ABSTRACT
Growth bands have been found in the vertebral arm ossicles of many brittlestars. Although the periodicity of these bands is not known, they are thought to be age related. Experiments were carried out to determine whether these bands could be used as biological markers in population growth and partial predation studies. Individual Ophiura sarsi and Microphiopholis gracillima incubated for 12 h in 500 ppm calcein in natural seawater incorporated a fluorescent mark onto the surface of their vertebral arm ossicles. The position of the fluorescent mark relative to subsequently deposited growth rings can be used to verify band number to age relationships. Microscopic observations of growth rings in partially predated arms indicate that the number of rings on ossicles in the regenerated portion was invariably smaller than on the non-regenerated ossicles. If the periodicity of growth bands can be quantified, growth band analysis can provide a method of quantifying the frequency of arm cropping and regeneration rate, especially when predation scars are not readily visible. In situ experiments with calcien-labeled, regenerating Microphiopholis gracillima indicated that growth band deposition rate is highly variable within a population, with an average band increment rate of 1 band per year and a range of 0 to 4 bands per year.
