bluuebunny/crossref_metadata_2025_split huggingface dataset:
The role of orientation flights on homing performance in honeybees
Authors: Capaldi Elizabeth A. , Dyer Fred C. 
Published: April 2021

ABSTRACT
Honeybees have long served as a model organism for investigating insect navigation. Bees, like many other nesting animals, primarily use learned visual features of the environment to guide their movement between the nest and foraging sites. Although much is known about the spatial information encoded in memory by experienced bees, the development of large-scale spatial memory in naive bees is not clearly understood. Past studies suggest that learning occurs during orientation flights taken before the start of foraging. We investigated what honeybees learn during their initial experience in a new landscape by examining the homing of bees displaced after a single orientation flight lasting only 5 — 10 min. Homing ability was assessed using vanishing bearings and homing speed. At release sites with a view of the landmarks immediately surrounding the hive, ‘first-flight’ bees, tested after their very first orientation flight, had faster homing rates than ‘reorienting foragers’, which had previous experience in a different site prior to their orientation flight in the test landscape. First-flight bees also had faster homing rates from these sites than did ‘resident’ bees with full experience of the terrain. At distant sites, resident bees returned to the hive more rapidly than reorienting or first-flight bees; however, in some cases, the reorienting bees were as successful as the resident bees. Vanishing bearings indicated that all three types of bees were oriented homewards when in the vicinity of landmarks near the hive. When bees were released out of sight of these landmarks, hence forcing them to rely on a route memory, the ‘first-flight’ bees were confused, the ‘reorienting’ bees chose the homeward direction except at the most distant site and the ‘resident’ bees were consistently oriented homewards.
Blood pressure regulation during hypotension in two teleost species: differential involvement of the renin–angiotensin and adrenergic systems
Authors: Bernier Nicholas J. , McKendry John E. , Perry Steve F. 
Published: April 2021

ABSTRACT
The stimulatory effects of angiotensin II (Ang II) on catecholamine release and the contributions of the renin–angiotensin system, humoral catecholamines and adrenergic nerves to blood pressure regulation were investigated in rainbow trout (Oncorhynchus mykiss) and American eel (Anguilla rostrata). In trout, bolus injections of homologous [Asn1,Val5]-Ang II (100 or 500 pmol kg−1) increased catecholamine secretion rates and plasma catecholamine concentrations from in situ posterior cardinal vein preparations and chronically cannulated fish, respectively. In contrast, in situ or in vivo injections of similar doses of Ang II in eel did not affect catecholamine release. α-Adrenoceptor blockade (prazosin; 1 mgkg−1) reduced the pressor effect of exogenous Ang II (500 pmol kg−1) in both species. In eel, intravenous injection of the smooth muscle relaxant papaverine (10 mg kg−1) elicited a rapid decrease in dorsal aortic pressure (PDA; 58 %) followed by a gradual recovery back to the baseline value 85 min after the treatment. In trout, papaverine elicited a similar decrease in blood pressure (62 %); however, PDA recovered fully 20 min after treatment. Blockade of either α-adrenoceptors with prazosin or adrenergic nerves with bretylium (10 mg kg−1) prior to papaverine treatment did not alter PDA recovery in eel. In trout, α-adrenoceptor and adrenergic nerve blockade prior to the papaverine treatment prevented and attenuated PDA recovery, respectively. In both species, papaverine treatment elicited significant increases in plasma catecholamine and Ang II concentrations. However, the increases in plasma catecholamine concentrations were markedly greater in trout than in eel. Similarly, the papaverine-elicited increase in plasma Ang II levels occurred earlier and was greater in trout than in eel. Thus, while Ang II stimulates humoral catecholamine release in trout, there is no evidence for a similar interaction in eel. Moreover, during hypotensive stress, although the renin–angiotensin system is recruited in both species, an essential involvement of adrenergic nerves and humoral catecholamines in the restoration of blood pressure is only apparent in trout.
Hiding responses of locusts to approaching objects
Authors: Hassenstein Bernhard , Hustert Reinhold 
Published: April 2021

ABSTRACT
Locusts, Locusta migratoria, sitting on a plant stem hide from dark moving or expanding shapes in their environment. The fore- and middle legs perform this avoidance response by making lateral tilting movements, while the hindlegs slide laterally and guide rotation of the posterior body over the stem. During larger turns, the legs take lateral steps when lateral tilting is limited by the joints. Slow hiding movements of less than 300 ° s−1 of angular velocity are induced by slowly changing (looming) shapes, and interposed stops or slowing of the movement can delay the progress of this hiding manoeuvre. Fast hiding movements with angular velocities between 120 ° s−1 and 860° s−1 proceed continuously and rapidly in response to rapidly expanding stimuli. Hiding responses to expanding shapes occur only after the expanding image has exceeded a threshold visual angle of 8–9.5 °. Hiding response latencies range between 220 ms and 1.2 s for fast hiding and are approximately 1.2 s for most slow hiding responses. Predator-avoidance responses such as freezing, jerking, crouching, walking backwards, dropping or jumping can be used instead of or in conjunction with hiding behaviour. We conclude that the fast hiding behaviour of locusts is a specific goal-directed type of optomotor behaviour requiring positional information from small-field detectors of shape expansion in the interneurone layers of the locust eye.
Fenestration nodes and the wide submyelinic space form the basis for the unusually fast impulse conduction of shrimp myelinated axons
Authors: Xu (Ke Hsu) Ke , Terakawa Susumu 
Published: April 2021

ABSTRACT
Saltatory impulse conduction in invertebrates is rare and has only been found in a few giant nerve fibres, such as the pairs of medial giant fibres with a compact multilayered myelin sheath found in shrimps (Penaeus chinensis and Penaeus japonicus) and the median giant fibre with a loose multilayered myelin sheath found in the earthworm Lumbricus terrestris. Small regions of these nerve fibres are not covered by a myelin sheath and serve as functional nodes for saltatory conduction. Remarkably, shrimp giant nerve fibres have conduction speeds of more than 200 m s−1, making them among the fastest-conducting fibres recorded, even when compared with vertebrate myelinated fibres. A common nodal structure for saltatory conduction has recently been found in the myelinated nerve fibres of the nervous systems of at least six species of Penaeus shrimp, including P. chinensis and P. japonicus. This novel node consists of fenestrated openings that are regularly spaced in the myelin sheath and are designated as fenestration nodes. The myelinated nerve fibres of the Penaeus shrimp also speed impulse conduction by broadening the gap between the axon and the myelin sheath rather than by enlarging the axon diameter as in other invertebrates. In this review, we document and discuss some of the structural and functional characteristics of the myelinated nerve fibres of Penaeus shrimp: (1) the fenestration node, which enables saltatory conduction, (2) a new type of compact multilayered myelin sheath, (3) the unique microtubular sheath that tightly surrounds the axon, (4) the extraordinarily wide space present between the microtubular sheath and the myelin sheath and (5) the main factors contributing to the fastest impulse conduction velocity so far recorded in the Animal Kingdom.
The distribution of a crf-like diuretic peptide in the blood-feeding bug Rhodnius prolixus
Authors: Brugge V. A. Te , Miksys S. M. , Coast G. M. , Schooley D. A. , Orchard I. 
Published: April 2021

ABSTRACT
The blood-feeding bug Rhodnius prolixus ingests a large blood meal, and this is followed by a rapid diuresis to eliminate excess water and salt. Previous studies have demonstrated that serotonin and an unidentified peptide act as diuretic factors. In other insects, members of the corticotropin-releasing factor (CRF)-related peptide family have been shown to play a role in post-feeding diuresis. Using fluorescence immunohistochemistry and immunogold labelling with antibodies to the Locusta CRF-like diuretic hormone (Locusta-DH) and serotonin, we have mapped the distribution of neurones displaying these phenotypes in R. prolixus. Strong Locusta-DH-like immunoreactivity was found in numerous neurones of the central nervous system (CNS) and, in particular, in medial neurosecretory cells of the brain and in posterior lateral neurosecretory cells of the mesothoracic ganglionic mass (MTGM). Positively stained neurohaemal areas were found associated with the corpus cardiacum (CC) and on abdominal nerves 1 and 2. In addition, Locusta-DH-like immunoreactive nerve processes were found over the posterior midgut and hindgut. Double-labelling studies for Locusta-DH-like and serotonin-like immunoreactivity demonstrated some co-localisation in the CNS; however, no co-localisation was found in the medial neurosecretory cells of the brain, the posterior lateral neurosecretory cells of the MTGM or neurohaemal areas. To confirm the presence of a diuretic factor in the CC and abdominal nerves, extracts were tested in Malpighian tubule secretion assays and cyclic AMP assays. Extracts of the CC and abdominal nerves caused an increase in the rate of secretion and an increase in the level of cyclic AMP in the Malpighian tubules of fifth-instar R. prolixus. The presence of the peptide in neurohaemal terminals of the CC and abdominal nerves that are distinct from serotonin-containing terminals indicates that the peptide is capable of being released into the haemolymph and that this release can be independent of the release of serotonin.
An interneurone of unusual morphology is tuned to the female song frequency in the bushcricket Ancistrura nigrovittata (Orthoptera, Phaneropteridae)
Authors: Stumpner Andreas 
Published: April 2021

ABSTRACT
The interneurone AN5-AG7 of the duetting bushcricket Ancistrura nigrovittata has its soma in the seventh (penultimate) abdominal ganglion. Its major postsynaptic arborizations with dense thin branches of smooth appearance are found in the prothoracic ganglion. The branches terminate in the auditory neuropile, predominantly at the same location as those auditory receptors that respond best to the female song frequency. Correspondingly, AN5-AG7 responds preferentially to frequencies between 24 and 28 kHz, thereby matching the carrier frequency of the female response song quite well. At frequencies below 24 kHz, AN5-AG7 receives inhibition, which is sometimes seen as clear inhibitory postsynaptic potentials. At these frequencies, thresholds of excitatory postsynaptic potentials are considerably lower than spike thresholds. In contrast, above 20 kHz, the two thresholds match and they correspond to the behavioural threshold. The AN5-AG7 interneurone is more sensitive to soma-contralateral stimuli and it receives predominantly inhibition, but also some excitation, from the soma-ipsilateral ear. Response strength is not greatly affected by stimulus duration but shows prominent habituation. This habituation depends only weakly on intensity and frequency. Some AN5-AG7 interneurones show very small graded potentials and no spiking responses to any acoustic stimuli.
Muscle growth and development in atlantic cod larvae (Gadus morhua L.) related to different somatic growth rates
Authors: Galloway Trina F. , Kjørsvik Elin , Kryvi Harald 
Published: April 2021

ABSTRACT
The present study describes the development of the axial musculature in first-feeding larvae of Atlantic cod (Gadus morhua L.) with different somatic growth rates achieved by using different nutritional conditions. Muscle growth was assessed by determining the number of muscle fibres (hyperplasia) and the growth of existing fibres (hypertrophy). Larvae were fed rotifers containing a high (1.4; treatment 1) or low (0.2; treatment 2) ratio of docosahexaenoic acid to eicosapentaenoic acid from day 5 after hatching. From day 17, the larvae were fed Artemia nauplii with the same enrichment in both treatments. Treatment 1 gave the highest somatic growth rate and hence the highest dry mass at the end of the experiment, but no difference in larval standard length was found between treatments. In slow-growing larvae, higher priority was thus put into reaching a certain length than into increasing muscle mass.
The largest fibres, which were present from hatching, increased in cross-sectional area during larval development, but no differences were found between treatments in the cross-sectional area of individual fibres or the total cross-sectional area of these fibres at the end of the experiment. The first white recruitment fibres were observed at the dorsal and ventral apices of the myotome at approximately the onset of first feeding (larval length 4.5 mm). In larvae 8.5 mm long, the total cross-sectional area of white muscle fibres in the treatment 2 group was 75 % of that in the treatment 1 group. The highest somatic growth rate was associated with an increased contribution of hyperplasia to axial white muscle growth. In the faster-growing larval group, the relative contribution of hyperplasia to the total white muscle cross-sectional area was 50 %, whereas it was 41 % in the slower-growing larval group. The subsequent growth potential may thus be negatively affected by inadequate larval feeding.
Red muscle activation patterns in yellowfin (Thunnus albacares) and skipjack (Katsuwonus pelamis) tunas during steady swimming
Authors: Knower Torre , Shadwick Robert E. , Katz Stephen L. , Graham Jeffrey B. , Wardle Clement S. 
Published: April 2021

ABSTRACT
To learn about muscle function in two species of tuna (yellowfin Thunnus albacares and skipjack Katsuwonus pelamis), a series of electromyogram (EMG) electrodes was implanted down the length of the body in the internal red (aerobic) muscle. Additionally, a buckle force transducer was fitted around the deep caudal tendons on the same side of the peduncle as the electrodes. Recordings of muscle activity and caudal tendon forces were made while the fish swam over a range of steady, sustainable cruising speeds in a large water tunnel treadmill. In both species, the onset of red muscle activation proceeds sequentially in a rostro-caudal direction, while the offset (or deactivation) is nearly simultaneous at all sites, so that EMG burst duration decreases towards the tail. Muscle duty cycle at each location remains a constant proportion of the tailbeat period (T), independent of swimming speed, and peak force is registered in the tail tendons just as all ipsilateral muscle deactivates. Mean duty cycles in skipjack are longer than those in yellowfin. In yellowfin red muscle, there is complete segregation of contralateral activity, while in skipjack there is slight overlap. In both species, all internal red muscle on one side is active simultaneously for part of each cycle, lasting 0.18T in yellowfin and 0.11T in skipjack. (Across the distance encompassing the majority of the red muscle mass, 0.35–0.65L, where L is fork length, the duration is 0.25T in both species.) When red muscle activation patterns were compared across a variety of fish species, it became apparent that the EMG patterns grade in a progression that parallels the kinematic spectrum of swimming modes from anguilliform to thunniform. The tuna EMG pattern, underlying the thunniform swimming mode, culminates this progression, exhibiting an activation pattern at the extreme opposite end of the spectrum from the anguilliform mode.
Neurochemical control of cricket stridulation revealed by pharmacological microinjections into the brain
Authors: Wenzel B. , Hedwig B. 
Published: April 2021

ABSTRACT
Neuroactive substances were administered into the frontal protocerebrum of tethered male Gryllus bimaculatus by pressure injections from microcapillaries. All three types of species-specific song pattern (calling song, rivalry song and courtship song) could be elicited by injection of acetylcholine and cholinergic agonists. Injection of nicotine led to short bouts of calling song that occurred after a short latency. In contrast, muscarine elicited long-lasting stridulation that took longer to develop. The pharmacologically induced song patterns showed transitions from rivalry song to calling song and from calling song to courtship song, which also occur during natural behaviour. Stridulation induced by a cholinergic agonist could be immediately blocked by microinjection of γ-aminobutyric acid (GABA) into the same neuropile sites. Administration of picrotoxin in resting crickets led to enhanced motor activity that incorporated the three different song patterns. We propose that, in the brain of the cricket, acetylcholine and GABA are putative transmitters involved in the control of stridulation. Histological analysis located the stimulation sites to an area between the pedunculus and the α-lobe of the mushroom body in which the command neurons for calling song have dendritic arborizations.
What determines the bending strength of compact bone?
Authors: Currey John D. 
Published: April 2021

ABSTRACT
The bending strength of a wide variety of bony types is shown to be nearly linearly proportional to Young’s modulus of elasticity/100. A somewhat closer and more satisfactory fit is obtained if account is taken of the variation of yield strain with Young’s modulus. This finding strongly suggests that bending strength is determined by the yield strain. The yield stress in tension, which might be expected to predict the bending strength, underestimates the true bending strength by approximately 40 %. This may be explained by two phenomena. (1) The post-yield deformation of the bone material allows a greater bending moment to be exerted after the yield point has been reached, thereby increasing the strength as calculated from beam formulae. (2) Loading in bending results in a much smaller proportion of the volume of the specimens being raised to high stresses than is the case in tension, and this reduces the likelihood of a weak part of the specimen being loaded to failure.
Effects of sea water and stanniectomy on branchial Ca2+ handling and drinking rate in eel (Anguilla anguilla L.)
Authors: Van Der Heijden A. J. H. , Verbost P. M. , Bijvelds M. J. C. , Atsma W. , Bonga S. E. Wendelaar , Flik G. 
Published: April 2021

ABSTRACT
We examined the effects of seawater adaptation and extirpation of the Stannius corpuscles on branchial Ca2+ flows, gill plasma membrane Ca2+ transporters and drinking rate of European eels, Anguilla anguilla. Transepithelial Ca2+ inflow in the gills increased 2 weeks after transfer of the eels from fresh water to sea water and after stanniectomy. Neither of these treatments changed the membrane density or the affinity of the Ca2+-extrusion mechanisms (Ca2+-ATPase and Na+/Ca2+-exchanger) in the gill cells, as measured in basolateral plasma membrane vesicles. We conclude that the increase in the Ca2+-transporting capacity observed in the gills of fish exposed to the larger transepithelial Ca2+ fluxes, resulting from exposure to sea water or stanniectomy, involves an increase in number and/or size of the Ca2+-transporting cells, but not in the membrane density of Ca2+ transporters. Branchial Ca2+ outflow was higher in stanniectomised than in sham-operated fish. Changes in electrochemical driving forces as well as plasma stanniocalcin or teleocalcin levels may be the basis for the observed differences. Stanniectomy enhanced drinking in stanniectomised eels. Drinking was not further affected by transfer to sea water. These observations suggest that the corpuscles of Stannius are involved in the water balance.
Reflex and muscular adaptations in rat soleus muscle after hindlimb suspension
Authors: Anderson Judith , Almeida-Silveira Maria I. , Pérot Chantal 
Published: April 2021

ABSTRACT
Reflex, mechanical and histochemical adaptations of the soleus muscle following 3 weeks of hindlimb suspension (HS) were measured in the rat. HS transformed the soleus muscle fibre type composition from predominantly slow, type I, to approximately equal proportions of fast, type II and slow fibres. Consistent with this transformation was an increase in the maximum shortening velocity, Vmax, and a decrease in the stiffness of the series elastic component. Disuse also produced muscle atrophy and a resultant decrease in twitch and tetanic force. Reflex responses of the ankle extensors were also obtained at 5 and 9 weeks of age for six control rats (C group) and six rats subjected to HS for 3 weeks (HS group). The soleus reflexes to a mechanical tap applied to the Achilles tendon (T reflex) and to an electrical stimulation of the sciatic nerve (H reflex) were measured. The maximal amplitude of these reflexes (Tmax and Hmax) were normalised to the maximal direct motor response (Mmax) and the Tmax/Hmax ratio was also calculated to give an index of the relative adaptations of the peripheral and central components of the reflex pathway. The HS group showed significantly higher H reflex gains than the C group, possibly due to changes in synaptic efficiency after HS. Conversely, the HS group presented strongly inhibited T reflexes and negative gains for the Tmax/Hmax ratios. This result indicated a reduced spindle solicitation after HS, which may reflect changes in the spindle sensitivity itself, but it could also be due to the decrease in stiffness of the musculo–tendinous elements in series with the muscle spindles. Such mechanical changes may play an important part in the decreased T reflex responses.
The synaptic junctions of LE and RF cluster sensory neurones of Aplysia californica are differentially modulated by serotonin
Authors: Storozhuk Maksim V. , Castellucci Vincent F. 
Published: April 2021

ABSTRACT
The monosynaptic component of withdrawal reflexes in Aplysia californica, from sensory neurones to motor neurones, is a critical site of the synaptic modulation occurring during short-term and long-term behavioural changes. There are four clusters of sensory neurones (LE, rLE, RE, RF) innervating the receptive field for the gill and siphon withdrawal reflex. The receptive fields of these cells are located on the siphon, the mantle, the branchial cavity and the gill itself. In most studies, the synapses made by the sensory neurones of the LE cluster of the abdominal ganglion or the VC cluster of the pleural ganglion have been investigated and shown to be facilitated by the neuromodulator serotonin (5-hydroxytryptamine, 5-HT). In this report, we have examined the effect of 5-HT on the synaptic junctions of the RF cluster neurones. The duration of action potentials in these cells, unlike those of the other clusters, is barely affected by serotonin.
We found that while the LE synapses are facilitated by 5-HT (10 μmol l−1), the RF synapses are not. In fact, the RF–L14 connections are actually depressed by 5-HT; this effect is not due to shunting in the postsynaptic neurone. The RF–L7 connections are also depressed by 5-HT, although the effect is smaller. The RF–L14 connections are blocked by the non-NMDA receptor agonist CNQX (100 μmol l−1), suggesting that the transmitter and the postsynaptic receptors involved are similar to those present on the LE or VC cluster cells. The absence of serotonin-induced facilitation of the RF cluster cells may provide the animal with a means of reducing the nonspecific effects of aversive sensitization and therefore of allowing a greater specificity and more flexibility in plastic behavioural changes.