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.

Excitatory Actions of Antho-RFamide, An Anthozoan Neuropeptide, on Muscles and Conducting Systems in the Sea Anemone Calliactis Parasitica

1987 ◽  
Vol 133 (1) ◽  
pp. 157-168 ◽  
Author(s):  
I. D. McFARLANE ◽  
D. GRAFF ◽  
C. J.P. GRIMMELIKHUIJZEN
Keyword(s):  
Electrical Activity ◽  
Slow Muscle ◽  
Conduction System ◽  
Sea Anemone ◽  
Sea Anemones ◽  
Nerve Net ◽  
Direct Excitation ◽  
Calliactis Parasitica ◽  
Muscle Groups ◽  
Fast Muscles

In the sea anemone Calliactis parasitica endodermal application of the anthozoan neuropeptide Antho-RFamide (<Glu-Gly-Arg-Phe-amide), at a concentration of 10−6 or 10−7moll−1, caused a long-lasting increase in tone, contraction frequency and contraction amplitude in several slow muscle groups but had no effect on contractions in fast muscles. The effects were investigated further in isolated muscle preparations. Ectodermal application to whole animals had no effect on muscle contractions. Both ectodermal and endodermal application, at 10−7moll−1, raised electrical activity in an ectodermal conduction system, the SSI, but had no effect on an endodermal conduction system, the SS2. Electrical activity in the SS2 was increased by application at 10−6moll−1 to the endoderm but not to the ectoderm. The peptide had no effect on the through-conducting nerve net. It is concluded that contractions evoked by Antho-RFamide may be partly due to neuronal activity, but probably also involve direct excitation of the muscles. The diverse excitatory actions of Antho-RFamide suggest that it may be a neurotransmitter or neuromodulator in sea anemones.

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.

scholarly journals Nerve Nets and Conducting Systems in Sea Anemones: Two Pathways Excite Tentacle Contractions in Calliactis Parasitica

1984 ◽  
Vol 108 (1) ◽  
pp. 137-149
Author(s):  
IAN D. MCFARLANE
Keyword(s):  
Electrical Activity ◽  
Conduction System ◽  
Sea Anemones ◽  
Single Shock ◽  
Nerve Net ◽  
Slow Conduction ◽  
Calliactis Parasitica ◽  
Slight Movement ◽  
Pulse Stimulation ◽  
Stimulation Of

1. Single shocks to the column sometimes evoke tentacle contractions, ranging from slight movement of a few scattered tentacles to rapid bending or shortening of all the tentacles. Some individuals are more responsive than others. Complex bursts of electrical activity follow single shocks, but only in tentacles that contract. 2. These single shocks excite pulses in two conducting systems - the through-conducting nerve net (TCNN) and the ectodermal slow conduction system (SSI). When a single shock evokes contractions and bursts of electrical activity, these usually follow the SSI pulse, rarely the TCNN pulse. Stimulation of the SSI alone causes tentacle contraction in responsive anemones. 3. Fast tentacle contractions always follow the second of two closelyspaced TCNN pulses: the TCNN shows facilitation (Pantin, 1935a). An SSI pulse, however, does not facilitate subsequent pulses in either the SSI or TCNN. 4. There are two pathways for activation of tentacle contractions. The TCNN pathway is mechano-sensitive and normally requires facilitation. The SSI pathway is mechano- and chemosensitive, only requires a single SSI pulse to evoke contraction, but is very labile. It is proposed that the TCNN and the SSI do not excite the ectodermal muscles directly, but via a multipolar nerve net.

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 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.

Control of the Pacemaker System of the Nervenet in the Sea Anemone Calliactis Parasitica

1974 ◽  
Vol 61 (1) ◽  
pp. 129-143
Author(s):  
I. D. MCFARLANE
Keyword(s):  
Sensory Feedback ◽  
Pulse Frequency ◽  
Pulse Number ◽  
Pulse Action ◽  
Conduction System ◽  
The Body ◽  
Optimum Frequency ◽  
Nerve Net ◽  
Slow Conduction ◽  
Calliactis Parasitica

1. The rhythm of spontaneous nerve-net pulses is reset by intercalated evoked nerve-net pulses. 2. The origin of spontaneous nerve-net pulses can shift during a burst. There seem to be many potential pacemakers, widely distributed throughout the body, but apparently absent from the tentacles. 3. If a spontaneous or evoked pulse in the endodermal slow conduction system (SS 2) occurs during a burst, the nerve-net pulse intervals are increased during a 15-30 sec period following the SS 2 pulse. Additional SS 2 pulses cause a further increase in pulse intervals. 4. Nerve-net bursts are followed by a sequence of muscular contractions. The size of the contraction shown by any muscle group depends on nerve-net pulse number and frequency, the optimum frequency being different for different muscles. It is suggested that the SS 2 pulse action on nerve-net pulse frequency can significantly alter the behavioural output of nerve-net bursts. The SS 2 activity may represent sensory feedback on to the nervous pacemakers.

Facilitation in Sea Anemones

1945 ◽  
Vol 22 (1-2) ◽  
pp. 32-36
Author(s):  
D. M. ROSS
Keyword(s):  
Neuromuscular Transmission ◽  
Muscular Contraction ◽  
Single Stimulus ◽  
Sea Anemones ◽  
Metridium Senile ◽  
Neuromuscular Response ◽  
Calliactis Parasitica ◽  
Sensitizing Effect

1. Extracts of the sea anemones, Calliactis parasitica and Metridium senile, have been prepared and their effects on the neuromuscular response of these anemones tested. The presence of extract sensitizes the organism so that a response is given to a single stimulus, whereas normally this occurs only on the second and subsequent stimuli. No other significant effects were observed. 2. The sensitizing effect of the extract differs from the effect of a sensitizing drug like tyramine; it appears more quickly, more regularly, and it is rarely accompanied by an increase in the size of the muscular contraction. 3. The fact that a substance with sensitizing properties has been detected in anemones supports the view that a ‘sensitizer’ or ‘facilitator’ exists and takes part in neuromuscular transmission in these animals. Nevertheless, the extract, like the sensitizing drugs, lacks some of the properties that would be expected of a true ‘sensitizer’ or ‘facilitator’.

scholarly journals Nerve Net Pacemakers and Phases of Behaviour in the Sea Anemone Calliactis Parasitica

1983 ◽  
Vol 104 (1) ◽  
pp. 231-246
Author(s):  
IAN D. McFARLANE
Keyword(s):  
Electrical Stimulation ◽  
Pulse Number ◽  
Sea Anemone ◽  
Sea Anemones ◽  
Nerve Net ◽  
Partial Activation ◽  
Calliactis Parasitica ◽  
Slow System ◽  
Stimulation Of

Bursts of through-conducting nerve net (TCNN) pulses, 20–45 min apart, were recorded from Calliactis attached to shells. Within 15–25 min of the anemones being detached the TCNN bursts suddenly became more frequent (only 4–11 min apart). Such bursts continued for several hours if re-attachment was prevented. In an attached anemone simultaneous electrical stimulation of the TCNN and ectodermal slow system (SS1) with 20–30 shocks at one every 5 s also led to more frequent TCNN bursts, whether or not detachment took place. If, however, the anemone remained attached, the intervals between bursts returned to the normal resting duration after about 90 min. In all cases the decay of the 4–11 min interval TCNN bursts involved a reduction in pulse number, not an increase in burst interval. Partial activation of the TCNN pacemakers followed stimulation of the SS1 alone. It is suggested that in sea anemones the change from one behavioural phase to another is associated with a change in the patterned output of nerve net pacemakers.

The role of L-Dopa in the nervous system of sea anemones: a putative inhibitory transmitter in tentacles

1995 ◽  
Vol 198 (4) ◽  
pp. 1045-1050
Author(s):  
D Hudman ◽  
I D McFarlane
Keyword(s):  
Sphincter Muscle ◽  
Sea Anemones ◽  
Extracellular Recordings ◽  
Nerve Net ◽  
Local Inhibition ◽  
Calliactis Parasitica ◽  
Inhibitory Transmitter ◽  
Spontaneous Contractions ◽  
Longitudinal Muscles

1. l-Dopa evokes transitory inhibition of spontaneous contractions of tentacle longitudinal muscles in sea anemones. It also modulates spontaneous contractions of the sphincter muscle in isolated preparations and whole animals. 2. Extracellular recordings from the tentacles of Calliactis parasitica show that l-Dopa evokes bursts of electrical events apparently associated with a local nerve net. 3. We propose that l-Dopa be added to the growing list of putative transmitter substances in sea anemones, its action being to coordinate local inhibition of spontaneous tentacle contractions.

An Adrenergic Nervous System in Sea Anemones

1963 ◽  
Vol s3-104 (68) ◽  
pp. 531-534
Author(s):  
ERIK DAHL ◽  
BENGT FALCK ◽  
CLAES VON MECKLENBURG ◽  
HARRY MYHRBERG
Keyword(s):  
Nervous System ◽  
Fluorescence Microscopy ◽  
Motor Function ◽  
New Method ◽  
Sea Anemones ◽  
Fluorescent Substance ◽  
Metridium Senile ◽  
Adrenergic Nervous System ◽  
Oral Disk

A new method for the demonstration of certain mono-amines by means of fluorescence microscopy was applied to the tentacles and oral disk of the sea anemones Metridium senile and Tealia felina. A fluorescent substance was found in the cells and fibres of the tentacular ectodermal nervous system. This nervous system probably has a double sensory and motor function.

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