Elasmoid scale

Scaling of the bitterling ( Rhodeus amarus ). The greenish flank stripe is of epidermal origin, the remaining pigmentation is part of the dermis.

Elasmoid scales (from Greek elasmos "plate") are the scales of the real bony fish (Teleostei).

They are plate-shaped bone formations that are covered by the epidermis (upper skin). Typically, they are tiled, which provides mechanical protection without hindering the fish's growth and mobility. The scales grow with the seasons and their arrangement and number remain with the fish for life. They can therefore be used to determine the type and age. If lost, they will be replaced.

construction

Elasmoid scales are formed in pocket-like spaces in the connective tissue (stratum laxum) of the dermis , the so-called scaly pockets. They are made up of two layers with different fine structures and lime content. The upper layer consists of bone tissue with deposits of hydroxyapatite . Underneath is a fibrillar plate made of orthogonally aligned collagen fibers that remains partially or completely uncalcified.

Ganoid scales on the left , round scales in the middle, comb scales on the right.

to form

There are two basic forms of elasmoid scales. The more original round scale (cycloid scale) and the phylogenetically derived comb scale (ctenoid scale). Round scales are almost circular and smooth-edged, comb scales, on the other hand, are toothed like a comb on the rear edge. Both forms form concentric growth rings (anulli).

A number of species have both types of scales, for example the flounder has round scales on the “blind side” and comb scales on the “eye side”.

Dandruff formula

The number and characteristics of the scales are of great importance in taxonomy and are recorded in the scale formula. It indicates how many scales are in the side line row (SL), the number of scales in a middle longitudinal row (mLR), the number of scales in a transverse row (QR).

Example of the red crested earth eater ( Geophagus steindachneri ):

Scale formula: mLR 28-30; SL 18-21.

The following can also be specified: the number of scales between the lateral line and the dorsal fin, between the lateral line and the abdominal profile, the lateral line and the base of the ventral fin and around the caudal stalk.

Dandruff formula: 4.5 / 25-28 / 3.5; 2.5 / 12

means: 4.5 scales between the lateral line and the dorsal fin, 25-28 in the lateral line row, 3.5 between the lateral line and the abdominal profile, 2.5 between the lateral line and the base of the ventral fin and 12 scales around the caudal stalk.

literature

Kurt Fiedler: Textbook of special zoology . Volume 2: Vertebrates. Part 2: fish. Gustav Fischer Verlag, Jena 1991, ISBN 3-334-00338-8 .
Manfred Klinkhardt: Elasmoid scale. In: Claus Schaefer, Torsten Schröer (Hrsg.): The large lexicon of aquaristics. 2 volumes. Eugen Ulmer, Stuttgart 2004, ISBN 3-8001-7497-9 , p. 349.

Individual evidence

↑ Günther Sterba : Freshwater fish of the world. 2nd Edition. Urania, Leipzig / Jena / Berlin 1990, ISBN 3-332-00109-4 , p. 15.
↑ Melanie Stiassny, Guy Teugels, Carl D. Hopkins: The Fresh and Brackish Water Fishes of Lower Guinea, West-Central Africa. Volume 2, Paris 2007, ISBN 978-90-74752-21-3 , p. 25.

[1] Günther Sterba : Freshwater fish of the world. 2nd Edition. Urania, Leipzig / Jena / Berlin 1990, ISBN 3-332-00109-4 , p. 15.

[2] Melanie Stiassny, Guy Teugels, Carl D. Hopkins: The Fresh and Brackish Water Fishes of Lower Guinea, West-Central Africa. Volume 2, Paris 2007, ISBN 978-90-74752-21-3 , p. 25.