Retinal photoreceptors and visual pigments in Boa constrictor imperator

The photoreceptors of Boa constrictor, a boid snake of the subfamily Boinae, were examined with scanning electron microscopy and microspectrophotometry. The retina of B. constrictor is duplex but highly dominated by rods, cones comprising 11% of the photoreceptor population. The rather tightly packed rods have relatively long outer segments with proximal ends that are somewhat tapered. There are two morphologically distinct, single cones. The most common cone by far has a large inner segment and a relatively stout outer segment. The second cone, seen only infrequently, has a substantially smaller inner segment and a finer outer segment. The visual pigments of B. constrictor are virtually identical to those of the pythonine boid, Python regius. Three different visual pigments are present, all based on vitamin A(1.) The visual pigment of the rods has a wavelength of peak absorbance (lambda(max)) at 495 +/- 2 nm. The visual pigment of the more common, large cone has a lambda(max) at 549 +/- 1 nm. The small, rare cone contains a visual pigment with lambda(max) at 357 +/- 2 nm, providing the snake with sensitivity in the ultraviolet. We suggest that B. constrictor might employ UV sensitivity to locate conspecifics and/or to improve hunting efficiency. The data indicate that wavelength discrimination above 430 nm would not be possible without some input from the rods.     

A gene-derived SNP-based high resolution linkage map of carrot including the location of QTL conditioning root and leaf anthocyanin pigmentation

Background

Purple carrots accumulate large quantities of anthocyanins in their roots and leaves. These flavonoid pigments possess antioxidant activity and are implicated in providing health benefits. Informative, saturated linkage maps associated with well characterized populations segregating for anthocyanin pigmentation have not been developed. To investigate the genetic architecture conditioning anthocyanin pigmentation we scored root color visually, quantified root anthocyanin pigments by high performance liquid chromatography in segregating F₂, F₃ and F₄ generations of a mapping population, mapped quantitative trait loci (QTL) onto a dense gene-derived single nucleotide polymorphism (SNP)-based linkage map, and performed comparative trait mapping with two unrelated populations.

Results

Root pigmentation, scored visually as presence or absence of purple coloration, segregated in a pattern consistent with a two gene model in an F₂, and progeny testing of F₃-F₄ families confirmed the proposed genetic model. Purple petiole pigmentation was conditioned by a single dominant gene that co-segregates with one of the genes conditioning root pigmentation. Root total pigment estimate (RTPE) was scored as the percentage of the root with purple color.All five anthocyanin glycosides previously reported in carrot, as well as RTPE, varied quantitatively in the F₂ population. For the purpose of QTL analysis, a high resolution gene-derived SNP-based linkage map of carrot was constructed with 894 markers covering 635.1 cM with a 1.3 cM map resolution. A total of 15 significant QTL for all anthocyanin pigments and for RTPE mapped to six chromosomes. Eight QTL with the largest phenotypic effects mapped to two regions of chromosome 3 with co-localized QTL for several anthocyanin glycosides and for RTPE. A single dominant gene conditioning anthocyanin acylation was identified and mapped.Comparative mapping with two other carrot populations segregating for purple color indicated that carrot anthocyanin pigmentation is controlled by at least three genes, in contrast to monogenic control reported previously.

Conclusions

This study generated the first high resolution gene-derived SNP-based linkage map in the Apiaceae. Two regions of chromosome 3 with co-localized QTL for all anthocyanin pigments and for RTPE, largely condition anthocyanin accumulation in carrot roots and leaves. Loci controlling root and petiole anthocyanin pigmentation differ across diverse carrot genetic backgrounds.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-1118) contains supplementary material, which is available to authorized users.     

Season-, sex-, and age-specific accumulation of plasma carotenoid pigments in free-ranging white-winged crossbills Loxia leucoptera

Many birds acquire carotenoid pigments from foods and deposit these pigments into feathers and bare‐parts to become sexually attractive, but little work has been done on the interindividual and temporal variability in the types and amounts of carotenoids that free‐ranging individuals have available for use in coloration or other functions (e.g., in immunomodulation). To address this issue, we studied intra‐annual variation in plasma carotenoid profiles of juvenile and adult white‐winged crossbills Loxia leucoptera of both sexes. Adult male crossbills exhibit bright red carotenoid‐based plumage pigmentation, whereas females uniformly display drab yellow feather coloration and juvenile males only occasionally display some orange or pink color. Yellow xanthophylls (e.g., lutein, zeaxanthin) were predominant in plasma of birds from both sexes and age classes throughout the year. Plasma xanthophylls levels tended to be highest in the summer, when crossbills increase seed consumption for breeding as well as supplement their diet with insects. Blood accumulation of three other, less common plasma carotenoids‐β‐cryptoxanthin, rubixanthin, and gazaniaxanthin‐varied in a highly season‐, sex‐, and age‐dependent fashion. These carotenoids were virtually absent in juvenile or adult female plasma at all times of year and were only present in male plasma, at higher concentrations in adults than juveniles, during the period of feather growth (Sept.–Nov.). These pigments have been reported as valuable precursors of the metabolically derived red pigments (e.g., 3‐hydroxy‐echinenone, 4‐oxo‐rubixanthin, and 4‐oxo‐gazaniaxanthin, respectively) that appear in the plumage of male crossbills. These findings suggest that male crossbills either adopt a season‐specific foraging strategy to acquire foods rich in these pigments at the time they are needed to develop red coloration, or have a unique physiological ability to metabolically produce these pigments or absorb them from food during molt, in order to maximize color production.     

Intraclutch variation in avian eggshell pigmentation: the anaemia hypothesis

Many passerine species lay eggs that are speckled with dark protoporphyrin pigmentation. Because protoporphyrin is mainly derived from the blood, we here formulate and test a new hypothesis that links an increase in anaemia along the laying sequence to within-clutch variation in egg pigmentation. More intense pigmentation is expected if pigments accumulate during enhanced red blood cell production in response to anaemia. Reduced pigmentation is expected if pigments are derived from the degradation of red blood cells that circulate in smaller numbers due to blood loss. To test this hypothesis, we manipulated anaemia in great tit (Parus major) females by infesting the nests with hen fleas (Ceratophyllus gallinae) prior to egg laying. Polychromatophil (i.e., immature red blood cells) percentage, as a measure of blood cell production, was positively correlated with parasite load confirming that female great tits experienced stronger anaemia when infested with haematophagous parasites during egg laying. We found a positive relationship between spot darkness and laying order that weakened under high parasite load. This result suggests that anaemia in females due to blood-sucking parasites led to diminished protoporphyrin from disintegrated red blood cells and hence a decreased deposition of protoporphyrin. However, the overall increase in pigment darkness along the laying sequence suggests that pigments also accumulate by enhanced red blood cell production caused by anaemia due to egg production itself.     

The evolution of sperm ultrastructure among Boidae (Serpentes)

We investigate the evolution of sperm ultrastructure of three species of Boidae (Epicrates cenchria, Boa constrictor amarali, and Corallus hortulanus). Spermatozoa of these species are filiform consisting of a head region, containing the nucleus and acrosome complex, a midpiece, and a tail region subdivided into principal piece and endpiece. Multilaminar membranes and extracellular microtubules were observed next to the plasma membrane of the spermatozoa. The following differences were observed among the species: ridge on acrosome surface in Boa constrictor amarali (absent in Epicrates cenchria and Corallus hortulanus), stopper-like perforatorium base plate in Boa constrictor amarali and Epicrates cenchria (absent in Corallus hortulanus), rounded mitochondria in transverse section in Epicrates cenchria and Corallus hortulanus (irregular in Boa constrictor amarali). We mapped sperm characters onto two phylogenies based on morphological (Kluge in Misc Publ Mus Zool Univ Michigan 178:1–58, 1991) and molecular (Austin in Copeia 2:341–352, 2000) data, using a number of squamate species as outgroups. We identified 31 unambiguous character transformations in the morphological phylogeny and 30 in the molecular phylogeny, but only 13 and 12 transformations, respectively, are possible synapomorphies. We identified novel sperm synapomorphies, which were common between the morphological and molecular phylogenies: absence of perforatorium base plate and mitochondria arranged as sinuous tubes in oblique section (Serpentes), acrosome vesicle not subdivided and fibers 3 and 8 at the anteriormost region of principal piece (Boidae), and absence of an electron dense structure inside the proximal centriole (Elapidae + Colubridae). Our results suggest greater agreement between sperm ultrastructure and gross anatomical characters. In addition, we found no tendency for more homoplasies in the sperm head than in the flagellum, as recorded in previous studies.     

Transcriptomic analysis of skin pigmentation variation in the Virginia opossum (Didelphis virginiana)

Skin pigmentation and coat pigmentation are two of the best‐studied examples of traits under natural selection given their quantifiable fitness interactions with the environment (e.g., camouflage) and signalling with other organisms (e.g., warning coloration). Previous morphological studies have found that skin pigmentation variation in the Virginia opossum (Didelphis virginiana) is associated with variation in precipitation and temperatures across its distribution range following Gloger's rule (lighter pigmentation in temperate environments). To investigate the molecular mechanism associated with skin pigmentation variation, we used RNA‐Seq and quantified gene expression of wild opossums from tropical and temperate populations. Using differential expression analysis and a co‐expression network approach, we found that expression variation in genes with melanocytic and immune functions is significantly associated with the degree of skin pigmentation variation and may be underlying this phenotypic difference. We also found evidence suggesting that the Wnt/β‐catenin signalling pathway might be regulating the depigmentation observed in temperate populations. Based on our study results, we present several alternative hypotheses that may explain Gloger's rule pattern of skin pigmentation variation in opossum, including changes in pathogen diversity supporting a pathogen‐resistant hypothesis, thermal stress associated with temperate environments, and pleiotropic and epistatic interactions between melanocytic and immune genes.     

Plasmid-Mediated Sulfanilamide Resistance

Dihydropteroate synthetase (DHPS) is specified by a substrain of Escherichia coli K12, ML1410. This enzyme activity is inhibited by sulfanilamides (Sa) and is known to be heat-stable, i.e., an Sa-sensitive normal enzyme. Another DHPS activity specified by E. coli ML1410 carrying drug resistance plasmids is Sa-resistant but heat-sensitive, i.e., an Sa-resistant enzyme. Most plasmids encoding single Sa or double (Sa. Tc or Sa. Sm) (Tc, tetracycline; Sm, streptomycin) resistance mediate the formation of this type of DHPS. Therefore, E. coli carrying these plasmids becomes diploid for DHPS, i.e., an Sa-resistant and an Sa-sensitive normal enzyme. The biochemical mechanism of Sa resistance mediated by plasmids encoding triple (Cm.Sm.Sa; Tc.Sm.Sa) and quadruple (Cm.Tc.Sm.Sa) resistance is not due to the formation of an altered DHPS but probably due to the decrease in permeation of the drug into the cell. The evolutionary process of the formation of Sa-resistance determinants on plasmids is discussed based on the presence of two types of Sa resistance mechanism.     

Establishment of the site of involution at novel locations on the amphibian embryo

Anuran (Rana) and urodele (Ambystoma) amphibian eggs were subjected to prolonged unnatural orientations in relation to gravity. In some cases eggs were rotated 90°, while in other instances eggs were rotated 180° (complete inversion). Alterations in the pigmentation pattern, cleavage pattern, and site of involution were observed. Despite these unnatural orientations to gravity, the morphogenesis of axial structures was frequently normal. Reorganization of the egg cytoplasm apparently takes place after the unnatural orientation. Rather than being localized in a fixed position in the egg (e.g., the egg cortex), the determinants for the pattern of early embryogenesis are probably located in that portion of the cytoplasm (e.g., “internal” cytoplasm) that orients to gravity.     

Novel Hepatozoon in vertebrates from the southern United States

Novel Hepatozoon spp. sequences collected from previously unrecognized vertebrate hosts in North America were compared with documented Hepatozoon 18S rRNA sequences in an effort to examine phylogenetic relationships between the different Hepatozoon organisms found cycling in nature. An approximately 500-base pair fragment of 18S rDNA common to Hepatozoon spp. and some other apicomplexans was amplified and sequenced from the tissues or blood of 16 vertebrate host species from the southern United States, including 1 opossum (Didelphis virginiana), 2 bobcats (Lynx rufus), 1 domestic cat (Felis catus), 3 coyotes (Canis latrans), 1 gray fox (Urocyon cinereoargenteus), 4 raccoons (Procyon lotor), 1 pet boa constrictor (Boa constrictor imperator), 1 swamp rabbit (Sylvilagus aquaticus), 1 cottontail rabbit (Sylvilagus floridanus), 4 woodrats (Neotoma fuscipes and Neotoma micropus), 3 white-footed mice (Peromyscus leucopus), 8 cotton rats (Sigmodon hispidus), 1 cotton mouse (Peromyscus gossypinus), 1 eastern grey squirrel (Sciurus carolinensis), and 1 woodchuck (Marmota monax). Phylogenetic analyses and comparison with sequences in the existing database revealed distinct groups of Hepatozoon spp., with clusters formed by sequences obtained from scavengers and carnivores (opossum, raccoons, canids, and felids) and those obtained from rodents. Surprisingly, Hepatozoon spp. sequences from wild rabbits were most closely related to sequences obtained from carnivores (97.2% identical), and the sequence from the boa constrictor was most closely related to the rodent cluster (97.4% identical). These data are consistent with recent work identifying prey-predator transmission cycles in Hepatozoon spp. and suggest this pattern may be more common than previously recognized.     

Red gall pigmentation: cytokinin stimulation is not everything

Recently, the nature of gall pigmentation phenomenon has gained interest, with different, and often contradicting, explanations and hypotheses. A recent, welcome contribution by Connor et al. (Arthropod–Plant Interact 6:489–495, 2012) suggested that gall pigmentation is a mere “fabricational noise” of the gall development, caused by the production of anthocyanin due to the accumulation of cytokinins and sugars. We propose that this perspective, although probably true in some systems, is an oversimplification of a more complex situation. We argue that since multiple pigments are likely to be involved in gall coloration, and since the link between cytokinins and pigmentation is not obligatory, this is an unlikely general explanation of gall pigmentation. The galling habit has evolved independently among numerous insect lineages and habitats, and therefore, the role of gall pigmentation may vary. It is the time to test the different hypotheses in the field.     

Effect of light on nonphotosynthetic microorganisms. II. Photochromogenicity in genus Streptomyces.

The effect of light on the pigmentation of various strains belonging to the genus Streptomyces was investigated. It was revealed that six species of streptomycetes, S. massaporeus, S. phaeopurpureus, S. chibaensis, S. salmonicida, S. fluvissimus and S. longispororuber, were photochromogenic, i.e., these strains can be photoinduced to synthesize pigments. On the basis of these results, pigmentation in Streptomyces is discussed.     

Inferring the phylogenetic position of Boa constrictor among the Boinae

Snakes of the subfamily Boinae are found in Madagascar, the Papuan-Pacific Islands, and the Neotropics. It has been suggested that genera within each of these particular areas do not form monophyletic groups. Further, it was proposed that the New World Boa constrictor is more closely related to boine genera in Madagascar than to boines in the Neotropics. Along with inferring the relationship of all boine genera using data from the cytochrome b gene and morphology, the placement of Boa was also examined. Phylogenetic inferences using maximum likelihood and Bayesian (BI) methods for combined data analyses and separate analyses of DNA sequence and morphological data were conducted. Priors, parametric bootstraps, and the Shimodaira-Hasegawa test were used to examine the previously proposed placement of Boa with Madagascan taxa using these DNA data. DNA data and combined data analyses strongly reject the hypothesis that Boa is more closely related to Old World genera than to other New World genera. Additionally, strong tree support suggests that all species within Madagascar, the Papuan-Pacific Islands, and the Neotropics each form a monophyletic group with respect to their geographic region.     

Antisense inhibition of flavonoid biosynthesis in petunia anthers results in male sterility.

Inhibition of flower pigmentation in transgenic petunia plants was previously accomplished by expressing an antisense chalcone synthase (chs) gene under the control of the cauliflower mosaic virus (CaMV) 35S promoter. This chimeric gene was not effective in inhibiting pigmentation in anthers, presumably because the viral CaMV 35S promoter was insufficiently expressed in cell types of this organ in which the pigments are produced. Insertion of the anther box, a homologous sequence found in other genes expressed in anthers, resulted in a modified expression pattern driven by this promoter, as monitored by the beta-glucuronidase (gus) gene. In addition to the basic CaMV 35S expression pattern in anthers, GUS activity was observed in tapetum cells when the modified promoter was fused to the gus gene. This promoter construct was subsequently used to drive an antisense chs gene in transgenic petunia, which led to the inhibition of pigment synthesis in anthers of five of 35 transformants. Transgenic plants with white anthers were male sterile due to an arrest in male gametophyte development. This finding indicated that flavonoids play an essential role in male gametophyte development.     

Allopurinol-induced melanism in the tiger salamander (Ambystoma tigrinum nebulosum).

The enzyme, xanthine dehydrogenase (XDH), has been examined in Ambystoma tigrinum nebulosum with respect to its role in pigmentation. It now seems probable that the melanoid gene (m) either codes directly for XDH or is somehow intimately connected with the normal function of this enzyme. Inhibition of XDH using the drug, allopurinol, results in animals which appear to be phenocopies of melanoid mutants as described for the Mexican axolotl (Ambystoma mexicanum). The effects of allopurinol in terms of specific pigmentary alterations were examined, and a new method for analyzing heterogeneous extracts of skin pigments (e.g., purines and pteridines) is presented. The significance of the link between XDH and melanism is discussed with emphasis on possible mechanisms of pigment induction and general applicability to biological systems.     

The influence of carotenoid acquisition and utilization on the maintenance of species-typical plumage pigmentation in male American goldfinches (Carduelis tristis) and northern cardinals (Cardinalis cardinalis).

Birds display a tremendous variety of carotenoid-based colors in their plumage, but the mechanisms underlying interspecific variability in carotenoid pigmentation remain poorly understood. Because vertebrates cannot synthesize carotenoids de novo, access to pigments in the diet is one proximate factor that may shape species differences in carotenoid-based plumage coloration. However, some birds metabolize ingested carotenoids and deposit pigments that differ in color from their dietary precursors, indicating that metabolic capabilities may also contribute to the diversity of plumage colors we see in nature. In this study, we investigated how the acquisition and utilization of carotenoids influence the maintenance of species-typical plumage pigmentation in male American goldfinches (Carduelis tristis) and northern cardinals (Cardinalis cardinalis). We supplemented the diet of captive goldfinches with red carotenoids to determine whether males, which are typically yellow in color, were capable of growing red plumage. We also deprived cardinals of red dietary pigments to determine whether they could manufacture red carotenoids from yellow precursors to grow species-typical red plumage. We found that American goldfinches were able to deposit novel pigments in their plumage and develop a striking orange appearance. Thus, dietary access to pigments plays a role in determining the degree to which goldfinches express carotenoid-based plumage coloration. We also found that northern cardinals grew pale red feathers in the absence of red dietary pigments, indicating that their ability to metabolize yellow carotenoids in the diet contributes to the bright red plumage that they display.     

Why are birds’ eggs speckled?

Birds are unique in laying eggs with pigmented shells, but for most species (e.g. most passerines, which lay white eggs speckled with reddish spots of protoporphyrin) the pigments’ function is unknown. We studied a bird population at a geologically variable site, and considered a hitherto untested hypothesis: that protoporphyrin pigments might compensate for reduced eggshell‐thickness (caused partly by calcium deficiency), which is known to reduce eggshell‐strength and increase eggshell‐permeability. We found that pigment spots specifically demarcated thinner areas of shell, with darker spots marking yet thinner shell than paler spots. Variation in pigmentation was thus associated with variation in shell thickness both within and between clutches, so accounting for the eggshell's characteristic spot patterns. Geological variability at this site has resulted in a great range of calcium availability and, as predicted by the hypothesis, variation in calcium availability was found to affect between‐clutch variation in both eggshell‐mass (+) and pigmentation characteristics (?). We suggest a physiological mechanism and some important implications of these findings.     

Ultraviolet vision in birds: the importance of transparent eye media

Ultraviolet (UV)-sensitive visual pigments are widespread in the animal kingdom but many animals, for example primates, block UV light from reaching their retina by pigmented lenses. Birds have UV-sensitive (UVS) visual pigments with sensitivity maxima around 360–373 nm (UVS) or 402–426 nm (violet-sensitive, VS). We describe how these pigments are matched by the ocular media transmittance in 38 bird species. Birds with UVS pigments have ocular media that transmit more UV light (wavelength of 50% transmittance, λ_T0.5, 323 nm) than birds with VS pigments (λ_T0.5, 358 nm). Yet, visual models predict that colour discrimination in bright light is mostly dependent on the visual pigment (UVS or VS) and little on the ocular media. We hypothesize that the precise spectral tuning of the ocular media is mostly relevant for detecting weak UV signals, e.g. in dim hollow-nests of passerines and parrots. The correlation between eye size and UV transparency of the ocular media suggests little or no lens pigmentation. Therefore, only small birds gain the full advantage from shifting pigment sensitivity from VS to UVS. On the other hand, some birds with VS pigments have unexpectedly low UV transmission of the ocular media, probably because of UV blocking lens pigmentation.     

SINGLE-CELL PIGMENTATION OF PORPHYRA LINEARIS ANALYZED BY FOURIER TRANSFORM MULTI-PIXEL SPECTROSCOPY AND IMAGE ANALYSIS1

The novel method of Fourier transform multi-pixel spectroscopy was used for the nondestructive analysis of and comparison of pigmentation in different regions of live thalli of the red alga Porphyra linearis. Because the thallus in this alga consists of a monolayer of nonoverlapping cells, we were able to analyze the pigmentation of single cells by combining light absorbance with natural fluorescence data. From the image of each cell in the vegetative male and female reproductive and holdfast regions, more than 4 ± 10⁴ fluorescence and absorbance spectra were obtained. Specific pigments in the different regions were localized by the use of a software program of similarity mapping followed by image construction. The reconstructed images revealed subcellular localization of each pigment according to specific spectroscopic fingerprints. The results showed that the vegetative and female reproductive cell types had a significantly higher content of phycoerythrin than of phycocyanin, and quite similar chlorophyll a levels. Most of the holdfast cells were poorly pigmented, but had more chlorophyll a than phycoerythrin or phycocyanin. The male reproductive cells contained only traces of pigments. Thus, by using Fourier transform multipixel spectroscopy, we were able to characterize the pigmentation of different regions of the thallus and follow the distribution patterns of the different pigments on the subcellular level along the differentiation gradient of the alga.     

Effect of Light on Nonphotosynthetic Microorganisms

The effect of light on the pigmentation of various strains belonging to the genus Streptomyces was investigated. It was revealed that six species of streptomycetes, S. massasporeus, S. phaeopurpureus, S. chibaensis, S. salmonicida, S. fluvissimus and S. longispororuber, were photochromogenic, i.e., these strains can be photoinduced to synthesize pigments. On the basis of these results, pigmentation in Streptomyces is discussed.     

碳排放影响下中国省域旅游效率损失度研究

旅游效率损失度反映了碳排放对旅游效率的影响程度。采用超越对数生产函数测算2001—2014年中国30个省(区、市)的旅游效率及损失度,并运用面板回归模型分析效率损失的驱动力。结果表明:(1)碳排放对中国各省(区、市),尤其是中部省份的旅游效率造成了损失。研究期内,中国总体旅游效率损失度呈现上升趋势,东部地区年均增幅最大;(2)中国旅游效率与损失度总体上处于中等水平,但损失度年均增长率远高于旅游效率增长率,中部地区因为排放问题造成了较大的效率损失;(3)根据不同省域旅游效率及其损失度,可划分为"高效低损、高效高损、低效低损、低效高损"4种类型区;(4)基础设施、旅游接待能力、旅游吸引力、旅游产业规模、旅游产业结构、能源技术对不同类型区的影响存在差异,应根据外力驱动大小和作用方向调整旅游效率优化策略。