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A structural colour ornament correlates positively with parasite load and body condition in an insular lizard species

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Pigment-based ornaments in vertebrates may reflect the body condition or health status of the individual in correlation with environmental stress and hormonal balance. Among the environmental factors shaping sexual colouration, parasitic infections have been stressed as an important evolutionary pressure constraining the maintenance of pigment-based ornaments. However, the honesty of structure-based ornaments in vertebrates is still under debate. Structural UV-biased ornaments in Gallotia lizards were described as a trait used by conspecifics during mate and rival assessment suggesting the reliability of these signals. We investigated the relationship between parasitaemia, body condition and a structural-based ornament present in the cheek of the sexually dichromatic Canarian lacertid Gallotia galloti in a population with an almost 100 % prevalence of haemoparasites. Using spectrophotometric techniques, we found that males with higher values of cheek UV chroma were infected with more haemoparasites. No significant relationship was found between haemoparasite load and body condition. However, males with higher cheek UV chroma showed significantly better body condition. In addition, we found that cheek hue was significantly related to body condition of individuals in both sexes. In males, cheek reflectivity biased towards the UV range was significantly related to better body condition. In females, those individuals with better body condition showed more whitish cheeks with less UV suggesting that cheek hue serves as an intersexual signal for sex recognition. We conclude that the positive relationship between cheek chroma and parasite load in male lizards is compatible with both differential density of melanin and iridophore arrangement in the dermis conveying an individual’s ability to cope with environmental stress.
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A structural colour ornament correlates positively with parasite
load and body condition in an insular lizard species
Rodrigo Megía-Palma
&Javier Martínez
&Santiago Merino
Received: 28 November 2015 /Revised: 22 May 2016 /Accepted: 26 May 2016/Published online: 4 June 2016
#Springer-Verlag Berlin Heidelberg 2016
Abstract Pigment-based ornaments in vertebrates may re-
flect the body condition or health status of the individual in
correlation with environmental stress and hormonal balance.
Among the environmental factors shaping sexual colouration,
parasitic infections have been stressed as an important evolu-
tionary pressure constraining the maintenance of pigment-
based ornaments. However, the honesty of structure-based
ornaments in vertebrates is still under debate. Structural UV-
biased ornaments in Gallotia lizards were described as a trait
used by conspecifics during mate and rival assessment sug-
gesting the reliability of these signals. We investigated the
relationship between parasitaemia, body condition and a
structural-based ornament present in the cheek of the sexually
dichromatic Canarian lacertid Gallotia galloti in a population
with an almost 100 % prevalence of haemoparasites. Using
spectrophotometric techniques, we found that males with
higher values of cheek UV chroma were infected with more
haemoparasites. No significant relationship was found be-
tween haemoparasite load and body condition. However,
males with higher cheek UV chroma showed significantly
better body condition. In addition, we found that cheek hue
was significantly related to body condition of individuals in
both sexes. In males, cheek reflectivity biased towards the UV
range was significantly related to better body condition. In
females, those individuals with better body condition showed
more whitish cheeks with less UV suggesting that cheek hue
serves as an intersexual signal for sex recognition. We con-
clude that the positive relationship between cheek chroma and
parasite load in male lizards is compatible with both differen-
tial density of melanin and iridophore arrangement in the der-
mis conveying an individuals ability to cope with environ-
mental stress.
Keywords Colour .Gallotia .Hamilton and Zuk hypothesis .
Handicap Principle .Island ecology .Parasite .Sexual
The Handicap Principle (Zahavi 1975) proposed a theoretical
framework to explain the persistence of conspicuous orna-
ments in nature. Individuals are tested by the handicap that
implies bearing a conspicuous, or even exaggerated, trait or
behaviour (Zahavi 1975). An exaggeration of these characters
without a correlation to an adaptive advantage should lose its
effect by negative selection (Zahavi 1975;Grafen1990). In
several vertebrates including lizards, colour ornaments have
been studied as signals of individual quality used by conspe-
cifics during rival or mate assessment (Cooper and Burns
1987; Stapley and Whiting 2006; Martín and López 2009;
Bajer et al. 2010,2011). Parasites exert a selective environ-
mental pressure shaping sexual ornaments (Hamilton and Zuk
2013). The hypothesis formulated by Hamilton and Zuk
(1982) assumes that: (1) females choose mates on the basis
of secondary sex characters, (2) the full expression of these
characters is limited by parasite infection, (3) females choose
males with exaggerated secondary traits to obtain resistance
Communicated by: Sven Thatje
*Rodrigo Megía-Palma
Departamento de Ecología Evolutiva, Museo Nacional de Ciencias
Naturales-CSIC, J. Gutiérrez Abascal 2, E-28006 Madrid, Spain
Área Parasitología. Departamento de Biomedicina y
Biotecnología.Facultad de Farmacia, Universidad de Alcalá de
Henares, Alcalá de Henares, E-28871 Madrid, Spain
Sci Nat (2016) 103: 52
DOI 10.1007/s00114-016-1378-8
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
... nm (Pérez i deLanuza and Font 2010;Megía-Palma et al. 2016a, 2016b. In contrast, the available spectral evidence of the blue coloration in species of the genus Sceloporus (fam. ...
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Male competition conforms to a cost-benefit model, because while aggression may increase reproductive prospects, it can also increase risk of injury. We hypothesize that an additional cost in aggressive males would be an increase of parasite load associated with a high energy investment into sexual competition. Some of these infections, in turn, may downmodulate the level of host aggression via energetic trade-offs. We staged dyadic male contests in the lab to investigate the relationships of multiple parasites with the agonistic behavior of lizard hosts, Sceloporus occidentalis. We also included both color and behavioral traits from opponents in the analyses because (i) color patches of lizards may serve as intraspecific signals used by conspecifics to assess the quality of opponents, and (ii) contests between male lizards fit classical models of escalated aggression, where lizards increase aggression displays in response to an opponent’s behavior. The results conform to our hypothesis because male lizards displayed more pushups when they had more ticks. Moreover, some parasites may modulate the levels of aggression because lizards infected by hematic coccidians performed fewer pushups. Interestingly, lizards also displayed fewer pushups when both chroma and size of the opponent’s blue patch were greater. The results thus also supported the role of the blue patch of S. occidentalis as a sexual armament, because it contributed to the deterrence of aggression from opponent lizards. We revealed that natural parasitic infections in lizard hosts can contribute to their agonistic behavior. We encourage future studies to account for parasites in behavioral tests with lizards.
... Conspicuous colourful patches -displayed mainly by males -would rather allow to attract mates or to bully potential competitors (Andersson 1994). Hence, colourful ornaments are thought to function as signals of quality to reliably inform conspecifics about, for example, condition (Hill 2011), immune status (Rodríguez-Ruiz et al. 2020) or parasitic burden (Megía-Palma et al. 2016). Honesty in signalling traits is achieved through associated costs to produce and maintain them (Andersson 1994). ...
In many species, offspring display conspicuous adult-like colouration already early in life, even though they might be very vulnerable to predation at this stage. Yet, the signalling function of adult-like traits in nestlings has been little explored to date. Here, we investigated whether the yellow breast plumage of blue tit (Cyanistes caeruleus) nestlings shows patterns of condition-dependence and hence signals individual quality, as has been described for adult birds. During three consecutive breeding seasons, we therefore explored the association between nestling body mass and three colour components of the yellow breast plumage (i.e., UV chroma, carotenoid chroma and total brightness), considering both within and among nest effects. Carotenoid chroma was not affected by body mass. However, UV chroma and total brightness showed an among-nest effect of body mass, suggesting that they might signal aspects of genetic quality or parental rearing capacity. Interestingly, we also found a within-nest effect of body mass on total brightness, suggesting that this is a good candidate for a condition-dependent signal within the family. Thus, other family members could rely on brightness to adjust their behavioural strategies, such as feeding behaviour in parents. Our study thus reveals that certain colour components of the yellow breast plumage signal different aspects of offspring quality and suggest that they might have a correlated signalling value across life-history stages.
... For instance, from a female point of view, highly infested males might be better able to cope with infections and demonstrate improved parasite tolerance as they were able to develop similar or better secondary sexual ornaments than their competitors. In line with this, Ressel and Schall (1989) and Megía-Palma et al. (2016) found a positive correlation between color, ornament size, and parasite load in lizard species. Producing and maintaining such ornaments while bearing parasites may be physiologically costly and only high-quality individuals will be able to afford it (Folstad and Karter 1992;McGraw and Hill 2000). ...
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Parasites are known to be a key driving force in mate choice and are important for the expression and evolution of ornaments and behavioural traits being used. However, there is little experimental evidence on how parasite’s burden of the choosing individual is integrated in the mate-choice process and how it affects decision-making, especially in relation to parasite infestation of potential mates. Thus, the aim of our study was to determine whether female house sparrows, Passer domesticus, adjust their mate preference according to their own as well as the parasite load of prospective partners. To do this, we experimentally manipulated female parasite load and determined their mate preferences prior to and after parasite treatment. We manipulated the chronic coccidian parasite burden of females either by initiating the acute infection phase via re-infecting them with coccidian or by temporally reducing parasite load of coccidia. We then measured the effect of this manipulation on mate preference by presenting females with a choice of four stimuli: three males with similar ornaments, but unmanipulated, naturally varying chronic coccidiosis levels, and an unmanipulated control female. Additionally, we recorded some male’s behaviour in relation to their infection status pointing towards an increased or reduced interest in mating. We found that females preferred highly infested males prior to manipulation, regardless of their own infestation level. However, after manipulation, infested females avoided highly infested males probably in response to the deterioration of their health condition by parasites. Our study suggests that mate choice decisions are more complex when they are mediated by parasites. The implications of parasites for evolutionary theories of sexual signalling and mate choice are discussed.
... In contrast, parasite load was uncorrelated with UV colouration, diverging from previous results showing either positive or negative correlations between parasite load and UV signals in other lacertid species (e.g. -Palma et al., 2016a-Palma et al., , 2016b. ...
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Male lizards often display multiple pigment‐based and structural colour signals which may reflect various quality traits (e.g. performance, parasitism), with testosterone (T) often mediating these relationships. Furthermore, environmental conditions can explain colour signal variation by affecting processes such as signal efficacy, thermoregulation, and camouflage. The relationships between colour signals, male quality traits, and environmental factors have often been analysed in isolation, but simultaneous analyses are rare. Thus, the response of multiple colour signals to variation in all these factors in an integrative analysis remains to be investigated. Here, we investigated how multiple colour signals relate to their information content, examined the role of T as a potential mediator of these relationships, and how environmental factors explain colour signal variation. We performed an integrative study to examine the covariation between three colour signals (melanin‐based black, carotenoid‐based yellow‐orange, and structural UV), physiological performance, parasitism, T levels, and environmental factors (microclimate, forest cover) in male common lizards (Zootoca vivipara) from 13 populations. We found that the three colour signals conveyed information on different aspects of male condition, supporting a multiple message hypothesis. T influenced only parasitism, suggesting that T does not directly mediate the relationships between colour signals and their information content. Moreover, colour signals became more saturated in forested habitats, suggesting an adaptation to degraded light conditions, and became generally brighter in mesic conditions, in contradiction with the thermal melanism hypothesis. We show that distinct individual quality traits and environmental factors simultaneously explain variations of multiple colour signals with different production modes. Our study therefore highlights the complexity of colour signal evolution, involving various sets of selective pressures acting at the same time, but in different ways depending on colour production mechanism.
... While considerable effort has been spent on understanding the physical mechanisms responsible for structural coloration [12,13], less attention has been paid to the biochemical pathways involved in the development of such structures [14][15][16]. In this context, the regulatory pathways linking environmental conditions to the development of photonic structures should provide important insights into the biological function of structural colour in nature [17,18]. For example, environmental factors such as temperature and nutrient availability could be used in honesty signalling towards other organisms [17,[19][20][21][22][23]. ...
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The brightest colours in nature often originate from the interaction of light with materials structured at the nanoscale. Different organisms produce such coloration with a wide variety of materials and architectures. In the case of bacterial colonies, structural colours stem for the periodic organization of the cells within the colony, and while considerable efforts have been spent on elucidating the mechanisms responsible for such coloration, the biochemical processes determining the development of this effect have not been explored. Here, we study the influence of nutrients on the organization of cells from the structurally coloured bacteria Flavobacterium strain IR1. By analysing the optical properties of the colonies grown with and without specific polysaccharides, we found that the highly ordered organization of the cells can be altered by the presence of fucoidans. Additionally, by comparing the organization of the wild-type strain with mutants grown in different nutrient conditions, we deduced that this regulation of cell ordering is linked to a specific region of the IR1 chromosome. This region encodes a mechanism for the uptake and metabolism of polysaccharides, including a polysaccharide utilization locus (PUL operon) that appears specific to fucoidan, providing new insight into the biochemical pathways regulating structural colour in bacteria.
... Thus, it can be argued that G. galloti populations on Tenerife are exceptionally well suited to study environmental adaptation. It has been the subject of numerous pioneering studies (e.g., Thorpe and Baez, 1987;Thorpe and Brown, 1989a;Thorpe, 1991;Thorpe et al., 1996;Thorpe and Richard 2001;Brown et al., 2016), encompassing aspects of morphology, colouration, sexual selection, parasites, chemical signals, environmental stress tolerance, locomotion, activity, thermoregulation, and digestive ecology (e.g., Díaz, 1994;Vanhooydonck et al., 2001;Valido and Nogales, 2003;Font and Molina-Borja, 2004;Huyghe et al., 2005;Bohórquez-Alonso et al., 2011;Megía Palma et al., 2016García-Roa et al., 2017). Furthermore, genetic variation within the species is complex, and while one of its components appears to have arisen during historical allopatry (possibly associated with volcanism), a second is related to xeric/mesic habitat differences and shows signatures to be expected under divergent selection between these areas (Brown et al., 2016). ...
... This suggested that SCD correlated with reproductive investment and/or male competition ability (territoriality) in this population. Interestingly, during the second breeding season, lizards from TLQ group significantly increased their pigmentation and the infection by Karyolysus as compared to lizards from the CLQ group (Fig. 5), suggesting that the higher allocation of pigment to colour patches was associated with increased susceptibility to some parasites in line with a handicapping mechanism (Salvador et al. 1996;Megía-Palma et al. 2016b. Nonetheless, future experimental manipulation of the reproductive effort and/or the parasite load of the lizards is needed to fully discriminate their effects on coloration (e.g., Megía-Palma et al. 2018b). ...
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Ontogeny is expected to be a determinant factor affecting production of colour patches in lizards, while immune challenges or sudden weight loss may impair the maintenance of pigment-based coloration within a breeding season. We translocated males of the lizard Psammodromus algirus between two sampling plots that differed in distance to a road, vegetation structure, and predator abundance. We analysed variation in spectral reflectance of their colour patches the same and the following year. The change in the reflectance of the lizard colour patches within the first breeding season was explained by the interaction between plot and treatment, but not body condition. The maintenance of the breeding coloration was impaired only in those males translocated close to the road, probably reflecting that it is a poor-quality habitat for P. algirus . The following year, lizards that produced a more elaborate coloration were those that increased their body condition and controlled some parasitic infections, although suffered an increase of others. This study shows that colour patch production is plastic in P. algirus . Lizards increasing parasites or losing weight reduced pigmentation, although habitat quality can cushion these negative effects on pigmentation. However, not all parasites constrain the investment in coloration. In fact, some increased in those lizards that allocated more pigments to colour patches. In conclusion, longitudinal studies following experimental manipulation can contribute to understand pigment allocation rules in lizards. Significance statement Pigments involved in colour patches of animals are limiting resources that can be reallocated off the skin to other functions. However, longitudinal evidence of this phenomenon is scarce in reptiles. We designed a manipulative mark-recapture experiment to investigate effects of habitat and parasitic infections on colour patch maintenance (within-year variation) and production (between-year variation) in male free-ranging lizards that were reciprocally translocated between two patches of habitat that differed in quality. During the first year, lizards translocated to the habitat with more predators and worse vegetation impoverished their coloration, while lizards translocated to the more favourable habitat maintained it despite all translocated lizards loose body condition. The next year we detected different effects on the coloration of three different parasites investigated, suggesting that coloration can reflect the virulence of the infections.
... Studies on lizard coloration frequently recover biologically relevant differences among individuals correlated with colour variation, either depending on ontogeny e.g., [9], reproductive status e.g., [10], performance e.g., [11][12][13] or body condition that can be affected, for example by parasite load, disease and immune system function e.g., [14,15] and stress level e.g., [16]. Specifically, the content of carotenoids within the xanthophores may arise from the physiological trade-off between carotenoid-based coloration and immune and antioxidant functions [3]. ...
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Colour polymorphism may be accompanied by alternative expressions of phenotypic traits that are directly or indirectly related to fitness, and selection forces may act on the traits separately or concurrently. In polymorphic species, natural selection may act through frequency- or density-dependent mechanisms and maintain polymorphism through interactions among morphs. We used an integrative approach to examine functionally relevant and interrelated life history traits in the context of colour polymorphism in the European wall lizard (Podarcis muralis). Body, head and limb morphology, bite and locomotor performance, and physiology, particularly metabolic and antioxidant capacity, were analysed in the three pure colour morphs (yellow, orange, white) and the two mosaic morphs (yellow-orange and white-orange). Morphological differences between morphs were present but subtle and consisted mainly of variations in head length. Head size and bite force were strongly associated between and within morphs. Limb and boot morphology and locomotor performance (sprinting and climbing) were variably associated among morphs. Finally, variation in biochemical indicators of cellular metabolism and antioxidant capacity appeared to be largely independent of morphology and performance. The results provide evidence for existing and non-existing relationships between colour and morphology, performance, and physiology that could have short- and long-term effects on selection.
... Over the past decade, a growing body of evidence has been accumulated on the involvement of UV coloration in intrasexual competition and the role of these UV color traits as badges of status (Lim and Li 2013;Xu and Fincke 2015;Martin et al. 2016;Sabol et al. 2017). A higher UV reflectance appears to convey information on RHP (Stapley and Whiting 2006;Whiting et al. 2006;Tringali and Bowman 2012;Lim and Li 2013), a better immune response (Doucet and Montgomerie 2003;Griggio et al. 2010;Megía-Palma et al. 2016), or a higher testosterone level (Roberts et al. 2009). The signal honesty of UV signals has been suggested to be ensured by the immunocompetence handicap mechanism (Folstad and Karter 1992;Roberts et al. 2009) but mainly through a social cost (Martin et al. 2016). ...
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In many animals, males engage in agonistic interactions. Color signals are commonly used to mitigate these potentially harmful interactions. Both pigment-based color and structural color, notably ultraviolet coloration, are used in this context to convey information, including an animal’s resource holding potential (RHP) or social status. Despite extensive previous work on this topic, the ability to change color in this context has received relatively little attention. Moreover, no studies have considered the visible and the ultraviolet components of this ability. Thus, whether changes in ultraviolet play a role in settling intraspecific disputes remains unknown. Here, we investigate the role of color change during intrasexual agonistic interactions in male panther chameleons (Furcifer pardalis). To do so, we combined behavioral experiments and color analysis. Our results show that the outcome of male intrasexual agonistic interactions depends on particular aspects of color change in the visible spectrum. Dominant males exhibit more brightness changes and Euclidian distance changes within the HSV color space at the level of the bands and interbands, suggesting a prominent role of these patterns in panther chameleon communication. Our results also align with previous studies in another chameleon species, thus supporting the key role of brightness changes in chameleon communication, at least in a competitive context. Interestingly, although our species did exhibit UV coloration, neither this coloration nor its changes seem to be involved in intrasexual agonistic interactions among males, possibly because those signals may be used for other purposes like attracting mates, repelling predators, or deception.
... Reflectance was measured using a spectrophotometer (Jaz Ocean Optics) with a Pulsed Xenon Light Source (Jaz-PX) connected to an optical fiber within the 300-700 nm range, which includes most of the spectrum reflected by lizards' dorsa. The probe was mounted within a holder that ensured readings were taken from areas 1 mm in diameter at a constant distance of 3 mm from the skin surface with a 45 • angle (Megía-Palma et al., 2016;González-Morales et al., 2021). All measurements were relative to a 99% WS-1 white reflectance standard (all components from Ocean Optics Inc. Dunedin. ...
Sprint speed is a major performance trait in animal fitness involved in escaping from predators, obtaining food, and defending territory. Biotic and abiotic factors may influence sprint speed in lizards. Temperature decreases at higher altitude. Therefore, lizards at high elevations may require longer basking times to reach optimal body temperatures, increasing their vulnerability to predation and decreasing their time for other activities such as foraging or reproduction. Here, we tested whether the maximum sprint speed of a lizard that shows conservative thermal ecology varied along an altitudinal gradient comprising low (2500 m), middle (3400 m) and high-altitude (4300 m) populations. We also tested whether sprint speed was related to dorsal reflectance at different ecologically relevant temperatures. Given that the lizard Sceloporus grammicus shows conservative thermal ecology with altitude, we expected that overall average sprint speed would not vary with altitude. However, given that darker lizards heat up quicker, we expected that darker lizards would be faster than lighter lizards. Our results suggest that S. grammicus at high altitude are faster and darker at 30 °C, while lizards from low and middle altitude are faster and lighter in color at 20 °C than high altitude lizards. Also, our results suggest a positive relationship between sprint speed and dorsal skin reflectance at 10 and 20 °C. Sprint speed was also affected by snout-vent length, leg length, and leg thickness at 10 °C. These results suggest that, even though predation pressure is lower at extreme altitudes, other factors such as vegetation cover or foraging mode have influenced sprint speed.
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Diurnal lizards are useful model organisms for the study of color polymorphisms. The cellular basis of nonavian reptilian coloration and dermal chromatophores, as well as the different pigments contained therein, is relatively well understood. Nonetheless, specific predictions cannot be made for the biochemical chromatophore constituents of individual species a priori. Despite well-documented associations between throat coloration and behavioral, physiological, and life history traits, the cellular basis of throat coloration in polymorphic Common Side-Blotched Lizards, Uta stansburiana, has never been studied. We used a combination of chromatographic techniques in conjunction with transmission electron microscopy and a thin-layer reflectance model to determine the cellular basis of polymorphic coloration in U. stansburiana. We found that different morphs express coloration through varying spatial arrangements of dietary xanthophylls (lutein and zeaxanthin), differential synthesis of drosopterins, differential melanin synthesis, and morph-specific iridophore reflecting platelets. Our results indicate that chromatic variations in this polymorphism cannot be attributed to alternative xanthophore pigmentation or structural reflectance alone. Instead, the chromatophores of U. stansburiana are multicomponent color signals.
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Ectoparasites may imply a cost in terms of oxidative stress provoked by the inflammatory responses in hosts. Ectoparasites may also result in costs for nestlings and brooding females because of the direct loss of nutrients and reduced metabolic capacity resulting from parasite feeding activities. These responses may involve production of reactive oxygen and nitrogen species that may induce oxidative damage in host tissues. Our goal was to examine the effect of ectoparasites in terms of oxidative stress for nestlings and adult females in a population of pied flycatchers Ficedula hypoleuca. We manipulated the entire nest ectoparasite community by reducing ectoparasite loads in some nests through a heating treatment and comparing them with a control group of nests with natural loads. A marker of total antioxidant capacity (TAS) in plasma and total levels of glutathione (tGSH) in red blood cells as well as a marker of oxidative damage in plasma lipids (malondialdehyde, MDA) were assessed simultaneously. Levels of tGSH were higher in heat-treated nests than in controls for both females and nestlings. Higher TAS values were observed in females from heat-treated nests. In nestlings there was a negative correlation between TAS and MDA. Our study supports the hypothesis that ectoparasites expose cavity-nesting birds to an oxidative challenge. This could be paid in the long-term, ultimately compromising individual fitness.
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Many chameleons, and panther chameleons in particular, have the remarkable ability to exhibit complex and rapid colour changes during social interactions such as male contests or courtship. It is generally interpreted that these changes are due to dispersion/aggregation of pigment-containing organelles within dermal chromatophores. Here, combining microscopy, photometric videography and photonic band-gap modelling, we show that chameleons shift colour through active tuning of a lattice of guanine nanocrystals within a superficial thick layer of dermal iridophores. In addition, we show that a deeper population of iridophores with larger crystals reflects a substantial proportion of sunlight especially in the near-infrared range. The organization of iridophores into two superposed layers constitutes an evolutionary novelty for chameleons, which allows some species to combine efficient camouflage with spectacular display, while potentially providing passive thermal protection.
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Cnemidophorus arubensis, an endemic teiid lizard of Aruba island, Netherlands Antilles, is parasitized by a haemogregarine protozoan. The proportion of animals infected (prevalence) was greater for males than females and for adults compared to juveniles. Brightly colored males were more likely to be infected than blandly colored males of the same body size. Percent of erythrocytes infected with parasite gametocytes, and parasite prevalence, were similar in both wet and dry seasons. Infected and noninfected lizards were similar for several hematological, physiological, anatomical, and behavioral measures of parasite virulence. The Aruban haemogregarine appears to have an avirulent effect on Cnemidophorus arubensis.
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Males and females from Lacertid lizard species often display conspicuous colourations involved in intraspecific communication. However, visual systems of Lacertidae have rarely been studied and the spectral sensitivity of their retinal photoreceptors remains unknown. Here, we characterised spectral sensitivity of two Lacertid species from contrasted habitats, the wall lizard Podarcis muralis and the common lizard Zootoca vivipara. Both species possess a pure-cone retina with one spectral class of double cones and four spectral classes of single cone photoreceptors. The two species differ in the spectral sensitivity of the LWS cones, the relative abundance of UVS single cones (potentially more abundant in Z. vivipara), and the colouration of oil droplets. Wall lizards have pure vitamin A1-based photopigments while common lizards possess mixed vitamin A1- and A2- photopigments extending spectral sensitivity into near infrared, a rare feature in terrestrial vertebrates. We found that spectral sensitivity in the UV and in the near infrared improves discrimination of small variation in throat colouration among Z. vivipara. Thus, retinal specialisations optimise chromatic resolution in common lizards, which indicates that visual system and visual signals may co-evolve.
Knowledge of melanin chemistry has important implications for the study of the evolutionary ecology of animal pigmentation, but the actual chemical diversity of these widely expressed biological pigments has been largely overlooked. Considering all melanin forms and the different conditions of endogenous oxidative stress during their synthesis provides information about physiological costs and benefits of different pigmentation patterns and opens a new perspective to understanding the evolution of color phenotypes in animals.