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Marine benthic organisms can be used as indicators of the quality of environmental status and as monitoring tools to detect natural or anthropogenic perturbations. In temperate waters, metabolic and biochemical responses may be governed by physiological changes driven by seasonal factors. Gathering baseline information on the mechanisms underlying seasonal acclimation patterns is therefore a critical step towards the understanding of the physiological responses of biological indicators. In poikilothermic metazoans, the production of regulatory metabolic enzymes can be used as tools for deciphering the acclimation potential. The aim of this study was to characterize the natural seasonal variability in biometric traits and enzymatic biomarkers over a 12-month period in the sea anemone, Anemonia sulcata (Anthozoa, Cnidaria), from two areas with different environmental and anthropic impacts. Seasonality and site factors affected enzymatic kinetics at tentacle levels, while seasonality, site and biometrical characteristics modulated the same enzymes in the body column of A. sulcata. The results showed a decrease in enzymatic activity in summer and an increased synthesis of enzymes in the late fall and winter months. The interaction between biometric features and temperature appeared significant for mesolittoral sea anemones but not for infralittoral specimens. This study showed seasonal patterns of variations of biochemical responses in A. sulcata, suggesting that this species, an abundant member of shallow rocky bottom communities in temperate European seas, may represent a sensitive bio-indicator organism worth considering for further ecological studies on climate change as well as for environmental monitoring programs.

Anemonia sulcata Pennant absorbs and accumulates tritiated D-glucose dissolved in sea water in natural concentrations (80 μg/l). The rate of decrease of glucose concentration in the sea water can best be described by an exponential function, when the concentration of added glucose exceeds 20 to 25 μg/l. The glucose, absorbed through the ectoderm, is immediately metabolized. This is determinable experimentally by tritiated water which is emitted into the sea water. The rate of uptake estimated experimentally was in the range 3 to 4 μg glucose/g wet weight/h, whilst the rate calculated by V max (maximum absorption rate) was 20 μg/g wet weight/h. The concentration of free glucose in the tentacle tissue is greater by a factor of 105 than that of the medium in which absorption takes place. Absorption is temperature-dependent; the Q10 between 15° and 25°C exceeds 2; translocation is, therefore, energy-dependent. Absorption was diminished by inhibitors, especially by phlorizin. The actinians increase their energy reserves by absorption of glucose (and other dissolved organic substances). The energetic net profit by taking up glucose comprises up to 50% of the energy amount which is equivalent to the oxygen consumption.

Reciprocal inhibition experiments concerning the simultaneous absorption of acidic, basic and neutral amino acids give evidence that Anemonia sulcata Pennant (Coelenterata: Anthozoa) possess at least three distinct uptake systems for amino acids. The absorption of amino acids belonging to the same class is mutually inhibited. Increasing inhibitor concentrations reduce the uptake of the substrate successively, indicating that the receptors are saturated only at high substrate concentrations; this is not the case under natural conditions. The uptake system for acidic amino acids is highly specific; uptake is not inhibited by either basic or neutral amino acids. The specificity for basic amino acids is lower; uptake is influenced by neutral amino acids. Neutral amino acids are absorbed either by one single system with broad specificity or by several systems with overlapping specificity. D- and L-isomers seem to be absorbed by the same system, as the uptake is reciprocally inhibited. The restricted specificity of the amino-acid uptake systems, especially those for neutral amino acids, could be explained as an adaptation to avoid accumulation of certain amino acids in a most economic way. Moreover, a broad spectrum of various dissolved organic materials can thus be utilized. The experiments also give evidence that anemones are able to supply their metabolism completely with the necessary substances by absorbing dissolved organic material. The absorbed substances may, furthermore, be vital for the metabolism, although their individual energy content may be negligible. Anemones display optimum fitness to an important environmental factor-dissolved organic material — on a macromolecular level, in addition to structural and physiological adaptations.

A highly specific recognition system, capable of distinguishing between allogeneic (non-clonemates) and syngeneic (clonemates) conspecifics, exists in Anemonia sulcata (Coelenterata: Anthozoa). During a competitive interaction between allogeneic individuals, specialized structures (acrorhagi) are exposed and used to sting opponents. This complex behavior is called the acrorhagial response. In order to quantify this behavior we measured the acrorhagial response time (period from first contact with opponent to full expansion of acrorhagi). More than 320 reciprocal histoincompatibility responses were recorded. These histoincompatibility (H) markers are free components of the sea anemone mucus: they were characterized as glyco-proteins of a molecular weight

The effects of two toxic polypeptides isolated from Anemonia sulcata Pennant (Anthozoa) were tested on Gadus morhua, Pleuronectes platess and Platichthys flesus. In tramuscular injections caused paralysis and death, with symptoms similar to those of death caused by lack of oxygen. In cod, the LD50 dose of Toxin II was 50 times higher chan that of Toxin I (Toxin I=6.9 mg/kg, Toxin II=0.14 mg/kg). Flatfish were less sensitive. The LD50 of Toxin II was 0.37 mg/kg for Platichthys flesus and 0.38 mg/kg for Pleuronectes platessa. Both toxins are less lethal to fishes than to crustaceans.

The discharge and mode of action of the microbasic mastigophores (b-Rhabdoids) of Anemonia sulcata Pennant (Anthozoa) tentacles were examined using light and electron microscopical techniques. The statistical analysis of different morphological parameters of 100 nematocysts before and after their complete discharge revealed four different phases in the process of discharge. The first phase consists of the opening of the three opercular flaps. The second phase is characterized by the extrusion of the shaft. Osmotic pressure generated by the nematocyst propagates the extremely fast shaft discharge. The third phase, the evagination of the long tubule, is propagated by intrinsic mechanical forces stored in the tubule's twists and coils. During the process of evagination the tubule length increases by 95%, its circumference by 17%. Its forward motion is produced by the dilatation of its circumference and undoing of its twists. This motion is supported by the pressure which is generated by the hydration of the capsular matrix. The fourth phase consists in the extrusion of soluble capsular material at the tip of the evaginated tubule. During discharge the net volume of the nematocyst increases by 182%. This expansion is only possible if a high osmotic pressure is generated within the cyst. The extrusion of the shaft is the crucial phase in the discharge of the microbasic mastigophores, because without the puncture produced by the shaft the tubule is not able to overcome even surfaces of low viscosity media. The function of these tentacular nematocysts is the mechanical capture of prey organisms and, most probably, the introduction of unknown toxins into the latter.

Anemonia sulcata resorbierte und akkumulierte tritiummarkierte l-Aminosauren aus Meerwasser, welche diesem in naturlicher Konzentration zugesetzt worden waren (70–700 nMol/l). Die Aufnahme erfolgte nahezu ausschlieslich ektodermal; der uberwiegende Teil der aufgenommenen und dann eingebauten Aminosauren befand sich auch nach langerer Inkubation im Ektoderm. Diese Tatsache ist auf unterschiedliche cytologische Differenzierungen von Ento- und Ektoderm zuruckzufuhren. Elektronenmikroskopische Aufnahmen zeigen, das nur das Ektoderm resorbierende Strukturen (Mikrovilli) besitzt. Die Aufnahmeraten waren (von naturlichen Konzentrationen ausgehend) fur die untersuchten Aminosauren verschieden hoch (2–10 μg/g Frischgewicht/h). Die aufgenommene Menge war von der Ausenkonzentration abhangig. Die Konzentrationen, unterhalb denen nur noch eine sehr geringe Aufnahme registriert werden konnte, schwankten fur die einzelnen Aminosauren zwischen 10 und 100 nMol/l. Eine Gruppe von Aminosauren (Phe, Lys, Leu, His, Pro) wurde vorwiegend in den Synthesestoffwechsel eingeschleust, eine andere (Gly und Ser) wurde uberwiegend oxydativen Prozessen zugefuhrt. Der Gehalt an freien Aminosauren von Tentakelgewebe wurde bestimmt. Die Konzentration von Glycin z.B. ist im Gewebe 107mal hoher als im Medium, aus dem noch resorbiert wird. Die Aufnahme erfolgt daher mit groster Wahrscheinlichkeit aktiv. Formale Berechnungen zeigen, das den Tieren durch die Aufnahme geloster organischer Verbindungen ein Energiegewinn erwachst; dieser liegt uber dem Energieverbrauch, der dem Sauerstoffverbrauch aquivalent ist.

Investigations have been carried out on the carotenoids in Anemonia sulcata (Pennant) and Actinia equina (L.) (Coelenterata: Anthozoa) from the Adriatic Sea. The presence of the carotenoids was determined by means of columnar and thin-layer chromatography. The following carotenoids were found: Anemonia sulcata: β-carotene, lutein-like (epoxy and free) and astaxanthin; Actinia equina: α-carotene, β-carotene, actinioerythrin, lutein-like (?) and astaxanthin (ester and free).

OUR observations1 show that sponge species of distant taxonomic position, even if they belong to different classes such as Calcispongiae and Demospongiae, may form bispecific cell aggregates after dissociation.

IN an earlier report1, it was concluded from evidence obtained by pharmacological tests and paper chromatography that 5-hydroxytryptamine was a constituent of the sea-anemones, Metridium senile and Calliactis parasitica. More 5-hydroxytryptamine-like material was obtainable from Metridium tentacles, with their nematocysts, than from body wall which is relatively free of nematocysts. This led to the suggestion that 5-hydroxytryptamine might be a pain-producing factor in these stinging organelles. An independent study2 of material released on discharge of isolated Metridium nematocysts yielded two hydroxyindoles tentatively identified by chromatography as 5-hydroxytryptophan and bufotenine. The identification of 5-hydroxytryptamine in Calliactis has now been made quite certain3,4. However, the very large amount found in the coelenteric organ of this species and the relatively small amount in tentacles, coupled with the finding of little 5-hydroxytryptamine in Metridium and Anemonia sulcata, led Mathias, Koss and Schachter3,4 to conclude that it is unlikely that 5-hydroxytryptamine is associated with nematocysts. Further evidence is now available that this conclusion may not be fully warranted.

THERE has in the past been considerable discussion concerning the nature of the stimulus which causes the nematocysts of Cœlenterates to discharge, In some cases, it is quite clear that the mechanical stimulus to the cnidoblast causes an, explosion of the enclosed nematocyst. But for the majority of nematocysts, discharge only takes place in the presence of food, and it has been suggested that the stimulus is essentially a chemical one. During a long series of experiments on the feeding of Anemonia sulcata, interesting evidence has been obtained as to the mode of excitation of nematocysts. In agreement with Parker and Van Alstyne1, I find the cnidoblasts of the tentacles of Anemonia are independent effectors. They respond, however, selectively to food. If touched by a clean glass rod, no discharge is normally obtained. If touched with a piece of human skin, there is copious discharge. The discharge, however, only takes place where there has been mechanical contact. Strong food solutions sometimes seem to cause spontaneous discharge of a few nematocysts. But it is easy to show that this is of no direct significance in the normal reaction. As a direct chemical stimulus, food is far less effective than certain surface-active substances such as bile salts (0.1 per cent), which produce a complete spontaneous discharge of the nematocysts. This action is, however, quite different from the normal response. Cotton wool soaked in dilute bile salts does not adhere to the tentacles ; the nematocysts being discharged, by the diffusing bile salt before contact is made. On the other hand, cotton wool soaked in food solution causes extensive discharge of nematocysts into the mass on contact. This is true even though the food solution employed is far below the concentration for spontaneous discharge. Clean cotton wool, soaked in sea water as a control, produces no discharge.

THE feeding mechanisms of coelenterates were the subject of much interest at the turn of the century, and were investigated by such notable biologists as Loeb1, Jennings2 and Parker3. Renewed consideration has been given to these problems in the past few decades largely through the work of Pantin4, who used the sea anemone, Anemonia sulcata, and more recently through the experiments of Loomis5. The latter, who showed that small amounts of the tripeptide reduced glutathione activated feeding in the fresh-water Hydra littoralis, directed attention toward the chemical activation of feeding6,7. But the question of mechanical stimulation of feeding, although demonstrated in some sea anemones by earlier workers2,8, has been neglected in recent years. In this communication, I describe some observations which show that the feeding response of the sea anemone Epiactis prolifera can be repeatedly activated by remarkably slight mechanical stimulation with inert objects.

ALTHOUGH much work has been carried out on the biochemistry and mechanism of discharge of cnidae in the phylum Cnidaria, the past decade in particular has shown a swing towards research on the actual stimulus for discharge, which, along with other aspects of nematocyst researches, has been reviewed by Picken and Skaer1. Pantin2 made a great advance in our understanding of this problem, working on cnidae in isolated tentacles of Anemonia sulcata. He concluded that the cnidae behave as independent effectors, a fact which must be established if a hypothesis based on external environmental stimuli is to be postulated without involving the nervous system.