Nematode and Strepsipteran Parasitism in Bait-Trapped and Hand-Collected Hornets (Hymenoptera, Vespidae, Vespa).

The parasitism of two groups of host-manipulating parasites of hornets was examined in Kyoto, Japan. Vespa mandarinia (661 individuals), V. simillima (303), V. analis (457), V. ducalis (158), V. crabro (57), and V. dybowskii (4) were collected either by bait trap or hand collection with an insect net, and examined for their parasites. An endoparasitic nematode, Sphaerularia vespae was isolated from three overwintered gynes of V. mandarinia and a gyne of V. ducalis. While endoparasitic insects, Xenos spp., were recovered from 13 V. mandarinia, 77 V. analis, two V. ducalis, and three V. crabro, and those recovered from V. analis and others were molecularly identified as X. oxyodontes and X. moutoni, respectively. Comparing Xenos parasitism level and capturing methods, the parasitism level was significantly higher in trapped hosts than in hand-collected ones, suggesting that stylopized hosts are more strongly attracted to the food source (bait trap) compared with unparasitized hosts. The genotypes of S. vespae were identical to each other, and near identical to its type population. While each of the two Xenos spp. showed four mitochondrial DNA haplotypes. A phylogenetic comparison suggested that Xenos haplotypes found in the present study are close to those previously reported from Japan and other Asian countries.

Complete mitochondrial DNA sequence of the paper wasp Polistes riparius (Hymenoptera: Vespidae).

The paper wasp Polistes riparius is distributed in cold regions of northern East Asia to Russia. P. riparius are characterized by having longer cells than those of the closely related P. chinensis, which has a similar life history, as an adaptation to cold regions. The phylogenetic relationships of paper wasps have recently been studied; however, the genetic diversity and population structure of P. riparius has not been determined. The present study is the first to analyze the complete mitochondrial genome using next generation sequencing of P. riparius collected from Sapporo, Hokkaido Prefecture, Japan. The genome consisted of a closed loop that was 16,383 bp-long and included 13 protein coding genes (PCGs), 22 tRNA genes, two rRNA genes, and one AT-rich control region. The average AT content was 84.54%. The heavy (H)-strand was predicted to have 12 PCGs and 14 tRNA genes, while the light (L)-strand was predicted to contain one PCGs, eight tRNA genes, and two rRNA genes. All PCGs started with ATG. Stop codons were of two types: TAA for 11 genes (ND1, ND2, ND3, ND4L, ND5, ND6, COXI, COXII, COXIII, COB, ATP6 and ATP8) and TAG for two genes (ND3 and ND4). The molecular phylogenetic relationship based on the maximum likelihood method using 13 PCGs was consistent with some previous studies in which a closely relationship between P. riparius and P. jokahamae.

Co-occurrence of ecologically equivalent cryptic species of spider wasps.

Many cryptic species have been discovered in various taxonomic groups based on molecular phylogenetic analyses and mating experiments. Some sympatric cryptic species share equivalent resources, which contradicts the competitive exclusion principle. Two major theories have been proposed to explain the apparent lack of competitive exclusion, i.e. niche-based coexistence and neutral model, but a conclusive explanation is lacking. Here, we report the co-occurrence of cryptic spider wasp species appearing to be ecologically equivalent. Molecular phylogenetic analyses and mating experiments revealed that three phylogenetically closely related species are found sympatrically in Japan. These species share the same resources for larval food, and two of the species have the same niche for nesting sites, indicating a lack of competitive exclusion. This evidence may suggest that ecologically equivalent species can co-occur stably if their shared resources are sufficiently abundant that they cannot be over-exploited.

Sphaerularia vespae sp. nov. (Nematoda, Tylenchomorpha, Sphaerularioidea), an endoparasite of a common Japanese hornet, Vespa simillima Smith (Insecta, Hymenoptera, Vespidae).

Sphaerularia vespae sp. nov., an endoparasite of a common Japanese hornet, Vespa simillima is described from Hokkaido, Japan, and its molecular sequence profiles are given. This newly discovered nematode appears to belong to the genus Sphaerularia, judging from its characteristic parasitic form, the uterium, which looks like a sausage with many verrucae on its surface. Sphaerularia vespae sp. nov. is distinguished from S. bombi, the only other nominal species of the genus, by the morphology of the male bursa, female tail, and anterior end of parasitic juveniles. SSU, ITS, and D2D3 (LSU) DNA sequences were determined for S. vespae sp. nov. and compared with those from related nematodes obtained from the GenBank database. The sequences from S. vespae sp. nov. were close to those of S. bombi and several another tylenchid entomoparasitic nematodes. Sphaerularia vespae sp. nov. parasitizes overwintering gynes of the hornet and practically sterilizes them, as S. bombi does for bumblebee gynes.