Polycheles typhlops
Encyclopedia
Polycheles typhlops is a species
of blind
, deep water decapod
crustacean
with a cosmopolitan distribution
. It is "one of the dominant and most characteristic crustaceans in deep-sea communities of the Mediterranean Sea".
to the end of the telson
. This excludes the greatly elongated first pair of pereiopods which are normally held with the first three segments close to the side of the thorax
, and the remainder held horizontal above the level of the animal's body, with the tips of the claw
s not exceeding the tip of the rostrum. This is thought to be an adaptation to predation while partly buried in the sediment. The usual colour of the exoskeleton
is whitish, orange or yellow, with the fertilised eggs
matching the colour of the pleon where they are brooded.
As in other polychelids
, and as implied by the generic names Polycheles and Pentacheles, all five pairs of pereiopods bear claw
s.
Polycheles typhlops may be distinguished from closely related species by a number of characteristics, including the presence of an indentation around the orbit
of the eye, 12–15 spines on each side of the carapace
, a forward-pointing spine on the back of each of the second to fifth segments of the pleon
, and two longitudinal ridges on each uropod, Only one other polychelid species is known to occur in the Mediterranean Sea
, although four different species of larva
have been found there.
, and on both sides of the Atlantic Ocean
, including the Mediterranean Sea
, the type specimen having been caught off Sicily
.
The species' depth distribution is less clear, with different authors citing depths of 350–900 m (1,148.3–2,952.8 ), 300–2000 m (984.3–6,561.7 ), 450–2000 m (1,476.4–6,561.7 ), 77–2055 m (252.6–6,742.1 ), and 600–1400 m (1,968.5–4,593.2 ). It is reported to be most abundant at depths of 750 metres (2,460.6 ft), 500–1000 m (1,640.4–3,280.8 ), or 900–1300 m (2,952.8–4,265.1 ). There are known to be both seasonal and geographical variations in depth, which may help to explain the variation.
, hiding buried in the sediment with its claws raised above the surface. Its main prey are bony fish
and other crustacean
s, such as shrimp
, mysids and amphipods.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of blind
Blindness
Blindness is the condition of lacking visual perception due to physiological or neurological factors.Various scales have been developed to describe the extent of vision loss and define blindness...
, deep water decapod
Decapoda
The decapods or Decapoda are an order of crustaceans within the class Malacostraca, including many familiar groups, such as crayfish, crabs, lobsters, prawns and shrimp. Most decapods are scavengers. It is estimated that the order contains nearly 15,000 species in around 2,700 genera, with...
crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
with a cosmopolitan distribution
Cosmopolitan distribution
In biogeography, a taxon is said to have a cosmopolitan distribution if its range extends across all or most of the world in appropriate habitats. For instance, the killer whale has a cosmopolitan distribution, extending over most of the world's oceans. Other examples include humans, the lichen...
. It is "one of the dominant and most characteristic crustaceans in deep-sea communities of the Mediterranean Sea".
Description
Adult P. typhlops reach a total length of 50–100 mm (2–3.9 ), from the tip of the rostrumRostrum (anatomy)
The term rostrum is used for a number of unrelated structures in different groups of animals:*In crustaceans, the rostrum is the forward extension of the carapace in front of the eyes....
to the end of the telson
Telson
The telson is the last division of the body of a crustacean. It is not considered a true segment because it does not arise in the embryo from teloblast areas as do real segments. It never carries any appendages, but a forked "tail" called the caudal furca is often present. Together with the...
. This excludes the greatly elongated first pair of pereiopods which are normally held with the first three segments close to the side of the thorax
Thorax
The thorax is a division of an animal's body that lies between the head and the abdomen.-In tetrapods:...
, and the remainder held horizontal above the level of the animal's body, with the tips of the claw
Claw
A claw is a curved, pointed appendage, found at the end of a toe or finger in most mammals, birds, and some reptiles. However, the word "claw" is also often used in reference to an invertebrate. Somewhat similar fine hooked structures are found in arthropods such as beetles and spiders, at the end...
s not exceeding the tip of the rostrum. This is thought to be an adaptation to predation while partly buried in the sediment. The usual colour of the exoskeleton
Exoskeleton
An exoskeleton is the external skeleton that supports and protects an animal's body, in contrast to the internal skeleton of, for example, a human. In popular usage, some of the larger kinds of exoskeletons are known as "shells". Examples of exoskeleton animals include insects such as grasshoppers...
is whitish, orange or yellow, with the fertilised eggs
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
matching the colour of the pleon where they are brooded.
As in other polychelids
Polychelidae
The family Polychelidae contains thirty-eight extant species of blind, benthic lobster-like crustaceans. They are found throughout the world's tropical, sub-tropical and temperate oceans, including the Mediterranean Sea and the Irish Sea.-Anatomy:...
, and as implied by the generic names Polycheles and Pentacheles, all five pairs of pereiopods bear claw
Claw
A claw is a curved, pointed appendage, found at the end of a toe or finger in most mammals, birds, and some reptiles. However, the word "claw" is also often used in reference to an invertebrate. Somewhat similar fine hooked structures are found in arthropods such as beetles and spiders, at the end...
s.
Polycheles typhlops may be distinguished from closely related species by a number of characteristics, including the presence of an indentation around the orbit
Orbit
In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...
of the eye, 12–15 spines on each side of the carapace
Carapace
A carapace is a dorsal section of the exoskeleton or shell in a number of animal groups, including arthropods such as crustaceans and arachnids, as well as vertebrates such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron.-Crustaceans:In crustaceans, the...
, a forward-pointing spine on the back of each of the second to fifth segments of the pleon
Pleon
Pleon is a Europe based Public Relations and communications consultancy. It is part of the Brodeur Pleon Worldwide network and a subsidiary of BBDO Worldwide. Pleon belongs to the Omnicom Group. Pleon is headquartered in Düsseldorf, Germany.- Overview :...
, and two longitudinal ridges on each uropod, Only one other polychelid species is known to occur in the Mediterranean Sea
Mediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by North Africa, and on the east by the Levant...
, although four different species of larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
have been found there.
Distribution
Polycheles typhlops lives in deep water throughout the Indo-PacificIndo-Pacific
The Indo-Pacific is a biogeographic region of the Earth's seas, comprising the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the seas connecting the two in the general area of Indonesia...
, and on both sides of the Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
, including the Mediterranean Sea
Mediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by North Africa, and on the east by the Levant...
, the type specimen having been caught off Sicily
Sicily
Sicily is a region of Italy, and is the largest island in the Mediterranean Sea. Along with the surrounding minor islands, it constitutes an autonomous region of Italy, the Regione Autonoma Siciliana Sicily has a rich and unique culture, especially with regard to the arts, music, literature,...
.
The species' depth distribution is less clear, with different authors citing depths of 350–900 m (1,148.3–2,952.8 ), 300–2000 m (984.3–6,561.7 ), 450–2000 m (1,476.4–6,561.7 ), 77–2055 m (252.6–6,742.1 ), and 600–1400 m (1,968.5–4,593.2 ). It is reported to be most abundant at depths of 750 metres (2,460.6 ft), 500–1000 m (1,640.4–3,280.8 ), or 900–1300 m (2,952.8–4,265.1 ). There are known to be both seasonal and geographical variations in depth, which may help to explain the variation.
Ecology
P. typhlops probably acts as an ambush predatorAmbush predator
Ambush predators or sit-and-wait predators are carnivorous animals that capture prey by stealth or cunning, not by speed or necessarily by strength. These organisms usually hide motionless and wait for prey to come within striking distance. They are often camouflaged, and may be solitary...
, hiding buried in the sediment with its claws raised above the surface. Its main prey are bony fish
Osteichthyes
Osteichthyes , also called bony fish, are a taxonomic group of fish that have bony, as opposed to cartilaginous, skeletons. The vast majority of fish are osteichthyes, which is an extremely diverse and abundant group consisting of over 29,000 species...
and other crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s, such as shrimp
Shrimp
Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...
, mysids and amphipods.