Crayfish Dissection

Crayfish Dissection


Crayfish dissection. After completing this
video, you should be able to, one, name the
origins of the crayfish; two, identify the features
that serve as adaptations for crayfish living in
aquatic habitats; and, three, demonstrate the
correct procedure for dissecting a crayfish. To complete this lab, you’ll
need the following materials– personal protective
equipment, dissection tools and pan, crayfish
specimen, and camera for documenting your work. Before you begin, place
a small but legible piece of paper with your name and
the date of the dissection next to your specimen. Include this paper with any
images taken of your specimen. Observe the external
anatomy of your crayfish. Locate the head,
cephalothorax, and abdomen. Observe the carapace and
then the ventral surface of the crayfish as directed in
the learning unit instructions. Begin the dissection by
cutting up the exoskeleton from the tail to the eyes. Make sure your cuts
are shallow so as not to cut into internal organs. The scissors should be
parallel to the exoskeleton. Hold the exoskeleton up
and cut just underneath it, with only the point
of the scissors. Carefully detach the exoskeleton
from the muscle attachment underneath. Gently pull the
exoskeleton away. Once the carapace is removed,
locate and observe the gills. Take a picture of the gills. Move the walking
legs and notice how they are attached to the gills. This helps with
respiration and serves to move water across the gills. Observe that there are lots
of abdominal flexor muscles that can be viewed on the dorsal
side, flanking the intestine. Take a picture and label
the abdominal flexor muscle. In between this muscle
is the intestine, a long tube that runs along
the abdomen to the stomach. Take a picture and
label the intestine. Locate the heart, just
underneath the carapace and positioned
around the posterior portion of the cephalothorax. Take a picture and
label the heart. The cream-colored structures
beneath and slightly posterior to the heart are the gonads. Locate the stomach in the
head region above the mouth. It’s large, sack-like, and
joins to the intestine. Remove the digestive glands– yellowish-green structures
above the gonads– to view this. Take a picture and
label the stomach. Locate the green
antennal glands, anterior to the stomach at the
base of the antenna. These are primitive
excretory organs that remove metabolic
waste and excess water. Take a picture and
label the green glands. The ventral nerve cord
is a thin, white thread, similar to the spinal cord. Nerves fuse into the nerve
cord at the posterior side of the brain. The nerve cord runs along
the midline of the crayfish. The brain is found just
anterior to the green glands. It’s a small white mass
between the eyestalks. In conclusion, you
should have learned that the crayfish displays
bilateral symmetry and a high degree
of cephalization with its many
sensory structures. The crayfish is well
adapted for life in an aquatic environment
with its feathery gills. Its walking legs are
attached in a way so as to move water
over the gills when the organism is moving. The crayfish uses
its legs, tail, and swimmerets for locomotion
and has a segmented body.

local_offerevent_note February 27, 2020

account_box Gilbert Heid


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