Talking about the Netdevil

Hi everyone!  Dante gere with a fun story for you....

When I was a kid, my dad bought me a book on deep sea fauna. He was always supportive of me learning about oddball wildlife and I had quite a library owing to his support. I loved the book so much that after my parents had put me to bed at night and turned the lights off, I’d sneak under the covers with a flashlight and cruise through the pages for another hour or two. The book was filled with hand drawn illustrations. There were a couple that really captured my imagination. One of them was an anglerfish that had all of the normal anglerfish craziness to it and a little more – it had a glowing beard! I looked at that book so many times that it had thumb marks where I held each page and I wore its binding out. I was captivated by the crazy animals that spent their lives in the deep. In particular, the “Netdevils” (Linophryne sp.) held a special place in my heart. I made an oath at that point, as a child, that someday I’d go out onto a research ship and see one of these animals in person. It does not hurt to have one of your best friends as one of the world’s greats in deepsea fish biology (Dr. Tracey Sutton) but, somewhat unbelievably, that day arrived while working on the DEEPEND-RESTORE project.

 

 

While working on the DEEPEND-RESTORE project, we’ve encountered several netdevils; however, until a recent trip and on the last trawl of the cruise, we hadn't yet found the species that had been represented in my childhood book. We even trawled a female of another species that had a male attached to her! But this time, with the image attached here, we got the exact species from my past.

 

 

So here are a few cool things about these fishes: (1) That I am aware, this is the only group of fishes that evolved two entirely different bioluminescence systems. What do I mean by that? The "beard" that hangs off of the chin glows in the dark by way of "intrinsic bioluminescence" or light produced by the fish. The lure is "symbiotic bioluminescence" and glows by way of light produced by a bacterial symbiote. It is exceptionally rare to have two bioluminescence systems evolve in the same organism – and again, these anglerfishes are the only group of animals, that I am aware, that do this.

 

(2) Females have horns - not sure what else to say about that... but its so cool. They also have a nice set of spines on their sides. Both features are visible in some of the images shared here.

 

(3) Males of this family are parasitic on the females in that a male that finds a female bites her and holds on. Ultimately, her skin grafts with his and her circulatory system connects with his. Many of his organs begin to degenerate, except for sperm production. From that point on, she sustains him. He becomes a built in sperm factory, ready to fertilize her eggs any time she is ready to produce them.  Why?  Finding a mate in the dark depths of the ocean is clearly a challenge.  Once you find a mate, why not stay together?

 

(4) The large female in the tray that I am holding is over 7.5cm (3 inches) in total length... they are normally the size of a golf ball, give or take.

 

(5) We have found larval stages of the same fish which allowed me to organize a developmental series of images, which I have also shared here – from an early stage larva to a late stage larva to an adult female. The adult Netdevil here (Linophryne arborifera) is the ultimate in deep sea bizarre and “otherworldliness.” To the top left of the Netdevil images is the esca highlighted and to the lower left is the “beard.”