To place the Hermit Crabs and their relatives in taxonomic
perspective let's do a/the usual rundown on their systematics starting from the:
Subphylum Crustacea:
About 42,000
species of some of the most familiar arthropods; crabs, shrimps, lobsters, crayfish,
wood-lice (sow-bugs, rolly-pollies, you know, terrestrial isopods, and aquatic, even
parasitic marine ones). Many small members in fresh and marine habitats of importance in
aquatic food chains. Primarily aquatic, mostly marine.
Some common characteristics of the crustaceans: 1) Their
heads are more or less uniform with five pair of appendages: they have two pair of
antennae (this feature is distinctive within the phylum); the third pair as opposing,
biting, grinding mandibles. Behind the mandibles there are two pair of accessory
feeding appendages, the first and second maxillae. 2) Their bodies trunks are composed of
distinct segments covered by a chitinous exoskeleton strengthened by deposition of
calcium salts. 3) Crustacean appendages are typically biramous (two major elements).
4) They typically have a carapace covering the trunk of their bodies. Enough of this
detail. We'll cover this stuff in more general survey pieces of the mega-groups. On toward
the lobsters.
A systematic resume of the Crustacea is
necessarily large and complex. Allow me to semi-skirt around a full discussion here. The
nine Classes that don't include our family of interest enclose the primitive
cephalocaridans (C. Cephalocarida), the Class Branchiopoda (fairy shrimps, tadpole
shrimps, water fleas (Daphnia); the Class Ostracoda, Class Copepoda (Anchor worm, Lernaea),
Classes Mystacocarida, Branchiura, Tantulocarida, Remipedia, Cirripedia (barnacles), whew!
& finally, our:
Class Malacostraca:
Comprises almost three-fourths of all described species of crustaceans and most of the
larger forms, such as crabs, lobsters, and shrimps. Characteristics: Trunks
typically composed of 14 segments plus the telson ("tail"); the first 8 segments
form the thorax, the last 6 the abdomen; all segments bear appendages. Four
Superorders: Syncarida, Hoplocarida, Peracarida, and the one we want to talk about, the
Eucarida.
Superorder Eucarida contains many of the
large malacostracans. They have highly developed carapaces displaying fusion of all
thoracic segments (the cepahalothorax). Eyes are stalked... Two living orders; the
Euphausiacea (krill) and the:
Order Decapoda includes
the familiar shrimps, crayfish, lobsters and crabs. This is the largest order of
crustaceans with @10,000 species. Decapods are distinguishable from euphausiaceans and
other malacostracans in that their first three pair of thoracic appendages, The remaining
five pairs are legs (Decapoda= "ten feet"). Decapods are further divided into two Suborders,
the Dendrobranciata, with "tree-like" branched gills, body laterally
compressed..., eggs planktonic, nauplius as the first larval stage (as in Artemia,
our brine shrimp), Infraorders, Sections, Superfamilies... See Barnes re their
higher taxonomy.
Of animals that are Crabs ("false" and true) there
are about eight thousand described species, with about 600 venturing into or
living in freshwater.
Infraorder Anomura, families of Hermit
Crabs, Sand or Mole Crabs, Crab-like Crustaceans. Depressed carapaces, third pair of legs never
chelate, fourth and fifth pair reduced.... Have a soft abdomen... live
with bodies enclosed in discarded shells for the most part.
Superfamily Galatheoidea
Family
Chirostylidae
Family Galatheidae (squat lobsters)
Family
Porcellanidae (porcelain crabs)
Superfamily Hippoidea
Family
Albueidae (mole crabs)
Family Hippidae
(sand crabs)
Superfamily Paguroidea, have oval carapaces, usually asymmetrical.
Live either in shells or with abdomen tucked underneath. First pair of legs as
chelipeds. Includes the Hermit Crab genera: Pomatocheles, Petrochirus,
Clibanarius, Coenobita (land Hermit Crab), Pagurus, Pylopagurus, Birgus (the
Coconut Crab), Stone Crabs like Lithodes, Paralithodes (commercial King Crab of
the North Pacific).
| Unusual find: a dead Hermit Crab found lying on coral in
Fiji. |
 |
Best (most "Reef-Safe") Hermit Crab Species (though no
carte-blanche guarantees) for Algae Control: Even these cannot be absolutely
trusted with small fishes, invertebrates if hungry... and they too can be meals
for... Puffers, Triggerfishes, Stomatopods (Mantis), Alpheids (Pistol Shrimp)...
| Calcinus laurentae Haig & McLaughlin 1983,
Laurent's Hermit Crab, Family
Diogenidae. Orange-yellow antennae. Claw-limbs brown, other legs pink with
white junctions and black tips. Hawaiian endemic. Common. To about
1/5" carapace length. Kona pic. |
 |
| Calcinus tibicen, the Orangeclaw Hermit Crab, Family
Diogenidae. Tropical West Atlantic. Orange antennae and eyestalks. Eye tips white, eyes with black
pupils. Unequal size claws. 1/2 to 1". |
 |
| Clibanarius tricolor, the Blue-Legged Hermit Crab. To
less than an inch in length. One of a few "reef-safe"
Hermits that stay small and almost exclusively feed on algae (and
Cyanobacteria!). Good for aiding in aerating the substrate as well.
Aquarium photo. |
 |
| Clibanarius digueti, a Mexican Hermit Crab, aka the
Blue-Eyed Spotted Hermit. To less than an inch in length. |
|
| Clibanarius seurati
Fiji |
 |
|
Clibanarius vittatus,
a common Gulf of Mexico hermit crab. Very hardy... can live out of water
for days at times. "*C.
vittatus* does get rather large, 10 cm at least
(Adam J. said he had one (actually, he said it was
*P. holthuisi* in a 6" shell)" Scott Allen Rauch
pic. |
 |
Bigger PIX:
The images in this table are
linked to large (desktop size) copies. Click on "framed" images to go to
the larger size. |
|
 |
| Paguristes cadenati Forest 1954, the Scarlet Reef
Hermit. Tropical West Atlantic. To one inch in length. Red carapace and
legs, eyes green, on yellow stalks. Aquarium and Cozumel photo. |
  |
| Never entirely "reef safe"... All hermits are to
degrees opportunistic omnivores... they WILL eat
your other livestock if hungry... Here two
Paguristes cadenati are "riding" a snail...
|
 |
Bigger PIX:
The images in this table are linked to large (desktop
size) copies. Click on "framed" images to go to the larger size. |
 |
| Phimochirus holthuisi, the Red-striped Hermit Crab.
Tropical West Atlantic. To one inch in length. One cheliped enlarged
(usually right); movable pincer white. Eyestalks white with dark band, eyes grayish blue. |
|
| Phimochirus opercularis, the Polka-Dot Hermit Crab. |
|
| Trizopagurus (Ciliopagurus)
strigatus (Herbst 1804), the Striped or
Halloween Hermit Crab. Indo-Pacific and Red Sea. To a little over two
inches in length. Nocturnal. Lives in empty Cone shells. Feed on live
and dead animal material. |
 |
Other Species of Hermits Sometimes Offered
in the Interest that are Unusual, though not highly suitable for
Aquarium use.
Other Species of Hermits Sometimes Offered in the Interest that are
TROUBLE: For (large) fish-only systems.
| Aniculus hopperae McLaughlin & Hoover 1996,
Hopper's Hermit Crab. Sometimes imported
from Hawai'i. Not a hardy aquarium species; apparently a sponge feeder in
the wild. To an inch in length. Black eyes, yellow eye stalks, bright
red claws bear black tips. Hawaiian endemic. Big Island pic. |
 |
| Aniculus maximus, a Large Hermit Crab. Often imported
from Hawai'i. To four inches in length. |
|
| Dardanus gemmatus
H. Milne-Edwards 1848,
Jeweled
Anemone Hermit Crab. To two inches
carapace length. With Calliactis anemones on its
shell. Hawai'i image. |
 |
| Dardanus lagopodes (Forsskal 1775), the Blade-eyed
Hermit Crab. Indo-Pacific, including the Red Sea. To a little over two
inches in length. White eye stalks, body mottled in maroon, brown, covered
with white-tipped bristles. This one in Aitutaki, Cook Islands and N.
Sulawesi. |
  |
| Dardanus megistos (Herbst 1789), Shell-Breaking Reef Hermit Crab,
often sold as the White Spotted. Members of this genus are predaceous, and
will gladly consume any fishes they can get their claws on. To six inches. Place with large,
aware fishes only. Aquarium and N. Sulawesi pix. |
  |
| Bigger PIX: The images in this table are linked to large (desktop size) copies. Click on "framed" images to go to the larger size. |
 |
| Dardanus pedunculatus
(Herbst
1804), another Reef Hermit Crab. Indo-Pacific. Often with anemones
placed on its movable home/shell. To a little over two inches in length.
Spiny chelipeds, red and white striped eye stalks are definitive. Aquarium
and N. Sulawesi pix. |
  |
| Dardanus tinctor, a Coral Hermit Crab. This one with
its Calliactis polypus Anemones out at night in the Red Sea.
To 10 cm. Large left claw. Nocturnal; omnivorous. Moves anemones when
transferring to new shells. |
 |
| Dardanus venosus, the Starry-eyed Hermit Crab. 3-5
inches. Blue/green eyes, dark pupils that are star-burst like in close
view. Claws of lavender color generally. Bristly. Cozumel pic. |
 |
| Paguristes puncticeps,
White Speckled Hermit Crab.
|
|
| Petrochirus diogenes, a Giant Hermit Crab. To twelve
inches (not a mis-print). Caribbean. |
|
The Superfamily Paguroidea also includes Stone Crabs like Lithodes, Paralithodes (commercial King Crab of
the North Pacific).
| Lithodes
SIO Aquarium image. |
 |
Care Notes:
If you use them, place about one, two small Hermits per actual gallon of your
system. Use a mix of species and make sure and provide many "upgrade"
homes (empty shells) for your Hermits to move to.
Bibliography/Further Reading:
Systematics of Crustacea:
http://www.dnr.state.sc.us/marine/sertc/Martin%20&%20Davis.pdf
http://www.marbef.org/data/ermstaxdetails.php?id=106685
http://animaldiversity.ummz.umich.edu/site/accounts/classification/Anomura.html#Anomura
Baensch, Hans & Helmut Debelius. 1994. Marine Atlas, v.1. MERGUS,
Germany. 1215pp.
Brawer, Marc. 1970. Hermit Crabs. Marine Aquarist 1:6, 70.
Burgess, Warren E. 1974. Salts from the seven seas (on Hermits). TFH 11/74.
Debelius, Helmut. 1999. Crustacea of the World. Atlantic, Indian, Pacific
Oceans. IKAN, Germany 321pp.
Friese, U. Erich. Crustaceans in the home aquarium. Hermit Crabs. TFH 4/85.
Hoover, John P. 1997. Hawaiian Hermit Crabs, pts. I,II. FAMA 9,10/97.
Jensen, Christopher. 1998. Red Legged Hermit Crab. FAMA 4/98.
Menten, Bob. 1980. The Hermit Crab. Marine scavenger- par excellence. TFH
11/80
Michael, Scott. 1998. Hermit danger. Some species of hermit crabs actually
consider your fish their dinner. AFM 5/98.
