Seasonal variation in cone sensitivity and short-wave absorbing visual pigments in the rudd Scardinius erythrophthalmus

Summary Microspectrophotometric and electroretinographic investigation of photoreceptor spectral sensitivity in the rudd Scardinius erythrophthalmus has revealed four spectral classes of cone with peak sensitivity in the ultra-violet, violet, green and red regions of the spectrum. These peak sensitivities were found to vary seasonally, and in response to artificial illumination, as a result of a change in the ratio of A1 to A2-based visual pigment in the cells. Short daylengths favoured the A2 pigment whereas long daylengths favoured the A1 analogue. Both the ultra-violet and violet-sensitive pigments have not previously been reported for the rudd. Evidence is presented supporting the hypothesis that the ultra-violet class of cells is not present in older fish.Abbreviation rvi response versus intensity (curve)     

Visual pigments and spectral sensitivity of the diurnal gecko Gonatodes albogularis

The visual pigments and oil droplets in the retina of the diurnal gecko Gonatodes albogularis were examined microspectrophotometrically, and the spectral sensitivity under various adapting conditions was recorded using electrophysiological responses. Three classes of visual pigments were identified, with _max at about 542, 475, and 362 nm. Spectral sensitivity functions revealed a broad range of sensitivity, with a peak at approximately 530–540 nm. The cornea and oil droplets were found to be transparent across a range from 350–700 nm, but the lens absorbed short wavelength light below 450 nm. Despite the filtering effect of the lens, a secondary peak in spectral sensitivity to ultraviolet wavelengths was found. These results suggest that G. albogularis does possess the visual mechanisms for discrimination of the color pattern of conspecifics based on either hue or brightness. These findings are discussed in terms of the variation in coloration and social behavior of Gonatodes.Abbreviations ERG electroretinogram - MSP microspectrophotometry - UV ultraviolet - _max wavelength of maximum absorbance     

Leucine interference in the production of water-soluble red Monascus pigments

The formation of soluble Monascus red pigments is strongly positively and negatively regulated by different amino acids. Leucine, valine, lysine, and methionine had strong negative effects on pigment formation. Leucine supported poor pigment formation when used as sole nitrogen source in fermentations, yet it neither repressed pigment synthase(s) nor inhibited its action. The new pigments derived from the hydrophobic leucine were more hydrophilic than the conventional red pigments (lacking an amino acid side-chain) and were extracellularly produced. Therefore, the low level of red pigments produced when leucine was the nitrogen source was not due to feed-back regulation by cell-bound leucine pigments. The negative effect of leucine was caused by enhanced decay of pigment synthase(s). The enhanced decay was not due simply to de novo synthesis of a leucine-induced protease.Abbreviations mSG Monosodium glutamate - MOPS 3-(N-morpholine)propane sulfonic acid - DCW dry cell weight     

Localization of visual pigments within rhabdoms of the compound eye of Spodoptera exempta (Insecta,Noctuidae)

Summary In the noctuid moth Spodoptera exempta, the distribution of visual pigments within the fused rhabdoms of the compound eyes was investigated by electron microscopy. Each ommatidium regularly contains eight receptor cells belonging to three morphological types: one distal, six medial, and one basal cell (Meinecke 1981); four different visual pigments — absorption maxima at approximately 355, 465, 515, and 560 nm — are known to occur within the eye (Langer et al. 1979). The compound eyes were illuminated in situ by use of monochromatic light of different wavelengths. This illumination produced a wide scale of structural changes in the microvilli of the rhabdomeres of individual cells. Preparation of eyes by freeze-substitution revealed the structural changes in the rhabdomeres to be effects of light occurring in vivo.The degree of structural changes may be considerably different in rhabdomeres within the same ommatidium; it was found to depend on the wavelength and the duration of illumination, the intensity received by the ommatidia as well as the spectral sensitivity of the receptor cells. Therefore, it was possible to estimate the spectral sensitivities of the morphological types of receptor cells. Generally, all medial cells are green receptors and all basal cells red receptors; distal cells are blue receptors in about two-thirds of the ommatidia, while in the remaining third of them distal cells are sensitive to ultraviolet light.Supported by Deutsche Forschungsgemeinschaft, Sonderforschungsbereich 114 (Bionach)     

色素生物合成相关PigE基因的缺失对紫色红曲霉Mp-21黄色素种类和产量的影响

红曲色素（MPs）是红曲霉次生代谢过程中产生的具有多种生物活性的天然色素,广泛应用于食品、化妆品和保健品行业。[目的]本研究从紫色红曲霉Mp-21中克隆了一个红曲色素产生相关PigE基因,并对其功能进行了鉴定。[方法]利用同源重组原理对PigE基因进行敲除,从表型、显微结构、生长速率、红曲色素、桔霉素等方面分析基因缺失前后的生物学特征变化。[结果]PigE基因的缺失主要导致黄色素产量的提高和种类的增多。与野生型Mp-21菌株以产生红色素为主的色素混合物相比,△PigE丧失了产生红色素的能力,并且新产生了至少5种新的黄色素。△PigE液体发酵13 d后,红曲色素的总色价达到了3548.2 U/g,约为野生型Mp-21菌株的4.82倍;而△PigE桔霉素的产量没有显著变化,但产生的时间延迟。[结论]PigE基因的缺失可能阻断了黄色素向橙色素的转化途径,使△PigE更趋向于黄色素的形成。由于红色素的形成需要较复杂的条件,如培养基中的氨基酸和适宜的pH值等,△PigE更倾向于先合成黄色素,丧失了产生红色素的能力。本研究为高产黄色素基因工程红曲霉菌株的构建提供了一种可能的途径。     

Colour vision in the passeriform bird,Leiothrix lutea: correlation of visual pigment absorbance and oil droplet transmission with spectral sensitivity

The visual receptors in the retina of the passeriform bird Leiothrix lutea were examined microspectro-photometrically. The rods had a maximum absorbance close to 500 nm. Four spectrally different classes of single cone were identified with typical combinations of photopigments and oil droplets: a long-wave sensitive cone with a photopigment P568 and a droplet with a cut-off wavelength at 564 nm, a middle-wave sensitive cone with a P499 and a droplet with a cut-off at 506 nm, a short-wave sensitive cone with a P454 and a droplet with maximum absorbance below 410nm and an ultraviolet sensitive cone with a P355 and a transparent droplet. Double cones possessed a P568 in both the principal and accessory members. A pale droplet with variable absorbance (maximal at about 420 nm) was associated with the principal member whereas the ellipsoid region of the accessory member contained only low concentrations of carotenoid. The effective spectral sensitivities of the different cone classes were calculated from the characteristic combinations of oil droplets and photopigments and corrected for the absorbance of the ocular media. Comparison of these results with the behavioural spectral sensitivity function of Leiothrix lutea suggests that the increment threshold photopic spectral sensitivity of this avian species is mediated by the 4 single cone classes modified by neural opponent mechanisms.Abbreviations LWS long wave sensitive - MWS middle wave sensitive - SWS short wave sensitive (cones)     

Vegetation development at a mountain settlement site in the Swedish Scandes during the late Holocene: palaeoecological evidence of human-induced deforestation

A palaeoecological study was conducted close to the forest limit in the northern Scandinavian mountain range. The aim was to elucidate the degree to which human impact has affected the vegetation at Hiednikvalta, a Stállo settlement site. Stállo settlements consist of round hut foundations that have a hearth in the middle and are surrounded by a low turf wall. They were probably established by Sámi people using the mountain areas for hunting and/or reindeer herding. In order to separate the effects of humans and climate on the vegetation, a reference area approach was adopted, i.e. the vegetation development at the Stállo settlement site Hiednikvalta was compared with the vegetation development in a forested reference area Avvuhatjåhkkå, at the same altitude as Hiednikvalta but with no archaeological remains of settlements. Peat stratigraphies were retrieved at the two sites and pollen analysis, loss-on-ignition (LOI), pollen accumulation rates (PAR), macrofossil analysis and Betula pollen size statistics were all examined. The results indicate that Hiednikvalta was forested with Betula trees prior to the Stállo settlement period, which occurred between the eighth and thirteenth centuries. Human activities resulted in a decrease in tree cover at the site, as found in a previous study at Adamvalta, another Stállo settlement site in the region. However, the magnitude of vegetation change, and the post-Stállo vegetation development differed between the two areas, suggesting that site-specific factors are important. The use of reference areas in palynological studies is also discussed.     

The effect of agriculture on the primary production in Lake Beskie (Poland) as recorded in the stratigraphy of fossil pigments

Analysis of fossil pigments deposited in the bottom sediments of Lake Beskie, was used to assess changes in the primary productivity during the past years. Three characteristic periods of lake development were distinguished. These periods correspond with a transformation in the lake's catchment area induced by the development of agriculture. A first period was characterized by intensive inflow of allochthonous matter into the lake, due to agriculture in the catchment area, favouring soil erosion. This erosion and the subsequent increase in mineral fertilization resulted in decrease of sorption ability of the soil. This in turn led to increased leaching of nutrients into the lake which resulted in increased primary production and hypolimnetic anoxia. These high oxygen deficits were characterized by a development of photosynthetic bacteria of the genus Chlorobium, and an intensification of the lake's enrichment, mainly with phosphorus. In a final period organic fertilizers (manure) were used in the catchment area. A noticeable improvement of sorption ability of the soil occurred, migration of nutrients to the lake was inhibited, and primary productivity decreased.     

Changes of fluorescence and xanthophyll pigments during dehydration in the resurrection plantSelaginella lepidophylla in low and medium light intensities

The changes in photosynthetic efficiency and photosynthetic pigments during dehydration of the resurrection plantSelaginella lepidophylla (from the Chiuhahuan desert, S.W. Texas, USA) were examined under different light conditions. Changes in the photosynthetic efficiency were deduced from chlorophyll a fluorescence measurements (F_o, F_m, and F_v) and pigment changes were measured by HPLC analysis. A small decrease in F_v/F_m was seen in hydrated stems in high light (650 μmol photons·m⁻²·s⁻¹) but not in low light (50 μmol photons·m⁻²·s⁻¹). However, a pronounced decline in F_v/F_m was observed during dehydration in both light treatments, after one to two hours of dehydration. A rise in F_o was observed only after six to ten hours of dehydration. Concomitant with the decrease in photosynthetic efficiency during dehydration a rise in the xanthophyll zeaxanthin was observed, even in low-light treatments. The increase in zeaxanthin can be related to previously observed photoprotective non-photochemical quenching of fluorescence in dehydrating stems ofS. lepidophylla. We hypothesize that under dehydrating conditions even low light levels become excessive and zeaxanthin-related photoprotection is engaged. We speculate that these processes, as well as stem curling and self shading (Eickmeier et al. 1992), serve to minimize photoinhibitory damage toS. lepidophylla during the process of dehydration.     

Eyespot membranes in newly released zoospores of the green algaChlorosarcinopsis gelatinosa (Chlorosarcinales) and their fate during zoospore settlement

Summary Eyespot membranes in zoospores of the green algaChlorosarcinopsis gelatinosa were studied with the freeze-fracture technique. The PF of the plasmalemma overlying the eyespot lipid globules contains significantly greater numbers of intramembraneous particles (IMP; 8,200 IMP/m²) compared to other areas of the plasmalemma (2,100 IMP/m²). In the eyespot area the EF of the plasmalemma reveals no IMP, but regularly arranged depressions corresponding to the PF particles. Sizes of PF particles are not significantly different between the eyespot area and other areas of the plasmalemma. Zoospore settlement starts approximately two hours after release and involves in sequence, rounding up of the cells, retraction of the flagella and secretion of a cell wall. Eyespot membrane specializations on the PF of the plasmalemma disappear during flagellar retraction and before cell wall secretion.The functional significance of eyespot membrane specializations is discussed in accordance with the view that these membranes are engaged in photoreception and primary sensory transduction relating to green algal phototaxis.     

Correlation of spinule dynamics and plasticity of the horizontal cell spectral response in cyprinid fish retina: quantitative analysis

Summary A negative feedback interaction between luminosity type horizonatal cells (HCs) and green-sensitive cones generates the long-wavelength-sensitive depolarizing response in biphasic chromaticity type HCs. This interaction is suppressed in the dark and is potentiated by light adaptation of the retina. HCs are morphologically plastic; during light adaptation, their dendritic terminals within cone pedicles extend, giving rise to spinules. This paper examines whether there is a quantitative correlation between the time course of light-dependent formation of the spinules and enhancement of the feedback interaction. The strength of the feedback interaction in isolated retinac of the roach was determined as the neutral wavelength at which reversal of spectral response polarity occurred in biphasic HCs. A good correlation was found between the neutral wavelength and the spinule/ribbon ratios of retinae. Biphasic HCs were intracellularly stained with horseradish peroxidase and the correlative ultrastructure of the contacted pedicles was examined. Neutral wavelength was found to be correlated with the spinule number, weighted according to the number of synaptic contacts mediating feed-forward transmission. The latter was estimated from the total number of labelled C_b/H2 HC processes (central and lateral) at synaptic triads. A model in which spinules mediate the negative feedback interaction of HCs in the retina of cyprinid fish is presented.     

The role of visual cues in the facilitation of growth in a schooling fish

Synopsis This study tested the hypothesis that visual contact between fish may result in enhanced rates of growth in a schooling fish. Juvenile chum salmon, Oncorhynchus keta, were held singly and reared in isolation or in visual contact with conspecifics. Fish were fed at either a low (6% body weight d^–1) or high (20% body weight d^–1) ration for 42d. Specific rates of weight gain were 18% greater at low ration and 38% greater at high ration for fish in visual contract with conspecifics than for those held in isolation. The results demonstrate a selective advantage of visual cues associated with schooling behavior and suggest that the efficacy of growth models for schooling fishes may be enhanced by the consideration of social interactions which may facilitate growth.     

A comparison of the benthic macroinvertebrate communities in a trout stream: Winter and spring 1973 and 1977

The benthic macroinvertebrate riffle community of the Bushkill Creek (Northampton County, PA) was sampled monthly, December through May 1972–73 and 1976–77. Total precipitation in 1972–73 was 22.3 cm more than in 1976–77 and water and air temperatures were also higher. In April and May, community composition (dominant taxa and similarity indices) was less similar than in December, January and February. In April and May there were fewer Hydropsyche (Trichoptera) and Ephemerella (Ephmeroptera) and more Chironomidae (Diptera) and Antocha (Diptera) than in 1973. Total numbers and biomass were lower in 1977 than in 1973. The reduction in Hydropsyche, Ephemerella, biomass and total numbers in Spring 1977 may be due to the scouring effect of ice break up. Inspite of fluctuating environmental conditions the macroinvertebrate community exhibited stability.     

Growth,pigments, UV-absorbing compounds and agar yield of the economic red seaweed <Emphasis Type="Italic">Gracilaria lemaneiformis</Emphasis> (Rhodophyta) grown at different depths in the coastal waters of the South China Sea

The economic red alga, Gracilaria lemaneiformis Bory, was grown at different depths in the coastal waters of the South China Sea, and its growth, pigments, ultra-violet (UV)-absorbing compounds and agar yield were investigated in order to see the impacts of depth change. Gracilaria lemaneiformis grew slower at greater depths in March, while the highest relative growth rate (RGR) was found at about 1.0 m depth in April, about 9% higher than that at surface water (0.5 m below the surface). The RGR increased with the increasing daily photosynthetically active radiation (PAR) dose received by the thalli at different depths. The contents of phycoerythrin and chlorophyll a increased, while that of UV-absorbing compounds (UVAC, absorption peak at 325 nm) decreased with increased depth. The highest levels of the UVAC in the thalli grown in surface seawater played a protective role against solar UV radiation (280–400 nm). The content of UVAC declined at deeper depths and under indoor low PAR. The agar yield of the thalli increased with the increasing depths, with the highest content found at 3.5 m depth.     

Aerial visual acuity in harbor seals (<Emphasis Type="Italic">Phoca vitulina</Emphasis>) as a function of luminance

In this study, we measured aerial visual acuity in harbor seals. As a first approach to the hypothesis that harbor seals can obtain acute aerial visual acuity mediated by the interaction of the vertical slit-shaped pupil and the corneal flattening although refractive measurements had revealed aerial myopia, visual acuity was tested as a function of luminance and pupil dilation. We analyzed aerial visual acuity (minimal resolvable stripe width) in three harbor seals in a two-alternative-forced-choice discrimination experiment. Our results further support the hypothesis that harbor seals possess an aerial visual acuity comparable to the acuity in clear waters if the vertical slit pupil does not exceed the zone of corneal flattening in bright light. When the pupil dilates with decreasing luminance, visual acuity decreases which might be due to deflected light from the stronger curved peripheral cornea.     

Changes in mRNA level rhythmicity in the leaves ofSinapis alba during a lengthening of the photoperiod which induces flowering

A previous study has shown that mRNAs exhibit complex patterns of diurnal rhythms in their quantity in the leaves ofSinapis alba during an 8 h light/16 h dark short day (SD). In order to determine whether this situation is rapidly modified in plants subjected to an extended light treatment, we have usedin vitro translation and two-dimensional polyacrylamide gel electrophoresis, together with a strict gel comparison procedure giving aP=0.03 certitude level, to analyse the mRNA complement at different times during a 22 h light/2 h dark long day (LD).During this LD, complex changes affected about 10% of the mRNAs. Thirty-four different patterns were observed. Some diurnal rhythms present in SD are not modified by the lengthening of the light period, but most are affected. Moreover, we have shown that some mRNAs presenting a constant quantity under a SD regime show an increase or a decrease during the first hours of the photoperiod lengthening.InSinapis, this LD also induces flowering. All the changes in mRNA quantity detected thus parallel the photoperiodic induction of flowering in the leaves and are quantitative; no mRNA was shown to appear or to disappear.     

Prey-capture in the African clawed toad (Xenopus laevis): comparison of turning to visual and lateral line stimuli

Separately delivered visual and lateral line stimuli elicit similar but not identical orientation and approach by intact, sighted Xenopus. Response frequencies for visual stimuli declined sharply for distant or caudal stimuli while those for lateral line stimuli changed little. Turn angles correlated highly with stimulus angles but were smaller on average, so regression slopes were less than one. Regression slopes were smaller for visual than for lateral line stimuli, but this apparent difference was due to different distributions of stimulus distance interacting with the toad’s rotation center. Errors in final headings, most often under-rotations, did not differ by modality. Frequencies of lunges and arm capture movements were higher for visual stimuli both overall and especially for rostral proximal stimuli. The results demonstrate accurate orientation by sighted Xenopus to visual and lateral line stimuli; they are consistent with expectations based on in-register tectal maps. Orientation to lateral line stimuli is similar to previous results with blinded animals, revealing no heightened acuity in the latter. Modality differences indicate that the lateral line system is better for omnidirectional orientation and approach to distant stimuli whereas the visual system is more attuned to nearby rostral stimuli and more apt to mediate strikes.Electronic Supplementary Material Supplementary material is available to authorised users in the online version of this article at .     

Cycling of soil carbon in a Japanese red pine forest II. Changes occurring in the first year after a clear-felling

Cycling of soil carbon in the first year after a clear-felling was compared with that before the felling in a Japanese red pine forest in Hiroshima Prefecture, west Japan. The daily mean temperature at the soil surface in summer was increased after the felling in comparison to that before felling, and the water content of both the A₀ layer and the surface mineral soil was decreased due to the loss of the forest canopy. The rate of weight loss of the A₀ layer was reduced after felling. However, accumulation of the A₀ layer rapidly decreased because of the lack of litter supply to the forest floor. Low soil respiration after felling was mainly caused by the cessation of root respiration. Analysis of annual soil carbon cycling was then conducted using a compartment model. The relative decomposition rate of the A₀ layer decreased whereas that of humus and dead roots in mineral soil increased to some extent after felling. The accumulation of carbon in mineral soil, however, increased slightly due to the supply of humus from roots killed by the felling.     

Pelagic-benthic transition of the harmful alga, Heterosigma akashiwo: Changes in swimming and implications for benthic cell distributions

Many harmful algal blooming (HAB) species transition between a vegetative, motile phase in the water column and a dormant, non-motile resting phase in the sediments. These life history transitions potentially regulate the timing, location and persistence of bloom events. Motility promotes aggregation and influences vertical distributions in the water column. However, the contribution of this behavior to benthic distributions of resting cells is currently unknown. We used video-tracking techniques to test the hypothesis that algal cells use active down-swimming during pelagic-benthic transition to favorably influence benthic distributions. In an experimental water column, we monitored cell swimming trajectories of Heterosigma akashiwo for 14 days after cells were signaled to enter the benthic resting stage. Using the statistical characteristics of individual cell trajectories, we developed a video-based motion assay to assign each tracked Heterosigma cell to one of three cell states known to occur during pelagic-benthic transition: induced motile, transitional and resting. The primary swimming characteristic influencing benthic distribution, net vertical velocity, was essentially the same for all three cell states. Hence, we found no evidence that active down-swimming influences benthic distributions. Our data suggest that benthic distributions of Heterosigma resting cells are similar to distributions of slowly sedimenting passive particles. These observations suggest that Heterosigma benthic resting cell distributions can be predicted by modeling the effects of cell sedimentation rates combined with geophysical flow patterns.