Friday, March 21, 2014

Deep Sea Anglerfish

Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Actinopterygii
Order: Lophiiformes
Family: Melanocetidae
Genus: Melanocetius
Species: johnsonii
(Australian Museum)

Melanocetus johnsonii, the Humpback Anglerfish, is a type of deep sea anglerfish that lives in depths about  100- 4,500 meters (FiseBase) and can be found worldwide. It is also called the Black Seadevil. They can reach up to about 5in in length. This anglerfish gets its name from their dorsal spine- it makes their back look humped. The spine also leads to the photophore atop of their head. The body of this anglerfish is round, and it has a large mouth with teeth that angle inward. Humpback Anglerfish can be brown, dark gray, or black. The skin of an anglerfish tend to be fleshy and light-reflective; this helps them adapt to their surroundings as well as defend themselves against predators. Fleshy skin helps the fish to stay warm since it is very cold at the depths that they live at. Having skin that reflects light also helps to not only hide themselves when they are using their lophophore, but other predators that use light to find prey will tend to look over the deep sea anglerfish because they would not be able to see them.

Obviously, the anglerfish's photophore is the characteristic that most people identify with. That, or most people think "that scary fish from Finding Nemo?" -- yes. This photophore dangles above their head and lights up. The anglerfish's prey is attracted to this light; If you remember the scene in Finding Nemo, you see Marlin and Dory swim toward the light thinking that it is just a beautiful little friend. (You can watch the scene here!)The anglerfish dangles the photophore to catch their prey's attention while the rest of their bodies stay completely still. They tend to keep their mouths open, and when their prey gets close enough, they will slam their mouths shut trapping their prey inside where they will then eat them; this is why their teeth are angled inwards- so their prey cannot escape. One thing that an anglerfish has the ability to do is extend their jaws and stomach to be able to eat and swallow prey that are twice its size. This is a great adaptation for the fish considering that there is not a lot of food in the depths of the ocean. Having the ability to expand their stomach comes in handy, because then they can conserve energy just in case they are not able to find food for a longer period of time. The video below gives a great look at a specimen of a different species of anglerfish; I thought it would be good to post, though, because you can see how large its stomach can expand to eat their prey.

Deep Sea Anglerfish have a really interesting way of reproducing; and by "really interesting", I mean really creepy. For one, male anglerfish are smaller than female anglerfish; "It is about the size of a small finger and black in color" (SeaSky). After a male anglerfish matures, their digestive systems degenerate. Obviously, if they do not have a digestive system, it makes it impossible to eat, let alone live. This is when the male anglerfish finds a female to attach to with his teeth. He is able to find a female based on pheromones that the females gives off. "Once he bites into their skin, he releases an enzyme that dissolves the skin of his mouth and that of her body" (SeaSky). After this, the male and female are essentially one, and the male will spend the rest of his life on the female. The female anglerfish can have multiple male anglerfish on her body at one time- usually up to seven males. When it comes to reproduction, "...when the female is ready to spawn, she already has a mate available" (SeaSky). A thin, gelatinous sheet containing the anglerfish's eggs floats in the water until the eggs hatch. The larvae then swim to the surface to eat plankton, and return to the deep sea when they become adults. The video below is another great video on how this reproduction strategy was discovered and how the anglerfish reproduce!


  1. Julie, I really liked your section on the reproduction of the anglerfish! I have to admit the video was a little creepy, but I learned something new.

    I also didn't know about that CT scanning method for developing images of specimens. It's incredible to see the all structural features of the anglerfish plus what it had for its last meal. Kudos to you for finding such an awesome YouTube video!

  2. These fish should have the same internal temperature as their surroundings, so "fleshy skin" is probably not holding in heat.