Fertilization and pesticide use in conventional farming greatly affects the soil invertebrate community structure. A recent study reported that megascolecid earthworms were more abundant in an organic apple orchard with no fertilization or agrochemicals compared with an adjacent, conventionally managed apple orchard in Japan. Understory plant and leaf litter compositions also largely differed between these orchards. Under conventional farming practices, monocotyledonous species were dominant, with only a few dicotyledonous species, whereas both monocotyledonous and dicotyledonous species were dominant in the organically farmed orchard. Here, we examined the effect that differences in leaf litter had on the growth and reproduction of megascolecid earthworms to elucidate why megascolecid earthworms dominate in organic farms. Breeding experiments were conducted for 12 weeks using the important megascolecid earthworm Metaphire hilgendorfi (Michaelsen, 1892). We used four leaf-litter treatments: 1) monocotyledonous leaf litter from conventional farming, 2) monocotyledonous leaf litter from organic farming, 3) dicotyledonous leaf litter from organic farming, and 4) no leaf litter. We found that earthworms in treatments containing monocotyledonous leaf litter from conventional farming or dicotyledonous leaf litter from organic farming were heavier after 9–12 weeks than those in the other treatments. Cocoon viability was lower in the conventional farming treatment than in treatments with leaf litter from organic farming. Survival rates and the number of cocoons did not differ among the leaf-litter treatments. Our results indicate that dicotyledonous leaf litter from organic farming is the most suitable food resource for M. hilgendorfi, suggesting that organic apple orchards are dominated by megascolecid earthworms because they provide adequate dicotyledonous leaf litter.
Ceratophysella mediolobata Nakamori, sp. nov., obtained from fungal sporocarps in Akita, northern Japan, is described herein. Ceratophysella liguladorsi (Lee, 1974) has been obtained from fungal sporocarps in the Ryukyus, southern Japan, as the first record from Japan. These species and Ceratophysella tergilobata (Cassagnau, 1954) are similar to each other in having a central projection on abdominal segment V, but C. tergilobata can be distinguished from the other two species by having one sublobal hair on the maxillary outer lobe (two sublobal hairs in the other species), and C. mediolobata sp. nov. can be distinguished from C. liguladorsi by the absence of third setae in the posterior-row on abdominal tergum IV (present in C. liguladorsi). Partial regions of the mitochondrial cytochorome c oxidase subunit 1 and 16S ribosomal RNA genes of C. liguladorsi and C. mediolobata sp. nov. were sequenced for DNA barcoding.
Carabus insulicola Chaudoir, 1869 is a Japanese endemic ground-beetle species with a major geographic range from central to northern Honshu. In Hokkaido it had previously been found in Hakodate and Bibai, but here we report a new record from Tomakomai City. We found the species in two isolated urban forests, whereas we did not find it in the large suburban forests. mtDNA analysis of the NADH dehydrogenase subunit 5 (ND5) in two male individuals revealed that nucleotide sequences of the two specimens were identical with the one in the southern Tohoku District, not the one from the northern Tohoku District ̶ just across a narrow strait from Hokkaido. This result strongly suggests that the population in Tomakomai City was introduced from Honshu by human activity. Introduction of and colonization by the species are likely facilitated by: i) active movement of people and goods between the southern Tohoku Distinct and Tomakomai; and ii) the species' preference for forest edges and open habitats, and ability to inhabit urban forests.