Some evolving eels glow their own way, professor and students find

By Hadley Jenkins

Regis biology Prof. Mike Ghedotti, Ph.D., borrows eels the way some people borrow library books.

Studying the evolution of creatures who live in the darkest ocean depths is quite a task in landlocked Colorado. Luckily, Benjamin Frable, who oversees the eel collection at the Scripps Institution of Oceanography in San Diego, allows Ghedotti to borrow and use specimens at Regis.

This eel-sharing has paid off for Ghedotti and for his students. Ghedotti teaches in the undergraduate program and in the Master of Science in Environmental Biology program at Regis, and specializes in researching the anatomy, evolution, and diversity of marine and freshwater fishes. Recently, he began focusing on deep-sea, ultra-black eels.

Ghedotti and his students found that deep-sea gulper eels have been evolving independently from one another and developing the ultra-black pigmentations that were discovered in 2020. Ghedotti explained that the ultra-black pigmentation occurs when the skin cells release especially small bundles of melanin, allowing the skin of these eels to absorb more light than normal and appear very dark.

His findings were published last summer in the journal Environmental Biology of Fishes. Two undergraduate students, Kandice Agudo and Flor Gonzalez, who assisted with tissue sampling and photography, also were credited on the paper.

“We actually were in a biology laboratory on the Regis campus studying the light producing structures on the gulper eels by using a process called histology that looks at the specific tissue-level of structure,” said Ghedotti, “When looking at the eel light organs we ended up puzzled by the structures in the skin that did not look at all like the usual skin pigment cells ... We were not initially planning on looking at this, it was just another unknown thing we found by chance.”

The gulper eels’ coloration “likely evolved repeatedly in the ancestors of the lure-waving pelican eels and swallower eels, and separately in the bobtail eels, snipe eels, and sawtooth eels. In the deep habitats where these eels live, most light is very dim and is produced by animals, so that ultra-black coloration can provide especially effective camouflage,” said Ghedotti.

There are nearly 1,000 species of eels; some live in fresh water, many others live deep in the dark regions of oceans. Nearly all are predators.

Ultra-black camouflage is effective to eels as predators. The dark environment of the deep ocean provides excellent cover for them, especially those that use their glowing tails to lure prey.

Creating the opportunity for undergraduate students to conduct research is something Ghedotti prioritizes. He said involving students can be incredibly fun and rewarding, and also promotes the cura personalis Regis strives for by helping students gain skills and experiences they can use in the future.

This summer, he hopes to submit for review research on eels’ anatomy and histology, and is working with students on the anatomy of other bioluminescent and deep-sea fishes. Ultimately, he hopes his findings increase understanding of and respect for deep-sea marine environments.