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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Synamoeba

Synamoeba Grell, 1994 (ref. ID; 4844 original paper)
  1. Synamoeba arenaria Grell, 1994 (ref. ID; 4844 original paper)

Synamoeba arenaria Grell, 1994 (ref. ID; 4844 original paper)

Descriptions

The most remarkable feature of Synamoeba arenaria is that the amoebae do not separate after division but remain connected by pseudopodia-like strands. After a period of feeding, their cell bodies are full of diatoms, whereas the strands and their free-ending branches are free of them. It appears that the diatoms can be phagocytized by the whole surface of the cell bodies, but when the amoebae spread on a "lawn", it becomes evident that the ramified tips of free-ending pseudopodia are used of grasping. As long as the amoebae are full of diatoms, they are rather large. The nuclei with their central nucleoli are clearly visible. After successive binary divisions and exhaustion of the diatom "lawn", the cell bodies become much smaller and nuclei are difficult to recognize. The cytoplasm, which is not subdivided into ecto- and endoplasm, contains about 15-20 light-reflecting granules of an oval shape. Below the amoebae, empty diatom shells may be seen which, under natural on conditions, drift in the surrounding seawater. If the diatom "lawn" is thick enough, the cellular community becomes a three-dimensional meshwork. In a Petri dish, in the absence of wave action, this meshwork can survive several months, even after all diatoms are digested. (ref. ID; 4844)

Comments

From the biological point of view, the feeding communities of Reticulamoeba gemmipara and Synamoeba arenaria are quite different. In Reticulamoeba gemmipara they are temporary. Usually, the amoeboid stages are solitary. By means of their reticulopodia they gather the diatoms near the cell body, so that every amoeba becomes the center of a cluster. The diatoms are not engulfed. Instead, the reticulopodia penetrate their shells and phagocytize the cytoplasm. Final digestion takes place in food vacuoles discernible in the cell bodies. When diatoms are sparse but several amoeboid stages, derived from different zoospores, are present their reticulopodia may fuse to form a feeding community. In this case, several amoeboid stages participate in a single diatom or a group of diatoms. In Synamoeba arenaria the feeding community is permanent. Multiplication occurs only when the cells are associated and full of diatoms. When starving the community desintegrates and the solitary amoebae disperse to find another diatom lawn. Hence, in Reticulamoeba gemmipara the formation of the feeding community serves to overcome periods of starvation, in Synamoeba arenaria to master an abundance of food. In the first case, the cellular association is brought about by a fusion of cells, in the second case by a delay of their division. (ref. ID; 4844)

Type location

Synamoeba arenaria derives from samples of sand, collected at the Playa de las Teresitas, north-east from Santa Cruz de Tenerife (Canary Islands). (ref. ID; 4844)