New Gobies

September 9, 2020 Pacificklaus

I have been in the fortunate situation that I was able to dive again, post Philippine no-diving covid quarantine, and I have unsurprisingly used the dives to take a number of photographs of small, rare, beautiful and fascinating gobies. One of them I could initially not ID to the species, though I knew it was a Trimma:

Another dive, another Trimma. Looks like Trimma benjamini but for the line on the dorsal fin. @Eviota @thackfish to the taxonomic rescue! Cebu, #Philippines, ~ 20 meters, in a crevice. #goby #fishbiology #underwaterphotography #uwphoto pic.twitter.com/J7aJTSPk3T

— Klaus Stiefel (@Pacificklaus) September 7, 2020

It turned out that the fish I photographed is Trimma trioculatum, a goby originally discovered in Cenderawasih Bay, in the northern coast of West Papua in Indonesia. Thanks to Helen Larson for the ID! This is the paper describing the fish’s discovery, with exquisite anatomical detail:

Winterbottom, R., & Erdmann, M. V. (2015). New species of Trimma (Actinopterygii, Gobiidae) from Indonesia, with comments on head papillae nomenclature. Zootaxa, 3973(2), 201.

This is also a really interesting article about this species, with quality photographs, and it’s covering two more gobies also belonging to the genus Trimma. The photos in the article show different colors for T. trioculatum, which is an effect of local color variants. The distance between Indonesia and the Philippines is massive for such small fishes, and local variants will emerge by relative genetic isolation. As the T. trioculatum gobies mentioned in the literature, the individual I found lived along a steep reef wall.

Gobies of the genus Trimma often hover upside-down, at an angle, inside crevices on steep reef walls. I caught another Trimma doing this, in front of a sea fan:

Co-Evolution

Another curious species of goby I had the pleasure of observing and photographing is Pleurosicya elongata, which is highly camouflaged to live on elephant ear sponges. The gobies match the color of these sponges so well that it’s hard to make them out if you are not aware that there are such gobies live on the sponge surface. They are well camouflaged, small, quick, and live deeper than 10 meters, where the fading light makes it even harder to see them – the picture below was taken with a strobe, of course.