Preliminary experiments with Bryozoa in a simple apparatus for producing continuous water currents

Abstract

1. An improved type of bubble-pump and an apparatus for producing continuous water currents, designed especially for utilization of planktonic food, are described. 2. The operation of the apparatus is easy; current speeds can be regulated from 0 to about 1/2 m/sec. 3. The apparatus can be used for experiments on small animals and plants, especially sessile and hemisessile forms. 4. Bryozoans Farrella repens, Conopeum seurati, and C. reticulum, exposed to water currents at 15° C, exhibited no preferred growth direction relative to the current direction. 5. In fast currents Farrella repens and Electra monostachys covered their substratum densely with zooids. 6. In slow currents Electra monostachys and E. pilosa revealed positive rheotropic growth responses. 7. Slow water currents appear to stimulate Electra pilosa to form erect colony parts. 8. Water currents probably influence the development of ball-formed colonies in Electra pilosa forma erecta. The ball-form may be the result of an interaction between retarding effects of strong water currents at the periphery and stimulating effects of slow water currents in the interior parts of the ball. © 1970 Biologischen Anstalt Helgoland.