• Korean Journal of Fisheries and Aquatic Sciences
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• v.45 no.5
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• pp.480-485
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• 2012

The hemocytes of the tunicate Halocynthia roretzi are classified into six types based on their size, cellular form, and fine structure of the cytoplasmic granules: hyalinocytes, granulocytes, phagocytes, nephrocytes, morula cells, and multi-vacuole cells. Based on cell size, they are ordered multi-vacuole cells ($7.5{\mu}m$)>nephrocytes ($7.1{\mu}m$)>phagocytes ($6.8{\mu}m$)>granulocytes ($6.1{\mu}m$)>morula cells ($5.7{\mu}m$)>hyalinocytes ($5.4{\mu}m$). The proportion of hemocytes is ranked in the order multi-vacuole cells (54.8%)>nephrocytes (16.9%)>granulocytes (9.9%)>morula cells (8.8%)>phagocytes (6.1%)>hyalinocytes (3.5%).

• Journal of Aquaculture
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• v.20 no.4
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• pp.226-231
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• 2007

We investigated survival and osmolarity, oxygen consumption, amonia extetion and filtration rates associated with physiological responses of the tunicate Halocynthia roretzi salinity changes. Acclimation times for osmolatity in different salinities took $20{\sim}26$ hours in 60% SW (19.8 psu) and $20{\sim}25$ hours in 80% SW (26.4 psu), while their times took $7{\sim}8$ hours in 110% SW (36.3 psu). Accordingly, acclimation times for high salinities were faster than those for low salinities. Survival (%) was more than 80% at salinity over 26.4 psu, and 6 $days-LS_{50}$ was 25.4 psu. physiological responses such as oxygen consumption, amonia excretion and filtration rates of H. roretzi showed more clear reactions in the longer exposure period (four days after exposure) than that in the beginning of the exposure. To sum up the results, the tunicate might be stressed from the beginning of the exposure in low salinity.

• Proceedings of the Korean Aquaculture Society Conference
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• 2006.05a
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• pp.457-458
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• 2006

• Fisheries and Aquatic Sciences
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• v.20 no.7
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• pp.14.1-14.8
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• 2017

In this study, marine tunicate Styela clava hydrolysate was produced by an environment friendly and green technology, pressurized hot water hydrolysis (PHWH) at different temperatures ($125-275^{\circ}C$) and pressure 50 bar. A wide range of physico-chemical and bio-functional properties such as color, pH, protein content, total carbohydrate content, reducing sugar content, and radical scavenging activities of the produced hydrolysates were evaluated. The appearance (color) of hydrolysates varied depending on the temperature; hydrolysates obtained at $125-150^{\circ}C$ were lighter, whereas at $175^{\circ}C$ gave reddish-yellow, and $225^{\circ}C$ gave dark brown hydrolysates. The $L^*$ (lightness), $a^*$ (red-green), and $b^*$ (yellow-blue) values of the hydrolysates varied between 35.20 and 50.21, -0.28 and 9.59, and 6.45 and 28.82, respectively. The pH values of S. clava hydrolysates varied from 6.45 ($125^{\circ}C$) to 8.96 ($275^{\circ}C$) and the values were found to be increased as the temperature was increased. The hydrolysis efficiency of S. clava hydrolysate was ranged from 46.05 to 88.67% and the highest value was found at $250^{\circ}C$. The highest protein, total carbohydrate content, and reducing sugar content of the hydrolysates were found 4.52 mg/g bovine, 11.48 mg/g and 2.77 mg/g at 175, and 200 and $200^{\circ}C$, respectively. Hydrolysates obtained at lower temperature showed poor radical scavenging activity and the highest DPPH, ABTS, and FRAP activities were obtained 10.25, 14.06, and 10.91 mg trolox equivalent/g hydrolysate (dry matter basis), respectively. Therefore, S. clava hydrolysate obtained by PHWH at $225-250^{\circ}C$ and 50 bar is recommended for bio-functional food supplement preparation.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.4
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• pp.404-410
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• 2021

Although, mouse bioassay for the monitoring of azaspiracids (AZAs) toxins in shellfish has been used previously, the reported method has low sensitivity and it is time-consuming. Recently, there is an interest in the quantitative analysis of AZAs using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The purpose of this study is to verify the simultaneous analysis of AZAs in shellfish and tunicate in Korea using LC-MS/MS. To validate the method, linearity, limit of detection (LOD), limit of quantification (LOQ), precision, accuracy, and repeatability were determined. All standard compounds were analyzed within 7 min. The correlation coefficients (R²) of the standard solution was higher than 0.9995 (within the range of 0.8-10.0 ㎍/L). The LODs and LOQs of AZAs in shellfish were 0.08-0.16 ㎍/kg and 0.23-0.50 ㎍/kg, respectively. The accuracy and precision of the method for determining AZAs in shellfish were 87.1-93.0% and 1.23-4.91%, respectively. Consequently, the verified LC-MS/MS method is suitable to analyze AZAs in shellfish and tunicates in Korea.

• Animal Systematics, Evolution and Diversity
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• v.39 no.1
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• pp.10-15
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• 2023

Two pelagic thaliacean tunicates, Pyrosoma atlanticum and Cyclosalpa quadriluminis, with bioluminescent organ, were collected from Jejudo Island and Korea Strait. In this study, the Pyrosomatida, which is holoplanktonic colonial tunicate with ascidiozooids embedded in a common test, and to which P. atlanticum belongs, is reported for the first time in Korea. The Cyclosalpa in the Salpida has a bar-shaped alimentary canal beside the branchial bar in both oozooids and blastozooids. Cyclosalpa quadriluminis is added to make Cyclosalpa species in Korea from four to five (C. affinis, C. bakeri, C. polae, C. sewelli, and C. quadriluminis). As a result of this study, 27 species of thaliaceans have been reported from Korea.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.41 no.4
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• pp.237-242
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• 2008

The tunic of Styela clava(SCT) consists of a proteoglycan network. Regenerated cellulose films were prepared by solution casting and coagulation of SCT in N-methylmorpholine-N-oxide(NMMO)/$H_2O$(87/13 wt%). The crystalline structure of powdered SCT was primarily that of cellulose I. The crystalline structure of SCT films exhibited a cellulose II structure, similar to that of viscose rayon. Physical characterization of SCT films and fibers revealed an intrinsic viscosity($\eta$) of 6.35 dL/g, average molecular weight($M_w$) of 423,000 g/M, and fiber density of 1.50 $g/cm^3$ with a moisture regain and water absorption of 10.20% and 365%, respectively. The results were similar to those of cellulose films regenerated from wood pulp. Films prepared with 6 wt% SCT exhibited strong tensile strength, high water absorption, and a greater degree of elongation. Scanning electron micrographs(SEM) of film cross-sections showed a layered, sponge-like structure.

• Korean Journal of Environmental Biology
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• v.35 no.1
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• pp.1-5
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• 2017

A native species to the European ocean, the tunicate Ciona intestinalis now appears worldwide, from sub-Arctic to tropical regions. C. intestinalis generally occurs as an opportunistic fouling organism on artificial substrates in harbors or aquaculture. This study focused on estimating the early growth pattern of C. intestinalis under various temperature conditions. Adults were collected from the Guryungpo harbour in November 2016, and their artificially inseminated eggs were used for the study. The growth of the C. intestinalis was investigated at 8 constant temperatures, ranging from $12^{\circ}C$ to $26^{\circ}C$, at 30 psu. Results indicate that the growth of C. intestinalis increased with increasing temperature. The growth was sluggish at $12^{\circ}C$, and decreased at $26^{\circ}C$. The optimal temperature for growth of C. intestinalis was therefore estimated to be between $20^{\circ}C$ and $24^{\circ}C$.

• Ocean and Polar Research
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• v.41 no.4
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• pp.251-263
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• 2019

We investigated the mesozooplankton community structure during autumn in the southern Yellow Sea. Mesozooplankton density generally ranged from 352 to 2,954 ind. m^-3 and varied according to different sampling stations. The copepod Paracalanus parvus s.l. and its copepodites dominated in the communities, corresponding to 57.3% in density of the total. Surface and water-column averaged salinity were positively correlated with density of total mesozooplankton, copepods and a few dominant species, and the tunicate Thalia rhomboides was negatively related to chlorophyll-a concentration. The mesozooplankton community of the study area was divided into three groups according to the cluster analysis using species composition and density: one in the northern coastal region, another in the northern offshore region, and the other in the south. The most significant indicator species for each of the groups were Labidocera euchaeta in the northern coastal region, T. rhomboides in the northern offshore region, and Themisto sp. juveniles in the south. This study provides recent data on the characteristics of the mesozooplankton community in the southern Yellow Sea, which may be valuable for gaining a better understanding of changes in the pelagic ecosystem of the Yellow Sea.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.2
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• pp.174-180
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• 2020

The mouse bioassay has been used widely for the monitoring of paralytic shellfish toxins (PSTs) in many countries. However, this method shows low sensitivity and high limit of detection (LOD), as well as it cannot confirm toxic profiles. Recently, LC-MS/MS method was studied for the quantitative of PSTs, however, the method has any problems with unstable retention times by ionization suppression caused by high salt concentration in shellfish extracts. To establish an alternative method for PSTs analysis, we tried to original LC-MS/MS methods adding desalting operation using amorphous graphitized polymer carbon solid-phase extraction cartridges. The method validation was conducted to determine linearity, limit of detection, limit of quantification (LOQ), accuracy, and precision in quantifying PSTs. The correlation coefficients for all tested PSTs maintained over 0.999. The LODs and LOQs for all PSTs were about 0.19-1.05 ㎍/kg and 0.58-3.18 ㎍/kg, respectively. The accuracies for PSTs were 95.4-107.7% for saxitoxin group, 97.1-100.9% for gonyautoxin group, 99.0-100.8% for N-sulfocarbamoyl toxin group, and 96.8-104.6% for decarbamoyl toxin group. These results indicate that the modified LC-MS/MS method was appropriate for analyzing the PSTs in shellfish and tunicates.