Unseen Monsters of the Underworld

Snail fishes are scaleless with thin loose gelatinous skin, their teeth are small and occupies blunt cusps. There is a wide distribution such that the ones in cold marine waters have anti freeze proteins! It has a record of being the deepest living creature, as it was filmed at 8000 meters depth in the Mariana trench. Menu chart of Snail fish consists of crustaceans, earthworms, mollusks, and sea cucumbers. Some species deposit the eggs among cold water corals, kelp or stones. As no much details about this creepy creature it is believed that males guard the cell mass, and carry carry the eggs in their mouth. Life span is less than a year for certain species, but it could last a decade for others.

Enormous mouth is larger than the body, lower jaw is loosely hinged at the back of the base of the head enabling it to gobble prey larger than its size! Food is primarily crustaceans, and scoop on shrimps as well as squids. They live in tropical and temperate regions of the world. Found rarely in deep fishing nets only. In males the olfactory organs become enlarged, so that they could locate females using the pheromones released by them, and most researchers believe that they die shortly after reproduction.

This monstrous looking fish lives in deep waters of tropical and temperate regions of the sea. It is believed to live 30 to 40 years in the wild! They attack and swallow whatever random prey they encounter. Their dark coloration helps them to be invisible and can remain motionless for hours to strike on unsuspecting prey! The first vertebrae  behind the head acts as a shock absorber. Petite bulb which hangs at the back lures prey towards the fish. Diet consists of crustaceans and small fish. Migration from deep to shallow waters is observed at night. Not much details available about its reproduction, but believed to follow the usual external fertilization technique.

Looks like Venom isn't it? I mean the eyes... Though it is non deep sea fish it has bio-luminescent organs below the eyes. Yes what you see is not the eyes, but light emitting organs, this bio-luminescence is brought about by bacteria working as light producing factories within the organ. They are nocturnal and have a flap of skin to veil and reveal its light thus it seems to blink. This ability helps to confuse predators and communicate with other members of the species. Females larger than males, and protect males from intruders! Diet is zooplankton, shrimp, and small fish. External fertilization occurs, about 600 eggs produced by females.  For more info check out the link below:   https://www.nationalgeographic.com/animals/2019/08/flashlight-fish-glow-blue-for-schooling/

The name of the fish reveals its identity. Have a slender compressed body, and terminal mouth with small teeth. They feed on zooplankton, hence they stay in deep waters during the day and rise up in the night as they follow the migration of zooplankton, this is called as diel vertical migration. This strategy is followed to prevent predation as well. Photophores (light producing organs) present in the body and head. Reproduction done by releasing eggs into the water and then fertilized externally by males.

It looks fantastic isn't it? Purely carnivorous fish with fang like teeth. Females larger in size compared to males!!! Special thing about this fish is the bulb that hangs in-front of it called esca. It is powered by bio-luminescence, through symbiotic relationship with bacteria. Enormous size of jaws allows it  to gobble prey as twice as large compared to its body size! Now lets observe how they mate: Males bite females and behaves as parasites absorbing nutrients from the blood circulatory system in return males provide sperms, simple as that. If a male didn't find a female in the dark using  pheromones and large eyes, its a pathetic situation for him to die without mating.