Carotenoid-based colour polyphenism in a moth species: search for fitness correlates

Carotenoid‐based integumental coloration is often associated with individual performance in various animals. This is because the limited amount of the pigment has to be allocated to different vital functions. However, most of the evidence for the carotenoid‐based trade‐off comes from vertebrate studies, and it is unclear if this principle can be applied to insects. This possibility was investigated in Orgyia antiqua L. (Lepidoptera: Lymantriidae). The larvae of this species are polyphenic in their coloration, varying from a highly conspicuous combination of yellow hair tufts on black background to cryptic appearance with brown hair tufts. The conspicuous larvae are aposematic, advertising their aversive hairiness. The maintenance of different colour morphs in O. antiqua requires explanation, as an aposematic signal is expected to evolve towards monomorphism. Chromatographic analysis showed that the yellow coloration of the hair is based on the carotenoid pigment lutein (α‐carotene‐3,3’‐diol). The colour of hair tufts was dependent on their carotenoid content. This justifies an expectation of carotenoid‐based physiological trade‐offs between aposematic coloration and individual performance. To test this hypothesis, we monitored life histories of differently coloured larvae reared on various host plants, recording their body sizes, growth rates, and mortalities in each instar. There was a significant but relatively low heritability of tuft coloration, which allowed us to expect environmental effects. We found no phenotypic associations between hair tuft colour and performance indices in O. antiqua larvae, neither did the quality of host plant affect the frequency of colour morphs. However, the frequency of colour morphs differed between larval instars. Our results suggest that carotenoid‐mediated physiological trade‐offs are not involved in the maintenance of colour morphs in O. antiqua larvae, and factors other than individual condition should be responsible for the observed variability.     

How caterpillars avoid overheating: behavioral and phenotypic plasticity of pipevine swallowtail larvae

We tested the hypothesis that larvae of the pipevine swallowtail butterfly, Battus philenor, employ behavioral and phenotypic plasticity as thermoregulatory strategies. These larvae are phenotypically varied across their range with predominantly black larvae (southeastern USA and California) and red larvae (western Texas, Arizona) occurring in different regions. Two years of field observations in south Texas indicate that the proportion of red larvae increases with increasing daily temperatures as the growing season progresses. Larvae were also observed to shift their microhabitats by climbing on non-host vegetation and avoided excessive heat in their feeding microhabitat. Larvae of ten half-sib families from populations in south Texas and California, reared under different temperature regimes in common garden experiments, exhibited plasticity in larval phenotype, with larvae from both populations producing the red phenotype at temperatures greater than 30°C and maintaining the black phenotype at cooler temperatures. However, larvae from Texas were more tolerant of higher temperatures, showing no decrease in growth rate in the highest temperature (maximum seasonal temperature) treatment, compared to the California population. In a field experiment, black larvae were found to have higher body temperatures when exposed to sunlight compared to red larvae. These results suggest that microhabitat shifts and the color polyphenism observed in pipevine swallowtail larvae may be the adaptive strategies that enable larvae to avoid critical thermal maximum temperatures.     

Effects of hatchling body colour and rearing density on body colouration in last-stadium nymphs of the desert locust, Schistocerca gregaria

Abstract.  The influences of hatchling character and rearing density on body colour at the last-nymphal stadium are investigated for the desert locust, Schistocerca gregaria . Hatchlings are divided into five groups based on the darkness of the body colour and reared either under isolated or crowded conditions. Two types of body colour variation at the last-nymphal stadium are separately analysed (i.e. the background colour and black patterns). Under isolated conditions, the background body colour is either greenish or brownish. Most individuals are greenish and the highest percentage of brownish insects is obtained from hatchlings with the darkest body colour. Under crowded conditions, the background colour is yellow or orange and the percentage of yellowish nymphs tends to decrease when they are darker at hatching. The intensity of black patterns differs depending on the body colour at hatching and subsequent rearing density. Most isolated-reared nymphs exhibit few or no black patterns but nymphs with some black patterns also appear, particularly among those that had been dark at hatching. Under crowded conditions, the black patterns become more intense when they are darker at hatching. Therefore, last-stadium nymphs with typical solitarious or gregarious body colouration appear when they have the phase-specific body colouration at hatching as well. The present results demonstrate that both body colour at hatching and rearing density during nymphal development influence body colouration at the last-nymphal stadium.     

Variation in hydraulic architecture and gas-exchange in two desert sub-shrubs,<Emphasis Type="Italic"> Hymenoclea salsola</Emphasis> (T. &; G.) and<Emphasis Type="Italic"> Ambrosia dumosa</Emphasis> (Payne)

Adjustment of hydraulic architecture in response to environmental conditions was studied in two warm-desert sub-shrubs, Hymenoclea salsola and Ambrosia dumosa, both at the level of genetic adaptation along a climatic gradient and plastic response to immediate growth conditions. Individuals of both species originating from southern populations developed higher leaf-specific hydraulic conductance in the common greenhouse than individuals from northern populations. Hydraulic conductance was higher in plants grown at high temperature, but did not vary as a function of growth relative humidity. Hydraulic conductance was not correlated within species with individual variation in vessel diameter, cavitation vulnerability, or root:shoot ratio, but was strongly, negatively correlated with the fraction of total plant biomass allocated to leaves. For both species, stomatal conductance (g _s) at high leaf-to-air vapor pressure difference (ν) was tightly correlated with variability in hydraulic conductance, as was the sensitivity of stomatal closure to increasing ν. Experimentally increasing shoot water potential by soil pressurization, under conditions where high ν had already caused stomatal closure, led to substantial stomatal reopening in both species, but recovery was significantly higher in H. salsola. Hydraulic conductance was higher in H. salsola than A. dumosa. H.salsola also differed from A. dumosa by being a representative of a highly specialised group of desert shrubs which use the twigs as a major photosynthetic organ. The southern population of H. salsola produced far fewer leaves and relied much more heavily on twig photosynthesis than the northern population. At the whole-plant level, increased reliance on twig photosynthesis was associated with higher leaf-specific hydraulic conductance, but equivalent whole-plant photosynthesis on either a dry weight (μmol CO₂ g^–1) or nitrogen basis (μmol CO₂ g^–1)). This suggests that twig photosynthesis might be one way of increasing hydraulic conductance per unit photosynthetic canopy by increasing allocation to an organ which simultaneously performs photosynthetic, support, and transport functions. Received: 13 December 1999 / Accepted: 31 March 2000     

Selective breeding and characterization of a black mealworm strain of Tenebrio molitor Linnaeus (Coleoptera: Tenebrionidae)

Larvae of Tenebrio molitor Linnaeus are edible insects and are approved as a food ingredient in Korea. They are typically yellow; however, rare black larvae have been found in breeding boxes at insect farms. It is not clear whether black larvae represent a different species that invaded and hybridized with the yellow larvae of T. molitor or whether T. molitor shows intraspecific color variation. In this study, we characterized and identified black larvae for applications in industrial fields as well as accurate breeding and management. First, in a comparative analysis, we did not detect differences in the morphological characteristics of yellow and black larvae and adults, with the exception of larval body color. For accurate species identification, molecular analyses (p-distances and neighbor-joining) were performed based on partial COI sequences of 33 yellow and seven black larvae. Genetic divergence between yellow and black larvae ranged from 0.0% to 2.1%, revealing intraspecific variation. A neighbor-joining analysis strongly supported the classification of the two morphs as a single species. Black larvae were separated from yellow larvae and maintained by selective breeding. As a result, black larvae were completely fixed in the F2 generation (F1 = 96% and F2 = 100%). Yellow and black larvae showed no significant differences in developmental characteristics and fecundity. These findings improve our understanding of diversity within an important edible insect species and contribute to quality assurance in the food industry based on clear species identification.     

Predation and the relative importance of larval colour polymorphisms and colour polyphenism in a damselfly

Intraspecific body colour variation is common in many animal species. Predation could be a key selective agent giving rise to variation in body colour, and such variation could be due to genetics (polymorphisms) or phenotypic plasticity (polyphenisms). In this study we examined the degree of colour polymorphism and polyphenism in background colour matching in larvae of the damselfly Coenagrion armatum. In addition, we tested if predation risk is reduced when larvae are exposed to a matching compared to a non-matching background. By raising families of larvae at three different background colours we showed that polymorphism explained about 20 % of the total variation and polyphenism about 35 %. In a predation experiment with fish, we showed that larvae with a body colour matching the background had a higher survival success compared to larvae with a non-matching background colour. We suggest that the background matching is adaptive in terms of survival from predation and that colour diversity is maintained because of spatial and temporal variation in the background experienced by damselfly larvae under field conditions.     

Thermal constraints for stingless bee foragers: the importance of body size and coloration

In the dry tropics, foraging bees face significant thermal constraints as a result of high ambient temperatures and direct insolation. In order to determine the potential importance of body size and body coloration in heat gain and heat loss, passive warm-up and cooling rates were measured for freshly killed workers of 24 stingless bee species. Results accorded with biophysical principles. Small bees reached lower temperature excesses (T_exc) and warmed up and lost heat much more rapidly than larger bees. In addition to body size, body coloration had a clear effect on thermal parameters. Light-coloured bees warmed up less rapidly and had lower T_exc than dark bees. An intraspecific comparison of Melipona costaricensis and Cephalotrigona capitata colour morphs confirmed that body coloration influences thermal characteristics. This study is the first to indicate that abdominal coloration in stingless bees might be involved in the regulation of body temperature in extreme thermal conditions. However, body temperatures of foraging bees of colour morphs were not very different. This is probably due to behavioural adaptations (e.g. foraging strategies) or differences in convective and evaporative heat loss or the production of metabolic heat during flight, that all mask the effect of body colour. Notwithstanding such effects and potential thermoregulatory capabilities, stingless bees show niche differentiation and biogeographic distributions that correlate with body coloration and body size. This also suggests that, in general, light bees have an advantage over black bees in hot open lowland habitats, whereas black bees might have an advantage in wet habitats and mountains. The origin, occurrence and function of flavinism (yellow integument colouring) are discussed.     

Seasonal selection and resource dynamics in a seasonally polyphenic butterfly

Seasonal polyphenisms are widespread in nature, yet the selective pressures responsible for their evolution remain poorly understood. Previous work has largely focussed either on the developmental regulation of seasonal polyphenisms or putative ‘top‐down’ selective pressures such as predation that may have acted to drive phenotypic divergence. Much less is known about the influence of seasonal variation in resource availability or seasonal selection on optimal resource allocation. We studied seasonal variation in resource availability, uptake and allocation in Araschnia levana L., a butterfly species that exhibits a striking seasonal colour polyphenism consisting of predominantly orange ‘spring form’ adults and black‐and‐white ‘summer form’ adults. ‘Spring form’ individuals develop as larvae in the late summer, enter a pupal diapause in the fall and emerge in the spring, whereas ‘summer form’ individuals develop directly during the summer months. We find evidence for seasonal declines in host plant quality, and we identify similar reductions in resource uptake in late summer, ‘spring form’ larvae. Further, we report shifts in the body composition of diapausing ‘spring form’ pupae consistent with a physiological cost to overwintering. However, these differences do not translate into detectable differences in adult body composition. Instead, we find minor seasonal differences in adult body composition consistent with augmented flight capacity in ‘summer form’ adults. In comparison, we find much stronger signatures of sex‐specific selection on patterns of resource uptake and allocation. Our results indicate that resource dynamics in A. levana are shaped by seasonal fluctuations in host plant nutrition, climatic conditions and intraspecific interactions.     

The environmental and genetic control of seasonal polyphenism in larval color and its adaptive significance in a swallowtail butterfly

Seasonal polyphenism, in which different forms of a species are produced at different times of the year, is a common form of phenotypic plasticity among insects. Here I show that the production of dark fifth-instar caterpillars of the eastern black swallowtail butterfly, Papilio polyxenes, is a seasonal polyphenism, with larvae reared on autumnal conditions being significantly darker than larvae reared on midsummer conditions. Both rearing photoperiod and temperature were found to have individual and synergistic effects on larval darkness. Genetic analysis of variation among full-sibling families reared on combinations of two different temperatures and photoperiods is consistent with the hypothesis that variation in darkness is heritable. In addition, the genetic correlation in larval darkness across midsummer and autumnal environments is not different from zero, suggesting that differential gene expression is responsible for the increase in larval darkness in the autumn. The relatively dark autumnal form was found to have a higher body temperature in sunlight than did the lighter midsummer form, and small differences in temperature were found to increase larval growth rate. These results suggest that this genetically based seasonal polyphenism in larval color has evolved in part to increase larval growth rates in the autumn.     

Population biology and behavior of larval Eustrongylides tubifex (Nematoda: Dioctophymatida) in poikilothermous hosts

A total of 178 channel catfish (Ictalurus punctatus), 162 freshwater drum (Aplodinotus grunniens), 60 smallmouth bass (Micropterus dolomieui) and 2,488 yellow perch (Perca flavescens) were examined for larval Eustrongylides tubifex (Nitzsch 1819) J?gerskiold 1909 during 1973 and 1974. Older, large fish exhibited higher prevalence, larger mean numbers of larvae in infected fish, larger mean numbers of larvae in all fish examined, and wider range of intensity of infection. Infections were most extensive in yellow perch. The majority of larvae were removed from mesenteric cysts. Under experimental conditions, larvae migrated from cysts through the body wall when environmental temperatures reached or exceeded 40 C. Fourth-stage larvae removed from yellow perch successfully reinfected a variety of poikilothermous experimental hosts. Both young-of-the-year and I+ age/size class yellow perch exhibited increasing monthly larval worm burdens during portions of the sampling period. Older (II+) age/size class yellow perch did not exhibit significantly increasing worm burdens. No significant differences were noted in numbers of male and female larvae or in worm burdens in male and female yellow perch.     

The nature of the seasonal colour dimorphism in the scorpion fly,Panorpa japonica thunberg

The scorpion fly, Panorpa japonica, displays a seasonal colour dimorphism by changing from black to yellow in the adult state. The yellow pigment in the integument and haemolymph of the adult fly was identified as sepiapterin, while the black integument pigment was found to be melanin. After analysis of sepiapterin content by high performance liquid chromatography and determination of total haemolymph volume by [carboxyl-¹⁴C]inulin, it was shown that sepiapterin levels in the haemolymph and integument varied greatly both in the two colour types of insects and in the two sexes. Photometric analysis of melanin content showed that melanin levels correlated negatively with sepiapterin levels. These quantitative differences in sepiapterin and melanin fully explain the colour dimorphism in the insect.     

Agouti: from mouse to man, from skin to fat

The agouti protein regulates pigmentation in the mouse hair follicle producing a black hair with a subapical yellow band. Its effect on pigmentation is achieved by antagonizing the binding of alpha-melanocyte stimulating hormone (alpha-MSH) to melanocortin 1 receptor (Mc1r), switching melanin synthesis from eumelanin (black/brown) to phaeomelanin (red/yellow). Dominant mutations in the non-coding region of mouse agouti cause yellow coat colour and ectopic expression also results in obesity, type 11 diabetes, increased somatic growth and tumourigenesis. At least some of these pleiotropic effects can be explained by antagonism of other members of the melanocortin receptor family by agouti protein. The yellow coat colour is the result of agouti chronically antagonizing the binding of alpha-MSH to Mc1r and the obese phenotype results from agouti protein antagonizing the binding of alpha-MSH to Mc3r and/or Mc4r. Despite the existence of a highly homologous agouti protein in humans, agouti signal protein (ASIP), its role has yet to be defined. However it is known that human ASIP is expressed at highest levels in adipose tissue where it may antagonize one of the melanocortin receptors. The conserved nature of the agouti protein combined with the diverse phenotypic effects of agouti mutations in mouse and the different expression patterns of human and mouse agouti, suggest ASIP may play a role in human energy homeostasis and possibly human pigmentation.     

Hormonal control of larval coloration in the armyworm, Leucania separata

Leucania separata larvae show various degrees of darkening depending on the population density. A ligature applied behind the thorax of crowded or yellow solitary larvae caused black or reddish brown pigmentation in the anterior part after the larval ecdysis. Extirpation of the brain, the corpus cardiacumcorpus allatum complexes, or the suboesophageal ganglion reduced the degree of melanization in the crowded larvae, lack of the suboesophageal ganglion having a particularly striking effect. Transplantation of 3 complexes of brain-corpora cardiaca-corpora allata-suboesophageal ganglion induced intense black pigmentation in the isolated abdomens of crowded larvae and reddish brown pigmentation with some melanization in the isolated abdomens of yellow solitary larvae, though the melanization in the latter was weaker than in the former. Implantation of these organs or of the suboesophageal ganglia into yellow solitary larvae caused black and reddish brown pigmentation after a larval ecdysis. In the pieces of integument implanted into the body cavity of crowded larvae, melanization occurred after ecdysis, whereas it did not occur in most of the fragments implanted in yellow solitary larvae. Transplantation of corpora allata and other organs from solitary larvae or injection of juvenile hormone into crowded larvae did not inhibit melanization.     

Factors shaping the evolution of colour patterns in Australian agamid lizards (Agamidae): a comparative study

Identifying general patterns of adaptive coloration in animals can help to elucidate the evolutionary processes that generate them. We examined the evolution of colour patterns in Australian agamid lizards, a morphologically and ecologically diverse group that relies primarily on visual communication. We tested whether certain types of colour (yellow–reds and black) were likely to be used as sexual signals, as indicated by their association with indices of sexual selection, namely, sexual dichromatism and sexual dimorphism in body size and head shape. We then tested whether sexually dichromatic colours are associated with specific patterns (uniform, mottled, striped, blotched, reticulated) or ecological variables such as habitat openness, arboreality, and substrate type. The presence of yellow–red on lateral and ventral body regions and black on ventral body regions was significantly more common in males than females. Lateral yellow–red in males was associated with the total extent of sexual dichromatism and size dimorphism, whereas ventral yellow–red was associated with sexual dichromatism. Both lateral and ventral yellow–red were associated with uniform patterning, suggesting that sexual signals in male agamid lizards may often comprise uniform patches or flushes of yellow–red. Although ventral black coloration was more prevalent on males (i.e. strongly sexually dichromatic), it was not associated with indices of sexual selection, suggesting that, in agamid lizards, yellow–red coloration is more likely to be sexually selected than black. Sexually dichromatic coloration was not strongly associated with any of the ecological variables measured. We found some associations, however, between female dorsal patterns and ecological variables, suggesting that female patterns are influenced by natural selection. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109 , 101–112.     

Tryptophan, copper and zinc in hair of healthy subjects. Correlation with differences in hair pigmentation

Tryptophan, copper and zinc levels were determined in the hair of 300 healthy subjects divided by sex, age and hair colour. Sex influences tryptophan content in hair, the levels of this amino acid being higher in males than in females. Tryptophan is also higher in infancy (2-5 years) and in both males and females aging around 80 years and over. Hair colour also influences tryptophan levels, which increase from fair to black hair. Copper levels are similar in hair of both males and females, while those of zinc are higher in women. Age influences the distribution of these two metals in human hair. Copper contents in hair of males are higher at the age 20-40 years. In females, values decrease over the age of 60 years. Instead, zinc levels are higher between 20 and 60 years in males, and between 13 and 19 years in females. As regards hair colour, copper is slightly higher in black hair in males and in fair hair in females, and lower in white hair in both sexes. Zinc values appear to be higher in red and lower in white hair in males. In females they are higher in black hair.     

Highly‐enhanced larval growth during the cold season mediated by the basking behavior of the butterfly Parnassius citrinarius (Lepidoptera: Papilionidae)

Some insect species are thought to grow quickly, even in low temperatures under natural conditions, presumably by conducting basking behaviors to use sunlight. However, whether basking behavior in fact enhances developmental speed and shortens the larval period in the field has not been determined. Moreover, few studies have examined whether basking is behavioral thermoregulation or simply the result of highly‐heterogeneous heat environments in the field. To examine these issues, we conducted field observations and laboratory experiments using larvae of Parnassius citrinarius Motschulsky, which mature within a short period after the thaw in early spring. First, body temperatures of larvae were measured under sunny and cloudy conditions. Second, larval preference for warmer locations was examined. Finally, we compared the developmental speed of larvae when they basked under field conditions and when did not bask in laboratory conditions under different air temperature regimes. Under sunny conditions, larval body temperature was substantially higher than either the temperature of the host plant or the air temperature, and was equivalent to the temperature of dead leaves, which the larvae used as basking sites. In contrast, no such tendency was observed under cloudy conditions. Larvae exhibited an exclusive preference for warmer locations. Moreover, in the field, despite the low ambient temperature, larvae grew much faster than those reared in the laboratory. These results imply that the basking behavior of P. citrinarius larvae is active thermoregulation to maintain high body temperatures in the cold season.     

我国鼬獾的亚种分类及一新亚种的描述

鼬獾(Melogale moschata)主要分布于我国华东、华南、中南、西南等广大地区。在我国的分布区大约在东经97°-123°,北纬18°-32°之间。     

Inheritance of colour and coat in the Belgian Shepherd dog

The several colours and coats of the Belgian Shepherd dog are shown to be due primary to combinations of the following genes: dominant black (A ^s ), dominant yellow (A ^y ), chinchilla (ch), long hair (l) and wire hair (Wh). The gene for black and tan (a ^t ) is or has been present in the breed. All of the dominant yellow dogs exhibit a black facial mask and extensive suffusion of black guard hairs on the body.     

Moving south: effects of water temperatures on the larval development of invasive cane toads (Rhinella marina) in cool‐temperate Australia

The distributional limits of many ectothermic species are set by thermal tolerances of early‐developmental stages in the life history; embryos and larvae often are less able to buffer environmental variation than are conspecific adults. In pond‐breeding amphibians, for example, cold water may constrain viability of eggs and larvae, even if adults can find suitable thermal conditions in terrestrial niches. Invasive species provide robust model systems for exploring these questions, because we can quantify thermal challenges at the expanding range edge (from field surveys) and larval responses to thermal conditions (in the laboratory). Our studies on invasive cane toads (Rhinella marina) at the southern (cool‐climate) edge of their expanding range in Australia show that available ponds often average around 20°C during the breeding period, 10°C lower than in many areas of the toads’ native range, or in the Australian tropics. Our laboratory experiments showed that cane toad eggs and larvae cannot develop successfully at 16°C, but hatching success and larval survival rates were higher at 20°C than in warmer conditions. Lower temperatures slowed growth rates, increasing the duration of tadpole life, but also increased metamorph body mass. Water temperature also influenced metamorph body shape (high temperatures reduced relative limb length, head width, and body mass) and locomotor performance (increased speed from intermediate temperatures, longer hops from high temperatures). In combination with previous studies, our data suggest that lower water temperatures may enhance rather than reduce recruitment of cane toads, at least in areas where pond temperatures reach or exceed 20°C. That condition is fulfilled over a wide area of southern Australia, suggesting that the continuing expansion of this invasive species is unlikely to be curtailed by the impacts of relatively low water temperatures on the viability of early life‐history stages.