scholarly journals The Nerve-Net of the Sea-Anemone Metridium Senile: the Mesenteries and the Column

1960 ◽  
Vol s3-101 (56) ◽  
pp. 487-510
Author(s):  
E. J. BATHAM ◽  
C. F. A. PANTIN ◽  
E. A. ROBSON
Keyword(s):  
Methylene Blue ◽  
Reciprocal Inhibition ◽  
Nerve Cells ◽  
Sea Anemone ◽  
Nerve Net ◽  
Metridium Senile ◽  
Physiological Evidence ◽  
Staining Methods

The actinian nerve-net has been examined in the mesenteries and column of Metridium senile (L.) after staining with silver and with methylene blue. Modified staining methods are described. The synaptic nature of the junctions between bipolar nerve-cells, of their expanded terminations over the muscle-field, and of their contacts with the neurites of sense-cells is reviewed. The neurites always run in the space between the epithelium and underlying muscle. They follow the distribution of the main contractile systems, including the passage of circular fibres beneath the mesenteries. The richerinnervation of the retractor surface of a mesentery compared to the radial is correlated with the ability of this hypertrophied muscle to contract rapidly. The distribution of nerve-cells and sense-cells in the mesenteries and column is related to physiological evidence concerning the through-conduction pathways, facilitated and slow contractions, and other aspects of the behaviour of Metridium. It is concluded that although features such as reciprocal inhibition in the column are still unexplained, there is as yet no histological or physiological evidence for double innervation of the musclesin this anemone. The terminations of sensory neurites, on musclefibres or elsewhere, have not yet been seen in any actinian

The Nerve-net of Metridium senile: Artifacts and the Nerve-net

1961 ◽  
Vol s3-102 (58) ◽  
pp. 143-156
Author(s):  
E. J. BATHAM ◽  
C.F. A. PANTIN ◽  
E. A. ROBSON
Keyword(s):  
Nervous System ◽  
Nerve Cells ◽  
Muscle Fibres ◽  
Nerve Net ◽  
Metridium Senile ◽  
Staining Methods ◽  
Epithelial Layers

The present paper follows an account of the structure of the nervous system of Metridium senile(L.). Conflicting statements about the actinian nervous system in the earlier literature made it necessary to assess the results of previous workers critically. Several of their methods have now been repeated and compared with our results after using more specific techniques. The criteria for distinguishing nerve-cells from nonnervous elements in actinians are discussed. Mesogloeal fibres, amoebocytes, nematocyst threads, and muscle-fibres may on occasion be confused with nerve-cells, and deteriorating nerve-cells may also have a misleading appearance. Gross artifacts may be reduced by the use of special staining methods, and on the basis of this work the results of several earlier authors have been re-interpreted. It is concluded that the nervous system in the mesenteries and column of Metridium follows the epithelial layers and does not penetrate the mesogloea.

A Comparison of the Nervous Systems of two Sea-Anemones, Calliactis parasitica and Metridium senile

1961 ◽  
Vol s3-102 (59) ◽  
pp. 319-326
Author(s):  
ELAINE A. ROBSON
Keyword(s):  
Methylene Blue ◽  
Nervous System ◽  
Conduction System ◽  
Nerve Cells ◽  
Bipolar Cells ◽  
Retractor Muscle ◽  
Sea Anemones ◽  
Nerve Net ◽  
Metridium Senile ◽  
Calliactis Parasitica

The properties of the actinian nervous system are known mainly from physiological experiments on Calliactis parasitica (Couch), and from histological work on Metridium senile (L.). The structure of the nerve-net in the mesenteries of Calliactis is now shown to resemble in general that in Metridium. Methylene blue stains a network of bipolar cells over the retractor muscle, together with sense-cells, and unlike Metridium, multipolar nerve-cells. The nerve-net over the radial surface of the mesentery is similarly much sparser. The distribution of nerve-cells and sense-cells in the column also resembles that in Metridium. Experiments on Metridium show that as in Calliactis, the rate of conduction in the mesenteries is greater than in other parts of the anemone. The column, including the sphincter region, conducts more slowly. It is thus shown that the presence of a well developed nerve-net over the retractors is associated with the development of fast tracts in the through-conduction system, and of rapid, facilitated contractions of the retractor muscles, in both species of anemone.

The Behaviour and Neuromuscular System of Gonactinia Prolifera, A Swimming Sea-Anemone

1971 ◽  
Vol 55 (3) ◽  
pp. 611-640
Author(s):  
ELAINE A. ROBSON
Keyword(s):  
Electrical Stimulation ◽  
Mechanical Stimulation ◽  
Motor Units ◽  
Nerve Cells ◽  
Sea Anemone ◽  
Neuromuscular System ◽  
Sea Anemones ◽  
Nerve Net ◽  
Local Contraction ◽  
Electric Shocks

1. In Gonactinia well-developed ectodermal muscle and nerve-net extend over the column and crown and play an important part in the anemone's behaviour. 2. Common sequences of behaviour are described. Feeding is a series of reflex contractions of different muscles by means of which plankton is caught and swallowed. Walking, in the form of brief looping steps, differs markedly in that it continues after interruptions. Anemones also swim with rapid tentacle strokes after contact with certain nudibranch molluscs, strong mechanical disturbance or electrical stimulation. 3. Swimming is attributed to temporary excitation of a diffuse ectodermal pacemaker possibly situated in the upper column. 4. From the results of electrical and mechanical stimulation it is concluded that the endodermal neuromuscular system resembles that of other anemones but that the properties of the ectodermal neuromuscular system require a new explanation. The size and spread of responses to electric shocks vary with intensity, latency is variable and there is a tendency to after-discharge. There is precise radial localization, for example touching a tentacle or the column causes it to bend towards or away from the stimulus. 5. A model to explain these and other features includes multipolar nerve cells closely linked to the nerve-net which would act as intermediate motor units, causing local contraction of the ectodermal muscle. This scheme can be applied to other swimming anemones but there is no evidence that it holds for sea anemones generally.

A Transmesogloeal Conduction System in the Swimming Sea Anemone Stomphia

1980 ◽  
Vol 87 (1) ◽  
pp. 45-52
Author(s):  
I.D. LAWN
Keyword(s):  
Electrical Activity ◽  
Conduction System ◽  
Nerve Cells ◽  
Sea Anemone

1. A conduction system in Stomphia transfers information across the mesogloea from ectodermal receptors to endodermal effectors. 2. In the column, this transmesogloeal system has numerous and widespread connexions. 3. It is suggested that the connexions may be processes from multipolar nerve cells located in the endoderm. 4. Certain aspects of behaviour are controlled by this conduction system which provides yet another pathway to co-ordinate electrical activity.

Endings of the vagus nerve fibers in the mammalian heart

1927 ◽  
Vol 23 (6-7) ◽  
pp. 622-623
Author(s):  
B. I. Lavrent'ev
Keyword(s):  
Methylene Blue ◽  
Vagus Nerve ◽  
Nerve Fibers ◽  
Nerve Cells ◽  
Vagus Nerves ◽  
Mammalian Heart ◽  
Cardiac Ganglia ◽  
Important Study ◽  
Spiral Fibers

In 1893, Prof. V.V. Nikolaev, having cut vagus nerves of a frog, saw under a microscope degeneration of so-called spiral fibers and pericellular apparatuses on nerve cells of intracardiac nodes. Later these observations were thoroughly verified by Prof. D.V. Polumordvinov and fully confirmed by him. I had a chance to look through amazing by technique preparations of the late Prof. Polumordvinov, obtained by methylene blue method, on which decay of pericellular apparatuses in cardiac ganglia of a frog was absolutely clearly visible. D. V-ch, who died untimely in 1919, unfortunately, did not have time to publish in detail his important study; the manuscript and drawings of his work also remained undiscovered.

Observation of virus-like particles in thin sections of the plumose anemone, Metridium senile

2001 ◽  
Vol 81 (5) ◽  
pp. 879-880 ◽  
Author(s):  
William H. Wilson ◽  
David M. Chapman
Keyword(s):  
West Coast ◽  
Sea Anemone ◽  
Dense Core ◽  
Icosahedral Structure ◽  
The West ◽  
Thin Sections ◽  
Virus Like Particles ◽  
Metridium Senile ◽  
Electron Dense Core

Virus-like particles (VLPs) were observed in thin sections of the plumose anemone, Metridium senile, collected from seawater off the west coast of Sweden in 1969. The VLPs were observed in the nucleus of spiroblasts and amoebocytes; they were either pentagonal or hexagonal in section, indicating an icosahedral structure. Virus-like particles were ∼60 nm in diameter, with an electron-dense core 40 nm in width; they had no apparent tail. This is the first substantial report of viruses observed in sea anemone cells.

Control of mouth opening and pharynx protrusion during feeding in the sea anemone Calliactis parasitica

1975 ◽  
Vol 63 (3) ◽  
pp. 615-626
Author(s):  
I. D. McFarlane
Keyword(s):  
Amino Acids ◽  
Electrical Stimulation ◽  
Reduced Glutathione ◽  
Mouth Opening ◽  
Pulse Frequency ◽  
Sea Anemone ◽  
Conducting System ◽  
Nerve Net ◽  
Calliactis Parasitica ◽  
Stimulation Of

1. Activity in all three known conducting systems (the nerve net, SS1, and SS2) may accompany feeding in Calliactis. The most marked response is an increase in pulse frequency in the SS2 (the endodermal slow conducting system) during mouth opening and pharynx protrusion. 2. Electrical stimulation of the SS2 at a frequency of one shock every 5 s elicits mouth opening and pharynx protrusion in the absence of food. 3. A rise in SS2 pulse frequency is also evoked by food extracts, some amino acids, and in particular by the tripeptide reduced glutathione, which produces a response at a concentration of 10(−5) M. 4. Although the SS2 is an endodermal system, the receptors involved in the response to food appear to be ectodermal. 5. The epithelium that lines the pharynx conducts SS1 pulses, but there is some evidence for polarization of conduction.

Long-Term Facilitation in a Swimming Sea Anemone

1959 ◽  
Vol 36 (3) ◽  
pp. 526-532
Author(s):  
DONALD M. WILSON
Keyword(s):  
Sea Anemone ◽  
Experimental Techniques ◽  
Frequency Range ◽  
Nerve Net ◽  
Electric Shocks ◽  
Electrical Shocks ◽  
Probable Site ◽  
A Chain ◽  
Long Term Facilitation

1. Repetition-produced modifications in the behaviour of the swimming sea anemone, Stomphia coccinea, are described. Lowered threshold to number of electrical shocks on successive trials indicates a kind of ‘learning‘ called here longterm facilitation. 2. Dissection of the behaviour into its components, both by experimental techniques and observation of atypical cases, shows the swimming reaction not to be simply a chain of reflexes, but to be ‘centrally’; co-ordinated. 3. The conditions for electrical elicitation of swimming are shocks sufficient in intensity to activate the through-conducting nerve net repeated eight times in the frequency range of 1/2 sec. to 4/sec. Fewer than 8 shocks constitute a subthreshold stimulus in fresh animals; more than 8 are rarely required. 4. Repeated subthreshold stimulation by starfish or by 7 electric shocks result in a long-lasting facilitated state in which the same stimulus repeated hours later may produce a full response. The facilitated condition has been observed to last 7 days. Controls kept without stimulation do not show facilitation. 5. The probable site of this long-term facilitation is discussed. It is suggested that this site is at the point of convergence of the two types of stimulation used and between the through-conducting nerve net and the responding muscles.

Nervous control of light responses in the sea anemone, Calamactis praelongus

1976 ◽  
Vol 65 (1) ◽  
pp. 85-96
Author(s):  
P. S. Marks
Keyword(s):  
Light Response ◽  
Sea Anemone ◽  
Light Stimulation ◽  
Local Effects ◽  
Nervous Control ◽  
Light Responses ◽  
Nerve Net ◽  
Muscular Responses

1. The burrowing sea anemone, Calamactis praelongus, responds to light with local, non-nervous contractions of the column. There are also more extensive responses of the column and retractor muscles co-ordinated by nerve net pulses (NNP's) under pacemaker control. 2. NNP's occur in at least two types of bursts and in sequences which sometimes indicate a rotating site of pulse initiation. 3. Light-evoked NNP sequences can be tape recorded and used later to drive a stimulator to reproduce the original sequences in the same or different anemones, evoking muscular responses which approximate the originals. This technique separates the pacemaker-directed component of the light response from the local effects of light stimulation. 4. Isolated circular and parietal muscles contract slowly when stimulated by light or excited indirectly by NNP's. Retractor muscles are insensitive to light but produce rapid contractions when excited by closely spaced light-evoked NNP's. 5. A model for light responses is proposed which incorporates the characteristics of isolated muscles and intact anemones.

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