The complete mitochondrial genome of Labidocera rotunda Mori, 1929 (Copepoda: Calanoida) from Jeju Island, Korea.

We sequenced the complete mitochondrial genome of the copepod Labidocera rotunda (family Pontellidae) collected from Ihotaewoo Beach in Jeju, Korea. The mitochondrial genome was 16,564 bp in length and contained 13 protein-coding genes (PCGs), 22 transfer RNAs, and two ribosomal RNAs. The concatenated phylogenetic tree of L. rotunda was reconstructed using the maximum-likelihood method based on the eight PCGs obtained from eight species of copepods including L. rotunda. The results of the phylogeny analysis showed that L. rotunda was closely related to the family Temoridae among the three families. The complete mitochondrial genome of L. rotunda analyzed for the first time in this study provides insight into the phylogenetic and evolutionary relationship of Labidocera.

Zooplankton diversity monitoring strategy for the urban coastal region using metabarcoding analysis.

Marine ecosystems in urban coastal areas are exposed to many risks due to human activity. Thus, long-term and continuous monitoring of zooplankton diversity is necessary. High-throughput DNA metabarcoding has gained recognition as an efficient and highly sensitive approach to accurately describing the species diversity of marine zooplankton assemblages. In this study, we collected 30 zooplankton samples at about 2-week intervals for 1 year. Zooplankton diversity showing a typical four season pattern. Of the "total" and "common" zooplankton, we assigned 267 and 64 taxa. The cluster structure and seasonal diversity pattern were rough when only the "common" zooplankton was used. Our study examined how to maximize the benefits of metabarcoding for monitoring zooplankton diversity in urban coastal areas. The results suggest that to take full advantage of metabarcoding when monitoring a zooplankton community, it is necessary to carefully investigate potential ecosystem threats (non-indigenous species) through sufficient curation rather than disregarding low-abundance operational taxonomic units.

Morphological and genetic differentiation of heteromorphy in Labidocera rotunda (Copepoda, Calanoida, Pontellidae).

The pontellid calanoid Labidocera rotunda Mori, 1929 is relatively widespread in the inshore surface waters of East Asia. In this study, some heteromorphic specimens have been observed with extreme morphological discrepancies in the female, including the genital double-somite, the second urosomite, the caudal rami, and the fifth leg. To evaluate the validity of species assignment of the morphological variants, we analyzed the DNA sequences of two mitochondrial genes, 16S rRNA and cytochrome oxidase subunit I (mtCOI). The specimens were collected in the Yellow Sea, the East China Sea and the East Sea (Sea of Japan) around Korea. They differed by <2.9% for mt16S rRNA and by 3.7%-4.7% for mtCOI, suggesting that they are conspecific despite their considerable morphological differences. In contrast, Labidocera japonica Mori, 1935, a morphologically similar species to L. rotunda, displayed interspecific variation of 6.1%-7.2% for mt16S rRNA and 15.1%-16.7% for mtCOI.

Microstructure Analysis of Ti-xPt Alloys and the Effect of Pt Content on the Mechanical Properties and Corrosion Behavior of Ti Alloys.

The microstructure, mechanical properties, and corrosion behavior of binary Ti-xPt alloys containing 5, 10, 15 and 20 wt% Pt were investigated in order to develop new Ti-based dental materials possessing superior properties than those of commercially pure titanium (cp-Ti). All of the Ti-xPt (x = 5, 10, 15, 20) alloys showed hexagonal α-Ti structure with cubic Ti3Pt intermetallic phase. The mechanical properties and corrosion behavior of Ti-xPt alloys were sensitive to the Pt content. The addition of Pt contributed to hardening of cp-Ti and to improving its oxidation resistance. Electrochemical results showed that the Ti-xPt alloys exhibited superior corrosion resistance than that of cp-Ti.

Reconstruction of arietellid copepod phylogenetic relationship, with description of a new species of Sarsarietellus (Copepoda, Calanoida, Arietellidae) from Korean waters.

A new species of the genus Sarsarietellus from Korean waters, S. orientalis n. sp. is described based on both sexes. This is very closely related to S. suluensis Ohtsuka, Nishida and Machida, 2005 , but is readily distinguished by the following characteristics: in the female (1) narrow head; (2) nearly symmetrical posterior corners of last pedigerous somite, not extending beyond the genital double-somite; (3) antennary endopod slightly longer than the exopod; (4) nearly equal length of three outer spines and the terminal spine of the exopod of the fifth leg, except for the proximal third outer spine; and in the male the left fifth leg with two whip-like setae on the tip of the second exopodal segment not being rotated outside. Sarsarietellus orientalis is the fourth species of the genus Sarsarietellus, while the male of Sarsarietellus species is the first reported. The habitat colonization of arietellids is reconsidered.