• Korean Journal of Fisheries and Aquatic Sciences
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• v.47 no.3
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• pp.195-203
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• 2014

We investigated the effect low salt (2 or 4% salt) concentrations jeotgal made from Todarodes pacificus on the learning and memory impairments in scopolamine-induced (2 mg/kg, i.p.) dementia rats. Rats treated with oral BF-7 (200 mg/kg, p.o.) as a positive control and Todarodes pacificus jeotgal had significantly reduced scopolamine-induced memory deficits in the passive avoidance test. The Morris water maze test or treatment with 2% salt jeotgal made from Todarodes pacificus significantly ameliorated the scopolamine-induced memory deficits in the formation of long- and short-term memory. The acetylcholine content and acetylcholinesterase acitivity paralleled the results of the behavior experiment. There were no significant differences in the brain acetylcholine contents of the experimental groups, while the brain acetylcholine content of the group treated with 2% salt Todarodes pacificus jeotgal was higher than that of the control group. The inhibitory effect of 2% salt jeotgal made from Todarodes pacificus on the acetylcholinesterase activity in the brain was lower than that of the control group. These trends were similar to those of the gamma-aminobutyric acid content. We suggest that Todarodes pacificus jeotgal enhances learning memory and cognitive function by regulating cholinergic enzymes.

• Applied Microscopy
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• v.32 no.1
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• pp.17-30
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• 2002

The retinae of Todarodes pacificus and Octopus minor are divided into four layers that are an outer segment, a rod base region, an inner segment, and a plexiform layer, respectively. The retina of Octopus minor is about $20{\mu}m$ thicker ($400{\sim}420{\mu}m$) than that of Todarodes pacificus ($385{\sim}400{\mu}m$). A retina is composed of visual cells and supporting cells. The microvilli of length $0.6{\sim}0.7{\mu}m$ are packed densely on top of the supporting cells of Octopus minor while they are not found in Todarodes pacificus. The visual cells and supporting cells have pigment granules that exclude light. In case of Todarodes pacificus, the pigment granules of the visual cell are larger ($2.0{\times}0.5{\mu}m$) than those of the supporting cell ($1.0{\times}0.3{\mu}m$). But, the sizes of both cells are similar in Octopus minor. In the upper portion of a visual cell, microvilli shaped like a comb are forming a rhabdome (diameter, 60 nm) of a hexagonal structure. The rhabdome consists of 4 rhabdomere and the total area of a rhabdom of Octopus minor is larger than that of Todarodes pacificus. The synaptosome constructing a plexiform layer in Todarodes pacificus are divided into two types, each of which possess electron dense-core vesicles and electron lucent vesicles, respectively. Octopus minor also has two types of synaptosomes but each type comprises a mixture of electron dense vesicles and electron lucent vesicles, and electron lucent vesicles only, respectively, which is different from the case of Todarodes pacificus.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.6
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• pp.1052-1057
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• 2021

The diet composition of common flying squid Todarodes pacificus was studied using 1,084 specimens collected through trawl and jigging from June 2018 to June 2020 in the East Sea of Korea. The mantle length (ML) of the collected individuals ranged from 13.6 to 31.1 cm. Todarodes pacificus is a carnivore. In the study area, T. pacificus was observed feeding mainly on fish and cephalopods, in addition to small quantities of crustaceans. The calculated trophic level value for T. pacificus was 4.10. Small individuals (ML, <18.0 cm) mainly fed on cephalopods, while intermediate (ML, 18.0-23.0 cm) and large (ML, ≥23.0 cm) individuals fed mainly on fish and occasionally on cephalopods. Overall, as the body size of T. pacificus increased, the mean weight of the consumed prey increased (one-way ANOVA, P<0.05).

• 한국해양학회지
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• v.30 no.3
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• pp.197-202
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• 1995

A total of 272 specimens of Todarodes pacificus purchased during the period from July 1 to August 30, 1994 in the southern sea off Pusan were examined for their infection status with larval anisakids. Larvae in squids were encapsulated and appeared to remain active. Firty five larval anisakids sorted from T. pacificus (7.72% of infection rate) were classified based on morphological and morphometric observations as follows; Anisakis type I larvae (23 larvae, 51.0%: positive rate), Contracaecum type A (9, 20.0%), Contracaecum D (4, 9.0%), Anisakis II (3, 6.7%) and unknown type (6, 13.3%).

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.1 no.1
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• pp.55-57
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• 1996

A total of 248 specimens of Todarodes pacificus were purchased from the Jumungin fishery market at the East Sea area two times during the period from November 1 to December 30, 1995. Samples were examined for their infection status with larvae anisakid. Anisakid larvae were collected from muscle, viscera and omentum. One hundred sixteen larval anisakids sorted from 34 specimens of T. pacificus (13.7% of infection rate) ranged from 13.5 to 29.5 mm in their body length. They were classified based on morphological and morphometric observations as follows; Anisakis type I larvae (68 larvae, 58.6%: positive rate), Contracaecum type A (5, 4.3%), Anisakis type II (17, 14.5%), Contracaecum type D (8, 7.0%) and unknown type (18, 15.5%).

• Applied Microscopy
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• v.32 no.3
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• pp.247-255
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• 2002

In this study, we carried out immunostaining and immunogold labeling with antibodies to serotonin and somatostatin to examine the characteristics and functions of the neurons that secrete neurotransmitters in optic lobes of Todarodes pacificus and Octopus minor. As a result of immunostaining with anti-somatostatin, the nerve cells of Todarodes pacificus reacted as similar to the anti-serotonin, but in Octopus minor, only large cells in the outer granule cell layer reacted positively. In the immunogold labeling with anti-serotonin, the nerve cells in the inner grande cell layer and medulla of Todarodes pacificus reacted strongly, 30 gold particles being labeled per $0.5{\mu}m^2$ of the cytoplasm. However, in Octopus minor, only 17 gold particles were labeled, which stated a weak reaction. On the other hand, in the anti-somatostatin case, the nerve cells in the outer and inner granule cell layers and medulla of Todarodes pacificus showed strong reaction, 30 gold particles being labeled per $0.5{\mu}m^2$ of the cytoplasm while the nerve cells in the outer granule cell layer of Octopus minor reacted weakly, about 3 gold particles being labeled per the equivalent area. As a result of immunostaining and immunogold labeling with two types of antibodies to each part of the optic lobes, we found that the reactive nerve cells were distributed differently in the two species. In particular, the degree of reactivity to the immunostaining and immunogold labeling appeared stronger in Todarodes pacificus than in Octopus minor.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.4
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• pp.534-536
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• 1999

The common squid, Todarodes pacificus was infected by parasites. The parasites may be infective to humans if common squid are eaten raw as 'sashimi' or 'sushi'. The species of the parasites in host, T. pacificus were Tentacularia sp., Orygmatobothrim sp. and Ponocaecum sp.. The prevalence, relative density and mean intensity of three parasites were $100.00\%$, 24.13 and 24.13 respectively.

• Journal of Marine Life Science
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• v.4 no.1
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• pp.14-21
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• 2019

This review paper discussed the decadal fluctuations in the catch of the common squid, Todarodes pacificus (T. pacificus) by focusing on migration and distribution patterns. Since 1980s, changes in T. pacificus catches were due to climate regime shift in Korean waters. Fluctuation patterns of catches were different between the East Sea and the Yellow Sea. Generally PDO (Pacific Decadal Oscillation) phase shows a negative correlation with strength of warm current to the East Sea. In 1980s when PDO was positive phase (+), T. pacificus catch was higher in the Yellow, but it was lower in the East Sea. In 1990s when PDO was negative phase (-), T. pacificus catch showed opposite trend compared with 1980s. Such spatial and decadal fluctuations of T. pacificus catch were due to its northward migration along with the warm current or southward movement against the current. In the East Sea, strong (weak) warm current period, the current path has been shifted toward the East Sea coast of Korea (central East Sea or the coast of Japan). It has a correlation with PDO. In the positive PDO phase (1980s), the fishing ground was located on the eastern side of Ulleungdo, whereas during negative PDO phase (1990s), they were situated near the southeastern coast of the Korean peninsula. In the 1980s, volume transport passing into the Yellow Sea increased, whereas volume transport in the East Sea decreased. This is one of major reason increasing T. pacificus larvae in the Yellow Sea.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.45 no.2
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• pp.173-179
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• 2012

The common squid $Todarodes$ $pacificus$ is a dominant species in Korean waters, where it is captured preponderantly by the angling fishery. The spawning and nursery grounds of $T.$ $pacificus$ extend from the southern East Sea to the northern East China Sea. Consequently, the environmental conditions in this area during the spawning and nursery seasons might affect the abundance of $T.$ $pacificus$. This study, analyzed the relationship between the distribution of zooplankton and the abundance of $T.$ $pacificus$ and variation in the squid angling fishing grounds in Korean waters. There was a positive relationship between the fluctuations in zooplankton and the catch per unit effort (CPUE; $kg{\cdot}day^{-1}{\cdot}person^{-1}$) of the angling fishery in the East Sea of Korea. The main fishing season is from July to December and the CPUE was closely related to the zooplankton biomass in April in the East Sea. Recently, the center of the squid jigging ground has moved drastically from the area around Ulleung Island to the northern East Sea. We postulate that the fishing grounds of the squid angling fishery will move farther north with climate change.

• Applied Microscopy
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• v.32 no.2
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• pp.175-183
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• 2002

In this study, we carried out immunostaining and immunogold labeling with rabbit anti-dopamine (TH) and rabbit anti-calbindin-$D_{28K}$ to examine the characteristics and functions of the neurons that secrete neurotransmitters in optic lobes of Todarodes pacificus and Octopus minor inhabiting the Korean waters. The obtained results are as follow. In the immunostaining with anti-dopamine, only a few of the large amacrine cells in an the upper part of an outer granule cell layer and the cells forming the islands of medulla showed positive reaction in Todarodes pacificus, while $2{\sim}3$ cells in the upper and middle parts of an outer granule cell layer and more than 5 cells in the islands of medulla reacted positively in Octopus minor. For the case of anti-calbindin case, $2{\sim}3$ small amacrine cells in the upper portion of the outer granule cell layer and $1{\sim}2$ cells which are located in the lower part of an inner granule cell layer showed positive reaction in Todarodes pacificus, while, in Octopus minor, 4 cells in the outer granule cell layer reacted positively, no immunoreactive cell being found in the inner granule cell layer. As a result of performing the immunogold labeling, relative large number ($17{\sim}26$) of gold particles were labeled per $0.5{\mu}m^2$ of the cytoplasm of the cells which showed the immunoreactivity to the anti-dopamine and anti-calbindin in Todarodes pacificus, however, small number (10) of gold particles were labeled in Octopus minor, which reach only half of the number in the Todarodes pacificus.