GROWTH AND REPAIR OF SPINES IN THE SEA URCHIN STRONGYLOCENTROTUS PURPURATUS (STIMPSON)

Open Access
Publisher Website
Google Scholar
Abstract
Spines are composed to calcite crystals arranged in a 3-dimensional lattice and, in cross-section, show large crystals arranged in cycles separated by a fine meshwork. Previous work has suggested that cycles might be related to age in years. Evidence is presented for a natural population which indicates that there is a positive correlation between animal size and number of cycles in spines. Longitudinal sections show that cycles always terminate distally at sharp discontinuities and, for all seasons, large crystals are present on the outside of the spine. The hypothesis is set-up that cycles represent not age in years but rather the number of times a spine was broken and regenerated. This is shown to be correct. Broken spines of small green animals produced purple tips when the urchins were exposed to light and white tips when the animals were kept in darkness. The appearance of the purple-tipped spines was similar to the green-cored spines of large animals in the field. In such spines, the green core was separated from the purple portion by a cycle of large calcite crystals. This suggested that they were formed as a result of regeneration under light conditions and that the outside calcite crystals of the small green spines were covered-over during regeneration and growth. A 2nd experiment demonstrated that when a spine tip was removed and the spine allowed to regenerate a new tip, a new cycle was added. From observed morphology and experimental evidence, it appears that growth of spines requires a very precise resportion as well as deposition of calcite.

This publication has 3 references indexed in Scilit: