''Libinia ferreirae'' is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of tropical spider crab 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 social order. Ideally, families offer predictabili ...

Epialtidae Epialtidae is a family 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 e ...

. It is found on the

seabed The seabed (also known as the seafloor, sea floor, ocean floor, and ocean bottom) is the bottom of the ocean. All floors of the ocean are known as seabeds. The structure of the seabed of the global ocean is governed by plate tectonics. Most of ...

in shallow waters off the Atlantic coast of South America.

Description

Like other spider crabs, ''Libinia ferreirae'' has a roughly circular spiny

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 ...

that extends forwards into a rostrum between the two, stalked eyes. It has five pairs of walking limbs.

Distribution

''Libinia ferreirae'' is found off the Atlantic coast of South America in the intertidal zone and at depths down to about . The range extends from

Venezuela Venezuela, officially the Bolivarian Republic of Venezuela, is a country on the northern coast of South America, consisting of a continental landmass and many Federal Dependencies of Venezuela, islands and islets in the Caribbean Sea. It com ...

and the

Guianas The Guianas, also spelled Guyanas or Guayanas, are a geographical region in north-eastern South America. Strictly, the term refers to the three Guianas: Guyana, Suriname, and French Guiana, formerly British Guiana, British, Surinam (Dutch colo ...

, through parts of

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

Uruguay Uruguay, officially the Oriental Republic of Uruguay, is a country in South America. It shares borders with Argentina to its west and southwest and Brazil to its north and northeast, while bordering the Río de la Plata to the south and the A ...

Biology

The larvae of ''Libinia ferreirae'' are planktonic and have one prezoeal stage, two

zoea Crustaceans may pass through a number of larval and immature stages between hatching from their eggs and reaching their adult form. Each of the stages is separated by a moult, in which the hard exoskeleton is shed to allow the animal to grow. The ...

l stages and one

megalopa Crustaceans may pass through a number of larval and immature stages between hatching from their eggs and reaching their adult form. Each of the stages is separated by a moult, in which the hard exoskeleton is shed to allow the animal to grow. The ...

stage. The carapace of the zoea has one short rostral and one curved dorsal spine and some of the abdominal segments have spiny projections. The post-larval megalopa has a downturned rostrum, a carapace with various protuberances and four pairs of abdominal appendages.

Ecology

''Libinia ferreirae'' is often found in association with the jellyfish, ''

Lychnorhiza lucerna ''Lychnorhiza lucerna'' or Marbled Jelly is a species of jellyfish in the order Rhizostomeae. It is found off the Atlantic coasts of South America. Description When small, ''Lychnorhiza lucerna'' has a hemispherical bell, but this becomes flatt ...

''. Juvenile crabs are found living within the bell, on the oral arms or clinging to the exterior, even on jellies that have been stranded on the shore. The crabs are mostly less than in diameter and probably colonized the jellyfish when they were larvae. The number of jellyfish acting as host is low but increases with the size of the jellyfish and the inhabited ones mostly house a single crab. The crab may be immune to or able to tolerate the jellyfish stings. It is thought that the crab benefits from using the jellyfish as a nursery because free-living, young crabs are eaten by

predatory 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 feeding behaviours that includes parasitism and micropredation (which usually do not kill ...

fish. Other benefits of this arrangement to the crab are a potential increase in food supply and transport to new locations. There do not seem to be any benefits to the jellyfish and the arrangement may be deleterious to it if the crab nibbles its interior tissues, as happens in some other crab/jellyfish relationships. At some stage the crab emerges from the bell and falls to the sea bed. Adult ''Libinia ferreirae'' often have faunal

epibiont An epibiont (from the Ancient Greek meaning "living on top of") is an organism that lives on the surface of another living organism, called the basibiont ("living underneath"). The interaction between the two organisms is called epibiosis. An ep ...

s growing on their carapace. These include

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 ...

polychaete Polychaeta () is a paraphyletic class of generally marine Annelid, annelid worms, common name, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called c ...

worms,

sea anemone Sea anemones ( ) are a group of predation, predatory marine invertebrates constituting the order (biology), order Actiniaria. Because of their colourful appearance, they are named after the ''Anemone'', a terrestrial flowering plant. Sea anemone ...

barnacle Barnacles are arthropods of the subclass (taxonomy), subclass Cirripedia in the subphylum Crustacean, Crustacea. They are related to crabs and lobsters, with similar Nauplius (larva), nauplius larvae. Barnacles are exclusively marine invertebra ...

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 and

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, ...

. The most common species growing on the carapace was the sea anemone, '' Calliactis tricolor'', which seems to be used by the crabs as

camouflage Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard's spotted coat, the b ...

. Bryozoans colonised the legs as well as the carapace.

References

{{Taxonbar, from=Q13400675 Majoidea Crustaceans of Brazil Crabs of the Atlantic Ocean Taxa named by Félix António de Brito Capello Crustaceans described in 1871