''Ligia exotica'', also called sea roach or wharf roach, is a

woodlouse A woodlouse (plural woodlice) is an isopod crustacean from the polyphyleticThe current consensus is that Oniscidea is actually triphyletic suborder Oniscidea within the order Isopoda. They get their name from often being found in old wood ...

-like isopod, a sea slater in the

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Ligiidae Ligiidae is a family of woodlice, the only family in the infraorder Diplocheta. Its members are common on rocky shores, in similar habitat In ecology, the term habitat summarises the array of resources, physical and biotic factors that ...

. It is found in various parts of the world living on rocky coasts and harbour walls just above high water mark.

Description

''Ligia exotica'' can grow to in length, with the males being rather bigger than the females. The general colour is dark grey, sometimes with brown flecks, and the appendages are pale brown. The head has a pair of long antennae which exceed the length of the body, and two unstalked, bulging eyes. The body is flattened dorsally and has seven

thoracic The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the crea ...

segments, each with a pair of legs, and six abdominal segments. The first five of these bear flat, membranous

gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

s and the sixth bears a pair of long, forked

uropod Uropods are posterior appendages found on a wide variety of crustaceans. They typically have functions in locomotion. Definition Uropods are often defined as the appendages of the last body segment of a crustacean. An alternative definition sugge ...

s.''Ligia exotica'': Wharf roach
Smithsonian Marine Station. Retrieved December 3, 2011.

Distribution and habitat

''Ligia exotica'' is believed to be

native Native may refer to: People * Jus soli, citizenship by right of birth * Indigenous peoples, peoples with a set of specific rights based on their historical ties to a particular territory ** Native Americans (disambiguation) In arts and entert ...

to the coasts of

Western Europe Western Europe is the western region of Europe. The region's countries and territories vary depending on context. The concept of "the West" appeared in Europe in juxtaposition to "the East" and originally applied to the ancient Mediterranean ...

and the

Mediterranean Sea The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the ...

. Other authorities suggest it originated in the

Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the contine ...

and

Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or ~19.8% of the water on Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by t ...

s. The fact that Roux gave it the specific name "'" when he first described the species in 1828 from near Marseilles, may indicate that it was not previously known in that locality. It has spread to many other temperate and subtropical parts of the world including the

Red Sea The Red Sea ( ar, البحر الأحمر - بحر القلزم, translit=Modern: al-Baḥr al-ʾAḥmar, Medieval: Baḥr al-Qulzum; or ; Coptic: ⲫⲓⲟⲙ ⲛ̀ϩⲁϩ ''Phiom Enhah'' or ⲫⲓⲟⲙ ⲛ̀ϣⲁⲣⲓ ''Phiom ǹšari''; ...

, the eastern seaboard of the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...

and

Hawaii Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only state ...

. It is thought that the spread occurred unintentionally via shipping, either in ballast or between the planks of timber ships. Its natural habitat is rocks and cliffs in the splash zone just above high water mark where it lives in damp crevices. It is also found, sometimes in large numbers, on jetties and harbour walls.

Biology

''Ligia exotica'' is both a grazer on microalgae and diatoms and a scavenger on plant remains and detritus. In the eastern United States, where it is considered to be invasive, it seems to be the dominant invertebrate in its habitat. The impact of this on competing organisms and its contribution to the diet of

predators Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...

has not been properly evaluated, however the NEMESIS database suggests it is not likely to be of much significance. Individual ''Ligia exotica'' are either male or female. Fertilization is internal and eggs are laid in batches of about eighty in moist cracks and fissures. Females often carry their eggs around with them using specially adapted appendages. The larvae develop into juveniles which go through a number of moults before becoming adult. ''Ligia exotica'' has a passive

water transportation Water transportation is the international movement of water over large distances. Methods of transportation fall into three categories: * Aqueducts, which include pipelines, canals, tunnels and bridges * Container shipment, which includes trans ...

system through open

capillaries A capillary is a small blood vessel from 5 to 10 micrometres (μm) in diameter. Capillaries are composed of only the tunica intima, consisting of a thin wall of simple squamous endothelial cells. They are the smallest blood vessels in the body: ...

in its legs.

References

External links

* {{Taxonbar, from=Q1049222 Woodlice Crustaceans described in 1828