nils-herrmann/clean_scirepeval huggingface dataset:
Effects of dietary fibre and protein on urea transport across the cecal mucosa of piglets
Venue: Journal of Comparative Physiology B

In ruminants, gastrointestinal recycling of urea is acutely enhanced by fibre-rich diets that lead to high ruminal concentration of short chain fatty acids (SCFA), while high ammonia has inhibitory effects. This study attempted to clarify if urea flux to the porcine cecum is similarly regulated. Thirty-two weaned piglets were fed diets containing protein (P) of poor prececal digestibility and fibre (F) at high (H) or low levels (L) in a 2 × 2 factorial design. After slaughter, cecal content was analyzed and the cecal mucosa incubated in Ussing chambers to measure the effect of pH, SCFA and NH4+ on the flux rates of urea, short-circuit current (Isc) and tissue conductance (Gt). NH4+ significantly enhanced Isc (from 0.5 ± 0.2 to 1.2 ± 0.1 μEq cm−2 h−1). No acute effects of SCFA or ammonia on urea flux were observed. Tissue conductance was significantly lower in the high dietary fibre groups irrespective of the protein content. Only the HP-LF group emerged as different from all others in terms of urea flux (74 ± 6 versus 53 ± 3 nmol cm−2 h−1), associated with higher cecal ammonia concentration and reduced fecal consistency. The data suggest that as in the rumen, uptake of ammonia by the cecum may involve electrogenic transport of the ionic form (NH4+). In contrast to findings in the rumen, neither a high fibre diet nor acute addition of SCFA enhanced urea transport across the pig cecum. Instead, a HP-LF diet had stimulatory effects. A potential role for urea recycling in stabilizing luminal pH is discussed.
Perception of floral volatiles involved in host-plant finding behaviour: comparison of a bee specialist and generalist
Venue: Journal of Comparative Physiology A

Specialist and generalist bees use olfactory and visual cues to find and recognise flowering plants. Specialised (oligolectic) bees rely on few host plants for pollen collection. These bee species are suggested to use specific volatiles, but it is unknown whether they have dedicated adaptations for these particular compounds compared to bees not specialised on the same plants. In the present study, we investigated the perception of host odorants and its neuronal substrate with regard to host-plant finding behaviour in oligolectic bees. We reconstructed the antennal lobes (AL) in the Salix specialist, Andrena vaga, and counted about 135 glomeruli and thereby less than the approximately 160 in honeybees. Using calcium imaging experiments to measure neural activity in the bee brain, we recorded odorant-evoked activity patterns in the AL of A. vaga and, for comparison, in the generalist honeybee, Apis mellifera. Our physiological experiments demonstrated that A. vaga bees were particularly sensitive to 1,4-dimethoxybenzene, a behaviour-mediating odorant of Salix host flowers. We found more sensitive glomeruli in the specialised bees as compared to generalist honeybees. This neural adaptation might allow oligolectic A. vaga bees to effectively locate host plants from distances.
The effect of ambient humidity on the foraging behavior of the hawkmoth Manduca sexta
Venue: Journal of Comparative Physiology A

The foraging decisions of flower-visiting animals are contingent upon the need of an individual to meet both energetic and osmotic demands. Insects can alter their food preferences to prioritize one need over the other, depending on environmental conditions. In this study, preferences in nectar sugar concentrations (0, 12, 24 %) were tested in the hawkmoth Manduca sexta, in response to different levels of ambient humidity (20, 40, 60, and 80 % RH). Moths altered their foraging behavior when placed in low humidity environments by increasing the volume of nectar imbibed and by consuming more dilute nectar. When placed in high humidity environments the total volume imbibed decreased, because moths consumed less from dilute nectars (water and 12 % sucrose). Survivorship was higher with higher humidity. Daily foraging patterns changed with relative humidity (RH): moths maximized their nectar consumption earlier, at lower humidities. Although ambient humidity had an impact on foraging activity, activity levels and nectar preferences, total energy intake was not affected. These results show that foraging decisions made by M. sexta kept under different ambient RH levels allow individuals to meet their osmotic demands while maintaining a constant energy input.
Insect–machine hybrid system for understanding and evaluating sensory-motor control by sex pheromone in Bombyx mori
Venue: Journal of Comparative Physiology A

To elucidate the dynamic information processing in a brain underlying adaptive behavior, it is necessary to understand the behavior and corresponding neural activities. This requires animals which have clear relationships between behavior and corresponding neural activities. Insects are precisely such animals and one of the adaptive behaviors of insects is high-accuracy odor source orientation. The most direct way to know the relationships between neural activity and behavior is by recording neural activities in a brain from freely behaving insects. There is also a method to give stimuli mimicking the natural environment to tethered insects allowing insects to walk or fly at the same position. In addition to these methods an ‘insect–machine hybrid system’ is proposed, which is another experimental system meeting the conditions necessary for approaching the dynamic processing in the brain of insects for generating adaptive behavior. This insect–machine hybrid system is an experimental system which has a mobile robot as its body. The robot is controlled by the insect through its behavior or the neural activities recorded from the brain. As we can arbitrarily control the motor output of the robot, we can intervene at the relationship between the insect and the environmental conditions.
Group recruitment in a thermophilic desert ant, Ocymyrmex robustior
Venue: Journal of Comparative Physiology A

Thermophilic desert ants—Cataglyphis, Ocymyrmex, and Melophorus species inhabiting the arid zones of the Palaearctic region, southern Africa and central Australia, respectively—are solitary foragers, which have been considered to lack any kind of chemical recruitment. Here we show that besides mainly employing the solitary mode of food retrieval Ocymyrmex robustior regularly exhibits group recruitment to food patches that cannot be exploited individually. Running at high speed to recruitment sites that may be more than 60 m apart from the nest a leading ant, the recruiter, is followed by a loose and often quite dispersed group of usually 2–7 recruits, which often overtake the leader, or may lose contact, fall back and return to the nest. As video recordings show the leader, while continually keeping her gaster in a downward position, intermittently touches the surface of the ground with the tip of the gaster most likely depositing a volatile pheromone signal. These recruitment events occur during the entire diurnal activity period of the Ocymyrmex foragers, that is, even at surface temperatures of more than 60 °C. They may provide promising experimental paradigms for studying the interplay of orientation by chemical signals and path integration as well as other visual guidance routines.
A vagal nerve branch controls swallowing directly in the seawater eel
Venue: Journal of Comparative Physiology B

By developing a new in vivo method to evaluate the esophageal closure, which reflects inhibition of swallowing, we demonstrate that the vagal X1 branch projected from the glossopharyngeal-vagal motor complex (GVC) controls the upper esophageal sphincter (UES) muscle directly. Although eel vagal nerve consisted of five branches, other branches (X2, X3, X4 and X5) did not influence the esophageal pressure. When the X1 nerve branch was stimulated electrically, the balloon pressure in the UES area increased with optimum frequency of 20 Hz. Since similar optimum frequency was observed both in the pithed eel and in the isolated UES preparation, such characteristic of X1 nerve is not due to anesthetic used during experiment. As the isolated UES preparation consists of muscle cells and nerve terminals, and as the optimum frequency of the nerve terminal is identical with that of the X1 branch, it is most likely that the X1 nerve branch is identical with the nerve terminals within the UES preparation. On the other hand, since the GVC neurons fire spontaneously at around 20 Hz, the optimum frequency of 20 Hz means that the eel UES is usually closed vigorously and relaxed only when the GVC neuron is inactivated. The effect of X1 stimulation was inhibited by curare, but not by atropine, indicating that the X1 nerve branch releases acetylcholine, which acts on the nicotinic receptor on the UES striated muscle. Beside vagal nerve X1 branch, spinal nerve SN2, SN3 and SN4 also contributed to the UES closure, but SN1 did not influence the UES movement. However, since the efficacy of these spinal nerve stimulations is about 1/10 of that by vagal X1 branch, the eel UES may be controlled primarily by a vagal nerve X1 branch, and secondarily by spinal nerves (SN2, SN3 and SN4).
Severe constraints for sound communication in a frog from the South American temperate forest
Venue: Journal of Comparative Physiology A

The efficiency of acoustic communication depends on the power generated by the sound source, the quality of the environment across which signals propagate, the environmental noise and the sensitivity of the intended receivers. Eupsophus calcaratus, an anuran from the temperate austral forest, communicates by means of an advertisement call of weak intensity in a sound-attenuating environment. To estimate the range over which these frogs communicate effectively, we conducted measurements of sound level and degradation patterns of propagating advertisement calls in the field, and measurements of auditory thresholds to pure tones and to natural calls in laboratory conditions. The results show that E. calcaratus produces weak advertisement calls of about 72 dB sound pressure level (SPL) at 0.25 m from the caller. The signals are affected by attenuation and degradation patterns as they propagate in their native environment, reaching average values of 61 and 51 dB SPL at 1 and 2 m from the sound source, respectively. Midbrain multi-unit recordings show a relatively low auditory sensitivity, with thresholds of about 58 dB SPL for conspecific calls, which are likely to restrict communication to distances shorter than 2 m, a remarkably short range as compared to other anurans.
Digestive strategies and food choice in mantled howler monkeys Alouatta palliata mexicana: bases of their dietary flexibility
Venue: Journal of Comparative Physiology B

Mantled howler monkeys (Alouatta palliata) occupy a wide variety of tropical habitats and are the most folivorous of New World primates. However, their diet may include fruits, buds, petioles, and flowers, as well as leaves, suggesting they must cope with variations in the nutrient composition of their food. We studied the physiological basis of the dietary flexibility of these monkeys by comparing food choice, digestive performance and patterns of digesta flow in six adults, fed diets of either leaves or a mixture of fruit and leaves. Although monkeys ate similar amounts of the two diets, they ingested more digestible protein when offered the leaf diet, on which they lost body mass, but they ingested much more soluble sugars when offered fruit and leaves on which they gained mass. Digestibilities of dry matter, fat, energy and fibre did not differ between diets, but those of crude protein, soluble sugars and minerals were higher on the fruit–leaf diet. Mean retention times in the gut of solute (Co-EDTA) and particulate markers (Cr-mordanted cell walls) did not differ between diets, but on both diets the monkeys retained the particulate marker (mean retention time ca 55 h) for longer than they did the solute marker (MRT ca 50 h). A lack of selective retention of solutes and small particles in the gastro-intestinal tract of howler monkeys probably restricts them to mixed diets but their digestive strategy is sufficiently flexible to allow them to feed on a diet of leaves when fruit is unavailable.
Liver glucose-6-phosphatase proteins in suckling and weaned grey seal pups: structural similarities to other mammals and relationship to nutrition, insulin signalling and metabolite levels
Venue: Journal of Comparative Physiology B

Phocid seals have been proposed as models for diabetes because they exhibit limited insulin response to glucose, high blood glucose and increasing insulin resistance when fasting. Liver glucose-6-phosphatase (G6Pase) catalyses the final step in glucose production and is central to glucose regulation in other animals. G6Pase comprises a translocase (SLC37A4) and a catalytic subunit (G6PC). G6PC and SLC37A4 expression and activity are normally regulated by nutritional state and glucostatic hormones, particularly insulin, and are elevated in diabetes. We tested the hypotheses that (1) grey seal G6PC and SLC37A4 cDNA and predicted protein sequences differ from other species’ at functional sites, (2) relative G6Pase protein abundances are lower during feeding than fasting and (3) relative G6Pase protein abundances are related to insulin, insulin receptor phosphorylation and key metabolite levels. We show that G6PC and partial SLC37A4 cDNA sequences encode proteins sharing 82–95 % identity with other mammals. Seal G6PC contained no differences in sites responsible for activity, stability or subcellular location. Several substitutions in seal SLC37A4 were predicted to be tolerated with low probability, which could affect glucose production. Suckling pups had higher relative abundance of both subunits than healthy, postweaned fasting pups. Furthermore, relative G6PC abundance was negatively related to glucose levels. These findings contrast markedly with the response of relative hepatic G6Pase abundance to feeding, fasting, insulin, insulin sensitivity and key metabolites in other animals, and highlight the need to understand the regulation of enzymes involved in glucose control in phocids if these animals are to be informative models of diabetes.
The breeding season duration hypothesis: acute handling stress and total plasma concentrations of corticosterone and androgens in male and female striped plateau lizards (Sceloporus virgatus)
Venue: Journal of Comparative Physiology B

Acute glucocorticoid elevations can be adaptations to short-term stressors. The breeding season hypothesis predicts reduced glucocorticoid responsiveness to acute stressors in populations or species with short breeding seasons. The striped plateau lizard (Sceloporus virgatus) has a short breeding season in Arizona. We measured plasma corticosterone and total androgen levels (dihydrotestosterone and testosterone) following one of the four stress-handling treatments (0, 10, 60, or 180 min). In both sexes, longer handling stress yielded higher corticosterone; females had higher corticosterone than males at all time points. Androgens did not vary with handling duration, in either sex. Combining treatments, plasma androgens correlated positively with corticosterone (CORT) in females but not in males; plasma CORT and body mass residuals were negatively correlated in both sexes, suggesting lizards in poor body condition and/or not investing heavily in reproduction (follicle mass) have higher acute corticosterone. Total plasma androgens and body mass residuals were positively associated in males, but showed no association in females. The maximal CORT elevation after handling stress in this single-clutching species was of comparable magnitude to responses in related multi-clutching lizard species with longer breeding seasons. Using data from studies of multiple populations of three Sceloporus species, we found no relationship between the relative magnitude of the CORT increase and either latitude or elevation, two variables in the literature correlated with duration of the breeding season, and only weak relationships with geographic elevation and actual (not relative) stress-elevated CORT values in this multi-population comparison.
Separating the contributions of vascular anatomy and blood viscosity to peripheral resistance and the physiological implications of interspecific resistance variation in amphibians
Venue: Journal of Comparative Physiology B

Amphibian pulmonary and systemic vascular circuits are arranged in parallel, with potentially important consequences for resistance (R) to blood flow. The contribution of the parallel anatomic arrangement to total vascular R (RT), independent of blood viscosity, is unknown. We measured pulmonary (RP) and systemic (RS) vascular R with an in situ Ringer’s solution perfusion technique using anesthetized anuran and urodele species to determine: (1) relative contributions of vascular anatomy and blood viscosity to RT; (2) distensibility index (%Δ flow kPa−1) of the pulmonary and systemic vascular circuits; and (3) interspecific correlates of variation in these parameters with red blood cell size, cardiac power output, and aerobic capacities. RP was lower than RS in anurans, while RP of the urodeles was greater than RS and significantly greater than anuran RP. Anuran RT was lowest and did not vary interspecifically, whereas urodele RT was significantly greater than anuran, and varied interspecifically. Pulmonary and systemic circuit distensibility differences may explain cardiac shunt patterns in toads with changes in cardiac output from rest to activity. When blood viscosity was taken into account, vascular resistance accounted for about 25 % of RT while blood viscosity accounted for the remaining 75 %. Owing to lower RT, terrestrial anuran species required lower cardiac power outputs when moving fluid through their vasculature compared to aquatic species. These results indicate that physical characteristics of the vasculature can account for interspecific differences in cardiovascular physiology and suggest a co-evolution of cardiac and vascular anatomy among amphibians.
Function of head-bobbing behavior in diving little grebes
Venue: Journal of Comparative Physiology A

Most birds show a characteristic head movement that consists of head stabilization and quick displacement. In this movement, which is analogous to saccadic eye movement in mammals, head stabilization plays an important role in stabilizing the retinal image. This head movement, called “head bobbing”, is particularly pronounced during walking. Previous studies focusing on anatomical and behavioral features have pointed out that visual information is also important for diving birds, indicating its significance in the head movements of diving birds. In the present study, the kinematic and behavioral features of head bobbing in diving little grebes were described by motion analysis to identify the head movement in diving birds. The results showed that head-bobbing stroke (HBS) consisted of a thrust phase and a hold phase as is typical for head bobbing during walking birds. This suggests that HBS is related to visual stabilization under water. In HBS, grebes tended to dive with longer stroke length and smaller stroke frequency than in non-bobbing stroke. This suggests that the behavior, which is related to vision, affects the kinematic stroke parameters. This clarification of underwater head movement will help in our understanding not only of vision, but also of the kinematic strategy of diving birds.
Energetics and metabolite profiles during early flight in American robins (Turdus Migratorius)
Venue: Journal of Comparative Physiology B

Although birds use fat as the primary fuel for migratory flights, carbohydrate and protein catabolism could be significant in the early stages of flight while pathways of fatty acid transport and oxidation are induced. The fuel mixture of long distance migrant birds can also be affected by the rate of water loss, where birds catabolize more protein to increase endogenous water production under dehydrating flight conditions. Despite many studies investigating flight metabolism, few have focused on the metabolic response to flight during the switchover to fat catabolism in migrants, and none have examined the effect of ambient conditions on fuel selection during early flight. We investigated the effect of water loss on the metabolic response to short duration flight in the American robin (Turdus migratorius). Birds were flown in a climatic wind tunnel and changes in body composition and plasma metabolites were measured. As flight duration increased, there was a gradual switchover from carbohydrate and protein catabolism to fat catabolism. Plasma metabolite profiles indicate that the mobilization of fat occurred within 20 min of initiating flight. Plasma glucose decreased and uric acid increased with flight duration. Ambient humidity did not affect fuel mixture. Thus, it seems that the utilization of fat may be delayed as migrants initiate flight. Short-hop migrants may exploit high rates of endogenous water production resulting from carbohydrate and protein catabolism early in flight to offset high water loss associated with low humidity. Rapid catabolism of lean body components at the start of a flight also reduces mass quickly, and may reduce energy costs.
Cattle on pastures do align along the North–South axis, but the alignment depends on herd density
Venue: Journal of Comparative Physiology A

Alignment is a spontaneous behavioral preference of particular body orientation that may be seen in various vertebrate or invertebrate taxa. Animals often optimize their positions according to diverse directional environmental factors such as wind, stream, slope, sun radiation, etc. Magnetic alignment represents the simplest directional response to the geomagnetic field and a growing body of evidence of animals aligning their body positions according to geomagnetic lines whether at rest or during feedings is accumulating. Recently, with the aid of Google Earth application, evidence of prevailing North–South (N–S) body orientation of cattle on pastures was published (Begall et al. PNAS 105:13451–13455, 2008; Burda et al.  2009). Nonetheless, a subsequent study from a different laboratory did not confirm this phenomenon (Hert et al. J Comp Physiol A 197:677–682, 2011). The aim of our study was to enlarge the pool of independently gained data on this remarkable animal behavior. By satellite snapshots analysis and using blinded protocol we scored positions of 2,235 individuals in 74 herds. Our results are in line with the original findings of prevailing N–S orientation of grazing cattle. In addition, we found that mutual distances between individual animals within herds (herd density) affect their N–S preference—a new phenomenon giving some insight into biological significance of alignment.