THE STEINHART AQUARIUM - Gulf of Guinea Science ...

74 A Docent Field Guide to the Species of the Steinhart Aquarium
Mortality/Longevity: Pacific halibut is a
known predator; probably other fishes,
cephalopods, and sea otters as well. Lives up
to several years.
Remarks: Masking or decorator crabs typically
add camouflaging items to their bodies by
attaching them to hook-like spines on the
carapace and legs. This strategy may conceal
the crabs from predators, prey, or both.
Northern Kelp Crab
Pugettia producta (Majidae)
Distribution: Alaska to Baja California.
Habitat: Rocky intertidal in kelp beds and tide
pools with abundant surfgrass or algae. The
crab uses the vegetation as protection from sun
and predators. Subtidal to 70 m.
Appearance: Mostly dark brown to green.
Color varies with diet depending on the
type of algae consumed, providing a natural
camouflage. Like other members of its family,
noted for its unique, elongated carapace with
extended rostrum and four pairs of relatively
long, slender walking legs. Because of these
features, the family common name is “spider
crabs.”
Diet: Mainly a nocturnal vegetarian feeding
on bull kelp, sea lettuce, rockweed and other
kelp. Occasionally will take barnacles, mussels,
hydroids, and bryozoans in winter when
vegetation is scarce.
Reproduction and Development: Females
usually mate June to July, though can mate
year round. Fertilized eggs develop for several
months underneath the female’s abdomen.
Mortality/Longevity: Preyed upon by sculpins,
gulls, cabezon, and sea otters among others.
Remarks: Most crabs in this family are called
masking crabs; they attach fragments of shells
and algae to their carapace for camouflage. P.
producta, a large active crab, maintains a clean
surface, perhaps for ease of movement.
P. producta is a feisty animal; long legs are
dextrous, and claws can pinch hard.
Orange Fiddler Crab
Uca vocans (Ocypodidae)
Distribution: Indo-Western Pacific: Madagascar,
South Africa to Thailand, Indonesia, Malaysia,
Philippines.
Habitat: Adults are semi-terrestrial, like all
fiddler crabs. Usually in or near mangrove
sandbanks. Prefer slightly sandier substrates
to mudbanks, burrows located in the intertidal
zone of both substrates.
Appearance: Carapace width to 2.5 cm. Strong
sexual dimorphism; males have one of their
chelae very greatly enlarged (the “fiddle”),
females dull colored with chelae equal and small.
Diet: Organic matter in the sand.
Reproduction and Development: Males gain
the attention of potential mates by waving
their enormous chela in a semaphore manner;
each species of Uca has a distinctive huge claw
movement pattern. The male also attracts a
female with acoustic signals by rapping the
propodus (elbow) of his claw against the
substrate or by rapid flexion of the walking
legs. The number of pulses (raps) in a series,
as well as the interval between every series,
is characteristic to each Uca species. Females
detect these acoustical signals in special organs
in their legs.
Remarks: When disturbed, quickly retreat into
a burrow, which may not be their own, or dig
a new one.
Males use their huge claw to defend their
burrow turf against other males. Male-to-male
combat is highly ritualized. The huge chela is
held like a shield. Combat involves variations
of pushing and extension.
Common Hermit Crab
Dardanus pedunculatus (Diogenidae)
Distribution: Indo-Pacific.
Habitat: Coral, rock or sand; depth to 40 m.
Likely the most common species of hermit crab
in the locations in which it occurs.
Appearance: To 10 cm. Spiny chelipeds,
light-colored bristles. Candy-cane white and
red-striped eyestalks, green eyes. Abdomen
protected by a recycled mollusk shell.
Diet: Algae, scavenger.
Remarks: Adults locate a prospective empty
home with their eyes and inspect it by inserting
one of their chelae into its interior. No real
estate agents are employed. If the shell seems
like a good fit on their “test drive,” they walk
away with their find. On the other hand, if the
fit, weight, or movability doesn’t suit, the crab
returns to its old, crowded shell with no qualms
about searching for other choices.