The Neotropical catfish family Loricariidae is a vertebrate success story about which we know little. With over 600 described species (and many additional undescribed) this family evolved entirely after the Cretaceous separation of South America from Africa and accounts for between 1 and 2% of all current vertebrate diversity. Unlike other speciose fish families, which usually exploit multiple trophic niches, virtually all loricariids are herbivorous and eat near the bottom of the food chain. Field collections and laboratory experiments suggest that some loricariid catfishes are even utilizing wood in their diet. This is the first and only documentation of wood eating (xylophagy) in the more than 25,000 species of bony fish. These observations alone justify undertaking more detailed studies of the nutritional physiological of loricariids. However, all cellulolytic organisms thus far cultured from loricariids are either aerobic or facultatively anaerobic and all loricariids that have been tested can breathe air as well as water. Thus, it is possible that loricariids are the only vertebrates to be digesting cellulose under aerobic conditions. Unfortunately, nothing is currently known about the gut environment of loricariids.

Cast net fishing for Hypostomus regani to be used in the experiments on the Mogi Guacu river, Pirassinunga, Sao Paulo State.

Diagram of the apparatus used to investigate air-breathing behavior and physiology of Hypostomus regani that were either fed or starved and either normoxic or hypoxic.