A BMI Key Vocabulary


Abdomen: The third main division of the body; behind the head and thorax.

Anterior: In front.

Apical: Part of any body structure that is farthest from the body.

Appendage: an external body part that protrudes from an organism's body, including antennae, legs, mouthparts, and parts of the tail. 

Basal: Pertaining to the part of any structure that is nearest to the body.

Burrower: Animal that uses a variety of structures designed for moving and burrowing into sand and silt, or building tubes within loose substrate.

Calcium carbonate: is a chemical compound, with the chemical formula CaCO3. It is a common substance found as limestone rock in all parts of the world, and is the main component of seashells, snails, and eggshell.

Carapace: The hardened part of some arthropods that spreads like a shield over several segments of the head and thorax.

Caudal: At or near the tail or hind parts of an animal

Caudal chamber: A chamber at the tail or hind part of an animal.

Caudal filament: Threadlike projection at the end of the abdomen, like a tail.

Cephalothorax:  the anterior major body section in arachnids and malacostracan crustaceans that includes the head (cephalon) and thorax.  The cephalon and thorax may be completely or partially fused.

Chaetae: a chitinous bristle or seta found on annelid worms, also frequently used to describe similar structures in other invertebrates.

Chitin:  is the main component of the exoskeletons of arthropods such as crustaceans (e.g. crabs, lobsters and shrimps) and insects. 

Chitinous: containing chitin.

Clinger: Animal that uses claws or hooks to cling to the surfaces or rocks, plants or other hard surfaces and often moves slowly along these surfaces.

Crawler: An animal, whose main means of locomotion is moving slowly along the bottom, usually has some type of hooks, claws or specially designed feet to help hold them to surfaces.

Detritus: Disintegrated or broken up mineral or organic material.

Dextral: The curvature of a gastropod shell where the opening is visible on the right when the spire is pointed up, sometimes referred to as "left-handed shell."

Distal: Near or toward the free end of any appendage; that part farthest from the body.

Dorsal: Pertaining to, or situated on the back or top, especially of the thorax and abdomen.

Elongate: Longer than wide

Elytra: Hard forewings that cover the abdomen and hind (flying) wings, found on adult beetles.

Embeddedness:  the extent to which cobble and boulders in a stream are buried in fine silt and sand. 

Exoskeleton: an external, supportive structure.

Filamentous gills:  Gills that are long and narrow.  Often occur in clusters.

Filament: a threadlike structure. 

Flagellum: A small fingerlike or whip-like projection.

Gastropod:  mollusks typically having a one-piece coiled shell

Gill: Any structure especially adapted for the exchange of dissolved gases between animal and a surrounding liquid.

Head:  The front (anterior) part of an organism, often the area where the brain and many sensory organs like eyes are located. 

Herbivores:  Plant eating.

Hermaphrodites: an animal or plant that has both male and female reproductive organs.

Hirudin: a naturally occurring peptide in the salivary glands of medicinal leeches that has a blood anticoagulant property

Jointed legs: Legs that have joints. 

Labium: Lower mouthpart of an arthropod, like a jaw or lip.

Labrum: Upper mouthpart of an arthropod consisting of a single usually hinged plate above the mandibles.

Larva: a distinct juvenile form some animals undergo before metamorphosis into adults.  The appearance is generally very different from the adult form, as a caterpillar’s form is different than the butterfly’s form.  This process is called "complete" metamorphosis, with the organism going through four life stages; embryo, larva, pupa and imago.

Lateral: Feature or marking located on the side of a body or other structure.

Laterally flattened: flattened from side-to-side

Ligament: a sheet or band of tough fibrous tissue that connects bones, cartilages or supports muscles or organs.

Ligula: Forming the ventral wall of an arthropod’s oral cavity.

Lobe: A rounded projection or protuberance.

Mandibles: The first pair of jaws in insects.

Mantle:  a part of the anatomy of molluscs, it is the dorsal body wall which covers the organs of digestion, reproduction and movement.  In many species of molluscs, the mantle secretes calcium carbonate and conchiolin, and creates the mollusc’s shell.

Maxillae: The second pair of jaws in insects.

Maxillipeds: Legs (or appendages) modified to serve as mouthparts

Metamorphous:  when an animal undergoes a marked change in form from immature larva to adult, as a caterpillar’s form is different than the butterfly’s form.

Molt: the process where an animal sheds its skin as it grows larger.

Nymphs/ naiads:  the immature form of some invertebrates, particularly insects, which undergoes gradual metamorphosis through a series of molts before the final molt results in an adult insect. This is called incomplete metamorphosis.  Unlike a larva, a nymph's overall form already resembles that of the adult and a nymph never enters a pupal stage.

Omnivore: an animal that eats a variety of plant and animal food. 

Operculate: an animal that has an operculum. 

Operculum: A lid or covering structure, like a door to an opening.

Palpal lobes: The grasping pinchers at the end of the Odonata lower jaw.

Parasite/ parasitic:  an organism that lives in or on another organism and does the host some harm.

Periphyton: Algae and associated organisms that live attached to underwater surfaces.

Posterior: Behind, opposite of anterior.

Proleg (protuberances): An unjointed appendage that serves for support locomotion or attachment.  They may have hooks but they are not jointed, and so lack the segments that true arthropod legs possess.

Pupa, pupal: inactive life stage of an insect’s development when it is undergoing transformation from larva and adult.  The pupal stage is found only in insects that undergo a complete metamorphosis, going through four life stages; embryo, larva, pupa and imago.

Rostrum: A beak or beak-like mouthpart.

Sclerite: A hardened area of an insect body wall, usually surrounded by softer membranes.

Scrapers: BMI feeding group that scrapes attached algae and microorganisms (periphyton) located on submerged underwater surfaces.

Segments: Distinct sections of a body.

Seta (pl. setae): Hair like projection.

Setae vs. cilia:  setae are stiff, bristly hairs, while cilia are flexible hair like structures. 

Shredders: BMI feeding group that consumes coarse organic matter like leaves

Sinistral: The curvature of a gastropod shell where the opening is seen on the left when the spire is pointed up, sometimes referred to as "left-handed shell."

Siphon:  In molluscs, siphons are long tube-like structures used for the exchange of water or air. 

Terrestrial: Living on the land, rather than in the air or water.  

Thorax: the middle region of the body of an arthropod between the head and the abdomen

Valves, as in bivalves:  A bivalve is a mollusk with two halves, or valves, that have a hinge between them and are opened using a large muscle inside the shell.  

Wingpad: Sheaths that protect wings as they develop on a nymph.



The Potomac Highlands Watershed School 

BMI Key Vocabulary

The BMI Key Vocabulary is just one component of the Potomac Highlands Watershed School's watershed science and society curriculum, and is best used when accessed from within an eSchool classroom.  If you reached this page via a direct web-link, you might consider going to the Potomac Highlands Watershed School and visiting an eSchool classroom to use this and other activities, review the literature in the bookshelf or, if you are a teacher, visit the "Teacher's" room and check out the lesson plans.