bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Study of the Muscular Anatomy and Swimming Behaviour of the Sea Anemone, Stomphia coccinea
Authors: Sund Paul N. 
Published: April 2021

ABSTRACT
The sea anemone Stomphia coccinea, when touched by certain starfishes, frees itself from the substratum, and by a series of waving motions propels itself through the water. This locomotion has been studied by means of direct observation and by analysis of time-lapse, and normal-speed motion-picture films.
Ecological observations and stimulation tests made in the natural environment of the anemone are described and discussed.
The musculature of the anemone is described, and the function of the various muscles is discussed with regard to their participation in swimming. The muscles that play the most important part in the animal’s movement through the water are the parieto-basilar and the circular muscle-sheet. The other muscles are involved in the overall reaction, but act only as aids in maintenance of the form of the anemone during actual swimming.
Experiments involving the ability of several species of starfish to elicit swimming are described. It has been established that, of those asteroids tested, only Dermasterias imbricata and Hippasteria spinosa are consistently effective in causing Stomphia to swim.
The possibility that swimming serves as a means of escape from starfish predators is considered. Observations and simple experiments indicate that predation may not be a factor in this relationship between starfishes and the anemone.
Observations of the anemones in their natural environment suggested that swimming might be a means to remove debris settling on the oral disk and eventually burying the animal. Experimentally, this could not be substantiated; silt is removed by the cilia of the oral end of the anemone.
That the starfish release some chemical which serves as a stimulant to the anemone is considered; but experiments indicate that if such a substance is present it probably is not water-soluble.
It was discovered that swimming could be brought about by electrical stimulation. The response is facilitated and can be controlled, to a certain degree, by giving stimuli of proper intensity and frequency for varying periods of time (e.g. 6 volts at 1-sec intervals over a period of 2 to 8 sec).
Possible uses for the swimming reaction in nature are considered, but this question still remains open to further speculation and experimentation.
Unmasking of Sudanophil Lipid in the Testis of the House-cricket, Acheta domesticus
Authors: Clayton Blanche-P. 
Published: April 2021

ABSTRACT
1. When the testis of Acheta domesticus is fixed in Flemming’s fluid and embedded in gelatine, Sudan black reveals scarcely any lipid in the externum of the acroblast.
2. It can be shown that the externum of the acroblast contains much lipid in a masked (bound) form.
3. Experiments were performed to find what substances were effective, after Flemming fixation, in unmasking the lipid of the externum and thus making it colourable by Sudan black.
4. The following substances were found to act as unmasking agents: ethanol, dioxane, phenol, resorcinol, hydroquinone, pyrogallol, tannic acid.
5. Under the conditions of the experiment, the most effective unmasking agents were 90% ethanol and 5% hydroquinone.
Histochemical and Morphological Studies of Lipids in the Oogenesis of Pheretima posthuma
Authors: Nath Vishwa , Gupta Brij L. , Manocha S. L. 
Published: April 2021

ABSTRACT
A study of the oocytes of the earthworm, Pheretima posthuma, examined fresh under the phase-contrast and interference microscopes as well as by histochemical techniques, has revealed that there are two types of lipid bodies in the cytoplasm. The lipid bodies of the first type (L1) are smaller, appear as homogeneous, dark granules under the phase-contrast microscope, and have a protein-phospholipid core surrounded by a thick sheath of phospholipids only. The lipid bodies of the second category (L2), which arise as a result of growth and chemical change in L1 bodies, have a pure phospholipid core surrounded by a thick triglyceride sheath. They give a ringed appearance under the phase-contrast microscope. The study under the interference microscope shows that this ringed appearance is an optical artifact. The lipid spheres present in the follicular epithelium contain phospholipids only.
The mitochondria are in the form of minute granules. They remain unchanged throughout oogenesis.
Some vacuoles devoid of any lipids, proteins, or carbohydrates have been observed. They also remain unchanged.
Pure triglyceride spheres, yolk globules, nucleolar extrusions, as well as cholesterols and cholesteryl esters are absent.
The Fine Structure of the Mesenteries of the Sea-Anemone Metridium senile
Authors: Grimstone A. V. , Horne R. W. , Pantin C. F. A. , Robson Elaine A. 
Published: April 2021

ABSTRACT
Sections of the retractor and radial face of mesenteries of Metridium senile (L.) fixed withosmic, osmic-phosphotungstic, or formol-phosphotungstic fixatives were examined by electron microscopy. Each muscle-fibre forms the basal part of a musculo-epithelial cell and is in contact through the cell membrane with a differentiated surface layer of the underlying mesogloea. The muscle-fibres bear crests of cytoplasm containing mitochondria. Each crest is continuous with a cytoplasmic stem which passes through the intercellular space into the epithelial part of the musculo-epithelial cell. The musclefibre consists of densely packed longitudinal filaments 40-80 Å across. The musclefibres present a similar appearance over a great range of extension of the muscle. The filaments show no gross periodic structure like that of striated muscle; nor has any fine regular structure like that described in some other ‘plain’ muscle-fibres yet been detected. There is, however, an irregular beading on the filaments at about 240 Å. Though much smaller, the muscle-fibres of the very slowly contracting radial muscle sheet have the same fine structure as those of the very rapidly contracting retractor muscle. The epithelial part of the cell bears a flagellum arising from a cytoplasmic ‘crater’. The flagellum contains vesicles as well as the typical fibrils. It passes continuously into a complex basal corpuscle which continues into a striated fibrous root. Near the epithelial surface there are conspicuous cross-connexions between adjacent cells. Mucus cells and amoebocytes are described. The mesogloeal lattice of Chapman, which permits free extension of the actinian body, is composed of fibres which seem to be built up of tubular fibrils of about 100 Å diameter. The fibrils show well-developed banding at 260 Å. Where fibrils adhere together their banding is congruent. The criteria of correspondence between the electron micrographs and the living structure are discussed, and the value of information from artifacts and varied methods of fixation is noted.
Studies in Animal Locomotion
Authors: Gray J. 
Published: April 2021

ABSTRACT
The two previous papers in this series have dealt almost exclusively with the movements of fish, such as the eel or the butterfish (Centrono tus gunnellus) whose bodies are long and flexible and which exhibit very well-defined waves of muscular contraction when the fish are travelling through the water. The present paper deals primarily with pelagic fish which differ from the eel in two important respects; they possess well-developed caudal fins and the ratio of body lengthbody width is much smaller.
The Cuticular Stress Detector (Csd2) of the Crayfish I. Physiological Properties
Authors: Klärner Diemut , Barth Friedrich G. 
Published: April 2021

ABSTRACT
The cuticular stress detector (CSD2) is coupled to a patch of compliant cuticle in the ischiopodite. It is excited when the compliant cuticle is deformed directly or by deformation of the surrounding stiffer cuticle. Sinusoidal force (1Hz) directly applied to the compliant cuticle revealed sensory units with thresholds as low as 0·03 mN. The thresholds of most units are higher by up to 40 dB. The stimulus-response curves of the CSD2 units in all preparations have an activity peak between 10 and 30 Hz. In some units (on-units) the spike frequency is high while the force on the cuticle increases. The activity of other units (off-units) declines with rising force. The phase relationship between stimulus and response and the magnitude of the response depend on the exact site of force application. The sensory units of CSD2 can supply the CNS with detailed information about the forces acting on the surrounding cuticle.
The Morphology and Physiological Properties of the Small White Neurones in the Buccal Ganglia of Tritonia Hombergi
Authors: Dorsett D. A. 
Published: April 2021

ABSTRACT
The two small white (W) cells in the buccal ganglia of Tritonia hombergi can initiate and modulate cyclic activity in the pattern generating neurones which drive feeding activity in the buccal mass.
They also make extensive monosynaptic connections with the buccal moto-neurones, generating EPSPs on protractor (P) cells, IPSPs on retractor (R) cells, and EIPSPs on the small radula flattener (F) cells. Two F motoneurones receive a chemically mediated, facilitating EPSP from the W cells.
Inactive W cells receive weak excitatory feedback from the pattern generating network interneurones (FPG) in phase I of the feeding cycle and also from some F cells. Prolonged depolarization of one W cell recruits the other. When both are active they adopt a patterned burst mode with a common inhibitory input in phase I.
Synaptic Basis of Swim Initiation in the Leech: III. Synaptic Effects of Serotonin-Containing Interneurones (Cells 21 and 61) on Swim Cpg Neurones (Cells 18 and 208)
Authors: Nusbaum Michael P. 
Published: April 2021

ABSTRACT
Serotonin-containing cells 21 and 61 strongly excite a swim central pattern generator (CPG) neurone, cell 208, in nearby segmental ganglia in the leech Macrobdella decora. This excitatory effect is apparently independent of activity in the swim-initiating neurone cell 204, which monosynaptically excites cell 208 (Weeks, 1982b). Cell 208 excites cell 21, apparently directly. This is the first identified direct pathway for feedback from the swim central pattern generator to a swim initiator neurone. Focally applied serotonin has no effect on the soma of cell 208, but causes both excitatory and inhibitory responses in cell 208 when applied to different places within the neuropile. Cell 61 polysynaptically excites distant, posterior cells 208. This excitation is mediated at least in part by the activation of nearby cells 208, which polysynaptically excite posterior cells 208. Cell 208 is dye-coupled intraganglionically to a newly identified pair of neurones, designated cells 18. Cell 208 also excites posterior cells 18, apparently directly. This interaction may be the pathway whereby cell 61 polysynaptically excites posterior cells 208. During swimming, cell 18’s membrane potential oscillates in phase with cell 208. Intracellular current injection into cell 18 during swimming perturbs the swim motor pattern. Therefore, cell 18 qualifies as a candidate swim CPG neurone.
Recovery From Anaerobiosis in the Intertidal Worm Sipunculus Nudus II. Gas Exchange And Changes in the Intra- And Extracellular Acid-Base Status
Authors: Pörtner H. O. , Vogeler S. , Grieshaber M. K. 
Published: April 2021

ABSTRACT
Intra- and extracellular acid-base status and changes of coelomic were investigated during recovery following 24 h of anaerobiosis in Sipunculus nudus L. Metabolism, gas exchange and acid-base status were compared in animals collected during March and October.
Anaerobiosis led to an uncompensated metabolic acidosis, the degree of the acidosis depending on the metabolic rate of the animals. During initial recovery in March animals, the acidosis was transiently aggravated in the extracellular, but not in the intracellular, compartment, indicating an efficient regulation of intracellular pH as soon as oxygen was available in the coelomic fluid. The extracellular acidosis was predominantly of non-respiratory origin.
The non-respiratory part of the acidosis is attributed to the repletion of the phospho-L-arginine pool. The proton yield calculated from phosphagen resynthesis was highly correlated in time and in quantity to the observed negative base excess in the extracellular compartment. In October animals, strombine accumulation may have contributed to the acidosis that develops during recovery. The amount of succinate, propionate, and acetate in the coelomic plasma had already decreased when the acidosis developed. This discrepancy supports the conclusion that protons move between the body compartments independent of the distribution of anionic metabolites.
The respiratory part of the acidosis is attributed to the repayment of an oxygen debt. The increase of is higher in October than in March animals, probably because of differences in metabolic rate.
The time course of acid-base disturbances and their compensation is discussed in relation to the time course of metabolic events during recovery and to the priorities of the different processes observed.
The Role of a Zinc-Based, Serum-Borne Sulphide-Binding Component in the Uptake and Transport of Dissolved Sulphide by the Chemoautotrophic Symbiont-Containing Clam Calyptogena Elongata
Authors: Childress J. J. , Fisher C. R. , Favuzzi J. A. , Arp A. J. , Oros D. R. 
Published: April 2021

ABSTRACT
Calyptogena elongata is a small (about 7cm maximum length) species of vesicomyid clam which lives at depths of 494–503m, near the sill depth, in the Santa Barbara Channel in mildly reducing muds at low ambient oxygen concentrations. This species has abundant autotrophic sulphur-oxidizing bacteria in bacteriocytes in its gills. The stable carbon isotope composition values of its gills and other tissues range from −36 to −38‰, supporting the suggestion that the primary carbon source for this symbiosis is inorganic carbon fixed by the endosymbionts. This species of clam concentrates sulphide into its blood serum by using a sulphide-binding component and into the gills by using an unknown sulphide-binding activity. In both tissues, total H2S concentrations within the clam can greatly exceed those outside. This apparently enables the clam to concentrate sufficient sulphide from the mildly reducing muds to support the needs of its endosymbionts. Both of these binding activities are reversible in vivo as shown by the rapid declines in blood and gill sulphide levels when the clams are deprived of sulphide and the rapid concentration of sulphide into the blood and gills when it is provided. For example, within minutes of exposure to 65 μmol l−1 H2S, gill and blood total H2S concentrations in individual C. elongata exceed the external concentration; within 2 h they reach maximum concentrations of about 2mmol l−1. When such experiments are carried out under anoxic conditions, the blood and gill total H2S concentrations approach saturation (10–20mmol l−1), indicating that under oxic conditions the oxidation of sulphide by the clam and its endosymbionts holds the binding components below saturation and enables them to protect the animal tissues and endosymbionts from toxic concentrations of sulphide. In contrast to these results for C. elongata, our experiments show that the host of another chemoautotrophic symbiosis, Solemya reidi, does not concentrate sulphide from the medium into either its blood or its gills. Data are presented which indicate that the serum sulphide-binding component is a large molecular mass molecule with Zn2+ at the active site. This study strongly supports the model of vesicomyid functioning in which the blood-borne sulphide-binding component concentrates sulphide from the reducing environment around the clam’s foot and transports this sulphide to the symbionts in the gills. Data are also presented which indicate that the clam oxidizes some sulphide to thiosulphate and transports this to the gills as well. Thus, individual C. elongata, like the previously studied C. magnifica, appear to bridge the reducing and oxidizing zones of their habitats to provide needed substrates to their endosymbionts. Examination of these two species and the anatomy of other vesicomyid species suggest that vesicomyid clams are functionally quite conservative.
An Analysis of Control of the Ventricle of the Mollusc Mercenaria Mercenaria: I. The Ionic Basis of Autorhythmicity
Authors: Devlin C. Leah 
Published: April 2021

ABSTRACT
During spontaneous beating (autorhythmicity) in the bivalve ventricle, the cardiac action potential (AP) was generated by calcium (Ca2+) and sodium (Na+) influx. The initial fast rising phase (the ‘spike’) of the cardiac AP was dependent on extracellular Ca2+ concentration, whereas the slow plateau phase was Na+-dependent.
The initial fast rising phase of the cardiac AP was abolished by treatment with a Ca2+-free saline or inorganic Ca2+ entry blockers, such as lanthanum chloride or cobalt. Conversely, this fast rising phase of the AP was potentiated by treatment with barium ions, the dihydropyridine-sensitive Ca2+ channel agonist Bay K 8644 or, unexpectedly, by the organic Ca2+ entry blocker diltiazem.
The force of systolic beating was directly proportional to the amplitude of the fast rising phase of the cardiac AP. The Ca2+-dependent, fast rising phase of the AP was modulated by the level of extracellular Na+. Both the amplitude of the fast rising phase of the AP and coupled systolic force were increased by progressive reduction of extracellular Na+ concentration.
The slow plateau phase was abolished by treatment with a Na+-free saline and potentiated by the Na+ ionophore monensin. The size of the Na+-dependent plateau was modulated by the level of extracellular Ca2+. When extracellular Ca2+ was removed from the bathing saline, both the amplitude and duration of the plateau phase were increased. Conversely, restoring extracellular Ca2+ to physiological levels decreased the size of the Na+-dependent plateau.
Autorhythmicity was dependent on the level of extracellular potassium. In the absence of K+, neither a Ca2+-dependent fast rising phase nor a Na+-dependent plateau phase was recorded.
Animal Flight Mechanics in Physically Variable Gas Mixtures
Authors: Dudley Robert , Chai Peng 
Published: April 2021

ABSTRACT
Empirical studies of animal flight performance have generally been implemented within the contemporary atmosphere. Experimental alteration of the physical composition of gas mixtures, however, permits construction of novel flight media and the non-invasive manipulation of flight biomechanics. For example, replacement of atmospheric nitrogen with various noble gases results in a tenfold variation in air density at a constant oxygen concentration. Such variation in air density correspondingly elicits extraordinary biomechanical effort from flying animals; hummingbirds and euglossine orchid bees hovering in such low-density but normoxic mixtures have demonstrated exceptionally high values for the mechanical power output of aerobic flight muscle. As with mechanical power, lift coefficients during hovering increase at low air densities in spite of a concomitant decline in the Reynolds number of the wings. The physical effects of variable gas density may also be manifest in morphological and physiological adaptations of animals to flight across altitudinal gradients. Global variation in atmospheric composition during the late Paleozoic may also have influenced the initial evolution and subsequent diversification of ancestral pterygotes. For the present-day experimenter, the use of physically variable flight media represents a versatile opportunity to explore the range of kinematic and aerodynamic modulation available to flying animals.
Three Neural Groups in the Femoral Chordotonal Organ of the Cricket Gryllus Bimaculatus: Central Projections and Soma Arrangement and Displacement During Joint Flexion
Authors: Nishino Hiroshi , Sakai Masaki 
Published: April 2021

ABSTRACT
The arrangement of neuronal somata and their displacement during joint flexion together with the central projection of the pro- and metathoracic femoral chordotonal organs (FCOs) in the cricket were investigated. The FCO consists of the partially fused ventral and dorsal scoloparia in the proximal femur. The ventrally located neurones (the ventral group) form chain-like rows in which somata became sequentially smaller distally and project their axons ipsilaterally to the dorso-lateral regions, giving off abundant branches and terminating in the region between the dorsal intermediate tract and the ventral intermediate tract in the thoracic hemiganglion. The dorsal scoloparium, composed of small, simply aggregated neurones, projects exclusively to the medioventral association centre (mVAC), which is known to be an auditory neuropile. In addition, another neural cluster (the dorsal group) was found in the proximo-dorsal region of the ventral scoloparium. This was composed of simply aggregated neurones with axons giving off sparse branches dorso-laterally and terminating in the peripheral region inside the mVAC. The somata of these three groups were displaced distally by flexion of the femoro-tibial joint: the ventral group showed the greatest displacement, with the degree of movement depending upon soma location, while the dorsal group and dorsal scoloparium neurones were hardly displaced, possibly because of their strong connection with the cuticle. These properties were similar in both the prothoracic FCO and the metathoracic FCO. Taken together, the above points suggest that there is greater functional differentiation of the FCO than was previously thought.
Cyclic Amp Induces A Relaxation Response In The Bullfrog Rana Catesbeiana, But Nitric Oxide Does Not
Authors: Kline L. W. , Zhang M. L. , Pang P. K. T. 
Published: April 2021

ABSTRACT
Cholecystokinin octapeptide (CCK), acetylcholine (ACh) and ceruletide have been shown to produce contraction in bullfrog (Rana catesbeiana) gallbladder strips. Agents capable of relaxing the bullfrog gallbladder are less numerous. Calcitonin gene-related peptide reduced the amount of both CCK- and ACh-induced tension in bullfrog gallbladder strips. The purpose of this study was to determine whether vasoactive intestinal peptide (VIP), nitric oxide (NO) and the second messengers cyclic GMP or cyclic AMP had any effect on gallbladder motility in the bullfrog. In vitro tension studies using L-NG-nitro-arginine methyl ester, Methylene Blue, sodium nitroprusside and N2,2′-O-dibutyryl guanosine 3′,5′-cyclic monophosphate suggested that nitric oxide did not modulate gallbladder motility in the bullfrog gallbladder. Histochemical staining for NADPH diaphorase (nitric oxide synthase) failed to demonstrate nerve fibers containing nitric oxide synthase in the bullfrog gallbladder. In vitro studies demonstrated that VIP had no effect on CCK-induced tension. However, in vitro studies using either 8-bromoadenosine 3′,5′-cyclic monophosphate or forskolin demonstrated that both agents relaxed strips precontracted with CCK. The results of this study suggested that, while neither NO nor VIP had a role in modulating bullfrog gallbladder motility, cyclic AMP was capable of modulating bullfrog gallbladder motility.