Studies on the Embryology of Pycnopodia helianthoides (Brandt) Stimpson

Abstract

The Embryonic development of Pycnopodia helianthoides, the 20-rayed sea star, which has a small egg (120j-t), an indirect form of development, and larval metamorphosis, has not been previously reported in detail. Mortensen (1921) was able to rear only the early gastrula. No other references to the development of Pycnopodia have been found. Species of other multi-rayed sea stars with a yolky egg (and in consequence a more direct form of development) are much better known, e.g., Solaster endeca (Gemmill, 1912), Leptasterias hexactis (Osterud, 1918), and Crossaster papposus (Gemmill, 1920).