Genetic relationships among populations of the Argentine ant Linepithema humile introduced into Japan

Since some colonies of Argentine ant Linepithema humile were discovered in Japan in 1993, populations of this invasive alien ant species have been expanding their distribution. To resolve the number of invasions and the genetic structure in the early stages of introduction, we inferred the genetic structure and relationships among colonies from eight localities, from analyses of eight nuclear microsatellite DNA markers. F _ST analysis, principal component analysis and assignment test showed that at least three highly genetically differentiated groups of Argentine ants are present in Japan. Populations from Hiroshima Bay were grouped together (Hiroshima, Hatsukaichi, Otake, Iwakuni Central and Iwakuni Kuroiso), while those from Kobe and Yanai were both genetically distant from each other and from the Hiroshima Bay group. Hatsukaichi and Kobe are international seaports, suggesting that the by-ship invasion occurred at least twice. The invasion route of the Yanai population is unknown at this moment. The Aichi population was genetically distant from that of the Hiroshima Bay group by the difference in allele frequencies, and it was plausible that the Aichi population was introduced from the Hiroshima Bay group by human-mediated jump dispersal.     

The Argentine ant, Linepithema humile, in Japan: Assessment of impact on species diversity of ant communities in urban environments

The Argentine ant Linepithema humile (Mayr) invaded the Hiroshima Prefecture in south‐west Japan some time before 1990. In this report, we describe the distribution of this exotic ant species and assess its impact on indigenous ant communities in urban areas. L. humile is now widely distributed mainly in urban areas and surrounding secondary vegetation of the cities Hatsukaichi and Hiroshima. The impact assessment suggested that L. humile reduced species diversity of local, indigenous ant communities. There was differential sensitivity of indigenous ant species to the invasion of L. humile. Some ant species disappeared in parks infested with L. humile; for example, Pheidole noda, Pheidole indica and Lasius japonicus. L. humile seemed to be superior to these ant species in certain traits and habits, such as mobility, recruitment ability, aggressiveness and omnivory. In contrast, Paratrechina sakurae and Camponotus vitiosus were less affected by L. humile infestation. The mechanisms allowing such coexistence seemed to be small body size (P. sakurae) and arboreal nesting habits (C. vitiosus).     

Argentine ant infestation affects the abundance of the native myrmecophagic jumping spider <Emphasis Type="Italic">Siler cupreus</Emphasis> Simon in Japan

The effect of an Argentine ant invasion on the abundance of the myrmecophagic jumping spider Siler cupreus Simon was investigated in the Hiroshima Prefecture, southwestern Japan. The frequency and density of S. cupreus were significantly higher in sites infested with Argentine ants than in ant-free sites. S. cupreus actually preyed on the adult ants and the brood. The dominance of Argentine ants possibly provides an abundant food source for S. cupreus, thus causing an increase in the number of spiders. Received 16 May 2007; revised 27 December 2007; accepted 15 January 2008.     

Detection of an invasive gall-inducing pest, Quadrastichus erythrinae (Hymenoptera: Eulophidae), causing damage to Erythrina variegata L. (Fabaceae) in Okinawa Prefecture, Japan

In 2005, Quadrastichus erythrinae Kim, 2004 (Hymenoptera: Eulophidae), which induces stem, petiole, and leaf galls on Erythrina variegata L. (Fabaceae), was found on the following six islands in Okinawa Prefecture, Japan: Okinawa, Kume, Miyako, Ishigaki, Iriomote, and Hateruma. Galls were also found in Vietnam. In Japan, no further infestation records have been reported from any of Japan's other south‐western prefectures where Erythrina species grow. Because no Erythrina galls were observed in Okinawa Prefecture before 2005, Q. erythrinae seems to have invaded quite recently.     

Geographic differences in paralytic shellfish poisoning toxin profiles among Japanese populations of Alexandrium tamarense and A. catenella (Dinophyceae)

To reconsider whether toxin profile could be used as a marker for populations from different geographical areas, clonal isolates of the toxic dinoflagellates Alexandrium tamarense (Lebour) Balech and Alexandrium catenella (Whedon et Kofoid) Balech from Ofunato Bay (Iwate Prefecture), Atsumi Bay (Aichi Prefecture), Tanabe Bay (Wakayama Prefecture), Harima‐Nada (Kagawa Prefecture), Uranouchi Bay (Kochi Prefecture), Hiroshima Bay (Hiroshima Prefecture) and Yamakawa Bay (Kagoshima Prefecture), which were identified on the basis of morphotaxonomy, immunological and molecular biological techniques, were subjected to analysis of paralytic shellfish poisoning toxins by high performance liquid chromatography‐fluorometric method. All the isolates except A. tamarense OF152 from Ofunato Bay contained mainly N‐sulfocarbamoyl toxins (C1 +2) with various amounts of derivatives, and a typical north‐to‐south trend of decreasing toxicity was observed. In both A. tamarense and A. catenella, toxin profiles were rather constant within a geographical area and divergent among different geographical areas. The toxin profiles of A. tamarense from Harima‐Nada were well conserved among different bloom years. Toxin profile showed that isolates of A. tamarense from Ofunato Bay, A. tamarense from Harima‐Nada isolated in 1988 and A. catenella from Uranouchi Bay were heterogeneous. However, only two or three groups of isolates with different toxin profiles were observed in a geographical region, suggesting that several representative isolates express the genotype in a given region. These observations confirmed that toxin composition could be used as a marker to discriminate different geographical populations of these species.     

Increased incidence of rare cancers and varied age distributions by cancer group: A population-based cancer registry study in Hiroshima Prefecture,Japan

BackgroundEpidemiological characteristics of many types of rare cancers are limited especially in Asia. Therefore, this study aimed to describe the burden and changing time trends of rare cancers in Hiroshima, Japan.MethodsThe internationally agreed RARECAREnet list of rare cancers was used to identify patients diagnosed with cancers from 2005 to 2015 who were registered in the Hiroshima Prefecture Cancer Registry. Quality indicators specific to rare cancers were assessed by cancer grouping. Crude incidence rates (IRs) and age-standardized rates (ASRs) were calculated for 216 single cancers (rare and common) included in the list. A joinpoint regression was used to analyze age distribution and time trends in the ASRs for 12 internationally agreed rare cancer families. Quality indicators, ASRs, and IRs in Japan were identified to examine IR differences and the effects on data accuracy.ResultsThe 231,328 cases were used to calculate the IRs of each cancer. Epithelial tumors in rare families increased with age, but nonepithelial tumors occurred at any age. The proportion of rare cancer families to total cancers was stable. The time trend for families of head and neck cancers (annual percent change and 95 % confidence interval: 2.4 %; 1.2–3.7 %), neuroendocrine tumors (6.6 %; 5.1–8.1 %), and hematological cancers (4.3 %; 3.2–5.5 %) markedly increased.ConclusionThe ASRs of several rare cancers increased because of increased knowledge of these diseases, improved diagnostic techniques, and aggressive diagnoses.     

History of Katayama disease: schistosomiasis japonica in Katayama district, Hiroshima, Japan

Historical account of Katayama disease is presented as a centenary record since the discovery of Schistosoma japonicum in Japan in 1904. The ever unknown endemic disease was called Katayama disease. Katayama district, Hiroshima Prefecture is one of endemic areas of schistosomiasis japonica in Japan. The causative parasite was first discovered in a human case in Katayama district. After the discovery of the parasite, life history, diagnosis, treatment, control measures and even eradication have been worked out, attempted and succeeded in Katayama district together with other endemic areas in Japan. Hiroshima Prefecture declared safety from the disease in 1980.     

A new aerial alga, Stichococcus ampulliformis sp. nov. (Trebouxiophyceae, Chlorophyta) from Japan

A new aerial alga, Stichococcus ampulliformis S. Handa sp. nov. (Trebouxiophyceae, Chlorophyta) is described based on a clone isolated from the bark of Cephalotaxus harringtonia (Knight ex Forbes) K. Koch collected from Taishaku‐kyo Gorge, Hiroshima Prefecture, south‐west Japan. This alga was examined by light microscopy and transmission electron microscopy and subjected to molecular phylogenetic analysis. Based on its morphological features and life‐cycle, especially short filament formation, the alga was assigned to the genus Stichococcus Nägeli. However, this alga differs from other described Stichococcus species in that it reproduces by a form of ‘budding’, producing two daughter cells of different sizes. The larger cell, enclosed within the mother cell wall, soon reaches the size of a normal vegetative cell. The smaller cell is extruded and takes longer to reach full vegetative size. A phylogenetic tree constructed using 18S rRNA sequences indicated that, within the Trebouxiophyceae, S. ampulliformis is closely related to S. bacillaris Nägeli and some species of Prasiola Meneghini.     

Habitat characteristics and seasonal changes of Laurencia brongniartii (CeramiaIes, Rhodophyta) in Kagoshima, Southern Japan

The seasonal change in size of Laurencia brongniartii was observed for the year 2002 at Banshobana Park, Satsuma Peninsula and Tsuchihama Beach, Amami Oshima, both in Kagoshima Prefecture, Japan. Additionally, the vertical distribution of this species was also studied at Tsuchihama Beach (second site), where the largest populations were found. Maximum lengths were observed in October ‐ November with a size of 100 ± 6 mm at Banshobana Park and 111 ± 5 mm at Tsuchihama Beach. Line‐transects conducted at Tsuchihama Beach, were analyzed to determine the vertical distribution of L. brongniartii due to depth and the slope of the substrate. Alga was found growing in areas restricted to low levels of light.     

Chemical composition of Laurencia spp. collected from the Seto Inland Sea of Japan

The chemical composition of three Laurencia spp., Laurencia sp., L. okamurae and L. saitoi, which were collected from the Seto Inland Sea of Japan, has been examined. Laurencia sp. collected from the coast of Matoba Park, Takehara, Hiroshima Prefecture, contained a brominated chamigrane-type sesquiterpene (1), named matobol, as the main metabolite. The structure of matobol was determined as (+)-(2R,3R,6R,10S)-2,10-dibromochamigr-7(14)-en-3-ol (1). This is the first time that the optically active 1 has been isolated from Laurencia. On the other hand, L. okamurae from the coast of Ikunoshima Island, Hiroshima Prefecture, produced laurinterol (2) that is a known cyclolaurane-type sesquiterpene characteristic to this species in Japan. L. saitoi from the coast of Matoba Park contained a known bromoallenic C₁₅-acetogenin, neolaurallene (3).