Fish are the most diverse vertebrates when it comes to aquatic environments. In fact, there are about 28,000 species of fish around the world. They have a large number of anatomical and physiological adaptations that have allowed them to successfully evolve over the years. At the same time, in the immense number of life forms that exist within this group, we will find different fish throughout the water column, and this will depend on the ecological requirements of each species. In this sense, there are very particular species that, thanks to their lifestyle do not need sunlight to live, and are known as abyssal fish.
If you want to know more about the abyssal fish, their characteristics and names, keep reading this article on our site and we will tell you everything about them.
Characteristics of deep-sea fish
Abyssal fish are a group of species that have the ability to live in the depths of the ocean, where other fish could not survive. In this area, it should be noted that the conditions are very different from others closer to the surface, since the main ecological factors that influence here are sea currents, the absence of light, food sources, low temperatures, high pressures and chemical factors (amount of oxygen, pH and nutrients). So much so, that these fish share a series of characteristics that makes them very special and striking, such as the ones we will see below:
- Esqueleto: as it is an area where waves are not generated, only weak currents, deep-sea fish do not need solid bone structures to resist the turbulence of seawater. In addition, it is also due to the fact that, in these deep conditions, there is not enough calcium (the main compound to form the skeleton), nor is vitamin D generated due to the lack of sunlight.
- Body: in general, they do not have bright or striking colors, some can even be albino, and a trait that makes them very unique is the presence of bioluminescent organs (photophores) in some regions of its body. The macrourids (Gadiformes), also called "rat tails", are fish that live in depths greater than 1.000 meters. They have a very peculiar appearance, with thick and armored heads, and a body that thins quickly and abruptly to end in a "whip"-like tail that can reach up to 30 cm in length. At greater depths, the fish have more flexible and soft bodies, similar to jellyfish. Regarding the water pressure, they do not need special adaptation, since the pressure is the same inside and outside their body. This is because they have lost their swim bladder, which is present in other shallower fish.
- Mouth: Some species have extremely large mouths compared to their bodies, an adaptation to the lack of food sources. The development of these mouths and, in addition, of stomachs that can dilate, allows them to feed on larger prey, even many times larger than themselves. Some species look like they only have a head and jaws, others have huge, sharp teeth that don't fit into their mouths when they close. The lack of food forces these species to take advantage of everything that falls from the upper levels of the seabed.
- Eyes: some species have huge eyes, however, others have no or very small eyes, and in these cases have an acceptable view. These fish have a retina with a total absence of cones, which are the cells responsible for controlling visual acuity and color perception, however, the rods are well developed. These cells react to the weak light produced by bioluminescence and can produce quite sharp images. In addition to this, deep-sea fish have a tapetum (strengthening layer) behind the retina, so that light entering the eye is reflected by this layer and passes through the retina twice. This increases light sensitivity and enables them to perceive their prey or predators in the total darkness of the abyss. On the other hand, these eyes are adapted to react to bioluminescence, but not to bright colors, and that is why these species do not have colored bodies, and rather have brown and dark tones.
To better understand abyssal fish, we advise you to read this other article on our site about the Characteristics of fish.
Types of deep-sea fish
Within the types of abyssal fish, some of the most notable are:
Fishing fish (Ceratias holboelli)
This fish of the Lophiiformes order inhabits the depths of all the planet's oceans. It is a large species, and can reach more than a meter in length It has a predatory strategy that consists of using a filament that comes out of the upper part of your body, which is made up of the first three vertebrae of your skeleton. The first of the filaments is the longest and is the one that uses to “fish”, since it is mobile and lights up thanks to bioluminescent bacteria with which it performs a symbiosis. In this way, the light emitted by the filament is used as a lure to attract prey.
Abyssal Anglerfish (Melanocetus johnsonii)
Another example of abyssal fish of the Lophiiformes order that is present in the ocean floors of the tropics. The abyssal anglerfish has a very curious mode of reproduction and represents an extreme case of sexual dimorphism. The female is large, reaching a meter in length and the male is a parasite ten times smaller The male (which does not have a digestive system) attaches and fuses to the female's body, where it is nourished by her nutrients, and in turn is a constant source of sperm. This happens thanks to the fact that he has a highly developed sense of smell and locates the female through pheromones.
Viperfish (Chauliodus sloani)
Abyssal fish that belongs to the Stomiiformes order and is distributed in temperate and warm waters of all oceans, found at depths of about 5,000 meters. It has an elongated body similar to a snake (hence its name) about 35 cm long, the male being larger than the female. Its jaw is so large that in order to swallow its prey it must dislocate it and, in addition, it has enormous and sharp teeth.
In addition to these abyssal fish, you may also be interested in this other article on our site about Animals of the deep sea.
Whipfish (Saccopharynx ampullaceus)
It is a species of the Saccopharyngiformes order that reaches depths of 3,000 meters and is distributed throughout the Atlantic Ocean. It reaches more than 1.5 meters in length and its body is dark brown, being almost black near the head. It has an extremely long and thin tail that can reach four times the length of the body. In addition, adults suffer from jaw reduction, but their sense of smell is very well developed and they can capture prey larger than themselves thanks to the fact that their stomachs can expand.
Pelican fish (Eurypharynx pelecanoides)
Species of the order Saccopharyngiformes, is distributed in temperate areas of all the oceans. It measures about 60 cm and its shape resembles an eel, which is why it is also called a “voracious eel”. What stands out in a very striking way is the size of the mouth, which becomes larger than the bodyIts common name is due to the fact that its lower jaw opens reminiscent of the gular bag of a pelican, being able to swallow huge prey. Its body ends in a long, thin tail that ends in a bioluminescent organ that it uses to attract prey.
If you want to know more about the wonders that the ocean hides, you may also be interested in reading this other article about The largest sea fish in the world.
Other deep sea fish
Other of the most notable deep sea fish are:
- Spiny stickleback (Himantolophus appelii).
- Dragon fish (Stomias boa).
- Leptostomias gladiator fish.
- Toothed firefly (Gonostoma elongatum).
- Hatfish (Argyropelecus aculeatus).
- Spiny Frogfish (Caulophryne jordani).
- Square-nosed Helm (Scopelogadus beanii).
- White Abyssal Cerato (Haplophryne mollis).
- Red velvet whalefish (Barbourisia rufa).
- Craw fish (S accopharynx lavenbergi).