What is the function of Placoid scales?
They provide protection from the environment and from predators. Sharks have placoid scales, bony, spiny projections with an enamel-like covering. These scales have the same structure as their teeth, and are also referred to as dermal denticles (dermal=skin, denticle=teeth).
What has Placoid scale?
Placoid scales are found in sharks and rays, and can vary greatly in external appearance. Unlike the scales of bony fishes, placoid scales do not increase in size as the fish grows, instead new scales are added between older scales. Placoid scales are often referred to as denticles.
What is meaning of Placoid scales?
Placoid scales (or denticles) are spiny, toothlike projections seen only in cartilaginous fishes. Ganoid scales, sometimes considered a modification of the placoid type, are chiefly bony but are covered with an enamel-like substance called ganoin.
What is a Placoid in biology?
adj. 1. ( Biology) platelike or flattened. 2. ( Zoology) (of the scales of sharks and other elasmobranchs) toothlike; composed of dentine with an enamel tip and basal pulp cavity.
Which class has Placoid scales?
cartilaginous fishes
Placoid (pointed, tooth-shaped) scales are found in the cartilaginous fishes: sharks, rays.
What is the function of the Claspers?
Claspers in chondrichthyans are specialized elongations on the posterior side of male pelvic fins that are used for sperm transfer during copulation.
What is difference between Placoid and cycloid scales?
The key difference between placoid and cycloid scales is that placoid scales are triangular, rough structures present in cartilaginous fish, while cycloid scales are round, flexible structures present in bony fish. The exoskeletal covering of vertebrates is made of two types of scales. They are epidermal and dermal.
Where is found in Placoid scales?
Placoid (pointed, tooth-shaped) scales are found in the cartilaginous fishes: sharks, rays. They are also called dermal denticles.
How do Placoid scales grow?
Placoid scales are packed tightly together, are supported by spines, and grow with their tips facing backward and laying flat.
What is claspers in biology?
Definition of clasper : a male copulatory structure: a : one of a pair of external anal processes of an insect that are used to grasp a female. b : one of a pair of organs that are extensions of the pelvic fins of cartilaginous fishes.
What is the difference between Placoid and Ctenoid scale?
is that placoid is platelike; having irregular, platelike, bony scales, often bearing spines; pertaining to the placoids while ctenoid is having a toothed margin, usually fish scales.
What is the difference between Placoid and Ctenoid scales?
Placoid is plate-like having irregular, platelike, bony scales, often bearing spines; pertaining to the placoids while ctenoid is having a toothed margin, usually fish scales. Placoid is any fish having placoid scales, such as the sharks while ctenoid is a ctenoidean.