zealand. Biological characteristics, including its first intermediate host and natural definitive hosts, as well as its zoonotic capability, should be elucidated.