actino-, actin-, actini-, -actinal, actis- +
(Greek: ray [as of light] or like a ray in form; radiance, radiation; a radiating or tentacled structure)
Nearly all living bony fishes are actinopterygians.
2. Treatment of a disease with rays of light; especially actinic or photochemically active rays, X-rays, radium, and other radio-chemicals.
2. Slender, horny, flexible, unsegmented fibrils which strengthen the embryonic fin fold 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.
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.