Histology of the Posterior Chamber of the Swimbladder of Argentina

Argentina was the first genus among the salmonoid fishes in which the swimbladder was reported to lack an open communication with the oesophagus, typical for the suborder Salmonoidei 1,2 . This has since been found to apply also to the families Microstomidae and Opisthoproctidae 3 . A more detailed description of the structure of the swim-bladder of Argentina silus 4 revealed the occurrence of a large number of flat bundles of blood vessels, which constitute a counter-current system. The name micro-retia mirabilia 3 has been established for this type of rete mirabile. In Argentina a gas gland tissue was also detected 4 , being in contact with capillary loops from the micro-retia. From these findings it was concluded that the swimbladder of Argentina silus has a capacity for gas secretion comparable to the swimbladder with a rete mirabile of the compact type.