Ocular gill

The ocular gill gland or pseudobranch of bony fish is a glandular organ and rudimentary gill arch whose function is still largely unknown, but has a special role in the gas metabolism of the retina .

Morphologically it corresponds to the short half gill in the injection hole of the plate gill (Elasmobranchii) (sharks and rays), the spiracular gill and thus originally indicates the location of the injection hole channel of the bony fish, which is only present in the sturgeon , the sword sturgeon and the pike fish . In adult gars and the Bowfin the injection port is no longer consistently outward and became a narrow pit. In the real bony fish (Teleostei) this pit is no longer found either, but only the pseudobranch.

Covered pseudobranchia are covered by connective tissue and stored deep in the roof of the gill cavity against the base of the skull. In other real bony fish, the pseudobranch is on the inside of the gill cover . These free pseudobranchia, which macroscopically and microscopically hardly differ from real gills, are found in many herrings (Clupeidae), arm-finfish (Lophiiformes), pipefish (Syngnathidae), slimy fish (Blenniidae) and plaice (Pleuronectidae).

The pseudobranch is upstream of the capillary system of the eye. In adult real bony fish, it is only supplied with oxygen-saturated blood from the first branchial arch artery, which is then passed on to the eye. The pseudobranch is rich in carbonic anhydrases and causes exophthalmos ("googly eyes") in disorders .

literature

• Kurt Fiedler: Textbook of Special Zoology, Volume II, Part 2: Fish , Gustav Fischer Verlag Jena, 1991, ISBN 3-334-00339-6 .
• Wilfried Westheide & Reinhard Rieger: Special Zoology Part 2: Vertebrae and Skull Animals , 1st edition, Spectrum Akademischer Verlag Heidelberg • Berlin, 2004, ISBN 3-8274-0307-3 .