On September 25 2019, a Reddit user shared the following post (“Inside the gills of a whale shark”) to Reddit’s r/woahdude, and the post with an identical title was subsequently shared to Imgur:
On Reddit, the purported image of whale shark gills in action was heavily upvoted; the Imgur post of the same name was viewed nearly half a million times in eight hours. Neither post included a source or additional information about the image or its veracity. A version of the photograph shared to r/DamnThatsInteresting in late 2018 was not nearly as popular.
As is often the case with high-engagement Reddit image posts, the original poster appeared to be a karma farmer, regularly sharing images to various subreddits but rarely engaging in discussion about those posts. Karma farming behavior often suggests that that poster is invested in garnering upvotes, and the lack of commenting indicates that the user is not particularly invested in the veracity of the content they share. That said, karma farming alone is not proof positive that an image is of dubious origin or description.
An image from 2010 uploaded by a Flickr user showed whale shark gills, but in less detail that the Reddit and Imgur posts. That image was taken in waters off Mexico, as was one whale shark gill-specific photograph in a much larger set published in 2011.
Sharks (including whale sharks) have gills, but unlike many other fish, their gills are not covered by a protective flap called an operculum. The structure of the gill includes cartilage in the form of gill rakers, and gill filaments through which oxygen is absorbed:
Sharks, like other fish, use their gills to breathe. Water flows through the gills and out the gill slits while the gill filaments extract oxygen from the water. The oxygen is absorbed by the blood that flows through the gill filaments. Gill rakers, cartilaginous projections on the gill support structure, protect the delicate gill filaments from particles in the water that might damage them. The flow of water through the gills is essential for sharks to breathe, otherwise they will die of lack of oxygen – drowning.
A March 2018 blog post about underwater photographer Simone Caprodocci credited the Dubai-based underwater photographer with the image:
Underwater photographer Simone Caprodossi has been photographing the deep seas for over 10 years. The Italian-born, Dubai-based Caprodossi has combined his passions for photography and diving, creating an impressive portfolio of underwater imagery. Particularly fond of sharks, he managed to capture a stunning image of the gills of a whale shark, demonstrating the impressive anatomy of this gentle giant.
The largest living fish species, whale sharks are a slow-moving shark that can weigh up to 21.5 tons and grow up to 41.5 feet. Caprodossi was working with researchers in Djibouti and Qatar to help with photo identification when he snapped this interesting perspective on the shark. “The whale shark spot pattern is unique to each animal like a human fingerprint so photos of the area between the gills and the end of the dorsal fin are used to uniquely identify individuals and estimate populations as well as tracking movement and recurrence of the same animals,” Caprodossi explains to My Modern Met.
An image titled “Inside the Gills of a whale shark” shared to Reddit and Imgur matched Caprodossi’s work exactly, featuring the same background and view of gills in action. The image is authentic, and far more detailed than most images of whale shark gills, gill rakers, and filaments.