By Gus Engman and Patrick Cooney
Have you ever looked at a fish and wondered, “What is that weird thing on its head and what is it there for?” Well here is our list of the ‘Top 10 Weirdest Things Found on a Fish’s Head’.
- Electrosensitive Rostrum: “That’s no banana, that’s my nose! Acha cha cha cha.” Even at the expense of looking incredibly weird, some fish have developed extended nose like structures called rostrums that are used as electrosensory organs. Goblin sharks and Paddlefish exemplify this, most likely due to murky or dark conditions where they are commonly found, limiting their ability to visually see prey. Paddlefish rostrums are so sensitive to electrical pulses that they can sense the muscle twitch of a single plankton! Sawfish have taken the electrosensitive rostrum to a whole new level, by also using it as a weapon, with razor sharp teeth on either edge of the rostrum that cut prey in half.
- Ampullae of Lorenzini: Have you ever noticed when up close and
personal with a shark that it looks like it needs to use one of those pore-cleansing strips? Well, those dark spots aren’t blackheads, rather, they are Ampullae of Lorenzini! Say what? These jelly-filled pores are actually electroreceptors that allow sharks and other groups of fishes to sense electric fields and temperature gradients that are produced by the muscle contractions of their prey. They are even known to use them to
find animals that are buried under the sand. More recent evidence has shown that this special sensing system can even be used for navigation based on the geomagnetic field of the earth. Hammerhead Sharks have large surface areas on their heads to better detect prey with Ampllae of Lorenzini.
- Nuchal hump: It may look like this fish swam right into a ledge and
got the nastiest bump ever, but that big bump on its head is actually a nuchal hump, also known as a kok. The formation of this forehead bulge is hormonally induced and swells up on male cichlid fish right around mating time. They do rarely appear on females of certain species but are always smaller than the male bumps. Two explanations have been postulated about the purpose of a nuchal hump. (1) They are used for sexual recognition or (2) as fat stores. Either way, now you know if you see a cichlid with a swollen forehead, he is probably feeling the urge to get down.
- Sucking Disk: The remora’s highly modified dorsal fin that forms a
sucking disk allows them to grasp onto larger fish and mammals and hitch a ride. Remoras remind us of one of those deadbeat friends or younger siblings that always hangs around bumming rides but never offering to pay for gas. The remora will even try and subsist off of the table scraps or excrement of the whale, turtle, shark, ray or other large fish that it hitches a ride on.
- Sword-like Bill: A highly elongated spear or sword-like rostrum is
a distinguishing characteristic of members of the xiphiidae and istiophoridae families (Swordfishes, Marlins, and Sailfish). This bill is also a double threat to the prey of these pelagic predators because it not only stuns or injures by slashing, stabbing, or smacking, but it is also thought to make the bill-bearers faster through hydrodynamic mechanisms. These bills are also known to be a threat to unfortunate bystanders such as turtles, other billfish, divers or flotsum, which are incidentally impaled when prey fish try to use them as cover.
- Bioluminescent Lure: Have you ever found yourself standing on
the edge of a pond or stream that you just know is loaded with fish your dying to catch, but, have to exclaim “dang it!” because you forgot your rod? Well that’s not a problem for many members of the order lophiiformes, also known as the anglerfish. These deep ocean predators have a built in rod and lure that is actually a modified second dorsal spine, which they use to attract prey in close enough for capture. The variety of forms that the lure or esca comes in are enough to give any human angler tackle envy. Even in total darkness these lures help the angler fish capture its prey by luminescing or glowing!
- Barbels: Many different fish species, like catfish and sturgeons, have a network of sensory appendages hanging off of their faces called barbels. Generally, fish barbels just hang about attempting to sense electrical pulses that are generated by a prey species. Whereas goatfish have barbels growing from their chin (hence the ‘goat’ name) that they use like fingers to dig around in the sand to actively probe, excavate, and detect hidden prey. Wouldn’t it be crazy to have chin fingers?
- Kype: Salmon moving from saltwater into freshwater to breed undergo significant physical and morphological changes. Once entering freshwater, most salmon stop eating and focus entirely on upstream migration and spawning, before dying. Male salmon develop giant hooked jaws and breeding teeth on a structure called a kype. Without the need to eat, this new jaw functions to fend off other males and impress the lady salmon. I wonder if Gonzo is related to a salmon?
- Tubercles: Every year in the mountain streams of North Carolina,
one good indication of an oncoming Spring is the growth of tubercles on the snouts of Stonerollers and Bluehead Chubs. The keratin based structures most generally grow on males during the breeding season, and are shed once breeding ceases. Similar to the kype found on salmon, it is proposed that males use tubercles to not only display their prowess to females, but also in battles to defend prime spawning habitat. Many species of Suckers also get tubercles on their anal fins that are suspected to help fish dig and form proper spawning beds.
- Cephalic Fins: Giant Manta Rays are acrobatic marvels. Considering their large size and diet that consists of tiny plankton, they need any extra advantage to capture as much food as possible. Manta Rays use cephalic fins to funnel plankton-rich water into their mouths where gill rakers filter out the plankton. When not feeding, Manta Rays often extend these fins, giving the appearance of horns…hence the name “Devil Rays”.
Incredibly, many of the top 10 weirdest things found on fish heads have similar functions. Without surprise, many help the fish eat, mate, defend itself against predators, or provide camouflage.
Tell us in the comments below which one you think is the weirdest. Do you know of any more weird or awesome fish head attachments? Add them to the comments section below!
Here is a list of additional fish with weird heads:
Slender Snipe Eel
Pacific Barrel Eye Fish
Leafy Sea Dragon
Weedy Sea Dragon
One more thing: Thank you to all who have read and contributed to The Fisheries Blog. We were honored to recently be recognized by industry leading Fisheries Magazine as a leader in sharing fisheries information through Social Media. See the link to the article (http://www.thefisheriesblog.com/2013/04/the-fisheries-blog-gets-recognition.html)