bluuebunny/crossref_metadata_2025_split huggingface dataset:
Testing Hypotheses Concerning The Phenotypic Plasticity Of Escape Performance In Fish Of The Family Cottidae
Authors: Temple Genevieve K. , Johnston Ian A. 
Published: April 2021

ABSTRACT
A knowledge of the natural history of two species of marine Cottidae was used to construct a set of complex a priori hypotheses to test the idea that seasonal temperature acclimation conferred a fitness advantage and to examine whether acclimation responses were constant through development. The species studied were the short-horn sculpin (Myoxocephalus scorpius L.) and the long-spined sea scorpion (Taurulus bubalis Euphr.). Fast-start escape performance was measured as a proxy of fitness, and maximum body-length-specific speed (Ûmax) and acceleration (Âmax), and angular velocity (ωmax) and cumulative turning angle (CTA) were quantified. Fish were acclimated to 5, 15 and 20 °C and filmed using high-speed cinematography at 0.8, 5.0, 15.0 and 20.0 °C. The following hypotheses were tested: (1) improvements in escape performance following acclimation to high temperature in adult short-horn sculpin that live offshore would involve a trade-off in performance at low temperature, (2) the escape response of the sea scorpion, which experiences large daily temperature variation, would exhibit low thermal sensitivity and be unchanged by acclimation between 5 and 15 °C, and (3) in short-horn sculpin, the ability to acclimate maximum speed thermally is acquired during ontogeny in parallel with the offshore migration of the late juvenile stage. At 20.0 °C, in adult short-horn sculpin, Ûmax and Âmax were 110 % and 55 % higher, respectively, in 15 °C-than in 5 °C-acclimated fish. No evidence was obtained for improved fast-start performance at 0.8 °C or 5.0 °C following cold acclimation. In the long-spined sea scorpion, acclimation to 5 and 15 °C did not improve Ûmax or Âmax compared with fish acutely exposed to these temperatures, although acclimation to 5 °C increased ωmax (P=0.005).
When tested over the most extreme thermal range found in the field, all variables were improved at a test temperature of 0.8 °C in 5 °C-compared with 15 °C-acclimated sea scorpion. Acclimation therefore appeared to be beneficial in some instances in both species. How this affects relative fitness is uncertain. The scaling of Ûmax with acclimation to 5 and 15 °C was examined in both species over the test range 5.0–15.0 °C. Temperature acclimation did not affect scaling relationships of Ûmax in long-spined sea scorpion ranging in total body length (L) from 45 to 160 mm. At a test temperature of 15.0 °C, the scaling of Ûmax for short-horn sculpin ranging in total body length from 43 to 270 mm changed from aL−0.98 in 5 °C-acclimated fish to aL−0.50 (where a is the proportionality coefficient in the regression equation) in 15 °C-acclimated fish (P&lt;0.01). In short-horn sculpin, therefore, the ability to modify escape performance with temperature acclimation was found to vary during ontogeny, potentially paralleling a migration from a more variable to a more stable thermal environment.
Rattlesnake Strike Behavior: Kinematics
Authors: Kardong Kenneth V. , Bels Vincent L. 
Published: April 2021

ABSTRACT
The predatory behavior of rattlesnakes includes many distinctive preparatory phases leading to an extremely rapid strike, during which venom is injected. The rodent prey is then rapidly released, removing the snake’s head from retaliation by the prey. The quick action of the venom makes possible the recovery of the dispatched prey during the ensuing poststrike period. The strike is usually completed in less than 0.5 s, placing a premium on an accurate strike that produces no significant errors in fang placement that could result in poor envenomation and subsequent loss of the prey. To clarify the basis for effective strike performance, we examined the basic kinematics of the rapid strike using high-speed film analysis. We scored numerous strike variables. Four major results were obtained. (1) Neurosensory control of the strike is based primarily upon sensory inputs via the eyes and facial pits to launch the strike, and upon tactile stimuli after contact. Correction for errors in targeting occurs not by a change in strike trajectory, but by fang repositioning after the jaws have made contact with the prey. (2) The rattlesnake strike is based upon great versatility and variation in recruitment of body segments and body postures. (3) Forces generated during acceleration of the head are transferred to posterior body sections to decelerate the head before contact with the prey, thereby reducing impact forces upon the snake’s jaws. (4) Body acceleration is based on two patterns of body displacement, one in which acute sections of the body open like a gate, the other in which body segments flow around postural curves similar to movements seen during locomotion. There is one major implication of these results: recruitment of body segments, launch postures and kinematic features of the strike may be quite varied from strike to strike, but the overall predatory success of each strike by a rattlesnake is very consistent.
Homing Pigeons Use Olfactory Cues for Navigation In England
Authors: Guilford Tim , Gagliardo Anna , Chappell Jackie , Bonadonna Francesco , Perera Theresa Burt De , Holland Richard 
Published: April 2021

ABSTRACT
Although the use of olfactory cues in pigeon navigation is well established, the generality of olfactory navigation remains uncertain because of apparent variability in results gained by different researchers in different regions. We report the results of the first experiments investigating the effect of anosmia on homing pigeons reared in a previously uninvestigated region, southern England. In series 1, experienced birds showed little effect of anosmia induced with zinc sulphate at unfamiliar sites 30 km and 39 km from the loft, but treated birds were significantly poorer than controls at homing from an unfamiliar site 66 km distant (and in pooled results). In series 2, naïve (untrained) birds, both control and zinc-sulphate-treated, showed poor homing abilities and initial orientation from sites 25 km, 36 km and 39 km from the loft. Nevertheless, in pooled results, controls showed significantly better homeward orientation than anosmic birds and were significantly more likely to home on the day of release. The most likely explanation for our results is that pigeons are able to use olfactory navigation in southern England, but that for some reason the olfactory map is relatively weak.
Scaling of Muscle Performance During Escape Responses in the Fish Myoxocephalus Scorpius L
Authors: James Rob S. , Johnston Ian A. 
Published: April 2021

ABSTRACT
Fast-starts associated with escape responses were studied in short-horn sculpin (Myoxocephalus scorpius L.), ranging from 5.5 to 32 cm in total length (L). Electromyography and sonomicrometry were used simultaneously to measure muscle activation and length changes, respectively, in the superficial layers of fast muscle in rostral myotomes. Escape responses consisted of a half tailbeat to bend the body into a C-shape (C-bend), another half tailbeat (contralateral contraction), followed by one or two more tailbeats and/or a gliding phase. The scaling relationships for both muscle strain and shortening duration differed between the C-bend and the contralateral contraction. As a result, relative muscle shortening velocity (V/V0) scaled as −1.18L1.06 for the C-bend and as 1.23L−0.66 for the contralateral contraction. Therefore, the scaling relationships for muscle shortening velocity varied throughout the time course of the escape response. Muscle power output was determined by using the work-loop technique to subject isolated muscle fibres to in vivo strain and stimulation patterns. Plots of the instantaneous muscle forces and velocities achieved during the contralateral contraction were found to deviate from the steady-state force–velocity relationship. Maximum instantaneous muscle power output was independent of body size, with mean maximum values of 307 and 222W kg−1 wet muscle mass for the C-bend and the contralateral contraction, respectively.
Finding Food: Senses Involved in Foraging for Insect Larvae in the Electric Fish Gnathonemus Petersii
Authors: Emde Gerhard Von Der , Bleckmann Horst 
Published: April 2021

ABSTRACT
The weakly electric fish Gnathonemus petersii searches at night for insect larvae in tropical African streams. The aim of this study was to determine the contributions of different sensory modalities to foraging. The time that fish needed to find two randomly placed chironomid larvae was measured. The influence of various senses on search time was investigated by blocking the use of one or more senses. Active electrolocation was used by most fish for prey detection in the dark. In addition, passive electrolocation played a role in some individuals. If light was available, vision could become the dominant sense in some individuals, replacing active electrolocation. The presence of chemical cues decreased prey detection time in most fish. Prey movements also shortened search times when active electrolocation and vision were not possible, indicating that the mechanosensory lateral line also plays a role in the detection of moving prey. The results show that G. petersii uses several senses simultaneously during foraging. Each individual favours a specific combination of the available sensory inputs. If one sensory modality is eliminated, fish can switch to other modalities, indicating that the food detection system is flexible and plastic.
Oxygen and the Upper Limits to Animal Design and Performance
Authors: Suarez Raul K. 
Published: April 2021

ABSTRACT
Mass-specific rates of aerobic metabolism (/Mb) scale in inverse proportion to body mass (Mb). Thus, small hummingbirds display the highest / Mb known among vertebrates. Among all animals, higher /Mb values are known only in flying insects. The high body-mass-specific rates of metabolism seen in hummingbirds are made possible by high lung O2 diffusing capacities, cardiac outputs, ratios of capillary surface area to muscle fiber surface area, mitochondrial volume densities, cristae surface densities and concentrations of enzymes involved in energy metabolism. Current evidence from control analyses of O2 transport through the respiratory and cardiovascular systems and of metabolic fluxes through pathways of energy metabolism indicates shared control of maximum flux rates among multiple steps (i.e. the absence of single rate-limiting steps). This supports the suggestion that functional capacities at each step in linear pathways or processes are matched to each other, and provides an explanation for why the up-regulation of functional capacities has occurred at virtually all steps in the evolution of the smallest vertebrate homeotherms. Flying insects make use of a tracheal system for O2 transport and, like hummingbirds, possess a highly up-regulated biochemical machinery for substrate oxidation. Studies of hummingbirds and honeybees reveal closer matches between biochemical flux capacities and maximum physiological flux rates than in animals capable of lower maximum /Mb. It is proposed that the upper limits to functional capacities set the upper limit to /Mb. This upper limit to aerobic metabolic rate may contribute, along with other factors, towards establishing the lower limit to vertebrate homeotherm size.
Self-Association, Cooperativity and Supercooperativity of Oxygen Binding by Hemoglobins
Authors: Riggs Austen F. 
Published: April 2021

ABSTRACT
Cooperative ligand binding by tetrameric vertebrate hemoglobins (Hbs) makes possible the delivery of oxygen at higher pressures than would otherwise occur. This cooperativity depends on changes in dimer–dimer interactions within the tetramer and is reflected in a 50 000-fold increase in the tetramer–dimer dissociation constant in human Hb upon oxygenation at pH 7.4, from approximately 2×10−11 mol l–1 to approximately 10−6 mol l−1. Hbs that undergo such ligand-dependent changes in association are widespread in non-vertebrates, where the mechanisms are very different from those in vertebrates. Oligomeric Hbs have been identified in organisms in five phyla (molluscs, echinoderms, annelids, phoronids and chordates) that dissociate to subunits upon oxidation of the heme iron and reassociate with the binding of ferric iron ligands such as CN−, N3− or NO2−. Thus, the valence and ligand state of the heme iron control the stability of a critical subunit interface. The broad distribution of this phenomenon suggests a common mechanism of communication between heme and interface that may be almost universal among non-vertebrate Hbs. This interaction may be similar to that known for the homodimeric Hb of the mollusc Scapharca inaequivalvis.
Although muscle tissue Hbs or myoglobins (Mbs) are usually monomeric, with non-cooperative O2 binding, the radular muscles of gastropod molluscs and chitons have homodimeric Mbs that bind O2 cooperatively. Cooperative non-muscle tissue Hbs have also been identified. These include the neural Hb of the nemertean worm Cerebratulus lacteus and the Hb of the diving beetle Anisops assimilis, which exhibit deoxygenation-dependent self-association of monomers that is associated with high Hill coefficients. Calculations suggest that the 2–3 mmol l−1 concentration of Hb on a heme basis in the brain of Cerebratulus should substantially extend the time as an active predator in an anaerobic or hypoxic environment. Oxygen from the Hb of Anisops is delivered to a gas bubble and thereby controls the buoyant density.
Many Hbs of amphibians, reptiles, birds and some embryonic mammals exhibit a further ‘supercooperativity’ of O2 binding which depends on reversible deoxygenation-dependent tetramer–tetramer association to form an assemblage with a very low affinity for O2. This phenomenon results in steeper O2-binding curves than exhibited by tetramers alone. The increased cooperativity should result in an increase in the amount of O2 delivered to the tissues and should be especially valuable for avian flight muscles.
Hemoglobins From Bacteria to Man: Evolution of Different Patterns of Gene Expression
Authors: Hardison Ross 
Published: April 2021

ABSTRACT
The discovery of hemoglobins in virtually all kingdoms of organisms has shown (1) that the ancestral gene for hemoglobin is ancient, and (2) that hemoglobins can serve additional functions besides transport of oxygen between tissues, ranging from intracellular oxygen transport to catalysis of redox reactions. These different functions of the hemoglobins illustrate the acquisition of new roles by a pre-existing structural gene, which requires changes not only in the coding regions but also in the regulatory elements of the genes. The evolution of different regulated functions within an ancient gene family allows an examination of the types of biosequence data that are informative for various types of issues. Alignment of amino acid sequences is informative for the phylogenetic relationships among the hemoglobins in bacteria, fungi, protists, plants and animals. Although many of these diverse hemoglobins are induced by low oxygen concentrations, to date none of the molecular mechanisms for their hypoxic induction shows common regulatory proteins; hence, a search for matches in non-coding DNA sequences would not be expected to be fruitful. Indeed, alignments of non-coding DNA sequences do not reveal significant matches even between mammalian α- and β-globin gene clusters, which diverged approximately 450 million years ago and are still expressed in a coordinated and balanced manner. They are in very different genomic contexts that show pronounced differences in regulatory mechanisms. The α-globin gene is in constitutively active chromatin and is encompassed by a CpG island, which is a dominant determinant of its regulation, whereas the β-globin gene is in A+T-rich genomic DNA. Non-coding sequence matches are not seen between avian and mammalian β-globin gene clusters, which diverged approximately 250 million years ago, despite the fact that regulation of both gene clusters requires tissue-specific activation of a chromatin domain regulated by a locus control region. The cis-regulatory sequences needed for domain opening and enhancement do show common binding sites for transcription factors. In contrast, alignments of non-coding sequences from species representing multiple eutherian mammalian orders, some of which diverged as long as 135 million years ago, are reliable predictors of novel cis-regulatory elements, both proximal and distal to the genes. Examples include a potential target for the hematopoietic transcription factor TAL1.
Adaptations of Vertebrate Neurons to Hypoxia And Anoxia: Maintaining Critical Ca2+ Concentrations
Authors: Bickler Philip E. , Buck Leslie T. 
Published: April 2021

ABSTRACT
Down-regulation of ion channel activity (‘channel arrest’), which aids in preserving critical ion gradients in concert with greatly diminished energy production, is one important strategy by which anoxia-tolerant neurons adapt to O2 shortage. Channel arrest results in the elimination of action potentials and neurotransmission and also decreases the need for ion transport, which normally requires a large energy expenditure. Important targets of this down-regulation may be channels in which activity would otherwise result in the toxic increases in intracellular [Ca2+] characteristic of anoxia-sensitive mammalian neurons. In turtles, Na+ channels and the Ca2+-permeable ion channel of the N-methyl-D-aspartate (NMDA)-type glutamate receptor undergo down-regulation during anoxia. Inactivation of NMDA receptors during hypoxia occurs by a variety of mechanisms, including alterations in the phosphorylation state of ion channel subunits, Ca2+-dependent second messenger activation, changes in Ca2+-dependent polymerization/depolymerization of actin to postsynaptic receptors and activation of other G-protein-coupled receptors. Release of inhibitory neurotransmitters (e.g. γ-aminobutyrate) and neuromodulators (e.g. adenosine) into the brain extracellular fluids may play an important role in the down-regulation of these and other types of ion channels.
The Origins of Marine Bioluminescence: Turning Oxygen Defence Mechanisms Into Deep-Sea Communication Tools
Authors: Rees Jean-François , Wergifosse Bertrand De , Noiset Olivier , Dubuisson Marlene , Janssens Bernadette , Thompson Eric M. 
Published: April 2021

ABSTRACT
Bioluminescence, the emission of ecologically functional light by living organisms, emerged independently on several occasions, yet the evolutionary origins of most bioluminescent systems remain obscure. We propose that the luminescent substrates of the luminous reactions (luciferins) are the evolutionary core of most systems, while luciferases, the enzymes catalysing the photogenic oxidation of the luciferin, serve to optimise the expression of the endogenous chemiluminescent properties of the luciferin. Coelenterazine, a luciferin occurring in many marine bioluminescent groups, has strong antioxidative properties as it is highly reactive with reactive oxygen species such as the superoxide anion or peroxides. We suggest that the primary function of coelenterazine was originally the detoxification of the deleterious oxygen derivatives. The functional shift from its antioxidative to its light-emitting function might have occurred when the strength of selection for antioxidative defence mechanisms decreased. This might have been made possible when marine organisms began colonising deeper layers of the oceans, where exposure to oxidative stress is considerably reduced because of reduced light irradiance and lower oxygen levels. A reduction in metabolic activity with increasing depth would also have decreased the endogenous production of reactive oxygen species. Therefore, in these organisms, mechanisms for harnessing the chemiluminescence of coelenterazine in specialised organs could have developed, while the beneficial antioxidative properties were maintained in other tissues. The full range of graded irradiance in the mesopelagic zone, where the majority of organisms are bioluminescent, would have provided a continuum for the selection and improvement of proto-bioluminescence. Although the requirement for oxygen or reactive oxygen species observed in bioluminescent systems reflects the high energy required to produce visible light, it may suggest that oxygen-detoxifying mechanisms provided excellent foundations for the emergence of many bioluminescent systems.
Life at Stable low Oxygen Levels: Adaptations of Animals to Oceanic Oxygen Minimum Layers
Authors: Childress James J. , Seibel Brad A. 
Published: April 2021

ABSTRACT
Zones of minimum oxygen level are found at intermediate depths in most of the world’s oceans and, although the oxygen partial pressure in some of these ‘oxygen minimum layers’ is only a fraction of a kilopascal, populations of pelagic metazoans exist there. These oxygen minimum layers are areas of the water column and the associated benthos with stable conditions of continuously low oxygen level and low temperature at intermediate depths (400–1000 m depth) over vast areas. Off California, where at the oxygen minimum is 0.8 kPa, there are abundant populations of animals both in the water column and on the bottom. Farther to the south in the eastern tropical Pacific, oxygen partial pressures of less than approximately 0.4 kPa result in very low biomasses and diversity of animals at minimum layer depths.
At the minimum oxygen levels found off California, most animals which inhabit the minimum zones appear to support their routine metabolic demands via aerobic metabolism. They do this by being very effective at removing oxygen from water. Among the adaptations of pelagic crustaceans to these conditions are: (1) enhanced ventilatory abilities, (2) enhanced percentage removal of O2 from the ventilatory stream, (3) large gill surface areas, (4) short diffusion distances from the water to the blood, and (5) hemocyanin respiratory proteins with a very high affinity for O2, high cooperativity and large Bohr effects. The lower O2 consumption rates of many deeper-living species are also functionally adaptive in that they facilitate aerobic survival at low . However, they are not adaptations to the minimum layer, since similarly low rates are found in the same and comparable species living at the same depths in regions without well-developed minima, and these animals are unable to survive at the low values of the minima. While anaerobic metabolism may be important for metabolic rates above the routine level for most animals in the minimum layer, there is little evidence for the use of sustained anaerobiosis in the species studied. In summary, given the stable presence of very low O2 levels in the minima, the primary adaptations of animals living within them are those that support aerobic metabolism by giving the animals remarkable abilities to extract O2 from water. These abilities are notably better than those of animals adapted to unstable hypoxic environments, such as intertidal mudflats, while the latter animals rely to a much greater extent on anaerobiosis and perhaps on metabolic suppression to survive periods of anoxia.