Eine Fisch-Seeigel-Partnerschaft. Untersuchungen optischer reizparameter beim formenerkennen

The shrimp Tuleariocaris sansibarica and the fish Siphamia permutata live between the spines of the sea urchin Diadema setosum. Visual attration is important in maintaining this association. The spines of the sea urchin act as an optical stimulus for shrimp and fish. The specific optical stimuli which the shrimp (Fricke and Hentschel, 1971) and the fish perceive during their stay with the urchin were investigated and compared. Dummy experiments in the coral reef of the Red Sea (Eilat, Israel) have shown that the fish is able to distinguish between at least 5 different stimuli patterns: color (black or white), diameter, number, distance between spines, and orbital position. Color is less attractive than number and orbital position; the relations between number and orbital position are nearly linear. The different visual systems of shrimp and fish are capable of selecting similar optical parameters. Slight differences in evaluation of single parameters are understood as adaptive processes to an identical environment.