Spectral Sensitivity of the Hawaiian Saddle Wrasse, Thalassoma duperrey, and Implications for Visually Mediated Behaviour on Coral Reefs

Although tropical coral reefs are one of the most spectrally complex habitats, there is relatively little known about colour vision of reef fish. In this study, we measured the spectral sensitivity of an endemic Hawaiian coral reef fish, Thalassoma duperrey (family Labridae), and assessed the possible role of visual sensitivity in mediating intraspecific communication. Electrophysiological recordings of compound action potentials from retinal ganglion cells were used to generate spectral sensitivity curves for specific wavelengths (380–620nm). We found at least 2 sensitivity peaks for the on response (_max=460, 550nm). The off response lacked a short wavelength mechanism but a medium wavelength mechanism (_max=545nm) and a longwave mechanism (_max=570nm) were found. To quantify the visual stimulus provided by a conspecific individual, spectral reflectance from the colour pattern of T. duperrey was measured with a spectroradiometer. Luminance and spectral contrast were computed between colour patches of the pattern and between the patches and natural backgrounds (i.e., water and coral). Reflectance from the blue head and contrast from the blue, green and red patches matched the sensitivity maxima of T. duperrey, although this depended on the type of background. Our results indicate that T. duperrey should be able to visually detect the colour pattern of a conspecific fish and that T. duperrey's visual system is designed to enhance target detection in the coral reef habitat with matched and offset cone mechanisms.     

Biosynthesis,accumulation and emission of carotenoids, α-tocopherol,plastoquinone, and isoprene in leaves under high photosynthetic irradiance

The localization of isoprenoid lipids in chloroplasts, the accumulation of particular isoprenoids under high irradiance conditions, and channelling of photosynthetically fixed carbon into plastidic thylakoid isoprenoids, volatile isoprenoids, and cytosolic sterols are reviewed. During leaf and chloroplast development in spring plastidic isoprenoid biosynthesis provides primarily thylakoid carotenoids, the phytyl side-chain of chlorophylls and the electron carriers phylloquinone K1, alpha-tocoquinone and alpha-tocopherol, as well as the nona-prenyl side-chain of plastoquinone-9. Under high irradiance, plants develop sun leaves and high light (HL) leaves with sun-type chloroplasts that possess, besides higher photosynthetic CO2 assimilation rates, different quantitative levels of pigments and prenylquinones as compared to shade leaves and low light (LL) leaves. After completion of chloroplast thylakoid synthesis plastidic isoprenoid biosynthesis continues at high irradiance conditions, constantly accumulating alpha-tocopherol (alpha-T) and the reduced form of plastoquinone-9 (PQ-9H2) deposited in the steadily enlarging osmiophilic plastoglobuli, the lipid reservoir of the chloroplast stroma. In sun leaves of beech (Fagus) and in 3-year-old sunlit Ficus leaves the level of alpha-T and PQ-9 can exceed that of chlorophyll b. Most plants respond to HL conditions (sun leaves, leaves suddenly lit by the sun) with a 1.4-2-fold increase of xanthophyll cycle carotenoids (violaxanthin, zeaxanthin, neoxanthin), an enhanced operation of the xanthophyll cycle and an increase of beta-carotene levels. This is documented by significantly lower values for the weight ratio chlorophylls to carotenoids (range: 3.6-4.6) as compared to shade and LL leaves (range: 4.8-7.0). Many plant leaves emit under HL and high temperature conditions at high rates the volatile compounds isoprene (broadleaf trees) or methylbutenol (American ponderosa pines), both of which are formed via the plastidic 1-deoxy-D: -xylulose-phosphate/2-C-methylerythritol 5-phosphate (DOXP/MEP) pathway. Other plants by contrast, accumulate particular mono- and diterpenes. Under adequate photosynthetic conditions the chloroplastidic DOXP/MEP isoprenoid pathway essentially contributes, with its C5 isoprenoid precusors, to cytosolic sterol biosynthesis. The possible cross-talk between the two cellular isoprenoid pathways, the acetate/MVA and the DOXP/MEP pathways, that preferentially proceeds in a plastid-to-cytosol direction, is shortly discussed.     

Foraging tactics in alternative heterochronic salamander morphs: trophic quality of ponds matters more than water permanency

1. In lentic freshwater habitats, the composition of animal assemblages shifts along a gradient from temporary to permanent basins. When habitats with different degrees of permanence are at the scale of the home range of species, they constitute alternatives in terms of energy acquisition through feeding. 2. In this context, previous studies showed an advantage of metamorphic over paedomorphic tiger salamanders (Ambystoma tigrinum) in temporary ponds which are only available to metamorphs. The aim of this study was to establish whether salamanders obtain similar benefits in ponds that do not differ in water permanence and whether salamanders shifted from detrimental to advantageous ponds. To this end, we determined the feeding habits, body condition and movement patterns of the two morphs in a complex of four permanent and four temporary ponds. 3. Consistent with previous studies, metamorphs consumed higher‐quality diets than paedomorphs in term of energy intake. However, these differences occurred because metamorphs consumed fairy shrimp in a single temporary pond. Individual movement patterns confirmed that most of the metamorphs used different aquatic habitats both within and between years and that most of them moved from permanent ponds for breeding towards the most profitable temporary pond in terms of foraging. 4. These results indicate that habitat selection by salamanders is optimal in term of energy intake in metamorphs that use high quality ponds independently of hydroperiod. It seems that both spatial and temporal variation can influence the relative foraging success of each morph.     

酶法催化降解2,4,6-三硝基甲苯的研究进展

2,4,6-三硝基甲苯(TNT)作为一种广泛使用的含能材料,发挥巨大作用的同时也给环境带来了严重的污染,对人类健康构成一定威胁。目前国内外的TNT处置主要有物理、化学、生物及酶法等方法,其中酶法作为一种新兴的方法,显示了良好的应用潜力,受到研究者的广泛关注,。比较了各类处理方法的优缺点,重点介绍近年来涉及TNT降解的酶学研究进展,并对酶法在TNT废水处理和土壤修复中的应用前景进行展望。     

Recolonisation patterns of benthic invertebrates: a field investigation of restored former sewage channels

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Biological evidence against the panspermia theory

The following idea is analysed. Given that evolution on Earth seems to have passed through protocellular evolutionary stages of progenotes, this would appear to be incompatible with the panspermia theory because this observation would imply that the infection bringing life to the Earth started in these protocells, for which a low or null infective power is generally expected.     

Evolutionary pathways to self-fertilization in a tristylous plant species

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Hedgehog and Wnt coordinate signaling in myogenic progenitors and regulate limb regeneration

Amphibians have a remarkable capacity for limb regeneration. Following a severe injury, there is complete regeneration with restoration of the patterning and cellular architecture of the amputated limb. While studies have focused on the structural anatomical changes during amphibian limb regeneration, the signaling mechanisms that govern cellular dedifferentiation and blastemal progenitors are unknown. Here, we demonstrate the temporal and spatial requirement for hedgehog (Hh) signaling and its hierarchical correlation with respect to Wnt signaling during newt limb regeneration. While the dedifferentiation process of mature lineages does not depend on Hh signaling, the proliferation and the migration of the dedifferentiated cells are dependent on Hh signaling. Temporally controlled chemical inactivation of the Hh pathway indicates that Hh-mediated antero-posterior (AP) specification occurs early during limb regeneration and that Hh is subsequently required for expansion of the blastemal progenitors. Inhibition of Hh signaling results in G0/G1 arrest with a concomitant reduction in S-phase and G2/M population in myogenic progenitors. Furthermore, Hh inhibition leads to reduced Pax7-positive cells and fewer regenerating fibers relative to control tissue. We demonstrate that activation of Wnt signaling rescues the inhibition of Hh pathway mainly by enhancing proliferative signals, possibly mediated through TCF4 activity. Collectively, our results demonstrate coordinated signaling of Hh and Wnt activities in regulating blastemal progenitors and their hierarchical positioning during limb regeneration.     

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