bluuebunny/crossref_metadata_2025_split huggingface dataset:
How Fish Power Predation Fast-Starts
Authors: Johnston Ian A. , Van Leeuwen Johan L. , Davies Melissa L. F. , Beddow Toni 
Published: April 2021

ABSTRACT
Short-horned sculpin (Myoxocephalus scorpius L.) were acclimated for 6–8 weeks to either 5#x00B0;C or 15#x00B0;C (12 h dark: 12 h light). Fast-starts elicited by prey capture were filmed from above in silhouette using a high-speed video camera (200 frames s−1). Outlines of the body in successive frames were digitised and changes in strain for the dorsal fast muscle calculated from a knowledge of backbone curvature and the geometrical arrangement of fibres. For 15#x00B0;C-acclimated fish at 15#x00B0;C, muscle strain amplitude (peak-to-peak) during the first tail-beat was approximately 0.16 at 0.32L, 0.19 at 0.52L and 0.15 at 0.77L, where L is the total length of the fish. Fast muscle fibres were isolated and subjected to the strains calculated for the first tail-beat of the fast-start (abstracted cycle). Preparations were electrically stimulated at various times after the initiation of the fast-start using an in vivo value of duty cycle (27 %). Prior to shortening, muscle fibres at 0.52L and 0.77L were subjected to a pre-stretch of 0.055l0 and 0.085l0 respectively (where l0 is resting muscle length). The net work per cycle was calculated from plots of fibre length and tensile stress. For realistic values of stimulus onset, the average power output per abstracted cycle was similar at different points along the body and was in the range 24–31 W kg−1 wet muscle mass. During shortening, the instantaneous power output reached 175–265 W kg−1 wet muscle mass in middle and caudal myotomes. At the most posterior position examined, the muscle fibres produced significant tensile stresses whilst being stretched, resulting in an initially negative power output. The fibres half-way down the trunk produced their maximum power at around the same time that caudal muscle fibres generated significant tensile stress. Fast muscle fibres at 0.37–0.66L produced 76 % of the total work done during the first tail-beat compared with only 14 % for fibres at 0.67–0.86L, largely reflecting differences in muscle mass. The effect of temperature acclimation on muscle power was determined using the strain fluctuations calculated for 0.52L. For 5#x00B0;C-acclimated fish, the average power per cycle (± S.E.M.; W kg−1 wet muscle mass) was 21.8±3.4 at 5#x00B0;C, falling to 6.3±1.8 at 15#x00B0;C. Following acclimation to 15#x00B0;C, average power per cycle increased to 23.8±2.8 W kg−1 wet muscle mass at 15#x00B0;C. The results indicate near-perfect compensation of muscle performance with temperature acclimation.
Feeding Behavior in the Nocturnal Moth Manduca Sexta is Mediated Mainly by Blue Receptors, but where are they Located in the Retina?
Authors: Cutler Dianne E. , Bennett Ruth R. , Stevenson Robert D. , White Richard H. 
Published: April 2021

ABSTRACT
The spectral sensitivity of nectar feeding by adults of the tobacco hawkmoth Manduca sexta was measured in free-choice experiments. The action spectrum displayed a narrow peak at 450 nm and a low secondary maximum at 560 nm. Thus, the feeding response is mediated primarily by blue-sensitive receptors containing the Manduca sexta photopigment P450, while green-sensitive receptors containing P520 play a minor role. A minimum at 500 nm separating the two peaks suggests mutual inhibition between green and blue receptors or negative interaction more proximally in the visual system. The action spectrum drops off abruptly at 400 nm, in accordance with an earlier finding that ultraviolet wavelengths, discerned by receptors containing P357, obstruct the feeding response.
The spectral sensitivity of the Manduca sexta compound eye, determined by electroretinogram recordings, and earlier visual pigment measurements indicate that approximately 75 % of the receptors are green-sensitive, with the remainder divided between blue-and ultraviolet-sensitive cells. The distribution of receptor types in small areas of the retina was measured by their ultrastructural response to light. Green and ultraviolet receptors were found, but not the blue receptors that dominate the feeding response. Possibly they are concentrated in a particular region of the retina that has not yet been found.
Evidence That Calcium-Dependent Cellular Processes are Involved in the Stiffening Response of Holothurian Dermis and That Dermal Cells Contain an Organic Stiffening Factor
Authors: Trotter John A. , Koob Thomas J. 
Published: April 2021

ABSTRACT
Although previous investigations have shown that experimental increases and decreases of the concentration of extracellular Ca2+ produce correlated changes in the stiffness of holothurian dermis, they have failed to determine whether the Ca2+-correlated changes were due to Ca2+-dependent cellular events or to direct effects of Ca2+ on the viscosity of the extracellular matrix. We have addressed this question by testing two explicit predictions of the latter hypothesis: that dermal stiffness should be correlated with the Ca2+ concentration in the absence of viable cells; and that, in the presence of a normal extracellular Ca2+ concentration, drugs that inhibit cellular pathways dependent on Ca2+ should not affect dermal stiffness. Our results are inconsistent with the hypothesis and support the alternative hypothesis that Ca2+ is important only in the cellular regulation of dermal stiffness. In addition, we have extracted from dermal cells an organic factor that stiffens the extracellular matrix.
Remodelling of an Intact Neurone in the Central Nervous System of the Leech
Authors: Calabrese B. , Pellegrino M. 
Published: April 2021

ABSTRACT
The regeneration pattern of two identified central neurones was studied in the leech Hirudo medicinalis. Anterior pagoda (AP) and mechanosensory touch-sensitive (T) neurones were stained in adult segmental ganglia, maintained in culture for 6–10 days. AP neurones, which normally project only to the contralateral nerve roots, sprouted extensively in all the available nerve paths during regeneration. Mechanosensory T cells, in the same experimental conditions, showed only a moderate growth and did not change their normal pattern of axonal projections. The observed differences in the growth pattern might account for the different electrophysiological responses to axotomy exhibited by the two types of neurone. Interruption of interganglionic connectives induced a moderate and stereotyped remodelling of the morphology of intact AP neurones, which was reminiscent of that transiently exhibited during embryonic development. This response was observed in 25 % of the AP neurones we examined.
Seven Theses on Pigeon Homing Deduced From Empirical Findings
Authors: Wallraff Hans G. 
Published: April 2021

ABSTRACT
Experimental findings obtained in recent years make it possible to recognize and distinguish the most relevant components determining homing flights of displaced pigeons. Conclusions deduced from these experiments, more or less compelling or tentative, are presented in the form of seven theses, supplemented by several subtheses along with reference to empirical data. The principal theses are as follows. (1) Passively displaced pigeons find the way home by using location-dependent signals and not by path integration based on recording of motion. Pigeons are able to home, even from unfamiliar areas, without access to potentially useful information during transport to the release site. (2) Home-related orientation of pigeons in unfamiliar areas requires positional information acquired olfactorily from atmospheric trace gases. Empirically deduced details of olfactory navigation are enumerated (connection with winds and the sun, inaccuracy, spatial range, time course of sampling and memorizing spatial information, etc.). The critical gap in our knowledge, i.e. the nature and spatio-temporal distribution of the substances involved, is provisionally filled by speculation. (3) In familiar areas, known from previous flights, the visual landscape is used additionally to find the way home. (4) Initial orientation of pigeons does not exclusively reflect home-related navigation but includes components independent of the position with respect to home. Observed bearings are co-determined by a general preference for a certain compass direction and by distracting features of the nearby landscape. (5) Proportions among components controlling initial orientation according to theses 2–4 are highly variable depending on local, temporal and experimental conditions and on the life histories of the pigeons. This complexity greatly restricts recognition of the navigationally relevant components of behaviour at a given release site. (6) Sensory inputs, being neither olfactory nor visual, do not substantially contribute to determining the current position with respect to home. This thesis need not be definitive, but at present no contradicting evidence is available. (7) Pigeon homing is a model case of bird homing in general. Experiments with other species support this thesis. So far, there is no reason to assume that wild birds apply mechanisms fundamentally different from those of pigeons to find the way home.
The Debate Over Olfactory Navigation by Homing Pigeons
Authors: Able Kenneth P. 
Published: April 2021

ABSTRACT
In the years since 1971, when Papi and his colleagues first proposed that odors played an important role in the homing navigation of pigeons, the hypothesis has remained controversial. Although the idea seemed intuitively unreasonable to nearly everyone working in the field at that time, empirical support from a wide variety of experiments emanating from Papi’s laboratory in Pisa has stimulated a quarter of a century of experiments, theorizing, advocacy and dissent. The issue is reviewed here in contributions by Hans Wallraff, one of the chief proponents of olfactory navigation, and Roswitha Wiltschko, who remains skeptical about the involvement of odors in pigeon homing. At the Editors’ request, I provide here a personal perspective on the debate from one who has had no involvement in the issue and, indeed, has never released a homing pigeon.
Middle-Scale Navigation: the Vertebrate Case
Authors: Sherry David F. 
Published: April 2021

ABSTRACT
Few ideas have had a greater impact on the study of navigation at the middle scale than the theory of the cognitive map. As papers in this section show, current views of the cognitive map range from complete rejection of the idea (Bennett, 1996) to new proposals for the behavioural and neural bases of the cognitive map (Gallistel and Cramer, 1996; McNaughton et al. 1996). The papers in this section also make it clear that path integration has taken centre stage in theorizing about navigation at the middle scale. Path integration is the use of information generated by locomotion to determine the current distance and direction to the origin of the path. Etienne (1980) provided one of the first experimental demonstrations of path integration by a vertebrate, and in this section Etienne et al. (1996) describe recent research with animals and humans on the interaction between path integration and landmark information. Path integration is also the fundamental means of navigation in the model described by Gallistel and Cramer (1996). McNaughton et al. (1996) suggest that the neural basis of path integration is found in the place cells and head direction cells of the hippocampus and associated brain regions.
Behavioural and Neural Bases of Orientation in Food-Storing Birds
Authors: Sherry David F. , Duff Sarah J. 
Published: April 2021

ABSTRACT
Food-storing birds retrieve hoarded food by remembering the locations of large numbers of spatially dispersed caches. The basic patterns of spatial orientation in these animals have been established in research on two major groups of food-storing birds, chickadees and tits (Paridae), and jays and nutcrackers (Corvidae). Experiments using displacement of landmark arrays show that food-storing birds rely on visual information from nearby landmarks to locate concealed caches. The appearance of the cache sites themselves seems to be relatively unimportant in cache retrieval, perhaps because local features are subject to change during the lifetime of a cache. Under some conditions, food-storing birds use sun-compass information to orient their search for caches, but appear to integrate sun-compass information with landmark information. Lesions of the avian hippocampus disrupt cache retrieval and other spatial tasks in food-storing birds without disrupting the formation of simple associations. Comparative studies show that food-storing birds possess a hippocampus larger than that of non-food-storing birds, probably as an evolutionary consequence of their dependence on spatial orientation for cache retrieval. Experience with cache retrieval plays a role in the development of increased hippocampal size, and there are indications of seasonal variation in hippocampal size in food-storing species.
Homing in Pacific Salmon: Mechanisms and Ecological Basis
Authors: Dittman Andrew H. , Quinn Thomas P. 
Published: April 2021

ABSTRACT
Pacific salmon (Oncorhynchus spp.) are famous for their homing migrations from oceanic feeding grounds to their natal river to spawn. During these migrations, salmon travel through diverse habitats (e.g. oceans, lakes, rivers), each offering distinct orientation clues and, perhaps, requiring distinct sensory capabilities for navigation. Despite these challenges, homing is generally precise and this philopatry has resulted in reproductively isolated spawning populations with specialized adaptations for their natal habitat. This paper reviews the mechanisms underlying all aspects of salmon homing but emphasizes the final, freshwater phase governed by olfactory recognition of homestream water. Prior to their seaward migration, juvenile salmon learn (imprint on) odors associated with their natal site and later, as adults, use these odor memories for homing. Our understanding of this imprinting process is derived primarily from studies using artificial odorants and hatchery-reared salmon. Recent findings suggest, however, that such studies may underestimate the complexity of the imprinting process in nature.
Lophotoxin-Insensitive Nematode Nicotinic Acetylcholine Receptors
Authors: Tornøe Camilla , Holden-Dye Lindy , Garland Catherine , Abramson Stewart N. , Fleming John T. , Sattelle David B. 
Published: April 2021

ABSTRACT
Nematode nicotinic acetylcholine receptors (nAChRs) are molecular targets of several anthelmintic drugs. Studies to date on Caenorhabditis elegans and Ascaris suum have demonstrated atypical pharmacology with respect to nAChR antagonists, including the finding that κ-bungarotoxin is a more effective antagonist than α-bungarotoxin on Ascaris muscle nAChRs. Lophotoxin and its naturally occurring analogue bipinnatin B block all vertebrate and invertebrate nAChRs so far examined. In the present study, the effects on nematode nAChRs of bipinnatin B have been examined. The Ascaris suum muscle cell nAChR was found to be insensitive to 30 μmol l−1 bipinnatin B, a concentration that is highly effective on other nAChRs. To our knowledge, this is the first demonstration of a nAChR that is insensitive to one of the lophotoxins. Xenopus laevis oocytes injected with C. elegans polyadenylated, poly(A)+, mRNA also expressed bipinnatin-B-insensitive levamisole responses, which were, however, blocked by the nAChR antagonist mecamylamine (10 μmol l−1). In contrast to the findings for nematode receptors, bipinnatin B (30 μmol l−1) was effective in blocking mouse muscle nAChRs expressed in Xenopus laevis oocytes and native insect nAChRs. A possible explanation for insensitivity of certain nematode nAChRs to lophotoxins is advanced based on the sequence of an α-like C. elegans nAChR subunit in which tyrosine-190 (numbering based on the Torpedo californica sequence), a residue known to be critical for lophotoxin binding in vertebrate nAChRs, is replaced by a proline residue.
Body Temperatures of Free-Living African Penguins (Spheniscus Demersus) and Bank Cormorants (Phalacrocorax Neglectus)
Authors: Wilson Rory P. , Grémillet David 
Published: April 2021

ABSTRACT
Two free-living seabirds (the African penguin Spheniscus demersus and the bank cormorant Phalacrocorax neglectus) were equipped with stomach temperature-loggers to study body temperature changes during foraging. Body temperature in these endotherms was environmentally and activity-dependent and varied in the case of the cormorant by over 5 °C. Considerations of heat flux show that such flexibility confers considerable energetic advantages: by allowing body temperature to drop when the heat loss to the environment is high, such as in water, birds may save the energy that would normally be necessary to compensate for this drop. It appears that, in cormorants, low body temperature resulting from extended time in water can subsequently be elevated using solar energy when the birds return to land in a manner similar to that of ectotherms. In the better-insulated penguins, muscle-generated heat during swimming is used to re-elevate low body temperature. Continued swimming eventually causes body temperature to rise above normal resting levels so that metabolic rate could theoretically be dramatically reduced immediately post-exercise when the temperature drops to some critical level before any increase in metabolism is necessary to correct it.
Seasonal Dynamics of Dental Sexual Dimorphism in the Atlantic Stingray Dasyatis Sabina
Authors: Kajiura Stephen M. , Tricas Timothy C. 
Published: April 2021

ABSTRACT
Cartilaginous fishes continuously replace their teeth throughout their life (polyphyodonty) and often show a sexually dimorphic dentition that was previously thought to be an invariant sex character. Radial vector analysis of tooth shape in the polyphyodontic stingray Dasyatis sabina across a consecutive 24 month period shows a stable molariform morphology for females but a periodic shift in male dentition from a female-like molariform to a recurved cuspidate form during the reproductive season. The grip tenacity of the male dentition is greater for the cuspidate form that occurs during the mating season than for the molariform dentition that occurs during the non-mating season. Dental sexual dimorphism and its sex-dependent temporal plasticity probably evolved via polyphyodontic preadaptation under selective pressures on both sexes for increased feeding efficiency and sexual selection in males to maximize mating success. These phenomena are important considerations for the identification and classification of cartilaginous fishes and possibly other polyphyodontic vertebrates in the fossil record.
Photoinactivation Of An Identified Motoneurone In The Locust Locusta Migratoria
Authors: Bässler Dagmar , Rathmayer Werner 
Published: April 2021

ABSTRACT
1.The common inhibitory motoneurone 1 (CI1) in the mesothoracic ganglion of the locust was photoinactivated using a helium–cadmium laser or a mercury lamp as light source. Treated animals showed no signs of abnormal locomotory behaviour over periods of up to 40 days.
2.Photoinactivation of part of the neurone in the ganglion, i.e. the soma and the primary neurite, is sufficient to cause irreversible degeneration of all the peripheral extensions of the neurone. Three weeks after photoinactivation, all GABA immunoreactivity had disappeared from the axon branches of the photoinactivated neurone and from their terminals on one of the target muscles investigated, the anterior coxa rotator M92, and inhibitory postsynaptic potentials could no longer be elicited through stimulation. This was taken as proof of functional denervation of the muscle with regard to its inhibitory input. By this time, the axon of CI1 in nerve N3C1, which supplies M92, had also disappeared.
3.Animals treated during the fourth or fifth instars showed a permanent loss of the photoinactivated mesothoracic CI1 neurone after moulting into adulthood.
4.Denervation of M92 in the middle legs of instars and adults by axotomy of N3 always led to rapid functional reinnervation of the muscle. The first sign of reinnervation (excitatory neuromuscular activity upon mechanical stimulation of the tarsi) was detected electrophysiologically as early as 8 days after severing the motor nerve.
5.The eliminination of CI1 by photoinactivation for a period of up to 40 days did not influence parameters of the target muscle, such as size, number of fibres and phenotypes of fibres defined histochemically according to their myofibrillar ATPase isoforms, irrespective of whether the operation was performed in instars or adults. Similarly, the short period of denervation following axotomy before reinnervation took place did not affect the fibre type composition of the muscle.
Short-Range Orientation In Electric Fish: An Experimental Study Of Passive Electrolocation
Authors: Shieh Kwang-Tze , Wilson Willard , Winslow Michael , McBRIDE Don W. , Hopkins Carl D. 
Published: April 2021

ABSTRACT
Gymnotiform electric fish are capable of locating and approaching an electrically discharging conspecific over a range of 1–2 m in a behavior called passive electrolocation. This paper investigates the movements of two species in experiments with approaches to stationary dipoles that are either silenced or jumped to a new direction during an approach.
Gymnotus carapo fail to find an electrode source in trials in which the dipole electrode is switched off in mid-track. They slow their approach, become disoriented and drift away from the target within seconds of the field being switched off. This result suggests that the fish are unable to construct a cognitive map of a dipole source from brief exposure to local electrosensory stimuli.
The second set of trials shows that Brachyhypopomus diazi and Gymnotus carapo bend their body to track electric vectors which are suddenly jumped to a new direction. The latency of the bend response is 0.5 s after the jump. Bending initiates a turn that reduces to zero the error between the fish’s direction and the electric field vector and helps keep the fish aligned with the local electric field vector. Together, these experiments suggest that passive electrolocation is stimulus-bound and that these fish find the electrical sources simply by tracking instantaneous local electric current vectors.
Multiple High-Affinity Binding Sites for [3H]Serotonin in the Brain of a Teleost Fish, the Arctic Charr (Salvelinus Alpinus)
Authors: Winberg Svante , Nilsson Göran E. 
Published: April 2021

ABSTRACT
Binding of [3H]serotonin (5-HT) to membranes prepared from Arctic charr brain homogenates was most consistent with a one-site model for [3H]5-HT binding, with KD and Bmax values of 5.7±0.3 nmol l−1 and 60.7±7.3 fmol mg−1 protein, respectively. Similarly, 5-HT displacement of [3H]5-HT was best explained by a monophasic model with an apparent Ki of 4.3±0.7 nmol l−1. The ability of a number of synthetic 5-HT receptor ligands to displace [3H]5-HT was studied. 8OH-DPAT was found to interact with three [3H]5-HT binding sites, whereas buspirone, TFMPP, spiperone and mianserin all distinguish two sites. In the presence of 300 nmol l−1 buspirone, 8OH-DPAT and mianserin distinguished two [3H]5-HT binding sites, whereas spiperone interacted with only one. Moreover, 8OH-DPAT differentiated three [3H]5-HT binding sites even in the presence of 0.5 mmol l−1 GTP, making it unlikely that these sites represent different affinity states of G-protein-coupled receptors. GTP had no effect on apparent Ki values for 8OH-DPAT, but reduced the Bmax value of the high-affinity site by 60 %. GTP had a similar effect on the saturation binding curve for [3H]5-HT, reducing Bmax by approximately 50 %, whereas KD was unaffected. The results provide evidence for at least three different high-affinity [3H]5-HT binding sites, one of them showing a pharmacological profile strikingly similar to that of the mammalian 5-HT1A receptor.