Tae Joong Yoon

Light-attraction flight of the giant water bug, Lethocerus deyrolli (Hemiptera: Belostomatidae), an endangered wetland insect in East Asia

The giant water bug, Lethocerus deyrolli, is an endangered wetland insect found throughout East Asia. In 2006, the light-attraction flight of L. deyrolli was studied in Gyodong Island, Korea, using artificial light. The flight of L. deyrolli was observed from early June to late October, and two peaks in the numbers of attracted insects were noted in the middle of June and September. L. deyrolli begins to exhibit flight behaviour at a daily mean air temperature of 15°C and above, but optimal flight temperatures for the insect are between 17°C and 19°C, with a wind speed of less than approximately 1.8 m/sec and a relative humidity of around 80%. The length of daylight did not substantially influence the flight pattern. Daily flight occurred principally between 9 pm and 10:30 pm. L. deyrolli individuals attracted by the artificial light were frequently consumed by magpies or house rats. It appears most probable that artificial lights, such as street lights and tennis court lights, constitute a critical factor in the local extinction of L.deyrolli.

Molecular phylogeny of the higher taxa of Odonata (Insecta) inferred from COI, 16S rRNA, 28S rRNA, and EF1‐α sequences

In this study, we sequenced both two mitochondrial genes (COI and 16S rRNA) and nuclear genes (28S rRNA and elongation factor‐1α) from 71 species of Odonata that represent 7 superfamilies in 3 suborders. Phylogenetic testing for each two concatenated gene sequences based on function (ribosomal vs protein‐coding genes) and origin (mitochondrial vs nuclear genes) proved limited resolution. Thus, four concatenated sequences were utilized to test the previous phylogenetic hypotheses of higher taxa of Odonata via Bayesian inference (BI) and maximum likelihood (ML) algorithms, along with the data partition by the BI method. As a result, three slightly different topologies were obtained, but the BI tree without partition was slightly better supported by the topological test. This topology supported the suborders Anisoptera and Zygoptera each being a monophyly, and the close relationship of Anisozygoptera to Anisoptera. All the families represented by multiple taxa in both Anisoptera and Zygoptera were consistently revealed to each be a monophyly with the highest nodal support. Unlike consistent and robust familial relationships in Zygoptera those of Anisoptera were partially unresolved, presenting the following relationships: ((((Libellulidae + Corduliidae) + Macromiidae) + Gomphidae + Aeshnidae) + Anisozygoptera) + (((Coenagrionidae + Platycnemdidae) + Calopterygidae) + Lestidae). The subfamily Sympetrinae, represented by three genera in the anisopteran family Libellulidae, was not monophyletic, dividing Crocothemis and Deielia in one group together with other subfamilies and Sympetrum in another independent group.

Life history and secondary production of Ephemera orientalis (Ephemeroptera: Ephemeridae) from the Han River in Seoul, Korea

In this study, we investigated the life history of Ephemera orientalis, a common lowland burrowing mayfly which resides in temperate East Asia and often causes a serious nuisance to people due to mass emergence from the Han River in Seoul, Korea. Larvae were sampled monthly (every two weeks during the emergence period) from April 2006 to June 2007 using a Surber sampler (50 × 50 cm, mesh 0.25 mm, two replicates). The mean density of E. orientalis was found to be 105.88±42.14 indiv/m2 during the study period. On the basis of the larval body size distribution and emergence time, we concluded that E. orientalis has a univoltine life cycle with two distinct cohort groups, S1-group emerging in May–June and S2-group in August–September. The estimated annual production of the larvae was 1350.84 mg DW/m2; the mean biomass was 325.17 mg DW/m2; the annual production to mean biomass ratio (P/B) was 4.15. Mean water temperature during the study period was 15.02±6.84°C. The accumulated degree days for the S1- and S2-groups were 2565.07 and 2,621.69 degree days, respectively. This study shows that the Han River population of E. orientalis lacks the fast growing cohort (F-group) in May–August, and demonstrates a relatively higher secondary production than that of other stream mayflies (e.g. Gapyeong stream population of E. orientalis).

Development of Glyptotendipes tokunagai (Diptera: Chironomidae) Under Different Temperature Conditions

ABSTRACT The nonbiting midge, Glyptotendipes tokunagai Sasa (Diptera: Chironomidae), is an organism that can be used as a water quality indicator. Development of this insect under different temperatures was evaluated. The highest egg hatching rate was 99.12 ± 1.47% at 30°C, and the lowest was 84.50 ± 11.09% at 10°C. No eggs hatched at temperatures of 8 and 42°C. Developmental rate (1/h) increased gradually as temperature increased from 10 to 35°C with a peak rate (0.045 ± 0.0079) at 35°C. The estimated lower thermal threshold for egg hatching was 9.3°C. Adult emergence rate was highest (80.6%) at 30°C and lowest (22.2%) at 15°C. The developmental times (egg to adult) for both males and females decreased from 2,102.6 to 457.2 h and from 2,337.1 to 619.8 h as temperatures increased from 10 to 30°C. The estimated lower thermal thresholds for males and females were 11.4 and 10.4°C, respectively. The body sizes of all G. tokunagai decreased as temperature increased from 15 to 35°C. From the results of this study, the approximate rearing temperature for G. tokunagai is suggested to be 25–30°C for egg hatching, larval development, and emergence. Our results demonstrate that G. tokunagai is a potential test insect species that can be reared in the laboratory by providing optimal temperature conditions.

Molecular phylogeny evidence of altitudinal distribution and habitat adaptation in Korean Ephemera species (Ephemeroptera: Ephemeridae)

Molecular phylogeny of the four Korean Ephemera species, Ephemera orientalis, E. sachalinensis, E. strigata, and E. separigata, was inferred from 630 bp sequences of the partial mitochondrial cytochrome c oxidase I (COI) gene. Results indicated that mean intraspecific sequence divergences were 0.70%, whereas mean interspecific divergences were 15.75%, and 17 samples were distinguished to four species correctly by COI sequences. The results also demonstrated that four species of Korean Ephemera assembled a monophyletic group with high support in maximum parsimony and maximum likelihood analyses. This Ephemera group was divided into two major clades of E. orientalis–E. sachalinensis and E. strigata–E. separigata. Furthermore, we demonstrated that this phylogeny explained altitudinal and habitat adaptations of Korean Ephemera species. The E. orientalis–E. sachalinensis clade, a widespread and lowland‐adapted mayfly group, retained plesiomorphic traits such as paired stripes on abdominal segments and was regarded as plesiotypic in terms of habitat adaptation, compared to the geographically more limited and upland‐adapted E. strigata–E. separigata clade.

Genetic divergence between the South Korean and Mongolian populations of the dung beetle, Gymnopleurus mopsus (Coleoptera: Scarabaeidae) based on mitochondrial cytochrome c oxidase subunit I (COI) gene sequences

The locally extinct dung beetle, Gymnopleurus mopsus Pallas, 1781 (Coleoptera: Scarabaeidae), has not been found in South Korea since the 1970s. This research was conducted to understand the genetic divergence between the South Korean and Mongolian populations of G. mopsus as a part of its reintroduction program in South Korea. The genetic distance and diversity were determined using the mitochondrial cytochrome c oxidase subunit I (COI) gene sequence (658 bp) corresponding to the DNA barcode region. The mitochondrial COI gene sequences of 64 individuals of G. mopsus collected in South Korea (7 individuals) and Mongolia (57 individuals) showed a relatively high level of genetic diversity (nucleotide diversity, 0.0078 ± 0.0007; Haplotype diversity, 0.965 ± 0.017). The genetic distances between the South Korean and Mongolian populations lay within the intraspecific level and the phylogenetic reconstruction using the neighbor‐joining (NJ) method showed that all individuals belonged to a single clade. This result indicates that the current Mongolian population of G. mopsus is a good candidate source population to restore the locally extinct population of the species in South Korea.

Four-year successive rearing of Glyptotendipes tokunagai Sasa (Diptera: Chironomidae) under laboratory condition

The dipteran Chironomidae have been commonly used as water quality indicators and toxicity test organisms. Two chironomids, Chironomus riparius Meigan and C. tentans Fabricius, are standard test organisms for toxicity (OECD), but their distribution is limited in Korea. The purpose of this study was to establish a Korean native chironomid species as a toxicity test organism. Glyptotendipes tokunagai Sasa, distributed widely in Korean streams, was selected and reared successively under laboratory conditions for over 30 generations over 4 years.

Biological and Genetic Characteristics of Glyptotendipes tokunagai (Diptera: Chironomidae) on the Basis of Successive Rearing of Forty-Two Generations Over Seven Years Under Laboratory Conditions

ABSTRACT Members of the nonbiting midge family Chironomidae have been used worldwide as water-quality indicators or toxicity test organisms. The purpose of this study was to establish the chironomid Glyptotendipes tokunagai Sasa as a new test species by conducting successive rearing under laboratory conditions. We monitored biological and genetic aspects of >42 successive generations over 7 yr, and also compared the development of the 39th generation with the fourth generation under five constant temperatures of 15, 20, 25, 30, and 35°C. We observed that the number of eggs in an egg mass and the adult body sizes decreased rapidly in the early generations, and thereafter tended to stabilize from the fifth generation to the 42nd generation. In all generations, the mean hatching rate was >75%. Males were predominant in the early generations, but the sex ratio increased to 0.5 (ranged 0.24–0.61) in later generations. The genetic divergence of the reared generations, analyzed by using the mitochondrial cytochrome c oxidase subunit I gene, decreased from 0.0049 to 0.0004 as the generations progressed. In comparison with the fourth generation, the mortality and developmental time of the 39th generation were generally greater, and the adult body sizes were generally smaller. The estimated low developmental threshold temperatures of eggs, male larvae to male adults, and female larvae to female adults were 9.6, 11.3, and 9.7°C, respectively. The optimal rearing temperature was determined to be 25°C. This is the first record of domesticated rearing of a wild chironomid species under laboratory conditions for >7 yr.

Identification of insect pests as food foreign materials using DNA barcodes

Insect foreign materials in food are of great economic and hygienic significance. However, identifying these species with any certainty requires an expert taxonomist and can be a time consuming process. Furthermore, insects are found as body parts or they are immature specimens that cannot be identified by conventional means. For these reasons, a reference database and efficient means of identification by non‐specialists are necessary to control insect pests.

Long‐term monitoring of the life history of a riverine mayfly Ephemera orientalis (Ephemeroptera: Ephemeridae) in the Han River in Seoul, Korea

Climatic change often affects life history aspects of aquatic insects. Long‐term monitoring was conducted to understand the life history variability of the riverine mayfly Ephemera orientalis in the Han river, where habitat is largely disturbed by summer floods. Water level of the study site, Godeok‐dong area in Seoul, is regulated by the Paldang Dam located approximately 14 km above the study site. E. orientalis often emerged in large numbers around the study area. Larvae were sampled monthly from April 2006 to July 2010 using a Surber sampler (50 × 50 cm, mesh 0.25 mm, two replicates). Additional qualitative sampling was conducted using a hand net. As a result, based on the larval body size distribution, E. orientalis had a univoltine life cycle with two distinct slow growing cohort groups: the S1group emerged during May–June and the S2 group emerged during August–September. Our previous study conducted in Gapyeong stream in Gyeonggi‐do showed that E. orientalis normally had three cohort groups, S‐1 and S‐2 groups and the F‐group (a fast growing cohort developed during May–August). However, the Han River population of E. orientalis lacked such a fast growing cohort. It is most probable that habitat disturbances caused by high water level during the rainy season negatively affected the development of the fast growing cohort (F‐group) in the Han River area. The relationships between monthly E. orientalis population data and water level in the Han River are presented.