• Journal of fish pathology
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• v.34 no.1
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• pp.63-70
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• 2021

As a part of research to elucidate the pathogenesis of so called Soft Tunic Syndrome(STS), that caused mass mortalities in the cultured sea squirts, Halocynthia roretzi, the epidemiological and pathological analysis were done to both clinically normal and diseased groups of the farms of Tongyoung and Geoje coastal areas in southeast sea from February to July, 2008. In the histological finding of the tunic, most of individuals showed tunic softness syndromes that included the disarrangement and destruction of tunic fiber with the simultaneous presence of flagellates-like cells, recently suspected as main agents of tunic softness syndromes. Simultaneously, the intensive degenerative changes of the skeletal muscle of diseased sea squirts were recognized. The changes were characterized with the hyalinization and condensation of muscle fibril and hemocytic infiltration in the muscle fibers. Those were thought to be a kind of typical Zenker's necrosis as in the skeletal muscle of higher vertebrates. Besides of the diseased sea squirts, Zenker's necrosis of skeletal muscles were seen in the normal ones. Epidemiological inquiry for diseased groups revealed that the higher incidences of tunic softness syndrome were recorded in the fast growing groups and in the sites presuming the organic pollution. And Higher malondialadehyde(MDA) and glutathione peroxidase(GPx) activity were detected in the groups showing STS. Those results suggested that Zenker's necrosis of body muscles was a kind of"nutritional myopathy" by oxidative stress. Conclusively, it was considered that Zenker's necrosis of body muscles gives an important clue for elucidating pathogenesis of STS of cultured squirts. And it seems that the necrosis were caused by the oxidative stress to body muscle during abnormal rapid growth of sea squirts.

• Journal of Life Science
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• v.23 no.2
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• pp.190-196
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• 2013

The sea squirt, Halocynthia roretzi, has experienced mass mortality due to softness syndrome. The identification of disease-induced genes can provide insights into the development of this syndrome. To identify the genes, we performed differentially expressed gene (DEG) analysis. The expression of the phosphoglycerate kinase (HrPGK) gene was significantly decreased in diseased sea squirts compared to normal ones. We confirmed the result of the DEG analysis through RT-PCR and real-time PCR. In addition, we detected single nucleotide polymorphisms at position -106 (A/T) and -254 (G/T) in the HrPGK gene promoter by genotyping analysis. At the -106 site of the HrPGK gene, the frequency of the AA allele in disease-resistant sea squirts was about two-fold higher than that of sensitive ones, and the frequency of the TT allele in the disease-resistant sea squirts was about six-fold lower. At the -254 site of the HrPGK gene, the frequency of the GT and the GG allele was approximately two-fold higher and two-fold lower, respectively, in the disease-resistant sea squirts compared to the disease-sensitive ones. Analysis of the relationship between the genotypic variation at the -106/-254 promoter and the expression of HrPGK mRNA showed that HrPGK mRNA expression was higher in the -106/-254 AA/GT genotype samples than in the -106/254 TT/GG genotype ones. These results show that sea squirts harboring the AA/GT genotype may have more resistance to mortality than the sea squirts with other genotypes.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.46 no.1
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• pp.27-36
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• 2013

This study was conducted to develop and characterize sea squirt Halocynthia roretzi sikhae. According to the results for pH, total acidity, lactic acid bacteria, amino nitrogen and sensory evaluation of sea squirt sikhae during fermentation for 6 days at $15^{\circ}C$, the optimum fermentation periods were 4 days for sourness-disliking customers and 5 days for sour-disliking customers. No differences in the proximate compositions of sea squirt sikhaes fermented for 4 days (4D) and for 5 days (5D) were found. There was a difference in the eproximate compositions of commercial seasoned sea squirts, 4D and 5D, sea squirt sikhaes. The results of salinity, total acidity, amino nitrogen and sensory evaluation of two kinds of sikhae suggest that the taste was stronger for 5D than for 4D, both of which were superior to commercial seasoned sea squirts. There was, however, no difference in color of 4D, 5D and commercial seasoned sea squirts. The results of E. coli analyses suggest that sea squirt sikhae is a safe food in terms of sanitation.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.50 no.5
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• pp.494-499
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• 2017

This study evaluated the abundance of fecal coliforms in oysters Crassostrea gigas, sea squirts Halocynthia roretzi and sea cucumbers Apostichopus japonicus in fisheries along the coast of Korea in 2014, and investigated the prevalence of antimicrobial resistance in Escherichia coli isolated from these fishery products. The ranges of fecal coliforms found in oysters, sea squirts and sea cucumbers were <18-20, <18-330 and <18-3,300 MPN (most probable number)/100 g, respectively. Sea squirts contained the greatest range of E. coli (<20-140 MPN/100 g), followed by sea cucumbers (<20-130 MPN/100 g) and oysters (<20-20 MPN/100 g). A total of 26 strains of E. coli were isolated from 34 sea squirt, 25 sea cucumber and 13 oyster samples. Strains thus isolated were tested for their susceptibility to 22 antimicrobial agents used in Korea for medical or veterinary therapy. E. coli isolates showed the greatest resistance to ampicillin (84.6%), followed by trimethoprim (34.6%), nalidixic acid (34.6%), tetracycline (30.8%), pipemidic acid (26.9%), streptomycin (23.1%), chloramphenicol (23.1%), trimethoprim/sulfamethoxazole (23.1%), and gentamicin (15.4%). Resistance to at least one antimicrobial agent was present in 88.5% of E. coli isolates. Of the 26 isolated, six strains (23.1%) were resistant to multiple antimicrobial agents.

• Animal Systematics, Evolution and Diversity
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• v.24 no.1
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• pp.139-142
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• 2008

A lysianassid species, Orchomene japonicus (Gurjanova, 1962) associated with sea squirts collected from Geojedo Island located in the South Sea of Korea, is described and illustrated. Present specimens conform to that of Gurjanova's except some morphological variation in mandibular palp.

• Journal of the Korean Society of Marine Environment & Safety
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• v.13 no.4
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• pp.15-19
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• 2007

Mass mortalities of the farmed sea squirt, Halocynthia roretzi, occurred in August, 2006 along the Gyeongbuk coasts of the East Sea without any pathological symptom. Suspecting the No. 10 typhoon, Wukong, which had passed over the relevant locations in the middle of August, 2006 as a culprit of the mortalities, we compared water temperature stratifications of the affected coasts before and after the typhoon. Just prior to the typhoon, cold waters lower than $15^{\circ}C$ were stratified at depths deeper than 10m probably by a persisting upwelling of cold bottom waters. The typhoon enforced water off-coast waters into coasts for 5 days, replacing the cold waters at depths $10{\sim}20m$ which can be justified by Ekman Spiral Effect. The results were an increment of water temperature by $10^{\circ}C$ and more at depths where sea squirts were suspended. The sudden elevation of water temperature might drive the sea squirts under abnormal stress to mass mortality.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.47 no.1
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• pp.1-11
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• 2014

This study was carried out to investigate nutritional and physiologically active characterizations of sikhae and the seasoned products from the sea squirt Halocynthia roretzi. The total taste values of sikhae fermented for 4 and 5 days were 10.9 and 15.4, respectively, which was lower than for commercially seasoned sea squirts. The sikhaes contained mostly glutamic and aspartic acids. The total amino acid contents of sikhaes fermented for 4 and 5 days were 5.5 and 6.0 g/100 g, respectively, which were lower than those of commercial seasoned-sea squirts or similar. An amount of 100 g of sikhae and its seasoned products contained P, K, Mg and Fe, and these minerals, which are deemed good for our health, were at 10% above the recommended daily requirements. The functional properties of sikhae fermented for 4 and 5 days were as follows: for ACE inhibiting activity, 69 and 69.5%, respectively; for antioxidative activity, 28.9 and 29.3%, respectively; for xanthine oxidase inhibitory activity, 52.8 and 53.1%, respectively; and for ${\alpha}$-glucosidase inhibitory activity, 2.4 and 1.4%, respectively. Antimicrobial activity of the 5 day fermented sikhae against Vibrio parahaemolyticus and Staphyloccus aureus was detected in 8 mm and in 7 mm against Escherichia coli.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.44 no.5
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• pp.516-523
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• 2011

To compare four populations of sea squirt Halocynthia roretzi adults, their egg quality and larval development were investigated in the hatchery. The populations were: south sea wild (SSW), south sea cultured (SSC), east sea wild (ESW) and Iwate Japan cultured (IJC). Egg quality and larval development were compared using 13 factors (fertilization rate and diameter, proximate composition, amino acid and fatty acid contents of eggs, hatching rate and various sizes of tadpole larvae) which were obtained from each population. Fertilized egg diameter, hatching rate and size of tadpole larvae were significantly different among the four populations (P<0.05). Eggs were produced with higher crude protein ($5.20{\pm}0.00%$ SSW, $4.71{\pm}0.01%$ ESW, $4.66{\pm}0.01%$ SSC and $3.96{\pm}0.01%$ IJC) and lipid ($1.22{\pm}0.01%$ ESW, $1.01{\pm}0.00%$ SSW, $0.77{\pm}0.01%$ SSC and $0.69{\pm}0.00%$ IJC,) contents from domestic wild populations than from Japanese or cultured populations. Also amino acid and fatty acid contents were different. The extent of similarity between domestic and Japanese populations (30.5% IJC:SSW, 34.3% IJC:SSC and 40.7% IJC:ESW) was relatively low but was very high between SSW and SSC (73.9%). These results may have been due to differences in the abundance of food types and environmental conditions in the four localities and consequent differences in the diets of the sea squirts.

• Journal of Aquaculture
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• v.3 no.1
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• pp.49-63
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• 1990

A population ecological study was carried out to estimate survival and growth rates, biomass, biological production and turnover ratio of cultured sea squirt, Halocynthia roretzi, by growth stages, using data from in situ culture experiment off Hansando in the southern part of Korea from February 1985 to July 1986. The squirt population followed an exponential decay function and the instantaneous coefficient of total mortality (Z) was estimated to be 0.0614 $month^{-1}$(Var (Z) = 0.000126). Growths in total weight and meat weight of squirts were expressed as linear functions during the period of culture experiment. The growth of squirts showed a negative correlation with the water temperature. The mean biomass per string ranged from 2.14 kg for March of the first year to 16.26 kg for March of the next year. The biological production per string was estimated to range from 3.28 kg for the first summer (June - July) to 6.46kg for the first late winter (February-March). The peak of turnover ratio occurred in the late winter (February-March) as 3.013 and the ratios sharply declined thereafter. Based on the results of this study, management implications for culturing sea squirts were also suggested. The optimum harvest time ($t_{mb}$) when the peak biomass in terms of total weight occurred was estimated to be late June of the second year, which corresponded to 16.7 months after the main hanging. However, the time when the peak biomass in terms of meat weight was occurred was early July of the second year. The maximum harvest biomass was 17.4 kg per string in terms of total weight and 6.3 kg per string in terms of meat weight. In conclusion, the process of culture should be conducted on the basis of the knowledge of population ecological theories as shown in this study.

• Fisheries and Aquatic Sciences
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• v.22 no.5
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• pp.11.1-11.8
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• 2019

Background: In the present study, the skin-whitening effects of a marine-sourced mixture that includes a fucoidanrich extract of Undaria pinnatifida (UPEF), a phlorotannin-rich extract of Ecklonia cava (ECE), and glycosaminoglycans (GAGs) from sea squirt skin were investigated. Methods: The whitening effects of the mixture and its components were evaluated by measuring the inhibition of mushroom tyrosinase and melanin synthesis in alpha-melanocyte-stimulating hormone (${\alpha}$-MSH)-stimulated B16F10 melanoma cells. Results: Each component alone markedly inhibited mushroom tyrosinase in a dose-dependent manner, and in ${\alpha}$-MSH-stimulated B16F10 cells, they inhibited melanin synthesis and were cytotoxic. However, the whitening effects of UPEF, ECE, and GAGs in combination were greater than those of each component alone. A mixture in the ratio of 4:5:1 (UEG-451) showed the strongest activity without cytotoxicity. Further study suggested that UEG-451 inhibits ${\alpha}$-MSH-stimulated melanogenesis in B16F10 cells by downregulating tyrosinase and tyrosinase-related proteins, such as TRP-1 and TRP-2, via the inhibition of MITF expression. Conclusions: These results suggest that mixing the different components at optimum ratios might be an effective way to improve their bioactivities and reduce toxicity and that UEG-451 possesses strong whitening effects that could be used in the cosmetic industry.