Summer forage biomass and the importance of litterfall for a high-density sika deer population

The biomass of summer forage and their contributions were surveyed to show that litterfall supported a high-density population of sika deer (Cervus nippon Temminck) in summer on Nakanoshima Island, Toya Lake, Japan. In July 1974, the grassland had the highest productivity among understory vegetations (228±55kgha^–1: mean±SE). In deciduous forests, palatable plants occupied only 0.1% of the biomass of 0.872±0.366kgha^–1, and deciduous leaves within the reach of deer (=220cm at height) produced 0.208±0.070kgha^–1. However, litterfall during this period had the highest productivity, 28.7± 5.3kgha^–1. The deer consumed litterfall (75.6% in dry weight), short grasses (17.2%), deciduous forest understory (4.1%), deciduous leaves within the reach of deer (3.0%) and conifer plantation under story (0.1%). It is suggested that the high-density deer population would be maintained by litterfall through the year instead of browsing in deciduous forests, which has been overlooked.     

Amphibian chytridiomycosis in Japan: distribution,haplotypes and possible route of entry into Japan

A serious disease of amphibians caused by the chytrid fungus Batrachochytrium dendrobatidis was first found in Japan in December 2006 in imported pet frogs. This was the first report of chytridiomycosis in Asia. To assess the risk of pandemic chytridiomycosis to Japanese frogs, we surveyed the distribution of the fungus among captive and wild frog populations. We established a nested PCR assay that uses two pairs of PCR primers to amplify the internal transcribed spacer (ITS) region of a ribosomal RNA cassette to detect mild fungal infections from as little as 0.001 pg (1 fg) of B. dendrobatidis DNA. We collected swab samples from 265 amphibians sold at pet shops, 294 bred at institutes and 2103 collected at field sites from northern to southwestern Japan. We detected infections in native and exotic species, both in captivity and in the field. Sequencing of PCR products revealed 26 haplotypes of the B. dendrobatidis ITS region. Phylogenetic analysis showed that three of these haplotypes were specific to the Japanese giant salamander (Andrias japonicus) and appeared to have established a commensal relationship with this native amphibian. Many other haplotypes were carried by alien amphibians. The highest genetic diversity of B. dendrobatidis was found in the American bullfrog (Rana catesbeiana). Some strains of B. dendrobatidis appeared to be endemic to Japanese native amphibians, but many alien strains are being introduced into Japan via imported amphibians. To improve chytridiomycosis risk management, we must consider the risk of B. dendrobatidis changing hosts as a result of anthropogenic disturbance of the host‐specific distribution of the fungus.     

Phylogeography of the Japanese giant flying squirrel, Petaurista leucogenys (Rodentia: Sciuridae): implication of glacial refugia in an arboreal small mammal in the Japanese Islands

To test the association between temperate forest dynamics and glacial refugia for arboreal small mammals, we studied the phylogeography of the Japanese giant flying squirrel ( Petaurista leucogenys ) using complete mitochondrial cytochrome b gene sequences (1140 bp). This squirrel is endemic to three of Japan's main islands: Honshu, Shikoku, and Kyushu. We examined 58 specimens of P. leucogenys collected from 40 localities in Japan. Additionally, two individuals with unknown sampling localities were included in phylogenetic analyses. There were 54 haplotypes of P. leucogenys. We found five major phylogroups (Northern, Central, South-eastern, South-western, and Southern). These phylogroups may have originated from glacial refugia during the Late Pleistocene. After the last glaciation, the Northern phylogroup, widely distributed in eastern Japan, could have extensively expanded northward from its refugia. By contrast, in western Japan, population expansion was restricted to western Japan. All members of four phylogroups existed in western Japan during glaciations. The complicated phylogeographical pattern of P. leucogenys populations originating from western Japan may have resulted from the long history.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 47–60.     

Macronuclear Regeneration and Cell Division in Paramecium caudatum

SYNOPSIS. In Paramecium caudatum , occurrence of macronuclear regeneration is closely related to the time of feeding after conjugation. Macronuclear regeneration is induced with a high frequency when conjugating pairs are transferred into fresh culture medium. Feeding immediately after conjugation induces early cell division and 3 or more fissions occur without macronuclear division because of the inability of the macronuclear anlagen to divide. In the cells lacking normal macronuclear anlagen, old macronuclear fragments undergo regeneration and form vegetative macronuclei.     

SPECIES-SPECIFIC ADHESION OF SPERMATOZOA TO THE SURFACE OF FIXED EGGS IN SEA URCHINS

When the spermatozoa of sea urchins are added to eggs which have been fixed with glutaraldehyde and washed thoroughly, the spermatozoa swarm around the eggs and adhere to the egg surface. The mode of sperm adhesion to the fixed egg is assumed, on the evidence of electron-microscopical studies, to be the same as that of adhesion to the intact egg at the initial stage of normal fertilization. The spermatozoa and fixed eggs of five species of sea urchins were combined and heterologous crosses were studied. Species-specific adhesion of sperm to fixed eggs was clearly demonstrated. There is a direct relationship between the cross-fertilization of living gametes and the binding capacity of spermatozoa and fixed eggs in so far as the employed five species are concerned.     

EMBRYO AND ORGAN CULTURES OF THE HORSESHOE CRAB,TACHYPLEUS TRIDENTATUS*

This paper deals with some preliminary technical experiments on cultures of the embryos and organs of Tachypleus tridentatus. In embryo culture, using the embryos at various stages of development, embryonic areas with hardly any yolk remaining in them were cultured in various media and by various methods (Series A); hemispheres of embryos containing the embryonic area (Series B) and whole embryos without egg membranes (Series C) were cultured in sterilized sea water. The suitability of the culture media and methods is described; the medium containing calf serum or 199, and the hanging-drop method were found to be the most appropriate of those used in respective series of experiments. The changes in external and internal structures of the explants from embryos at various developmental stages cultured in various media and by various methods are described; dorsal closure, secretion of inner egg membrane, thickening of the cell layer and the elongation of limb buds were all observed in the Series A experiments. In Series B and C, coelom formation and also normal development of the embryos cultured after the 2nd embryonic moulting were observed. In organ culture, fragments of the embryonic heart were cultured in various media and by various methods. The hanging-drop method resulted in longer survival than the method using agar media.     

Studies on ribonucleic acids from Chlorella protothecoides with special reference to the degradation of chloroplast RNA during the process of "glucose-bleaching"

By growing Chlorella protothecoides under certain nutritionaland light conditions the following three different types ofalgal cells were obtained: (i) normal "green" cells grown ina medium rich in a nitrogen source (urea) and poor in glucoseunder illumination, (ii) "etiolated" cells cultivated in thesame medium in darkness, and (iii) "glucose-bleached" cellsgrown, in the light or in darkness, in a medium rich in glucoseand poor in the nitrogen source. The "glucose-bleached" cellscontain profoundly degenerated plastids, and the "etiolated"cells have only partially organized plastids. From these algalcells RNA was extracted by the cold phenol method, and fractionatedby MAK column chromatography and sucrose density gradient centrifugation,making use of ³²P-labelled E. coli RNA as the internal marker.It was found that in comparison with the green cells that arerich in chloroplast ribosomal RNA as well as in nonchloroplastic("cytoplasmic") ribosomal RNA, the etiolated cells possess acomparable amount of "cytoplasmic" rRNA but a significantlylesser amount of chloroplast rRNA. Both types of rRNA existat extremely low levels in the glucose-bleached cells. During the process of bleaching (chloroplast degeneration) ofthe green cells induced by the addition of a high concentrationof glucose, marked changes were observed in the patterns offractionation of RNA as followed by the above procedures. Itwas disclosed that the chloroplast rRNA is rapidly degradedduring an early phase of the bleaching process, while the quantityof "cytoplasmic" rRNA remained almost unaltered. ¹Part of this work was reported at the Symposium on Cell Differentiationsponsored by the Institute of Applied Microbiology, Universityof Tokyo, in November 1965, and at the Symposium on Biogenesisof Subcellular Particles, the 7th Internatl. Congress of Biochemistry,Tokyo, 1967. ²Present address: Faculty of Pharmaceutical Sciences, Universityof Hokkaido, Sapporo.