bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of incline and speed on the three-dimensional hindlimb kinematics of a generalized iguanian lizard (Dipsosaurus dorsalis)
Authors: Jayne Bruce C. , Irschick Duncan J. 
Published: April 2021

ABSTRACT
Lizards commonly move on steep inclines in nature, but no previous studies have investigated whether the kinematics of the limbs of lizards differ on inclined surfaces compared with level surfaces. Therefore, we examined how the kinematics of the hindlimb were affected by both incline (downhill 30°, level and uphill 30°) and different speeds of steady locomotion (50–250 cm s−1) in the morphologically generalized iguanian lizard Dipsosaurus dorsalis. On the uphill surface, the strides of lizards were shorter and quicker than those at a similar speed on the level and downhill surfaces. A multivariate analysis revealed that the kinematics of locomotion on all three inclines were distinct, but several kinematic features of locomotion on the downhill surface were especially unique.
For example, downhill locomotion had the lowest angular excursions of femur rotation, and the knee and ankle were flexed more at footfall which contributed to a very low hip height. For D. dorsalis, changes in knee and ankle angles on the uphill surface were similar to those described previously for mammals moving up inclines, despite fundamental differences in limb posture between most mammals and lizards. Several features of the kinematics of D. dorsalis suggest that a sprawling limb enhances the ability to move on inclines.
Cholecystokinin affects gastric emptying and stomach motility in the rainbow trout Oncorhynchus mykiss
Authors: Olsson Catharina , Aldman Göran , Larsson Annhild , Holmgren Susanne 
Published: April 2021

ABSTRACT
In this study, we describe new methods for recording gastric emptying and in vivo measurements of intragastric pressure in fish. Using these methods, we investigated the effects of the sulphated octapeptide of cholecystokinin (CCK8) on gastric emptying and on stomach motility in vivo and in vitro. Gastric emptying of 99Tcm-labelled food was measured in swimming fish by using a gamma camera, counting consecutive 2.5 min periods for 18–42 h. After 20 h, 55.3±4.0 % of the labelled food remained in the stomach of the control fish (mean ± S.E.M., N=9). Vascular infusion of CCK8 (25 pmol kg−1 h−1) delayed gastric emptying so that 70.4±4.8 % of the labelled food remained in the stomach after 20 h (N=8). Gastric pressure changes in vivo were measured using a balloon surgically fitted into the cardiac or pyloric part of the stomach. In the cardiac part, intra-arterial infusion of CCK8 at 0.1 nmol kg−1 h−1 resulted in a decrease in the frequency and amplitude of rhythmic contractions, while higher doses started/increased contractions. Atropine blocked much of the basal contractile activity, but did not influence the CCK8-induced inhibition of contractile activity. The pyloric part of the stomach was unaffected by intra-arterial infusion of CCK8 or atropine. In vitro perfusion of the stomach (with a balloon placed in the cardiac part to record motility) with CCK8 at high concentrations (10−7 mol l−1 and above) augmented the spontaneous contractions, while lower concentrations had inconsistent effects. In addition, CCK8 (10−7 to 10−6 mol l−1) decreased the amplitude of spontaneous contractions in longitudinal strip preparations, usually in combination with an increase in the resting tension. The decrease in amplitude was not affected by the nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester hydrochloride (L-NAME; 10−4 mol l−1). Depending on the concentration and experimental arrangement, CCK8 had either inhibitory or excitatory effects on the cardiac stomach, suggesting the possible presence of different types of CCK receptor. We conclude that the predominant effect of CCK8 in vivo may be a slowing down of gastric emptying, presumably coinciding with a release of bile into the duodenum.
Control of abdominal extension in the freely moving intact crayfish Cherax destructor: II. Activity of the superficial extensor motor neurones
Authors: McCarthy Bernard J. , Macmillan David L. 
Published: April 2021

ABSTRACT
The activity of the superficial extensor motor neurones was recorded during slow abdominal extension in the crayfish Cherax destructor. Postural extensions were evoked by lowering a platform from beneath the suspended crayfish. During extensions where the abdomen was physically blocked from achieving full extension, the largest superficial extensor motor neurone (SEMN6) fired at a higher rate than during unhindered extensions. Blocking a segment neighbouring that being examined also increased SEMN6 activity, demonstrating an intersegmental spread of the reflex. The increase in SEMN6 firing rate occurred in the absence of activity in the sensory neurone of the tonic muscle receptor organ, demonstrating that the tonic sensory neurone is not necessary for load compensation during these abdominal extensions in C. destructor. The findings support earlier evidence suggesting that other receptor systems can mediate load compensation in the abdomen of the crayfish.
Escape trajectories of the brown shrimp Crangon crangon, and a theoretical consideration of initial escape angles from predators
Authors: Arnott Stephen A. , Neil Douglas M. , Ansell Alan D. 
Published: April 2021

ABSTRACT
Tail-flip escape trajectories of the brown shrimp Crangon crangon have been investigated in response to a natural predator, the cod Gadus morhua, and an artificial stimulus. Shrimps escaped by rolling to their left or right during the initial tail-flip of a response, and thereafter swam on their side. As a result of the laterally directed first tail-flip, initial escape angles always lay between 75° and 156° with respect to the (pre-escape) longitudinal axis (anterior=0°) of the shrimp. Symmetrical attacks from either head-on or tail-on produced escapes to the shrimp’s left or right in equal proportions, although a contralateral bias did occur if the shrimp experienced a looming object from one side before a symmetrical attack was applied. Lateral attacks produced a significantly greater proportion of contralateral responses than ipsilateral ones. Empirical and theoretical analyses indicate that the initial escape direction is influenced by an interaction between the range of first tail-flip escape angles that the shrimp is capable of performing and the risk of being intercepted by a predator during the initial stage of an escape. Thus, the unpredictability (‘protean behaviour’) of the response may be affected by the conditions of the interaction.
Subsequent tail-flips of an escape usually directed the response away from the stimulus, but sometimes escapes were instead steered to the side of the stimulus and then behind it. The probability of each type of escape occurring changed with attack direction.
The elements of protean behaviour that have been identified in both the initial and subsequent stages of the escape may prevent predators from learning a fixed pattern of response, but a trade-off occurs when escape trajectories infringe upon zones of high capture risk.
The development of a biological novelty: a different way to make appendages as revealed in the snout of the star-nosed mole Condylura cristata
Authors: Catania Kenneth C. , Northcutt R. Glenn , Kaas Jon H. 
Published: April 2021

ABSTRACT
The nose of the star-nosed mole Condylura cristata is a complex biological novelty consisting of 22 epidermal appendages. How did this new set of facial appendages arise? Recent studies find remarkable conservation of the genes expressed during appendage formation across phyla, suggesting that the basic mechanisms for appendage development are ancient. In the nose of these moles, however, we find a unique pattern of appendage morphogenesis, showing that evolution is capable of constructing appendages in different ways. During development, the nasal appendages of the mole begin as a series of waves in the epidermis. A second deep layer of epidermis then grows under these superficial epidermal waves to produce 22 separate, elongated epidermal cylinders embedded in the side of the mole’s face. The caudal end of each cylinder later erupts from the face and rotates forward to project rostrally, remaining attached only at the tip of the snout. As a result of this unique ‘unfolding’ formation, the rostral end of each adult appendage is derived from caudal embryonic facial tissue, while the caudal end of each appendage is derived from rostral facial tissue. This developmental process has essentially no outgrowth phase and results in the reversal of the original embryonic orientation of each appendage. This differs from the development of other known appendages, which originate either as outgrowths of the body wall or from subdivisions of outgrowths (e.g. tetrapod digits). Adults of a different mole species (Scapanus townsendii) exhibit a star-like pattern that resembles an embryonic stage of the star-nosed mole, suggesting that the development of the star recapitulates stages of its evolution.
The diving physiology of bottlenose dolphins (Tursiops truncatus): II. Biomechanics and changes in buoyancy at depth
Authors: Skrovan Randolph C. , Williams T. M. , Berry P. S. , Moore P. W. , Davis R. W. 
Published: April 2021

ABSTRACT
During diving, marine mammals must balance the conservation of limited oxygen reserves with the metabolic costs of swimming exercise. As a result, energetically efficient modes of locomotion provide an advantage during periods of submergence and will presumably increase in importance as the animals perform progressively longer dives. To determine the effect of a limited oxygen supply on locomotor performance, we compared the kinematics and behavior of swimming and diving bottlenose dolphins. Adult bottlenose dolphins (Tursiops truncatus) were trained to swim horizontally near the water surface or submerged at 5 m and to dive to depths ranging from 12 to 112 m. Swimming kinematics (preferred swimming mode, stroke frequency and duration of glides) were monitored using submersible video cameras (Sony Hi-8) held by SCUBA divers or attached to a pack on the dorsal fin of the animal. Drag and buoyant forces were calculated from patterns of deceleration for horizontally swimming and vertically diving animals. The results showed that dolphins used a variety of swimming gaits that correlated with acceleration. The percentage of time spent gliding during the descent phase of dives increased with depth. Glide distances ranged from 7.1±1.9 m for 16 m dives to 43.6±7.0 m (means ± S.E.M.) for 100 m dives. These gliding patterns were attributed to changes in buoyancy associated with lung compression at depth. By incorporating prolonged glide periods, the bottlenose dolphin realized a theoretical 10–21 % energetic savings in the cost of a 100 m dive in comparison with dives based on neutral buoyancy models. Thus, modifying locomotor patterns to account for physical changes with depth appears to be one mechanism that enables diving mammals with limited oxygen stores to extend the duration of a dive.
The diving physiology of bottlenose dolphins (Tursiops truncatus): III. Thermoregulation at depth
Authors: Williams Terrie M. , Noren D. , Berry P. , Estes J. A. , Allison C. , Kirtland J. 
Published: April 2021

ABSTRACT
During diving, marine mammals initiate a series of cardiovascular changes that include bradycardia and decreased peripheral circulation. Because heat transfer from thermal windows located in peripheral sites of these mammals depends on blood flow, such adjustments may limit their thermoregulatory capabilities during submergence. Here, we demonstrate how the thermoregulatory responses of bottlenose dolphins (Tursiops truncatus) are coordinated with the diving response. Heart rate, skin temperature and heat transfer from the dorsal fin and flank were measured while dolphins rested on the water surface, stationed 5–50 m under water and floated at the surface immediately following a dive. The results showed that heat flow ranged from 42.9±7.3 to 126.2±23.1 W m−2 and varied with anatomical site and diving activity. Upon submergence, heat flow declined by 35 % from the dorsal fin and by 24 % from the flank. An immediate increase in heat flow to levels exceeding pre-dive values occurred at both sites upon resurfacing. Changes in heart rate during diving paralleled the thermoregulatory responses. Mean pre-dive heart rate (102.0±2.6 beats min−1, N=26) decreased by 63.4 % during dives to 50 m and immediately returned to near resting levels upon resurfacing. These studies indicate that heat dissipation by dolphins is attenuated during diving. Rather than challenge the diving response, heat transfer is delayed until post-dive periods when the need for oxygen conservation is reduced.
Rhythmic changes in the serotonin content of the brain and eyestalk of crayfish during development
Authors: Castañón-Cervantes Oscar , Battelle Barbara-Anne , Luisa Fanjul-Moles María 
Published: April 2021

ABSTRACT
The present study investigated developmental circadian changes in the content of 5-hydroxytryptamine (5-HT) in two structures proposed to contain pacemakers in crayfish Procambarus clarkii: the cerebral ganglion and the eyestalks. Crayfish (N=260) from three developmental stages were divided into two groups: (1) animals subjected to 12 h:12 h light:dark cycles for 10 days and (2) animals treated as described above, then exposed to 72 h of continuous dim light. Crayfish from both groups were killed at different times of day, and the cerebral ganglion and the eyestalks of each were assayed for 5-HT by reversed-phase HPLC with electrochemical detection. In all stages of development, 5-HT content (expressed asμg g−1 wet mass tissue) showed circadian variations in both structures analyzed; rhythms continued to free-run under constant illumination, and total 5-HT content was higher in the brain (0.581±0.36 μg g−1; mean ± S.E.M.) than in the eyestalks (0.299±0.15 μg g−1). As development advances, the percentage of the rhythm that shows periods of 24 h diminishes, while the percentage of the rhythm that shows periods of 9 to 12 h increases. This seems to indicate that pulsatile variations in 5-HT content are superimposed in a circadian component. The relationship between the 5-HT rhythm and electroretinogram and motor activity rhythms during development is discussed.
Body-building without power training: endogenously regulated pectoral muscle hypertrophy in confined shorebirds
Authors: Dietz Maurine W. , Piersma Theunis , Dekinga Anne 
Published: April 2021

ABSTRACT
Shorebirds such as red knots Calidris canutus routinely make migratory flights of 3000 km or more. Previous studies on this species, based on compositional analyses, suggest extensive pectoral muscle hypertrophy in addition to fat storage before take-off. Such hypertrophy could be due to power training and/or be effected by an endogenous circannual rhythm. Red knots of two subspecies with contrasting migration patterns were placed in a climate-controlled aviary (12 h:12 h L:D photoperiod) where exercise was limited. Using ultrasonography, we measured pectoral muscle size as the birds stored fat in preparation for migration. At capture, there were no differences in body mass and pectoral muscle mass between the two subspecies. As they prepared for southward and northward migration, respectively, the tropically wintering subspecies (C. c. canutus) gained 31 g and the temperate wintering subspecies (C. c. islandica) gained 41 g. During this time, pectoral mass increased by 43–44 % of initial mass, representing 39 % (C. c. canutus) and 29 % (C. c. islandica) of the increase in body mass. The gizzard showed atrophy in conjunction with a diet change from molluscs to food pellets. Although we cannot exclude the possibility that the birds’ limited movement may still be a prerequisite for pectoral muscle hypertrophy, extensive power training is certainly not a requirement. Muscle hypertrophy in the absence of photoperiod cues suggests the involvement of an endogenous circannual process.
Isotope dilution spaces of mice injected simultaneously with deuterium, tritium and oxygen-18
Authors: Król Elzbieta , Speakman John R. 
Published: April 2021

ABSTRACT
The isotope dilution technique for measuring total body water (TBW), and the doubly labelled water (DLW) method for measuring energy expenditure, are both sensitive to small variations in the ratio of the hydrogen to oxygen-18 dilution space. Since the dilution space ratio varies between individuals, there has been much recent debate over what causes this variability (i.e. physiological differences between individuals or analytical error in the isotope determinations), and thus which values (individual or a population mean dilution space ratio) should be employed for TBW and DLW calculations. To distinguish between physiological and analytical variability, we injected 15 non-reproductive and 12 lactating mice (Mus musculus, outbred MF1) simultaneously with deuterium, tritium and oxygen-18. The two hydrogen labels were administered and analysed independently, therefore we expected a strong correlation between dilution space ratios based on deuterium and tritium if most of the variation in dilution spaces was physiological, but only a weak correlation if most of the variation was analytical. Dilution spaces were significantly influenced by reproductive status. Dilution spaces expressed as a percentage of body mass averaged 15.7 % greater in lactating mice than in non-reproductive mice. In addition, the hydrogen tracer employed had a significant effect (deuterium spaces were 2.0 % larger than tritium spaces). Deuterium and tritium dilution spaces, expressed as a percentage of body mass, were highly correlated. Dilution space ratios ranged from 0.952 to 1.146 when using deuterium, and from 0.930 to 1.103 when using tritium. Dilution space ratios based on deuterium and tritium were also highly correlated. Comparison of standard deviations of the dilution space ratio based on deuterium in vivo and in vitro indicated that only 4.5 % of the variation in the dilution space ratios observed in the mice could be accounted for by analytical variation in the deuterium and oxygen-18 analyses. Although our results include data which were outside the limits previously regarded as biologically possible, the correlations that we detected strongly suggest that variation in the observed dilution space ratio was mostly physiological rather than analytical.
Food ingestion and water turnover in hummingbirds: how much dietary water is absorbed?
Authors: McWhorter Todd J. , Martínez del Rio Carlos 
Published: April 2021

ABSTRACT
Hummingbirds are specialized nectarivores that feed on dilute solutions of sugars with trace amounts of amino acids and electrolytes. Their diets contain excess water that, if absorbed, must be eliminated. It has been hypothesized that in hummingbirds only a small fraction of this dietary water may be absorbed in the intestine. Here, we report the results of experiments designed to examine the relationship between nectar intake and water turnover in hummingbirds. Our results also allow the estimation of water absorption across the intestine and therefore test the hypothesis that ingested water in hummingbirds passes largely unabsorbed through the gastrointestinal tract. We found that fractional and total water turnover increased linearly with water ingestion. At low sucrose concentrations, food intake rates between four and five times body mass per 12 h were not unusual. A simple mass-balance model suggested that 78 % of ingested water was absorbed in the gastrointestinal tract and hence must be processed by the kidneys. However, fractional water absorption was variable and did not appear to be correlated with food or water intake parameters. Our results do not lend support to the hypothesis that the bulk of dietary water passes through the intestine unabsorbed. Although hummingbird kidneys appear well suited to excrete large volumes of dilute urine, rates of energy assimilation in hummingbirds may be constrained by excess water elimination when these birds are feeding on nectars with a low sugar concentration.
Genes to remember
Authors: Alberini Cristina M. 
Published: April 2021

ABSTRACT
It has been known for several decades that the formation of long-term memory requires gene expression. In recent years, the use of genetic and molecular approaches has led to the identification and characterization of genes and molecules that play a fundamental role in the biological mechanisms underlying learning and memory. From these studies, it appears that molecules and molecular mechanisms essential for the process of memory have been conserved throughout evolution. The cyclic AMP (cAMP)-dependent activation pathway and a cAMP-dependent cascade of gene expression have been shown to be essential for memory formation in Aplysia californica, Drosophila melanogaster and rodents. Moreover, members of the transcription factor family cAMP response element binding proteins (CREBs) seem to represent key molecules for transforming incoming information into long-term memory. Here, we review the studies showing that conserved molecules and biological mechanisms are engaged in simple and complex forms of memory.
Sound production by abdominal tymbal organs in two moth species: the green silver-line and the scarce silver-line (Noctuoidea: Nolidae: Chloephorinae)
Authors: Skals Niels , Surlykke Annemarie 
Published: April 2021

ABSTRACT
Male moths of the chloephorine species Pseudoips prasinana and Bena bicolorana produce clicks (approximately 100 dB peSPL at 10 cm) using ventral tymbal organs located in a cleft in the second abdominal sternite. Large muscles insert on the dorsal part of the tymbal frame and rhythmically flex a thin sheet of cuticle. Normally, each sound-production cycle contains four clicks, the left and right tymbals producing clicks both on active buckling caused by muscle contraction and on the passive elastic return from buckling. Histochemical staining indicated the presence of elastic resilin-like proteins in the tymbals. Obvious differences between the click patterns of the two species reflect differences in their tymbal morphology. P. prasinana has smooth tymbals and produces a single click (300 μs, 40 kHz) for each tymbal buckling. In contrast, B. bicolorana has striae on the medial part of the tymbals. Accordingly, it produces many clicks per buckling. The click pattern is a heterogeneous mixture of large clicks at 52 kHz, resembling those of P. prasinana, interspersed with series of broad-band clicks (20–100 kHz) of lower intensity (15–20 dB). Thus, in chloephorine moths, there is a correlation between the structure and function of the smooth and striated tymbals that is strikingly similar to that in arctiid moths, although the two types of tymbals have evolved independently. The hearing of P. prasinana is tuned to its own sounds with lowest threshold (38 dB SPL) at 40–60 kHz. We suggest that sound production in male chloephorines plays a part in sexual acoustic communication.