Spanish dancer
The Spanish dancer (Hexabranchus sanguineus) is a large tropical nudibranch that swims by undulating its broad red-and-white mantle.
Nudibranch: A shell-less marine gastropod mollusk with exposed gills or other external respiratory structures. The Spanish dancer is one of the largest and most mobile nudibranchs.
Mollusca: A large animal phylum that includes snails, clams, cephalopods, and their relatives. The Spanish dancer is a mollusk despite its slug-like, shell-less appearance.
Coral reef: A marine ecosystem built largely by reef-forming corals and associated organisms. The Spanish dancer is commonly encountered in tropical reef habitats.
Sea hare: A large marine gastropod in the order Aplysiida, often with ear-like rhinophores and reduced shells. Sea hares are another conspicuous shell-reduced gastropod, but belong to a different lineage.
Nudibranch swimming: Swimming behavior in nudibranchs, produced by body flexion, mantle movements, or rhythmic appendage strokes. The Spanish dancer is a classic example, propelling itself with waves across its mantle.
Locomotion in nudibranchs: The ways nudibranchs move, including crawling on a muscular foot and swimming in some species. The Spanish dancer’s swimming is an unusual alternative to the crawling typical of nudibranchs.
Gastropoda: The mollusk class containing snails, slugs, limpets, and related animals. Its body plan and evolutionary relationships place it among gastropods.
Marine biodiversity: The variety of life, genes, and ecosystems found in oceans and other marine environments. Its specialized form and ecology contribute to the diversity of reef animals.
Sea butterfly: A free-swimming pelagic gastropod, usually a small pteropod with wing-like parapodia. Both names evoke swimming displays, but sea butterflies swim in open water with different anatomy.
Nocturnality: An activity pattern in which an animal is mainly active during the night. The Spanish dancer is often observed moving and feeding after dark.