Predatory tunicate

The Megalodicopia hians, also known as the Predatory tunicate, is a very unique and unusual animal that resembles a cross between a Venus flytrap and a jellyfish. Though it has a small backbone-like structure in its larva form called a notochord, the Predatory tunicate is considered an invertebrate since it looses this notochord towards the end of its metamorphosis cycle. Unlike most tunicates, the Predatory tunicate is not a filter feeder, but is carnivorous in nature as it lets food enter its open mouth before snapping it closed.

It is also special in the fact that it is a simultaneous hermaphrodite, meaning it can produce both the egg and sperm from each tunicate. The life cycle of the Predatory tunicate is very interesting as it begins inside its mother tunicate and is eventually released to float about in search of a place to land. At this stage, the larvae look much like tadpoles and swim about using their tale as a propeller. Eventually they find a place to land and they do so upside down, secreting adhesives to keep them there. Throughout this process the Predatory tunicate undergoes metamorphosis and changes dramatically. The Predatory tunicate often lives a few years before it dies and is replaced by another.

Living in the deep-sea at depths of 600-3,300 feet, one might think that the Predatory tunicate would have few predators, but this is not the case. Periwinkles, sharks, snakes, and even other tunicates can cause problems for the Predatory tunicate. Other factors that can hinder the Predatory tunicate’s lifestyle is its pickiness of habitat. Not only is it very precise about what temperatures and chemical levels it has in the water, but it also cannot be removed from its canyon wall or it will die.

Though the Predatory tunicate may have some odd characteristics, it has been found to be extremely useful in the medical world. Scientists have discovered that the cellulose in tunicate tunics (from which they receive their name) can be used in muscle tissue cell alignment. This process has the capability to generate and repair damaged tissues. Some of the chemicals found in tunicates also demonstrate potential to help to treat medical conditions such as melanoma and leukemia.

Body Design


Unlike most tunicates, which are filter feeders, the Predatory tunicate is rare in the fact that it is a carnivorous predator. One observer described it as “a filter-feeding, cylindrical animal with a gelatinous tunic. ” This strange looking creature is often compared to jellyfish or Venus flytraps in appearance, as it is long and tall with a hood-shaped opening at its top. On average, the Predatory tunicate is around five inches in diameter. The Predatory tunicate has a large sock-puppet-like hood, which it uses to catch food. Often it will leave this hood-like mouth open, and patiently wait to close upon unknowing prey, such as zooplankton, that swims inside. The food enters the large siphon and can sometimes take up to five days to digest, but once digested the waste is excreted by small, flaky pellets through the excurrent siphon.

The Predatory tunicate’s name originates from its outer tunic, a protective covering against predators. This tunic is made up of material similar to that of cellulose and has a thin inner lining called the epidermis, which secretes the tunic. Inside the epidermis lies a layer of dermis that is thicker and often called the body wall. This body wall has many muscles which contract and force water and other wastes to jet out of the exhalent siphon, thus giving the Predatory tunicate, along with most other tunicates, the name “sea squirts”.

This tunicate is also unique in the fact that it is a simultaneous hermaphrodite, meaning it alone can produce both egg and sperm. Though it has this capability, the Predatory tunicate tends to do this only when conditions are poor or there are no other tunicates around. More often than not, the eggs and sperm will mature at different rates in order to decrease the chance of self-fertilization. Fertilization occurs when one Predatory tunicate releases sperm and it is carried into the incurrent siphon of a neighboring tunicate and fertilizes the eggs inside. When the Predatory tunicate is in its larval stage, it has a tadpole-looking appearance and an odd flexible backbone called a notochord. Along with this notochord, it possesses a nerve that spans down its relatively lengthy tail. This tale is strong and is used to propel the Predatory tunicate along while it is still in its egg form. The Predatory tunicate also possesses the ability to sense light and gravity, which it mainly uses when finding a place for metamorphosis when it is young.

Life Cycle
Like all animals, the Predatory tunicate goes through many stages of life. Beginning inside the egg, the Predatory tunicate lives inside a larger tunicate. This egg does not eat, but instead its entire mission is to find a new place to live other than inside its mother. In the larva form, the Predatory tunicate is microscopic and short-lived. During the larval stage the tunicate lives on the nutrients still left over in the yolk sack. Using its strong tail, it propels itself along in search of a place to undergo metamorphosis. It also uses its light and gravity-sensing features to find a good location. Once the Predatory tunicate finds its spot, it lands with its cephalic (head) side down.

The next step in the life cycle is the beginning of metamorphosis. The first stage in this process happens when adhesives are secreted. These adhesives are used to attach the larva to a base from which it will live for the rest of its life. As this is happening, the cerebral eye (connected with the brain) begins to retract and degrade as well. Next, the tail of the Predatory tunicate containing the notochord and nerve chord is reabsorbed and the excurrent and incurrent valves begin to grow larger. Soon the rest of the notochord is absorbed and the organs begin their rotations (turning to an almost 90 degree angle). At this point the cerebral eye/ganglion is almost entirely gone and the stomach and intestines slowly become elongated. The incurrent siphon, or hooded-“mouth” becomes larger than the excurrent siphon and the cerebral ganglion decreases even further in its size. By the end of its metamorphosis, the Predatory tunicate has lost is notochord, outer cuticle layer, and sensory organs, and the incurrent and excurrent siphons have greatly increased in size compared to the larval state. The stomach, esophagus, and intestines have developed and the process is complete.

After the Predatory tunicate is fully grown, it will reproduce. The Predatory tunicate is a simultaneous hermaphrodite, meaning it can reproduce with other Predatory tunicates, or it can reproduce by itself by producing both the egg and sperm. On average, the Predatory tunicate can live from one to three years before dying off or being eaten by deep-sea predators.

Ecology


Predatory tunicates are deep-sea creatures living at depths of 600-3,300 feet. Often found deep in the Monterey Bay Canyon, where they are rarely viewed by anyone but specialized divers and researchers. (Recently however, the Monterey Bay Aquarium has made a Predatory tunicates exhibit in order for the public to be more informed about them). Though most tunicates prefer reefs and are much easier to find, the Predatory tunicate is special in the fact that it likes to live on the deep seafloor or attached to canyon walls. Because the Predatory tunicate is sessile (meaning it is attached to a solid surface at its base and does not move), it does not have an extremely active way of living. A day in the life of a Predatory tunicate literally consists of sitting and waiting for food to drift into its mouth. The greatest effect that Predatory tunicates have on their surrounding environment is when it eats the tiny organisms that drift into its mouth, such as zooplankton.

Some common predators of adult tunicates can sometimes include sharks, snakes, periwinkles, and a variety of other bottom-dwelling animals. Another danger, though less common, can occur when tunicates are in their larval stage. Often they will be drifting along and accidentally float into the mouth of a fellow tunicate, being eaten. The Predatory tunicate is actually very hard to remove from its natural habitat (an example would be to relocate it to an aquarium) because once it attaches to a rock it relies on the rock to live; it needs that structure. The Predatory tunicate is also very particular as to what its habitat must be like. Its environmental ranges acquire the water temperature to be around 0.209-7.405°C, the nitrate level (umol/L) around 17.664-44.123, the salinity (PPS) (ought to be) around 34.069-34.698, the oxygen level (ml/l) 0.303-6.077, the phosphate (umol/l) 1.315-3.284, and silicate (umol/l) 4.830-180.942.

Medical Uses
In recent years, researchers have discovered that the cellulose from the tunics of tunicates is very beneficial to the modern medical world. Though scientists were aware that the tunics could be used in wound dressings and such, this is the first instance in which they have been used for the creation of new skeletal muscle tissue in humans. Tunicates have minute nanoscale whiskers that are a few billionths of a meter in size, far smaller than a human hair and the tiniest physical feature discovered to cause cell alignment. Being made out of cellulose, these whiskers are made up of polysaccharides (long strings of sugars jointed together), and are very good for giving support and structure to muscle tissues. These nanoscale whiskers are used to help skeletal muscle recovery and cause cell alignment which is important for stiffness. At the University of Manchester, Dr. Stephen Eichhorn and Dr. Julie Gough have been working in aligning these tunicate whiskers parallel with each other to cause rapid muscle fusion and cell alignment. The newly created tissues can be utilized in helping repair or grow muscle. The process is simple and for the most part fast and thus could revolutionize the healthcare industry. The cellulose is both unique in its properties and in the fact that it is a renewable resource. Researchers are now discovering what else cellulose could be used for. Some scientists are looking into aligning ligaments and nerves with this process, while also starting muscle precision engineering. It has also been discovered recently that some of the chemicals in tunicates may be of use in treating cancers and other medical conditions such as leukemia and melanoma.

Video
The Predatory tunicate is unlike most tunicates as it is very much like a cross between a jellyfish and a Venus Fly Trap in appearance. This aggressive predator clamps down its hooded mouth as soon as small creatures unknowingly swim inside. |e8jM94pNssc