Biomedical subjects

Kazunori Yoshizawa

Publications and source records attributed to Kazunori Yoshizawa.

6 recordsLinked to original sources

PubMed2006

Symbiotic bacteria associated with stomach discs of human lice.

The symbiotic bacteria associated with the stomach disc, a large aggregate of bacteriocytes on the ventral side of the midgut, of human body and head lice were characterized. Molecular phylogenetic analysis of 16S rRNA gene sequences showed that the symbionts formed a distinct and well-defined clade in the Gammaproteobacteria. The sequences exhibited AT-biased nucleotide composition and accelerated molecular evolution. In situ hybridization revealed that in nymphs and adult males, the symbiont was localized in the stomach disc, while in adult females, the symbiont was not in the stomach disc but in the lateral oviducts and the posterior pole of the oocytes due to female-specific symbiont migration. We propose the designation "Candidatus Riesia pediculicola" for the louse symbionts.

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PubMed2005

Multiple host shifts between distantly related plants, Juglandaceae and Ericaceae, in the leaf-mining moth Acrocercops leucophaea complex (Lepidoptera: Gracillariidae).

Insect herbivores such as gall formers and leaf miners are often highly specialized and adapted to their respective natal host plants. Due to the specialization and adaptation, it is presumed that host shifts readily occur among closely related plant species. Leaf-mining moths, the Acrocercops leucophaea complex, consist of three species, A. leucophaea, A. defigurata, and A. transecta. Larvae of all the species of the complex feed on Juglandaceae plants, but A. leucophaea and A. transecta are also associated with an Ericaceae plant, which is quite distantly related to Juglandaceae. Such a host utilization as in this species complex is very rare among phytophagous insects. In the present study, we estimate the history of host shifts by reconstructing the phylogeny of the A. leucophaea complex using molecular data (partial sequence of mitochondrial COI, 12S rDNA, and ND5). Parsimony and maximum likelihood analyses indicated that the common ancestor of the A. leucophaea complex used Juglandaceae only, and that the association with Ericaceae has evolved in A. leucophaea and A. transecta independently. Parametric bootstrap analysis also supported multiple origins of the association with Ericaceae in this complex. These results imply that there are ecological and biochemical factors that promote host shifting between Juglandaceae and Ericaceae despite the two families being not closely related.

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PubMed2005

Aligned 18S for Zoraptera (Insecta): phylogenetic position and molecular evolution.

The order Zoraptera (angel insects) is one of the least known insect groups, containing only 32 extant species. The phylogenetic position of Zoraptera is poorly understood, but it is generally thought to be closely related to either Paraneoptera (hemipteroid orders: booklice, lice, thrips, and bugs), Dictyoptera (blattoid orders: cockroaches, termites, and mantis), or Embioptera (web spinners). We inferred the phylogenetic position of Zoraptera by analyzing nuclear 18S rDNA sequences, which we aligned according to a secondary structure model. Maximum likelihood and Bayesian analyses both supported a close relationship between Zoraptera and Dictyoptera with relatively high posterior probability. The 18S sequences of Zoraptera exhibited several unusual properties: (1) a dramatically increased substitution rate, which resulted in very long branches; (2) long insertions at helix E23; and (3) modifications of secondary structures at helices 12 and 18.

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PubMed2004

Multiple origins of parasitism in lice.

A major fraction of the diversity of insects is parasitic, as herbivores, parasitoids or vertebrate ectopara sites. Understanding this diversity requires information on the origin of parasitism in various insect groups. Parasitic lice (Phthiraptera) are the only major group of insects in which all members are permanent parasites of birds or mammals. Lice are classified into a single order but are thought to be closely related to, or derived from, book lice and bark lice (Psocoptera). Here, we use sequences of the nuclear 18S rDNA gene to investigate the relationships among Phthiraptera and Psocoptera and to identify the origins of parasitism in this group (termed Psocodea). Maximum-likelihood (ML), Bayesian ML and parsimony analyses of these data indicate that lice are embedded within the psocopteran infraorder Nanopsocetae, making the order Psocoptera paraphyletic (i.e. does not contain all descendants of a single common ancestor). Furthermore, one family of Psocoptera, Liposcelididae, is identified as the sister taxon to the louse suborder Amblycera, making parasitic lice (Phthiraptera) a polyphyletic order (i.e. descended from two separate ancestors). We infer from these results that parasitism of vertebrates arose twice independently within Psocodea, once in the common ancestor of Amblycera and once in the common ancestor of all other parasitic lice.

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PubMed2004

The first record of sucking louse, Neohaematopinus callosciuri, infesting pallas squirrels in Japan.

A species of sucking louse, Neohaematopinus callosciuri, was found for the first time in Japan. The species was found on an invasive species of squirrel, Pallas squirrel, Callosciurus erythraeus, in the Kamakura district, Kanagawa Prefecture, Japan. A total of 52 lice were obtained from 22 of 104 squirrels captured. The lice were about three times more prevalent in male squirrels than in females and were detected most frequently in the winter. As N. callosciuri has never been reported on wild animals in Japan, this species probably was introduced into Japan along with their host, Pallas squirrels.

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PubMed2003

Phylogenetic position of Phthiraptera (Insecta: Paraneoptera) and elevated rate of evolution in mitochondrial 12S and 16S rDNA.

Phthiraptera (chewing and sucking lice) and Psocoptera (booklice and barklice) are closely related to each other and compose the monophyletic taxon Psocodea. However, there are two hypotheses regarding their phylogenetic relationship: (1) monophyletic Psocoptera is the sister group of Phthiraptera or (2) Psocoptera is paraphyletic, and Liposcelididae of Psocoptera is the sister group of Phthiraptera. Each hypothesis is supported morphologically and/or embryologically, and this problem has not yet been resolved. In the present study, the phylogenetic position of Phthiraptera was examined using mitochondrial 12S and 16S rDNA sequences, with three methods of phylogenetic analysis. Results of all analyses strongly supported the close relationship between Phthiraptera and Liposcelididae. Results of the present analyses also provided some insight into the elevated rate of evolution in mitochondrial DNA (mtDNA) in Phthiraptera. An elevated substitution rate of mtDNA appears to originate in the common ancestor of Phthiraptera and Liposcelididae, and directly corresponds to an increased G+C content. Therefore, the elevated substitution rate of mtDNA in Phthiraptera and Liposcelididae appears to be directional. A high diversity of 12S rDNA secondary structure was also observed in wide range of Phthiraptera and Liposcelididae, but these structures seem to have evolved independently in different clades.

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