actino-, actin-, actini-, -actinal, actis- +

A fish of the taxonomic class Actinopterygii: An actinopterygian has fan-shaped fins supported by radiating spines or rays.

Nearly all living bony fishes are actinopterygians.

A subclass of bony fishes, often called ray-finned fish: Actinopterygii consist of many extinct groups and most living bony fishes with usually paired fins with broad bases.

The fishes of the Actinopterygii have ganoid scales, which are a type of scale consisting of dentine-covered bone with a thick outer layer of a substance similar to enamel.

A symbiotic association between certain plant roots and certain bacteria: Actinorrhizae are exemplified as "Frankia" strains (nitrogen-fixing root-nodule symbionts of many species of woody dicotyledonous plants), in which nitrogen fixation occurs within specialized root nodules.

In radiology, a former term for fluoroscopy or an X-ray machine: The obsolete word actinoscopy refers to the instrument that combines X-ray images on a fluorescent screen to enable direct observation.

A former term for radiostereoscopy: An actinosteroscopy is the simultaneous viewing of two radiographs (X-rays) made in slightly different projections.

Actinosteroscopy is usually performed with an instrument that reflects the image of one on each eye, allowing three-dimensional visualization of an object in relation to others.

The mouth of a radially symmetrical animal: The actinostome is the oral cavity of a coelenterate creature, such as the starfish.

The use of light rays for the treatment of skin diseases: Actinotherapeutics is used for treating cutaneous ailments by exposing the outer surface of the body to ultraviolet light.

The treatment of a disease with actinic rays: Actiontherapy is the medical attention and care of an ailment with rays of light or with photochemically active rays, X-rays, radium, and other radio-chemicals.

A term for radiation sickness: While reading her biology book, Annette came across the obsolete word actinotoxemia which meant an illness caused by exposure to electromagnetic radiation, which would also include the sunburn.

A crude poison derived from extracts of the tentacles of sea anemones: The actinotoxin, or venom, of the tentacles is a combination of toxins, including neurotoxins, that deactivate or paralyze its prey so it can transfer it to its mouth for digestion.

One of a group of threadlike (hairlike) fibers in the finfolds of fish larvae that eventually develop into fin rays: The actinotrichia are slender, horny, flexible, unsegmented fibrils which strengthen the embryonic finfold, or the unjointed horny rays at the edge of fins in many fish.

Actinotrichia are translucent, exhibit birefringence (double refraction) and are composed of a scleroprotein, called elastoidine.

The former name of the radioactive uranium isotope of mass 235: Actinouranium is now called uranium-235 and fissionable with slow neutrons.

Solitary or colonial coelenterates without any free-swimming medusa stage and with the coelenteron divided by mesenteries: The actinozoa include most of the common sea-anemones and corals.

Coelenterata consist of a rather large phylum of sedentary or free-swimming animals having a radially symmetrical sac-like body with a mouth at one end, usually surrounded by a ring of stinging tentacles.

The digestive cavity, known as the "coelenteron", has only this opening, but repeated budding may give rise to a colony in which all the body-cavities are connected with each other.

The body-wall is "diploblastic" that is made of two layers of cells, ectoderm and endoderm, with a gelatinous layer known as the "mesogloea" between them.

The individuals of a colony are known as "polyps" or "hydroids". They form the asexual sedentary generation which alternates with a free-swimming sexual phase known as the "medusa". The latter is a disc-shaped jelly-fish which breaks away from the parent colony and swims away. It produces gametes and after fertilization has taken place, a new polyp colony develops.

Included in the Coelenterata are corals and anemones in which the hydroid stage is dominant, jelly-fish in which the medusoid stage is dominant, and complex forms such as the "Portuguese Man-of-war" formed by a large floating colony of diverse polyps.

In zoology, pertaining to the Actinozoa: Jack wanted to find out more information about actinozoal life forms in the sea, including hydras, polyps, jellyfishes, and corals, for his term paper.

A saltwater organism: Such actinozoans include corals, sea anemones, and sea fans.