Page 303 - (DK) Ocean - The Definitive Visual Guide

ARTHROPODS 301

Unlike most crabs, the blue swimming Resting in the cool of its burrow
SUBPHYLUM CRUSTACEA SUBPHYLUM CRUSTACEA
crab is an excellent swimmer and uses during the day, the fast-moving
Blue Swimming its fourth pair of flattened, paddlelike Ghost Crab ghost crab emerges at twilight
to hunt. It will eat anything it can
legs to propel itself through the water.
Crab Despite its common name, only the Ocypode saratan find, including other crabs, and also
males are blue, and the females are LENGTH scavenges whatever was brought in
a rather dingy greenish brown. Males About 1 / 2 in (3.5 cm) by the last tide. During the mating
Portunus pelagicus 1
LENGTH also differ in having very long claws, HABITAT season, males defend their burrows,
Up to 2 / 4 in (7 cm) Sandy shores in deep
3
more than twice as long as the width but they rarely fight, any disputes
HABITAT of their carapace. The claws are armed burrows above the being settled by ritualistic displays.
Intertidal sandy or water line
muddy sea beds to 180 ft with sharp teeth that are used to snag Their burrows can be over 330 ft
(55 m) small fish and other food items. DISTRIBUTION Coastal waters of western (100 m) from the sea and
When a blue swimming crab feels Indian Ocean, Red Sea over 3 ft (1 m) deep.
DISTRIBUTION Coastal waters of the Indian and threatened, it usually buries itself in
Pacific oceans, eastern Mediterranean
the sand. If this measure fails to deter
the threat, the crab
adopts its own threat
stance, extending its
claws sideways in an
attempt to look as large
as possible. The natural
range of this crab has
been extended to a
small part of the eastern
Mediterranean by the
opening of the Suez
Canal. It is a popular
food in Australia.
is greatly enlarged. In a mature adult
SUBPHYLUM CRUSTACEA
this claw makes up more than half the RITUAL DISPLAY
Orange Fiddler Crab crab’s body weight and is used both to
attract potential mates and to ward off Each species of fiddler crab waves
rival males. Observing the distinctive
Uca vocans its claw in a slightly different way. If
“courtship wave” of fiddler crabs is
LENGTH this ritual movement does not deter
About 1 in (2.5 cm) helpful in identifying different species. a rival male, then two crabs may
Orange fiddler crabs are active
HABITAT “arm-wrestle” each other
Near water on mud or during the day. As well as digging a to resolve their dispute. The
sand main burrow up to 12 in (30 cm) deep, weaker individual usually
they create a number of bolt holes retreats before any serious
into which they can retreat if danger
DISTRIBUTION Indian Ocean and western Pacific damage is done.
threatens. At high tide, they seal
Like its close relative the ghost crab themselves into their burrows with a
LEFT- OR RIGHT-HANDED?
(see above, right), the male orange small pocket of air. The presence of air Both crabs in this picture are right-
fiddler crab also exhibits ritualistic is essential for their survival because handed, but in some males it is the
displays to deter rivals. Males are easily fiddler crabs obtain oxygen from air, left claw that is enlarged (see below).
recognized because one of their claws not water, despite having gills. OCEAN LIFE