Zeev Arad

• PhD
• Professor (Full) at Technion – Israel Institute of Technology

In Israel, which is a bottleneck for some six hundred million migrating birds, the drainage of the Hula Lake in the north resulted in serious conflicts between fish-eating birds and the intensive fish farming and agriculture that became established on the reclaimed land. Implementation of various deterrence methods, including lethal control, failed...

Plant secondary compounds (PSCs) have profound influence on the ecological interaction between plants and their consumers. Glycosides, a class of PSC, are inert in their intact form and become toxic on activation by either plant β-glucosidase enzymes or endogenous β-glucosidases produced by the intestine of the plant-predator or its microbiota. Man...

Land snails are exposed to conditions of high ambient temperature and low humidity, and their survival depends on a suite of morphological, behavioral, physiological, and molecular adaptations to the specific microhabitat. We tested in six populations of the land snail Theba pisana whether adaptations to different habitats affect their ability to c...

Glycosides are a major group of plant secondary compounds characterized by one or more sugars conjugated to a lipophilic, possibly toxic aglycone, which is released upon hydrolysis. We compared small intestinal homogenate hydrolysis activity of three rodent and two avian species against four substrates: amygdalin and sinigrin, two plant derived glu...

Abstract Land snails frequently encounter desiccating conditions, and their survival depends on a suite of morphological, physiological, and molecular adaptations to the specific microhabitat. Strategies of survival can be determined by integrating information from various levels of biological organization. In this study, we used a combination of p...

In contrast to most other plant tissues, fleshy fruits are meant to be eaten in order to facilitate seed dispersal. Although fleshy fruits attract consumers, they may also contain toxic secondary metabolites. However, studies that link the effect of fruit toxins with seed dispersal and predation are scarce. Glucosinolates (GLSs) are a family of bit...

Fleshy, ripe fruits attract seed dispersers but also seed predators. Although many fruit consumers (legitimate seed dispersers as well as seed predators) are clearly exposed to plant secondary compounds (PSCs), their impact on the consumers' physiology and foraging behaviour has been largely overlooked. Here, we document the divergent behavioural a...

Food and water resources are limiting factors for animals in desert ecosystems. Fleshy fruits are a rare water source in deserts and when available they tend to attract a wide variety of organisms. Here we show that two congeneric rodent species, Acomys cahirinus and A. russatus, employ different fruit eating strategies that result in either disper...

The population dynamics of the land snail Theba pisana (Helicidae) was studied for two successive years in the sand dunes of northern Israel and under laboratory conditions. The field population in autumn consisted of two size classes: large snails of more than 10 mm in diameter and small snails of less than 5 mm in diameter. After the first rain,...

Slope orientation in the Mediterranean climate may lead to different adaptations of the faunistic elements to the environment. The south-facing slope (SF) of Lower Nahal Oren (Mount Carmel) is more exposed to solar radiation and therefore is warmer, drier, and has a lower vegetation coverage than the north-facing slope (NF). Resistance to desiccati...

This study compares the water relations and resistance to desiccation in three species of land snails of different phylogenetic origins: the prosobranch Pomatias glaucus and the pulmonates Helix engaddensis and Sphincterochila cariosa. All three species are understone-dwellers of the Mediterranean climatic zone of Israel. S. cariosa was the most re...

The Levant vole Microtus guentheri is a common species in the “Fertile Crescent". The populations of this species in Israel are marginal and they seem to be well adapted to the long dry and warm season of the Mediterranean ecosystem. Heat production and dissipation, nonshivering thermogenesis, and food and energy consumption were studied in voles a...

Plant secondary metabolites (SMs) acting as defensive chemicals in reproductive organs such as fruit tissues play roles in both mutualistic and antagonistic interactions between plants and seed dispersers/predators. The directed-deterrence hypothesis states that SMs in ripe fruits deter seed predators but have little or no effect on seed dispersers...

Land snails are subject to daily and seasonal variations in temperature and in water availability, and use heat shock proteins (HSPs) as part of their survival strategy. We used experimental heat stress to test whether adaptation to different habitats affects HSP expression in two closely related Sphincterochila snail species, a desert species, Sph...

Polmunate land snails are subject to stress conditions in their terrestrial habitat, and depend on a range of behavioural, physiological and biochemical adaptations for coping with problems of maintaining water, ionic and thermal balance. The involvement of the heat shock protein (HSP) machinery in land snails was demonstrated following short-term...

Plant secondary metabolites (SMs) are pervasive in animal foods and potentially influence feeding behavior, interspecies interactions, and the distribution and abundance of animals. Some of the major classes of naturally occurring SMs in plants include many water-soluble compounds in the molecular size range that could cross the intestinal epitheli...

Land snails are subject to daily and seasonal variations in temperature and in water availability, and have evolved annual cycles of activity and aestivation as part of their survival strategy. We tested in the field whether adaptation to different habitats affects the endogenous levels of heat shock proteins (HSPs) in two closely related Sphincter...

Land snails are subject to daily and seasonal variations in temperature and in water availability and depend on a range of behavioral and physiological adaptations for coping with problems of maintaining water, ionic, and thermal balance. Heat shock proteins (HSPs) are a multigene family of proteins whose expression is induced by a variety of stres...

Land snails are subject to desiccating conditions in their terrestrial habitat. Our previous studies have revealed significant differences in resistance to desiccation among closely related species and among genera that share a similar life style, suggesting that the distribution pattern is correlated with the abiotic regime in its specific habitat...

The land snail Sphincterochila is represented in Israel by five species that replace one another along a climatic gradient that ranges from the Mediterranean areas receiving up to 1000 mm down to arid areas receiving only 70 mm of rain per year. The resistance to three weeks of desiccation was studied in all five species. Total water loss was lowes...

Bush-dwelling land snails are exposed to desiccating conditions that are more severe than those of snails that seek the shelter of rock crevices, litter or the upper layers of the soil. We studied the resistance to desiccation in four bush-dwelling species of Israeli snails to evaluate a possible relation between their water economy and their distr...

Empleamos un enfoque alométrico para comprar los requerimientos mínimos de nitrógeno (RMN) y la pérdida total endógena de nitrógeno (PTEN) de aves nectarívoras y frugívoras con los parámetros observados en aves omnívoras. Los dos parámetros fueron cuatro veces mayores en los omnívoros que en los nectarívoros y frugívoros. En aves nectarívoras y fru...

Great cormorants are foot-propelled aquatic divers utilizing a region of the water column where their underwater foraging behavior is affected by their buoyancy. While swimming horizontally underwater, cormorants use downward lift forces generated by their body and tail to overcome their buoyancy. Here we assess the potential of this swimming strat...

We used nitrogen isotope analysis from pectoral muscle of the Egyptian fruit bat Rousettus aegyptiacus (Chiroptera: Pteropodidae) to determine intrapopulation variation in sources of dietary protein throughout the year in northern Israel. In Mediterranean climates, winter and summer are stable seasons, whereas spring and fall are transitional seaso...

The Great White Pelican Pelecanus anocrotalus is the largest migrating bird in Israel and is an endangered species. The Palearctic populations of the Great White Pelican breed in eastern Europe and Asia and most of them pass through the ‘bottleneck’ of Israel to wintering grounds in Africa. Natural feeding sites for pelicans have diminished during...

The scattering and absorption of light by water molecules and by suspended and dissolved matter (turbidity) degrade image transmission and, thus, underwater perception. We tested the effects on visual detection of prey size and distance (affecting apparent prey size) and of low-level water turbidity in hand-reared great cormorants (Phalacrocorax ca...

The rate at which an animal's tissues incorporate the isotopic composition of food determines the time window during which ecologists can discern diet changes. We investigated the effect of protein content in the diet on the incorporation rate of (15)N into the plasma proteins and blood cells of Yellow-vented bulbuls (Pycnonotus xanthopygos). Using...

Air-breathing divers should attempt to maximize foraging efficiency under the constraint of limited oxygen availability. For diving water birds, high buoyancy (owing to the air in the plumage) and the associated change in buoyancy with diving depth impose further constraints on the adaptation to aquatic life. Diving birds are expected to descend as...

We used an allometric approach to compare the minimum nitrogen requirements (MNR) and the total endogenous nitrogen loss (TENL) of nectar- and fruit-eating birds with those of omnivorous birds. These two parameters were 4× higher in omnivores than in nectarivores and frugivores. In nectarivorous-frugivorous birds, MNR was $152.8\ {\rm mg}\ {\rm N}\...

We used an allometric approach to compare the minimum nitrogen requirements (MNR) and the total endogenous nitrogen loss (TENL) of nectar- and fruit-eating birds with those of omnivorous birds. These two parameters were 4× higher in omnivores than in nectarivores and frugivores. In nectarivorous-frugivorous birds, MNR was 152.8 mg N kg−0.76 day−1;...

Uric acid is the main nitrogenous waste product in birds but it is also known to be a potent antioxidant. Hominoid primates and birds lack the enzyme urate oxidase, which oxidizes uric acid to allantoin. Consequently, the presence of allantoin in their plasma results from non-enzymatic oxidation. In humans, the allantoin to uric acid ratio in plasm...

Transcriptional induction of heat-shock genes in response to temperature elevation and other stresses is mediated by heat-shock transcription factors (HSFs). Avian cells express two redundant heat-shock responsive factors, HSF1 and HSF3, which differ in their activation kinetics and threshold induction temperature. Unlike the ubiquitous activation...

Waterbirds are buoyant because of volumes of air in their plumage and respiratory tract. When they are submerged, their buoyancy is reduced, owing to compression of these volumes of air with depth. We tested how the horizontal submerged swimming of cormorants (Phalacrocorax carbo sinensis (Blumelbach, 1798)) changed when their buoyancy was artifici...

The distribution of the bush-dwelling snail Theba pisana (Helicidae) in Israel is restricted to the coastal plain. It is known as an annual semelparous species, but recent studies revealed that part of the population has a biennial life cycle. The present study examined the water economy and resistance to desiccation throughout the life cycle under...

This study examines the water economy and resistance to desiccation in a minute (5 mg snail mass; 3 mm shell height) litter-dwelling land snail Lauria cylindracea (Pupillidae). As expected from its small size and from its moist habitat, L. cylindracea exposed to normothermic desiccation lost water at the highest rate revealed so far in our studies...

Cormorants are water birds that forage by submerged swimming in search and pursuit of fish. Underwater they swim by paddling with both feet simultaneously in a gait that includes long glides between consecutive strokes. At shallow swimming depths the birds are highly buoyant as a consequence of their aerial lifestyle. To counter this buoyancy cormo...

Living organisms respond to heat exposure by selectively expressing heat shock proteins (HSPs). Accumulation of HSPs confers thermotolerance in cell cultures and in ectotherms and is an important component of the heat shock response. This response, however, has not been directly examined in relation to different ;thermal states', namely ectothermy...

We measured minimal nitrogen requirements (MNR), total endogenous nitrogen loss (TENL) and the effect of protein and water intake on the nitrogenous waste composition in two frugivorous bird species: yellow-vented bulbuls Pycnonotus xanthopygos and Tristram's grackles Onychognathus tristrami. The nitrogen requirements of both species were much lowe...

Nectar-feeding birds have remarkably low nitrogen requirements. These may be due either to adaptation to a low-protein diet or simply to feeding on a fluid diet that minimizes metabolic fecal nitrogen losses. We measured minimal nitrogen requirements (MNR) and total endogenous nitrogen loss (TENL) in the omnivorous European starling Sturnus vulgari...

Cormorants are assumed to have a “partially wettable” plumage as a mechanism to reduce buoyancy while swimming underwater. This assumption is mainly based on 3 observations: 1) the volume of air in the plumage of submerged carcasses is small compared to other water birds, 2) cormorants assume a “wing drying” posture when they exit the water, and 3)...

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Buoyancy is a de-stabilizing force for diving cormorants that forage at shallow depths. Having to counter this force increases the cost of transport underwater. Cormorants are known to be less buoyant than most water birds but are still highly buoyant (rho= approximately 0.8 kg m(-3)) due to their adaptations for aerial flight. Nevertheless, cormor...

This study explored how a flying frugivorous mammal, the Egyptian fruit bat (Rousettus aegyptiacus), meets the increased energy requirements of reproduction. This bat feeds on low-protein fruit, and females have bimodal polyestrous cycles that are rel­ atively long for a small mammal. We measured the energy and water balance of captive nonreproduct...

We compared growth rates and adult morphological traits in two sympatric cormorant species, the pygmy cormorant (Phalacrocorax pygmeus) and the great cormorant (P. carbo sinensis), in Israel. The smaller P. pygmeus exhib-ited higher developmental rates than P. carbo sinensis, as expressed in the growth rate constant (K) of body mass and of various...

Because migration routes and stopover sites of the endangered Palearctic migratory Great White Pelican (Pelecanus onocrotalus) are poorly known, satellite tracking was used to map spring and autumn migration routes, stopover sites and ranging areas in Europe, Israel and Africa. Four immature and one adult individual were equipped with transmitters...

Land snails are subjected to annual cycles of activity and aestivation in relation to seasonal changes in temperature, humidity, and water availability and, therefore, should be adapted with a range of behavioral and physiological mechanisms that will ensure their survival under their specific microhabitat conditions. This study tested the physiolo...

Shmueli, M., Arad, Z., Izhaki, I. & Crivelli, A. 2000. The energetic demand of the Great White Pelican during migration in Israel and its implication to the conflict between fish industry and pelicans. Ostrich 71 (1 & 2): 1.The Great White Pelican Pelecanus onocrotalus is a migrating bird, which is an endangered species. The majority of the western...

The Great White Pelican Pelecanus onocrotalus is an endangered migratory bird, threatened by diminishing natural feeding sites and by persecution by fishermen. The majority of the migrating White Pelican (71000) stop-over in Israel during their autumn migration to Africa. As part of a larger study, aimed to assess the necessity of feeding during th...

The metabolic and thermoregulatory capacities of the Macedonian mouse (Mus macedonicus) of a population from a post-fire habitat on Mount Carmel, Israel, were studied. Post-fire habitats in the Mediterranean ecosystem of Mount Carmel are invaded by species that exist in the forest margins, including M. macedonicus, which established the largest mic...

We studied the blood profile of the free-living fruit bat (Rousettus aegyptiacus) during the beginning of the activity period (around various feeding trees) and upon return to the day roost during 1994-1995. Results of the present study suggest that during winter and early spring bats are characterized by a poor physical and physiological state as...

1. The Macedonian mouse (Mus macedonicus), a small (15 g) mesic rodent distributed in the Mediterranean ecosystem, is a species which invades post fire habitats in the first stages of habitat recovery. 2. In order to assess the seasonal acclimatization of thermoregulatory and metabolic mechanisms, the response of several physiological variables to...

The Egyptian fruit-bat Rousettus aegyptiacus is regarded as a pest for agriculture. However, no quantitative data on its diet have been collected in Israel or in other Mediterranean areas, and control measures in the past reduced populations of insectivorous bats in Israel. We therefore studied the relative importance of native versus commercially...

The majority of heron species (Aves, Ardeidae) forage on aquatic prey in shallow water. Prey detection, aiming and the beginning of the capture strikes are performed while the heron's eyes are above water. For most angles, as a result of air/water light refraction, the apparent image available to a heron is vertically displaced from the prey's real...

Composition of milk of the free-ranging Egyptian fruit-bat (Rousettus aegypriacus) was studied from early to peak lactation. Carbohydrates were the main component during early lactation and fats were the main component in milk from mid- to peak lactation. Dry-matter and energy content of the milk increased during mid-lactation and stabilized at pea...

Composition of milk of the free-ranging Egyptian fruit-bat (Rousettus aegyptiacus) was studied from early to peak lactation. Carbohydrates were the main component during early lactation and fats were the main component in milk from mid-to peak lactation. Dry-matter and energy content of the milk increased during mid-lactation and stabilized at peak...

Thermoregulatory mechanisms in rodents were found to respond to photoperiod manipulations. In desert adapted species, non-shivering thermogenesis NST-capacity (the ratio between the maximal VO2 response to noradrenaline injection and RMR, measured 1 degree C below the lower critical point) increased, as due to long scotophase acclimation. The aim o...

This study analyses the fruit syndrome of the Egyptian fruit-bat, Rousettus aegyptiacus, the only fruit-bat found in East Mediterranean habitats. Two different sets of bat-fruit syndromes were revealed. One follows the general bat-fruit syndrome and one represents a special case of bat-dispersed fruit syndrome only found in East Mediterranean habit...

Temperature selection in a thermal gradient and the physiological responses to heat exposure were studied in the Moorish gecko, Tarentola mauritanica, from Crete. In association with previous indications that the Moorish gecko has a bimodal activity pattern, we found a bimodal temperature selection with modes at 27-28 and 30-32°C. In this respect,...

The nitrogen and energy balances of the Egyptian fruit bat, Rousettus aegyptiacus (Pteropodidae), were determined in a series of studies of animals on five single-fruit diets differing in their nutritional content (carob, Ceratonoia siliqua; Persian lilac, Melia azedarach; loquat, Eriobotrya japponica; mulberry, Murus nigra; and sycamore, Ficus syc...

Interspecific differences in the responses to increasing ambient temperature (up to 40°C) were studied in three species of Ptyodactylus that differ in their distribution in Israel, in their daily activity pattern and in their preferred body temperatures: the northern, diurnal P. puiseuxi, the southern, nocturnal P. hasselquistii and the diurno-noct...

We have examined the resistance to desiccation among rock-dwelling land snails of various phylogenetic groups:Cristataria genezarethana (Clausiliidae),Rupestrella rhodia (Chondrinidae) andLevantina caesareana (Helicidae), all from the same location in Israel.L. caesareana was the most resistant andR. rhodia the least resistant to desiccation andC....

The fruit-bat Rousettus aegyptiacus (Pteropodidae) in Israel consumes a variety of cultivated and wild fruits. The aim of this study was to explore some of its qualities as a dispersal agent for six fruit-bearing plant species. The feeding roosts of the fruit-bat are located an average of 30 m from its feeding trees and thus the bats disperse the s...

1.1. The populations of the Levant vole, Microtus guentheri, inhabiting the Mediterranean ecosystem of Israel, are marginal populations which seem to be well adapted to its long dry and warm season. The thermoregulatory and metabolic responses of the Levant voles of Israel to manipulation of photoperiod were studied to assess to role of photoperiod...

Theba pisana is a bush-dwelling snail with a circum-Mediterranean distribution. In Israel it is limited to a narrow coastal strip, along which there is a north-to-south gradient in mean annual rainfall (700–300 mm per year). In this study we found significant intraspecific differences among populations ofT. pisana in resistance to desiccation along...

1. The effect of acute heat exposure on triglyceride (TG) transfer to preovulatory follicles was studied in the laying fowl. 2. Heat exposure of laying fowl resulted in a 1.1 degree C rise in body temperature, a 10-fold increase in respiration frequency and mild hypocapnia and hypoxaemia. 3. Plasma and follicular tissue TG concentrations were not s...

1. The effect of heat exposure (air temperature 35–45°C) for 1.5 h on blood flow distribution between the abdominal viscera and the muscles of abdominal wall and hind leg was investigated in unanaesthetised, unrestrained laying fowl.2. Heat stressed fowl showed a significant hyperthermia (+ 1.3°C), rapid shallow breathing (229 breaths/min) and sign...

We compared water relations and resistance to desiccation in three sympatric desert land snails, Eremina desertorum, Euchondrus desertorum and Euchondrus albulus. Ermina was the most resistant and Eu. albulus the least resistant to desiccation. Juveniles of both Euchondrus species were more susceptible to desiccation than adults. The rate of mass l...

1.1. The thermoregulatory responses of the fruit-bat, Rousettus aegyptiacus, the only fruit-bat out of 32 bat species in Israel, were studied over a wide range of ambient temperature during normal hydration and during water restriction.2.2. The thermoneutral zone of the normally-hydrated fruit-bat ranged between 31–36°C. Oxygen consumption in this...

The energy budget, water balance and osmoregulation of the fruit bat, Rousettus aegyptiacus, were studied during normal hydration and during water restriction (oven-dried apple diet). The water input and output were balanced during both normal hydration and water restriction. The kidney of the fruit bat is well adapted to handle the water load from...

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 distr...

1. The effect of dehydration and heat exposure on body and brain temperature was studied in quail exposed to increasing ambient temperatures within the range of 25-40 degrees C. 2. The body-to-brain temperature difference was not affected by increasing ambient temperature or hydration state. A mean body-to-brain temperature difference of 0.96 +/- 0...

1.1. The effect of dehydration and heat exposure on body and brain temperature was studied in quail exposed to increasing ambient temperatures within the range of 25–40C.2.2. The body-to-brain temperature difference was not affected by increasing ambient temperature or hydration state. A mean body-to-brain temperature difference of 0.96 ± 0.64C and...

Development of brain temperature regulation was studied in the precocial chick of the Japanese quail from hatching to 21 d of age during exposure to ambient temperatures of 35°, 30°, 25°, and 20° C. The newly hatched quail maintained a stable body-to-brain temperature difference from the day of hatching, although at relatively hypothermic levels co...

1. Development of brain temperature regulation was studied in the domestic fowl (Gallus gallus domesticus) from hatching to 21 d of age. 2. Body and brain temperature at hatching were relatively low compared with adult levels. However, both were effectively regulated at ambient temperatures of 30 and 35°C, with only a minor difference between the 2...

The brain cooling capacity of the altricial pigeon increases during posthatching growth at a higher rate than that of the precocial duck and chicken. To determine if this difference between the altricial and the precocial modes of development can be related to growth rates of the vascular heat exchanger involved in brain cooling (the ophthalmic ret...

The capability of birds to keep the brain cooler than the body over a wide range of ambient temperatures is a major thermoregulatory characteristic enabling the defense of the central nervous tissue from overheating, heat storage and saving of water. Brain cooling is related to the presence of a paired extra-cranial vascular heat exchanger, the ret...

The aim of this study was to characterize the dynamic changes in uterine fluid composition and acid-base status during shell calcification in the chicken. Uterine eggs at timed intervals were manually aborted and the accompanying fluid collected and analyzed for composition of osmolytes, enzymes, and acid-base parameters. Blood samples were analyze...

Time-related changes in shell porosity and eggshell water vapour conductance were measured in uterine eggs of the domestic fowl (Gallus domesticus) from 10 h in uterus to oviposition. Measurements were carried out in artificially-aborted eggs. It was found that the eggshell water vapour conductance decreased to a minimum level at 15 h in uterus. Th...

Osmoregulatory and volume-regulatory responses of heat-acclimated pigeons (Columba livia) were studied during normal hydration and dehydration combined with heat exposure. Dehydrated heat-exposed pigeons (exposure to 50 degrees C following 48 h of water deprivation; 16-18% mass loss) could recover 97% of their initial body mass within 30 min of fre...

The vasculature of skin and of peripheral heat exchangers in Turkey Vultures (Cathartes aura, mass 1.4 kg) was studied in relation to peripheral temperatures and behavior at ambient temperatures (T_a) from 10°C through 50°C. The head's unfeathered skin contains thin-walled, anastomosing veins near the epidermis. Metatarsal skin has a simi...

Development of brain temperature regulation was studied in the altricial hatchling of the pigeon from hatching to 30 d of age during exposure to ambient temperatures of 30° and 35° C. The newly hatched pigeons were completely poikilothermic. However, brain and body temperatures increased in an exponential relation with age, approaching adult levels...

The three Israeli forms of Ptyodactylus (P. hasselquistii puiseuxi, P. h. guttatus and P. h. hasselquistii) differ in daily activity pattern, being mainly diurnal, diurno-nocturnal and nocturnal, respectively. We measured body temperatures of the three forms in a photothermal gradient. They differed significantly from each other in mean selected bo...

1.1. Studies in respiratory physiology and acid-base balance of panting birds exposed to high Ta s show that flying as well as nonflying birds can use the respiratory system simultaneously for gas exchange and evaporative cooling.2.2. The present study proves that well acclimated hand-reared birds can effectively regulate a normal CO2 level and aci...

Temperature regulation by six Turkey Vultures (Cathartes aura) was studied at ambient temperatures (Ta) from 11 to 40°C in a metabolic chamber. Within this range body temperature varied little, averaging 39.7°C, and the ratio of CO2 production to O2 consumption averaged 0.76. The thermal-neutral zone (TNZ) extended from 26 to 40°C. Below 26°C evapo...

Eggshell water vapor conductance (GH₂O), shell thickness (T), and effective pore area (Ap) of eggs from pigeons (Columba livia) nesting under extreme conditions (high ambient temperatures and low humidity) were compared with those of urban pigeons and pure rock doves breeding in mesic conditions. Heat-acclimated pigeons had eggshells characterized...

The effect of water deprivation (dehydration) on cutaneous water evaporation (CWE, E,) was studied in seven heat-exposed rock pigeons (Columba livia). Dehydrated pigeons lost about 16% of the initial body mass after 48 h of water deprivation and additional heat exposure, resulting in a significant increase in hematocrit and serum sodium and chlorid...

In posthatching mallard ducks (Anas platyrhynchos), brain cooling improves with growth. To determine whether this may be correlated with growth-related changes in morphology of the rete ophthalmicum, we studied the development of this rete in immature mallards from hatching to 29 days of age. We found that the number of arteries and veins was fixed...

The effects of high- and low-NaCl diets on body temperature, plasma osmolality, plasma electrolytes and arginine vasotocin (AVT) were studied in the domestic fowl. Body temperature as a function of time increased or decreased significantly in the high- and low-NaCl groups respectively. Plasma osmolality, sodium and chloride concentrations and AVT c...

1. White Plymouth Rock hens were fed a high- and a low-NaCl content of the diet. The two groups were exposed to moderate dehydration, to intra-arterial hyperosmotic NaCl-loading, or to injection of physiological doses of arginine vasotocin (AVT). 2. The plasma levels of AVT and prolactin were measured by accurate and sensitive radioimmunoassay and...

Bird heads contain paired countercurrent heat exchangers, the ophthalmic retia, which function in brain temperature regulation. Blood, cooled by evaporation from the nasal and buccal mucosa and the ocular surfaces, flows to the venous side of each rete and there gains heat from arterial blood flowing countercurrent to it. The cooled arterial blood...

Recent theories on integration between osmotic and volume regulation places the antidiuretic hormone (ADH) in a central position. In this paper we outline first the concepts of osmotic and volume regulation in higher vertebrates, second we describe our own experiments which test a crucial consequence of the hypothesis stated most clearly by Gauer5.

1. This study reports on osmotic and hormonal responses to heat and dehydration in birds. 2. Heat exposure did not affect the osmotic and hormonal status of normally hydrated fowls. 3. Dehydration for 48 h (normothermia, ca. 13% body weight loss) significantly (PP4. Upon recovery (30 min of drinking) the osmotic and hormonal responses were signific...

The osmolality and concentrations of Na, K, Cl and the hormones arginine vasotocin (AVT), prolactin, aldosterone and corticosterone were measured in plasma as functions of time in relation to oviposition, changing NaCl content of the diet, and feeding-inanition. AVT was significantly increased immediately after oviposition (but not during the hour...

This review surveys our latest research dealing with the involvement of arginine vasotocin (AVT), the avian antidiuretic hormone, and other hormones in the regulation of water and salt balance in fowl. We examined the effect of dehydration, salt loading, high- and low-salt diets, and oviposition on plasma hormone levels and analyzed them in light o...