Phylum Echinodermata “spiny skinned”

5 Classes Class Asteroidea Class Ophiuroidea Class Echinoidea sea stars Class Ophiuroidea brittle stars Class Echinoidea sea urchins Class Holothuroidea sea cucumbers Class Crinoidea feather stars, sea lilies

What characteristics do you think they have in common?

Key Characteristics “spiny skin” Not always sharp, sometimes bumpy White spotted sea cucumber Pencil urchin Stubborn sea cucumber

Key Characteristics pentamerous radial symmetry (based on five parts) Multiples of five Red Velvet Star Most obvious in the sea star, but if you fold the arms of a sea star you will see the shape of a sea urchin, elongate that shape and you have a sea cucumber Skeletons of sand dollar’s, clearly see 5 parts

Key Characteristics Calcareous endoskeleton (internal skeleton) “test” = sea urchin’s skeleton Sea urchin test showing bumps where spines attach

Key Characteristics water vascular system network of water-filled canals tube feet for attachment, locomotion, and stimuli

Tube Feet Sea star tube feet, sensing and moving in the environment Sea cucumber tube feet modified to filter feed on detritus in the sand. Sea urchin tube feet can catch drifting algae and forward it to the mouth on the underside of the body.

Additional Physical Characteristics Complete Gut Radial Nervous system (non-centralized) Plump sea cucumber Collector urchin Spiny Brittle Star

Behavior Characteristics Reproduction Usually with separate sexes (spawning) Ability to regenerate arms and asexual reproduction Sea cucumber raised its head to spawn into the current.

Regeneration in a Sea Star

Feeding Behaviors Varies between groups Predators Herbivores Scavengers Filter Feeders Sea cumbers filter feed or sift through detritus with tentacles. Sea urchins graze on algae using their sharp teeth “Aristotle’s Lantern” located on their underside.

Sea Star Feeding Sea stars are predators. Able to open shells with strong tube feet and can evert their stomach into the shell of another to liquify meat and then digest. (white is the stomach in a mussel).