• The Korean Journal of Malacology
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• v.27 no.2
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• pp.131-141
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• 2011

Boring caracteristics, boring rate, and predation, rates on the valves of the seed and adult clams of Meretrix petechialis by Glossaulax didyma didyma in the shellfish aquafarm and the indoor rearing aquarium were investigated by various morphometric data. The investigations were carried out from June to September, 2007. The morphology of drilled holes on the valves of M. petechialis showed the crater type as seen in the spats of Ruditapes philippinarum and M. lusoria. The sizes of the outer diameters of holes were greater than the inner diameters of the holes on the valves of M. petechialis in the shellfish aquafarm and the indoor aquarium at the laboratory. On the whole, the sizes of the holes on the valves of the seeds of M. petechialis was smaller than those bored holes on the adult valves. The location of the bored holes on the valves of the seeds varied widely with the the sizes of the individuals of M. petichialis, while most of holes on the valves of adult clams were located near the umbo position of the valves of the clams in the shellfish aquafarm and the indoor aquarium at the laboratory. On the whole, the outer and inner diameters of the bored holes increased with increase of shell lengths of the clams in the shellfish aquafarm and the indoor rearing aquarium at the laboratory. The authors could confirm experimentally the boring snail, G. didyma didyma, drilled the seeds and adult clams of M. petechialis. In the experiments for 15 days (three times repeated) in the indoor rearing aquarium at the laboratory, the mortality of dead shells to total shells of M. petechialis by boring snail Glossaulax didyma didyma was totally average 41.5%, and percent of drilled shells to total dead shells of clams by the boring snail was average 47.1%. Of total shells, percent of drilled shells to total shells of clams by the boring snail was totally average 19.3%. Predation of G. didyma didyma were greater at night than the day time. Average 0.5 seed and adult individuals of M. petewchialis were consumed per G. didyma didyma, per day. Predation varied with shell lengths of M. petechialis and shell widths of G. didyma didyma.

• The Korean Journal of Zoology
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• v.28 no.2
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• pp.61-70
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• 1985

SDS-polyacrylamide gel electrophoresis for the proteins obtained from the plasma, Scapharca subcrenata and suapharca broughtonii, and for the proteins of muscles of several species in Bivalvia was performed. The protein patterns of plasma showed little difference between S. subcrenata and S. broughtonii in lower molecular weight weight proteins. However, the protein patterns of muscles of other species, which wre used in this study, were more shown in the lower molecular weights than the higher molecular weights in difference. Thus it is thought be an interesting fact. The protein band of blood corpuscles, 17,800 dalton, was not appeared in S. broughtonii, but this band was appeared in S. subcrenata. Henceforth this is the significantly important difference in these two species. But the protein patterns obtained from muscles of the species did not show a difference in a range of molecular weights between 10,000 and 100,000 daltons. Meanwhile, several protein bands obtained from Meretrix lusoria were similar to those of Mercenaria stimpsona. Hence, in this study, 6 protein bands which exist all species in Bivalvia and 4 characteristic protein bands in S. subcrenata and S. broughtoniionly, were investigated. And in four species of Eulamellibranchia, two protein bands in comon and the characteristic band of 23,000 dalton which is belong to Meretrix lusoria and Mercenaria stimdsona, were found. The molecular weights of the characteristic protein patterns, which are contained in each species, were measured and compared.

• The Korean Journal of Malacology
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• v.27 no.2
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• pp.149-157
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• 2011

Some characteristics of the formations of acrosomal vesicles during the late stage of spermatids during spermiogenesis and taxonomical charateristics of sperm morphology in male two species (Saxidomus purpurata and Meretrix petechialis) in the family Veneridae were investigated by electron microscope observations. In two species, the morphologies of the spermatozoa have the primitive type and are similar to those of other bivalves in that it contains a short midpiece with five mitochondria surrounding the centrioles. The morphologies of the sperm nuclear types of S. purpurata and M. petechialis in Veneridae have the curved cylindrical and cylinderical type, respectively. And the acrosome shapes of two species are the same cap-shape type. In particular, the axial filament is not found in the lumen of the acrosome of two species, however, subacrosomal material are observed in the subacrosomal spaces between the anterior nuclear fossa and the acrosomal vesicle of two species. The spermatozoon of S. purpurata is approximately 46-$52{\mu}m$ in length, including a curved sperm nucleus (about $3.75{\mu}m$ in length), a long acrosome (about $0.40{\mu}m$ in length),and a tail flagellum (about 45-$47{\mu}m$ long). And the spermatozoon of M. petechialis is approximately 47-$50{\mu}m$ in length including a slightly curved sperm nucleus (about $1.50{\mu}m$ in length), an acrosome (about $0.56{\mu}m$ in length) and tail flagellum (44-$48{\mu}m$ in length). In two species, the axoneme of the sperm tail flagellum of each species consists of nine pairs of microtubules at the periphery and a pair of cental doublets at the center. Therefore, the axoneme of the sperm tail flagellum shows a 9 + 2 structure. In particular, taxonomically important some charateristics of sperm morphologies of two species in the family Veneridae are acrosomal morphology of the sperm, The axial filament is not found in the acrosome as seen in a few species of the family Veneridae in the subclass Heterodonta. The acrosomal vesicle is composed of right, left basal rings and the apex part of the acrosomal vesicle. In particular, right and left basal rings show electron opaque part (region), while the apex part of the acrosomal vesicle shows electron lucent part (region). These charateristics belong to the subclass Heterodonta, unlikely a characteristic of the subclass Pteriomorphia showing all part of the acrosome being composed of electron opaque part (region). Therefore, it is easy to distinguish the families or the subclasses by the acrosomal structures. The number of mitochondria in the midpiece of the sperm of S. purpurata and M. petechialis in Veneridae are five. However, the number of mitochondria in the midpiece of the sperm in most species of Veneridae in the subclass Heterodonta are four. Therefore, the number of mitochondria of the sperm midpiece of two species are exceptionally 5, and it is only exceptional case in the species in Veneridae in the subclass Heterodonta. Except these cases, the number of mitochondria in the sperm midpiece in all families in the subclass Heterodontaare are 4, and now widely used in taxonomic analyses.

• The Korean Journal of Malacology
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• v.26 no.4
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• pp.317-326
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• 2010

The availability of fast and inexpensive sequencing technology has enabled researchers around the world to conduct many genome sequencing and expressed sequence tag (EST) projects of diverse organisms. In recent years, whole genome projects have been undertaken to sequence ten species from the phylum Mollusca. These include Aplysia californica, Lottia gigantea, Crassostrea virginica, Spisula solidissima, Mytilus californianus, Biomphalaria glabrata, Crepidula fornicata, Elysia chlorotica, Lottia scutum and Radix balthica. Additionally, complete mitochondrial genomes of 91 mollusks have been reported. In Korea, EST projects have been conducted in nine mollusk species that include Nesiohelix samarangae, Pisidium (Neopisidium) coreanum, Physa acuta, Incilaria fruhstorferi, Meretrix lusoria, Ruditapes philippinarum, Nordotis gigantea, Crassostrea gigas and Laternula elliptica. Finally, the mitochondrial genome projects from the Pacific Oyster (Crassostrea gigas) and the rock shell (Thais clavigera) have been conducted and reported. However, no systemic mollusk genome project has so far been conducted in Korea. In this report, the current status and research trends in mollusk genome study in Korea will be discussed.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.2
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• pp.244-250
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• 2020

Microplastic pollution in the marine ecosystem has been emerged as a global issue. In this study, we investigated the abundance of microplastics from clam Meretrix lusoria, blood arkshell Scapharca broughtonii, and warty sea squirt Styela clava obtained from a local market in Busan, Korea. The marine organisms were digested in 10% KOH, and were incubated at 40℃ and 150 rpm, for 7 days. The digest was filtered through standard sieve (5 mm, 1 mm, 300 ㎛, and 100 ㎛), and mciroplastics were identified using a light microscope and microFT-IR. The abundance of microplastics of clam, blood arkshell, warty sea squirt was 0.08 items/g, 0.05 items/g, and 0.12 items/g, respectively. The predominant microplastic size was in the range of 100-300 ㎛, occupying 48%, and the predominant type was fiber. The composition of microplastics was mostly rayon, semi-synthetic cellulosic material and polyester, which are main component of fabric and textile. We strongly believe that this preliminary work may provide useful information for the establishment of the standardized analysis method of microplastics ingested by marine organisms.

• Journal of Aquaculture
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• v.20 no.2
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• pp.75-80
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• 2007

Amino acid composition and relationship of the commercially valuable five Korean Veneridae, Protothaca jedoensis, Ruditapes philippinarum, Meretrix lusoria, Saxidomus purpuratus and Cyclina sinensis were compared. The major amino acids of five species in Veveridae clams were ureanine, taurine, proline, glycine, alanine and arginine. A similarity of amino acid between C. sinensis and M. lusoria was highest (0.94) and lowest (0.52) for between C. sinensis and P. jedoensis, respectively.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.36 no.6
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• pp.708-715
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• 2003

Species composition and distribution patterns of shellfish were investigated in Eoeun and Geojeon tidal flat located in the Saemangeum area on the west coast of Korea from May to October 2000. Nineteen species of shellfish were collected in Geojeon tidal flat. The samples in number of individuals included Umbonium thomasi $(90.0\%)$ and Mactra veneriformis $(5.0\%).$ In Eoeun tidal flat, ten species of shellfish were collected and the dominant species in number of individuals were Potamocorbula amurensis $(55.0\%)$ and U. thomasi $(18.6\%).$ These results were compared with previous studies conducted before the beginning of reclamation in Saemangeum. Compared with the results from 1988, a change In species composition was observed. Laternula flexuosa and Nuttallia olivacea appeared, while Mactra chinensis and Coelomactra antiquata disappeared in the deposition area in Geojeon tidal flat. In the erosion area of Eoeun tidal flat, M. veneriformis and Meretrix lusoria appeared, while Cyclina sinensis disappeared. Based on a cluster analysis, the shellfish community in Eoeun tidal flat was classified into three station groups based on sediment types. Geojeon tidal flat was also classified into three station groups. The distribution of shellfish in the Saemangeum area was closely related to the sediment types.

• The Korean Journal of Pharmacology
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• v.8 no.1
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• pp.15-25
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• 1972

Korean aconitum (Aconitum koreanum R. Raymond) as one of the botanical crude drugs which pertain to helleboraceae has been extensively applied in Chinese medicine during the past decades. It has been particularly used in immortal tonic among the folk remedies in China, however, its general uses comprehend diuresis, cardiotonic, analgesia, neuralgia, gout and, furthermore, even neoplastic effect. The components of aconitum have been acknowledged as aconitine, mesaconitine, hypaconitine, aconine and so on. The main ingredient, aconitine has the advantage of causing the atrial fibrillation, but, its pharmacological research has not been fully elucidated. Although there are many reports with regard to the pharmacological effects on the motility of several animal hearts, their conclusions have not been regretfully coincided yet. The authors hereby paid attention to this point of view and made experiment to examine the relationship between the alcohol extract of Korean aconitum and the motility of the isolated clam heart, making the use of several drugs related to the heart such as serotonin, acetylcholine, pilocarpine, physostigmine, barium chloride, procaine and quinidine. The cardiac movement of the isolated clam (Meretrix lusoria) heart in the standard sea water solution was recorded with the electric kymograph according to the Magnus method. The results of the experiment are as follows. 1. The motility of the isolated clam heart represents the tendency of gradual inhibition in proportion to the concentration of AK-A $10^{-4}$, $5{\times}10^{-4}$, and $10^{-3}$. 2. The cardiac inhibitory effect of AK-A $10^{-3}$ antagonizes the motility of the isolated clam heart pretreated with serotonin $10^{-6}$. 3. The cardiac inhibitory effect of AK-A $10^{-3}$ antagonizes the systolic state appealed by barium chloride $10^{-3}$. 4. The systolic state caused by quinidine $10^{-4}$ is not inhibited by AK-A $10^{-3}$.

• Journal of Food Hygiene and Safety
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• v.7 no.4
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• pp.137-142
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• 1992

The distribution of V. parahaemolyticus was surveyed from various kinds of shells in Kunsan Bay from July to September, 1987. 1be morphological, biochemical and serological characteristics of the isolated strains were studied. The results were as follows: 1. 41 strains were isolated from 1,350 specimens of shells (Crassostrea gigas, Tapes philippinarum, Meretrix Iusoria) 2. The isolation rates of V. parahaemolytieus were 3% in July, 3.8% in August, and 2.2% in September, respectively. 3. V. parahaemolytkus was more frequently isolated from Kunsan (20 strains) than Bideukgi (12 strains) and Gae Hwa-do (9 strains). 4. V. parahaemolyticus was more frequently isolated from C gigas (23 strains) than other shells. 5. Kanagawa hemolysis reactions were all negative. 6. 6 Strains positive to K pooled antiserum included K IV, K V, K VI and K vn type.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.1
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• pp.23-30
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• 2021

To examine the optimal temperature, light intensity, and shell-type for shell-living conchocelis production, we tested the shell infiltration of free-living conchocelis fragments under various environmental conditions. Under a combination of various temperatures (10, 15, 20, 25 and 30℃) and light intensities (1, 5, 10, 20, 40, and 80 μmol m-2 s-1), the optimal infiltration conditions of the evaluated three Pyropia species were 20-25℃ and 5-80 μmol m-2 s-1 for P. yezoensis, 20-30℃ and 20-80 μmol m-2 s-1 for P. seriata, and 20-25℃ and 20-80 μmol m-2 s-1 for P. dentata. The infiltration efficiency of free-living conchocelis for different shell types was greater in Korean and Chinese oyster Crassostrea gigas shells than that in scallop Argopecten irradians and clam Meretrix lusoria shells. These results suggest that oyster shells are suitable substrates for shell-living conchocelis production. In conclusion, the present results for optimal infiltration conditions for free-living conchocelis of the three examined Pyropia species will contribute significantly to the production of stable shell-living conchocelis.