11
uropods. The opening to the mouth is
flanked by several pair of maxillipeds
which chop their food into small pieces.
At right is a photo of the underside of a
female showing the seminal receptacle or
annulus ventralis. This is a blind pocket
that is used to store semen. Ahead of this, at
the base of the third pair of walking legs are
the openings for the oviducts.
INTERNAL ANATOMY
Below is a basic illustration of the internal
anatomy of a crayfish showing the major
organ systems. [For more detailed
information, please refer to Felgenhauer
62
or
Schramm et.al.
206
]
The digestive system consists of a foregut,
midgut and hindgut. The foregut has two
parts, the esophagus and stomach.
Digestion begins at the mouth where the
mouth parts, the maxillipeds, shred the food
items and feed them into the esophagus and
the stomach. The stomach has two
chambers. The larger front chamber is the
cardiac stomach and the smaller rear
chamber is the pyloric stomach. On either
side of the cardiac stomach are pouches
where the gastroliths form and are
dissolved during a molt. Between the two
stomachs is a gastric mill consisting of a set
of three chitinous teeth that grind the food
into mush. Just behind the gastric mill is a
filter that stops any food items that are too
large to digest (these are reground or spit
out). In the pyloric stomach, the food is
mixed with digestive enzymes from the
hepatopancreas. The hepatopancreas is a
complex organ that produces digestive
enzymes and fat emulsifiers which also
absorbs and stores food and minerals. After
passing back and forth between the pyloric
stomach and the hepatopancreas several
