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THE CHOROID RETE MIRABILE OF THE FISH EYE. II. DISTRIBUTION AND RELATION TO THE PSEUDOBRANCH AND TO THE SWIMBLADDER RETE MIRABILE

1974; Marine Biological Laboratory (MBL); Volume: 146; Issue: 1 Linguagem: Inglês

10.2307/1540403

1939-8697

JONATHAN B. WITTERBERG, Richard L. Haedrich,

Ichthyology and Marine Biology

The choroid rete mirabile is a vascular counter-current organ located behind the retina of the eye and responsible in part for the maintenance of a high partial pressure of oxygen there. It is absent in cyclostomes, elasmobranchs, and all living non-teleost bony fishes with the exception of the holostean, Amia calva. The choroid rete is found widely distributed among teleosts and is nearly always present in the Acanthopterygii, which comprise the great majority of living forms. The ability to do without a choroid rete typifies families or orders, but is a character of limited phyletic usefulness. There seems little correlation between habitat and presence or absence of the choroid rete. The choroid rete and the rete mirabile of the swimbladder occur independently. This does not seem to be true for the choroid rete and the pseudobranch, Since almost all fishes which have a choroid rete also have a pseudobranch. Arterial blood comes to the choroid rete mirabile by way of the pseudobranch, and those instances in which the latter is lost offer an occasion for deductions about its function. We argue that the pseudobranch acts to modify the incoming arterial blood in such a way that the choroid rete may concentrate oxygen without simultaneously concentrating carbon dioxide, which when hydrated becomes a strong acid.