Il Discus (Symphysodon Aequifasciatus)
- Creato: Venerdì, 22 Aprile 2011 07:17
- Scritto da Claudio Visalli (Claudio)
- Visite: 16912
Discus secretions to feed brood fry – part one
Do Discus Pairs Really Form Secretions? If everything is proceeding normally, the discus brood will, after their three to four day yolk sac phase, begin moving towards the sides of their parent’s bodies along the shortest route possible. The free swimming fry frequently concentrate themselves on the upper half of the body, especially around the base of the dorsal fin. The common belief is that the adult fish which alternate in leading the young fry, produce a secretion (“Discus milk”) upon which the young feed and which serves as their first food.
Two scientists have now explained what the young fry are really taking in. To explain this interesting function, examinations were conducted on the brooding parent fish as well as on sexually inactive discus fish, and also on the stomach contents of the larval discus fish.
Morphology of Fish Skin
To be able to properly understand and interpret the results of the examination, a basic introduction to the skin, which is the body covering of all fish, is presented here. The fish skin is composed of two separate layers; the external surface (epidermis), and the inner underlying skin (corium). Still further inwards is the tissue underlying the skin (sub cutis or hypodermis), and finally the body muscles. The last are composed of the cross banded muscle tissue, as well as their supplying capillaries and the nerves.
In the underlying skin of the discus, as is the case with most fish, the very small scales are anchored. Together with the stable underlying skin layer, they “armour” the fish and protect it from mechanical and other damage. The epidermis is composed of many cells arrayed over each other, the multi-layered epithelium. All layers arise from the lowest layer of cells, basal cell layer. Many varied glandular cells are in the epidermis. Some of these, the ellipsoidal, cup-shaped slime cells, discharge their secretion outwards. It disperses over the surface of the epidermis and makes it smooth and slippery. This slime layer is continually renewed; it protects the skin from colonization by fungi and bacteria, and it is also effective in restricting inflammation. Slime production by the cup-shaped cells is probably so retarded by the presence of toxic substances in the aquarium water, that it can resemble the symptoms of fresh water allergy.
Additionally, in the underlying skin layer beneath the scales, there occurs yet another unique characteristic of the skin; the dye cells called chromatophores. They contain very small pigmented bodies and they are responsible for the colouration and patterns of the fish. It is understandable that, during chemical damage to the skin (too high or too low a pH, fresh water allergy), the function of the chromatophores is also impaired so that the afflicted discus fish appear dark to black.
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Second part follows.
Special thanks to http://www.pds.ph administrator
By Horst W. Koehler “Diskus Brief” Sept. 1989 Translated by Paul Ceroke, Urbaira; reprinted in “Our Discus” N.A.D.S. Volume 4 Issue 2, 1990.
1. Bremer, e Walter H. U: Histologische, ultrastrukturelle e topochemische Untersuchungen zur Brutpflege von aequifasciatus Symphysodon Pellegrin 1903. Gegenbaurs morph. Jahrbuch Lipsia 132 (1986) 2, S. 183-194.
2. Bremer, e Walter H., U.: Wasfressen Junge Diskusbuntbarsche? Aquarien-Terrarien 1 / 1986, S. 14-17.
3. Sterba, G.: Aquarienkunde. Ulmer Eugen Verlag, Stoccarda, 1989 (Lizenzausgabe).
4. Schriftliche Mitteilungen Dott. Heinz von den Bremer e Vorn Verfasser 12.11.86 und 7.1.87.
Published: January 2006 Practical Fishkeeping Magazine
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