The subfamily Donaciinae (reed beetles) is a relatively small group that belongs to the family Chrysomelidae. There are typically brightly metallic in color, dorsally and ventrally. The main morphological characters of the group are as following: sutural margin of elytron explanate apically, inner sutural bead sinuate far from apex and joined to outer bead, and elytral apex rounded; hypomeron of pronotum glabrous (or with few scattered setae); mandible with apical teeth approximate, lacking serrulate occlusal edge; median lobe without basal angulation, tegmen robust and tapered (Askevold, 1990).
Reed beetles live in freshwater wetlands, such as ponds, marshes, bogs, fens, lakes, and streams, and their larvae feed on roots and/or subterranean stems of aquatic plants and are therefore considered aquatic beetles (Hayashi, 2020).
The subfamily Donaciinae mainly inhabits in the temperate Holarctic zone excluding the Central America, the west India, Indonesia, northern Australia, and tropical and temperate Africa (An, 2019). Askevold (1990) recognized about 160 species in eight genera belonging to the subfamily Donaciinae worldwide.
Korean members of the subfamily Donaciinae are reported until now three genera, Donacia Fabricius, 1775, Sominella Jacobson 1908 and Plateumaris Thomson, 1859 (An, 2019). The members of genus Donacia includes two and six species belonging to two subgenera, Cyphogaster Goecke and Donaciomina Medvedev, respectively in the Korean Peninsula (An, 2019).
Among them, the distribution record of D. japana Chûjô & Goecke, 1956 from the Korean peninsula is questionable. Regarding three specimens collected on June 1, 1934 in Ungi, Hamgyeongbuk-do, North Korea, which Chûjô (1941) reported as D. aquatica (Linnaeus, 1758), Kimoto and Kawase (1966) reported that this should be referred as D. japana, but Hayashi (2020) stated that this may have been misidentification of D. aquatica.
In this study, as a result of comparing specimens collected in South Korea (Pocheon and Ulsan), including morphological parts such male genitalia (Hayashi, 2020) and gene sequences of the cytochrome c oxidase subunit I (COI) region, with descriptions of D. japana, we conclude that the records of D. japana were replaced with those of D. aquatica in the Korean Peninsula, and D. japana is endemic to Japan.
Materials and Methods
Comparison of morphological characteristics
We examined morphological characters for four specimens of Donacia aquatica collected from Pocheon (on May. 6, 2023) and Ulsan (on Apr. 23, 2022). Seven morphological characters of male used by Hayashi (2020) were selected to compare two species (D. aquatica and D. japana): antenna, longitudinal stripe on elytron, metafemur, metatibia, sternum VII, pygidial apex, and male genitalia. Specimens were taken pictures with a Dhyana 400DC microscope camera that is attached to Leica M125 Stereo microscope. The pictures were stacked by using the Mosaic 2.4 and Delta-Bio multifocus ver. 24. Specimens examined in this study are deposited in insect collections of the Department of Plant Medicine in Sunchon National University.
Comparison of molecular data
We sequenced and analyzed 680 bp fragments of the anterior part and 750 bp fragments of the posterior part from the mitochondrial cytochrome c oxidase subunit I (COI) of D. aquatica. Genomic DNA was extracted from each specimen using a DNeasy Blood and Tissue kit (Qiagen, Inc., Dusseldorf, Germany) following the manufacturer’s protocols. Primer sets LCO1490 (5'-GGT CAA ATC ATA AAG ATA TTG G-3') and HCO2198 (5'-TAA ACT TCA GGG TGA CCA AAA AAT CA-3') (Folmer et al., 1994) for comparison with the European species (of genus Donacia, and primer sets COA3107 (5'-TCT ATT ARD GGD GAD GCD CTA TCT TG-3') and COS2183N (5'-CAR CAY YTA TTY TGR TTY TTY GG-3') (Sota et al., 2004) for comparison with the Japanese species of genus Donacia were used to amplify the COI gene. The Primer sequences were removed from the resulting sequences, and the trimmed sequences were submitted to NCBI GenBank. A BLAST search tool in MEGA11 (Kumar et al., 2018) was used to identify the COI sequence data Donacia aquatica (Linnaeus). Phylogenetic tree was constructed by neighbor-joining method (Saitou and Nei, 1987) with the number of bootstrap replications was 1,000 times (Felsenstein, 1985) based on p-distances (Nei and Kumar, 2000). Plateumaris sericea (Linnaeus, 1758) (Coleoptera: Chrysomelidae: Donaciinae) was used as the outgroup.
Results and Discussion
Taxonomic account
Family Chrysomelidae Latreille, 1802
Subfamily Donaciinae Kirby, 1837
Genus Donacia Fabricius, 1775
Donacia Fabricius, 1775: 195. (Type species: Donacia crassipes Fabricius, 1775)
Subgenus Donaciomima Medvedev, 1873
Donaciomima Medvedev, 1873: 876 (Type species: Donacia clavareaui Jakobson, 1906)
Donacia aquatica (Linnaeus, 1758) 홍날개뿌리잎벌레
Leptura aquatica Linnaeus, 1758: 397.
Leptura coccineofasciata Harrer, 1784: 226.
Donacia concinna Weise, 1989: 179.
Donacia cyanicollis Olsoufieff, 1903: 303.
Donacia dentipes Fabricius, 1792: 116.
Donacia fasciata Herbst, 1784: 100.
Donacia latonae Gistel, 1857: 586.
Donacia vittata Olivier, 1791: 292.
Donacia waldaica Olsoufieff, 1903: 303.
Records for Korean Donacia aquatica. Donacia aquatica - First recorded by Chûjô (1941: 451) based on specimens collected in Ungi, Hamgyeongbuk-do.
Donacia japana - Misidentified by Kimoto and Kawase (1966: 40) based on same specimens reported by Chûjô (1941); after that, all the following records were simply cited from the report of Kimoto and Kawase (1966): ESK and KSAE (1994: 189), Lee and An (2001: 20), An (2019: 64), and KSAE and ESK (2021: 346).
Comparison of morphological characteristics. Eight morphological characters of male used by Hayashi (2020) were selected to compare two species (Donacia aquatica and D. japana): antenna, longitudinal stripe on elytron, metafemur, metatibia, sternum VII, pygidial apex, and male genitalia. As a result of comparing specimens collected in South Korea (Pocheon and Ulsan) with descriptions of D. japana from Hayashi (2020), the longitudinal stripe on elytron continuous in D. aquatica and discontinuous in D. japana; male pygidial apex rounded in the former and shallowly emarginated in the latter; endophllus of D. aquatica basal supporting block (BSB) elongate, but D. japana BSB short; and a cap of tegmen broad subapically in the former and slender in the latter (Fig. 1).
Comparison of molecular data. We sequenced and analyzed 680 bp fragments of the anterior part and 750 bp fragments of the posterior part from the mitochondrial COI of D. aquatica. Plateumaris sericea (Linnaeus, 1758) (Coleoptera: Chrysomelidae: Donaciinae) was used as the outgroup. A 680 bp of anterior region of the mtDNA COI gene was amplified from 1 individual Donacia beetles (Table 1) using a set of universal COI primers. Alignment of these sequences and five previously reported Donacia sequences from GenBank (Table 1) were used for phylogenetics analysis. And also, a 750 bp of posterior region of the mtDNA COI gene was amplified from 1 individual Donacia beetles (Table 2) using a set of COI primers designed by Sota et al. (2004). Alignment of these sequences and seven previously reported Donacia sequences from Gen- Bank (Table 2) were used for phylogenetics analysis. Analysis using both primer sets showed that the neighbor-joining tree grouped the four and seven morphologically identified Donacia species based on the COI gene sequences respectively, as well as the outgroup species Plateumaris sericea (Linnaeus, 1758) (Coleoptera: Chrysomelidae: Donaciinae) (Fig. 2 and 3). Ultimately, the results of these trees strongly support that the Korean Donacia species is same as the European D. aquatica, but is a different from Japanese D. japana.
Comparison of geological distribution.Donacia aquatica is nearly distributed throughout the Palearctic region from Europe to the Russian Far East (Silfverberg, 2010). We were not examined to the North Korean specimens collected from Ungi, Hamgyeongbuk-do, which was first reported as the Korean D. aquatica in this study, while it is very likely that D. japana distributed in Japan which is isolated from the Northeast Asian continent, is an endemic species (Hayashi, 2020). Additionally, adults of the genus Donacia have poorly developed hind wings, so it is unlikely that they will naturally cross the sea and invade other countries.
Biological notes. Adults of Donacia aquatica (L.) usually observed April to May on the host plants of Carex sp. and Sparganium fallax Graebn. in South Korea (Fig. 4). The host plant S. fallax Graebn. was known to be distributed only in Jeju Island (Kim et al., 2010), but additional distribution areas were confirmed by Kim (2024). Adults mainly feed on the leaves and flowers of the host plants mentioned above. Their oviposition pattern appears a cluster wrapped in a membrane between overlapping leaves of S. fallax Graebn. (Fig 5). Eggs hatched after about 7 days at room temperature.