bluuebunny/crossref_metadata_2025 huggingface dataset:
Dual antennular chemosensory pathways mediate odor-associative learning and odor discrimination in the Caribbean spiny lobsterPanulirus argus
Authors: Steullet Pascal , Krützfeldt Dana R. , Hamidani Gemma , Flavus Tanya , Ngo Vivian , Derby Charles D.
Published: April 2021

Chemosensory neurons in the antennular flagella of lobsters mediate long-range responses to chemicals. These neurons are part of two parallel chemosensory pathways with different peripheral and central components. Aesthetasc sensilla on the lateral flagella are innervated by chemosensory neurons that project to the olfactory lobes. A diversity of other ‘non-aesthetasc’ sensilla on both lateral and medial flagella are innervated by mechano- and chemosensory neurons, and most of these non-aesthetasc neurons project to the lateral antennular neuropils. We investigated the roles of these two pathways in odor-associative learning and odor discrimination by selectively removing either aesthetasc or non-aesthetasc sensilla from the spiny lobster Panulirus argus. Lobsters lacking both aesthetasc and non-aesthetasc antennular sensilla show very reduced or no odor-mediated searching behavior. We associatively conditioned lobsters using two paradigms: aversive conditioning with generalization testing (which reveals the similarity in the lobsters’ perception of odorants) and discrimination conditioning (which reveals the lobsters’ ability to discriminate odorants). Sham-control intact lobsters performed these tasks well, as did lobsters lacking either aesthetascs or non-aesthetasc setae. There was a strong but statistically non-significant trend that lobsters lacking either aesthetascs or non-aesthetasc setae generalized more between complex odor mixtures than did intact lobsters. After aversive conditioning with generalization testing, aesthetasc-ablated lobsters had more difficulty discriminating among the most closely related complex mixtures than did intact or non-aesthetasc-ablated lobsters. However, after discrimination conditioning, aesthetasc-ablated lobsters were as proficient as intact animals in discriminating highly similar mixtures. These results indicate overlap and redundancy in the function of these two chemosensory pathways in odor-associative learning and odor discrimination, but these pathways also complement each other to enable better discrimination. This study presents the first evidence for a role of non-aesthetasc chemosensory neurons in complex odor-mediated behaviors such as learning and discrimination.
Learning speed and contextual isolation in bumblebees
Authors: Fauria Karine , Dale Kyran , Colborn Matthew , Collett Thomas S.
Published: April 2021

Bumblebees will learn to approach one of a pair of patterns (a 45°grating) and to avoid the other (a 135° grating) to reach a feeder, and to do the opposite to reach their nest (approach a 135° grating and avoid a 45° grating). These two potentially competing visuo-motor associations are insulated from each other because they are set in different contexts. We investigated what training conditions allow the two sets of associations to be acquired without mutual interference.

If the discrimination at the feeder has already been learnt, then the discrimination at the nest can be readily acquired without disrupting the bees' performance at the feeder. But, if the two are learnt simultaneously,there is mutual interference. Prior experience of the two contexts before the discriminations are learnt does not prevent interference. We conclude that visual patterns and contextual cues must already be associated with each other for a visuo-motor association to be isolated from the interfering effects of a competing association that is acquired in a separate context. This pattern of results was mimicked in a simple neural network with Hebbian synapses, in which local and contextual cues were bound together into a configural unit.
Discontinuous gas-exchange in centipedes and its convergent evolution in tracheated arthropods
Authors: Klok C. Jaco , Mercer Richard D. , Chown Steven L.
Published: April 2021

We have examined the gas-exchange characteristics of five southern African centipede species from three orders. Two scolopendromorph species exhibit discontinuous gas-exchange cycles (DGCs) identical to those recorded for several insect and chelicerate species. Another scolopendromorph and a lithobiomorph species exhibit weak periodic patterns, and a scutigermorph species shows continuous gas exchange. A crucial component for DGCs in tracheated arthropods is the presence of occludible spiracles. However, on the basis of studies of temperate centipedes, most recent invertebrate biology texts hold the view that centipedes, as a group, cannot close their spiracles. Using flow-through normoxic and normoxic—anoxic—normoxic respirometry and electron microscopy, we conclusively demonstrate that at least one of the scolopendromorph species, Cormocephalus morsitansL., can close its spiracles fully, thus accounting for its DGCs. Homologies in spiracular structure and DGCs suggest that several other tracheated arthropod taxa probably have this ability too and that DGCs have evolved convergently at least four times in the Arthropoda. Spiracular closure and discontinuous gas-exchange cycles are probably more widespread in arthropods than has previously been suspected.
Relationship between individual variation in morphological characters and swimming costs in brook charr (Salvelinus fontinalis) and yellow perch (Perca flavescens)
Authors: Boily Patrice , Magnan Pierre
Published: April 2021

The objective of this study was to examine if individual variation in morphological characters is related to swimming costs in wild and domestic brook charr, and in wild yellow perch. Our results indicate that absolute swimming cost was higher in wild and domestic brook charr individuals having a stout body shape, and these individuals are therefore less efficient swimmers. These results are consistent with field observations that described relationships between individual variation in morphology and habitat use in salmonids. Further analyses indicated that standard metabolic rates were higher in individuals having a stout body shape, and that net swimming cost was not related to body shape. Accordingly, the higher swimming cost of stout individuals is probably an indirect consequence of an increase in standard metabolic rate. In wild yellow perch, absolute and net swimming costs were higher in individuals having a stout body shape and a low aspect caudal fin,and standard metabolic rate was not related to body shape. Therefore, in contrast to brook charr, individual variation in the swimming cost of yellow perch appears to be related to morphological characters that affect drag and thrust forces, which is consistent with previously published inter-specific observations.
Comparative neuroethology of feeding control in molluscs
Authors: Elliott C. J. H. , Susswein A. J.
Published: April 2021

Over the last 30 years, many laboratories have examined, in parallel, the feeding behaviour of gastropod molluscs and the properties of the nervous system that give rise to this behaviour. Equal attention to both behavioural and neurobiological issues has provided deep insight into the functioning of the nervous system in generating and controlling behaviour. The conclusions derived from studies on gastropod feeding are generally consistent with those from other systems, but often provide more detailed information on the behavioural function of a particular property of the nervous system. A review of the literature on gastropod feeding illustrates a number of important messages. (i) Many of the herbivorous gastropods display similarities in behaviour that are reflected in corresponding similarities in neural anatomy,pharmacology and physiology. By contrast, the same aspects of the behaviour of different carnivorous species are quite variable, possibly because of their specialised prey-capture techniques. Nonetheless, some aspects of the neural control of feeding are preserved. (ii) Feeding in all species is flexible,with the behaviour and the physiology adapting to changes in the current environment and internal state and as a result of past experience. Flexibility arises via processes that may take place at many neural sites, and much of the modulation underlying behavioural flexibility is understood at a systems and at a cellular level. (iii) Neurones seem to have specific functions that are consistent with their endogenous properties and their synaptic connections, suggesting that individual neurones code specific pieces of information (i.e. they are `grandmother cells'). However, the properties of a neurone can be extremely complex and can be understood only in the context of the complete neural circuit and the behaviour that it controls. In systems that are orders of magnitude more complex, it would be impossible to understand the functional properties of an individual neurone, even if it also coded specific information. (iv) Systems such as gastropod feeding may provide a model for understanding the functional properties of more complex systems.
A model of scale effects in mammalian quadrupedal running
Authors: Herr Hugh M. , Huang Gregory T. , McMahon Thomas A.
Published: April 2021

Although the effects of body size on mammalian locomotion are well documented, the underlying mechanisms are not fully understood. Here, we present a computational model of the mechanics, control and energetics that unifies some well-known scale effects in running quadrupeds. The model consists of dynamic, physics-based simulations of six running mammals ranging in size from a chipmunk to a horse (0.115-676 kg). The `virtual animals' are made up of rigid segments (head, trunk and four legs) linked by joints and are similar in morphology to particular species. In the model, each stance limb acts as a spring operating within a narrow range of stiffness, forward motion is powered and controlled by active hip and shoulder torques, and metabolic cost is predicted from the time course of supporting body weight. Model parameters that are important for stability (joint stiffnesses,limb-retraction times and target positions and velocities of the limbs) are selected such that (i) running kinematics (aerial height, forward speed and body pitch) is smooth and periodic and (ii) overall leg stiffness is in agreement with published data. Both trotting and galloping gaits are modeled,and comparisons across size are made at speeds that are physiologically similar among species. Model predictions are in agreement with data on vertical stiffness, limb angles, metabolic cost of transport, stride frequency, peak force and duty factor. This work supports the idea that a single, integrative model can predict important features of running across size by employing simple strategies to control overall leg stiffness. More broadly, the model provides a quantitative framework for testing hypotheses that relate limb control, stability and metabolic cost.
Effect of muscle temperature on rate of oxygen uptake during exercise in humans at different contraction frequencies
Authors: Ferguson Richard A. , Ball Derek , Sargeant Anthony J.
Published: April 2021

The effect of elevated human muscle temperature on energy turnover was investigated during cycling exercise (at 85 % of V̇O2max) at a contraction frequency of 60 revs min-1. Muscle temperature was passively elevated prior to exercise by immersion of the legs in a hot water bath (42 °C). During exercise at this low pedalling rate, total energy turnover was higher (P<0.05) when muscle temperature was elevated compared with normal temperature (70.4±3.7 versus 66.9±2.4 kJ min-1, respectively). Estimated net mechanical efficiency was found to be lower when muscle temperature was elevated. A second experiment was conducted in which the effect of elevated human muscle temperature on energy turnover was investigated during cycling exercise (at 85 % of V̇O2max) at a contraction frequency of 120 revs min-1. Under the conditions of a high pedalling frequency, an elevated muscle temperature resulted in a lower energy turnover (P<0.05) compared with the normal muscle temperature (64.9±3.7 versus 69.0±4.7 kJ min-1, respectively). The estimated net mechanical efficiency was therefore higher when muscle temperature was elevated. We propose that, in these experiments, prior heating results in an inappropriately fast rate of cross-bridge cycling when exercising at 60 revs min-1, leading to an increased energy turnover and decreased efficiency. However, at the faster pedalling rate, the effect of heating the muscle shifts the efficiency/velocity relationship to the right so that cross-bridge detachment is more appropriately matched to the contraction velocity and, hence, energy turnover is reduced.
Specialized olfactory receptor neurons mediating intra- and interspecific chemical communication in leafminer moths Eriocrania spp.(Lepidoptera: Eriocraniidae)
Authors: Larsson Mattias C. , Hallberg Eric , Kozlov Mikhail V. , Francke Wittko , Hansson Bill S. , Löfstedt Christer
Published: April 2021

We performed a physiological and morphological characterization of sensilla auricillica in male Eriocrania semipurpurella moths. Each auricillic sensillum contained three olfactory receptor neurons. Responding neurons (87 of 139) could be grouped into five physiological types. Type 1 responded to(R,Z)-6-nonen-2-ol and type 2 to its enantiomer(S,Z)-6-nonen-2-ol, both of which are pheromone components of E. semipurpurella. Type 3 responded to both (R)-heptan-2-ol and(R,Z)-4-hepten-2-ol, which are pheromone components of the sympatric species E. cicatricella. Types 4 and 5 responded to the ketones(Z)-6-nonen-2-one and/or nonan-2-one, which are found in the pheromone glands of female E. semipurpurella.

Field-trapping showed that type 3 receptor neurons mediate strongly antagonistic effects of (R)-heptan-2-ol and(R,Z)-4-hepten-2-ol on E. semipurpurella, while nonan-2-one should possibly be included as a synergist in the sex pheromone blend of this species. The attraction of E. cicatricella and E. sparrmannella to compounds mixed with the pheromone blend of E. semipurpurella shows that the pheromone components of E. semipurpurella have little or no antagonistic effects on these species.

The morphology and physiology of eriocraniid pheromone sensilla are very similar to those found in the order Trichoptera (caddisflies), suggesting a homology between pheromone detection systems in the two sister orders Lepidoptera and Trichoptera.
Modulation of ecdysis in the mothManduca sexta
Authors: Fuse Megumi , Truman James W.
Published: April 2021

The sequential behaviours shown by insects at ecdysis are due to the sequential release of various hormones, but the transition from one phase to the next can be fine-tuned by inhibitory influences. The ecdysis sequence in the moth Manduca sexta was initiated by injecting sensitive animals with the neuropeptide ecdysis-triggering hormone (ETH). Exposure to ETH stimulates the release of eclosion hormone (EH) which, in turn, activates a set of neurons containing crustacean cardioactive peptide (CCAP) by elevating their levels of intracellular cyclic GMP. We characterized a set of non-CCAP containing neurons that also appear to be EH targets because of their response to cyclic GMP at ecdysis. The neurons did not display leucokinin-,diuretic-hormone- or FMRFamide-like immunoreactivity. They are probably the bursicon-containing cells described previously. After release of EH, there is a transient inhibition of the abdominal centers responsible for ecdysis. Transection experiments suggested that this suppression is viadescending inhibitory units from the suboesophageal and thoracic ganglia. The duration of this inhibition appears to depend on the levels of cyclic GMP and can be extended by pharmacologically suppressing cyclic GMP breakdown. We further found that brief exposure to CO2 caused premature ecdysis. Since the CO2 treatment was effective only after EH release, it probably acts by suppressing descending inhibition. Studies on adult eclosion suggest that CO2, given at the appropriate time, can uncouple the basic larval motor program from modulatory influences provided by the adult pterothoracic ganglion. CO2 therefore appears to be a novel and non-invasive tool for studies of ecdysis behavior in insects.
Distribution and effects of PACAP, VIP, nitric oxide and GABA in the gut of the African clawed frogXenopus laevis
Authors: Olsson Catharina
Published: April 2021

The distribution and possible effects on gastrointestinal motility of pituitary adenylate cyclase-activating polypeptide (PACAP), vasoactive intestinal polypeptide (VIP), nitric oxide and γ-amino-butyric acid(GABA) were investigated in the African clawed frog (Xenopus laevis)using immunohistochemistry and in vitro strip preparations. PACAP-and VIP-immunoreactive nerve fibres were common in the myenteric plexus as well as in the longitudinal and circular muscle layers all along the gastrointestinal tract. Double labelling demonstrated a close correlation between PACAP and VIP immunoreactivities, indicating that the two neurotransmitters are colocalised within the enteric nervous system. Occasionally, PACAP- and VIP-positive nerve cell bodies were seen in the myenteric or submucous plexa. In addition, VIP immunoreactivity coexisted with helospectin immunoreactivity. Nitric oxide synthase (NOS)-immunoreactive nerve cells were found in the myenteric plexus at an average density for the whole gastrointestinal tract of 4584±540 cells cm-2. The NOS-immunoreactive nerve cells were usually multipolar with an average size of 11.3±3.7 × 23.2±6.6 μm. Some NOS-immunoreactive nerve fibres were VIP-immunoreactive but not all VIP-positive fibres showed NOS immunoreactivity. GABA immunoreactivity was found in nerve fibres and nerve cells in the myenteric plexus of all regions of the gut. Few GABA-immunoreactive nerve fibres were VIP-immunoreactive. PACAP 27, VIP,sodium nitroprusside (a nitric oxide donor; NaNP) and GABA caused similar responses on spontaneously contracting circular preparations of the cardiac stomach of X. laevis. The mean force developed was decreased, mainly by a reduction in resting tension, while the amplitude of contractions was not necessarily affected. The NOS inhibitor NG-nitro-L-arginine methyl ester (L-NAME) increased the mean force developed, indicating a nitrergic tone in the preparations. In contrast, PACAP 27, VIP, NaNP, GABA and L-NAME had no significant effect on longitudinal strip preparations from the duodenum. These results indicate that PACAP, VIP, nitric oxide and GABA, which are known to be important inhibitory neurotransmitters in other vertebrates, are widely spread in the enteric nervous system of Xenopus laevis and may be involved in the inhibitory control of gastric motility. Although no effect of PACAP,VIP, nitric oxide or GABA on the longitudinal strips of the duodenum was seen in this study, this does not rule out the possibility that they might play an important role in controlling intestinal motility as well.
The effects of continuousversuspartial reinforcement schedules on associative learning, memory and extinction inLymnaea stagnalis
Authors: Sangha Susan , McComb Chloe , Scheibenstock Andi , Johannes Christine , Lukowiak Ken
Published: April 2021

A continuous schedule of reinforcement (CR) in an operant conditioning procedure results in the acquisition of associative learning and the formation of long-term memory. A 50 % partial reinforcement (PR) schedule does not result in learning. The sequence of PR—CR training has different and significant effects on memory retention and resistance to extinction. A CR/PR schedule results in a longer-lasting memory than a PR/CR schedule. Moreover,the memory produced by the CR/PR schedule is resistant to extinction training. In contrast, extinction occurs following the PR/CR schedule.
The Distribution of Vitamin C in Nyctotherus Cordiformis Ehrenberg, Opisthioglyphe Ranae Frölich, and Toxocara Canis Werner
Authors: Smyth J. D. , Bingley W. J. , Hill G. R.
Published: April 2021

The localization of vitamin C in Nyctotherus cordiformis, Toxocara canis and Opisthioglyphe ranae was investigated by means of the silver nitrateacetic acid technique. In Nyctotherus, the vitamin C is distributed uniformly throughout the cytoplasm in the form of globules of varying sizes. No vitamin is present in the ectoplasmic layer or in the region of the nuclei. In the same preparations specimens of Opalina show no trace of any vitamin C present. In Toxocara, the vitamin is localized in relatively large quantities in all the cells of the intestine. In these cells it is aggregated mainly in the region between the nucleus and the free cell border. A series of fine granules of the vitamin also line the lower cell walls. Only a few scattered granules are present in the remaining tissues. In Opisthioglyphe, the vitamin is concentrated on the walls of the excretory system which in this trematode has the form of two longitudinal canals joining in the posterior region to form a single median canal. A line, of disk-like elements of the vitamin is also present immediately below the epidermis. In the remaining tissues only very small scattered grains are found. It is believed that in the case of Toxocara, the presence of the vitamin in the gut cells may indicate that the parasite is capable of absorption of vitamin C from the food of the host. It is suggested that in heavy parasitic infections the parasites may play some part in the disturbance of the vitamin C balance of the host.
On the Behaviour of Wireworms of the Genus Agriotes Esch. (Coleoptera, Elateridae) in Relation to Temperature
Authors: Falconer D. S.
Published: April 2021

I

1. The highest temperature which wireworms could withstand for an indefinite period without becoming paralysed was found to-be between-35 and 36 ° C. The resistance to high temperature was not influenced by the previous temperature. 2. The resistance of wireworms to low temperature was found to be greatly influenced by the rate at which the temperature was reduced. When the temperature fell rapidly, all were killed by 6 days’ exposure to – 3°C., and by 4 hr. exposure to –7°C. The resistance to low temperature was not increased by a previous exposure of 24 hr. at o°C., when the subsequent fall of temperature was rapid. When the temperature was lowered in small stages, however, the resistance was considerably increased, and a few wireworms survived for at least a day at − 10°C. 3. The published data of soil temperatures suggest that temperatures above 30 ° C. or below about − 1 ° C. are not of regular occurrence in England, and it is concluded that wireworms in England are not normally liable to encounter lethal temperatures..

II

4. The relationship between the wireworms’ speed of crawling and the temperature was found to be nearly linear between 8 and 25°C. 5. Burrowing activity was uniformly greater at higher than at lower temperatures between 6 and 33°C. Temperature influenced the speed but not the continuity of the activity. After adaptation had taken place the burrowing activity was almost nil at 6°C. When subjected to a sudden fall of temperature from 16 to 6 °C., the wire worms’ burrowing activity in the first 2 hr. was significantly greater than it was at the same temperature 16 hr. later. 6. The weight of wheat eaten by wire worms was found to be greatest at 32 ° C., but feeding activity was most continuous at about 18°C. At 7°C. and at 34° C. little feeding took place.

III

7. No vertical movements in response to gravity were exhibited by the wireworms under any conditions of temperature. 8. When given a choice of temperatures in an alternative-chamber apparatus, the wireworms showed a clear preference for 17°C. as against 11·5 and 21°C. or higher temperatures. The temperature preference was not found to be influenced to any great extent by the previous perature. 9. The mechanism by which the wireworms reacted at a temperature boundary was of the nature of a ‘shock reaction’, their direction of movement being reversed.

No evidence of a klinokinetic response to change of temperature was obtained from wireworms burrowing in sand.
On the Movement of Wireworms of the Genus Agriotes Esch. (Coleoptera, Elateridae) on the Surface of the Soil and Their Sensitivity to Light*
Authors: Falconer D. S.
Published: April 2021

During the course of experimental work on the behaviour of wireworms in relation to temperature (Falconer, 1945), stocks of wireworms were kept in sand in glass jars, and it was often noticed after a jar had been left undisturbed for some time that the surface of the sand was pierced by many small holes of the size of a wireworm burrow. This fact suggested that, contrary to general belief, wireworms might sometimes come out on to the surface of the soil and wander about before re-entering, perhaps at a different point. If this were the case, the fact might have considerable importance in connexion with migration and possibly with food finding. Reference to the matter is scanty in the literature. Subklew (1934) stated that though the larvae are well adapted to life in the soil, they are also able to crawl about extensively on the surface : in a later paper, however (Subklew, 1935), he concluded that a wireworm which had come out on to the surface would at once be led below ground again by its thigmotactic response. Guéniat (1937) speaks of collecting abundant wireworm material in early spring without digging, the larvae being found under stones and lumps of earth: these larvae, he says, eat young grass shoots and dandelion leaves. Though it is not explicitly stated, his remarks strongly suggest that wireworms in Switzerland habitually move about on the surface of the soil in early spring. There does not, however, appear to be any evidence of similar behaviour on the part of wireworms in England.
The Mechanism of Locomotion in Gastropod Molluscs: I. Kinematics
Authors: Lissmann H. W.
Published: April 2021

Whereas the broad outline of the mechanical events of locomotion can in most animals be readily visualized, the mechanism of propulsion in gastropods is less easily observed. Since the seventeenth century (Lister, 1694) a great deal of attention has been paid to this problem and a wealth of suggestions has been forthcoming; there is, however, a significant absence of convincing experimental data. To some extent the problem is confusing on account of the diversity of locomotory mechanisms existing within the group (Vlès, 1907; Parker, 1911; Olmsted, 1917; Weber, 1925). Nevertheless, there can be no room for doubt that one characteristic type of movement depends upon the propagation of waves of muscular activity over the surface of the animal’s foot. So far as is known, no adequate account has yet been, given of the method whereby this type of activity propels the animal over the surface of the ground. The present paper deals with these problems in respect to three representative genera, Helix, Haliotis and Pomatias.
Internal Oxygen Environment of the Brains of Post-Mature Rabbit Embryos
Authors: Barcroft Joseph , Young I. Maureen
Published: April 2021

In 1935 Barcroft, Flexner, Herkel, McCarthy & McClurkin, working on rabbits, showed that the oxygen saturation of the blood leaving the uterus dropped from an average value of about 70 % at the 18th day of gestation to about 30 % saturation on the 30th day. During the period in question the foetuses are in active growth, whilst growth of the placenta is only trifling. On the 18th day the combined weight of the foetuses is approximately the same as that of the foetal portions of the placentas to which they are attached; on the 30th day the foetuses weigh about fifteen times as much as the placentas.
The Biology and Behaviour of Ptinus Tectus Boie. (Coleoptera, Ptinidae), A Pest of Stored Products
Authors: Gunn D. L. , Knight R. H.
Published: April 2021

The highest temperature at which Ptinus tectus should be reared is near 24 ·7 ° C. Humidities higher than 70 % cannot conveniently be used because of the growth of moulds. Lower humidities prolong development. The best food tried was 95 % whole ground wheat with 5 % dried brewers ‘yeast. The smallest quantity of this food which permits completion of development is about 3 mg. per animal. This produces miniature adults, one-third of the normal weight, in almost normal time. About 30 mg. is required to produce full-sized adults. These statements apply to individuals reared in isolation. When a group of several larvae are reared in one container, development is prolonged by up to 40 % (which does not occur at all with isolated animals even if food is so short as to cause severe stunting), while some diminution of size (20 %) is found. This is called the ‘group effect’. With groups of 8 larvae, as much as 5 g. of food per larva is required before the group effect disappears, too times as much as is needed for full and speedy development by an isolated larva. With quantities of food per larva which are optimal or supra-optimal for isolated larvae, the group effect reaches its highest expression with 8 larvae in the group. It diminishes at smaller group sizes. Mass cultures show the effect to about the same extent as groups of 8. Animals reared in groups show a wider range of variation in size than those reared in isolation, but their duration of development is not more variable. No adequate explanation has yet been found for the group effect and no method has yet been found of producing from mass cultures animals as uniform in size as those reared singly. Adults come into full and fertile lay about a week after emergence from the cocoon. The rate of laying is markedly diminished if the animals are not given fresh food and water to drink daily. A female can live for a year and lay nearly a thousand eggs. In starting mass cultures, it is best to allow a large number of animals in good condition to lay for a day or so. No better result will be obtained by leaving the animals longer.
On the Penetration of Insecticides Through the Insect Cuticle
Authors: Webb J. E. , Green R. A.
Published: April 2021

Using Melophagus ovinus, the sheep ked, as test insect, it was found that certain organic solvents of diphenylamine, such as the cresols, benzyl alcohol and 4-methyl-cyclohexanol, greatly increase the rate of action of this insecticide. Others, strcn as carbitol and methyl benzoate, gave little or no improvement in the time of kill. The degree to which a solvent induces rapid penetration of an insecticide is referred to as its ‘carrier efficiency’. The influence of the physical properties of the solvents on carrier efficiency was investigated. It was found that a high carrier efficiency could be correlated with a high rate of penetration through beeswax, a high partition coefficient of the solvent between beeswax and water and a high solubility of insecticide in a solution of the solvent in water. The volatility of the solvent and the solubility of insecticide in solvent were also contributory factors. Mixtures of two solvents, each showing no carrier efficiency but together possessing all the essential physical properties, were tested and showed a carrier efficiency considerably higher than that of either constituent. This is taken as supporting evidence that carrier efficiency depends on certain physical properties of a solvent. Using a range of solvents shown to exhibit various degrees of carrier efficiency with diphenylamine, comparable results were obtained with dixanthogen, ω-nitrostyrene dibromide and rotenone and showed that the synergy could be extended to other insecticides. It is suggested that certain solvents increase the rate of penetration of contact insecticides through the insect cuticle : By transporting the insecticide through the lipoid elements of the epicuticle to the interface between this layer and the water permeating the exocuticle. By concentrating the insecticide at the interface between the epicuticle and the exocuticle, as the. solvent passes into the exocuticle, and thus increasing the diffusion gradient of the insecticide across that interface. By increasing the solubility of the insecticide in the water permeating exo-and endo-cuticles and thus, by raising its partition coefficient between solvent in the epicuticle and water in the exocuticle, further increasing its rate of diffusion, not only across this interface, but also through exo- and endo-cuticles to the hypodermis.
Differentiation of Ectoderm Implanted into the Primordium of the Limb Bud in the Amphibian Embryo and its Influence Upon the Limb*
Authors: Brandt Walter
Published: April 2021

It was shown by Brandt (1944) that phocomelias and atrophied limbs can be produced experimentally after deep implantation of embryonic ectoderm into the primordium of the limb bud in the tail-bud stage (Harrison’s stage no. 35) of the amblystoma embryo. The following microscopical analysis of the operated specimens shows some new results which concern the histological changes of the implanted embryonic ectoderm within the tissues of the host embryo and their effect on the limb primordium.
Peripheral Nerve and Regeneration in Crustacea. II
Authors: Needham A. E.
Published: April 2021

In the previous paper of this title (Needham, 1945) denervation of a thoracic limb of the isopod Asellus aquaticus at the time of amputation was shown to result in a marked retardation of regeneration, as compared with the partner limb amputated, without denervation, at the same time: In the present work it was hoped to throw more light on this neurotropic effect by experiments involving denervation at different times relative to amputation. Schotté & Butler (1944) find that the peripheral nerve is necessary for the early stages but not for the later stages of regeneration of amphibian limbs. In one series of the present experiments denervation was performed 5 days after amputation, and in a second series after normal regeneration for one instar, that is, at the first appearance of an externally visible regenerate, an average of 10 days after amputation. Such a regenerate is already partly functional, so that the possibility must be envisaged that denervation might lead to some disuse-atrophy in addition to its possible effect on regenerative growth; in a third series, therefore, the normally growing limb was denervated (without amputation), in order to obtain some measure of the extent of this disuseatrophy. The results of this third series may include an effect of denervation on normal (i.e. non-regenerative) growth also. In a fourth series the limb was denervated 5 days before amputation, the object being to ascertain whether tissue denervated some time previously to amputation and undergoing the consequent atrophic changes is capable of developing a regeneration blastema at the surface of amputation, and of regenerating at the normal rate as soon as the regenerating nerve reaches that surface (cf. Needham, 1945, p. 146).
The Growth of Brown Trout (Salmo Trutta Linn.)
Authors: Brown Margaret E.
Published: April 2021

Temperature is a limiting factor in the distribution of many animals. The ova of brown trout (Salmo trutta) can develop without excessive mortality at water temperatures between 3 and 15o C. (Gray, 1928), while for adult trout, mortality is high above 20 and complete above 25o C. (Gardner & Leetham, 1914; Audigé, 1921 ; Gardner, 1926). It is generally assumed that temperature is the most important physico-chemical factor affecting the growth of fish, especially in temperate zones, where there is an annual variation. Allen (1940) deduced from examination of salmon scales from British rivers that parr do not grow when the water temperature is less than 7°C. Pentelow (1939) and Wingfield (1940) observed the growth of yearling trout in tanks where the temperature varied with that of the external environment and was recorded once a day. They found that there was no growth at temperatures less than 6°C., and it was most rapid between 10 and I5°C. Since other environmental factors varied at the same time, the correlation between growth rate and temperature was necessarily approximate.
Volatile Acid in the Digesta of Ruminants and Other Animals
Authors: Elsden S. R. , Hitchcock M. W. S. , Marshall R. A. , Phillipson A. T.
Published: April 2021

A mixture of volatile organic acids, consisting for the most part of the fatty acids, acetic, propionic and butyric, is a characteristic product offermentation within the alimentary tract. It was shown previously that volatile acids are absorbed directly from the organ in which they are produced (Barcroft, McAnally & Phillipson, 1944), and this fact, together with a consideration of the quantities present in the digesta—a subject with which the present paper is concerned—suggest that they form a valuable part of the calorific material utilized by the animal.
The Reactions Of Isolated Parts Of Spirostomum
Authors: Clark A. M.
Published: April 2021

The determination of the reactions and behaviour of isolated fragments of a protozoan is of value to the study of three problems, namely, the relationship between the nucleus and behaviour, the detection of any area in the organism specialized for the reception of external stimuli, and in the case of a cihate, the role played in normal swimming by the cilia of different regions of the body. Recently, an account has been given of the reactions of fragments of Amoeba proteus (Clark, 1944). The present paper is an extension of the work to include a ciliated form.
Local Factors and Regeneration in Crustacea
Authors: Needham A. E.
Published: April 2021

The role of normal innervation in the regeneration of crustacean appendages has been illustrated in previous papers (Needham, 1945, 1946); it may, perhaps, be termed the ‘central’ factor in regeneration. In the present paper ‘local’ factors, such as properties of the tissues near the site of amputation, have been studied. The results of earlier work, chiefly on Amphibia, Planaria and Oligochaeta (Korschelt, 1927, pp. 639–40), have suggested that the rate of regeneration varies with (1) the extent of tissue damage at the site of amputation and (2) the amount of tissue removed. These two factors have been studied in the present experiments on the regeneration of the 7th thoracic limb of Asellus aquaticus (L.).
On the Function of Haemoglobin in Chironomus After Oxygen Lack
Authors: Walshe Barbara M.
Published: April 2021

When Chironomus plumosus larvae receive aerated water after a period of anaerobiosis their oxygen consumption increases at once to a value well above the normal. This initial increase lasts for about 10 min. at 17° C., after which the oxygen consumption falls but continues to be slightly above normal for 1 hr. The initial sudden considerable rise in oxygen consumption is due to increased activity of the larvae ; it is absent in larvae made inactive by a low temperature of 1° C. Such larvae, however, maintain an oxygen consumption above the normal value for about 2 hr. The increased oxygen consumption lasting for 1-2 hr. after anaerobiosis represents the repayment of an oxygen debt, but this debt is only 0·5 % of the oxygen which would have been consumed had the anaerobic period been an aerobic one. The small size of the oxygen debt suggests that most of the products of anaerobic metabolism are excreted. The haemoglobin of the larvae does not function during the repayment in fully aerated water of the small oxygen debt. This is shown by experiments with and without carbon monoxide. During the initial short considerable rise in oxygen consumption at 17° C. due to larval activity after anaerobiosis the haemoglobin is functional. This activity occurs while the water is not yet fully aerated, and so the haemoglobin enables the larvae to maintain their activity aerobically in water containing little dissolved oxygen. In nature the undulatory activity of the larvae immediately after anaerobiosis must serve to ventilate the U-shaped tubes in which they live in the mud, and so to fill the tubes with aerated water.
Age-related reductions in the number of serial sarcomeres contribute to shorter fascicle lengths but not elevated passive tension
Authors: Power Geoffrey A. , Crooks Sean , Fletcher Jared R. , Macintosh Brian R. , Herzog Walter
Published: April 2021

We investigated age-related changes to fascicle length, sarcomere length and serial sarcomere number (SSN), and how this affects passive force. Following mechanical testing to determine passive force, the medial gastrocnemius muscle of young (n=9) and old (n=8) Fisher 344BN hybrid rats was chemically fixed at the optimal muscle length for force production; individual fascicles were dissected for length measurement, and laser diffraction was used to assess sarcomere length. Old rats had ∼14% shorter fascicle lengths than young rats, which was driven by a ∼10% reduction in SSN, with no difference in sarcomere length (∼4%). Passive force was greater in the old than in the young rats at long muscle lengths. Shorter fascicle lengths and reduced SSN in the old rats could not entirely explain increased passive forces for absolute length changes, owing to a slight reduction in sarcomere length in old rats, resulting in similar sarcomere length at long muscle lengths.
The Regeneration of Legs in Rhodnius Prolixus (Hemiptera)
Authors: Lüscher Martin
Published: April 2021

It is well known that many insects, and especially many Orthoptera, are capable of regenerating autotomized and amputated legs (Godelmann, 1901 ; Bordage, 1905 ; Megusar, 1910; Friedrich, 1930). Very little is known, however, about those factors governing regeneration, those initiating the excessive growth in regeneration, and those suppressing growth when the regenerated leg has reached a normal size. In order to investigate these factors and their mode of action, it is very convenient to have an insect in which the hormonal control of moulting and metamorphosis is well known. Such an insect is Rhodnius (Wigglesworth, 1936, 1940 a, b), and this insect is also able to regenerate the distal parts of its legs. As regeneration in Rhodnius has not previously been described, it has been necessary to study the normal process of repair in relation to time, temperature and amputation level in order to provide a basis for further work on the factors mentioned above. Normal regeneration will be described in this paper. Strangely enough the temperature and time relations have never been investigated in insect regeneration, although much physiological work has been carried out on the subject.
The Poisoning of Marinogammarus Marinus by Cupric Sulphate and Mercuric Chloride
Authors: Hunter W. Russell
Published: April 2021

The toxicity, under various conditions, of cupric sulphate and mercuric chloride to the marine amphipod, Marinogammarus marinus, has been studied. With optimum conditions copper is virtually non-toxic over the range of concentrations studied (e.g. becoming effective as a poison on decrease in salinity or oxygen tension). The toxic action of mercury is not greatly affected by changed conditions. At very low concentrations, copper has a pronounced effect on animals undergoing mercury poisoning. Subtoxic traces of mercury have no effect on the course of copper poisoning. It is suggested that in M. marinus, mercury acts directly by poisoning of the protoplasm while the effect of copper is indirect, involving the upset of some metabolic process.

The relation of this work to other studies of the action of heavy metals is briefly discussed.
The Action of Colchicine in Arresting Epidermal Mitosis
Authors: Bullough W. S.
Published: April 2021

In the foregoing paper (Bullough, 1949b) a doubt is expressed concerning the value of colchicine for collecting in the metaphase all those mitoses which normally occur during a 12 hr. period. It is probably true to say that most studies of animal mitosis made with the help of colchicine have been planned on two assumptions, namely that, within reasonable limits, the drug arrests every mitosis reaching the metaphase, and, equally important, that it neither increases nor decreases the number of resting cells entering mitosis. Following the pioneer work of Dustin (1934), Lits (1934) and others, these reasonable limits have been defined (see Allen, 1937) as a dose of 0·1 mg. given subcutaneously in water or normal saline and allowed to act for a period of hr. With smaller doses only a partial stoppage of mitosis is achieved; with larger doses the resting cells are prevented from entering the prophase; and with longer periods the number of arrested mitoses does not increase because there is a complete stoppage of all cell division.
The Effect of Calcium On the Axoplasm of Giant Nerve Fibres
Authors: Hodgkin A. L. , Katz B.
Published: April 2021

As was first described by Bear, Schmitt & Young (1937), a jelly-like and apparently solid cylinder of axoplasm is obtained when the contents of a fresh giant nerve fibre of the squid are extruded. There are several observations which indicate that the axoplasm is also normally in a gelatinized state and behaves like a solid.
The Influence of Age and Sex on ‘Reasoning’
Authors: Hanson D. A.
Published: April 2021

Genetically determined, or instinctive, behaviour arises from the selective effects of environment on the life history of a species, and at its first appearance in the life of an individual owes little or nothing to the previous experience of that individual. Most, if not all, organisms are also able to modify their behaviour through ‘personal’ experience. By their ability to learn, animals adapt themselves more intimately to their own particular environment. The new behaviour patterns set up are biologically advantageous to the individual. They arise out of, and are continuous with, the past history of the individual.
On the Reactions to Humidity of Peripatopsis Moseleyi (Wood-Mason)
Authors: Bursell E. , Ewer D. W.
Published: April 2021

Quantitative studies have been made by previous workers on the reactions to humidity of three classes of terrestrial arthropod. The isopods have been studied by Gunn (1937) and Waloff (1941), the sheep tick by Lees (1948), while a number of insects have been examined in this connexion. The Onycophora have so far escaped attention. From a consideration of the usual habitat of these creatures it appeared likely that a marked humidity reaction might exist. The experiments described below give an account of this reaction, its character and mechanism.
Counting Spermatozoa
Authors: Rothschild Lord
Published: April 2021

The number of spermatozoa in a sample of sea-urchin semen (Echinus esculentus) can be accurately estimated by measuring the amount of light scattered and absorbed by a subsample composed of semen diluted with sea water. A ‘Spekker’ photoelectric absorptiometer was used for the measurements, with a cell 1 cm. long. The number N of spermatozoa in a sample of sea-urchin semen was found to be given by the equation where Y′= 0·3010 – log10y′ and y′ = absorptiometer reading, when the original sample was diluted 200 times and the absorptiometer set to 2·000 for the blank. The light-scattering and light-absorbing properties of washed and unwashed suspensions were found to be virtually identical. The number of spermatozoa in a sample of bull semen was found to be given by the equation
The Effect of Posterior Lobe Pituitary Extracts On the Blood Pressure of Ornithorhynchus (Duck-Billed Platypus)
Authors: Feakes M. J. , Hodgkin E. P. , Strahan R. , Waring H.
Published: April 2021

The carotid blood-pressure response to intravenous injection of histamine-free extracts of mammalian posterior pituitary extracts in the platypus (Ornithorhynchus) is described. Pitressin evokes a simple pressor response. Pitocin evokes a simple depressor response. Mixtures of pitressin and pitocin evoke a fall and a subsequent rise. Histamine evokes a depressor response. A preliminary note is made of the simple pressor response to pitressin and depression to pitocin in the deeply-anaesthetized bird and in a lizard. Comparison is made between the responses to posterior pituitary extracts in reptiles, birds, the platypus and eutheria. The possible phylogenetic significance of these observations is discussed.