The use of environmental DNA (eDNA) has recently been employed to evaluate the distribution of various aquatic macroorganisms. Although this technique has been applied to a broad range of taxa, from vertebrates to invertebrates, its application is limited for aquatic insects such as aquatic heteropterans. Nepa hoffmanni (Heteroptera: Nepidae) is a small (approx. 23 mm) aquatic heteropteran that inhabits wetlands, can be difficult to capture and is endangered in Japan. The molecular tool eDNA was used to evaluate the species distribution of N. hoffmanni in comparison to that determined using hand-capturing methods in two regions of Japan. The eDNA of N. hoffmanni was detected at nearly all sites (10 eDNA-detected sites out of 14 sites), including sites where N. hoffmanni was not captured by hand (five eDNA-detected sites out of six captured sites). Thus, this species-specific eDNA technique can be applied to detect small, sparsely distributed heteropterans in wetland ecosystems. In conclusion, eDNA could be a valuable technique for the detection of aquatic insects inhabiting wetland habitats, and could make a significant contribution to providing distribution data necessary to species conservation.
In August 2017, an outbreak of the stick insect, Ramulus mikado (Rehn, 1904), was observed in the Akashina area in Central Japan. This stick insect is a wingless, non‐flying species that inhabits East Asia. Although it seems that the occurrence of many individuals emerging together had been observed in the 2 or 3 years prior, the outbreak in 2017 was on a far larger scale, and was therefore not comparable to anything observed previously. Indeed, it was also observed that the stick insects fed on almost all leaves of the large Japanese zelkova trees until the trees were bare. Additionally, mass gatherings of the stick insects on the walls of houses in the area were observed. In Japan, there have been no other reports of outbreaks of R. mikado, thus this represents a unique case. In the Akashina area, the population's sex ratio is heavily biased towards females, as is the case with other populations, indicating that they reproduce parthenogenetically. However, among our observations, one individual of the 724 specimens collected in the present study was in fact a male. As there have only ever been about 10 observed cases of R. mikado males, the male individual collected in our field research constitutes a valuable record.
We developed microsatellite markers for Appasus japonicus (Hemiptera: Belostomatidae). This belostomatid bug is distributed in East Asia (Japanese Archipelago, Korean Peninsula, and Mainland China), and often listed as endangered species in the ‘Red List’ or the ‘Red Data Book’ at the national and local level in Japan. Here we describe twenty novel polymorphic microsatellite loci developed for A. japonicus, and marker suitability was evaluated on 56 individuals from four A. japonicus populations (Nagano, Hiroshima, and Yamaguchi prefecture, Japan, and Chungcheongnam-do, Korea). The number of alleles per locus ranged 1–12 (mean = 2.5), and average observed and expected heterozygosity, and fixation index per locus were 0.270, 0.323, and 0.153, respectively. The 20 markers described here will be useful for investigating the genetic structure of A. japonicus populations, which can contribute in population genetics studies of this species.
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