## r-w

### r

- radial canal n. The branch of the water vascular system connecting all the tube feet.
- radial symmetry n. Symmetrical about an axis that runs from the oral surface where the mouth is to the side opposite the mouth. Cnidarians have radial symmetry. Echinoderms are bilateral animals that have a 5-part radial symmetry as adults.
- radula n. A feeding organ of molluscs that contains teeth like structures for scraping food off surfaces and drawing food into the mouth.
- recombinant dna n. DNA which has been altered by joining genetic material from two different sources, usually involving putting a gene from one organism into the genome of a different organism, generally of a different species.
- remotely operated vehicle n. Typically aquatic, powered by a cable connected to a power source most commonly on a mothership.

### s

- salp n. Phylum Chordata, Class Thaliacea, Order Salpida. A type of boneless chordate that lives in the open ocean and can form massive chains of hermaphroditic individuals.
- scale worm n. Phylum Annelida, Class Polychaeta. A type of marine bristle worm that can sometimes live out its life in the underarms of sea stars.
- scorpion n. Arthropod in the class Arachnida, order Scorpiones. Scorpions are predatory with eight legs, grasping claws and a recurved tail with a venomous stinger.
- sea cucumber n. Phylum Echinodermata, Class Holothuroidea. A group of echinoderms that are soft and leathery, have elongated bodies, and feed by filtering detritus from the water column and/or vacuuming the seafloor.
- sea scorpion n. Phylum Arthropoda, Subphylum Chelicerata, Class Meristomata, Order Eurypteridae A type of vicious, extinct marine arthropod related to horseshoe crabs that reached sizes up to 10 feet (about 3 m) in length and could make short sojourns onto land.
- sea star n. Phylum Echinodermata, Class Asteroidea. A group of active predatory echinoderms arranged with a five-part symmetry.
- sea urchin n. Phylum Echinodermata, Class Echinoidea. A group of grazing or burrowing echinoderms typically covered with long sharp spines.
- setae n. Bristles on the segments in annelids. They are used to get purchase on the substrate to help movement.
- shell n. A structure in molluscs composed of calcium carbonate secreted by the mantle of the animal, which protects the occupant or similarly functional structures in other groups.
- sieve plate n. A structure in echinoderms through which water can flow in either direction between the water vascular system and the surrounding sea. Also known as a madreporite.
- siphuncle n. A strip of tissue running between the compartments of a cephalopod's shell that helps the animal achieve neutral buoyancy.
- skin gills n. Small finger-like projections from the body wall of the echinoderms that help in ridding the animal of waste and in absorbing oxygen. Also called papulas.
- spaghetti worm n. Phylum Annelida, Class Polychaeta, Order Terbellidae A type of tube-dwelling worm that lives in a mucus-lined burrow in the mud and extends its tentacles in all directions over the surface. See Terrebellid.
- spawn v. To release offspring or gametes. Can also be used as a noun.
- spicules n. A needlelike structure made of silica or calcium carbonate that, in large numbers, makes up the supporting framework of various sponges.
- spider n. Phylum Arthropod, Class Arachnida. Spiders are carnivores with eight legs and venomous fangs.
- sponges n. Phylum Porifera. A group of organisms at the base of the animal kingdom, characterized by a cellular level of organization and flagellated cells that capture tiny microscopic food the size of bacteria.
- stereo senses n. Paired senses that provide information about distance as well as direction.
- stomphia n. Phylum Cnidaria, Class Anthozoa, Order Actiniaria. A type of sea anemone found on the northwest coast of the United States that can thrust itself off submerged rocks and swing its body away from advancing predators.
- syrinx aruanus n. Phylum Mollusca, Class Gastropoda. A shelled mollusc that is believed to create the world's largest gastropod shell.

### t

- tapeworm n. Phylum Platyhelminthes, Class Cestoidea, Subclass Cestoda. A group of parasitic flatworms whose segmented bodies lack digestive organs and are capable of producing extreme numbers of offspring.
- taxonomist n. A type of biologist concerned with naming and classifying the diverse forms of life and deciphering their relationships.
- terrebellid n. Phylum Annelida, Class Polychaeta, Order Terbellidae A type of tube-dwelling worm that lives in a mucus-lined burrow in the mud and extends its tentacles in all directions over the surface. See spaghetti worm.
- tetrapod n. A four-limbed vertebrate, such as an amphibian, reptile, bird, or mammal.
- tick n. Phylum Arthropod, Class Arachnida. Ticks are ectoparasites living on the blood of vertebrates.
- tissue n. An integrated group of cells with a common structure and function.
- torque n. The force that produces or tends to produce rotation.
- toxin n. A poison produced by a living organism.
- trace fossil n. An imprint of the trackway from an animal long gone that can include the animal's feeding marks, burrows, and feces, as well.
- trilobite n. Phylum Arthropoda, Class Trilobita. A group of extremely prolific arthropods that went extinct 250 million years ago.
- tube feet n. Tubular extensions of the internal watervascular system of echinoderms that aid in locomotion, respiration, and grasping.
- tunicate n. Phylum Chordata, Subphylum Urochordata. A group of boneless chordates whose members begin life as tailed larva and often settle to a sedentary existence devoted to filtering seawater for a living.

### v

- vasculature n. Tissue consisting of cells joined to form tubes for transporting fluids through a body.
- velvet worm n. Phylum Onychophora. A type of caterpillar-like animal, closely related to arthropods, that has many soft legs and velvety skin.
- vertebrate n. Phylum Chordata, Subphylum Vertebrata The largest group of Chordates including fishes, amphibians, reptiles, and mammals.

### w

- wiwaxia n. An extinct animal that lived during the Cambrian Explosion, believed to be related to today's molluscs.