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

Abstract

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.

Along for the ride or missing it altogether: exploring the host specificity and diversity of haemogregarines in the Canary Islands

“…Parasite prevalence, parasitaemia and genetic diversity were higher in Gallotia hosts than in Tarentola and Chalcides (values in Gallotia spp. were consistent with previous studies [ 39 – 43 ]). Interestingly, a similar trend was also observed in nematodes of the genus Spauligodon infecting the same hosts [ 37 ].…”

“…However, this widening of host breadth seems to have been temporary, as contemporary host-parasite associations show a high level of host specificity, differing from the Island Syndrome expectations. Regarding haemogregarines, these parasites have been found in the archipelago infecting lizards of the genera Gallotia [ 38 – 43 ] and Tarentola [ 44 ]. However, in most cases detection was based on microscopy, and only one work suggests different haemogregarine morphological forms infecting Gallotia [ 37 ].…”

Opposed elevational variation in prevalence and intensity of endoparasites and their vectors in a lizard

“…2013 ), which is not consistent with the pattern of hemoparasite variation reported here. Lizards could be more susceptible to hemoparasites at high elevations, given that highland lizards invest more resources in colour signals ( Reguera 2015 ), and other studies have reported that lizards with more colorful colorations suffer from increased infection by hemoparasites ( Megía-Palma et al. 2016a , 2016b ).…”

“…We performed thin blood smears that were air dried and fixed with methanol. Smears were stained for 40 min with Giemsa diluted 1: 10 in buffer, pH 7.2 ( Megía-Palma et al. 2016a , 2016b ).…”

Effects of energy and thermoregulation time on physiological state and sexual signal in a lizard

“…Well‐fed lizards were also able to maintain more intense throat coloration than food‐deprived individuals. Production and maintenance of structural colors have been shown to be energetically costly (Megía‐Palma, Martínez, & Merino, ; Prum, ), with both developmental stress and available nutrients influencing coloration in lizards (Olsson et al., ). Additionally, previous studies showed that nuptial throat coloration is condition dependent (Molnár et al., ) and affected by environmental factors (Bajer et al., ) in the study species.…”