''Dorippe frascone'', the urchin crab or carrier crab, is a small species of

crab Crabs are decapod crustaceans of the infraorder Brachyura (meaning "short tailed" in Greek language, Greek), which typically have a very short projecting tail-like abdomen#Arthropoda, abdomen, usually hidden entirely under the Thorax (arthropo ...

in the family Dorippidae that was first described scientifically by J.F.W. Herbst, in 1785. It is found in the

Red Sea The Red Sea is a sea inlet of the Indian Ocean, lying between Africa and Asia. Its connection to the ocean is in the south, through the Bab-el-Mandeb Strait and the Gulf of Aden. To its north lie the Sinai Peninsula, the Gulf of Aqaba, and th ...

and parts of the western and eastern

Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or approximately 20% of the water area of Earth#Surface, Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia (continent), ...

. It often has a

symbiotic Symbiosis (Ancient Greek : living with, companionship < : together; and ''bíōsis'': living) is any type of a close and long-term biolo ...

relationship with a long-spined

sea urchin Sea urchins or urchins () are echinoderms in the class (biology), class Echinoidea. About 950 species live on the seabed, inhabiting all oceans and depth zones from the intertidal zone to deep seas of . They typically have a globular body cove ...

and carries one around on its

carapace A carapace is a dorsal (upper) 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 unde ...

Description

The urchin crab is a brownish-pink colour and grows to a length of about . It has long-stalked eyes, a rounded carapace and long, slender legs. It uses only the first two pairs of legs for locomotion because the third and fourth pairs are used to grip a sea urchin which it carries around on its back. It is similar in

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines *Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...

to the jellyfish crab ('' Ethusa'' spp.) but is easily distinguished by the different

invertebrate Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordata, chordate s ...

transported. It also resembles

decorator crab Decorator crabs are crabs of several different species, belonging to the superfamily Majoidea (not all of which are decorators), that use materials from their environment to hide from, or ward off, predators. They decorate themselves by stickin ...

s but those actually stick living creatures such as

sponge Sponges or sea sponges are primarily marine invertebrates of the animal phylum Porifera (; meaning 'pore bearer'), a basal clade and a sister taxon of the diploblasts. They are sessile filter feeders that are bound to the seabed, and a ...

hydroids Hydroids are a life stage for most animals of the class Hydrozoa, small predators related to jellyfish. Some hydroids such as the freshwater '' Hydra'' are solitary, with the polyp attached directly to the substrate. When these produce buds, ...

and

bryozoa Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals) are a phylum of simple, aquatic animal, aquatic invertebrate animals, nearly all living in sedentary Colony (biology), colonies. Typically about long, they have a spe ...

ns, bits of

algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...

and inert objects to their shells.

Distribution

''Dorippe frascone'' is found in the Red Sea and off the coast of East Africa, including

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 ...

and

Cargados Carajos Saint Brandon (), also known as the Cargados Carajos Shoals, is a southwest Indian Ocean archipelago of sand banks, shoals and islets belonging to the Republic of Mauritius. It lies about northeast of the island of Mauritius. It consists of fiv ...

, an atoll north east of

Mauritius Mauritius, officially the Republic of Mauritius, is an island country in the Indian Ocean, about off the southeastern coast of East Africa, east of Madagascar. It includes the main island (also called Mauritius), as well as Rodrigues, Ag ...

Ecology

The urchin crab is so called because of its habit of carrying a sea urchin on its carapace. This is usually the red urchin (''

Astropyga radiata ''Astropyga radiata'', the red urchin, fire urchin, false fire urchin or blue-spotted urchin, is a species of sea urchin in the Family (biology), family Diadematidae. It is a large species with long spines and is found in the tropical Indo-Pacific ...

''), the black long-spined urchin ('' Diadema setosum'') or the banded diadem urchin ('' Diadema savignyi''). All these urchins have long, hollow spines and may provide protection to the crab by reducing the risk of

predation Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...

by fish while not being too heavy to carry. The urchin obtains benefit by being transported to new feeding grounds. Even large and mobile individuals submit passively to being carried in this way.

References

External links

* {{Taxonbar, from=Q5297873 Crabs Crustaceans described in 1785