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Comparações morfológicas e histoquímicas da bexiga natatória de peixes teleósteos de respiração aquática e respiração aérea (*) * — Pesquisa financiada pelo CNPq e NSF Grant n.° BNS75 — 10457 AO 1

Summary

Morphological and histochemical comparisons were made between the swim-bladders of Hoplerythrinus unitaenitus (the "jeju"), a facultatively air breathing eritrinid fish, and Osteoglossum bicirrhosum (the "aruanã"), an osteoglossid fish which is restricted to aquatic respiration. In the "jeju", the swim-bladder has a respiratory function, while in the "aruanã" it is an hydrostatic organ. Both are physostomes, and the swim-bladder is divided into two chambers whose walls are made up of three enveloping membranes or mantles. There are morphological characteristics peculiar to each species, especially in the form of the mantles. In the "jeju" the mantle forms folds, which increase the surface area. The mantle also has a rich plexus of sub-epithelial capillaries and lateral muscular pads in this species. The histochemical tests show that the swim-bladder of the "jeju" contains mucopolysaccharides, reducing substances, lipids, cholesterol and the related compounds: calciferol, ferric ions, and proteins. There are also elastic fibers which are present in greater quantity in the anterior portion of the posterior chamber. With the exception of the elastic fibers, these components are usually located in the epithelium, the stripe itself, and near the blood vessels, especially near the muscular pads. In the "arunã" the tests for these substances were negative, except for a few which were discretely positive in the epithelium and in the presence of elastic fibers. It is suggested that the compounds found in the "jeju" have a function in the respiration carried out by the swim-bladder.

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