• Development and Reproduction
• /
• v.13 no.2
• /
• pp.115-122
• /
• 2009

Spermatogenesis and ultrastructural characteristics of sperm of brackish water diploid Corbicula japonica were investigated by electron microscope observations. Based on the cytological studies, the spermatozoon of this species (brackish water diploid) C japonica is approximately 55 ${\mu}m$ in length. The sperm head (about 12 ${\mu}m$ long) is elongated and tapers with a slight curve. Sperm nucleus is about 7.90 ${\mu}m$ long, and the acrosome is about 2.70 ${\mu}m$ long: The morphologies of the sperm nucleus type and the acrosome shape of this species are a long arrow-like type and long cone-like shape, respectively. The sperm head of this species (external fertilization, dioecious and oviparous species) is partially modified from that of the primitive type, as seen in triploid Corbicula species (internal fertilization, hermaphrodite and ovoviparous species), reported by some authors. However, this species produces uniflagellate spermatozoa, unlike freshwater triploid hermaphroditic clams being possessed of partially modified biflagellate spermatozoa. Diploid C japonica is similar to those of other bivalves being possessed of a short midpiece containing four mitochondria surrounding the centrioles. The axoneme of the sperm tail flagellum consists of nine pairs of microtubules at the periphery and a pair at the center. The axoneme of the sperm tail shows a 9+2 structure, and from uniflagellate sperm cross sectioned, in particular, wing-like axonernal lateral fins are observed, as seen in external fertilization fishes.

• Korean Journal of Environmental Biology
• /
• v.39 no.3
• /
• pp.273-288
• /
• 2021

We analyzed the spatio-temporal distribution characteristics of water quality and phytoplankton communities in the Isa Stream systems (ISS) from Sangsa Lake to Suncheon Bay. Sangsa Lake showed relatively oligotrophic and mesotrophic conditions, but the freshwater and mixed brackish water zones showed more severe eutrophication than Sangsa Lake and Suncheon Bay due to the influence of industrial waste such as livestock waste. In terms of the phytoplankton community, the number of phytoplankton species was higher in freshwater and mixed brackish water zones than in Sangsa Lake and Suncheon Bay, but the cell density and Chlorophyll-a concentrations (Chl-a) were relatively high in Sanga Lake and Suncheon Bay. In particular, the mesotrophic species Fragilaria crotonensis and Asterionella formosa showed different dominance in the surface and bottom layers, and the influence of A. formosa was significant in the freshwater and mixed brackish water zones in spring and summer. However, Skeletonema costatum-ls, a eutrophic indicator species, dominated in mixed brackish water zones to seawater in autumn and winter. Thus, the severe eutrophication and rapid environmental changes in the ISS could seriously damage the coastal ecosystem in Suncheon Bay. These ecosystem changes are threatening in terms of conservation and management of the UNESCO Suncheon Biosphere Reserve and Yeoja Bay including Suncheon Bay, which recorded the first Ramsar wetland in Korea. Therefore, further research is needed to establish an in-depth management plan.

• Korean Journal of Ichthyology
• /
• v.21 no.4
• /
• pp.311-321
• /
• 2009

Three categories (freshwater, amphidromous, and marine fishes) of Taiwanese fishes are analyzed on the basis of zoogeographic elements, viz. China element, Indo-China element, Indo-West Pacific element, Indo-Pacific element, North-Pacific element, Japan-Oregon element, and circumtropical element. Freshwater fishes, which include the China and Indo-China elements, are distributed on part of the boundary area between the Palaearctic and Oriental regions of Wallace (1876). Diadromous fishes include the North-Pacific, Indo-China and Indo-West Pacific elements. Taiwanese salmon, a landlocked (initially diadromous) species that became established in Taiwan between 0.5 my B.P. and the early Pleistocene, is recognized as a distinct taxon included within the Oncorhynchus masou complex, which comprises here three species and two subspecies, viz. Oncorhynchus masou masou (Sancheoneo, Songeo, Sakura-masu or Yamame), O. masou ishikawae (Satsuki-masu or Amago), O. sp. (Biwa-masu), and O. formosanus (Taiwanese salmon), based on molecular, morphological and biological studies. Marine fishes are discussed under the following headings, brackish-water fishes (fishes of brackish waters and seas adjacent to continental coastlines, North Pacific and Indo-West Pacific elements; fishes of brackish waters and seas primarily around islands, Indo-West Pacific element), reef fishes (fishes of inshore reefs along continental coastlines from 0 to ca.100 m depth, Indo-West Pacific element; fishes of inshore reefs primarily around islands from 0 to ca.100 m depth, Indo-West Pacific element; fishes of offshore reefs along continental shelf edges from ca.150 to 300 m depth, circumtropical and Indo-Pacific elements; fishes of offshore reefs primarily around islands from ca.150 to 300 m depth, Indo-Pacific element), demersal fishes (fishes on continental shelves shallower than ca.150 m depth, Indo-West Pacific and Japan-Oregon elements; fishes on edges and upper continental slopes from ca.150 m to 500 m depth, Indo-West Pacific, Indo-Pacific, and circumtropical elements; fishes on lower continental slopes to abyssal plains from ca.500 m to 6,000 m depth, circumtropical element and rarely Indo-Pacific element), pelagic fishes (epipelagic fishes from 0 to ca.150 m depth, Indo-West Pacific, Indo-Pacific or circumtropical elements; meso- and bathypelagic fishes from ca.150 to 3,000 m depth, circumtropical element). The distribution of Taiwanese marine fishes are influenced by the Kuroshio Current, low-salinity and low-temperature waters from mainland China, and sea-bottom topography.

• Parasites, Hosts and Diseases
• /
• v.59 no.4
• /
• pp.341-353
• /
• 2021

Acanthoparyphium shinanense n. sp. (Digenea: Echinostomatidae) is described from chicks experimentally infected with the metacercariae encysted in 2 brackish water clam species, Ruditapes philippinarum and Coecella chinensis, in the Republic of Korea. The metacercariae were round to oval, armed with 23 collar spines, and 0.216 (0.203-0.226) mm in diameter. From 5 chicks experimentally infected each with 200 metacercariae, 34 juvenile (5-day-old worms) and 104 adult flukes (7-day-old worms) were harvested from their small intestines, with the average worm recovery rate of 13.8%. The adult flukes were 3.18 (2.89-3.55) mm long and 0.68 (0.61-0.85) mm wide, with an elongated, posteriorly tapering body, and a prominent head collar armed with 23 collar spines arranged in a single uninterrupted row. The posterior testis of A. shinanense was longitudinally elongated, which is similar to Acanthoparyphium spinulosum Johnston, 1917 but unique from the other closely related species, including Acanthoparyphium tyosenense Yamaguti, 1939, Acanthoparyphium kurogamo Yamaguti, 1939, and Acanthoparyphium marilae Yamaguti, 1934. The eggs of A. shinanense were larger than those of A. spinulosum, and the anterior extent of 2 lateral groups of vitellaria was slightly more limited in A. shinanense than in A. spinulosum. Molecular analysis of nuclear and mitochondrial genes revealed low homology with A. spinulosum from USA (96.1% in 5.8S rRNA) and Ukraine (97.9% in 28S rRNA), Acanthoparyphium n. sp. from USA (98.0% in 28S rRNA), and Acanthoparyphium sp. from Australia, Kuwait, and New Zealand. Biological characteristics, including its first intermediate host and natural definitive hosts, as well as its zoonotic capability, should be elucidated.

• Animal Systematics, Evolution and Diversity
• /
• v.29 no.3
• /
• pp.227-237
• /
• 2013

A new copepod species, Cletocamptus koreanus, is described from estuaries and salt marshes on south and southwest coasts in Korea. Cletocamptus koreanus n. sp. evidently belongs to C. deitersi species group in sharing 6-segmented antennule, 3 setae on antennary exopod, leg 1 with endopod shorter than exopod, and 2+1 inner setae on the third exopodal segments of legs 3-4. However, C. koreanus is distinguished from its allied congeneric species by different setal armatures of mandibular palp, antennary exopod, endopod of female leg 2 and the third exopodal segments of legs 3-4, and relative length and shape of apophysis of male leg 3 enp 2. Description and taxonomic accounts of the new species are presented herein, with detailed illustrations and scanning electron microscope photomicrographs. Discussion on the affinities with other species of C. deitersi group are provided, along with brief comments on the morphological discrepancies between the new species from Korea and other Asian species from China and India.

• Journal of Species Research
• /
• v.8 no.4
• /
• pp.380-388
• /
• 2019

We collected ciliate species from diverse habitats (brackish water, marine water, and terrestrial ecosystems) composed of estuarine, coast, and moss samples during 2017-2018 in Korea. The morphology and infraciliature of these species were examined and identified based on the observations of living cells and protargol impregnated specimens. Of the ciliates we identified, we described eight unrecorded species in Korea as followings: class Heterotrichea - Condylostoma vorax, Peritromus kahli; class Protocruziea - Protocruzia labiata; class Spirotrichea - Hemiamphisiella granulifera; class Litostomatea - Loxophyllum chinense; class Phyllopharyngea - Trochilioides recta; and class Oligohymenophorea -Cohnilembus verminus, Uronemella filificum. Among them, Protocruzia labiata is a poorly known species. In this paper, we provide the improved diagnoses and brief descriptions of the species with their microphotographs. The taxonomic classifications of the eight species are summarized as six classes, eight orders, five families, and eight genera. These voucher slides with protargol impregnated specimens have been deposited in the National Institutes.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.40 no.1
• /
• pp.8-15
• /
• 2007

This study selected the optimal microalgal species for mass culture of a brackish water copepod Paracyclopina nana. Fifteen microalgal species were tested to examine nauplius production and the survival and maturation of brood females. Total and daily nauplius production were highest in P. nana fed Tetraselmis suecica followed Isochrysis galbana, Dunaliella tertiolecta, and Phaeodactylum tricornutum. With a monospecific microalgal diet, the total density was highest with P. nana fed I. galbana, at 63.3 inds./mL. With a mixed microalgal diet, the total density of P. nana fed T. suecica+I. galbana was higher than that fed other mixed diets, although there was no difference between a monospecific diet of I. galbana and a mixed diet of T. suecica+I. galbana. Examining the fatty acid composition of P. nana, the eicosapentaenoic acid (EPA) was highest in P. nana fed T. suecica at 5.4% while the docosahexaenoic acid (DHA) content was highest I. galbana diet at 31.9%. Although no DHA was detected in T. suecica, P. nana fed this microalgal species had a high DHA composition of 24.3%. We suggest that the optimal microalgal species for the mass culture of P. nana is T. suecica which is easy to culture on masse and has a high linolenic acid content.

• Ocean Science Journal
• /
• v.42 no.4
• /
• pp.255-267
• /
• 2007

Three brackish-water harpacticoid species belonging to the family Cletodidae are reported from the salt marshes in South Korea: Limnocletodes behningi Borutzky, 1926, L. angustodes Shen and Tai, 1963 and Kollerua longum (Shen and Tai 1979). Two genera, Limnocletodes and Kollerua, and the three species are newly added to Korean fauna. This paper deals with the redescription and systematic accounts of them, with detailed illustrations.

• Journal of Species Research
• /
• v.6 no.spc
• /
• pp.15-25
• /
• 2017

Twelve ciliates were collected from freshwater, marine, and brackish water habitats in Korea and taxonomic descriptions are provided based on observations of living cells and protargol-impregnated specimens. These ciliates, recorded for the first time in Korea, were classified into 12 genera, 11 families, 10 orders, and five classes. We provide brief descriptions and remarks, including microphotographs, for the 12 ciliates: Allotricha mollis, Amphileptus eigneri, Didinium gargantua, Holophrya teres, Lacrymaria marina, Novistrombidium apsheronicum, Pelagostrobilidium conicum, Pseudochilodonopsis fluviatilis, Pseudourostyla subtropica, Strombidium conicum, Urocentrum turbo, and Uronema marinum.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.17 no.2
• /
• pp.76-86
• /
• 2012

Macrozoobenthos were collected from 24 sites using small grab ($0.05m^2$) in order to see the spatial distribution of them at Sueocheon stream at the northern part of Gwangyang Bay during summer season when the maximum ecological processes are occurring. A total of 44 species of macrozoobenthos occurred, and their mean density was $789individuals/m^2$. Mollusks was the dominant faunal group accounted for 43.1% and 86.8% of the whole community density and biomass, respectively. Top five dominant species were a molluscan, Corbicula japonica (40.7%), two polychaete worms, Neanthes japonica (19.3%) and Heteromastus filiformis( 8.1%), and two crustaceans, Paranthura japonica (6.9%) and Jaeropsis sp. (6.9%). Species diversity index was very low with mean value of 1.12 and maximum value was recorded at the river mouth. At the upper stream, a brackish water species such as Corbicula japonica showed their maximum population density. The overall distribution of stream macrobenthos showed a rather simple pattern along with salinity and grain size gradients with few brackish water species occurring at coarse sediments in the stream but more diverse faunas inhabiting fine sediments in the river mouth.