Keun-Yong Kim

Morphological Observation of Alexandrium tanarense (Lebour) Balech, A. catenella (Whedon et Kofoid) Balech and One Related Morphotype (Dinophyceae) in Korea

Twenty-nine culture strains belonging to the genus Alexandrium Halim (Dinophyceae) were established from water column or sediments in Korea. Seventeen isolates were identified as A. tamarense (Lebour) Balech, eight isolates as A. sp. cf. catenella and one as A. catenella (Whedon et Kofoid) Balech according to the presence or absence of a ventral pore, the shape of the posterior sulcal plate and the sulcal width. Three isolates were unable to be identified due to considerable distortion of thecal plates and lack of enough materials, but typical of A. tamarense and/or A. catenella. The overall cell shape of A. tamarense was usually longer than wide. The posterior sulcal plate was definitely longer than wide dorsoventrally, and sulcus extended posteriorly without apparent widening. They were distributed in three major coasts of Korea. In contrast, the cell shape of A. sp.cf. catenella was generally anterior-posteriorly flattened. The transversal axis of the posterior sulcal plate was always longer than the longitudinal, or both axes were nearly equal in length. Its sulcus was broader than that of A. tamarense and widened in the direction of antapex about 1.5 times. This morphotype existed in nearshore and offshore waters of the southern Korea sea. One of A. catenella isolates from Jinhae Bay showed no conspicuous differences with A. sp. cf. catenella except for the consistent absence of a ventral pore.

Genetic Diversity of Parasitic Dinoflagellates in the Genus Amoebophrya and Its Relationship to Parasite Biology and Biogeography

ABSTRACT. We determined 18S rRNA gene sequences of Amoebophrya strains infecting the thecate dinoflagellates Alexandrium affine and Gonyaulax polygramma from Korean coastal waters and compared those data with previously reported sequences of Amoebophrya from cultures, infected cells concentrated from field samples, and environmental 18S rRNA gene sequences obtained from a variety of marine environments. Further, we used these data to examine genetic diversity in Amoebophrya strains relative to geographic origin, host phylogeny, site of infection, and host specificity. In our analyses of known dinoflagellate taxa, the 13 available Amoebophrya sequences clustered together within the dinoflagellates as three groups forming a monophyletic group with high bootstrap support (maximum likelihood, ML: 100%) or a posterior probability (PP) of 1. When the Amoebophrya sequences were analyzed along with environmental sequences associated with Marine Alveolate Group II, nine subgroups formed a monophyletic group with high bootstrap support (ML: 100%) and PP of 1. Sequences known to be from Amoebophrya spp. infecting dinoflagellate hosts were distributed in seven of those subgroups. Despite differences in host species and geographic origin (Korea, United States, and Europe), Amoebophrya strains (Group II) from Gymnodinium instriatum, A. affine, Ceratium tripos (AY208892), Prorocentrum micans, and Ceratium lineatum grouped together by all of our tree construction methods, even after adding the environmental sequences. By contrast, strains within Groups I and III divided into several lineages following inclusion of environmental sequences. While Amoebophrya strains within Group II mostly developed within the host cytoplasm, strains in Groups I and III formed infections inside the host nucleus, a trait that appeared across several of the subgroups. Host specificity varied from moderately to extremely species‐specific within groups, including Group II. Taken together, our results imply that genetic diversity in Amoebophrya strains does not always reflect parasite biology or biogeography.

Genetic Variation in the Asian Shore Crab Hemigrapsus sanguineus in Korean Coastal Waters as Inferred from Mitochondrial DNA Sequences

Genetic variation in the Asian shore crab Hemigrapsus sanguineus was determined from partial mitochondrial DNA (mtDNA) sequences of the cytochrome b (Cytb) gene. Samples included 143 crabs from six localities along three coastlines in South Korea. A nucleotide sequence analysis revealed 38 variable sites in a 470-bp sequence, which defined 37 haplotypes. The haplotypes were not associated geographically and had a shallow genealogy. Pairwise F ST tests and a two-dimensional scaling analysis revealed no significant genetic differentiation among most of the populations. The low pairwise comparison values, but significant genetic differentiation of a northeastern population from all other populations, might have been influenced by a restriction in gene flow caused by hydrographic conditions such as ocean boundaries. The high haplotype diversity, low nucleotide diversity, and time since H. sanguineus expansion in Korean coastal waters indicate rapid population growth and a recent, sudden expansion in the Late Pleistocene.

Isolation and characterization of the apolipoprotein multigene family in Hemibarbus mylodon (Teleostei: Cypriniformes)

We isolated and characterized the full-length cDNA sequences of nine apolipoproteins (apoA-I-1, apoA-I-2, apoA-IV, apoE-1, apoE-2, apoC-I, apoC-II, apo-14 kDa, and apoM) in the Korean spotted barbel Hemibarbus mylodon (Teleostei: Cypriniformes), an endangered fish species. Nucleotide sequences of all apolipoproteins of H. mylodon showed high levels of identity to those of cyprinid species. The secondary structures of their deduced amino acid sequences were generally conserved with previously reported vertebrate counterparts. Molecular phylogenetic analyses revealed that apolipoproteins from teleosts and avian/mammalian species were phylogenetically separated according to each encoded protein. Within each apolipoprotein lineage, teleosts consistently formed a strongly supported monophyletic group and were genetically separated from terrestrial vertebrates. Tissue distributions of apolipoprotein transcripts in H. mylodon were variable depending on apolipoprotein family members with relatively high expression levels in the liver and intestine. The overall spectrum of mRNA tissue distribution was wider in H. mylodon than in other teleosts and mammals. In addition, our findings showed the multiple isoforms of apoA-I and apoE were differentially modulated across tissues possibly with an isoform-specific role in a given tissue.

Characterization and phylogeny of two β-cytoskeletal actins from Hemibarbus mylodon (Cyprinidae, Cypriniformes), a threatened fish species in Korea

Complementary DNA and genomic sequences representing two different β-actins were isolated from a threatened freshwater fish species Hemibarbus mylodon. The β-actin 1 and 2 encoded an identical number of amino acids (375 aa), and shared 88.8 and 99.7% of identity at coding nucleotide and amino acid levels, respectively. Genomic open reading frame (ORF) sequences of both isoforms contained five translated exons interrupted by four introns with conserved GT/AG exon/intron boundary rule. Semi-quantitative RT-PCR showed that the two isoform mRNAs were ubiquitously detected in all tissues tested, but transcript levels were variable across tissues. Phylogenetic analysis showed that H. mylodon β-actin 1 and 2 were clustered into two distinct major and minor branches of Cypriniformes, respectively. Comparisons of the 5′-upstream region and 3′-UTR of H. mylodon β-actin 1 also showed a high degree of homology with those of the major teleost β-actins and warm-blooded vertebrate β-cytoskeletal actins, suggesting their more recent common origin.

Phylogenetic Relationships among Diverse Dinoflagellate Species Occurring in Coastal Waters off Korea Inferred from Large Subunit Ribosomal DNA Sequence Data

We analyzed the nuclear-encoded large subunit ribosomal RNA gene (LSU rDNA) sequences of 19 dinoflagellates occurring in costal waters off Korea and reconstructed a phylogenetic tree containing 74 representative species from 37 distinct genera. Of these, the LSU rDNA sequences of Amylax triacantha (Jorgensen) Sournia, Gonyaulax verior Sournia (

Complete mitogenome sequence of an endangered freshwater fish, Iksookimia choii (Teleostei; Cypriniformes; Cobitidae)

Iksookimia choii (Teleostei; Cypriniformes; Cobitidae) is an endangered freshwater fish species because of anthropogenic pressures around its natural habitats. We present the complete mitogenome sequence of I. choii to provide baseline data for use in the development of conservation plans and captive breeding programs. The total size, gene content and arrangement, and cloverleaf secondary structures of transfer RNA genes of I. choii mitogenome were highly homogeneous to previously known vertebrate mitogenomes. Phylogenetic analysis using nucleotide sequences of protein-coding and transfer RNA genes reflected the taxonomic clustering in the familial levels among species of the superfamily Cobitoidea. I. choii, which was recently transferred to the newly erected genus Iksookimia from Cobitis, was phylogenetically affiliated to one of two Cobitis species with strong statistical supports, indicating its taxonomically unstable status.

Phylogenetic relationships among three new Hemibarbus mitogenome sequences belonging to the subfamily Gobioninae (Teleostei, Cypriniformes, and Cyprinidae).

Background and aims: Here, we present the full-length mitogenome sequences of Hemibarbus labeo, Hemibarbus longirostris, and Hemibarbus mylodon – three fish species belonging to the subfamily Gobioninae (Teleostei, Cypriniformes, and Cyprinidae). H. mylodon is endemic to the Korean Peninsula and a critically endangered freshwater species because of various anthropogenic activities around its natural habitat. Results: Overall characteristics of mitogenomes of the three Hemibarbus species were identical to previously known typical vertebrate mitogenomes. Bayesian inference of phylogeny recovered the monophyly of the subfamily Gobioninae with high posterior probability support, with the three Hemibarbus species forming a strongly supported monophyletic group. H. mylodon was placed at the basal position, and H. longirostris was separated from two monophyletic H. labeo types. Conclusion: Our findings are congruent with the previous taxonomic appraisal based on morphological analysis.

Phylogenetic Analysis of Dinoflagellate Gonyaulax polygramma SteinResponsible for Harmful Algal Blooms Based on the Partial LSU rDNASequence Data

This study carried out phylogenetic analysis of dinoflagellate Gonyaulax polygramma which was responsible for a harmful algal bloom episode in Korea in 2004. Molecular phylogenetic tree inferred from the partial LSU rDNA data showed that G. polygramma came up among the monophyletic Gonyaulax clade, but did not have apparent genetic affiliation to other Gonyaulax species. This result appears to be consistent with characteristic morphological features of G. polygramma such as epitheca sharply tapering to the apex and thecal plates ornamented with numerous longitudinal striations.

Adaptations of a green tide forming Ulva linza (Ulvophyceae, Chlorophyta) to selected salinity and nutrients conditions mimicking representative environments in the Yellow Sea

Abstract: The massive green tide species Ulva linza undergoes an apparent rafting in a counterclockwise direction in the Yellow Sea from Jiangsu Province, China, to the west coast of Korea. During this dispersal, it undergoes development from early life history stages to senescence and experiences extensive salinity and nutrient gradients. We investigated the physiological responses of different developmental stages of U. linza to three representative environmental conditions that mimicked (1) a brackish environment at salinity 10 (S = 10) and 200 μM NO3−, (2) an inshore environment at S = 30 and 200 μM NO3−, and (3) an offshore environment at S = 30 and 4 μM NO3−. Chlorophyll a fluorescence of the early development stages (spores and germlings) of U. linza was measured using pulse amplitude modulation fluorometry to determine their photosynthetic efficiency. In addition, the photosynthesis and respiration rates of adult thalli were measured using chamber incubation. Within two hours of release, spores showed no difference in photosynthetic performance in the three conditions. Subsequently, the photosynthesis of germlings was enhanced at high-nutrient conditions regardless of salinity, suggesting that brackish and inshore waters are suitable nursery areas for early development. The adult thalli in the brackish environment showed two and three times higher growth rates than in the inshore and offshore environments, respectively. The adult thalli experienced synergistic effects of high nutrients and low salinity on photosynthesis that facilitated rapid growth in brackish environments. Overall, we suggest that brackish areas facilitate the initiation of blooms of U. linza, and the subsequent movement of floating fronds from estuaries to the inshore and then the offshore provides a continuous nutrient inoculum that maintains the population in the offshore environment.