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’.

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.

Facilitation in Sea Anemones

1952 ◽  
Vol 29 (2) ◽  
pp. 235-254
Author(s):  
D. M. ROSS
Keyword(s):  
Bile Salt ◽  
Standardized Tests ◽  
Single Stimulus ◽  
Living Animal ◽  
Sea Anemones ◽  
Nerve Net ◽  
Reported Effect ◽  
High Doses ◽  
Electrical Stimuli ◽  
Very High

1. The previously reported effect of anemone extracts, the occurrence of quick closing responses to single electrical stimuli in Metridium, has been re-investigated. In standardized tests it was found that whereas hundreds of stimuli are required for each response to a single stimulus in untreated animals, after anemone extract the incidence of such responses is one per nine stimuli. 2. The incidence of these responses falls off with decreasing doses of extract and the effect disappears when less than 1/500th of the material from a single large Metridium is administered. There is no evidence that extracts from ‘stimulated’ and ‘unstimulated’ (i.e. anaesthetized or quick-frozen) anemones differ in potency. Extracts from divided animals show greater activity in the ‘sphincter-disk’ fraction. 3. The incidence of the responses also falls off in time and is highest from 15 to 30 sec. after beginning the treatment. The effect is sporadic and short-lived and responses to two or more successive stimuli are exceptional. 4. A number of treatments, such as drastic changes in pH, KCl(K+ x 8), tetramethylammonium hydroxide (1 : 100), NH4C1 (1 : 340) and especially bile salt and saponin, have similar effects. Drugs with neuro-muscular effects elsewhere (acetylcholine, adrenaline, tyramine, histamine, etc.) were generally ineffective except at very high doses. Food stimulants too were ineffective. 5. From the time relations and other aspects of the responses to single stimuli it is concluded that the effect should not be attributed to a substance with the function of a ‘facilitator’ in the living animal. 6. While the effects are consistent with the passage of occasional adventitious impulses in the nerve net, there is a singular absence of spontaneous or post-stimulus contractions. Certain implications of this feature of the results are discussed.

Biochemical Genetic Variation, Growth and Regeneration of the Sea Anemone, Metridium, of British Shores

1985 ◽  
Vol 65 (1) ◽  
pp. 141-157 ◽  
Author(s):  
Ann Bucklin
Keyword(s):  
Genetic Differentiation ◽  
Taxonomic Status ◽  
Sea Anemone ◽  
Sea Anemones ◽  
The United Kingdom ◽  
Metridium Senile ◽  
Genetic Differentiation Of Populations ◽  
Biochemical Genetic ◽  
Enormous Number ◽  
Interesting System

Sessile organisms capable of asexual reproduction may be expected to show much genetic differentiation among local populations: mating between distant individuals is unlikely and genetic drift will contribute to differentiation since habitats can be colonized by one or a few individuals. This study investigates genetic differentiation of populations of the sea anemone Metridium senile (L.) in Great Britain. Individuals of M. senile are sessile and reproduce both sexually, by free-spawning of gametes, and asexually, by regeneration of fragments torn from the pedal disc. Metridium senile is one of the most common and widespread of British sea anemones (Manuel, 1981); reports place it at an enormous number and variety of sites around Britian (unpublished results of surveys by the Underwater Conservation Society of the United Kingdom). The extensive geographic range and variability of the species have confounded attempts to determine the taxonomic status of the ecological and morphological forms, but make it an interesting system for genetic analysis.

THE RESPONSE TO MOLLUSCAN SHELLS OF THE SWIMMING SEA ANEMONES STOMPHIA COCCINEA AND ACTINOSTOLA NEW SPECIES

1967 ◽  
Vol 45 (6) ◽  
pp. 895-906 ◽  
Author(s):  
D. M. Ross ◽  
L. Sutton
Keyword(s):  
Organic Matter ◽  
New Species ◽  
Behavior Pattern ◽  
Hermit Crabs ◽  
Behavior Patterns ◽  
Sea Anemones ◽  
Modiolus Modiolus ◽  
Calliactis Parasitica ◽  
Main Components ◽  
Pedal Disc

Behavior patterns in the sea anemones Stomphia coccinea and Actinostala new species are described by which these animals settled preferentially on shells of Modiolus modiolus (commensal of S. coccinea) after they have been made to swim in response to the appropriate stimuli (the starfishes Dermasterias or Hippasteria, the nudibranch Aeolidia papillosa, etc.). Tentacular and oral contact without adhesion, followed by great distension of the pedal disc and some flexion of the column towards the shell, were the main components of these behavior patterns. Anemones which had been allowed to settle on other surfaces not more than 6 h previously migrated to shells which were brought into contact with the tentacles. Shells which were boiled in alkali to remove organic matter lost their capacity to elicit the response. This behavior pattern is compared with that of Calliactis parasitica, a commensal of hermit crabs which shows a preference for settling on shells of large gastropods.

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.

Quick and Slow Contractions in the Isolated Sphincter of the Sea Anemone, Calliactis Parasitica

1957 ◽  
Vol 34 (1) ◽  
pp. 11-28
Author(s):  
D. M. ROSS
Keyword(s):  
Latent Period ◽  
Spontaneous Activity ◽  
Neuromuscular Transmission ◽  
Sea Anemone ◽  
Optimal Frequency ◽  
Temporal Features ◽  
Calliactis Parasitica ◽  
Slow Contraction

1. The neuromuscular activities of isolated marginal sphincter preparations of the sea anemone, Calliactis parasitica, have been studied. They showed almost no rhythmical or spontaneous activity. 2. In addition to the facilitated step-like quick contractions in response to stimuli at frequencies between 0·2 and 3·0 sec., the preparations gave smooth slow contractions in response to stimuli (usually not less than 6 stimuli were necessary) at frequencies up to about 15 sec. (at 17-18°C.). These contractions are similar to those given by the so-called ‘slow’ muscles which do not take part in the quick closing movements of the animal. 3. A study was made of the relations between the size and latent period of the slow contraction and the number and frequency of stimuli delivered. At each frequency there is a threshold number of stimuli which only just gives a response; with additional stimuli the response gets bigger until a maximum is reached. There is an optimal frequency (stimuli about 6-8 sec. apart at ordinary temperatures) at which the biggest responses are obtained with fewest stimuli. 4. Certain mechanical and temporal features of the quick and slow contractions are compared and the observations are discussed in relation to current views on neuromuscular transmission and innervation in these and other invertebrates.

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.

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