nils-herrmann/clean_scirepeval huggingface dataset:
Sources of Ca2+ for contraction of the heart tube of Tenebrio molitor (Coleoptera: Tenebrionidae)
Venue: Journal of Comparative Physiology B

Insect and vertebrate hearts share the ability to generate spontaneously their rhythmic electrical activity, which triggers the fluid-propelling mechanical activity. Although insects have been used as models in studies on the impact of genetic alterations on cardiac function, there is surprisingly little information on the generation of the inotropic activity in their hearts. The main goal of this study was to investigate the sources of Ca2+ for contraction in Tenebrio molitor hearts perfused in situ, in which inotropic activity was assessed by the systolic variation of the cardiac luminal diameter. Increasing the pacing rate from 1.0 to 2.5 Hz depressed contraction amplitude and accelerated relaxation. To avoid inotropic interference of variations in spontaneous rate, which have been shown to occur in insect heart during maneuvers that affect Ca2+ cycling, experiments were performed under electrical pacing at near-physiological rates. Raising the extracellular Ca2+ concentration from 0.5 to 8 mM increased contraction amplitude in a manner sensitive to L-type Ca2+ channel blockade by D600. Inotropic depression was observed after treatment with caffeine or thapsigargin, which impair Ca2+ accumulation by the sarcoplasmic reticulum (SR). D600, but not inhibition of the sarcolemmal Na+/Ca2+ exchanger by KB-R7943, further depressed inotropic activity in thapsigargin-treated hearts. From these results, it is possible to conclude that in T. molitor heart, as in vertebrates: (a) inotropic and lusitropic activities are modulated by the heart rate; and (b) Ca2+ availability for contraction depends on both Ca2+ influx via L-type channels and Ca2+ release from the SR.
The effects of embryonic hypoxic programming on cardiovascular function and autonomic regulation in the American alligator (Alligator mississippiensis) at rest and during swimming
Venue: Journal of Comparative Physiology B

Reptilian embryos naturally experience fluctuating oxygen levels in ovo, and developmental hypoxia has been established to have long-term impacts on cardiovascular function in vertebrates. In the present study, we investigated the impact of developmental 21% (normoxia) and 10% O2 (hypoxia) on juvenile (4-year-old) American alligator cardiovascular function in animals at rest and during swimming. In both experimental groups, combined right aortic and right subclavian blood flow approximately doubled during swimming. Carotid blood flow increased during swimming in the hypoxia-programmed animals only, and both carotid and left aortic blood flow reached higher values in swimming hypoxic-programmed animals compared to the normoxic group. However, pulmonary blood flow, which increased two to threefold during swimming (in both groups), was higher in normoxic-programmed animals at both rest and swimming. The differences between programming groups were preserved after cholinergic blockade (atropine), but reduced by adrenergic receptor antagonists (propranolol and phentolamine). Propranolol and phentolamine also blunted the incremental increases in blood flows during swimming, which was especially clear in the hypoxia-programmed animals. Alteration in adrenergic control and relative cardiac size (which was increased in hypoxic-programmed alligators) may account for the differences between the experimental groups.
Nitric oxide metabolites in hypoxia, freezing, and hibernation of the wood frog, Rana sylvatica
Venue: Journal of Comparative Physiology B

Nitric oxide (NO) is a gaseous free radical that in diverse organisms performs many signaling and protective functions, such as vasoregulation, inhibition of apoptosis, antioxidation, and metabolic suppression. Increased availability of NO may be especially important during life-history periods when organisms contend with multiple stresses. We investigated dynamics of the NO metabolites, nitrite (NO2−) and nitrate (NO3−), in the blood plasma, heart, liver, and skeletal muscle of the wood frog (Rana sylvatica), an amphibian that endures chronic cold, freezing, hypoxia, dehydration, and extended aphagia during hibernation. We found elevated concentrations of NO2− and/or NO3− in the plasma (up to 4.1-fold), heart (3.1-fold), and liver (up to 4.1-fold) of frogs subjected to experimental hypoxia (24 h, 4 °C), and in the liver (up to 3.8-fold) of experimentally frozen frogs (48 h, − 2.5 °C), suggesting that increased NO availability aids in survival of these stresses. During a 38-week period of simulated hibernation, NO2− and/or NO3− increased in the plasma (up to 10.4-fold), heart (up to 3.3-fold), and liver (5.0-fold) during an initial 5-week winter-acclimatization regimen and generally remained elevated thereafter. In hibernation, plasma NO2− was higher in frogs indigenous to Interior Alaska than in conspecifics from a temperate locale (southern Ohio), suggesting that NO availability is matched to the severity of environmental conditions prevailing in winter. The comparatively high NO availability in R. sylvatica, a stress-tolerant species, together with published values for other species, suggest that the NO protection system is of general importance in the stress adaptation of vertebrates.
Vestibular-related eye movements in the rat following selective electrical stimulation of the vestibular sensors
Venue: Journal of Comparative Physiology A

Rats are the most commonly used species in the neurosciences; however, little is known about the effects of selective electrical stimulation of individual vestibular sensors, on their eye movements. This limits their use to study the effects of vestibular stimulation on the brain, and their use in further exploring novel technologies such as artificial vestibular implants. We describe the effects of electrical stimulation of each vestibular sensor on vestibular-related eye movement in rats and compared the results to other species. We demonstrated that each sensor is responsible for specific bilateral eye movements. We found that the eye movements in rats differed from other species. Although the results were similar when stimulating the horizontal canal ampulla, differences appeared when stimulating the vertical canal sensors. During utricular stimulation, the ipsilateral eye moved dorsally in most cases, while the contralateral eye usually moved either caudally, or in extorsion. Saccular stimulation usually moved the ipsilateral eye dorsally or ventrally, while the contralateral eye usually moved ventrally or caudally. This study provides the first data on the application of selective electrical vestibular stimulation in the rat to the study of vestibular-related eye movements.
Olfactory sensitivity for mold-associated odorants in CD-1 mice and spider monkeys
Venue: Journal of Comparative Physiology A

Using operant conditioning procedures, we assessed the olfactory sensitivity of six CD-1 mice and three spider monkeys for mold-associated odorants. We found that with all eight stimuli, the mice detected concentrations as low as 0.1 ppm (parts per million), and with two of them individual animals even detected concentrations as low as 1 ppt (parts per trillion). The spider monkeys detected concentrations as low as 4 ppm with all eight stimuli, and with four of them individual animals even detected concentrations as low as 4 ppb (parts per billion). Between-species comparisons showed that with all eight odorants, the mice displayed significantly lower threshold values, that is, a higher sensitivity than the spider monkeys, but not than human subjects tested in previous studies. Analysis of odor structure–activity relationships showed that in both species, the type of oxygen-containing functional group and the presence versus absence of a double bond as well as the length of the carbon backbone of the odor stimuli had a systematic effect on detectability. We conclude that both mice and spider monkeys are clearly able to detect the presence of molds and thus to assess the palatability of potential food using the volatiles produced by molds during putrefaction.
Individual variation of daily torpor and body mass change during winter in the large Japanese field mouse (Apodemus speciosus)
Venue: Journal of Comparative Physiology B

Daily torpor is a strategy used by some overwintering small endotherms to aid in energy conservation. However, the pattern of torpor varies among individuals within species and populations, even under the same environmental conditions, with significant implications for survival rate and reproductive success. Body mass is one factor that may influence this variation, especially in some small mammals that accumulate fat stores prior to overwintering. However, to our knowledge there has been no previous study examining the detailed relationships between torpor expression and body mass change in small mammals that hoard food as an energy resource during winter. The large Japanese field mouse, Apodemus speciosus, whose winter survival strategy depends on food caches instead of fat stores, displays daily torpor under artificial winter conditions (short-day photoperiod and cold). The present study clarifies the characteristics and patterns of daily torpor and body mass change in this species in the laboratory. Although expression of daily torpor was facilitated progressively as in other species, the observed patterns of torpor expression and body mass change showed considerable individual variation. Moreover, there was no obvious correlation between body mass and daily torpor expression. Therefore, it is suggested that in A. speciosus body mass may not contribute to individual variation of daily torpor during winter. Daily torpor during winter may be adjusted by not only mechanisms common to other small mammals, but also species-specific factors relating to the external or internal reserves of energy in small mammals.
The springtail Megaphorura arctica survives extremely high osmolality of body fluids during drought
Venue: Journal of Comparative Physiology B

The springtail Megaphorura arctica Tullberg 1876 is widespread in the arctic and subarctic regions where it can be abundant along beaches. This species survives winters using cryoprotective dehydration as a cold tolerance strategy during which it becomes drastically dehydrated. Several studies have investigated the physiological responses associated with water loss of M. arctica under exposure to freezing temperatures, but little is known of the dynamics of body water and hemolymph osmolality when subjected to gradually increasing drought stress at temperatures above the freezing point. Therefore, an experiment was conducted in which M. arctica was subjected to relative humidities (RH) decreasing from fully saturated conditions to ca. 89%RH over a period of 30 days. During the experiment water content of springtails decreased from about 3 to ca. 0.5 mg mg−1 dry weight. Alongside with water loss, trehalose concentrations increased from nearly nothing to 0.12 mg mg−1 dry weight, which contributed to an increase in hemolymph osmolality from ca. 250 mOsm to at least 7 Osm. All springtails survived water loss down to 0.7 mg mg−1 dry weight and hemolymph osmolality of ca. 4 Osm, and about 60% of the springtails survived with only 0.5 mg water mg−1 dry weight and osmolality of ca. 7 Osm. At this level of dehydration, Differential Scanning Calorimetry analysis showed that most, but not all, osmotically active water was lost. It is discussed that the extensive dehydration must be associated with high concentrations of salts potentially causing denaturation and precipitation of cellular proteins. M. arctica is remarkably tolerant of dehydration, but because it does not endure loss of the osmotically inactive water it cannot be categorized as a truly anhydrobiotic species.
Behavioural responses to environmental hypercapnia in two eusocial species of African mole rats
Venue: Journal of Comparative Physiology A

Damaraland and naked mole rat are eusocial mammals that live in crowded burrows in which CO2 is elevated. These species are thought to be highly tolerant of CO2 but their behavioural responses to hypercapnia are poorly understood. We hypothesized that Damaraland and naked mole rats would exhibit blunted behavioural responses to hypercapnia and predicted that their activity levels would be unaffected at low to moderate (2–5%) CO2 but increased at > 7% CO2. To test this, we exposed Damaraland and naked mole rats to stepwise increases in environmental CO2 (0–10%) and measured activity, exploratory behaviour, and body temperature. Surprisingly, we found that both species exhibited no differences in movement velocity, distance travelled, zone transitions (exploration), or body temperature at any level of environmental hypercapnia. Conversely, when carbonic anhydrase was inhibited with acetazolamide (50 mg kg−1 intraperitonially, to increase whole-animal acidosis), exploration was significantly elevated relative to hypercapnic controls in both species at all levels of inhaled CO2, and naked mole rat body temperature decreased in > 7% CO2. We conclude that both species are largely non-responsive to environmental CO2, and that this tolerance may be dependent on bicarbonate buffering at the level of the kidney or within the blood.
Effects of pars intercerebralis removal on circatidal rhythm in the mangrove cricket, Apteronemobius asahinai
Venue: Journal of Comparative Physiology A

The circatidal rhythm is an endogenous rhythm corresponding to the tidal cycles, and its neural mechanism remains unknown. The mangrove cricket, Apteronemobius asahinai, possesses both circatidal and circadian clocks, and simultaneously exhibits circatidal and circadian rhythms in its locomotor activity. In a previous study, we showed that surgical removal of the optic lobes, the principal circadian clock locus in crickets, disrupted their circadian rhythm, but not their circatidal rhythm. In this study, we focused on the pars intercerebralis (PI) because surgical removal of the PI disrupts the circadian rhythm and causes arrhythmic activity in some cricket species. After surgical removal of the PI, the proportion of crickets displaying circatidal rhythm decreased, and more than half of the crickets exhibited arrhythmic activity. Surgical removal of the regions around the PI also caused a similar effect on locomotor activity. Our results indicate that the PI and/or its surrounding regions are important not only for circadian but also for circatidal rhythm. This suggests the presence of a neural or hormonal pathway in the PI and/or its surrounding regions that is common to the circatidal and circadian rhythms.
What does a butterfly hear? Physiological characterization of auditory afferents in Morpho peleides (Nymphalidae)
Venue: Journal of Comparative Physiology A

Many Nymphalidae butterflies possess ears, but little is known about their hearing. The tympanal membrane of butterflies typically comprises distinct inner and outer regions innervated by auditory nerve branches NII and NIII and their respective sensory organs. Using the Blue Morpho butterfly (Morpho peleides) as a model, we characterized threshold and suprathreshold responses of NII and NIII. Both are broadly tuned to 1–20 kHz with best frequencies at 1–3 kHz, but NIII is significantly more sensitive than NII. The compound action potentials (CAPs) of both branches increase their first peak amplitudes and areas in response to higher sound levels. NII and NIII differed in their suprathreshold CAP responses to sound frequencies, with stronger responses to 1–3 and 4–6 kHz, for NIII and NII respectively; results that are consistent with tympanal membrane mechanics. These results indicate that butterflies are capable of amplitude and frequency discrimination. Both auditory branches responded to playbacks of the flight and calls of predatory birds. We propose that the ears of butterflies, like those of many vertebrate prey such as some rabbits and lizards, function primarily in predator risk assessment.
Short and hyperthermic torpor responses in the Malagasy bat Macronycteris commersoni reveal a broader hypometabolic scope in heterotherms
Venue: Journal of Comparative Physiology B

The energy budgets of animal species are closely linked to their ecology, and balancing energy expenditure with energy acquisition is key for survival. Changes in animals’ environments can be challenging, particularly for bats, which are small endotherms with large uninsulated flight membranes. Heterothermy is a powerful response used to cope with changing environmental conditions. Recent research has revealed that many tropical and subtropical species are heterothermic and display torpor with patterns unlike those of “classical” heterotherms from temperate and arctic regions. However, only a handful of studies investigating torpor in bats in their natural environment exist. Therefore, we investigated whether the Malagasy bat Macronycteris commersoni enters torpor in the driest and least predictable region in Madagascar. We examined the energy balance and thermal biology of M. commersoni in the field by relating metabolic rate (MR) and skin temperature (Tskin) measurements to local environmental characteristics in the dry and rainy seasons. Macronycteris commersoni entered torpor and showed extreme variability in torpor patterns, including surprisingly short torpor bouts, lasting on average 20 min, interrupted by MR peaks. Torpid MR was remarkably low (0.13 ml O2 h−1 g−1), even when Tskin exceeded that of normothermia (41 °C). Macronycteris commersoni is thus physiologically capable of (1) entering torpor at high ambient temperature and Tskin and (2) rapidly alternating between torpid and normothermic MR resulting in very short bouts. This suggests that the scope of hypometabolism amongst heterothermic animals is broader than previously assumed and underlines the importance of further investigation into the torpor continuum.
Travelling waves and tonotopicity in the inner ear: a historical and comparative perspective
Venue: Journal of Comparative Physiology A

In the 1940s, Georg von Békésy discovered that in the inner ear of cadavers of various vertebrates, structures responded to sound with a displacement wave that travels in a basal-to-apical direction. This historical review examines this concept and sketches its rôle and significance in the development of the research field of cochlear mechanics. It also illustrates that this concept and that of tonotopicity necessarily correlate, in that travelling waves are consequences of the existence of an ordered, longitudinal array of receptor cells tuned to systematically changing frequencies along the auditory organ.
Body and organ metabolic rates of a cave fish, Triplophysa rosa: influence of light and ontogenetic variation
Venue: Journal of Comparative Physiology B

Triplophysa rosa is a typical species of cave-dwelling fish distributed throughout Wulong County, Chongqing, China. This study aimed to test whether T. rosa has a low metabolic level as a cave species and how the metabolic rate of this fish responds to light stimulation. The whole body and organ (including brain, heart, and liver) oxygen consumption rates ($${\dot {m}_{{{\text{O}}_{\text{2}}}}}$$m˙O2) and several blood parameters related to oxygen carrying were compared between T. rosa acclimated in constant dark and those in regular photoperiod conditions. No significant changes in any variables were observed between the regular photoperiod fish and the dark fish, suggesting that the metabolic consumption of T. rosa is not light sensitive, which may be attributed to the highly degraded eyes of this cave species. The average mass-specific resting $${\dot {m}_{{{\text{O}}_{\text{2}}}}}$$m˙O2 of T. rosa was 38.3 mgO2 kg− 1 h− 1 and was lower than many other fish species. One possible explanation for the low metabolic level of T. rosa can be due to its highly degraded eyes and small brain size. Whole-organ $${\dot {m}_{{{\text{O}}_{\text{2}}}}}$$m˙O2 of the brain, heart, and liver were on average responsible for 8.18%, 3.55%, and 8.61% of the body resting $${\dot {m}_{{{\text{O}}_{\text{2}}}}}$$m˙O2, respectively. Both heart mass and liver mass increased with increasing body mass; however, brain mass did not correlate with body mass. Maintaining a small brain size throughout ontogeny suggests energy-saving advantages for this cave species.
The energetics and thermoregulation of water collecting honeybees
Venue: Journal of Comparative Physiology A

Honeybees need water for different purposes, to maintain the osmotic homeostasis in adults as well as to dilute stored honey and prepare liquid food for the brood. Water is also used for cooling of the hive. Foraging in endothermic insects is energy-intensive and the question arises how much energy bees invest in a resource without any metabolically usable energy. We investigated the energy demand of water collecting bees under natural conditions. The thermoregulation and energetic effort was measured simultaneously in a broad range of experimental ambient temperatures (Ta = 12–40 °C). The thorax temperature as well as the energetic turnover showed a great variability. The mean Tthorax was ranging from ~ 35.7 °C at 12 °C to nearly 42.5 °C at 40 °C. The energy turnover calculated from CO2-release was highest at a Ta of 20 °C with about 60 mW and lowest at 40 °C with about 22 mW per bee. The total costs during collection decreased from 10.4 J at 12 °C to 0.5 J at 40 °C. The energetic effort of the water collectors was comparable with that of 0.5 M sucrose foraging bees. Our investigation strongly supports the hypothesis that the bees’ motivational status determines the energetic performance during foraging.
Soluble calcium-binding proteins (SCBPs) of the earthworm Lumbricus terrestris: possible role as relaxation factors in muscle
Venue: Journal of Comparative Physiology B

The soluble Ca2+-binding protein (SCBP) from the earthworm Lumbricus terrestris was analyzed with regard to its role as a soluble muscle relaxation factor. The actomyosin ATPase activity was inhibited by the addition of decalcified SCBP as it binds Ca2+ stronger than the regulatory proteins associated with the actomyosin. Competitive 45Ca2+-binding assays with decalcified actomyosin and SCBP showed that 45Ca2+ is first bound to actomyosin and is subsequently taken over by SCBP with increasing incubation time. Ca2+ competition experiments carried out with 45Ca2+ loaded SCBP and fragmented sarcoplasmic reticulum vesicles revealed that 45Ca2+ bound to SCBP can be deprived by the ATP-dependent Ca2+ uptake of the sarcoplasmic reticulum. Furthermore, experiments in a diffusion chamber showed that the addition of SCBP significantly enhances the 45Ca2+ flux in a concentration dependent manner. The amount of the Ca2+ flux increase tends to reach a maximum value of about 70%. With all protein components isolated from the obliquely striated muscle, our in vitro experiments consistently show that SCBP may accelerate muscle relaxation similar as assumed for vertebrate parvalbumin.