Spiracle

A small opening behind the eye that admits water to the gills in many fishes, especially sharks and rays.

Buccal pumping: A method of moving water over fish gills by expanding and compressing the mouth and throat cavity. Water drawn through the spiracle can join the flow driven by mouth and throat movements.
Fish: Aquatic vertebrates with gills, fins, and, in most species, a streamlined body. Spiracles are anatomical openings found in several fish lineages.
Benthic fish: A fish that lives on or near the bottom of a body of water. A spiracle can draw water from above when the fish lies against the substrate.
Shark: A cartilaginous fish with a skeleton made primarily of cartilage. Many sharks have spiracles behind the eyes that supply water to the gills.
Pharynx: A throat region connecting the mouth cavity to the openings and passages of the respiratory and digestive systems. Water entering the spiracle passes toward the pharynx and gill chambers.
Gill: A respiratory organ that extracts dissolved oxygen from water and releases carbon dioxide. The spiracle is an inlet associated with water flow to the gills.
Stingray: A flat-bodied cartilaginous fish with a long tail and enlarged pectoral fins. Stingrays use spiracles to take in water while resting on the seabed.
Ray: A cartilaginous fish with a flattened body and enlarged pectoral fins. Spiracles are especially prominent in many rays because they breathe while resting on the seafloor.
Gill arch: A skeletal support in fishes that bears gill filaments and associated structures. Gill arches support the respiratory surfaces supplied by water entering the spiracle.
Eye: A sensory organ that detects light and forms visual information. The spiracle's position is defined by its location behind the eye.

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