• Proceedings of the Zoological Society Korea Conference
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• 1997.10b
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• pp.110.1-110
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• 1997

• Proceedings of the Korean Society of Embryo Transfer Conference
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• 2002.11a
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• pp.37-42
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• 2002

In ascidians, a primitive chordate, maternal cytoplasmic factors and inductive interactions are involved in the specification of cell fate in early embryos. The larval structure of ascidians is relatively simple, and the major mesodermal tissues of the tadpole larva are notochord, muscle and mesemchyme. Formation of muscle cells is a cell-autonomous process, and localized maternal macho-1 mRNA specify muscle fate in the posterior marginal zone of the early embryo. In contrast, inductive influence from endoderm precursors plays important roles in the specification of notochord and mesenchyme fates. FGF-Ras-MAPK signaling is involved in the induction of both tissues. The difference in responsiveness of the posterior mesenchyme and anterior notochord precursors is caused by the presence or absence of the posterior-vegetal egg cytoplasm, respectively. In these cases, directed signal may polarizes the responding cells and cause asymmetric cell divisions that operate in both the anterior and posterior regions.

• Proceedings of the Zoological Society Korea Conference
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• 1996.10a
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• pp.80.1-80
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• 1996

No Abstract, See Full Text

• Animal Systematics, Evolution and Diversity
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• v.16 no.1
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• pp.39-53
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• 2000

The ascidians specimens were collected from Tangsa and its adjacent waters in Korea by scuba divers during the period from 1994 to 1999. They were identified into 30 species which are reported for the first time in Tangsa. Out of them one species, Molgula hozawai, was turned out to be new to the Korean fauna, and six species, such as Eudistoma illotum, Symplegma connectans, Boltenia trasversaria, Microcosmus nultitentaculatus, Pyura squamata and Molgula hozawai, were newly recorded in Chundo Island and Geojedo Island, which are influenced by warm waters of the Kuroshio Current.

• Proceedings of the Zoological Society Korea Conference
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• 1997.10b
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• pp.89.1-89
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• 1997

No Abstract, See Full Text

• Journal of fish pathology
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• v.7 no.2
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• pp.83-94
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• 1994

Bonnierilla namhaesius n, sp, is described based on the specimens recovered from the ascidians, Halocynthia roretzi Von Drasche in Namhae Islands, Korea, This is distinguished from congeners by having a combination of characters : setal formula 3, 17+1 hook, 9+1 aesthete, 5, 3, 2, 2+1 aesthete, 7+1 aesthete respectively on eight segments of antennule, II, 5 on distal segment of the second leg to fourth leg exopod, and 2, 3, I on distal margin of caudal ramus. This is the second record of the male, and first record of the copepodid in the genus Bonnierilla.

• Journal of Microbiology and Biotechnology
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• v.15 no.3
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• pp.665-671
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• 2005

Initiation and activation of sperm motility are prerequisite processes for the contact and fusion of male and female gametes at fertilization. The phenomena are under the regulation of cAMP and $Ca^{2+}$ in vertebrates and invertebrates. Mammalian sperm requires $Ca^{2+}$ and cAMP for the activation of sperm motility. Cell signaling for the initiation and activation of sperm motility in the ascidians and salmonid fishes has drawn much attention. In the ascidians, the sperm-activating and attracting factors from unfertilized egg require extracellular $Ca^{2+}$ for activating sperm motility and eliciting chemotactic behavior toward the egg. On the other hand, the cAMP-dependent phosphorylation of protein is essential for the initiation of sperm motility in salmonid fishes. A decrease of the environmental $K^+$ concentration surrounding the spawned sperm causes $K^+$ efflux and $Ca^{2+}$ influx through the specific $K^+$ channel and dihydropyridine-sensitive L-/T-type $Ca^{2+}$ channel, respectively, thereby leading to the membrane hyperpolarization. The membrane hyperpolarization induces synthesis of cAMP, which triggers further cell signaling processes, such as cAMP-dependent protein phosphorylation, to initiate sperm motility in salmonid fishes. This article reviews the studies on the physiological mechanisms of sperm motility and its cell signaling in aquatic species.

• Animal Systematics, Evolution and Diversity
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• v.38 no.4
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• pp.167-198
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• 2022

Ten species of copepods, including nine new species, associated with compound ascidians are recorded from Korean waters. Nine new species can be characterized by their major diagnostic features, as follows: Botryllophilus pentamerus n. sp. by having a five-annulated abdomen; B. paucisetatus n. sp. by the presence of four and three setae on the exopods of right and left leg 1, respectively; Haplostoma quadridens n. sp. by the presence of four lobes on the labrum and one seta plus four spines on the exopods of legs 1-4; H. paucidens n. sp. by the presence of only two spines on the distal segment of the antenna; Enterocola horridus n. sp. by having five setae on the antenna, no seta on the caudal ramus, and two setae on leg 5; E. longicaudatus n. sp. by having long caudal rami which are more than three times as long as wide; Thoracodelphys bisetata n. sp. by the presence of only two setae on the basis of the maxillule; T. cerasta n. sp. by the presence of a large, horn-like process on the distal margin of the basis of leg 2; and Unimeria hirsuta n. sp. by having three setae on the terminal segment of the maxilla. Zygomolgus didemni (Gotto, 1956) previously known only from European waters is reported from Korean waters, with a redescription and illustrations.

• Fisheries and Aquatic Sciences
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• v.20 no.7
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• pp.12.1-12.7
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• 2017

Soft tunic syndrome (STS) is a protozoal disease caused by Azumiobodo hoyamushi in the edible ascidian Halocynthia roretzi. Previous studies have proven that combined formalin-hydrogen peroxide ($H_2O_2$) bath is effective in reducing STS progress and mortality. To secure target animal safety for field applications, toxicity of the treatment needs to be evaluated. Healthy ascidians were bathed for 1 week, 1 h a day at various bathing concentrations. Bathing with 5- and 10-fold optimum concentration caused 100% mortality of ascidians, whereas mortality by 0.5- to 2.0-fold solutions was not different from that of control. Of the oxidative damage parameters, MDA levels did not change after 0.5- and 1.0-fold bathing. However, free radical scavenging ability and reducing power were significantly decreased even with the lower-than-optimal 0.5-fold concentration. Glycogen content tended to increase with 1-fold bathing without statistical significance. All changes induced by the 2-fold bathing were completely or partially restored to control levels 48 h post-bathing. Free amino acid analysis revealed a concentration-dependent decline in aspartic acid and cysteine levels. In contrast, alanine and valine levels increased after the 2-fold bath treatment. These data indicate that the currently established effective disinfectant regimen against the parasitic pathogen is generally safe, and the biochemical changes observed are transient, lasting approximately 48 h at most. Low levels of formalin and $H_2O_2$ were detectable 1 h post-bathing; however, the compounds were completely undetectable after 48 h of bathing. Formalin-$H_2O_2$ bathing is effective against STS; however, reasonable care is required in the treatment to avoid unwanted toxicity. Drug residues do not present a concern for consumer safety.

• KSBB Journal
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• v.21 no.3
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• pp.194-198
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• 2006

Dried raw Ascidians(Halocynthia roretzi) shells harvested from fish farms in southern coast area in Korea were used to extract ${\beta}$-carotene using supercritical carbon dioxide($SCO_2$) and with ethanol as a co-solvent at the range of temperatures and pressures, from 25 to $65^{\circ}C$ and 100 to 350 bar respectively. The size of the dried Ascidians shells was around $850{\mu}m$. The system used this study was a semi-batch flow type high pressure unit. The efficiency of ${\beta}$-carotene extraction using $SCO_2$ with and without co-solvent, ethanol, influenced to pressure and temperature changes. The highest solubility of ${\beta}$-carotene in $SCO_2$ was 1.35 mg/g for ${\beta}$-carotene at $35^{\circ}C$ and 350 bar. With addition of 2(v/v%) ethanol the recovery of ${\beta}$-carotene was 93%. As a result of using n-hexane and methanol for rinse, at $35^{\circ}C$ and 350 bar the amount of ${\beta}$-carotene by methanol rinse was 5 times higher than that of n-hexane rinse.