A Study of Metric characters for Bryozoan Taxonomy

点击翻译按钮获取中文摘要

Colony growth pattern is compared between the two cheilostome bryozoans Membranipora serrilamella and Thalamoporella rozieri. Some rules of zooids budding were revealed to be different between the two species as follows :(1) Increasing rates of both single and twin zooids according to the area expanding of colony are similar between the two species.(2) The timing of bifurcation of zooid row is strongly correlated with the width of zooid in both species. In other words, there is a critical threshold of zooid width between the single and twin zooids.(3) In the colonies of Thalamoporella rozieri, aproximately 9 % of zooid rows come to an end before the colony edge, while 0 % in Membranipora serrilamella. This is caused by the more frequent bifurcation in the former than in the latter.(4) Nearly 12 % of the zooids in a colony of Membranipora serrilamella are twins while aproximately 18 % in Thalamoporella rozieri.(5) The zooid width is not correlated with the development of heterozooids. The frequency of heterozooids increases in colony edge.All of the data obtained by the present study consistently tell us that the zooids of a colony of Membranipora serrilamella are regularly arranged in order to make their food intake efficiency high. This principle for existence, however, can not be directly applied for Thalamoporella rozieri. It is concluded that the defense of colony performed by heterozooids evolutionally decreases the efficiency of hood intake.