Andrea Frommel

Histology offers insight into the inner workings of organisms, sometimes revealing bizarre and beautiful structures. This is a 1 micrometer-thin section through the gills of a larval Arapaima gigas. At home in the Amazon, this giant fish is an obligate air breather—an adaptation to seasonal hypoxia. Its larvae, however, hatch as water breathers. This picture is part of a study on the modifications of the gills and swim bladder throughout their development from water to air breathing.