Mactan Island, The Philippines
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A Female crab (left) and a Male crab (right)
Below, a commonly found Xanthid species living within live rock.
Below, yet another rock living Xanthid species.
Below is a Xanthid species found on Acropora corals and assume they prey upon the corals polyps or tissue.
Various other Xanthid species.
The Mithrax Crabs ( Cling Crabs) None of which I would consider to be reef safe, members of this family include the popular "emerald" crabs that are used for algae control, which may be fine for awhile, but with all crabs being omnivores, it is usually only a matter of time before these crabs discover that there are meatier items to be had within your aquarium.
The Porcellanidae Crabs Photo Link #2 Photo Link #3 Can be considered Reef Aquarium Safe
The Anomuran crabs, part of the Porcellanidae family, relatives of Petrolisthes and Porcellanella.
The Galatheid Crabs - Also known as squat lobsters for their appearing very lobster like. All of the species that I have found on live rock have been very small and seem to be somewhat harmless, although they may feed upon small sessile invertebrates.
The Allogalatheid Crabs - also known as squat lobsters but only lives on crinoids. Color patterns usually consists of alternating dark & light colored bands with white leg tips & claws; the colors always match the host crinoid. They are klepto-parasites that don't directly harm the host but steal its food.
The Dromiidae Crabs - Specializes in carrying sponges and even zoanthids as a means of camouflage, it does so by means of its last set of legs which are modified to grasp onto its captive audience. I have had this specimen drop its sponge and snip out a square inch section of zoanthids off of their rock and form the zoanthids into the same shape as the sponge pictured below. I have seen others on the reef slopes carrying about both sponges and zoanthids in this manner.
The Portunidae ( Swimming Crabs) Note the paddle shaped last pair of legs.
Below: A Lissocarcinus laevis, a symbiont of sea anemone.
Below: Various other species
The Majoidea SuperFamily ( spider crabs / decorator crabs)
Below: Xenocarcinus tuberculatus A member of the Pisidae family
Below: Achaeus japonicus
Below: Various other unknown species
The Parthenopidae Family, commonly called the elbow crabs. Below is a possible Daldorfia horrida.
Below, possibly ajuvenile Daldorfia glasselli.
The Calappa Crabs ( box crabs )
Gravid Female Ready to hatch eggs Two day old Larvae
The Leucosiidae Crabs ( Pebble Crabs)
Below, a member of the Leucosia genus
The Cryptochirid Crabs ( Gall Crabs )
The Pinnotheridae Crabs ( Pea Crabs) - Pea crabs are commensals that associate with various echinoderms, molluscs, polychaetes, brachiopods, etc. Some are external while many of them are internal living inside their hosts' gill chambers or body cavities. (photos by Beth LeBlanc)
The Stenorhynchus Crabs ( arrow crabs ) Normally not considered reef aquarium safe
Click Links to view photographic detailsSpecimen #1 Specimen #2 Specimen #3
Specimen #4 Specimen #5 Specimen #6
Trapezia rufopunctata Tetralia nigrolineata Tetralia cymodoce
Specimen #7 Specimen #8 Specimen #9
Trapezia guttata Trapezia serenei Tetralia nigrolineata
Specimen #10 Specimen #11 Specimen #12
Cymo andreossyi : Very common and is considered a coral symbiont, with the caveat that such symbiosis are a trade off between the coral and the crab, the coral gains protection and house cleaning services while giving up a few polyps, mucus and captured/settled food particles in exhange for those services. A healthy coral should have no problem repairing or replacing lost polyps, but again, in an aquarium environment, an eye should be kept on the coral for excessive damage being done due to the coral being unable to recover as fast or faster than the damage being done by the crab. In short, its a judgement call that you will have to make.
Trapeziid Crabs of New Caledonia, Eastern Australia and the Coral Sea
Curator of Fish and Invertebrates Biological Sciences Department
Aquarium of the Pacific in Long Beach Ca. California State Polytechnic University
Download a .pdf version of the publication shown below
Every Crab in the World
(click above link)
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without permission of the authors.
Used by permission. Many thanks to Charlies and Linda Raabe for their support. www.chucksaddiction.com