bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of temperature and aquaticPO2 on the physiology and behaviour ofApalone feroxandChrysemys picta
Authors: Prassack S. L. , Bagatto B. , Henry R. P. 
Published: April 2021

SUMMARYSoftshell turtles overwinter in the same bodies of water as some emydids, but their reduced shell and increased non-pulmonary gas exchange may contribute to a different mechanism of overwintering. The dynamics of bimodal respiration, diving behaviour and blood acid–base status in Apalone ferox and Chrysemys picta were investigated under two different temperatures combined with three different aquatic PO2 levels. Both species obtained oxygen through pulmonary and non-pulmonary routes. Apalone ferox obtained more oxygen through non-pulmonary routes and increased its non-pulmonary V̇.O2 in response to both higher aquatic PO2 and lower temperatures. Both species increased pulmonary V̇.O2 in response to higher temperatures. As a consequence of the greater reliance of A. ferox on pulmonary V̇.O2, warmer temperatures caused plasma PCO2 and [HCO3−1] values to increase significantly compared with C. picta. Apalone ferox, which is efficient at bimodal respiration, displayed a high degree of plasticity with respect to both its respiratory and acid–base profiles, behaving more like an aquatic air-breathing fish in bimodal respiration at low temperature and more like a terrestrial air-breather at high temperature. Chrysemys picta, which is poor at bimodal respiration, was highly dependent on aerial gas exchange at both temperatures. Aquatic PO2 did not change any of the behavioural variables measured. At warm temperatures, A. ferox met O2 demands by increasing the rate of lung ventilation, which resulted in a significantly greater number of breathing bouts per hour and breaths per emersion period. However, the number of breaths per bout was not affected by temperature. As temperatures decreased, A. ferox utilized its non-pulmonary respiration ability and significantly increased its dive duration. Apalone ferox became less active at colder temperatures by significantly increasing the duration of inactive periods (from 4 to 18min) and by significantly decreasing the frequency of activity bursts. Chrysemys picta also met the higher gas-exchange demands associated with increased temperature by increasing the rate of lung ventilation; however, this increase was not as large as that measured in A. ferox. Chrysemys picta displayed multiple rhythmic breaths per bout. These results indicate that, unlike aquatic PO2, temperature is an important factor in the regulation of diving and ventilatory behaviour in turtles. The species responded to temperature in dissimilar ways because of differences in their bimodal respiration ability.
Fast muscle function in the European eel (Anguilla anguillaL.) during aquatic and terrestrial locomotion
Authors: Ellerby D. J. , Spierts I. L. Y. , Altringham J. D. 
Published: April 2021

SUMMARYEels are capable of locomotion both in water and on land using undulations of the body axis. Axial undulations are powered by the lateral musculature. Differences in kinematics and the underlying patterns of fast muscle activation are apparent between locomotion in these two environments. The change in isometric fast muscle properties with axial location was less marked than in most other species. Time from stimulus to peak force (Ta) did not change significantly with axial position and was 82±6ms at 0.45BL and 93±3ms at 0.75BL, where BL is total body length. Time from stimulus to 90% relaxation (T90) changed significantly with axial location, increasing from 203±11ms at 0.45BL to 239±9ms at 0.75BL. Fast muscle power outputs were measured using the work loop technique. Maximum power outputs at ±5% strain using optimal stimuli were 17.3±1.3Wkg−1 in muscle from 0.45BL and 16.3±1.5Wkg−1 in muscle from 0.75BL. Power output peaked at a cycle frequency of 2Hz. The stimulus patterns associated with swimming generated greater force and power than those associated with terrestrial crawling. This decrease in muscle performance in eels may occur because on land the eel is constrained to a particular kinematic pattern in order to produce thrust against an underlying substratum.
Function of the oblique hypaxial muscles in trotting dogs
Authors: Fife Mathew M. , Bailey Carmen L. , Lee David V. , Carrier David R. 
Published: April 2021

SUMMARYIn trotting dogs, the pattern of activity of the obliquely oriented hypaxial muscles is consistent with the possible functions of (i) stabilization against vertical accelerations that cause the trunk to sag in the sagittal plane and (ii) stabilization against forces that tend to shear the trunk in the sagittal plane. To test these hypotheses, we compared the amount of activity of the intercostal and abdominal oblique muscles (i) when dogs carried additional mass (8–15% of body mass) supported over the limb girdles versus supported mid-trunk (test of sagittal bounce), and (ii) when dogs trotted up versus down a 10° slope (test of sagittal shear). In response to the loading manipulations, only the internal oblique muscle responded in a manner that was consistent with stabilization of the trunk against forces that cause the trunk to sag sagittally. In contrast, when the fore–aft forces were manipulated by running up- and downhill, all four of the monitored muscles changed their activity in a manner consistent with stabilization of the trunk against sagittal shearing. Specifically, muscles with a craniodorsal orientation (external oblique and external intercostal muscles) showed an increase in activity when the dogs ran downhill and a decrease when they ran uphill. Muscles with a cranioventral orientation (internal oblique and internal intercostal muscles) exhibited the opposite pattern: increased activity when the dogs ran uphill and decreased activity when they ran downhill. Changes in activity of two extrinsic appendicular muscles, the serratus ventralis and deep pectoralis, during uphill and downhill running were also consistent with the sagittal shearing hypothesis. In contrast, changes in the level of recruitment of the oblique hypaxial muscles were not consistent with stabilization of the trunk against torques that induce yaw at the girdles. Hence, we suggest that the oblique hypaxial muscles of trotting dogs act to stabilize the trunk against sagittal shearing torques induced by limb retraction (fore–aft acceleration) and protraction (fore–aft deceleration).
Polarization analysis in the crayfish visual system
Authors: Glantz Raymon M. 
Published: April 2021

SUMMARY
It is proposed that polarization sensitivity at the most peripheral stages of the crayfish visual system (lamina ganglionaris and medulla externa) is used to enhance contrast and thus may contribute to motion detection in low contrast environments. The four classes of visual interneurons that exhibit polarization sensitivity (lamina monopolar cells, tangential cells, sustaining fibers and dimming fibers) are not sensitive exclusively to polarized light but also respond to unpolarized contrast stimuli. Furthermore, many of these cells and the sustaining fibers in particular exhibit a greater differential e-vector responsiveness to a changing e-vector than to e-vector variations among steady-state stimuli. While all four cell types respond modestly to light flashes at an e-vector of 90° to the preferred orientation, the dynamic response to a changing e-vector is small or absent at this orientation. Because the sustaining fibers exhibit polarization sensitivity, and they provide afferent input to a subset of optomotor neurons, the latter were also tested for polarization sensitivity. The optomotor neurons involved in compensatory reflexes for body pitch were differentially sensitive to the e-vector angle of a flash of light, with maximum responses for e-vectors near the vertical. The motor neurons also exhibited a maximum response near the vertical e-vector to a continuously rotating polarizer. Two scenarios are described in which the sensitivity to a changing e-vector can produce motion responses in the absence of intensity contrast.
Microspectrophotometric measurements of vertebrate photoreceptors using CCD-based detection technology
Authors: Hawryshyn Craig W. , Haimberger Theodore J. , Deutschlander Mark E. 
Published: April 2021

SUMMARY
We have developed a charge-coupled-device (CCD)-based microspectrophotometer (MSP) system and provide the first report on the successful employment of this technology to measure the spectral absorbance properties of vertebrate photoreceptors. The principal difference between the CCD-based MSP system and wavelength-scanning MSP systems, commonly used in vision biology, is that a short duration (800–1200ms), broad-spectrum flash is employed rather than ascending and descending wavelength scanning. Data acquisition is thus significantly faster, with the added possible advantages of less variance due to movement of target photoreceptors during measurement, reduced spectral distortion due to photoproduct interference and an ability to measure fast, transient changes in absorbance as bleaching proceeds. Rainbow trout photoreceptors, previously measured with a wavelength-scanning MSP system, were again measured using the CCD-based MSP system. Our analysis of optical recordings from 102 photoreceptors corroborated data obtained previously with rainbow trout photoreceptors on λmax (wavelength of maximum absorbance), Amax (maximum absorbance) and half maximum bandwidth (HBW) of ultraviolet-, blue-, green- and red-sensitive cones and rods. There were slight differences in λmax and half-maximum bandwidth of the ultraviolet-, blue- and green-sensitive cone classes, but this was most probably due to variation in the A1:A2 visual pigment ratio of the trout used in the two different studies. However, we were capable of resolving the A1 and A2 visual pigment spectra in the red-sensitive cones and the rods.
Avian ultraviolet vision and frequency-dependent seed preferences
Authors: Church Stuart C. , Merrison Annabel S. L. , Chamberlain Toby M. M. 
Published: April 2021

SUMMARYIt is well established that ultraviolet sensitivity plays an important role in the visually guided behaviour of birds. From a foraging perspective, evidence now exists that ultraviolet wavelengths are used by birds when foraging for insects, berries, seeds and mammals. Here, we present the results of two laboratory experiments that test the effect of removing (i) ultraviolet wavelengths and (ii) wavebands in the human-visible region on the frequency-dependent seed preferences of zebra finches (Taeniopygia guttata). Although the seeds and backgrounds used in our experiments reflected mainly at long wavelengths, we found that removal of ultraviolet wavelengths significantly changed the strength and direction of frequency dependence compared with full-spectrum illumination. We also found that the removal of ultraviolet wavelengths (300–400nm) did not affect the strength of frequency dependence compared with the removal of short wavelengths (approximately 400–500nm), medium wavelengths (approximately 500–600nm) or long wavelengths (approximately 600–700nm). Since frequency-dependent selection has direct consequences for the stability of prey populations and the spectral quality of ambient light is known to vary considerably with climate, time of day and local habitat geometry, our results suggest that ultraviolet wavelengths might play an important role in the dynamics of plant populations. However, we urge caution about overestimating the importance of ultraviolet wavelengths compared with wavelengths in the human-visible spectrum.
Is the ultraviolet waveband a special communication channel in avian mate choice?
Authors: Hunt Sarah , Cuthill Innes C. , Bennett Andrew T. D. , Church Stuart C. , Partridge Julian C. 
Published: April 2021

SUMMARYThere is growing evidence that ultraviolet (UV) wavelengths play an important role in avian mate choice. One of the first experiments to support this idea showed that female zebra finches (Taeniopygia guttata) prefer UV-reflecting males to males whose ultraviolet reflection has been removed. The effect was very strong despite little or no UV reflection from several plumage areas. However, it is not clear how the importance of the UV waveband compares to other regions of the bird-visible spectrum. We tested whether the response of female zebra finches to the removal of male UV reflection is greater than to the removal of other wavebands. We presented females with a choice of males whose appearance was manipulated using coloured filters. The filters removed single blocks of the avian visible spectrum corresponding closely to the spectral sensitivities of each of the zebra finch’s single cone classes. This resulted in males that effectively had no UV (UV−), no short-wave (SW−), no medium-wave (MW−) or no long-wave (LW−) plumage reflection. Females preferred UV− and SW− males. LW− and MW− males were least preferred, suggesting that female zebra finches show the greatest response to the removal of longer wavelengths. Quantal catches of the single cone types viewing body areas of the male zebra finch are presented for each treatment. Our study suggests it is important to consider the role of the UV waveband in avian mate choice in conjunction with the rest of the avian visible spectrum.
Topography of different photoreceptor cell types in the larval retina of Atlantic halibut (Hippoglossus hippoglossus)
Authors: Helvik Jon Vidar , Drivenes Øyvind , Harboe Torstein , Seo Hee-Chan 
Published: April 2021

SUMMARYThe identities of single cone cells in the retina of Atlantic halibut (Hippoglossus hippoglossus) larvae were studied by in situ hybridisation using RNA probes for the five different halibut opsins. Four different cone opsins (ultraviolet-, blue-, green- and red-sensitive) are expressed in Atlantic halibut at the end of the yolk-sac period, whereas rod opsin is expressed later in development. Photoreceptor cells expressing ultraviolet-sensitive opsin are found only in the ventral retina, presumably to optimise detection of the downwelling ultraviolet light. The majority of the photoreceptors (approximately 90%) in the retina express green-sensitive opsin and its distribution shows no regional differences. In contrast, blue- and red-sensitive opsins are expressed much less frequently (in approximately 10% of photoreceptors), although these two opsins are also found over the entire retina. The expression patterns of the different visual pigments indicate some form of mosaic expression in the single-coned larval retina, and this is reminiscent of the square mosaic expression found in post-metamorphic Atlantic halibut. These findings suggest plasticity in green-opsin-expressing cells during development, resulting in a square mosaic expression pattern.
Polarization vision – a uniform sensory capacity?
Authors: Wehner Rüdiger 
Published: April 2021

SUMMARYIn this concept paper, three scenarios are described in which animals make use of polarized light: the underwater world, the water surface and the terrestrial habitat vaulted by the pattern of polarized light in the sky. Within these various visual environments, polarized light is used in a number of ways that make quite different demands on the neural circuitries mediating these different types of behaviour. Apart from some common receptor and pre-processing mechanisms, the underlying neural mechanisms may differ accordingly. Often, information about χ (the angle of polarization), d (the degree of polarization) and λ (the spectral content) might not – and need not – be disentangled. Hence, the hypothesis entertained in this account is that polarization vision comes in various guises, and that the answer to the question posed in the title is most probably no.
Selective adaptation to noxious foods by a herbivorous insect
Authors: Glendinning John I. , Domdom Stephanie , Long Eliza 
Published: April 2021

SUMMARYWhen animals repeatedly sample a noxious food over a period of 1–4 days, they can markedly reduce their aversive behavioral response to the diet’s unpleasant taste (e.g. ‘bitterness’) or toxic effects. This long-term adaptation process is selective, however, permitting insects to adapt physiologically to some but not all noxious foods. We hypothesized (i) that the selective nature of this adaptation process stems from the fact that some unpalatable foods are toxic while others are harmless and (ii) that insects have more difficulty adapting to foods that are both unpalatable and toxic. Our model system consisted of Manduca sexta caterpillars and two compounds that taste bitter to humans and elicit an aversive behavioral response in this insect (salicin and aristolochic acid). We found that 2 days of exposure to a salicin diet completely adapted the aversive response of the caterpillars to salicin, but that exposure to an aristolochic acid diet failed to adapt the aversive response to aristolochic acid. We determined that M. sexta could not adapt to the aristolochic acid diet because it lacked mechanisms for reducing the compound’s toxicity. In contrast, the salicin diet did not produce any apparent toxic effects, and the caterpillars adapted to its aversive taste within 12 h of exposure. We also found that the salicin adaptation phenomenon (i) was mediated by the central gustatory system, (ii) generalized to salicin concentrations that were twice those in the adapting diet and (iii) offset spontaneously when the caterpillar was transferred to a salicin-free diet. We propose that toxicity is a more significant barrier to dietary adaptation than ‘bitterness’ in this insect.
Detection of Prey in a Cluttered Environment by the Northern Bat Eptesicus Nilssonii
Authors: Jensen Marianne Egebjerg , Miller Lee A. , Rydell Jens 
Published: April 2021

ABSTRACT
We studied the acoustic behaviour of bats (Eptesicus nilssonii) hunting for large (wing span 5 cm) non-hearing hepialid moths (Hepialus humuli). Groups of silvery-white male H. humuli perform a short (30 min) hovering display flight over grassland at dusk. They typically hover at, or below, the tops of grass panicles and are therefore situated in a highly acoustically cluttered habitat. Occasionally, they move to a new position by making short (1–5 s) flights at higher levels. E. nilssonii is not a clutter specialist, and yet we found that they attacked H. humuli within the ‘clutter overlap zone’. The bats did not change their signal design in any marked manner for this specific task. Measurements of echoes from a moth 10 cm above or below the grass tops showed that information for detecting the moths was available to the bats. Nevertheless, the bats did not attack moths in stationary hovering display flight, only when they moved above the grass panicles. The duration of the up/down flights (movements) were almost always longer than an entire capture sequence by the bats. Apparently, the bats rely on the movement of the moth in space, monitored over successive echoes, to discriminate moth echoes from overlapping clutter echoes.
Heterogeneity of Myoglobin Distribution in the Locomotory Muscles of Five Cetacean Species
Authors: Polasek L. K. , Davis R. W. 
Published: April 2021

ABSTRACT
Myoglobin is an important storage site for oxygen in the swimming muscles of diving marine mammals. However, little is known about its distribution within muscles since previous studies have relied on single samples. The goal of this study was to determine the distribution of myoglobin within the swimming muscles of five species of cetacean: dusky dolphin, false killer whale, striped dolphin, humpbacked dolphin and bottlenose dolphin. The entire dorsal (epaxial) and ventral (hypaxial) swimming muscles were removed from each animal and weighed. Transverse sections were taken from the cranial, middle and caudal regions of each muscle and sampled along a circular grid with a minimum of 30 sites per section. Spectrophotometric analysis was used to measure the myoglobin concentration of each sample. Contour maps of myoglobin concentration were made for each transverse section. Myoglobin concentration was found to be non-uniformly distributed within the muscle. The interior of the muscle lying closest to the vertebrae showed a significantly higher (11 %) mean myoglobin concentration than the exterior of the muscle for all five species. In the epaxial muscles, the mean myoglobin concentration was significantly higher in the caudal region closest to the flukes. The two deep-water species (false killer whale and striped dolphin) had significantly higher myoglobin concentrations than the three species (dusky, humpbacked and bottlenose dolphins) that occur in shallow, coastal waters. These results show that myoglobin is not homogeneously distributed in the locomotory muscle of cetaceans and that levels may be highest in those areas that produce greater force and consume more oxygen during aerobic swimming. Enhancing oxygen stores in those areas of the muscle that work the hardest would theoretically lengthen the aerobic dive limit of the animal during submerged swimming.
Enhanced Xenobiotic Transporter Expression In Normal Teleost Hepatocytes: Response To Environmental And Chemotherapeutic Toxins
Authors: Albertus Julie A. , Laine Roney O. 
Published: April 2021

ABSTRACT
Many aquatic organisms are resistant to environmental pollutants, probably because their inherent multi-drug-resistant protein extrusion pump (pgp) can be co-opted to handle man-made pollutants. This mechanism of multixenobiotic resistance is similar to the mechanism of multidrug resistance exhibited in chemotherapy-resistant human tumor cells. In the present study, a variety of techniques were used to characterize this toxin defense system in killifish (Fundulus heteroclitus) hepatocytes. The cellular localization and activity of the putative drug efflux system were evaluated. In addition, in vitro and in vivo studies were used to examine the range of expression of this putative drug transporter in the presence of environmental and chemotherapeutic toxins. The broad range of pgp expression generally observed in transformed mammalian cells was found in normal cells of our teleost model. Our findings suggest that the expression of the pgp gene in the killifish could be an excellent indicator of toxin levels or stressors in the environment.