Different phylogeographic patterns in two Japanese Silpha species (Coleoptera: Silphidae) affected by climatic gradients and topography

To reveal differences in phylogeographic patterns of flightless insect species occurring in different regions of Japan, we studied the phylogeography and demographic history of Silpha beetles occurring in cool-temperate habitats of two major islands, Honshu and Hokkaido, using sequences of the mitochondrial cytochrome oxidase subunit I (COI) gene. Honshu has a more mountainous topography, and cool-temperate habitats occur discontinuously, whereas Hokkaido, located to the north of Honshu, has more continuous cool-temperate habitats. A species endemic to Honshu, S. longicornis occurs on Honshu, whereas S. perforata occurs on Hokkaido and the East Asian continent. Our results indicate that the ancestors of S. longicornis colonized Honshu via a south-west route c . 0.7 Mya and the species has highly divergent populations in isolated mountainous areas of Honshu, whereas S. perforata colonized Hokkaido via a northern route less than 90 000 years ago and has less divergent geographic populations. During the last glacial period, S. perforata was probably restricted to refugia in southern Hokkaido and later expanded into northern Hokkaido, whereas S. longicornis populations existed in many isolated refugia, probably because of the complex topography of Honshu. Thus, our study demonstrates that, even between closely related species, interactions among biology, latitudinal climatic gradients and topography can produce different phylogeographic patterns.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 452–467.     

Selective light transmittance of translucent bracts in the Himalayan giant glasshouse plant Rheum nobile Hook. f. & Thomson (Polygonaceae)

Translucent bract transmittance of ultraviolet (UV) to infrared (IR) radiation (between 320 and 800 nm) and leaf anatomy were examined in a glasshouse plant, Rheum nobile Hook. f. & Thomson (Polygonaceae) to assess the function of avoiding injury by UV radiation while keeping the inflorescence warm by photosynthetically active (PA) and IR radiation. Although the translucent bracts and rosulate leaves transmitted little UV radiation, the former always transmit more PA and IR radiation. Additionally, the bracts transmit much more scattered solar radiation than direct radiation. The bracts are also anatomically different from the rosulate leaves. They have two or three layers of mesophyll cells with neither palisade nor spongy parenchymatous cells; in addition, the uppermost layer of mesophyll and the epidermis stain easily, and both are thought to play a role in attenuating UV radiation. The leaf epidermis of many land plants has UV absorbing pigments such as flavonoids, which absorb almost all UV radiation. Thus the role of the bracts of R. nobile is to protect the reproductive organs by absorbing UV radiation and to keep them warm by transmitting PA and IR radiation. The bracts are believed to have adapted function and form to the environment, in particular, to the weather conditions of the eastern Himalaya.     

Maturation-Inducing Substances in Asteroid and Echinoid Oocytes

In starfish a hormonal peptide, gonad-stimulating substance(GSS), which is released from nervous tissue, acts on the gonadto produce a maturation-inducing substance (MIS), an inducerof oocyte maturation and spawning. MIS is 1-methyladenine (1-MA).This substance acts on the surface of the oocyte. Cytoplasmicmaturation as revealed by fertilizability is also induced by1-MA. The amount of 1-MA can be determined very accurately witha bioassay method using isolated oocytes. In 1-MA formation,GSS seems to enhance the methylation of some compound whichcontains a purine nucleus at its N1 site. The methyl donor isprobably S-adenosylmethionine. 1-Methylated precursor seemsto be transformed to 1-methyl AMP and then hydrolyzed into 1-methyladenosineand phosphate by phosphomonoesterase. 1-Methyladenosine is finallysplit into 1-MA and ribose by 1-methyladenosine ribohydrolase.So-called spontaneous maturation of oocytes isolated in seawater is due to the action of 1-MA produced in follicle cellseven in the absence of GSS. 1-MA is present in echinoid gonadsand seems to act as MIS also in these animals. Disulfidereducingagents such as dithiothreitol and 2,3-dimercapto-1-propanolinduce starfish oocyte maturation. On the other hand, sulfhydrylreagents such as p-chloromercuribenzoate, iodoacetamide, andN-ethylmaleimide suppressed 1-MA-induced oocyte maturation.Since Concanavalin A acts on the follicle cells to produce 1-MA,the action of this substance seems to be quite similar to thatof GSS.     

CORTICAL AND SUBCORTICAL CHANGES PRECEDING FURROW FORMATION IN THE CLEAVAGE OF NEWT EGGS

In the first cleavage of the egg of the newt, Cynops(Triturus) pyrrhogaster, some sort of preparation for the furrow formation in the cortical and subcortical cytoplasm precedes the advancing tip of the cleavage furrow. This is shown by the following facts: (1) Incisions made close to the tip of the cleavage furrow do not stop the progress of furrowing, allowing the furrow to cross the incisions and appear on the farther sides, while incisions made far enough from the furrow tip always prevent the further travelling of the furrow, (2) Displacement of the subcortical cytoplasm ahead of the furrow by rubbing with a hair loop makes the furrow bend corresponding to the width of the rubbed area, and (3) Transplantation of the subcortical material of the furrow tip to lateral parts in the same egg causes a depression in the overlying cortex at the transplanted position. The linear extension of the prepared area for the furrow formation is the longest in the animal hemisphere and it decreases in gradient towards the vegetal pole.     

INDUCTION OF SPAWNING AND OOCYTE MATURATION IN STARFISH BY 1-METHYL-ADENOSINE MONOPHOSPHATE

l-Methyladenosine monophosphate (l-McAMP) induces ovulation and oocyte maturation when applied to isolated ovarian fragments of Asterina pectinifera . However, isolated oocytes fail to mature even in the presence of this substance. When ovarian or testis fragments are incubated with l-McAMP, the supernatant of the incubation mixture acquires the maturation-inducing activity. Also, superantants of gonadal homogenates incubated with l-McAMP have the capacity to convert it to a maturation-inducing substance, suggesting that l-McAMP is decomposed to l-methyladenine, which is believed to be a general inducer of oocyte maturation and ovulation in starfishes. Thus l-MeAMP seems to be an intermediate in l-methyladenine formation when the latter is produced under the influence of the gonad-stimulating hormonal peptide.     

The Inhibitory Effect of Glabridin from Licorice Extracts on Melanogenesis and Inflammation

Glabridin is the main ingredient in hydrophobia fraction of licorice extract affecting on skins. In this study, we investigated inhibitory effects of glabridin on melanogenesis and inflammation using cultured B16 murine melanoma cells and guinea pig skins. The results indicated that glabridin inhibits tyrosinase activity of these cells at concentrations of 0.1 to 1.0 μg/ml and had no detectable effect on their DNA synthesis. Combined analysis of SDS-polyacrylamide gel electrophoresis and DOPA staining on the large granule fraction of these cells disclosed that glabridin decreased specifically the activities of Tl and T3 tyrosinase isozymes. It was also shown that UVB-induced pigmentation and erythema in the skins of guinea pigs were inhibited by topical applications of 0.5% glabridin. Anti-inflammatory effects of glabridin in vitro were also shown by its inhibition of superoxide anion productions and cyclooxygenase activities. These data indicated that glabridin is a unique compound possessing more than one function; not only the inhibition of melanogenesis but also the inhibition of inflammation in the skins. By replacing each of hydroxyl groups of glabridin with others, it was revealed that the inhibitory effect of 2′-O-ethyl glabridin was significantly stronger than that of 4′-O-ethyl-glabridin on melanin synthesis in cultured B16 cells at the concentration of 1.0 mg/inl. With replacement of both of two hydroxyl groups, the inhibitory effect was totally lost. Based on these data, we concluded that two hydroxyl groups of glabridin are important for the inhibition of melanin synthesis and that the hydroxyl group at the 4’ position of this compound is more closely related to melanin synthesis.     

Development of Melanocyte Progenitors in Murine Steel Mutant Neural Crest Explants Cultured With Stem Cell Factor,Endothelin-3, or TPA

Stem cell factor (SCF) has been suggested to be indispensable for the development of neural crest cells into melanocytes because Steel mutant mice (i.e., Sl/Sf¹) have no pig-mented hairs. On the other hand, it has been demonstrated that the addition of endothelin 3 (ET-3) or TPA to neural crest cell cultures can induce melanocyte differentiation without addition of extrinsic SCF. In this study, we excluded the influence of intrinsic SCF by using SI/SI mouse embryos to study more precisely the effects of natural cytokines, such as extrinsic soluble SCF or ET-3, or chemical reagents, such as TPA or cholera toxin. We found that SCF is supplied within the wild-type neural crest explants and that ET-3 cannot induce melanocyte differentiation or proliferation without SCF. These results indicate that SCF plays a critical role in survival or G1/S entry of melanocyte progenitors and that SCF initially stimulates their proliferation and then ET-3 accelerates their proliferation and differentiation. TPA has the ability to elicit neural crest cell differentiation into melanocytes without exogenously added SCF but it is not as effective as SCF because many more melanocytes developed in the wild-type neural crest explants cultured with TPA.     

Morphological difference and reproductive isolation: morphometries in the millipede Parafontaria tonominea and its allied forms

Thin-plate spline and other multivariate statistical methods were used to examine the variation in genital morphology and body size in 74 populations of the millipede Parafontaria tonominea and its allied forms in central Japan. Although the study populations included nine sympatric pairs of two reproductively isolated forms, the variations in genital morphology and body size observed were continuous across the study group. Analyses of the sympatric pairs using bootstrapping revealed that the degree of morphological difference between sympatric populations varied considerably from pair to pair. These results demonstrate that the degree of difference in genital morphology and body size may not correspond with the establishment of reproductive isolation. Significant correlation in the pattern of geographic variation was observed for many combinations of morphological components. However, it was not possible to detect a significant correlation between morphology and geographic distance in many of the morphological components studied. This study suggests that the incorporation of genital characters in classification should be done carefully, particularly for animal groups with low vagility, such as millipedes.     

DISTRIBUTION OF MATURATION-PROMOTING FACTOR IN STARFISH OOCYTE STRATIFIED BY CENTRIFUGATION

In starfish, cytoplasm taken from maturing oocytes is capable of inducing breakdown of the germinal vesicle and subsequent maturation when injected into immature oocytes. The cytoplasmic factor has been designated as "maturation-promoting factor" (MPF). Ooplasm was stratified by centrifugation of maturing oocytes in density-graded Ficoll-seawater, without disrupting the cell. Three strata were distinguished beginning with the centripetal side: oil cap, hyaline layer and yellow layer. MPF activity was shown to be localized in the hyaline layer. Electron microscopic observation revealed that the hyaline layer contains Golgi complexes, many lucent vesicles and multi-vesicular bodies as distinct organelles, but seldom contains such inclusions as the lipid droplets forming the oil cap, mitochondria, yolk and pigment granules contained in the yellow layer. Based on these observations, a possible cytoplasmic component with MPF activity is discussed.