Desiccation resistance in four Drosophila species: sex and population effects

Desiccation resistance and body mass were measured in multiple populations of each of four species of Drosophila: two desert endemic species (D. nigrospiracula and D. mojavensis), and two with more widespread distributions (D. melanogaster and D. pseudoobscura). While flies from the desert species were more desiccation tolerant, there was, in certain cases, significant variation in desiccation resistance among populations of the same species. A significant difference in desiccation resistance was observed between the sexes, females were more resistant than males, but this relationship was reversed when taking into account body mass differences between the sexes. The degree of observed within-species variability demonstrates that studies focusing upon differences between species can produce different conclusions if they rely on observations for only single populations of a given species. Our data also suggest the existence of multiple mechanisms for desiccation resistance.     

Divergent strategies for adaptation to desiccation stress in two Drosophila species of immigrans group

Water balance mechanisms have been investigated in desert Drosophila species of the subgenus Drosophila from North America, but changes in mesic species of subgenus Drosophila from other continents have received lesser attention. We found divergent strategies for coping with desiccation stress in two species of immigrans group--D. immigrans and D. nasuta. In contrast to clinal variation for body melanization in D. immigrans, cuticular lipid mass showed a positive cline in D. nasuta across a latitudinal transect (10°46'-31°43'N). Based on isofemale lines variability, body melanization showed positive correlation with desiccation resistance in D. immigrans but not in D. nasuta. The use of organic solvents has supported water proofing role of cuticular lipids in D. nasuta but not in D. immigrans. A comparative analysis of water budget of these two species showed that higher water content, reduced rate of water loss and greater dehydration tolerance confer higher desiccation resistance in D. immigrans while the reduced rate of water loss is the only possible mechanism to enhance desiccation tolerance in D. nasuta. We found that carbohydrates act as metabolic fuel during desiccation stress in both the species, whereas their rates of utilization differ significantly between these two species. Further, acclimation to dehydration stress improved desiccation resistance due to increase in the level of carbohydrates in D. immigrans but not in D. nasuta. Thus, populations of D. immigrans and D. nasuta have evolved different water balance mechanisms under shared environmental conditions. Multiple measures of desiccation resistance in D. immigrans but reduction in water loss in D. nasuta are consistent with their different levels of adaptive responses to wet and dry conditions on the Indian subcontinent.     

Quantitative genetic analysis suggests causal association between cuticular hydrocarbon composition and desiccation survival in Drosophila melanogaster

Survival to low relative humidity is a complex adaptation, and many repeated instances of evolution to desiccation have been observed among Drosophila populations and species. One general mechanism for desiccation resistance is Cuticular Hydrocarbon (CHC) melting point. We performed the first Quantitative Trait Locus (QTL) map of population level genetic variation in desiccation resistance in D. melanogaster. Using a panel of Recombinant Inbred Lines (RILs) derived from a single natural population, we mapped QTL in both sexes throughout the genome. We found that in both sexes, CHCs correlated strongly with desiccation resistance. At most desiccation resistance loci there was a significant association between CHCs and desiccation resistance of the sort predicted from clinal patterns of CHC variation and biochemical properties of lipids. This association was much stronger in females than males, perhaps because of greater overall abundance of CHCs in females, or due to correlations between CHCs used for waterproofing and sexual signalling in males. CHC evolution may be a common mechanism for desiccation resistance in D. melanogaster. It will be interesting to compare patterns of CHC variation and desiccation resistance in species which adapt to desiccation, and rainforest restricted species which cannot.     

Changes in cuticular lipids, water loss and desiccation resistance in a tropical drosophilid: analysis of variation between and within populations

We investigated within as well as between population variability in desiccation resistance, cuticular lipid mass per fly and cuticular water loss in nine geographical populations of a tropical drosophilid, Zaprionus indianus. Interestingly, the amount of cuticular lipids and desiccation resistance in this non-melanic species are significantly higher as compared with melanic Drosophila melanogaster. On the basis of isofemale line analysis, within population trait variability in cuticular lipid mass per fly is positively correlated with desiccation resistance and negatively correlated with cuticular water loss but show lack of correlation with body size. We observed geographical variation in the amount of cuticular lipid mass per fly in Zaprionus indianus but no such divergence was found in D.melanogaster. In both the species, geographical variations in desiccation resistance are negatively correlated with cuticular water loss but the underlying mechanisms for changes in cuticular permeability are quite different. Thus, we may suggest that body melanisation and cuticular lipids may represent alternative strategies for coping with dehydration stress in melanic versus non-melanic drosophilids. For both the species, desiccation resistance and cuticular water loss are correlated with regular increase in aridity in the northern subtropical localities as compared with southern peninsular humid tropical localities. The role of climatic selection is evident from multiple regression analysis with seasonal changes in temperature and humidity (Tcv and RHcv) of the sites of origin of populations of Zaprionus indianus along latitude.     

Intraspecific variation in resistance to desiccation and climatic gradients in the distribution of the bush-dwelling land snail Trochoidea simulata

Resistance to desiccation was examined in six populations of the Israeli bush-dwelling snail Trochoidea simulata , a desert species distributed mainly between the 100–200 mm isohyets.
The present study revealed significant intraspecific differences in resistance to desiccation which are correlated with habitat and climatic gradients within the distribution range of the species. Populations from more arid sites were more resistant to desiccation and heat exposure than those from more mesic areas. However, the population from the Rift Valley (an extremely arid region) was surprisingly poorly resistant. Rates of population water loss under the controlled experimental conditions in the laboratory generally matched the calculated water losses during natural summer aestivation.     

Impact of body melanisation on contrasting levels of desiccation resistance in a circumtropical and a generalist <Emphasis Type="Italic">Drosophila</Emphasis> species

We investigated the role of cuticular lipids, body melanisation and body size in conferring contrasting levels of desiccation resistance in latitudinal populations of Drosophila melanogaster and Drosophila ananassae on the Indian subcontinent. Contrary to the well known role of cuticular lipids in water proofing in diverse insect taxa, there is lack of geographical variations in the amount of cuticular lipids per fly in both the species. In D. ananassae, quite low levels of body melanisation are correlated with lower desiccation resistance. By contrast, increased levels of desiccation resistance are correlated with quite high melanisation in D. melanogaster. Thus, species specific cuticular melanisation patterns are significantly correlated with varying levels of desiccation resistance within as well as between populations and across species. Role of body melanisation in desiccation resistance is further supported by the fact that assorted dark and light flies differ significantly in cuticular water loss, hemolymph and dehydration tolerance. However, similar patterns of body size variation do not account for contrasting levels of desiccation resistance in these two Drosophila species. Climatic selection is evidenced by multiple regression analysis with seasonal amplitude of thermal and humidity changes (Tcv and RHcv) along latitude on the Indian subcontinent. Finally, the contrasting levels of species specific distribution patterns are negatively correlated with RHcv of sites of origin of populations i.e. a steeper negative slope for D. ananassae corresponds with its desiccation sensitivity as compared with D. melanogaster. Thus, evolutionary changes in body melanisation impact desiccation resistance potential as well as distribution patterns of these two Drosophila species on the Indian subcontinent.     

Changes in body melanisation and desiccation resistance in highland vs. lowland populations of D. melanogaster

Wild caught samples of Drosophila melanogaster from five highland localities showed parallel changes in melanisation and desiccation resistance in darker versus lighter phenotypes, i.e. darker flies (>45% melanisation) showed significantly higher desiccation resistance than lighter flies (<30% melanisation). In order to find an association between body melanisation and desiccation resistance, highland and lowland populations from tropical and subtropical regions (11.15-31.06 degrees N) of the Indian subcontinent were raised and investigated at 21 degrees C for four physiological traits, i.e. per cent body melanisation, desiccation resistance, rate of water loss and rate of water absorption. On the basis of mother-offspring regression, body melanisation and desiccation resistance showed higher heritability (0.58-0.68) and thus these traits are suitable for laboratory analyses. Significantly higher melanisation as well as desiccation resistance were observed in highland populations as compared with lowland populations. The rates of water loss as well as absorption were negatively correlated with body melanisation, i.e. darker flies from highlands showed a reduced rate of water loss as well as a lower rate of water absorption while the reverse trend was observed in lighter flies from lowlands. On the basis of multiple regressions, significant effects due to combined altitude and latitude were observed for all the four physiological traits. Local climatic conditions (i.e. annual average temperature and relative humidity) helped in explaining parallel changes in body melanisation and desiccation resistance in D. melanogaster.     

Sexual conflict and environmental change: trade-offs within and between the sexes during the evolution of desiccation resistance

Intralocus sexual conflict occurs when males and females experience sex-specific selection on a shared genome. With several notable exceptions, intralocus sexual conflict has been investigated in constant environments to which the study organisms have had an opportunity to adapt. However, a change in the environment can result in differential or even opposing selection pressures on males and females, creating sexual conflict. We used experimental evolution to explore the interaction between intralocus sexual conflict, sexual dimorphism and environmental variation in Drosophila melanogaster. Six populations were selected for adult desiccation resistance (D), with six matched control populations maintained in parallel (C). After 46 generations, the D populations had increased in survival time under arid conditions by 68% and in body weight by 20% compared to the C populations. The increase in size was the result of both extended development and faster growth rate of D juveniles. Adaptation to the stress came at a cost in terms of preadult viability and female fecundity. Because males are innately less tolerant of desiccation stress, very few D males survived desiccation-selection; while potentially a windfall for survivors, these conditions mean that most males’ fitness was determined posthumously. We conjectured that selection for early maturation and mating in males was in conflict with selection for survival and later reproduction in females. Consistent with this prediction, the sexes showed different patterns of age-specific desiccation resistance and resource acquisition, and there was a trend towards increasingly female-biased sexual size dimorphism. However, levels of desiccation resistance were unaffected, with D males and females increasing in parallel. Either there is a strong positive genetic correlation between the sexes that limits independent evolution of desiccation resistance, or fitness pay-offs from the strategy of riding out the stress bout are great enough to sustain concordant selection on the two sexes. We discuss the forces that mould fitness in males under a regimen where trade-offs between survival and reproduction may be considerable.     

Desiccation resistance in interspecific Drosophila crosses. Genetic interactions and trait correlations

We used crosses between two closely related Drosophila species, Drosophila serrata and D. birchii, to examine the genetic basis of desiccation resistance and correlations between resistance, physiological traits, and life-history traits. D. serrata is more resistant to desiccation than D. birchii, and this may help to explain the broader geographical range of the former species. A comparison of F2's from reciprocal crosses indicated higher resistance levels when F2's originated from D. birchii mothers compared to D. serrata mothers. However, backcrosses had a resistance level similar to that of the parental species, suggesting an interaction between X-linked effects in D. serrata that reduce resistance and autosomal effects that increase resistance. Reciprocal differences persisted in hybrid lines set up from the different reciprocal crosses and tested at later generations. Increased desiccation resistance was associated with an increased body size in two sets of hybrid lines and in half-sib groups set up from the F4's after crossing the two species, but size associations were inconsistent in the F2's. None of the crosses provided evidence for a positive association between desiccation resistance and glycogen levels, or evidence for a tradeoff between desiccation resistance and early fecundity. However, fecundity was positively correlated with body size at both the genetic and phenotypic levels. This study illustrates how interspecific crosses may provide information on genetic interactions between traits following adaptive divergence, as well as on the genetic basis of the traits.     

Divergence of water balance mechanisms in two melanic Drosophila species from the western Himalayas

Drosophila busckii is more abundant under colder and drier montane habitats in the western Himalayas as compared to Drosophila melanogaster but the mechanistic basis of such climatic adaptations is largely unknown. We tested the hypothesis whether genetic variation or phenotypic plasticity of cuticular traits confer adaptive protection against desiccation stress in two melanic Drosophila species living under drier montane localities. For D. melanogaster, changes in melanisation are known to be associated with reduced water loss but there are no data on D. busckii. We investigated changes in body melanisation, cuticular lipids, desiccation resistance, water loss, extractable hemolymph volume (%), and dehydration tolerance in six sympatric populations of D. busckii and D. melanogaster over an altitudinal range of 640-2236 m. D. busckii is a melanic species but changes in cuticular water loss are negatively correlated with cuticular lipid mass and not with body melanisation. In D. melanogaster, there are no plastic effects (14-28 °C) for cuticular lipid mass but variation in body melanisation is associated with desiccation-related traits. Effects of organic solvents (hexane or chloroform: methanol), developmental plasticity and seasonal variation in cuticular lipids affect body water loss in D. busckii but no such changes occur in D. melanogaster. Thus, sympatric populations of D. busckii and D. melanogaster have evolved different water balance mechanisms under shared environmental conditions in the western Himalayas. Multiple measures of desiccation resistance in these species show clinal variation with altitude, consistent with adaptation to increased desiccation stress.     

The relation between body size and resistance to desiccation in two species of Zaprionus (Drosophilidae)

Abstract.

• 1 Resistance to desiccation and body size were studied in the drosophilid flies Zaprionus vittiger and Z.tuberculatus.
• 2 Populations in a hot dry low altitude area were compared with those in a nearby cooler wetter high altitude area in the north-eastern Transvaal of South Africa, using laboratory strains established from these populations.
• 3 No between-area differences were found for either body size or resistance to desiccation considered separately.
• 4 However, in Z.tuberculatus, regression analyses using strain mean values showed a strong positive correlation between the two characters amongst strains derived from low altitude populations but not amongst strains derived from high altitude populations.
• 5 It is concluded that differences of genetic organization have evolved between low and high altitude populations of Z.tuberculutus.
• 6 From differences between species and sexes it is concluded that both body size and some unknown factor related to sex may influence resistance of desiccation.

     

Desiccation resistance in arboreal and terrestrial ants

ABSTRACT Arboreal and terrestrial ants were exposed to 0, 25, 50, 75 and 100 (control)% r.h., at 30^oC. Desiccation resistance increased with body size (as dry weight^0.55), but not as quickly as expected from the consequences of the surface area and volume relationship (as dry weight^0.67). Arboreal ants took 8 times longer to die than terrestrial ants of comparable size. Even after size effects were removed, desiccation resistance differed between various terrestrial species and showed a correlation with foraging patterns.
Arboreal and terrestrial ants whose waterproofing epicuticular lipids were removed by chloroform: methanol extraction had equally high water loss rates at 0% r.h. Unextracted arboreal ants had water loss rates half those of unextracted terrestrial ants, suggesting that differences between them were based on differences in epicuticular lipids. The lower water loss rates of arboreal ants contributed significantly to their longer survival under desiccation. Arboreal ants also had greater total rectal pad area than terrestrial ants, suggesting that they may be able to reclaim faecal water more effectively. There were no differences in the minimum viable water content between the two groups of ants. Both had water loss tolerances comparable with those of arthropods adapted to xeric environments. Initial water loss rates could not account for all of the differences in desiccation resistance between arboreal and terrestrial ants. Other adaptations to desiccation stress by arboreal ants are likely.
Comparisons of water loss rates and desiccation resistance between arboreal and desert ants suggest that the arboreal habitat is at least as stressful as the desert habitat.     

Adaptive associations between total body color dimorphism and climatic stress‐related traits in a stenothermal circumtropical Drosophila species

Abstract Low desiccation resistance of Drosophila ananassae reflects its rarity outside the humid tropics. However, the ability of this sensitive species to evolve under seasonally varying subtropical areas is largely unknown. D. ananassae flies are mostly lighter during the rainy season but darker and lighter flies occur in the autumn season in northern India. We tested the hypothesis whether seasonally varying alternative body color phenotypes of D. ananassae vary in their levels of environmental stress tolerances and mating behavior. Thus, we investigated D. ananassae flies collected during rainy and autumn seasons for changes in body melanization and their genetic basis, desiccation‐related traits, cold tolerance and mating propensity. On the basis of genetic crosses, we found total body color dimorphism consistent with a single gene model in both sexes of D. ananassae. A significant increase in the frequency of the dark morph was observed during the drier autumn season, and body color phenotypes showed significant deviations from Hardy‐Weinberg equilibrium, which suggests climatic selection plays a role. Resistance to desiccation as well as cold stress were two‐ to three‐fold higher in the dark body color strain as compared with the light strain. On the basis of no‐choice mating experiments, we observed significantly higher assortative matings between dark morphs under desiccation or cold stress, and between light morphs under hot or higher humidity conditions. To the best of our knowledge, this is the first report on the ecological significance of seasonally varying total body color dimorphism in a tropical species, D. ananassae.     

Water balance in desert Drosophila: lessons from non-charismatic microfauna

Water stress is a particularly important problem for insects and other small organisms in arid environments. Cactophilic fruit flies in the genus Drosophila have invaded deserts on numerous occasions, including multiple independent invasions of North American deserts. Because the evolutionary history of this genus is so well studied, we can investigate the mechanisms of adaptation in a rigorous phylogenetic context. As expected, desert fruit flies lose water less rapidly than their mesic congeners. They are also able to tolerate the loss of a greater percentage of body water, but this difference is mainly due to phylogenetic history, and does not represent an adaptation specifically to desert habitats. A laboratory analogue of desert Drosophila is provided by populations of D. melanogaster that have been subjected to selection for desiccation resistance. Selected populations resemble desert species in that they lose water slowly, relative to control populations, and are not more tolerant of dehydration stress. They differ, however, in having much higher water contents and different behavioral responses to desiccating conditions. Our comparisons of laboratory and natural populations reveal that not all possible adaptive mechanisms evolve in stressful environments. Different physiological and behavioral strategies may evolve depending upon the particular options available in the environment.     

Very low additive genetic variance and evolutionary potential in multiple populations of two rainforest Drosophila species

Most quantitative traits are thought to exhibit high levels of genetic variance and evolutionary potential. However, this conclusion may be biased by a lack of studies on nonmodel organisms and may not generalize to restricted species. A recent study on a single, southern population of the rainforest-restricted Drosophila birchii failed to find significant additive genetic variance for the desiccation resistance trait; however, it is unclear whether this pattern extends to other D. birchii populations or to other rainforest species. Here we use an animal model design to show very low levels of additive genetic variance for desiccation resistance in multiple populations of two highly sensitive rainforest species of Drosophila from tropical northeastern Australia. In contrast, relatively high levels of genetic variance were found for morphological traits in all populations of the species tested. This indicates limited evolutionary potential for evolving increased desiccation resistance in these rainforest restricted species.     

Starvation resistance is positively correlated with body lipid proportion in five wild caught Drosophila simulans populations

Stress resistance traits in Drosophila often show clinal variation, suggesting that selection affects resistance traits either directly or indirectly. One of the most common causes of stress for animals is the shortage or suboptimal quality of food, and individuals within many species must survive periods of starvation or exposure to nutritionally imbalanced diets. This study determines the relationship between starvation resistance, body lipid content, and lifespan in five recently collected Drosophila simulans populations from four distinct geographic localities. Despite rearing under standard nutritional conditions, we observed significant differences in starvation resistance between sexes and between localities. If body lipid proportion is included as a covariate in statistical analysis the difference between the sexes remains (slopes are parallel, with males more susceptible than females to starvation across all lipid proportions) but the effect of locality disappears. This result suggests that flies from different localities differ in their susceptibility to starvation because of differences in their propensity to store body lipid. We observed a negative relationship between lifespan and starvation resistance in both males and females, suggesting a fitness cost to increasing lipid reserves. These data raise issues about the role of diet in maintaining life history trait variation within and among populations. In conclusion, we show many similarities and surprising differences in life history traits between D. simulans and Drosophila melanogaster.     

Adaptations to environmental stress in altitudinal populations of two Drosophila species

Abstract.  Opposite clinal variation for desiccation and starvation tolerance are observed in four altitudinal populations (219–2202 m), each of two sympatric and cold adapted species: Drosophila takahashii and Drosophila nepalensis from northern India. The high-altitude populations are more tolerant to desiccation than those from lower altitudes, whereas the reverse trend occurs for starvation tolerance. The magnitude of tolerances are significantly high in D. nepalensis, which is better adapted to cold conditions. During winter months (November to February), there are significant decreases in T _max, T _min and relative humidity along the altitudinal transect. Higher desiccation resistance can develop under cold conditions over short-range, altitudinally varying, geographical areas (250 km) compared with our previously reported long-range (>2000 km), latitudinal variations under tropical climatic conditions. However, significant starvation tolerances are favoured by small body size, higher dispersal rate and higher ambient temperature of the site of origin of populations. Significant correlations of two climatic factors (the mean monthly coefficients of variation of temperature and relative humidity) with these two physiological traits can best explain the observed altitudinal clinal variations under natural conditions.     

Variation in adult life history and stress resistance across five species of<Emphasis Type="Italic">Drosophila</Emphasis>

Dry weight at eclosion, adult lifespan, lifetime fecundity, lipid and carbohydrate content at eclosion, and starvation and desiccation resistance at eclosion were assayed on a long-term laboratory population ofDrosophila melanogaster, and one recently wild-caught population each of four other species ofDrosophila, two from themelanogaster and two from theimmigrans species group. The relationships among trait means across the five species did not conform to expectations based on correlations among these traits inferred from selection studies onD. melanogaster. In particular, the expected positive relationships between fecundity and size/lipid content, lipid content and starvation resistance, carbohydrate (glycogen) content and desiccation resistance, and the expected negative relationship between lifespan and fecundity were not observed. Most traits were strongly positively correlated between sexes across species, except for fractional lipid content and starvation resistance per microgram lipid. For most traits, there was evidence for significant sexual dimorphism but the degree of dimorphism did not vary across species except in the case of adult lifespan, starvation resistance per microgram lipid, and desiccation resistance per microgram carbohydrate. Overall,D. nasuta nasuta andD. sulfurigaster neonasuta (immigrans group) were heavier at eclosion than themelanogaster group species, and tended to have somewhat higher absolute lipid content and starvation resistance. Yet, these twoimmigrans group species were shorter-lived and had lower average daily fecundity than themelanogaster group species. The smallest species,D. malerkotliana (melanogaster group), had relatively high daily fecundity, intermediate lifespan and high fractional lipid content, especially in females.D. ananassae (melanogaster group) had the highest absolute and fractional carbohydrate content, but its desiccation resistance per microgram carbohydrate was the lowest among the five species. In terms of overall performance, the laboratory population ofD. melanogaster was clearly superior, under laboratory conditions, to the other four species if adult lifespan, lifetime fecundity, average daily fecundity, and absolute starvation and desiccation resistance are considered. This finding is contrary to several recent reports of substantially higher adult lifespan and stress resistance in recently wild-caught flies, relative to flies maintained for a long time in discretegeneration laboratory cultures. Possible explanations for these apparent anomalies are discussed in the context of the differing selection pressures likely to be experienced byDrosophila populations in laboratory versus wild environments. This paper is dedicated to the memory of our friend and former colleague Dr Hans Raj Negi, who tragically passed away at a very young age in a road accident in November 2003.     

Desiccation resistance along an aridity gradient in the cactophilic fly Drosophila buzzatii: sex-specific responses to stress

Stress resistance characters are valuable tools for the study of acclimation potential, adaptive strategies and biogeographic patterns in species exposed to environmental variability. Water stress is a challenge to terrestrial arthropods because of their small size and relatively high area: volume ratio. Fruit flies have been investigated to record adaptive morphological and physiological traits, as well as to test their responses to stressful factors. In this study, we investigate the ability to cope with water stress, by examining variation in desiccation resistance in a species that lives mainly in desert lands. Specifically, we explored the genetic and ecological basis of desiccation resistance in populations of Drosophila buzzatii from Northern Argentina. We used a common garden experiment with desiccation treatments on a number of isofemale lines from four populations along an aridity gradient. Our results revealed significant among-population differentiation and substantial amounts of genetic variation for desiccation resistance. We also detected significant genotype-by-environment and genotype-by-sex interactions indicative that desiccation resistance responses of the lines assayed were environment- and sex-specific. In addition, we observed clinal variation in female desiccation resistance along gradients of altitude, temperature and humidity; that desiccation resistance is a sexually dimorphic trait, and that sexual dimorphism increased along the aridity and altitudinal gradients. Based on current evidence, we propose that the observed sex-specific responses may reflect different life history traits, and survival and reproductive strategies in different ecological scenarios.     

Sexual dimorphism for water balance mechanisms in montane populations of Drosophila kikkawai

Conservation of water is critical to the ecological success of Drosophila species living in the drier montane localities of the Western Himalayas. We observed clinal variation in desiccation resistance for both sexes of Drosophila kikkawai from an altitudinal transect (512–2226 m above sea level). Since more than 90 per cent of body water is lost through cuticular transpiration, the target of selection may be cuticular lipids or cuticular melanization. We tested whether melanic females and non-melanic males of D. kikkawai have similar mechanisms of desiccation resistance. There is clinal variation in the amount of cuticular lipids per fly in males, but not in females. By contrast, for females, elevational increase in melanization is positively correlated with desiccation resistance and negatively with cuticular water loss, but there is no variation in the amount of cuticular lipids. Thus, sexual dimorphism for the mechanism of desiccation resistance in D. kikkawai matches the water proofing role of body melanization as well as cuticular lipids.