Regis University professor discovers deep-sea eels' strange evolutionary strategy

Despite humanity’s never-ending search for knowledge, only 5 percent of the world’s oceans have been explored. The deepest parts of the ocean are home to some of the most unique and highly specialized organisms on the planet. Mike Ghedotti, Ph.D., professor of Biology at Regis University, alongside recent Regis graduates has made strides in deciphering the mysteries of the deep.  

Ghedotti teaches courses in the undergraduate program and in the M.S. in Environmental Biology program at Regis University. His research specializes in the anatomy, evolution, and diversity of marine and freshwater fishes. Deep-sea, ultra-black eels were the subject of his most recent study and were coincidentally brought to his attention while teaching at Regis. 

Two of his undergraduate students, Kandice Agudo and Flor Gonzalez, were credited alongside Ghedotti in a study published last July in the journal Environmental Biology of Fishes. Agudo and Gonzalez assisted with the tissue sampling and photography, providing them the opportunity to gain credit for published research. 

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

“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,” Ghedotti said. “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.” 

There are nearly 1,000 species of eels living in freshwater and marine environments and most of them are predators. Ultra-black camouflage is incredibly effective to eels as predators. The dark environment of the deep ocean provides excellent cover for eels like the pelican and swallower eel which use their glowing tails to lure prey.  

“This 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," Ghedotti said. 

Being able to research deep-sea eels in Denver, however, is quite a task. Ghedotti, through his research background, formed a relationship with the Scripps Institution of Oceanography, in San Diego. His colleague, Benjamin Frable, who oversees the institute’s collection, allowed Ghedotti to borrow and use specimens at Regis. 

“Doing this is somewhat like borrowing from a library except, unlike books, they come in the mail moistened with alcohol and wrapped in cloth. We return them when we're done, sometimes with small samples taken from them,” Ghedotti said.  

Creating the opportunity for undergraduate students to work with unique samples and research has been something that Ghedotti has prioritized in both this study. He plans to continue this with future research at Regis. According to Ghedotti, research with students can be incredibly fun and rewarding, but it also promotes the Jesuit value of cura personalis.

The study of deep-sea marine life at Regis does not end here as Ghedotti continues his research with more Regis undergraduates. He hopes that this summer the continued project of looking at the anatomy and histology of the pelican and swallower eel light organs will be ready to be submitted for scientific review. Additionally, he plans to work with other students on the anatomy of other bioluminescent and deep-sea fishes, in hopes of increasing understanding and respect for deep-sea marine environments.