Control of formation of the two types of polyps in Thecocodium quadratum (Hydrozoa, Cnidaria).

ABSTRACT

Thecocodium quadratum (Werner, Jber. Biol. Anst. Helgoland, 1965) is a colonial hydroid which produces 2 different types of polyps gastrogonozooids and dactylozooids. The mouthless dactylozooids bear tentacles and catch the prey, which is then taken over and swallowed by the gastrogonozooids which have no tentacles. It is obvious that for a colony to survive both polyps must exist simultaneously arranged in a certain spatial pattern. Our experiments indicate that the formation of polyps in a growing culture is governed by at least 3 principles (1) short range inhibition between polyps irrespective of their differentiation; (2) long range specific inhibition between gastrogonozooids; and (3) long range supporting influence (lateral help, Meinhardt, H., Models of Biological Pattern Formation, 1982) between gastrogonozooids and dactylozooids.