• Journal of Life Science
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• v.18 no.2
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• pp.284-286
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• 2008

Octopus minor (O. minor) is widely distributed along the coastal regions of Korea, but most of them are caught in southern waters which are associated with one of the important fisheries stock. At present, O. minor from China has been introduced to the fishery markets in Korea. Here, we attempt to discriminate their origin for Korea or China using molecular techniques. Based on the O. minor mitochondrial DNA sequence, we developed a PCR-based origin discrimination system. The assay specificity was assessed by testing four individuals of O. minor from Sangdong, China, as well as 20 additional O. minor from Namhae, Muan, Yeosu and Jindo, Korea. Only four isolates of O. minor originated from China tested as positive in our distinction system. All PCR-positive products yielded identical sequences from Chinese O. minor, whereas Korean O. minor appeared to be PCR amplification. This result suggested that the primers used in this study are O. minor species specific, especially originated from China. The detection system appeared to be positive results in the use of 0.1 ng of Chinese O. minor DNA as template, however, the Korean O. minor even using $1{\mu}g$ of DNA showed no amplification. Consequently, the assay provides a simple, rapid and accurate method for the detection of Chinese O. minor.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.44 no.3
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• pp.184-193
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• 2008

For environment-friendly fishery, the lead sinkers of octopus drift line were developed with the environmentfriendly sinker, and their characteristics and performance were investigated. To make the environmentfriendly sinker, the hydrate ceramic material was developed, and to increase the weight and strength, the iron power was added to it. The fishing hook was machine-made, and standardized, by using 60cm iron wire. For the manufacture of the sinker, the first, the mold was made, and then, hydrate ceramic material and water were quantitatively mixed. The mixture was poured into the mold prepared with a fishing hook already inserted, and had hardened for several hour, before it was taken out of the mold as a complete sinker. The sinkers were made in the 8 types ranging in weight from 150 to 500g, and their specific gravities were diverse from 2.871 to 6.637, which was 0.19 to 0.44 times lower than that of lead. The movement of the environment-friendly sinker by flume tank was possible in the weaker current speed than the similar lead sinker. In the coastal fishing grounds of Gangwon province, the comparison of catching efficiency was made between the improved fishing gears composed of the environment-friendly sinkers and artificial baits, and the current used fishing gears of lead sinkers and pig-fat baits. The result showed the tendency in which the improved fishing gears caught the bigger octopuses than the current used fishing gears. In the quantity and number of the fish catch per unit fishing gear, the improved fishing gear showed a little more catch than the current used fishing gear, regardless of the fishing area. However, the number of the improved fishing gears lost during fishing operation was similar to that of the current used fishing gears.

• Journal of the Korean Society of Food Science and Nutrition
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• v.38 no.2
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• pp.177-181
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• 2009

The peptides from Aroase AP10 enzymatic hydrolysates of octopus proteins were isolated and tested for inhibitory activity against angiotensin converting enzyme (ACE). The Aroase AP10 hydrolysates were filtered through PM-10 membrane (M.W. cut-off 10,000) to obtain the peptides fractions with ACE inhibition activity. These fractions were applied to a Biogel P-2 column. Three active fractions (A, B, and C) were collected and applied to a SuperQ-Toyopearl 650S column chromatography, leading to the isolation of four active fractions (A-1, A-2, B-1, and C-1). Among the active fractions, C-1 had the highest ACE inhibitory activity ($IC_{50}=3.10{\mu}g$). The main composition of its amino acids is arginine, lysine, histidine and leucine, which cover about 60% of the total amino acids.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.52 no.4
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• pp.299-307
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• 2016

This study aims to investigate effects of the length of the buoy and sand bag line on the loss of webfoot octopus pot. A numerical modeling and simulation was carried out to analyze the process that the pot gear affected by wave using the mass spring model. Through the simulation, tensions of sand bag line under various condition were investigated by length of buoy and sand bag line. The drag force and coefficient k of an artificial shell used in the webfoot octopus pot was obtained from an experiment in a circular water channel, and the coefficient k was applied to the simulation. To verify the accuracy of the simulation model, a simple test was conducted into measuring a rope tension of a hanging shell under flow. Then, the test result was compared with the simulation. The lengths of the buoy line in the simulation were 1.12, 1.41, 1.80, 2.23, 2.69, and 3.17 times of water depth. The lengths of sand bag line were 10, 20, 30, and 40 meters, and conditions of water depth were 8, 15, 22 meters. 4 meter height and 8 second period of wave were applied to all simulations. As a results, the tension of the sand bag line was decreased as the buoy and sand bag line were increased. The minimum tension of the sand bag line was appeared in conditions that the length of the buoy line is twice of water depth and the sand bag line length is over 40 meters (except in case of depth 8 meters.).

• The Korean Journal of Malacology
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• v.31 no.2
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• pp.113-121
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• 2015

Gametogenesis, mating behaviour and spawning of Octopus ocellatus were investigated by histological study. This species is dioecious, and showed a protandry phenomenon. Ooogenesis (in females) and spermatogenesis (in males) can be classified into 3 stages, respectively. O. ocellatus copulates in one of two ways: a male may leap upon a female, mounting her mantle, or a male may sit near the female and extend the hectocotylized third right arm toward her. Spawning occurred between April and June in females, and between March and May in males of O. ocellatus. The spawning period was once a year and the peak took place between May and June. A number of flatened follicle cells, which were attached to an oocyte, were involved in vitellogenesis in the cytoplasm of the vitellogenic oocyte (maturing oocyte), and formation of chorion membrane (secondary egg membrane) of the ovarian eggs. Fecundity per female closely related to GSI was 294-660 eggs (average, 429 eggs). The diameters of the ovarian eggs surrounded by chorion membrane were approximately in the range of 10.10-2.50 mm. Each ovarian egg laid by a female was connected to an egg string. Each egg string was 1-5.5 cm (average 3.6 cm). The total number of eggs laid by a female of this species ranged 218-314, the egg sizes were independent to the size of female adult. this species has a life mode showing some special reproductive characteristics of an annual semelparity as shown in Octopodidae species because we have never seen a female spawning a second time.

• Journal of the Korean Society of Food Culture
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• v.37 no.3
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• pp.213-238
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• 2022

This study aims to investigate protein consumption market trends in Korea. Protein consumption was divided according to the protein source into meat, fishery, and plant-based protein. To accomplish the goal of this study, food purchase data from 525 households panels collected by the Rural Development Administration over the last 10 years were used. The results of the study showed an increase or decrease in protein consumption by protein type over the last 10 years, and a reason to explain this change has been suggested. Specifically, this study found a dramatic increase in the consumption of several proteins, including beef sirloin, beef tenderloin, seasoned beef & steak, pork belly, pork shoulder, pork neck, seasoned pork, pork cutlet, sweet and sour pork, canned ham, chicken drumstick, chicken breast, dak gangjeong, Chinese fried chili chicken, salmon, eel, abalone, squid, octopus, webfoot octopus, octopus minor, canned whelk, tofu, cold bean soup,and plant-based milk. Some items showed no increase in consumption (such as beef jerky, pork rib, sausage, bacon, whole raw chicken, cutlass fish, oyster, fish cake, crab stick, surimi sausage,and canned fishery), whereas a few items showed decreased consumption (e.g., mackerel, pollack, cod,and canned tuna)

• The Korean Journal of Malacology
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• v.17 no.2
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• pp.85-94
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• 2001

Spawning, hatching, survival and cannibalism of the octopus, Octopus ocellatus, were investigated at the indoor laboratory. The specimens were collected in the coastal waters of Puan, Korea, from March 2000 to May 2001. Changes in the gonadosomatic index (GSI) during March to May, 2000 were similar to those in 2001. The GSI began to increase in March and reached the maximum in May 2000 and 2001. The mean fecundity of adult individuals in April was larger than those in March and May in 2000 and 2001. In the investigations of survival rates of adults according to the water layers, the mean survival rate in the middle water layer was higher than that in the bottom layer in year 2000 (p = 0.002). The survival rate during 2001 was similar to the result of year 2000 in the water layers (p = 0.018). From the investigations with the purchase dates, the survival (88.8%) in the early spawning period (April 10, 2000) showed larger than those in the mid-spawning (May 11, 2000) and the late spawning (May 23, 2000). For aquaculture, it is suggested that the purchase timing of adults in the early spawning period will have a better result than that of the other spawning periods. In the amount of spawning with water layers, the number of eggs spawned of the adults in the middle layer were larger than those in the bottom layer. In the number of eggs spawned with the purchase dates, the number of eggs spawned in the early spawning period were larger than those in the middle and late spawning periods. The size of eggs spawned were 6.904$\times$2.520 mm. the hatching period required (from spawning to hatched larvae) was 55 days (April 17 to June 7,2000) at water temperatures of 11.2 to 21.1$^{\circ}C$. In case of the hatching rates with water layers, the hatching rate in the middle water layer was larger than that in the bottom one (p = 0.004).

• The Korean Journal of Malacology
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• v.26 no.4
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• pp.285-290
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• 2010

The nucleotide sequences of the mitochondrial cytochrome oxidase subunit 1 (CO1) gene of octopus groups collected from Muan, Taean, Yesu, Jeju in Korea and Youngsung, Daeryen in China were analyzed for the identification of species and populations. Six haplotypes were identified from the analyzed 60 individuals. All of the individuals (N = 10) from Jeju showed the A haplotype which was not observed from other groups, and could be classified as a distinct group. The analyzed groups could form two separate clade in MEGA4 analysis. The individuals from Muan, Taean, Yesu in Korea and Daeryen in China form a clase and the others from Jeju in Korea and Youngsung in China formed the other clade. The analysis of relationship among the groups showed the same results. Individuals belong to the group A (Muan, Taean, Yesu and Daeryen) showed closer relationship than individuals belong to the group B (Jeju and Youngsung). Although the CO1 universal primers used in this study was useful as a marker for species identification among Octopus, analysis of population was limited because of few variations in the partial sequences of CO1 analyzed in this study. However, it was possible to show the limited gene flow among the groups which is resulted from the spatial separation and differences in their habitats.

• Journal of the Korean Society of Marine Environment & Safety
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• v.15 no.1
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• pp.11-15
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• 2009

The proposal of the $CO_2$ ocean sequestration necessitates a thorough understanding of its consequences to aquatic organisms. This paper describes acute toxic responses to high $CO_2$ environment of a cephalopod, Octopus vulgaris. O. vulgaris was chronically cannulated in the abdominal aorta and recovered in a restrained chamber. Acid base variables as well as ion concentrations were estimated in samples of the blood collected from recovered O. vulgaris. 100% mortality occurred within 72h during exposure to 3%-$CO_2$ environment. Hemolymph pH significantly decreased after 30 min during exposure to 1%-$CO_2$ environment without any compensation thereafter. $[HCO_3^-]$ significantly increased from 2.2 mM at 0h to 7.8 mM at 8h, but gradually decreased thereafter. Hemolymph ions $([Cl^-],\;[Na^+],\;[K^+])$ showed no significant changes. O. vulgaris may be more sensitive than teleost, yellowtail, flounder and dogfish.

• The Korean Journal of Malacology
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• v.32 no.2
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• pp.133-139
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• 2016

The incubation time required for hatching of O. ocellatus were investigated through the processes of egg and embryonic developments by the dissecting microscopic and visual observations. And differences in ecological characteristics of the plankton mode of life or the benthic mode of life according to total numbers of the suckers on each short arm of the hatched juvenile larvae of O. ocellatus were studied by comparisons with other octopodidae species. Compared with the recent a few results reported by other researchers associated with the incubation time required for hatching by female adult mother of O. minor (73-90 days after spawning at $20.9-21.5^{\circ}C$ ranges), in this study, the incubation time required for hatching by female adult mother of O. ocellatus was 56-57 days after spawning at $11.0-20.4^{\circ}C$. Therefore, the incubation time required for hatching by female adult mother varied with Octopodidae species. In this studies, each ovarian egg laid by a female was connected to an egg string attaching to the surface of the wall or bottom of vacunt shell of Rapana venosa. Egg and embryonic developments of this species were studied in the indoor aquaria, in the specific gravity ranging 1.024-1.025. the hatched juvenile of O. ocellatus is 10.3 mm in the mean total length and 4.5 mm in mantle length, and each of its short arms has 18-20 suckers. The just hatched juvenile larvae of O. ocellatus enter the benthic mode of life (benthic larval stage) after hatching. In particular, regarding differences in ecological characteristics of the mode of life according to total numbers of the suckers, O. vulgaris may not need to have many suckers because they enter the planktonic mode of life after hatching, however O. ocellatus may need to have many suckers, because they should adapt to the benthic mode of life. And also the just hatched juvenile larvae of O. minor (bearing many suckers more than O. ocellatus) enter the benthic mode of life (benthic larval stage) after hatching. Therefore, the total number of the suckers on each short arm of the hatched juvenile larvae can be used for determining whether an octopus species has planktonic larval stages or benthic larval stage (benthic mode of life). In particular, The intracohort cannibalism phenomena appeared at the hatched juvenile larval stage because the larval stage of O. ocellatus and O. minor enter into the benthic larval stage in the early stage, unlike entering into the plaktonic larval stage in other Octopus species such as O. vulgaris: at this time, the early hatched larvae fed the late hatched larvae (they are the same species and almost same ages). Therefore, the intracohort cannibalism pheneomena occur in the just hatched juvenile stage of only O. ocellatus and O. minor.