1 Essentially a vestigial gill slit located between the mandibular and hyoid arches in adult sharks, rays, and some primitive bony fish, and visible as an opening behind the eye.
2 One of the pores on the body of an insect at which the tracheae open to the outside. Spiracles are found on the thoracic and abdominal segments, and usually have some mechanism to close them.
Users without a subscription are not able to see the full content. Please,
or login to access all content.