Colour Morphs Research Articles

Size, more than colour, drives dyadic interactions in sub-adults of a colour polymorphic cichlid

Abstract Social and aggressive behaviours often affect the fitness of multiple interacting individuals simultaneously. Here, we assessed dyadic interactions in a colour-polymorphic cichlid fish, the red devil, Amphilophus labiatus. We found that sub-adult red devil pairs of smaller body size interacted more, and were more aggressive towards each other, than pairs comprising larger individuals. Interactions did not significantly differ between colour morphs, i.e. between dark, gold and heterotypic pairs. Interestingly, within a broad range of parameters, an automated measure of time that the two fish spent in close proximity was an accurate proxy for their level of aggression, as measured by an observer from video recordings. These results show that, between sub-adult red devils, (aggressive) interactions significantly depend on body size, but not colour morph, of the interacting individuals. In addition, the results support the use of automated data-gathering approaches as an appropriate tool for studies of aggression.

No genomic repercussions of assortative pairing in a colour polymorphic lizard.

Long-term maintenance of colour polymorphisms often depends on the interplay of multiple selective forces. In the common wall lizard (Podarcis muralis), up to three pure and two mosaic ventral colour morphs co-exist across most of its range. Available evidence suggests that colour morphs in this species are maintained through the interaction between sexual and environment-dependent selection. In particular, colour-assortative pairing has been recorded, suggesting some degree of assortative mating. Here, we combined reduced-representation sequencing (ddRADseq) and fine-scale distribution data to explore the effects of assortative pairing on the common wall lizard. Overall, our results do not support any population structure (FST =0 and K=1) nor a significant effect of colour morph or geographic location on genomic differentiation. Therefore, we argue that assortative pairing may not fully translate into assortative mating and genomic differentiation between colour morphs and discuss possible explanations. Nonetheless, we find potential support for an elevated population size and/or source-sink dynamics and debate the potential contribution of other forms of selection to the maintenance of colour polymorphisms in lacertids.

Does the thermal mismatch hypothesis predict disease outcomes in different morphs of a terrestrial salamander?

Many aspects of ectotherm physiology are temperature-dependent. The immune system of temperate-dwelling ectothermic host species is no exception and their immune function is often downregulated in cold temperatures. Likewise, species of ectothermic pathogens experience temperature-mediated effects on rates of transmission and/or virulence. Although seemingly straightforward, predicting the outcomes of ectothermic host-pathogen interactions is quite challenging. A recent hypothesis termed the thermal mismatch hypothesis posits that cool-adapted host species should be most susceptible to pathogen infection during warm temperature periods whereas warm-adapted host species should be most susceptible to pathogens during periods of cool temperatures. We explore this hypothesis using two ecologically and physiologically differentiated color morphs of the Eastern Red-backed Salamander (Plethodon cinereus) and a pathogenic chytrid fungus (Batrachochytrium dendrobatidis; hereafter "Bd") using a fully factorial laboratory experiment. At cool temperatures, unstriped salamanders (i.e., those that are tolerant of warm temperatures) had a significantly higher probability of Bd infection compared with cool-tolerant striped salamanders, consistent with the thermal mismatch hypothesis. However, we found no support for this hypothesis when salamanders were exposed to Bd at warm temperatures: the probability of Bd infection in the cool-tolerant striped salamanders was nearly identical in both cool and warm temperatures, opposite the predictions of the thermal mismatch hypothesis. Our results are most consistent with the fact that Bd grows poorly at warm temperatures. Alternatively, our data could indicate that the two color morphs do not differ in their tolerance to warm temperatures but that striped salamanders are more tolerant to cool temperatures than unstriped salamanders.

Landscape and dynamics of accessible chromatin during pigmentation process in green, white and purple sea cucumber Apostichopus japonicus

Cis-regulatory sequences, such as enhancers, control development and physiology by regulating gene expression. The identification and functional characterization of these distal regulatory elements remains challenging, especially in non-model aquatic organisms like sea cucumbers. Apostichopus japonicus, an important echinoderm species, exhibits diverse body colour. Pigmentation is an important stage of growth and development in this species, but the regulatory mechanism remains poorly understood, especially the extent to which epigenetic changes regulate pigmentation. Herein, we globally profiled chromatin accessibility using the assay for transposase-accessible chromatin sequencing technique during pigmentation in green, white and purple sea cucumbers. We have got 27, 817 peaks in total and discovered 1427 peaks showing differentially accessed DNA sites across the genome, which were categorized into four distinct clusters via unsupervised hierarchical clustering. Among three colour morphs, white sea cucumber exhibited the most extensive changes and the greatest differences from the other two colour morphs. Global increases in chromatin accessibility occur in the late pigmentation stage suggesting that active function in the late pigmentation stage drives body colour formation. The screened key cis-regulatory elements KIT, RPS6KB2 and IRF8 may contributed to the albinism, slow growth and poor disease resistance of white sea cucumber. In conclusion, our study provides a framework for understanding the accessible chromatin dynamics of body colour diversity during echinoderm pigmentation process and a new avenue to unravel the transcriptional regulatory mechanisms that facilitate the occurrence of relevant molecular events.

Correction to: Assessment of Variation in Feeding Behavior by Color Morph in the Asian citrus Psyllid (Diaphorina citri)

Correction to: Assessment of Variation in Feeding Behavior by Color Morph in the Asian citrus Psyllid (Diaphorina citri)

Is It Function or Fashion? An Integrative Analysis of Morphology, Performance, and Metabolism in a Colour Polymorphic Lizard

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.

Integrative Taxonomy, Distribution and Ontogenetic Colouration Change in Neotropical Mountain Catfishes of the Trichomycterus nigroauratus Group (Siluriformes: Trichomycteridae).

Catfishes of the genus Trichomycterus comprise the most diverse fish group in mountain river basins crossing the Atlantic Forest of south-eastern Brazil, with a great concentration of species in the Rio Paraíba do Sul basin. The present study is directed to the T. nigroauratus group, endemic to the Rio Paraíba do Sul basin, comprising species commonly found associated with bottom leaf litter. Field studies revealed two sympatric, distinct colour morphs, one comprising small specimens with a black longitudinal stripe over a pale brown ground colour on the flank and another comprising a single larger specimen with small dark browns spots scattered over a pale-yellow ground colour. These specimens were found in the upper Rio Paraitinga drainage, an area disjunct from the area inhabited by the other species of the group. We performed coalescent single-locus analyses for species delimitation using a cytochrome b fragment (1088 bp) for specimens from eight localities, including sequences taken from specimens exhibiting different colouration morphs and topotypes of all the three nominal species of the T. nigroauratus group. The analyses supported the two colouration morphs as belonging to a single species that is herein described. It is distinguished from other congeners by its unique colour pattern, dorsal and anal fins fin more posteriorly placed, and by the morphology of the opercle, metapterygoid and pelvic bone. The Maximum Likelihood analysis indicated the new species as sister to a clade containing all other congeners of the group, which is corroborated by osteological data. The occurrence of different lineages in neighbouring areas of the upper Rio Paraíba do Sul basin is interpreted as a possible vestige of a past complex paleogeographical scenario during the Cenozoic. The present record of striking ontogenetic colouration change, revealed only after checking DNA sequences of individuals exhibiting different colouration phenotypes, again highlights the importance of combining morphological and molecular data in taxonomical studies.

Color Variation and Habitat Use in Liolaemus silvai

Liolaemus is a species-rich genus endemic to South America with relatively little known about the biology of most of the > 200 included species. One species, L. silvai is common in the coastal Atacama Desert and is sexually dimorphic. We studied their phenotypic variation in color and body size, as well as habitat use by capturing lizards active on the surface. To assess phenotypic variation, we categorized the color morph of each lizard based on visible coloration in their ventral throat region and their ventral body from the shoulder girdle to the hips. We also sexed each lizard, measured snout–vent length and body mass, and recorded incidences of tail breakage. For habitat use we measured perch height, distance from the rock edge to nearest vegetation, and the height of the rocks on which lizards were initially sighted. We assessed habitat selection by comparing perch characteristics to features available in the habitat by pairing capture rocks with the nearest rock in a random direction from the initial perch site. Male L. silvai were significantly larger than females, but color morph and tail break frequency were independent of sex. Lizards used rocks that were significantly closer to vegetation than random rocks available in the environment independently of sex or color morph. We document the same pattern for perch height. Future studies are needed to examine the exact role of vegetation for L. silvai.

The weaker sex: Male lingcod (Ophiodon elongatus) with blue color polymorphism are more burdened by parasites than are other sex-color combinations.

The unusual blue color polymorphism of lingcod (Ophiodon elongatus) is the subject of much speculation but little empirical research; ~20% of lingcod individuals exhibit this striking blue color morph, which is discrete from and found within the same populations as the more common brown morph. In other species, color polymorphisms are intimately linked with host–parasite interactions, which led us to ask whether blue coloration in lingcod might be associated with parasitism, either as cause or effect. To test how color and parasitism are related in this host species, we performed parasitological dissection of 89 lingcod individuals collected across more than 26 degrees of latitude from Alaska, Washington, and California, USA. We found that male lingcod carried 1.89 times more parasites if they were blue than if they were brown, whereas there was no difference in parasite burden between blue and brown female lingcod. Blue individuals of both sexes had lower hepatosomatic index (i.e., relative liver weight) values than did brown individuals, indicating that blueness is associated with poor body condition. The immune systems of male vertebrates are typically less effective than those of females, due to the immunocompromising properties of male sex hormones; this might explain why blueness is associated with elevated parasite burdens in males but not in females. What remains to be determined is whether parasites induce physiological damage that produces blueness or if both blue coloration and parasite burden are driven by some unmeasured variable, such as starvation. Although our study cannot discriminate between these possibilities, our data suggest that the immune system could be involved in the blue color polymorphism–an exciting jumping-off point for future research to definitively identify the cause of lingcod blueness and a hint that immunocompetence and parasitism may play a role in lingcod population dynamics.

Cold winters have morph-specific effects on natal dispersal distance in a wild raptor.

Dispersal is a key process with crucial implications in spatial distribution, density, and genetic structure of species’ populations. Dispersal strategies can vary according to both individual and environmental features, but putative phenotype-by-environment interactions have rarely been accounted for. Melanin-based color polymorphism is a phenotypic trait associated with specific behavioral and physiological profiles and is, therefore, a good candidate trait to study dispersal tactics in different environments. Here, using a 40 years dataset of a population of color polymorphic tawny owls (Strix aluco), we investigated natal dispersal distance of recruiting gray and pheomelanic reddish-brown (hereafter brown) color morphs in relation to post-fledging winter temperature and individual characteristics. Because morphs are differently sensitive to cold winters, we predicted that morphs’ natal dispersal distances vary according to winter conditions. Winter temperature did not affect the proportion of brown (or gray) among recruits. We found that dispersal distances correlate with winter temperature in an opposite manner in the two morphs. Although the gray morph undertakes larger movements in harsher conditions, likely because it copes better with winter severity, the brown morph disperses shorter distances when winters are harsher. We discuss this morph-specific natal dispersal pattern in the context of competition for territories between morphs and in terms of costs and benefits of these alternative strategies. Our results stress the importance of considering the interaction between phenotype and environment to fully disentangle dispersal movement patterns and provide further evidence that climate affects the behavior and local distribution of this species.

Another case of colour pattern polymorphism in Earth Snakes of the genus Geophis (Dipsadidae) from southern Mexico

ABSTRACT Geophis laticollaris and G. russatus are rare Mexican snakes currently known in the scientific literature only from their holotypes. However, fieldwork conducted in the states of Guerrero and Oaxaca by us and other workers during the last decades has made a few specimens of each taxon available for study. We review the taxonomic status of G. russatus on the basis of scutellation, colour pattern, maxillary, and hemipenial characters and sequences of a fragment of the cyt-b mitochondrial gene. We conclude that G. russatus is a colour morph and a junior synonym of G. laticollaris.

Evidence for morph-specific substrate choice in a green-brown polymorphic grasshopper.

Orthopteran insects are characterized by high variability in body coloration, in particular featuring a widespread green-brown color polymorphism. The mechanisms that contribute to the maintenance of this apparently balanced polymorphism are not yet understood. To investigate whether morph-dependent microhabitat choice might contribute to the continued coexistence of multiple morphs, we studied substrate choice in the meadow grasshopper Pseudochorthippus parallelus. The meadow grasshopper occurs in multiple discrete, genetically determined color morphs that range from uniform brown to uniform green. We tested whether three common morphs preferentially choose differently colored backgrounds in an experimental arena. We found that a preference for green backgrounds was most pronounced in uniform green morphs. If differential choices improve morph-specific performance in natural habitats via crypsis and/or thermoregulatory benefits, they could help to equalize fitness differences among color morphs and potentially produce frequency-dependent microhabitat competition, though difference appear too small to serve as the only explanation. We also measured the reflectance of the grasshoppers and backgrounds and used visual modeling to quantify the detectability of the different morphs to a range of potential predators. Multiple potential predators, including birds and spiders, are predicted to distinguish between morphs chromatically, while other species, possibly including grasshoppers themselves, will perceive only differences in brightness. Our study provides the first evidence that morph-specific microhabitat choice might be relevant to the maintenance of the green-brown polymorphisms in grasshoppers and shows that visual distinctness of color morphs varies between perceivers.

Intraspecific diversity alters the relationship between climate change and parasitism in a polymorphic ectotherm.

Climate-modulated parasitism is driven by a range of factors, yet the spatial and temporal variability of this relationship has received scant attention in wild vertebrate hosts. Moreover, most prior studies overlooked the intraspecific differences across host morphotypes, which impedes a full understanding of the climate-parasitism relationship. In the common lizard (Zootoca vivipara), females exhibit three colour morphs: yellow (Y-females), orange (O-females) and mixed (mixture of yellow and orange, M-females). Zootoca vivipara is also infested with an ectoparasite (Ophionyssus mites). We therefore used this model system to examine the intraspecific response of hosts to parasitism under climate change. We found infestation probability to differ across colour morphs at both spatial (10sites) and temporal (20years) scales: M-females had lower parasite infestations than Y- and O-females at lower temperatures, but became more susceptible to parasites as temperature increased. The advantage of M-females at low temperatures was counterbalanced by their higher mortality rates thereafter, which suggests a morph-dependent trade-off between resistance to parasites and host survival. Furthermore, significant interactions between colour morphs and temperature indicate that the relationship between parasite infestations and climate warming was contingent on host morphotypes. Parasite infestations increased with temperature for most morphs, but displayed morph-specific rates. Finally, infested M-females had higher reductions in survival rates than infested Y- or O-females, which implies a potential loss of intraspecific diversity within populations as parasitism and temperatures rise. Overall, we found parasitism increases with warming temperatures, but this relationship is modulated by host morphotypes and an interaction with temperature. We suggest that epidemiological models incorporate intraspecific diversity within species for better understanding the dynamics of wildlife diseases under climate warming.

Fecal Pellet Mass as a Function of Body Size, Color Morph, and Season in Plethodon cinereus (Green, 1818) (Amphibia: Plethodontidae)

In plethodontid salamanders, fecal pellets have a variety of behavioral functions related to chemical communication. We examined how fecal pellet mass in the Eastern Red-backed Salamander (Plethodon cinereus) varies with body size, color morph, and season. Fecal pellet mass increased with salamander size. Striped P. cinereus produced heavier fecal pellets than unstriped P. cinereus. Fecal pellet size tended to be greater in the spring than in the fall. Our results suggest further investigations of the factors governing fecal pellet size in plethodontid salamanders is warranted.

Biology of the oldest butterfly species in the world, Baronia brevicornis: food, abundance, polymorphism, and survival

The study of the basic biology of panchronic species could help understand their persistence through geological time. One of the least studied panchronic species is Baronia brevicornis Salvin (Lepidoptera: Papilionidae), the oldest known butterfly species endemic to Mexico. Here we report on our findings from studying a population of B. brevicornis in Sierra de Huautla, Morelos, for 3 years. In this population we identified 3 male and 3 female color morphs, making it perhaps the most complex polymorphism described yet for a panchronic species. We found a balanced sex ratio in newly emerged adults but a sex ratio biased to males at reproductive sites. Significantly, we found adults of the butterfly only on patches of the host plant Vachellia campechiana (Mill.) Seigler & Ebinger (Fabaceae) that also offered feeding sources for adults and report for the first-time adults feeding on 5 plant species. Additionally, differences in water use in trees of V. campechiana in zones with or without B. brevicornis suggest a relationship between butterfly food sources and plant water expenditure. Our findings on B. brevicornis could be used to develop conservation plans for this species.

New observations on the corallivorous nudibranchPhestilla melanobrachia: morphology, dietary spectrum and early development

ABSTRACTPhestilla melanobrachia is a coral-eating nudibranch widely distributed in the tropical Pacific. Previous studies have revealed only two colour morphs of P. melanobrachia, an orange form preying on various orange Dendrophyllia and Tubastraea spp. and a dark green form preying on the black Tubastraea micrantha and Tubastraea diaphana. Both colour morphs live in relatively deep waters (15–25 m) of exposed shores. We conducted morphological and molecular analysis, which revealed a beige colour morph of P. melanobrachia that feeds on the hermatypic scleractinian coral Turbinaria peltata in shallow waters (<10 m). The three genera of corals all belong to the family Dendrophylliidae, but Dendrophyllia and Tubastraea are azooxanthellates whereas Turbinaria is zooxanthellate. Consistent with their diet, the beige colour morph has a high abundance of dinoflagellate cells in the ceratal tips, whereas the other two colour morphs contain only few or no dinoflagellate cells in their cerata. Our finding of this new colour morph extends the knowledge about the diet, ecological niche and potential ecological impact of this species of corallivorous nudibranch.

A review of the Indian species of Apochinomma Pavesi, 1881 and Corinnomma Karsch, 1880, synonymy of Castianeira quadrimaculata Reimoser, 1934, and a catalogue of the Indian corinnid fauna (Arachnida: Araneae).

Indian species of the genera Apochinomma Pavesi, 1881 and Corinnomma Karsch, 1880 are reviewed. Corinnomma rufofuscum Reimoser, 1934 syn. nov. is synonymised with A. nitidum (Thorell, 1895). Redescriptions of A. nitidum and C. severum (Thorell, 1877) are provided, and two colour morphs (brown and black) of A. nitidum are illustrated. Supplementary descriptions for A. dolosum Simon, 1897 and C. comulatum Thorell, 1891 are provided. The species Castianeira quadrimaculata Reimoser, 1934 syn. nov. is recognised as a junior synonym of Coenoptychus pulcher Simon, 1885. Images of all the examined type material are provided and a catalogue of Indian corinnid species is presented.

Water content in diet affects growth and timing of female first mating, but not coloration, in the admirable grasshopper (Syrbula admirabilis)

AbstractUnderstanding how water limitation affects the performance of herbivorous insects is relevant in a context of worldwide alterations of rainfall regimes due to climate change. Apart from its influence on insect growth and development, water availability has also been considered a cue for color polyphenism in some species. This is the case of the grassland‐inhabiting admirable grasshopper (Syrbula admirabilis), for which water content in plant tissues, a potentially reliable cue to predict future vegetation conditions, has been proposed to determine the frequency of green–brown color morphs. We performed an experiment that manipulated water content of the diet (dry/wet treatment) in a group of individually monitored admirable grasshoppers to explore the effects on imago size, timing of female first mating, and coloration. Our results showed that grasshoppers in the wet treatment achieved larger sizes, and females mated comparatively earlier, than their counterparts in the dry treatment. We also found that hue (the dominant color) in imagines was significantly lower (browner) than in nymphs, but the magnitude of this color shift did not differ between treatments. This study supports the idea that water limitation has a negative impact on grasshopper growth and development, but rules out dietary water content as a cue for color polyphenism. This result encourages additional research to assess the actual contribution of environmental and genetic factors to color determination in admirable grasshoppers. Such information could help to better understand how color polymorphism is maintained in natural populations and to predict how it could evolve in a future in which environmental conditions will become more unpredictable.

Indian Star Tortoise, Geochelone elegans (Schoepff,1795): an unusual color morph and the threat of roadkills in Gujarat, India

Indian Star Tortoise, Geochelone elegans (Schoepff,1795): an unusual color morph and the threat of roadkills in Gujarat, India

Importance of melanin‐based colouration and environment in shaping intracellular glutathione levels in nestling and adult tawny owls Strix aluco

Resources allocated in reproduction are traded off against those invested in self‐maintenance such as antioxidant response. Glutathione (GSH) is an intracellular antioxidant defence that scavenges reactive oxygen species, the deleterious byproducts of oxygen consumption. Given the role of intracellular GSH in pheomelanogenesis, a trade‐off in GSH allocation between resistance in oxidative stress and melanin production may take place. To investigate how intracellular GSH is regulated in differently coloured individuals at the time of reproduction (in adults) and of intense melanogenesis (in nestlings), we measured the total pool of GSH produced (tGSH), consumed (oxGSH) and available (redGSH) in adult tawny owls and their offspring which were cross‐fostered between randomly chosen nests. Our goal was to describe potential correlations between resistance in oxidative stress and colour morphs in natural conditions. Nestling GSH levels were correlated with GSH levels in their genetic and foster parents suggesting that producing GSH is genetically and environmentally determined (although the effect of the foster nest seemed stronger). This species shows continuous variation in pheomelanin reddish colouration, which is associated with life‐history strategies. Based on the hypothesis of GSH dependence of pheomelanism, we expected a greater amount of oxGSH in dark compared to light pheomelanic nestlings, which was not the case. In contrast, light melanic breeding adults had higher levels of tGSH and redGSH than dark breeders probably because of a higher investment in antioxidant capacity. The link between pheomelanism and GSH may therefore be due to the fact that differently colored individuals have different life‐history strategies rather than because the production of pheomelanin pigments requires GSH.