Morphogenetic gradients in multiple-graftHydra viridis. I. The effects of colcemid and colchicine

Publisher Website
Google Scholar
Abstract
The morphogenesis of so‐called secondary (2°) heads, budding regions and feet, and separations at graft borders is studied in multiple‐graft animals containing three gastric regions (3g animals) treated with Colcemid or colchicine. Control animals consist of three non‐treated pieces. Animals consisting of two non‐treated and one treated piece are also employed. The main effects of Colcemid are the promotion of graft healing at the distal graft border, and of 2° head formation on the proximal gastric region (g‐1). Colchicine also promotes graft healing at the distal graft border, but in contrast to the effect of Colcemid, promotes the formation of ectopic feet (tertiary feet) and inhibits head regeneration at the distal end of the middle gastric region (g‐2). Colchicine also accelerates an inversion of polarity in 2° budding regions on the g‐2 pieces of animals with 2° heads on their g‐1 pieces. Treatment of a distal graft piece with Colcemid promotes 2° head formation on the nearest proximal piece which is not treated, but the inhibition of 2° head formation by colchicine occurs only on colchicine treated pieces. The morphogenetic effects of the drugs are interpreted as consequences of their actions on nerve differentiation and cell division. The paper argues that homeostatic control of a hydra's cell population depends on dividing cells influencing cell loss, and that similar mechanisms are involved in the rejection of a graft and the separation of a bud.