Scutum oculare
blue : Präoculare
green : Postocularia
red : Temporal
The scutum oculare (short oculare , lat. Plural ocularia ), also ocular scale or -shield, are groups of horny scales in squamata , which are arranged around the eye . All oculars together form the circumorbital ring and are therefore also referred to as circumorbitalia . In the snake system , the number, shape, size and formation of the ocularia - as well as the other head shields - are an important determinant .
The name of the respective group is a compound from the term "Oculus" for the eye and the specific positional relationship:
- The vorocularia are directly in front of the eye.
- The postocularia are just behind the eye.
- The supraocularia lie above the eye. They can be greatly enlarged or fragmented into a number of small scales. In many snakes they form characteristic horns or other structures.
- The subocularia lie below the eyes and abut the supralabialia in many snakes .
glasses
Legend
| ag - Anterior chin shields f - Frontals in - Internasals l - Loreale la - Supralabialia la ' - Sublabialia m - Mental n - Nasalia p - Parietalia | pf - Praefrontalia pg - Posterior chin shields pro - Praeoculare pso - Praesuboculare pto - Postocularia r - Rostrale so - Supraoculare t - Anterior and posterior temporalia v - First ventral |
The outer part of the eye, the cornea or cornea, is covered in all snakes, many lizards and some fish by a rigid, transparent scale, the so-called glasses . This membrane is formed during embryonic development from the fusion of the upper and lower eyelids and protects the eye from drying out and mechanical stress (especially in the case of forms living underground). Between the glasses and the cornea there is a space filled with tear fluid (subspectacular space), which is connected to the throat via a channel .
With the entire keratinized portion of the skin, the cornea and glasses are also skinned . The moult is preceded by the moulting cells between the old and new skin, which in snakes leads to a bluish-cloudy discoloration of the eyes. A few days before the moult begins, the eyes will clear again. The glasses (transparent referred to as "tertiary glasses" in distinction to the "primary glasses" integument on the cornea) of the cyclostomes and amphibians larvae as well as the "secondary glasses" many fish (outer, stationary corneal layer) is not are homologous to her .
It can happen that due to disruption of the moulting, remnants of the old glasses remain ("retained glasses"). These must not be removed, but must be carefully removed by rinsing, otherwise irreparable injuries to the eye can occur.
literature
- Roland Bauchot (Ed.): Snakes . Bechtermünz Verlag, Augsburg 1998, ISBN 3-8289-1501-9 .
- David Mallow, David Ludwig, Göran Nilson: True Vipers. Natural History and Toxicology of Old World Vipers. Krieger Publishing Company, Malabar, Florida 2003, ISBN 0-89464-877-2 , pp. 150-159.
Individual evidence
- ↑ a b Thomas Steidl, Michael Hartmann: Skin diseases in reptiles. In: Small Animal Medicine. No. 4/2012, pp. 180-185.
- ↑ Klaus Kabisch: Dictionary of Herpetology. Gustav Fischer Verlag , Jena 1990, pp. 58 and 75.