''Zebrida adamsii'' is a distinctively striped

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), ...

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 ...

that lives in association with a

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 ...

in the

Indo-Pacific The Indo-Pacific is a vast biogeographic region of Earth. In a narrow sense, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, it comprises the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the ...

region. It is cryptically coloured with vertical stripes and has special adaptations to its legs to enable it to cling to its host's spines.

Description

''Z. adamsii'' is a small crab, described as "a torpid, though elegant little crustacean" by the English naturalist Arthur Adams when it was first discovered by him and the Scottish zoologist Adam White during the surveying voyage of HMS ''Samarang'' in the Far East between 1843 and 1846. The

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 ...

and limbs are smooth and hairless and are adorned with long spines. The colour is pink with dark, reddish-brown vertical stripes.

Distribution

''Z. adamsii'' has a wide distribution in shallow water in the tropical Indian Ocean and western Pacific Ocean. The type locality is the estuary of the Pantai River in Borneo at a depth of about .

Ecology

''Z. adamsii'' lives in

symbiosis Symbiosis (Ancient Greek : living with, companionship < : together; and ''bíōsis'': living) is any type of a close and long-term biological interaction, between two organisms of different species. The two organisms, termed symbionts, can fo ...

with a sea urchin, living among its spines. Sea urchins on which it has been found include '' Asthenosoma ijimai'', ''

Diadema setosum ''Diadema setosum'' is a species of long-spined sea urchin belonging to the family Diadematidae. It is a typical sea urchin, with extremely long, hollow spines that are mildly venomous. ''D. setosum'' differs from other '' Diadema'' with five, c ...

'', ''

Heliocidaris crassispina ''Heliocidaris'' is a genus of sea urchins, part of the family Echinometridae. Characteristics This genus is typical of west Pacific Ocean (Japan to New Zealand), in particular in Australia. Some species are edible. List of species This gen ...

'', '' Pseudocentrotus depressus'', '' Salmacis bicolor'', '' Salmacis virgulata'', '' Toxopneustes elegans'', ''

Toxopneustes pileolus ''Toxopneustes pileolus'', commonly known as the flower urchin, is a widespread and commonly encountered species of sea urchin from the Indo-West Pacific. It is considered highly dangerous, as it is capable of delivering extremely painful and med ...

'', ''

Tripneustes gratilla ''Tripneustes gratilla'', the collector urchin or halloween urchin, is a species of sea urchin. Collector urchins are found at depths of in the waters of the Indo-Pacific, Hawaii, the Red Sea, and The Bahamas. They can reach in size. Descript ...

'' and a species of '' Acanthocidaris''. Adaptations for this lifestyle include a specialist joint between the propodus and

dactylus The dactylus is the tip region of the tentacular club of cephalopods and of the leg of some crustaceans (see arthropod leg). In cephalopods, the dactylus is narrow and often characterized by the asymmetrical placement of suckers (i.e., the vent ...

on the walking legs enabling the crab to cling to its

host A host is a person responsible for guests at an event or for providing hospitality during it. Host may also refer to: Places * Host, Pennsylvania, a village in Berks County * Host Island, in the Wilhelm Archipelago, Antarctica People * ...

, and cryptic colouring in the form of vertical stripes. Females are slightly larger than males and usually live singly on a sea urchin while males move from one urchin to another searching for females. ''Z. adamsii'' feeds on its host's

tube feet Tube or tubes may refer to: * Tube (2003 film), ''Tube'' (2003 film), a 2003 Korean film * "Tubes" (Peter Dale), performer on the Soccer AM#Tubes, Soccer AM television show * Tube (band), a Japanese rock band * Tube & Berger, the alias of dance/e ...

and on the epidermal tissue covering the

test Test(s), testing, or TEST may refer to: * Test (assessment), an educational assessment intended to measure the respondents' knowledge or other abilities Arts and entertainment * ''Test'' (2013 film), an American film * ''Test'' (2014 film) ...

and the base of the spines. This does little harm to the host which readily regenerates both the tissue and the tube feet. ''Z. adamsii'' larvae are

plankton Plankton are the diverse collection of organisms that drift in Hydrosphere, water (or atmosphere, air) but are unable to actively propel themselves against ocean current, currents (or wind). The individual organisms constituting plankton are ca ...

ic and pass through four

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 before settling on the seabed and undergoing

metamorphosis Metamorphosis is a biological process by which an animal physically develops including birth transformation or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and different ...

into juvenile crabs.

References

External links

* * {{Taxonbar, from=Q7938094 Pilumnoidea Crabs of the Indian Ocean Crabs of the Pacific Ocean Crustaceans described in 1847 Taxa named by Adam White (zoologist)