Buenos Aires Tetra reveals its colours

Photographing fish in full-spectrum colour is incredibly difficult as they rarely stay still long enough for changing of filters, and their colours often change rapidly after death, or even when they are anaesthetised. We found one of our >6 year old pet Buenos Aires tetras (Hyphessobrycon anisitsi) on its last legs on the floor of our aquarium, seemingly unable to move but otherwise looking healthy and alert (for its age!) So I took this rare opportunity to quickly photograph the poor thing in UV while it was held in an isolation tank to stop it getting bullied by its friends.

Buenos Aires Tetra (Hyphessobrycon anisitsi) photographed in human and ultraviolet fish-vision
Buenos Aires Tetra (Hyphessobrycon anisitsi) photographed in human and ultraviolet fish-vision

The top-left image shows normal human vision, the top right shows camera UV vision (vG, vB, and uR in place of RGB). The bottom left shows the tetra in guppy LWS MWS SWS2 vision, and the bottom right shows guppy MWS SWS2 SWS1. These false-colour images highlight the amazing ultraviolet reflectance in the iridescent scales, the orange fins, and the yellow spinal band. Even though this fish has possibly been selectively bred by humans for tens on generations its has retained these amazing ultraviolet colours that are invisible to us, but probably important for sexual selection in this species.

The image was taken with a full-spectrum Samsung NX1000, with Nikkor EL 80mm lens and the Baader Venus-U filter and Baader UV/IR cut filters. Lighting was from an Iwasaki eyeColor arc lamp (UV-modified), to simulate natural D65 lighting conditions. There was some eye movement between the UV and visible shots, so the UV colours around the eyes aren’t natural. As with most images here, the linear cone-catch images have been square-root transformed for viewing on non-linear displays.


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