MARINE LIFE & BIODIVERSITY: the Unicorn Shrimp
Plesionika Narval; the unicorn shrimp
Of all the dive sites that can be found in the marine protected area of Ustica‚ there is one in the southwestern part of the island that has been catching my attention for some time‚ and that is the so-called "Grotta dei Gamberi"‚ "the shrimps cave" . In this cave you can find many types of marine species‚ but present in large quantities and that populate every wall of the cave: the Plesionika Narval shrimp. In this blog I would like to describe some characteristics and curiosities of this shrimp‚ the Plesionika Narval.
Description of the Unicorn Shrimp
The Unicorn shrimp is‚ like any shrimp‚ a decapod. It has 10 walking legs or pereopods. The unicorn shrimp is characterized by a pale red color with red and white lines running over the length of its body. The shrimp´s legs and antennae are bright red. The two front antennae are longer than its body and the front legs longer than the back legs. The body of the unicorn shrimp can reach a length of 16 cm and is divided into three parts: head‚ chest and abdomen covered with a hard exoskeleton for protection. The rostrum (front outgrowth) of the unicorn shrimp is very long and thin and is characterized by 60 upper and 50 lower teeth. This very long rostrum explains the name this shrimp is known by: “unicorn shrimp”.
Habitat of the Unicorn Shrimp
The unicorn shrimp is a species that lives in the Atlantic and Mediterranean Sea. Being a photophobic species‚ it lives at very deep depths up to 900 meters on sandy bottoms or in caves at lower depths. In the marine protected area of Ustica we can mainly find the unicorn shrimp while diving in the “Grotta dei Gamberi”; In fact‚ this dive spot lends its name to the large number of these shrimp that live inside the cave.
Feeding of the Unicorn Shrimp
The unicorn shrimp is omnivorous and will eat practically anything it can find. It feeds on other invertebrates or other animals that are already dead or dying but can also feed on vegetable matter. The unicorn shrimp can sense the presence of prey thanks to its antennas that sense vibrations in the water. Once it has found its meal‚ it will begin a real fragmentation of its prey thanks to its sharp teeth.
Reproduction of the Unicorn Shrimp
Reproduction of the unicorn shrimp takes place through fertilization. During mating‚ the male rubs his belly over that of the female‚ who collects the sperm in special bags. While the eggs are being fertilized‚ they are deposited in the female´s tail fan‚ where they remain until hatching. Hatching varies from a few weeks to several months in relation to the temperature of the water. The young unicorn shrimp do not resemble the adult perfectly at birth‚ as they go through larval stages that are often very different from their final shape. The unicorn shrimp can reproduce several times a year but mating mainly takes place in the period between spring and autumn‚ often in March.
Life expectancy of the Unicorn shrimp
The lifespan of a unicorn shrimp is relatively long‚ maybe 7 years. However‚ the unicorn shrimp has many enemies: from hake to humans; These are often found on restaurant menus. Its lifespan therefore also depends on the area in which it lives‚ where a marine protected area contributes to the conservation of this species.
Important and interesting Facts of the Unicorn Shrimp
- During its growth‚ the unicorn shrimp loses its old shell several times and gets a new one. This process is called "molting" or "ecdysis" and occurs because the exoskeleton has a rigid structure. The tissues it contains‚ on the other hand‚ are subject to growth‚ to the point that they no longer fit inside the shell. The unicorn shrimp will have to release its old shell to form a new one.
- The unicorn shrimp is often found in cavities where moray eels live. Here it lives in symbiosis with the moray eel; The shrimp offers a cleaning service by eating all leftover food.
- Unicorn shrimp females carry between 1000 and 9000 eggs under their tail for just under two months before hatching. They are easily recognized by the purplish eggs that can be seen underneath their bodies.
Dive sites where to spot the Unicorn Shrimp?
The unicorn shrimp is a photophobic species that lives in depths or caves. There are dive sites where it is easier to spot this shrimp‚ such as:
In the marine protected area of Ustica:
Dive site Grotta dei Gamberetti
In the marine protected area of Isola delle Femmine:
But you have to be a bit of an adventurer to find the unicorn shrimp. With the right experience and the right scuba diving training‚ for example PADI TEC Deep Diver courses‚ it is possible to dive into the famous shrimp cave to admire thousands of these shrimp that line every wall of the cave.
Andrea Denaro
PADI Divemaster in training
