The integument of the nonamphibious goby Gobionellus oceanicus: Its functional morphology and respiratory capacity

Facultative air‐breathing fish can exchange respiratory gases using an air‐breathing organ (ABO), such as the oral cavity of the integument, during environmental hypoxia. The goby Gobionellus oceanicus inhabits areas subject to environmental hypoxia; however, its ABO is unknown. To investigate the respiratory potential of G. oceanicus, the gill and integument surface area, diffusion capacity, and their diffusion barrier thickness were measured. Our results show that although gill surface area is smaller than observed in other facultative air‐breathing fish, but it has all features necessary to perform aquatic gas exchange. Additionally the integument of the palate has a short diffusion barrier thickness and a large calculated O2‐diffusion capacity suggesting that it functions as the ABO. In this figure it is might be observed the relevance of the palate integument for air breathing expressed by the ratio between surface area and body mass (A), surface area and volume (B), anatomical diffusion factor (C) and O2 diffusion capacity (D), when compared to other integument parts.