bluuebunny/crossref_metadata_2025_split huggingface dataset:
Delayed Initiation of SS1 Pulses in the Sea Anemone Calliactis Parasitica: Evidence for A Fourth Conducting System
Authors: Jackson A. J. , McFarlane I. D. 
Published: April 2021

ABSTRACT
Single electrical shocks to the column sometimes elicit a series of 1−6 pulses in the SS1 (ectodermal slow system) but the first pulse does not appear until 5−28 s after stimulation. These pulses occur in addition to the early SS1 pulse which follows every shock and which has a conduction delay of less than 1 s. The threshold of the delayed SS1 response is different from the thresholds of the three known conducting systems (through-conducting nerve net, SS1, and SS2). In the case of stimulation of the column, the delayed SS1 pulses do not arise at the point of stimulation but probably originate in the tentacles or upper column. The pulse origin can shift during a single burst. The pathway from the point of stimulation to the site of origin of delayed SS1 pulses is endodermal. We propose that this pathway represents a fourth conducting system (Delayed Initiation System − DIS). The DIS must connect, across the mesogloea, with the ectodermal SS1. The long pulse delay and repetitive firing may derive from pacemaker activity in the DIS. The DIS pacemakers closely resemble the pacemakers connected to the through-conducting nerve net. The DIS may be neuronal. Delayed SS1 pulse bursts from unattached anemones showed an earlier onset, and more pulses/burst, than those from attached anemones. Delayed SS1 pukes can also be evoked by electrical, and in some cases mechanical, stimulation of the pedal disc, tentacles, and pharynx, but there are regional differences in the number of pulses evoked, in their delay, and in their site of origin.
Passive Exchanges During Water Vapour Absorption in Mealworms (Tenebrio Molitor): A New Approach to Studying the Phenomenon
Authors: Machin John 
Published: April 2021

ABSTRACT
The weights of single mealworms were continuously recorded at 20 °C during exposure to periods of constant humidity and to abrupt changes in atmospheric vapour pressure. Two exchange stages were recognized in each animal. Weight changes were either limited to slow losses, suggesting transpiration through the external cuticle, or showed more rapid humidity dependent gains as well as losses. Rapid exchanges indicated that water was gained or lost through permeable barriers, from a fluid compartmet of significantly lower vapour pressure than the haemolymph, equivalent to about 90% R.H. Weight gains and losses during humidity changes provided evidence of a significant, passively exchanging fluid compartment located between the exchange surface and absorbing mechanism. Weight changes in faecal pellets following their elimination provide further support for a rectal site of atmospheric absorption.
The location and mechanism of hyperosmotic fluid secretion in the rectum of the saline-water mosquito larvae Aedes taeniorhynchus
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Authors: Bradley T. J. , Phillips J. E. 
Published: April 2021

ABSTRACT
Ligation between the anterior and posterior segments of the rectum in vitro was used to demonstrate that the posterior rectum is the site of hyperosmotic secretion to the lumen side. Observations were consistent with a reabsorptive function for the anterior rectum. These results support predictions from ultrastructural studies of these two segments. The initial potential of the rectal lumen, relative to the haemocoel side, was of opposite polarity in the anterior (− 10 mV) and posterior (+10 mV) segments and these values decreased to − 2 and + 6 mV respectively in ligated recta which had secreted for 2 h. A comparison of these potential difference measurements with concentration differences developed across the rectal epithelium under the same experimental conditions indicates that Na+, K+, Mg2+, and Cl− are all actively transported by the posterior segment to the lumen side. The influence of different haemolymph concentrations of Na+, K+, and Cl− on the potential differences across the basal cell border and across the whole rectal epithelium are reported. Based on this and previous data, we propose a model for the organization of transport processes within the single celltype present in the posterior rectal epithelium.
The mechanism for co-ordinating metachronal limb movements between joined male and female Artemia salina during precopulatory behaviour
Authors: Lent Charles M. 
Published: April 2021

ABSTRACT
Male and female Artemia salina swim in tandem pairs before copulation and during this period the metachronal rhythms of the individuals are entrained. Artemia entrain to pulsatile water stimulation of the head at frequencies between 4 and 6 Hz. The antennules are mechano-sensitive. Antennular responsiveness to phasic input is very probably the actual mechanism by which interorganism co-ordination is achieved, as mechano-stimulation of other Artemia structures, electro-stimulation and photo-stimulation are ineffective modes of entraining metachronal movements.
EGG Diapause in Ephippiger Cruciger (Orthoptera: Tettigoniidae): I. The Incidence, Variable Duration and Elimination of the Initial Diapause
Authors: Dean R. L. , Hartley J. C. 
Published: April 2021

ABSTRACT
Eggs of the bush-cricket Ephippiger cruciger may be subject to two periods of diapause during the course of embryogenesis. After oviposition not all eggs develop at temperatures favourable to morphogenesis, some cease activity at the unsegmented embryonic primordium stage. If these eggs are cooled for 10–30 days some develop on subsequent exposure to higher temperatures, but further prolongation of the cooling period does not render more eggs competent to develop. Although cooling for longer than the critical period does not affect the proportion of eggs which subsequently start to develop, it does affect the time within which reactivated eggs begin to develop. The delay in the initiation of development after cooling increases with the duration of the chilling period. Excessively long cooling periods, however, impair the eggs’ ability to complete embryogenesis. It is evident that eggs laid in one season will develop and hatch over a number of years.
The locust jump. I. The motor programme
Authors: Heitler W. J. , Burrows M. 
Published: April 2021

ABSTRACT
A motor programme is described for defensive kicking in the locust which is also probably the programme for jumping. The method of analysis has been to make intracellular recordings from the somata of identified motorneurones which control the metathoracic tibiae while defensive kicks are made in response to tactile stimuli. Three stages are recognized in the programme.
Initial flexion of the tibiae results from the low spike thresholds of tibial flexor motorneurones to tactile stimulation of the body. Co-contraction of flexor and extensor muscles follows in which flexor and extensor excitor motorneurones spike at high frequency for 300–600 ms. Flexor inhibitory motorneurones are inhibited. The flexor muscle thus holds the tibia flexed while the extensor muscle develops tension isometrically to the level required for a kick or jump. activity terminates the co-contraction by inhibiting the flexor excitor motorneurones and simultaneously exciting the flexor inhibitors. This causes relaxation of the flexor muscle and allows the tibiae to extend. If the trigger activity does not occur, the jump or kick is aborted, and the tibiae remain flexed.
The mauthner-initiated startle response in teleost fish
Authors: Eaton Robert C. , Bombardieri Rocco A. , Meyer Dietrich L. 
Published: April 2021

ABSTRACT
A characteristic behaviour, the ‘Mauthner-initiated startle response’, was recorded and quantitatively analysed with high-speed cinematography (200 frames/sec) after vibrational stimulation in 11 of 13 teleost species which possess Mauthner cells. The latency of the response is 5–10 msec. This behaviour has: (a) an initial phase, the ‘fast-body-bend’, lasting about 20 msec and consisting of a stereotyped displacement of the head and tail to one side and (b), a second phase, the ‘return-flip ‘, consisting of a non-stereotyped flip of the tail to the opposite side. Within 100 msec after the start of the Mauthner-initiated startle response, most fish were displaced 0·5–1·5 body lengths from their initial position. The variability of the animal’s location after 100 msec suggests that the behaviour is adaptively non-predictable. In goldfish, the Mauthner-initiated startle response could also be elicited by visual stimulation. We conclude that the fast-body-bend is the direct result of activation of one Mauthner cell and its spinal motor neurone pool. In four species we described examples of apparently non-Mauthner initiated startle responses.
Studies on the Action of Biogenic Amines on Cockroach Heart
Authors: Collins C. , Miller T. 
Published: April 2021

ABSTRACT
Measurement of the beat of the semi-isolated cockroach heart, by impedance conversion, showed that the whole abdominal heart of large nymphs or adults responded to low concentrations of acetylcholine (ACh) or 5-hydroxytryptamine (5-HT) by increasing the rate of heartbeat. Preparations, which included 2-chamber sections of the abdominal heart, showed vastly reduced responses to ACh compared to the responses of the whole abdominal heart. Responses to 5-HT were similar in both preparations. Following assay with 5-HT, the cockroach heartbeat often developed marked regularity. ACh assays produced such regularity only rarely. The sectioned cockroach heart preparation was decreasingly responsive to 5-HT &gt; synephrine &gt; octopamine &gt; tryptamine &gt; dopamine &gt; tyramine. Dose-response curves revealed that the antagonist 501 c interacted competitively with 5-HT on the cockroach heart preparation. 501 c appeared to be a non-competitive antagonist to octopamine, suggesting that 5-HT and octopamine act at separate receptor sites on the myocardium. Experiments in which solutions of dibutyryl cyclic AMP, dibutyryl cyclic GMP, or aminophylline were continuously perfused on the cockroach heart, failed to establish that cyclic nucleotides mediate neurotransmitter or hormone action on this tissue. Cockroach hearts were not responsive to prostaglandin E1, F1, picrotoxin, L-glutamate, or ATP below 10−3-10−4M doses.
The Role of Neurosecretion in the Photoperiodic Control of Polymorphism in the Aphid Megoura Viciae
Authors: Steel C. G. H. , Lees A. D. 
Published: April 2021

ABSTRACT
The location of the photoperiodic mechanism controlling the production of the sexual and parthenogenetic morphs by apterous parents was examined by selectively injuring the brain with an R.F. microcautery. Lesions destroying the Group I neurosecretory cells (NSC) in the protocerebrum abolished the response to changed daylength. Extensive damage to other NSC Groups, to the compound eyes and optic lobes was without effect. It is concluded that the Group I NSC are the effectors, secreting a virginoparapromoting substance; in its absence only oviparae are produced. Areas slightly lateral to the Group I NSC are also required for the long-day response, indicating that this is the probable site of the neuronal photoperiodic clock which regulates the release of neurosecretory material (NSM) from the Group I cells.
Behavioural Thresholds for Diffuse Illumination in the Goldfish
Authors: Tavolga William N. 
Published: April 2021

ABSTRACT
Thresholds for diffuse, broad-band illumination were obtained for the goldfish (Carassius auratus) by avoidance conditioning. The light source was a television cathode-ray tube whose output was controlled over a range of 140 dB by a combination of ‘brightness’ control, blanking of scan lines, and neutral density filters. The threshold was calculated in terms of irradiance to be 2·9 ×10−6μW cm−2 (± a standard deviation of 1·4). The determination of absolute, rather than relative, values, and the use of overhead, diflfuse illumination provided data that would be ecologically and behaviourally relevant.
Effects of Median-Fin Amputation on Fast-Start Performance of Rainbow Trout (Salmo Gairdneri)
Authors: Webb P. W. 
Published: April 2021

ABSTRACT
Fast-start performance of eight groups of rainbow trout with various fin-rays removed was measured to test the hydromechanical theory (Weihs, 1973) that large fins are required for acceleration. A trend towards decreasing performance was found for the following sequence of fin-ray amputations: control (pelvic rays amputated); dorsal fin; anal fin; dorsal lobe of caudal fin and ventral lobe of caudal fin; ventral lobe of caudal fin and anal fin; dorsal and ventral lobes of caudal fin; both caudal-fin lobes and anal fin. The series represents progressive reduction in fin and body area, as well as reduction in these areas where lateral movements are largest. Effects of fin amputation on performance were statistically significant (P &gt; 0·05) in comparison with controls only for the last three groups lacking the caudal fin. The results confirm the hydromechanical theory, and lead to the conclusion that mechanically optimum lateral body profiles for faststart and for steady (cruising and sprint) performance are mutually exclusive. This mechanical restriction can be circumvented only in bony fish, with the evolution of flexible, collapsible fins that permit major variation in lateral body profile.
Bursting Pacemaker Activity in the Solitary Hydroid Tubularia Solitaria
Authors: De Kruijf H. A. M. 
Published: April 2021

ABSTRACT
Spontaneous electrical activity recorded from solitary Tubularia solitaria Warren consisted of long bursts of potentials regularly alternating with series of short bursts. Hydranth pulse (HP) systems in isolated hydranths produce a pulse pattern similar to that in intact animals though at a much lower frequency. Stalk pulse (SP) systems in isolated stalks produced extremely regular bursts of pulses resembling bursting patterns in molluscan single neurones. The bursts were associated with strong bending movements. In contrast with hierarchies in other hydroids, T. solitaria’s HP system dominates the SP system.
Excised parts of the stalk produced bursting patterns. Interburst-and interpulse intervals were longer in these parts than in the whole stalk. Numbers of pulses per burst and overall pulse frequency were highest in the most distal part of the stalk, and lowest in the most proximal part.
Urine Production Rate and Water Balance in the Terrestrial Crabs Gecarcinus Lateralis and Cardisoma Guanhumi
Authors: Harris R. R. 
Published: April 2021

ABSTRACT
The rate of urine production in the terrestrial crabs Gecarcinus lateralis (Freminville) and Cardisoma guanhumi Latreille maintained on s.w.-moist sand was measured by inulin clearance. The inulin U/B ratios in both species rose to about unity after 48 h, and remained at this level. It was concluded that neither species withdrew water from the primary urine. The relatively high rate of inulin clearance in G. lateralis (10·69 % body wt day−1) was considerably reduced when animals were transferred to dry sand (2·15 % body wt day−1). The rate of water loss on dry sand was measured in G. lateralis and changes in the haemolymph and urine osmolality recorded. The prevention of possible reabsorption of water from voided urine did not appear to affect significantly the rate of water loss in conditions of water deprivation. The maintenance of urine production rates measured on s.w.-moist sand would double the water loss of G. lateralis in dry conditions.
Body Colour Changes Induced by Spinal Thermal Stimulation of the Crucian Carp (Carassius Carassius)
Authors: Nagai M. , Iriki M. , Iwata K. S. 
Published: April 2021

ABSTRACT
Body colour changes of the crucian carp during spinal thermal stimulation were recorded photoelectrically. Warming the spinal cord induced darkening, whereas cooling induced lightening of body colour. After transection of the medulla oblongata posterior to the vagal lobe, the same colour responses as in intact fish were induced, apart from one of the seven responses to spinal cooling. After spinal pithing, thermal stimulation of the spinal cord failed to induce the responses. The present responses are considered to indicate influence of spinal thermal stimulation on the cutaneous sympathetic systems of this fish.
Metabolic and Tissue Solute Changes Associated with Changes in the Freezing Tolerance of the Bivalve Mollusc Modiolus Demissus
Authors: Murphy Dennis J. 
Published: April 2021

ABSTRACT
A physiological mechanism responsible for increasing the freezing tolerance of the bivalve Modiolus demissus (Dillwyn) following low-temperature acclimation was demonstrated. The rates of oxygen consumption of M. demissus acclimated to temperatures between o and 24 °C were presented as an Arrhenius plot. A change in slope occurred at 10 °C, suggesting that temperature alone was not responsible for the increased decline in the rate of oxygen consumption below 10 °C. Low-temperature acclimation had no effect on blood Na+ or K+ concentrations but did reduce the concentration of blood Mg2+ and, in addition, resulted in the accumulation of end-products characteristic of anaerobic metabolism -tissue alanine and proline, and blood Ca2+. Furthermore, maintenance of M. demissus under anaerobic conditions increased freezing tolerance. Taken together, these data indicate that the increased freezing tolerance of M. demissus acclimated to low temperatures involves a conversion to anaerobic metabolism. The increase in blood Ca2+ following low-temperature acclimation was associated with the increased freezing tolerance. Finally, Mg2+ simulated the effect of Ca2+ on freezing tolerance, but was only 20 % as effective. These results suggest that a Ca2+-dependent mechanism responsible for increasing the freezing tolerance of M. demissus exists, and that the increase in blood Ca2+ is due to a conversion to anaerobic metabolism.
A Calcium-Dependent Mechanism Responsible for Increasing the Freezing Tolerance of the Bivalve Mollusc Modiolus Demissus
Authors: Murphy Dennis J. 
Published: April 2021

ABSTRACT
A time course of the changes in blood Ca2+ and freezing tolerance of Modiolus demissus (Dillwyn) demonstrated that increases in freezing tolerance parallel increases in blood Ca2+. The increases in freezing tolerance occurred rapidly, suggesting that Ca2+ affects freezing tolerance directly by its presence in the blood. The presence of La3+ reduced the freezing tolerance of isolated foot muscle. Thus, Ca2+ appears to increase freezing tolerance directly by binding to cell membranes. The loss of the contractile response of freeze-thawed foot muscle to Ach, KC1 and caffeine and the continued response to CaCl2 suggested that cell membranes are the primary sites of freezing injury. The increase in blood Ca2+ following low-temperature acclimation accounted for only 40% of the total change in freezing tolerance. Therefore, other mechanisms responsible for increasing the freezing tolerance of M. demissus following low temperature acclimation also exist.
The Ionic and Water Relations of Embryos of Lymnaea Stagnalis, A Freshwater Pulmonate Mollusc
Authors: Taylor H. H. 
Published: April 2021

ABSTRACT
From cleavage to hatching Lymnaea stagnalis (L.) embryos exhibit net uptakes of radioactive sodium, potassium and calcium greater than the amounts of these ions initially present in the capsular fluid, implying the early development of mechanisms for ion uptake from the dilute external water. The rates of net uptake increase very rapidly during trochophore to veliger stages when the main volume increase and shell formation takes place.
22Na influx increases dramatically at first cleavage from 0·03 to 0·04 pmol min−1 in the hour before cleavage to 0·23 pmol min−1. A further increase occurs in early cleavage and for decapsulated morula to gastrula stages the influx is estimated to be 2·75 pmol min−1. 22Na efflux rates are also high in decapsulated morulae, blastulae and gastrulae (minimal estimates 1·40–3·35 pmol min−1) indicating a rapid exchange of sodium between the embryos and the medium. In sodium-free medium the 22Na efflux from decapsulated blastulae is 0–5 pmol min−1, suggesting that exchange diffusion is a large component of the fluxes. The characteristics of 22Na efflux indicate that sodium does not exchange with the medium as a single compartment.
Expansion of the’recurrent’ cleavage cavity of early stages is accompanied by a rise in exchangeable sodium content from 5 pmol in embryos without cavities to 11-19 pmol in embryos with normally expanded cavities. Experimental expansions of the blastocoel of morula-blastula stages produced by cyanide are also accompanied by great increases in embryo exchangeable sodium content.
A general model is proposed for the movements of sodium and water in the embryos and this provides a mechanism for hyperosmotic regulation by the embryos.
Innervation of the Ventral Diaphragm of the Locust (Locusta Migratoria)
Authors: Peters M. 
Published: April 2021

ABSTRACT
Innervation and some electrical properties of the locust ventral diaphragm were investigated with electrophysiological and histological methods. Muscle fibres are coupled electrically. Electrical stimulation evokes a graded active membrane response. Each segment is innervated by four motor neurones as follows. Two motor neurones are situated in each abdominal ganglion. Branches of their axons supply the ventral diaphragm in the respective and the next posterior segment. This pattern of innervation was confirmed by axonal Co and Ni staining of the motor nerve endings. Neuromuscular junctions are excitatory. EPSPs show summation but no facilitation. Spontaneous electrical activity of the diaphragm is to a certain degree coupled to activity of the main inspiratory muscles.
The Effect of Temperature on Certain Simple Haemolytic Systems
Authors: Ponder Eric , Yeager J. Franklin 
Published: April 2021

ABSTRACT
This paper is primarily concerned with an attempt to evaluate the temperature coefficients for the velocity of haemolysis in two simple haemolytic systems, the lysin being saponin in the first and sodium taurocholate in the second. There is nothing in the literature to suggest that the problem is one of any complexity, for Arrhenius (1915) and his collaborators, by whom most of the existing investigations have been carried out, find that the effect of temperature is adequately described by the well-known Arrhenius equation, the values of μ, ranging from 26,000 when acetic, butyric, or proprionic acids are used as lysins to 38,000 when the lysin is sodium oleate. Their methods, however, are very unsatisfactory, for either the concentration of the lysin or the “time of action” (t.e. time required for the production of a particular degree of haemolysis) is fixed arbitrarily; further, the observations are made over a short temperature range, and usually between 20° and 40°. Such experiments are too restricted to show the complete effects of temperature on the haemolytic systems, and, as will be shown below, lead to quite erroneous results1.