Evolutionary origin Attempts have been made to construct a single hypothetical crustacean ancestor. Such an organism would have to possess: elongated body, two pairs of appendages in front of the mouth, a pair of mandibles behind the mouth, and numerous trunk segments with appendages that form a continuous series of similar structure Cephalocarida is proposed as having a body plan from which all crustacean features could emerge Cephalocarida
The earliest crustacean fossils are ostrocods. There is evidence from the Burgess shales that many crustacean features had already evolved during the Cambrian Period (542 million to million years ago) Ostrocod fossil
Anatomy Haemocoel: The body cavity in which blood flows Sensory Organs: Compound eyes, statocysts (fluid filled cysts that sense direction of gravity), tactile hairs that respond to pressure or touch Respiration: Diffusion or gills Central nervous system: Brain and ventral nerve cord
Reproduction Crustacea produce from eggs which have been fertilized by sperm Most of the species are dioecious, there is a male and a female. Most species brood their eggs, meaning they have many eggs that hatch at the same time.
Habitat Crustacea live in: Oceans Fresh water Land Many crustaceans are nocturnal They spend their days hidden in a burrow, buried in the sand or sleeping in a crevice.
Diet carnivores or scavengers some are herbivores and detritivores few classify as parasites eat plants while some eat fish and other feed from the bottom of the ocean
Species of Crustacea There are many species of Crustacea known, 67000, many of these are used for human consumption
Semibalanus balanoides (Acorn Barnacle) Grow up to 15 mm Can produce up to 10,000 eggs Sessile No abdomen Feed using Cirri
Talitrus saltator (Sand Hopper) Compressed laterally Beach Fleas mm long Known for hopping patterns
Homarus americanus (Atlantic Lobster) cm kg Lives in cold shallow water Same Order as crabs Culinary Delicacy
Euphausia superba (Antarctic Krill) Grows to 6 cm in length Weigh up to 2 grams Most abundant species Bioluminescent