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.

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 A method for recording electrical activity from the body wall nerve nets in sea anemones

1995 ◽  
Vol 198 (3) ◽  
pp. 817-820
Author(s):  
K Cho ◽  
I D McFarlane
Keyword(s):  
Electrical Activity ◽  
Body Wall ◽  
Myoepithelial Cells ◽  
The Body ◽  
Sea Anemones ◽  
Nerve Net ◽  
Slow Conduction ◽  
Calliactis Parasitica ◽  
Type C ◽  
First Time

Glass microelectrodes were used to record electrical activity from thin rings cut from the column of the sea anemone Calliactis parasitica. This is the first time that pulses have been recorded from the nervous system in the column. Three pulse types were detected, types A, B and C. Type A pulses are probably associated with neurones of the through-conducting nerve net. Type B pulses may be from the endodermal slow conduction system (SS2). Type C pulses have not previously been recorded and are thought to represent activity in a local nerve net. At this stage we cannot positively state whether the recordings are intracellular from endodermal myoepithelial cells or are extracellular from the sub-epithelial region.

Electrophysiology of two parallel conducting systems in the colonial Hexacorallia

1976 ◽  
Vol 193 (1110) ◽  
pp. 77-87 ◽  
Keyword(s):  
Electrical Activity ◽  
Refractory Period ◽  
Feeding Behaviour ◽  
Conduction System ◽  
Mechanical Stimuli ◽  
Nerve Net ◽  
Slow Conduction ◽  
Calliactis Parasitica ◽  
Oral Disk ◽  
Dendrogyra Cylindrus

Extracellular polythene suction electrodes have been used to record electrical activity in four species of Madreporaria - Dendrogyra cylindrus, Meandrina meandrites, Mussa angulosa and Eusmilia fastigiata . A colonial conduction system, believed to be the nerve net, was found in all species. It conducted without decrement between all polyps. A second colonial system was found in Meandrina, Mussa and Eusmilia . Pulses could be recorded only from tentacles or oral disks though the system could be excited by electrical or mechanical stimuli to any part of the colony. In the tentacles and oral disk, this conduction system had a refractory period of about 60 ms while in the column or interpolyp regions the refractory period was much longer - up to several seconds. The effect of these differences was to limit the frequency of conduction of pulses in this system between polyps. The second system is compared to the s. s. 1 (ectodermal slow conduction system) of the sea anemone Calliactis parasitica . It is the first demonstrated example of a colonial slow conduction system in the Hexacorallia and is similar in properties to a colonial slow conduction system previously described for Pennatula phosphorea (Octocorallia). The slow conduction system may have a rôle during feeding behaviour by promoting expansion of tentacles and the production of mucus.

scholarly journals Co-Ordination of Pedal-Disk Detachment in the Sea Anemone Calliactis Parasitica

1969 ◽  
Vol 51 (2) ◽  
pp. 387-396
Author(s):  
I. D. MCFARLANE
Keyword(s):  
Electrical Stimulation ◽  
Electrical Activity ◽  
Mechanical Stimulation ◽  
Average Frequency ◽  
Conduction System ◽  
Identical Stimulus ◽  
Slow Conduction ◽  
Calliactis Parasitica ◽  
Behavioural Sequence ◽  
Stimulation Of

1. Electrical activity has been recorded from the sphincter region of Calliactis parasitica during the behavioural sequence in which the anemone detaches from the substrate and attaches to a Buccinum shell. The ectodermal slow-conduction system (SS1) fires repetitively, the majority of observed pulses occurring in the period prior to detachment (a typical example is 25 SS1pulses at an average frequency of 1 pulse/7 sec.). Shell-tentacle contact is essential for stimulation of SS1activity. 2. Mechanical stimulation of the column excites the SS1, and 30 stimuli at a frequency of about one shock/5 sec. give pedal disk detachment. 3. Electrical stimulation of the ectoderm excites the SS1and about 30 stimuli at frequencies between one shock/3 sec. and one shock/9 sec. produce detachment. Detachment and the SS1 have an identical stimulus threshold. It is concluded that detachment is co-ordinated by the SS1.

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.

The role of a ‘local electrical conduction system’ during feeding in the Devonshire cup coral Caryophyllia smithii Stokes and Broderip

1984 ◽  
Vol 220 (1221) ◽  
pp. 489-500 ◽  
Keyword(s):  
Electrical Conduction ◽  
Feeding Behaviour ◽  
Complete Sequence ◽  
Conduction System ◽  
Oral Disc ◽  
Nerve Net ◽  
Slow Conduction ◽  
Spread Of Excitation ◽  
Radial Spread ◽  
Slow System

The electrical conduction systems underlying the control of feeding behaviour are described for the solitary cup coral Caryophyllia smithii . A nerve net and a slow conduction system were found to conduct non-decrementally to all parts of the animal and to control symmetrical parts of the feeding behaviour such as polyp expansion. The slow system was activated by receptors on the tentacles and oral disc. Of particular interest was the presence of a ‘local conduction system’ in the tentacles and oral disc. This system was shown to be important in the control of local, asymmetrical parts of the feeding behaviour such as the movements of single tentacles. The local conduction system consisted of radially conducting units each of which consisted of a single tentacle and its associated sector of oral disc. This allowed the radial spread of excitation (at less than 2 cm s -1 ) from tentacle to mouth or mouth to tentacle but did not allow excitation to spread around the oral disc. The threshold for excitation of the local conduction system was above that of the nerve net or slow conduction system. The cellular basis for local conduction is unknown but may involve the oral disc radial muscles and the tentacle longitudinal muscles. By appropriate electrical stimulation of the nerve net, slow system and local conduction system, a complete sequence of feeding behaviour could be evoked. This closely resembled the behaviour shown during normal feeding and included polyp expansion, local pharynx movements and local tentacle bending. It is concluded that ‘local conduction’ is an important element to include in models purporting to explain the control of anthozoan behaviour, particularly that in which local movements are important.

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.

Two slow conduction systems co-ordinate shell-climbing behaviour in the sea anemone Calliactis parasitica

1976 ◽  
Vol 64 (2) ◽  
pp. 431-445
Author(s):  
I. D. McFarlane
Keyword(s):  
Electrical Stimulation ◽  
Low Frequency ◽  
Sensory Response ◽  
Pulse Interval ◽  
Nerve Net ◽  
Slow Conduction ◽  
Calliactis Parasitica ◽  
Climbing Behaviour ◽  
The Mean ◽  
Stimulation Of

1. Pulses in two slow conducting systems, the ectodermal SS 1 and the endodermal SS 2, were recorded during shell-climbing behaviour. The mean pulse interval of SS 1 pulses was 7–4 s and that of SS 2 pulses was 6-4 s. Activity in both systems may arise as a sensory response of tentacles to shell contact, but the SS 1 and SS 2 may not share the same receptors. 2. Electrical stimulation of the SS 1 and SS 2 together, at a frequency of 1 shock every 5 s, elicits shell-climbing behaviour in the absence of a shell. 3. Low-frequency nerve-net activity (about 1 pulse every 15 s) accompanies column bending during both normal and electrically elicited responses. This activity probably arises as a result of column bending and is not due to a sensory response to the shell.

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.

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.

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