''Deto echinata'', the horned isopod, is a species of air-breathing

isopod Isopoda is an Order (biology), order of crustaceans. Members of this group are called isopods and include both Aquatic animal, aquatic species and Terrestrial animal, terrestrial species such as woodlice. All have rigid, segmented exoskeletons ...

, or

woodlouse Woodlice are terrestrial isopods in the suborder Oniscidea. Their name is derived from being often found in old wood, and from louse, a parasitic insect, although woodlice are neither parasitic nor insects. Woodlice evolved from marine isopods ...

, in the family

Detonidae Detonidae is a family of woodlice in the order Isopoda Isopoda is an order of crustaceans. Members of this group are called isopods and include both aquatic species and terrestrial species such as woodlice. All have rigid, segmented exos ...

. It inhabits seashores in southern Africa and on some oceanic islands.

Description

''Deto echinata'' is distinguished by a pair of long curved "horns" situated on the back of each segment of the

thorax The thorax (: thoraces or thoraxes) or chest is a part of the anatomy of 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 di ...

. These horns are substantially longer in males than in females. Horn length in males has been found to be correlated with body condition, and it is hypothesized that this

sexual dimorphism Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...

acts as an indicator of overall fitness and is the result of

sexual selection Sexual selection is a mechanism of evolution in which members of one sex mate choice, choose mates of the other sex to mating, mate with (intersexual selection), and compete with members of the same sex for access to members of the opposite sex ...

. Colouration is dark brown on the back, lighter brown in patches, underneath and on the extremities. Males have an average length of 30 mm, females of 22 mm, making the species one of the largest in the suborder.

Distribution

The species occurs on the coast of southern Africa, having been recorded in

Namibia Namibia, officially the Republic of Namibia, is a country on the west coast of Southern Africa. Its borders include the Atlantic Ocean to the west, Angola and Zambia to the north, Botswana to the east and South Africa to the south; in the no ...

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...

and

Mozambique Mozambique, officially the Republic of Mozambique, is a country located in Southeast Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi and Zambia to the northwest, Zimbabwe to the west, and Eswatini and South Afr ...

. It can also be found on

Île Amsterdam (), also known as Amsterdam Island or New Amsterdam (), is an island of the French Southern and Antarctic Lands in the southern Indian Ocean that together with neighbouring Île Saint-Paul to the south forms one of the five districts of the t ...

and

Île Saint-Paul is an island forming part of the French Southern and Antarctic Lands (, TAAF) in the Indian Ocean, with an area of . The island is located about south of the larger Île Amsterdam , northeast of the Kerguelen Islands, and southeast of Réuni ...

in the southern Indian Ocean. It inhabits the

intertidal zone The intertidal zone or foreshore is the area above water level at low tide and underwater at high tide; in other words, it is the part of the littoral zone within the tidal range. This area can include several types of habitats with various ...

, where it occurs on or under rocks, generally associated with kelp and other organic drift material.

Ecology

''Deto echinata'' is placed in the suborder Oniscidea, the

woodlice Woodlice are terrestrial isopods in the suborder Oniscidea. Their name is derived from being often found in old wood, and from louse, a parasitic insect, although woodlice are neither parasitic nor insects. Woodlice evolved from marine isopods ...

, a group of crustaceans that is adapted to terrestrial rather than aquatic habitats. The species spends its life on shore, feeding mainly on drift algae and other washed-up plant material but also on carrion and small live prey. Where their ranges overlap in western South Africa, individuals are commonly mixed in with groups of the generally much more numerous, distantly related ''

Ligia dilatata ''Ligia dilatata'' is a woodlouse in the family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for ...

''.

References

{{Taxonbar, from=Q2752789 Isopoda Crustaceans described in 1836 Crustaceans of South Africa