Morphogenetic evolution of hydroid colony pattern
A scheme of evolution of hydrozoan colony pattern is proposed based upon the consideration of macromorphogenesis. Four main processes play decisive roles: (1) hard skeleton formation by soft tissues, (2) changes in duration of the growth phase relative to the transition to differentiation in interdependent zones of growth, (3) ratio in growth rates between adjacent zones of growth within the rudiment, the shoot, or the whole colony, and (4) spatial relationships among growth zones. The main tendency in morphological evolution of the hydroids is an increasing integration of the colony as revealed by increasing complexity of its structure. That is from a temporary colony towards the permanent one with highly organised shoots, as hydranths and branches are localised in a strictly arranged manner. An analysis of diverse data allows one to state that the main morphogenetic mechanism of increasing complexity in the hydroid colony is convergence, then fusion, of adjacent growth zones, a variant of heterochrony.
Key words: hydroid colony, heterochrony, colony integration, Hydrozoa
KeywordsGrowth Zone Colony Structure Colonial Hydroid Colony Pattern Hydroid Polyp
Unable to display preview. Download preview PDF.