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Most bony fishes are covered with the cycloid scales of salmon and carp, or the ctenoid scales of perch, or the ganoid scales of sturgeons and gars. Cartilaginous fishes (sharks and rays) are covered with placoid scales.
Reptile scale types include: cycloid, granular (which appear bumpy), and keeled (which have a center ridge). Scales usually vary in size, the stouter, larger scales cover parts that are often exposed to physical stress (usually the feet, tail and head), while scales are small around the joints for flexibility.
Ganoid scales are flat, basal-looking scales. Derived from placoid scales, they have a thick coat of enamel, but without the underlying layer of dentin. These scales cover the fish's body with little overlapping. They are typical of gar and bichirs. Cycloid scales are small, oval-shaped scales with growth rings like the rings of a tree. They ...
The teleost scales are also then divided into two subgroups which are the cycloid scales, and the ctenoid scales. All these scales have a base of bone that they all originate from, the only difference is that the teleost scales only have one layer of bone.
placoid scales Teeth-like scales found in sharks and rays. posterior Towards the hind end of the fish. postorbital Behind the eye. precaudal Anterior to the tail portion. premaxillaries Two bones forming the front portion of the upper jaw. preocular spine A spine positioned above and in front of the eye. preopercle, preoperculum
Placoid Scale. Super Smooth scales (dermal denticles) coat the skin of sharks, rays, and cartilaginous fishes due to the absence of dermal bone. These scales are present in the dermis, which has fibrous connective tissue components, and project through the epidermis, which contains secretory cells and stratified epidermal cells, to the surface.
One of the distinguishing characteristics of this class is that the organisms have a skeleton at least partially made of bone. Another characteristic being, this class typically has cycloid or ctenoid scales in comparison to pointed placoid scales. These scales are distinguished by their bony makeup and the protective layer of mucous covering ...
Saxatilia differs from Crenicichla (subgenus Crenicichla) by the presence (or absence) of an eye spot on the caudal fin and by cycloid (vs. ctenoid) scales on the cheeks and chest area. Saxatilia differs from Crenicichla (subgenus Batrachops) by the absence of a reticulate colour pattern on the sides of the body.