The Heterochromatin Block That Functions as a Rod Cell Microlens in Owl Monkeys Formed within a 15-Myr Time Span

In rod cells of many nocturnal mammals, heterochromatin localizes to the central region of the nucleus and serves as a lens to send light efficiently to the photoreceptor region. The genus Aotus (owl monkeys) is commonly considered to have undergone a shift from diurnal to nocturnal lifestyle. We recently demonstrated that rod cells of the Aotus species Aotus azarae possess a heterochromatin block at the center of its nucleus. The purpose of the present study was to estimate the time span in which the formation of the heterochromatin block took place. We performed three-dimensional hybridization analysis of the rod cell of another species, Aotus lemurinus. This analysis revealed the presence of a heterochromatin block that consisted of the same DNA components as those in A. azarae. These results indicate that the formation was complete at or before the separation of the two species. Based on the commonly accepted evolutionary history of New World monkeys and specifically of owl monkeys, the time span for the entire formation process was estimated to be 15 Myr at most

Morphometric geographic variation in the Asian lesser white-toothed shrew Crocidura shantungensis (Mammalia, Insectivora) in East Asia

This study investigated geographic variation in the Asian lesser white-toothed shrew, Crocidura shantungensis Miller, 1901, among a number of localities in East Asia, including the Korean Peninsula, Tsushima Island, Cheju Island, and Taiwan, using univariate and multivariate analyses of cranial morphometric characters. Sexual differences were found in Taiwanese shrews, but were not evident in those from Korea or Tsushima. The samples from Taiwan had a larger overall cranial size than those from Korea and Tsushima, and were well separated from the latter two samples in the discriminant analyses. The overall size of the Cheju shrews was also greater, but lay within the variation of those from Taiwan. Crocidura dsinezumi quelpartis Kuroda, 1934, described from Cheju Island, is actually a junior synonym of C. shantungensis, and is not related to C. dsinezumi

Phylogenetic relationships of three species within the family Heligmonellidae (Nematoda; Heligmosomoidea) from Japanese rodents and a lagomorph based on the sequences of ribosomal DNA internal transcribed spacers, ITS-1 and ITS-2

Nematodes of the family Heligmonellidae (Heligmosomoidea; Trichostrongylina) reside in the digestive tracts of rodents and lagomorphs. Although this family contains large numbers of genera and species, genetic information on the Heligmonellidae is very limited. We collected and isolated adult worms of three species in Japan that belong to the family Heligmonellidae, namely Heligmonoides speciosus (Konno, 1963) Durette-Desset, 1970 (Hs) from Apodemus argenteus, Orientostrongylus ezoensis Tada, 1975 (Oe) from Rattus norvegicus and Lagostrongylus leporis (Schulz, 1931) (Ll) from Pentalagus furnessi, and sequenced the entire internal transcribed spacer regions, ITS-1 and ITS-2 of ribosomal DNA. ITS-1 of Hs, Oe and Ll was 426, 468 and 449 bp in length, and had a G＋C content of about 41, 41 and 37 %, respectively. ITS-2 of Hs, Oe and Ll was 297, 319 and 276 bp in length and had a G＋C content of about 38, 40 and 28%, respectively. The data of Hs, Oe and Ll were compared with those of two other known species within the family Heligmonellidae, Calorinensis minutus (Dujardin, 1845) (Cm) and Nippostrogylus brasiliensis (Travassos, 1914) (Nb), and with those of two species of Heligmosomidae (Heligmosomoidea), Heligmosomoides polygyrus bakeri and Ohbayashinema erbaevae. Phylogenetic analysis placed Hs, Oe and Ll in the same clade with Cm and Nb, forming a Heligmonellidae branch in both ITS-1 and ITS-2, separate from the Heligmosomoidea branch. These results demonstrated that the ITS-1 and ITS-2 sequences are useful for differentiating the Heligmonellidae nematode species. This study is the first to describe the ITS-1 and ITS-2 sequences of Hs, Oe and Ll

Unique structural characteristics and evolution of a cluster of venom phospholipase A2 isozyme genes of Protobothrops flavoviridis snake

Protobothrops flavoviridis (Crotalinae) venom gland phospholipase A2 (PLA2) isozyme genes have evolved in an accelerated manner to acquire diverse physiological activities in their products. For elucidation of the multiplication mechanism of PLA2 genes, a 25,026 bp genome segment harboring five PLA2 isozyme genes was obtained from Amami-Oshima P. flavoviridis liver and sequenced. The gene PfPLA 2 encoded [Lys49] LA2 called BPII, the gene PfPLA 4 neurotoxic [Asp49]PLA2 called PLA-N, the gene PfPLA 5 basic [Asp49]PLA2 called PLA-B, and PfPLA 1(Ï¿) and PfPLA 3(Ï¿) were the inactivated genes. The 5' truncated reverse transcriptase (RT) elements, whose intact forms constitute long interspersed nuclear elements (LINEs), were found in close proximity to the 3' end of PLA2 genes and named PLA2 gene-coupled RT fragments (PcRTFs). The facts that PcRTFs have the stemâ¿¿loop and repetitive sequence in the 3' untranslated region (UTR) which is characteristic of CR1 LINEs suggest that PcRTFs are the debris of P. flavoviridis ancestral CR1 LINEs, denoted as PfCR1s. Since the associated pairs of PLA2 genes and PcRTFs are arranged in tandem in the 25,026 bp segment, it is thought that an ancestral PLA2 gene-PfCR1 unit (PfPLA-PfCR1) which was produced by retrotransposition of PfCR1 by itself to the 3' end of PLA2 gene duplicated several times to form a multimer of PfPLA-PfCR1, a cluster of PLA2 genes, in the period after Crotalinae and Viperinae snakes branched off. Recombinational hot spot of a 37 bp segment, named Scomb, was found in the region 548 bp upstream from the TATA box of PLA2 genes. Thus, it could be assumed that multiplication of PfPLA-PfCR1 occurred by unequal crossing over of the segment, -Scomb-PfPLA-PfCR1-Scomb-. The PfCR1 moieties were afterward disrupted in the 5' portion to PcRTFs. The detection of two types of PcRTFs different in length which were produced by elimination of two definitive sequences in PfCR1 moiety possibly by gene conversion clearly supports such process but not multiplication of the PLA2 gene-PcRTF unit

The Finding of a Group IIE Phospholipase A2 Gene in a Specified Segment of Protobothrops flavoviridis Genome and Its Possible Evolutionary Relationship to Group IIA Phospholipase A2 Genes

The genes encoding group IIE phospholipase A2, abbreviated as IIE PLA2, and its 5' and 3' flanking regions of Crotalinae snakes such as Protobothrops flavoviridis, P. tokarensis, P. elegans, and Ovophis okinavensis, were found and sequenced. The genes consisted of four exons and three introns and coded for 22 or 24 amino acid residues of the signal peptides and 134 amino acid residues of the mature proteins. These IIE PLA2s show high similarity to those from mammals and Colubridae snakes. The high expression level of IIE PLA2s in Crotalinae venom glands suggests that they should work as venomous proteins. The blast analysis indicated that the gene encoding OTUD3, which is ovarian tumor domain-containing protein 3, is located in the 3' downstream of IIE PLA2 gene. Moreover, a group IIA PLA2 gene was found in the 5' upstream of IIE PLA2 gene linked to the OTUD3 gene (OTUD3) in the P. flavoviridis genome. It became evident that the specified arrangement of IIA PLA2 gene, IIE PLA2 gene, and OTUD3 in this order is common in the genomes of humans to snakes. The present finding that the genes encoding various secretory PLA2s form a cluster in the genomes of humans to birds is closely related to the previous finding that six venom PLA2 isozyme genes are densely clustered in the so-called NIS-1 fragment of the P. flavoviridis genome. It is also suggested that venom IIA PLA2 genes may be evolutionarily derived from the IIE PLA2 gene