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Surface sculpturing and water retention of elephant skin

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Abstract

The integument of elephants is highly sculptured with wrinkles and crevices arranged in prominent geometric patterns. These features are shown to adsorb water and to facilitate its movement over the body surface. The retention of water attributable to epidermal morphology was quantified by studying latex casts of integumentary surfaces. Retention of water by casts of integument is4–5 to 10 times greater than that of flat surfaces and is greater in African elephants than in Asian elephants. Both species lack sebum and sweat glands and require regular wetting of their skin. However, the skin of African elephants is sculptured more deeply and retains significantly more water than does that of Asian elephants adapted to more mesic habitats. We propose that the highly sculptured morphology functions to enhance retention of surface moisture during periodic wallowing, thereby impeding dehydration of the exposed epidermis and mediating evaporative heat losses. These functions could have great physiological significance during periods of drought when intense heat and solar radiation coincide with limited availability of water.

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... There are numerous studies investigating the adaptations in nature to limited resources. Some reptiles, amphibians, arthropods, birds and even mammals have been found to survive restrictions on water supply by using their body surface to collect water from various sources (Louw, 1972;Rijke, 1972;Lillywhite and Licht, 1974;Gans et al., 1982;Lillywhite and Stein, 1987;Sherbrooke, 1990;Cardwell, 2006;Tracy et al., 2011). Collecting water in arid environments might appear to be contradictory at first, but nevertheless many such areas are known to provide water sources. ...
... In general, the need for water collection is often for rehydration, but it is also needed for water adsorption, which prevents dehydration of the skin (Lillywhite and Licht, 1974). Furthermore, collected water serves the thermoregulation in elephants and wharf roaches (Hoese, 1981;Lillywhite and Stein, 1987), is transported by adult sandgrouse from water sources to hydrate the young (Cade and MacLean, 1967), and yields reduced reflectivity for camouflage in flat bugs (Silberglied and Aiello, 1980;Hischen et al., 2017). ...
... Water penetration into surface structures with moderate chemical hydrophilicity can cover greater areas than are possible by spreading on a smooth surface (Quéré, 2008). Such water penetration has been found, for example, in toads (Lillywhite and Licht, 1974), elephants (Lillywhite and Stein, 1987) and flat bugs . ...
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Several mechanisms of water acquisition have evolved in animals living in arid habitats to cope with limited water supply. They enable access to water sources such as rain, dew, thermally facilitated condensation on the skin, fog, or moisture from a damp substrate. This Review describes how a significant number of animals - in excess of 39 species from 24 genera - have acquired the ability to passively collect water with their integument. This ability results from chemical and structural properties of the integument, which, in each species, facilitate one or more of six basic mechanisms: increased surface wettability, increased spreading area, transport of water over relatively large distances, accumulation and storage of collected water, condensation, and utilization of gravity. Details are described for each basic mechanism. The potential for bio-inspired improvement of technical applications has been demonstrated in many cases, in particular for several wetting phenomena, fog collection and passive, directional transport of liquids. Also considered here are potential applications in the fields of water supply, lubrication, heat exchangers, microfluidics and hygiene products. These present opportunities for innovations, not only in product functionality, but also for fabrication processes, where resources and environmental impact can be reduced.
... The influence of surface water in particular has received marked attention (; de Beer and van Aarde, 2008; Epaphras et al., 2008; Gaylard et al., 2003; Redfern et al., 2003; Shannon et al., 2009; Smit et al., 2007) because elephants are recognized as water dependent (Western, 1975; Western and Lindsay, 1984); therefore, surface water management may be a powerful tool for mitigating problems associated with localized overabundance of elephants, particularly in small reserves ( Smit et al., 2007). Heat dissipation has long been recognized as a challenge for these large mammals (Benedict, 1936; Lillywhite and Stein, 1987; Phillips and Heath, 1992; Williams, 1990; Wright, 1984; Wright and Luck, 1984) and reliance on evaporative cooling is hypothesized to contribute to the elephant's dependence on water (Wright and Luck, 1984). Thus, the interaction between two abiotic factors, temperature and the distribution of surface water, is likely an important driver of landscape use by elephants. ...
... Previous investigations have recognized the importance of behavioral thermoregulation such as shade seeking and dust bathing (Rees, 2002; Sikes, 1971), as well as the potential role for heat storage or heterothermy (Kinahan et al., 2007; Weissenböck et al., 2011), to how elephants maintain thermal balance in warm climates. Wright and Luck (Wright and Luck, 1984) and Lillywhite and Stein (Lillywhite and Stein, 1987) also recognized that evaporative cooling may be an important component ...
... The suggested functions of mud and dust bathing range from sun protection to protection from insects to thermoregulatory benefits (Rees, 2002; Sikes, 1971). Lillywhite and Stein (Lillywhite and Stein, 1987) found that the highly sculptured surface of the skin enhances the adherence of mud and water for up to 26h and hypothesized that water and mud would protect the skin from solar radiation and enhance evaporative cooling. Lillywhite and Stein (Lillywhite and Stein, 1987) also noted that African elephants, who are larger and generally live in more arid conditions, seemed to have more significant sculpturing compared with Asian elephants, which may further enhance adherence of surface water and evaporative cooling in this species. ...
Article
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Elephant movement patterns in relation to surface water demonstrate that they are a water-dependent species. Thus, there has been interest in using surface water management to mitigate problems associated with localized elephant overabundance. However, the physiological mechanisms underlying the elephant's water dependence remain unclear. Although thermoregulation is likely an important driver, the relationship between thermoregulation, water use and climate has not been quantified. We measured skin surface temperature of and cutaneous water loss from 13 elephants (seven African, 3768±642 kg; six Asian, 3834±498 kg) and determined the contribution of evaporative cooling to their thermal and water budgets across a range of air temperatures (8-33°C). We also measured respiratory evaporative water loss and resting metabolic heat production on a subset of elephants (N=7). The rate of cutaneous evaporative water loss ranged between 0.31 and 8.9 g min(-1) m(-2) for Asian elephants and 0.26 and 6.5 g min(-1) m(-2) for African elephants. Simulated thermal and water budgets using climate data from Port Elizabeth, South Africa, and Okaukuejo, Namibia, suggested that the 24-h evaporative cooling water debt incurred in warm climates can be more than 4.5 times that incurred in mesic climates. This study confirms elephants are obligate evaporative coolers but suggests that classification of elephants as water dependent is insufficient given the importance of climate in determining the magnitude of this dependence. These data highlight the potential for a physiological modeling approach to predicting the utility of surface water management for specific populations.
... Evaporative heat loss, E, has both skin, E r , and respiratory, E b , components (Robertshaw, 2006). Asian elephants may increase skin evaporative heat loss by wallowing and bathing (Lillywhite and Stein, 1987), but not by sweating, as the only sweat gland identified in Asian elephants is located interdigitally (Lamps et al., 2001). Therefore, E r is assumed to be negligible, as the elephants were dry at the start of the trials. ...
... We estimate that choosing nocturnal activity, in the absence of solar radiation, would relax the thermoregulatory constraints on activity in endothermic gigantotherms and allow elephants approximately 7 to 8h of continuous locomotion before the onset of lethal core body temperature (Fig.6A). In addition, because bathing and wallowing are the only means available to increase evaporative heat loss (Lillywhite and Stein, 1987), migratory routes in elephants are in often in close proximity to water (Lindeque and Lindeque, 1991; Tchamba, 1993; Joshi, 2009). Immediately following exercise events in hot conditions, one of the elephants, Panya, often chose to enter the pool and remain partially submerged for several hours (Fig.7). ...
Article
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Gigantic size presents both opportunities and challenges in thermoregulation. Allometric scaling relationships suggest that gigantic animals have difficulty dissipating metabolic heat. Large body size permits the maintenance of fairly constant core body temperatures in ectothermic animals by means of gigantothermy. Conversely, gigantothermy combined with endothermic metabolic rate and activity likely results in heat production rates that exceed heat loss rates. In tropical environments, it has been suggested that a substantial rate of heat storage might result in a potentially lethal rise in core body temperature in both elephants and endothermic dinosaurs. However, the behavioral choice of nocturnal activity might reduce heat storage. We sought to test the hypothesis that there is a functionally significant relationship between heat storage and locomotion in Asian elephants (Elephas maximus), and model the thermoregulatory constraints on activity in elephants and a similarly sized migratory dinosaur, Edmontosaurus. Pre- and post-exercise (N=37 trials) measurements of core body temperature and skin temperature, using thermography were made in two adult female Asian elephants at the Audubon Zoo in New Orleans, LA, USA. Over ambient air temperatures ranging from 8 to 34.5°C, when elephants exercised in full sun, ~56 to 100% of active metabolic heat production was stored in core body tissues. We estimate that during nocturnal activity, in the absence of solar radiation, between 5 and 64% of metabolic heat production would be stored in core tissues. Potentially lethal rates of heat storage in active elephants and Edmontosaurus could be behaviorally regulated by nocturnal activity.
... Elephants have a large heat transfer problem: they have the greatest volume-to-surface-area ratio of any terrestrial mammal [1], [2], [3] and they live in hot environments where temperatures can reach 50uC [4]. Prior studies have shown that even in a 30uC environment, an adult elephant needs to reject several kilowatts of heat averaged over a day [5], [6]. ...
... Prior studies have shown that even in a 30uC environment, an adult elephant needs to reject several kilowatts of heat averaged over a day [5], [6]. Known mechanisms of elephant heat transfer can be classified as behavioral such as ear flapping [7], dust bathing [8], moving to cooler shady areas [4] , waterspraying , mud-spraying, and bathing [1], [9], or biophysical such as skin roughness [3], blood circulation through the ears [5], [10], [11], breathing and evaporation through the skin despite the lack of sweat glands [9], or body temperature fluctuations to store and release heat during different times of the day [12]. However, none of these mechanisms alone seem to be plausibly sufficient to fulfill an elephant's heat transfer needs. ...
Article
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The idea that low surface densities of hairs could be a heat loss mechanism is understood in engineering and has been postulated in some thermal studies of animals. However, its biological implications, both for thermoregulation as well as for the evolution of epidermal structures, have not yet been noted. Since early epidermal structures are poorly preserved in the fossil record, we study modern elephants to infer not only the heat transfer effect of present-day sparse hair, but also its potential evolutionary origins. Here we use a combination of theoretical and empirical approaches, and a range of hair densities determined from photographs, to test whether sparse hairs increase convective heat loss from elephant skin, thus serving an intentional evolutionary purpose. Our conclusion is that elephants are covered with hair that significantly enhances their thermoregulation ability by over 5% under all scenarios considered, and by up to 23% at low wind speeds where their thermoregulation needs are greatest. The broader biological significance of this finding suggests that maintaining a low-density hair cover can be evolutionary purposeful and beneficial, which is consistent with the fact that elephants have the greatest need for heat loss of any modern terrestrial animal because of their high body-volume to skin-surface ratio. Elephant hair is the first documented example in nature where increasing heat transfer due to a low hair density covering may be a desirable effect, and therefore raises the possibility of such a covering for similarly sized animals in the past. This elephant example dispels the widely-held assumption that in modern endotherms body hair functions exclusively as an insulator and could therefore be a first step to resolving the prior paradox of why hair was able to evolve in a world much warmer than our own.
... Values for granular skin of other vertebrates are also considerably lower, reflecting roles other than water transport to the mouth for ingestion. For an amphibian (Woodhouse toad, Bufo woodhousei), the cutaneous water-holding capacity is less (∼0.43 mg cm −2 ), presumably because its skin granularity holds water for direct uptake across the permeable skin (Lillywhite and Licht, 1974; Lillywhite and Stein, 1987). The file snake (Acrocordis granulatus) has granular, hygroscopic skin with a water-holding capacity of 5.4 mg cm −2 , to retard desiccation when out of water (Lillywhite and Sanmartino, 1993). ...
... The file snake (Acrocordis granulatus) has granular, hygroscopic skin with a water-holding capacity of 5.4 mg cm −2 , to retard desiccation when out of water (Lillywhite and Sanmartino, 1993). Latex casts of African elephant (Loxodonta africana) skin hold 1.27 mg cm −2 , and of Asian elephants (Elephas maximus) approximately 0.81 mg cm −2 ; this serves to maintain hydration of the skin (Lillywhite and Stein, 1987). Presumably, similar biophysical constraints apply to water gain by thorny devils from other sources, such as fog condensation and dew. ...
Article
Moisture-harvesting lizards, such as the Australian thorny devil, Moloch horridus, have the remarkable ability to inhabit arid regions. Special skin structures, comprising a micro-structured surface with capillary channels in between imbricate overlapping scales, enable the lizard to collect water by capillarity and transport it to the mouth for ingestion. The ecological role of this mechanism is the acquisition of water from various possible sources such as rainfall, puddles, dew, condensation on the skin, or absorption from moist sand, and we evaluate here the potential of these various sources for water uptake by M. horridus. The water volume required to fill the skin capillary system is 3.19% of body mass. Thorny devils standing in water can fill their capillary system and then drink from this water, at approximately 0.7 μl per jaw movement. Thorny devils standing on nearly saturated moist sand could only fill the capillary channels to 59% of their capacity, and did not drink. However, placing moist sand on skin replicas showed that the capillary channels could be filled from moist sand when assisted by gravity, suggesting that their field behaviour of shovelling moist sand onto the dorsal skin might fill the capillary channels and enable drinking. Condensation facilitated by thermal disequilibrium between a cool thorny devil and warm moist air provided skin capillary filling to approximately 0.22% of body weight, which was insufficient for drinking. Our results suggest that rain and moist sand seem to be ecologically likely water sources for M. horridus on a regular basis.
... In terms of heat regulation the largest terrestrial animal – the elephant – is a case in point. Owing to its enormous body mass, the small surface-to-volume ratio and the lack of sweat glands (Spearman, 1970; Hiley, 1975; Wright, 1984; Mariappa, 1986), elephants are confronted with unusual problems concerning heat dissipation and drying of the integument (Lillywhite and Stein, 1987). Control of skin temperature (T s ) is an extremely important mechanism in elephants' temperature regulation (Phillips and Heath, 1995) and the most important thermoregulatory organs to use this pathway are the elephants' ears. ...
... Wild elephants bathe daily if they have access to water or, if not, their often coat their backs with mud (McKay, 1973; Poché , 1980; Nowak, 1999). The integument of elephants is highly sculptured with wrinkles and crevices, which promote water retention by the skin (Lillywhite and Stein, 1987). The elevation of T s facilitates evaporation of water adsorbed on the highly sculptured elephant skin due to increased saturation vapour pressure. ...
Article
In this study, we examined infrared thermograms in the course of time of six African zoo elephants and observed two phenomena. First, we noticed independent thermal windows, highly vascularised skin areas, on the whole elephants’ body and second we observed distinct and sharply delimited hot sections on the elephants’ pinnae. The frequency of thermal windows increased with increasing ambient temperature and body weight. We assume that the restriction of an enhanced cutaneous blood flow to thermal windows might enable the animal to react more flexibly to its needs with regard to heat loss. With this understanding, the use of thermal windows in heat loss might be seen as a fine-tuning mechanism under thermoneutral conditions.
... Grooves at the surface of materials retain water [33,34], and the trapping of moisture and dirt in the grooves of profiled wooden deckboards concerned Morris and Ingram [20] who mentioned its potential to affect the durability of boards. Morris and Ingram tested this hypothesis by assigning decay ratings to unprofiled and profiled subalpine fir decking that had been exposed to the weather in Vancouver for 10 years [20]. ...
... As a result, some morphological adaptations are distinguished among organisms to minimize heat gain and exposure to radiation. Wrinkles on the surfaces of the skin are one of the means for less radiation exposure by creating shaded regions, which provide a sufficient area for holding moisture and evaporation yet prevents too much direct exposure [26]. Since heat gain of an object has a direct relation to surface characteristics, the sum of environmental heat load on an object is directly related to surface area. ...
Article
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Efficient thermoregulation solutions can be extracted from strategies found in nature. Living organisms maintain body temperature in very narrow ranges in order to survive. Organisms have adopted physiological, morphological, and/or behavioral means for thermoregulation. In some organisms, the process is achieved by skin functioning as a thermal filter, whereas in others, it is achieved by their built structures. Building envelopes separate occupied indoor spaces from the exterior environment are often considered as thermal barriers or shields. Conceiving the envelope in this way limits potentially efficient solutions, where the building envelope is considered as a medium rather than a barrier, just as in living organisms. In this context, biomimetics, as a design approach, provides a huge potential for innovative thermal solutions. This work focuses on the initial phase of a biomimetic design process, where a biophysical framework is established to provide an easier access to relevant analogies. It presents a structured framework of heat regulation processes to support the search for, and the selection of, appropriate strategies from the large database of nature.
... 6 Even the sparse hairs on elephant skin influence convective heat transfer (Myhrvold, Stone, & Bou-Zeid, 2012), much the same as spines do for cacti in desert environments (Nobel, 1978). The wrinkles and crevices in elephant skin similarly serve not only to increase the total surface area available for heat exchange but also to trap and channel water, thereby improving evaporative heat loss (Lillywhite & Stein, 1987). By comparison, the relatively smooth skin of dolphins and other small cetaceans minimizes not only drag but also the transfer of heat (Boily, 1995). ...
Chapter
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Temperature has pervasive yet highly context-dependent effects on bodies, brains, and behavior. Recognizing the thermal and energetic constraints emerging from interaction between organisms and the niches they inhabit is thus critical for a comparative understanding of behavior and cognition. Critically, differences in ambient thermal conditions can both substantially alter experimental outcomes and modify the interpretation of behavioral research. Here we review key concepts necessary for understanding the role played by thermal factors and thermoregulatory processes in comparative psychology. We situate our discussion of thermoregulation in ecological, chronobiological, social, and developmental contexts, emphasizing the need for close attention to species- and age-specific differences in thermal and metabolic niches of the animals we study. Finally, the importance of a comparative approach to a number of current problems at the intersection of temperature, brain, and behavior is stressed.
... The presence of grooves on surface that run in the direction of the long axis towards the roots of the plant, provide a guided water collection and transportation, and reduced scattering of droplets [66] Water distribution Capillaries Thorny devil The scales of the integument create micro-channels from a semitubular capillary system over body surface, which transport water to the mouth via capillary forces [40] Venations Leaves A complex hierarchical network of nested loops in leaves (instead of linear) provides an optimal transportation even at events of damage [43,44] Evaporation Wrinkles Elephant skin Wrinkles provide sufficient surface area for holding moisture and evaporation [65] Cooling Diffusion Pores Tree frog skin Little pores on skin surface allow direct diffusion of condensed water [28] Humidification Reflection Trichomes Silver ragwort Trichomes are hairy structures that scatter light and result in reduced incident light at the interface [54] Light shielding for water conservation ...
Article
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Water management and regulation in buildings have been facing real challenges with the increasing environmental awareness during the last decades. Current concerns of shortage in water resources increase the demands to enhance water management strategies. In this respect, buildings should be able to gain, conserve, transport, and lose water adequately. Efficient water management solutions can be extracted from strategies found in nature. Here, we classify a basic array of strategies for water management; discuss morphological features and active means; and list corresponding examples from nature, to facilitate the search for and the selection of strategies from the large database of nature, and inspire new design solutions.
... Wright and Luck (1984) have suggested that transepidermal evaporative water loss is sufficient to achieve three-quarters of the required heat loss. The wrinkled skin of elephants has been shown to hold water and facilitate its movement on the body surface, thereby increasing the evaporative cooling effect (Lillywhite and Stein, 1987). Elephants are able to reduce heat load by using a number of behavioural mechanisms. ...
Article
(1) A captive herd of Asian elephants (Elephas maximus) exhibited dusting behaviour when the maximum daily temperature exceeded approximately 13oC, and dusting frequency increased directly with the environmental temperature. (2) Individual animals showed variation in dusting frequency but this was not related to body mass, suggesting that the function of dusting is not primarily thermoregulatory. (3) Synchronisation in the timing of dusting behaviour within the herd suggests that it may have a function in the maintenance of social cohesion. (4) The function of dusting behaviour could not be determined from the data presented, but it may be involved in skin care, protection from insects or other parasites, temperature control, protection from radiation or some combination of these.
Article
The elephant with its low surface-to-volume ratio presents an interesting problem concerning heat dissipation. To understand how such large mammals remain in thermal balance, we determined the major avenues of heat loss for an adult African elephant and an immature Indian elephant. Because conventional physiological measurements are difficult for these animals, the present study used a non-invasive technique, infrared thermography, to measure skin temperatures of each elephant. Detailed surface temperature profiles and surface area measurements of each elephant were used in standard equations for convective, conductive and radiant heat transfer. Results demonstrated that heat transfer by free convection and radiation accounted for 86% of the total heat loss for the elephants at Ta= 12·6 °C. Heat transfer across the ears, an important thermal window at high ambient temperatures, represented less than 8% of the total heat loss. Surface area of the animals, and metabolic heat production calculated from total heat loss of the African elephant, scaled predictably with body mass. In contrast, the thermal conductance of the elephants (71·6 W/°C, African; 84·5 W/°C, Indian) was three to five times higher than predicted from an allometric relationship for smaller mammals. The high thermal conductance of elephants is attributed to the absence of fur and appears to counteract reduced heat transfer associated with a low surface-to-volume ratio.
Article
AimWe propose a Megacatalyst Theory, based on the pivotal role of the micronutrients iodine (I), cobalt (Co) and selenium (Se), in answer to the body size anomaly of herbivores on different continents, and the previously unexplained absence of megaherbivores in certain environments.LocationIt is anomalous that megaherbivores are absent from Australia while present in even dry and nutrient-poor parts of southern Africa, and that they have been exterminated from the Americas, but not south-east Asia.Methods We hypothesize that I, Co and Se are micronutrients in quantity, but megacatalysts in effect, determining maximum body size and pace of life, hence whether energy is used by animals or fire. The Megacatalyst Theory suggests that the greater the reproductive rate and brain size relative to body size, the greater the probable demand for I, Co and Se.ResultsBalanced supply of I, Co and Se, within narrow tolerances, is elusive because of disparate cycles: I gravitates towards the sea, whereas Co and Se are concentrated in ultramafics and organic shales, respectively. Sufficiency of these micronutrients, at less than toxic concentrations, is vital for rapid metabolism and growth, particularly of the nervous system. Iodine controls thermogenesis, Co controls the gut fermentation supplying herbivores, and Se controls biochemical damage where both processes occur rapidly. The supply of Co allows vegetation to be metabolized instead of combusted, by promoting digestion of fibre by gut microbes. Herbivores demand I, Co and Se in greater concentrations than palatable plants necessarily contain, as an increasing proportion of energy is fermented from fibre with increasing body size. Economy of scale is limited by loss of I in urine (partly compensated by thyroid size), Co in faeces (partly compensated by gut compartments), and Se both ways.Main conclusionsThe larger the herbivore species, the more it may depend on supplementation in order to survive predation by humans. As body mass increases, Co becomes deficient before I, because it is essential for rumination, and cannot be absorbed by the skin. Moderate uplift of a fairly flat landscape sustainably supplies I from mineralized springs, and Co from rocks (and Se from both), avoiding the excess of I in the sea and the excess of Co on high mountains. Iodine and Se leached to groundwater under dry climates are inaccessible to herbivores on a continent as flat as Australia, where even kangaroos have limited fecundity and intelligence compared to southern African ruminants of similar body mass. Where springs and associated earth-licks were available in the late Pleistocene, megaherbivores could evolve to survive the era of domestication.
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Based on the combination of standard light and transmission electron microscopy, cryo-SEM, immunohistochemistry and a new sensitive glycolipid histochemical technique (5-hexadecanoylaminofluorescein staining, laser scanning microscopy), including densitometrical evaluation, our approach gives for the first time an overview of the specific biology of the epidermal permeability barrier in wild mammals (20 species from five orders), living under varying (aquatic or moist to dry) habitat conditions. The results obtained emphasised that the barrier region in most of the species studied is a continuous zone (thickness, 0. 1 and 3 μm) between the upper cells of the stratum granulosum and the inner cells of the stratum corneum conjunctum, normally present as a homogeneous glycolipid layer originating from fusion of lamellar body contents after exocytotic activities of the granular cells. However, this finding did not apply to all of the species studied, i. e., the Wild boar, the Common seal and the three large species with a very thick vital epidermis, the African elephant, the hippopotamus and the common dolphin, exhibited variations from the basic scheme. Densitometric evaluation of the 5-hexadecanoylaminofluorescein staining revealed that reaction intensity was not only generally related to the habitat conditions but also to vital epidermis thickness and hair density. The immunohistochemical demonstration of Na+/H+ exchanger 1 corroborated for all wild mammals studied that this important regulator of pH conditions during barrier formation is continuously produced in the epidermis. The variations in barrier biology observed for some species obviously had to be developed in relation to animal size (or body size area) and hair coat density, but, particularly, by the specific adaptation of certain mammalian groups to the aquatic environment. In the latter case, the typical barrier zone system was lost, as in the hippopotamus or the cetaceans.
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1. Surface temperatures of the pinnae of four female African elephants were measured at ambient temperatures between 14 and 32 degrees C using infrared thermography. Instantaneous heat losses calculated using those values ranged from 10.67 to 76.2 W under the observed conditions. 2. Using a value of 17 kcal/kg/day, those heat losses account for 0.65-4.64% of the animals' standard metabolic rates, considering one side of one ear only. 3. A model of heat flow across a flat vertical plate was constructed and compared to the actual values. Up to 100% of an African elephant's heat loss needs can be met by movement of its pinnae and by vasodilation. 4. Thermography indicates that the temperature distribution pattern across the pinna changes with ambient temperature and that areas of specialized motor control exist.
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We observed trace-making behaviors of one female African elephant (Loxodonta africana) and one female Asian elephant (Elephas maximus) in a zoo setting. Our objective was to document uncommonly studied traces, that is, traces other than dung and footprints in sediments, so that paleoichnological researchers may benefit from a broader search pattern when investigating trace fossils with potential proboscidean affinities. We observed six distinct traces: trunk-grasping traces, small pits from active and passive dispersal of water and sediment, urination traces, resting traces, wallowing traces, and dissected tracks created in partially snow-covered sediment. Of these traces, none attributable to proboscideans have been reported in the fossil record. The resting traces we observed, however, were created in dry sand and would likely not be preserved in the fossil record because of a high potential for disturbance before burial. Similarly, the trunk traces we observed in dry sand would likely have low preservation potential. Pits from thrown and blown sediment and water, wallowing traces, and snow-influenced tracks should have a higher probability of survival into the fossil record. Tracks representative of partially snow-covered ground are recognizable by sediment pedestals within undertracks. In such tracks, which we refer to as hanging tracks, the top surface of the pedestal is all that remains of the true track. The undertrack surrounding the pedestal(s) was created from the elephant’s foot pressing snow into the underlying sediment. The snow later melted away. Pleistocene proboscideans likely encountered partially snow-covered ground, so hanging tracks may be preserved in the rock record. Recognition of these tracks would be extremely informative about paleoclimate, but further research is needed to determine if they can be easily distinguished from tracks created exclusively in sediment.
Thesis
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Several biomimetic design strategies are available for various applications, though the research on biomimetics as a design tool in architecture is still challenging. This is due to a lack of systematic design tools required for identifying relevant organisms, or natural systems, and abstracting the corresponding generic principles for implementation in design concept generations for building envelopes. A major challenge in current strategies is the filtering of the wide possibilities that nature provides, especially for architects who have limited biophysical background. In order to find design solutions from nature, the requirements of the artificial system have to be defined, and then analogue systems in nature that perform similar functions need to be identified. The design generating tools should support the transitions between the domains, especially the identification of biological analogies and their abstraction. To this end, the current thesis proposes a strategic methodology, referred to as the living envelope methodology, for the generation of design concepts. The proposed methodology provides an exploration and investigation platform for architects. It assists channelling the way from technical challenges, defined by the demands on the living envelope, through functional aspects and various strategies found in nature. Furthermore, the proposed methodology provides several phases of categorizations that funnel at the end into a single imaginary organism/system, referred to as imaginary pinnacle, which has the successful dominant features of the desired living envelope. The various phases and sub-phases of the methodology facilitate the transitions between the various phases of the design process, with a special attention to the representation of biophysical information, identification and abstraction of principles, and their systematic selection. Systematic exploration models are developed for the biophysical information representation, and unique schemes and flow charts that provide user-friendly design tools are developed and presented. For the validation of the methodology and the assessment of its generality, four important environmental aspects that need to be managed by the building envelope are applied to the methodology: (1) air – to manage ventilation, which is required in order to provide high indoor air quality and to prevent air stagnation; (2) heat – to maintain a thermal comfort for the occupants; (3) water – to gain and make use of condensed water in arid areas; and (4) light – to provide a shading system with minimized undesired heat gain and maximized daylight. For each of the four aspects exemplary design concepts are successfully generated. It is worth noting that the aim of investigating these environmental aspects is not to provide detailed design solutions; rather the presented examples of the generated design concepts examine the generality of the implementation of the methodology. In order to further assess the generality of the proposed methodology, a qualitative example that combines all four environmental aspects is introduced. The results of the exemplary design concepts show the advantage of the proposed living envelope methodology. The methodology is capable to generate design concepts with specified initial challenge set by the user (architect). Moreover, the design cases open new perspectives for new possible technical solutions for building envelopes, and the potential to realize a new class of innovation and lay a functional foundation in architecture: a bio-inspired, climatically oriented, and environmentally conscious.
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In previous studies, the superhydrophilic skin of moisture-harvesting lizards has been linked to the morphological traits of the lizards’ integument, that is, the occurrence of honeycomb-shaped microstructures. Interestingly, these structures can also cover the skin of lizards inhabiting wet habitats. We therefore tested the influence of the microstructures’ main features on the habitat choice and wettability in the genus Phrynosoma. The genus Phrynosoma comprises moisture-harvesting species as well as nonspecialists. Lizards of this genus inhabit large areas of North America with diverse climatic conditions. Remarkably, the differences in the manifestation of microstructures are just as versatile as their surroundings. The phylogeny of the lizards as well as the depth of their ventral microstructures, though independent of each other, correlated with the precipitation in their respective habitat. All other morphological traits, as well as the skin's wettability itself, could not predict the habitat of Phrynosoma species. Hence, it is unlikely that the microstructure influences the wettability, at least directly. Hence, we presume an indirect influence for the following reasons: (a) As the ventral side cannot get wet by rain, but the belly could easily interact with a wet surface, the microstructure might facilitate water absorption from wet soil following precipitation. (b) We found the number of dorsal microstructures to be linked to the occurrence of silt in the habitat. In our study, we observed scales being heavily contaminated, most likely with a mixture of dead skin (after shedding) and silt. As many lizards burrow themselves or even shovel sand onto their backs, deploying the substrate might be a mechanism to increase the skin's wettability.
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An adequate rate of evaporative water loss is considered essential for the maintenance of thermal balance in the elephant in warm climatic conditions. Histological studies have failed to reveal the existence of sweat glands in elephant skin. Transepidermal water-loss rate has been measured and shown to be sufficiently high for possible thermal needs. The structure of elephant skin and the behaviour of elephants are seen to contribute towards maintaining skin permeability and the necessary level of transepidermal water loss,’n Toereikende tempo van waterverdamping word as noodsaaklik beskou vir die handhawing van hittebalans in olifante onder warm klimaatstoestande. Histologiese studies het tot nou toe nie die teenwoordigheid van sweetkliere in olifantvel bewys nie. Die tempo van transepidermale waterverlies is gemeet, en blyk hoog genoeg te wees om moontlike hittevereistes te dek. Daar word getoon dat die velstruktuur van die olifant, asook die olifant se gedrag, ’n bydrae lewer tot die handhawing van veldeurlaatbaarheid en die behoud van die vlak van transepidermale waterverlies.
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When live toads (Bufo) are placed on a water-saturated surface, it can be demonstrated that a film of water moves upward over the sides of the body and, in some individuals, reaches the dorsal midline. Movement of water over the skin follows interconnecting channels which characterize the outer epidermis of many terrestrial species. It was demonstrated that such water movement may replenish evaporative losses from skin surfaces and act to retard both cutaneous desiccation and elevated temperatures in individuals which are forced to bask in the laboratory. Observations and experiments suggest the possibility that epidermal sculpturing of terrestrial Bufonidae may have a functional role in relation to water uptake, thermoregulation and the prevention of integumentary desiccation.
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The amount of “bound water” in dense biological membranes such as human stratum corneum (keratin) can be estimated from the water desorption curves of the hydrated tissue. A distinct decrease in the rate of desorption, measured continuously with a microbalance, marks the transition between the elimination of free water and “bound water” from the tissue. The amount of “bound water” in fully hydrated stratum corneum can be as much as five times the dry weight of the tissue.
Article
The subdermal glands of Hippopotamus amphibius are scattered over almost the entire skin surface, but are most frequent over the dorsal and flank skin. They are situated in the plane between the dermis and the subcutaneous tissue. They are from 2–5 cm. to 0–5 cm. in diameter, lenticular in form, and usually possess two secretory ducts. Histologically, they are compound tubulo-acinar glands. The acini are composed of varying proportions of mucous cells and granular serous cells. The tubular system of secretory cells opens into a collecting system of larger ducts, which in turn open into the main secretory duct, which spirals through the thick collagenous dermis to end at a punctum on the epidermal surface. The communications of Tomes (1850) and Crisp (1867) to the Society are quoted, and the relationship between the observable phases of secretion and the various types of secretory cell is described. The subdermal glands of Hippopotamus amphibius are numerous, lenticular, discrete organs. Microscopic examination shows them to be compound tubulo-acinar glands, the secretory cells of which are of three different types, cuboidal eccrine, serous granular and mucous gland cells. The cytological characteristics of these cells suggest that they are related to the three phases of active secretion from the subdermal glands.
Article
Evidence is reviewed and observations are submitted concerning the occurrence and distribution of body hair in rhinoceroses. Absence of externally visible hair is shown to be not necessarily indicative of absence of hair follicles and to be part of a morphological cooling mechanism necessitated by the dynamics of the large body. Eyelashes are shown to be present on the lower eyelid of three species at least. The post-natal absence of all groups of facial vibrissae is confirmed for all rhinoceros forms, but a genal vibrissa is recorded for a Diceros foetus. Observations are submitted upon the hitherto undescribed histology of Diceros skin.
Article
An account is presented of the memoranda and drawings comprising the description of the African Black rhinoceros prepared at the Cape of Good Hope in 1778 by Robert Jacob Gordon (1743–95) and now incorporated in the Gordon Atlas preserved in the Rijksmuseum Amsterdam. Gordon's rhinoceros information was placed at the disposal of contemporaries, whereby part of it entered zoological literature and occasioned the temporary recognition of a “Gordon's rhinoceros”. His material never attained independent publication and its historical and anatomical merit has thus escaped recognition. Impressive in standards of observation and delineation it represents a pioneer investigation of African rhinoceros morphology.
Article
In the skin of the head of an african elephant (Loxodonta africanus) various regions of the epidermis have been investigated in histological sections as well as in whole mounts prepared by macerating the epidermis of the dermis. The relief of the dermo-epidermal junction is characterized by the presence of big complex papillae, the surface of which consists of smaller papillae. In the skin of the forehead and of the cheeks there are typical variations in the pattern of the dermo-epidermal relief. On the forehead the thick epithelium forms polygonal columns of cornified cells on top of the complex papillae. These columns may be as high as 1 cm. Groups formed by several such columns are seperated from each other by deep clefts and fissures. On the cheeks the epidermis has a thickness of only 1 mm. Here we find flat warts of cornified epithelium instead of the high columns. The distribution of the pigmented cells in the epidermis is described. The stratum granulosum is absent in the region of the forehead but it is present in the region of the cheeks. From the entrance towards the end of the meatus acusticus internus there is a continuous and characteristic change in the hairiness and in the pattern of the dermo-epidermal relief.
1.1. Nine animal species were investigated in relation to their transepidermal water loss (T.W.L.) values and this variable correlated with the thickness of their epidermal components.2.2. Various experimental procedures were also applied to change the thickness of these components.3.3. It is concluded that, in the skins investigated, barrier function does not reside only in the thickness of any epidermal component, and this suggested that the basement membrane might act as a “wick” in transporting fluid upwards through the epidermis from the deeper skin areas.
Article
Moloch horridusis an agamid lizard living in the desert regions of Western and South Australia. It weighs as much as 50 gm. and has been described by Buxton1 as "a repulsive animal with tubercles and spines, it has the power of absorbing water through the skin after showers of rain". This ability of absorbing water through the skin is characteristic of many Amphibia and is correlated with a ready loss of water by the same route2. Reptiles living in arid conditions would find a water-permeable skin uneconomical for water conservation so that this mode of taking up water may be questioned for Moloch.
Article
The elephant, black and white rhinoceros and the hippopotamus inhabit similar country, feed off land vegetation and have superficially the same type of almost hairless skin. The hippopotamus, however, is unique in spending most of the daytime in water or mud and feeding almost entirely at night or in the early morning. A study has been made of the structure of the epidermis of these animals and the differences found can, broadly speaking, be explained as modifications that are in accord with the animal's mode of life and surroundings. A more detailed study of the hippopotamus's skin shows that its structure, while probably primarily one of many possible modifications for an aquatic environment, permits a rate of transepidermal water loss that is greater than that in other animals for which figures can be obtained. No certain biological function can be proposed for this rapid loss of water; it is suggested that it is brought about by evaporation from the exposed layers of PAS-positive material which in this skin are continuous from the Malpighian layer to the surface of an unusually thin stratum corneum.
Article
The Journal of Investigative Dermatology publishes basic and clinical research in cutaneous biology and skin disease.
Some observations on food habits and behaviour of the African elephant Transport of water by adult sandgrouse to their young
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