87
omnivores. They eat everything, including filtering phytoplankton, grazing algae,
invertebrates, and animal meats (Hollows 2016). Crayfish mostly prefer live foods.
They do not want to eat stinking foods or dead animal wastes unless they are very
hungry. But they eat everything that can be eaten in food difficulty (Alpbaz 2005).
The body of a decapod crustacean, such as a crab, lobster, or prawn, is made up
of 19 body segments grouped into two main body parts, the cephalothorax, and the
abdomen. Each segment may possess one pair of appendages, although in various
groups these may be reduced or missing. The cephalothorax is covered by a carapace, which protects the internal organs and the gills; the section of the carapace
that projects in front of the eyes is called the rostrum. Crayfish have two pairs of
sensory antennae on the head, and the eyes are on movable stalks. On the thorax or
pereon, there are four pairs of walking legs (pereiopods) and one pair of pereiopods
(chelipes) armed with a claw (pinchers). On the abdomen, or pleon, there are pleopods (also called swimmerets), which are primarily swimming legs. At the end of
the pleon is the tail fan, comprising a pair of biramous uropods and the telson, which
bears the anus. Together, they are used for steering while swimming, and in the
caridoid escape reaction. When they are in danger and need to flee, crayfish can
swim backwards quickly by curling and uncurling their abdomen. They breathe
through feather-like gills predators (New World Encyclopedia 2019).
Crayfish live in rivers, lakes, streams and even marshes. They are often housed
on gravelly bottoms, under flat stones or in shallow pits. They love hollow, abundant
vegetation, stony and slime-free waters. If the soil is not too hard, they will make a
nest by carving the soil using their tails with digging movements. The crayfish lie in
their nests leaving their clamps out and easily observing their enemies. Crayfish
normally have a slow and shaky walk. They walk forward using their walking legs.
But they swim backwards. Crayfish generally like abundant calcareous and discharge waters. Limestone helps the development of the shell (Alpbaz 2005).
Some Species of Crayfish
There are two centres of species diversity of freshwater crayfish. The first is in the
South-eastern United States. The second centre is Victoria, Australia. Crayfish naturally occurs on all of the continent except Africa and Antarctica. The Astacidae are
distributed in Europe, US, British Colombia, and Canada. The Cambaridae are
found in the Eastern United States and South Mexico. Parastacidae are distributed
in Australia, New Guinea, New Zealand, South America and Madagascar (SoutyGrosset and Fetsner 2016).
Species used for economic income are mainly Procambarus clarkii, Pacifastacus
leniusculus, Cherax destructor, C. quadricarinatus, Orconectes limosus, O. rusticus and Astacus leptodactylus. Among these species, Procambarus clarkii can be
found in Africa, Asia, America, California and Europe; Procambarus leniusculus to
California in Japan, Europe and America; C. destructor in Africa and Australia;
C. quadricarinatus was transported to South America, O. rusticus to North America,
and A. leptodactylus was transported from Europe to the natural environment.
2.3 Lobsters
omnivores. They eat everything, including filtering phytoplankton, grazing algae,
invertebrates, and animal meats (Hollows 2016). Crayfish mostly prefer live foods.
They do not want to eat stinking foods or dead animal wastes unless they are very
hungry. But they eat everything that can be eaten in food difficulty (Alpbaz 2005).
The body of a decapod crustacean, such as a crab, lobster, or prawn, is made up
of 19 body segments grouped into two main body parts, the cephalothorax, and the
abdomen. Each segment may possess one pair of appendages, although in various
groups these may be reduced or missing. The cephalothorax is covered by a carapace, which protects the internal organs and the gills; the section of the carapace
that projects in front of the eyes is called the rostrum. Crayfish have two pairs of
sensory antennae on the head, and the eyes are on movable stalks. On the thorax or
pereon, there are four pairs of walking legs (pereiopods) and one pair of pereiopods
(chelipes) armed with a claw (pinchers). On the abdomen, or pleon, there are pleopods (also called swimmerets), which are primarily swimming legs. At the end of
the pleon is the tail fan, comprising a pair of biramous uropods and the telson, which
bears the anus. Together, they are used for steering while swimming, and in the
caridoid escape reaction. When they are in danger and need to flee, crayfish can
swim backwards quickly by curling and uncurling their abdomen. They breathe
through feather-like gills predators (New World Encyclopedia 2019).
Crayfish live in rivers, lakes, streams and even marshes. They are often housed
on gravelly bottoms, under flat stones or in shallow pits. They love hollow, abundant
vegetation, stony and slime-free waters. If the soil is not too hard, they will make a
nest by carving the soil using their tails with digging movements. The crayfish lie in
their nests leaving their clamps out and easily observing their enemies. Crayfish
normally have a slow and shaky walk. They walk forward using their walking legs.
But they swim backwards. Crayfish generally like abundant calcareous and discharge waters. Limestone helps the development of the shell (Alpbaz 2005).
Some Species of Crayfish
There are two centres of species diversity of freshwater crayfish. The first is in the
South-eastern United States. The second centre is Victoria, Australia. Crayfish naturally occurs on all of the continent except Africa and Antarctica. The Astacidae are
distributed in Europe, US, British Colombia, and Canada. The Cambaridae are
found in the Eastern United States and South Mexico. Parastacidae are distributed
in Australia, New Guinea, New Zealand, South America and Madagascar (SoutyGrosset and Fetsner 2016).
Species used for economic income are mainly Procambarus clarkii, Pacifastacus
leniusculus, Cherax destructor, C. quadricarinatus, Orconectes limosus, O. rusticus and Astacus leptodactylus. Among these species, Procambarus clarkii can be
found in Africa, Asia, America, California and Europe; Procambarus leniusculus to
California in Japan, Europe and America; C. destructor in Africa and Australia;
C. quadricarinatus was transported to South America, O. rusticus to North America,
and A. leptodactylus was transported from Europe to the natural environment.
2.3 Lobsters