This is the First Deep-Sea Fish Known to be a Mouthbreeder

Rory Christian
3/19/20
AP Biology
Current Event 20

Buehler, Jake. “This Is the First Deep-Sea Fish Known to Carry Its Eggs in Its Mouth.” Science News, 10 Mar. 2020, www.sciencenews.org/article/parazen-deep-sea-fish-mouthbrooding. 

A recent study reveals the first known fish from the deep sea to carry eggs in its mouth. Many fish breeds cast their gametes outside of their bodies, leaving their young to develop on their own. 2 percent are "mouthbreeders", as they keep their eggs protected in their mouths. Recently scientists found over 500 eggs inside of a parazen's mouth, the first deep-sea fish known to do this. Randy Singer, an ichthyologist at the University of Michigan Museum of Zoology was identifying fish when he noticed a red fish pass by the camera. He later identified it as a parazen, a poorly known species found in the deep West Atlantic and West Pacific. When examining the fish later he peeled back its gill to find a "big, gnarly clump of something in its mouth”. Looking closer, he realized that the clump was a mass of eggs. Using a CT scan, they estimated that there were 530 developing embryos in the mouth. 

This discovery is very unusual because deep-sea fishes spawn externally, this being the first deep-sea fish to mouthbrood. In general, mouthbrooding is very difficult and costs more energy than simply letting the young develop on their own. The parazen is also choosing to invest much more in protecting their young that scientists would have predicted. This raises an interesting question about why this certain fish has chosen to take this route. It is possible that the environment favors mouthbrooding. This discovery shows that there is a greater diversity of reproductive strategies in the deep ocean than we have known. Scientists are now looking deeper to unveil more about how fish have adapted to deep-sea living. As Singer says, "I would expect people to see many more new discoveries coming rapidly in the future". 

Overall this article was well written and one of the more detailed and thorough articles I've read. Still, I wish that the article had expanded more upon the mouthbrooding process in more detail. Nonetheless, this article was very informative. I especially liked the image of the CT scan of the fish's mouth. This was very interesting and a great visual representation of what the article was about. In the image, I could clearly see the mouth full of eggs, as the egg masses were colored bright red to show their placement.