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Queensland has many species of this fascinating group of marine creatures that includes crabs, prawns, lobsters, mantis shrimps, hermit crabs, freshwater crayfishes, and many others.
Crustaceans constitute a subphylum of the Arthropoda, and are among the most successful animal groups, with at least 67,000 described species. They are as abundant in the oceans as insects are on land. It is estimated that tiny marine copepod crustaceans make up over half of all animals in the world by sheer numbers, and krill (the preferred food of some types of whales) have one of the greatest biomasses on the planet. As such, crustaceans are a crucial component of most marine food webs.
Crustaceans vary enormously in their sizes, shapes, and lifestyles - from transparent microscopic copepods, to the largest of all Australian arthropods, the Tasmanian Giant Crab (Pseudocarcinus gigas), which weighs up to 14kg, reaches nearly 40 centimetres in shell width, and has a claw as big as a human forearm. While predominantly marine, some crustaceans have also moved into fresh water, and a few groups have adapted to life on land, such as terrestrial crabs, terrestrial hermit crabs, woodlice (Isopoda) and leaf-hoppers (Amphipoda).
Despite their diversity of form, crustaceans are united by their special first larval form known as the nauplius, though in some groups larval stages can be very short-lived, and even take place within the egg before release. Crustaceans also differ from other arthropods (such as insects, spiders and other arachnids) by having two pairs of antennae (although one pair can sometimes be tiny). Most large crustaceans have well-developed gills, but some smaller species respire directly through the body wall. Like other arthropods, crustaceans have a stiff exoskeleton that must be molted to allow the animal to grow. This is a time when many crustaceans are particularly vulnerable to attack from predators, because their new larger shell still needs to harden into protective armour.
The crustacean subphylum includes:
It depends how you measure it! The Japanese Spider Crab (Macrocheira kaempferi) has the greatest leg span of any crustacean, extending almost 4 metres, and weighs the most – up to 19kg. However, the Tasmanian Giant Crab (Pseudocarcinus gigas) has a larger carapace, reaching 46 centimetres in width, as opposed to the spider crab’s 40 centimetres. The Tasmanian Giant Crab is also a close second on weight, with one specimen tipping the scales at 17.6kg.
No. While the majority of crustaceans such as crabs, prawns, and lobsters have a hard outer shell, some unusual crustaceans have no hard exoskeleton. For example, some parasitic barnacles such as Sacculina species live inside other crustaceans, and have no need for protective armour.
The major characteristic that unites crustaceans is the presence of a larval swimming stage known as a nauplius. In addition, most crustaceans possess two pairs of antennae, as opposed to insects, which have only one pair.
No. While most do, some notable groups live in freshwater and terrestrial environments. For example, Australia has many species of freshwater crabs and crayfishes. Other non-marine examples include shield shrimps, land hoppers, and slaters.
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