The animal phylum known as cnidaria includes an abundant and colorful variety of anenomes, jellyfish, corals and hydroids—all categorized as having tentacles with stinging cells for defense and capturing prey.

It turns out that across the life stages of even just one species of jellyfish, tentacles can present a great number of functional and anatomical differences. In “Structural and Developmental Disparity in the Tentacles of the Moon Jellyfish Aurelia sp.1,” researchers examined two types of tentacles of the moon jellyfish: the oral tentacles of the polyp (post-larval stage) and the marginal tentacles of the medusa (juvenile to mature stage). They observed marked differences in musculature, cell types, cellular distribution and growth patterns that may have evolved from distinct adaptive requirements, such as for feeding or movement. The complexity of these differences call to question the current textbook assumption that all cnidarian tentacles evolved from a similar point of origin.

The research was supported by the NASA Astrobiology Institute – Foundations of Complex Life: Evolution, Preservation and Detection on Earth and Beyond.