Today we are going to talk about witch fish, a marine animal whose appearance is very strange and fascinating in equal parts. They lack jaw and their elongated body is reminiscent of that of eels. They are also known as hagfish. Its scientific name is Myxini and belong to the family Myxinidae, within the group of the agnate or jawless fish.
If you want to learn everything about the hagfish, keep reading and discover its secrets: anatomy, defensive drool, Feeding Habits, the habitat, its ecological paper and the latest findings on its evolution and genetics.
Characteristics of the witch fish
This curious fish has the bare and very loose skin, without scales, and has numerous mucous glands distributed throughout the body. Its skeleton is cartilaginous, so that the internal structure lacks true bones. They are classified among the agnate and are considered one of the oldest vertebrate lines still alive.
As mentioned, lack a jaw and they only have one nostril external. Its eyes They are rudimentary and covered by skin, so their vision is very limited; they depend mainly on the smell and the touch to orient themselves and locate food. Consequently, their life is spent mainly in the sea bottom, where they burrow and hide.
For a long time it was thought that the hagfish was an "incomplete" vertebrate, because although it has skull (of cartilage), it does not have vertebrae defined in the trunk. This uniqueness makes it a unique case among living vertebrates and helps explain its great flexibility to move between cracks and soft sediments.
As for their size, there are differences between species: most measure between 30 and 60 cm, although there are species that exceed the metro. Their skin is usually shades grayish or pinkish and is kept separated from the musculature by a wide subcutaneous cavity filled with fluid and blood, which gives them elasticity and the ability to withstand bites without damaging vital organs.
- Her first book of poems, Cuerpo, elongated, without paired fins and with a continuous fin in the caudal region.
- Tentacles tactile areas around the mouth, which increase sensitivity to contact.
- Loose skin attached to the body by a narrow longitudinal "seam".
- Blood pressure extremely low and large volume of blood relative to weight.
Although it has sometimes been claimed that most hagfish have become extinct due to their "poor evolution", it is correct to say that many ancient lines of agnates Yes, they disappeared, but the hagfish have endured successfully thanks to extraordinary adaptations such as their slime, slow metabolism, and feeding mode. In marine systems, their role is crucial: "recycle" organic matter consuming carrion and cleaning the bottom.
Meals
Par excellence, they are opportunistic detritivores that feed on carrion marine and of dying fish. Fisheries discards, when they reach the bottom, can also be exploited by these species. However, various studies of stomach contents have shown that their diet includes benthic invertebrates , the prawns y polychaete worms, confirming that they do not depend solely on carrion.
Their feeding method is as peculiar as it is effective. They attach themselves to a dead or dying fish and, with their keratinized tongue and its scraping apparatus, can penetrate through natural openings or make an incision to eat from withinWhen their prey is alive but defenseless, they take advantage of the opportunity to quickly consume the viscera. They can ingest it in a short time. several times its own weight in food.
Another striking ability is that its skin can absorb dissolved organic matter, something typical of marine invertebrates and unusual among fish. In addition, their taste buds They do not concentrate only on the mouth: They are also on the skin, allowing them to “taste” their environment and detect sources of nutrients in the water around them.
The hagfish has a very slow metabolism, so you can go long periods without eating, an adaptive advantage where food is scarce. To tear chunks of flesh from tough carcasses, they resort to a typical movement: form a knot with their body and pull their heads through the loop to gain leverage and tear tissue.
Although many of these behaviors are difficult to observe directly in the complete darkness of the seabed, the combination of fishing observations, stomach analysis and laboratory records have built a very solid picture of their trophic behavior.
Habitat
The hagfish lives in almost all temperate seas of the planet, with notable absences in regions such as Arctic, Antarctica y Red Sea, where environmental conditions are not favorable to them. They preferentially occupy great depths, where pressure is high, light is minimal, and the bottom is covered with soft sediments. For more information on their classification, visit the main groups de peces.
Your ability to dig and burying themselves allows them avoid predators y wait the passage of potential food. In shallower waters they may show greater night activityThe best-known species of hagfish in the Atlantic frequently reaches the half a meter, although there are larger species in other latitudes.
To feed de peces dying or corpses, the pierce with their tongue and its apparatus “horn teeth”, devouring flesh and guts with impressive efficiency. The distinct arrangement of the gill slits between species (sometimes they converge in a single opening and others open individually) illustrates their anatomical diversity.
On the seabed, hagfish help to decompose large food drops, such as the remains of marine mammals, thus participating in the recycling of nutrients from the deep ecosystems.
Witch fish slime
One of the most surprising characteristics of these animals is their defensive drool. It is a substance gelatinous that covers the fish and that released in large quantities when they're stressed or threatened. Although it may seem "disgusting," it has a clear purpose: defend them from their predatorsFor more details, see this video on YouTube.
When the mucus comes into contact with seawater, it expands creating a fibrous mesh that catches water and clogs the gills of potential attackers, making it difficult for them to breathe. It is not a toxic substance; its effectiveness is mechanicsA medium-sized hagfish can release in tenths of a second amounts of slime capable of generating tens of liters of watery gel, forming a viscous cloud that gives it time to escape.
The secret is in its microstructure: the slime contains protein fibers Ultra-thin, much thinner than a human hair, and surprisingly resistant, along with mucins. When mixed with water, these fibers create a three-dimensional network able to capture a volume of extraordinary water, multiplying the weight of the initial solid secretion thousands of times. By its nature, it is a product unstable which dissolves relatively easily with the movement of water, fulfilling its purpose without persisting.
To avoid suffocating in its own slime, the hagfish performs an effective maneuver: a knot is made and slides it toward the head, "cleaning" itself in seconds. This same knotting ability also helps it gain traction when feeding on tough tissue.
Skin and composition
Under the skin there is a wide subcutaneous cavity filled with fluids and blood. It is thought that, thanks to this space, hagfish can increase rapidly the volume of slime before the skin "hits the ceiling". In tests simulating shark bites, the skin deforms and bends around the teeth, allowing internal organs move out of danger. When the skin is immobilized over the muscles, the teeth pierce easily, which demonstrates the importance of that protective clearance.
Hagfish form knots with their body thanks to their flexible, scaleless skin. This knotting compensates for the lack of true jaws: the loop allows them tear off flesh of hard corpses and, in addition, it makes it easier for them remove your own mucus after a defensive episode.
On its head stand out cartilaginous structures such as the lingual cartilage, with horn teeth, which make up the rasping apparatus, and subnasal and tentacular elements that support and shape the oral region. Several gill pouches manage respiratory water flow, which can be propelled from the nasal opening inward by muscular action. For more details, see .
Accident with hagfish
A well-remembered case was that of a accident on an Oregon highway in which a truck overturned with a tank loaded with several tons of hagfishWhen the contents spilled onto the asphalt, the stressed fish released their sticky slime everywhere. When mixed with water, the pavement became covered in a slippery layer that was very difficult to handle.
The slime is so dense and adhesive that removing it from clothing is extremely complicated. To return the road to normal, it was necessary heavy machinery able to remove that gelatinous mass. The episode popularized the hagfish's reputation as a "slime animal", underlining the power of its defense.
Taxonomy, evolution and genetics
The hagfish form the class Myxini, within the order Myxiniformes and the family Myxinidae, with around 60 species described. Together with the lampreys, they make up the clade Cyclostomi (living agnatha). Modern genetic evidence supports that hagfish are vertebrates very old whose vertebral segments were reduced or lost secondarily, despite maintaining a skullFor more related topics, visit how many species exist.
Recent genomic studies have sequenced for the first time the hagfish genome, providing clues about the genomic duplications that preceded the diversification of vertebrates. Their DNA is organized into numerous microchromosomes with many repetitive sequences, which makes their analysis difficult. A striking feature of the lineage is that part of these microchromosomes can get lost in somatic tissues during development, maintaining the complete genome in the gonads, a fact that further complicates sampling.
In evolutionary terms, hagfish have retained a stable morphology for very long periods, a sign that their anatomical and physiological strategies they work exceptionally well in the conditions of the depths.
Senses and nervous system
Its sensory system is based primarily on the smell (they have a highly developed olfactory bulb) and the touch (thanks to tentacles and cutaneous receptors). They lack an organ of lateral line typical, although they have structures in the head that could perform analogous functions.
The eyes The hagfish's eyes are small and poorly pigmented, but they share characteristics with those of other vertebrates: they have neurons that connect photoreceptors with ganglion cells, show continued eye growth throughout life and have support layers key cells for the function of photoreceptors. However, their vision forms very poor images; the detection of light changes seems to be his main visual ability.
At the neural level, their axons are not myelinated as in most vertebrates. There are debates about the presence or extreme reduction of structures such as the cerebellum, and its spinal cord exhibits a simple organization. For more information, see the section on .
reproduction and life cycle
reproduction is oviparous with external fertilizationThe laying usually consists of few eggs, relatively large, oval and provided with adhesive filaments which hold them together in small piles. From these, juveniles emerge that already resemble adults; there is no larva very differentiated.
Some species have a single gonad with testicular and ovarian tissue, and can mature gametes at different times to avoid self-fertilization. In others, the sex ratio is very unbalanced, with populations dominated by females and very few males. Hagfish are reluctant to grow and to date they do not reproduce reliably in captivity, so most of what we know comes from field observations and the study of captured specimens.
Ecological role and relationship with humans
Hagfish play an essential role as scavengers from the seabed. In events such as the whale falls, together with other organisms, contribute to dismantling the tissues already recycle nutrients, accelerating the regeneration of organic matter in the ecosystem. This "clean-up crew" function makes them ecological links fundamental.
In their interaction with fisheries, they can take advantage of caught fish in bottom nets, feeding on wounded or dying individuals and sometimes causing economic losses. On the other hand, in some Asian countries its meat is consumes and its skin is used in crafts and leather goods. The baba has sparked enormous interest in research biomaterials for its ultra-fine protein fibers, inspiring potential textile and medical applications due to its combination of lightness y resistance.
Rare, resilient, and tremendously effective in their niche, hagfish are living proof that evolution finds ingenious solutions to extreme problems: a jawless mouth that scrapes, one baba that suffocates predators without being toxic, leather loose that shields organs and a smell able to guide them through the abyssal darkness. Understanding them better not only unravels mysteries of the evolutionary history of vertebrates; it also provides ideas for bio-inspired technologies and remember the importance of caring for the silent processes that sustain life in the deep ocean.
