Dissections

Starfish Dissection:

Our species of starfish was an Ophiuroidea, which are brittle stars and basket stars. We begin by placing the starfish with it's aboral surface, which is covered with spines, facing upward. Start cutting into one of the arms of the starfish and then peel back the surface to reveal the pyloric caeca and, below that, the tube feet. The bulb like tops on the tube feet are called ampulla. In the center of the starfish is its madreporite, which is on top of the central disk and is where water enters into through and to the water vascular system. 

Grasshopper Dissection

Since it's easier to see the important internal organs and nerves, we had the grasshopper's dorsal side facing us. Taking a pair of scissors, we began cutting at the bottom in an upward motion. We were sure to cut as slow and close to the exoskeleton as possible so not to cut any of the ventral nerve cord. In order to see the brain and dorsal ganglion, we could've continued cutting higher into the head. Once we get to the top near the neck region, we started cutting toward the sides. We did this by cutting from both the top and bottom portion of the prothorax. By spreading the exoskeleton to the sides, we revealed the inside of our grasshopper. We also inspected many of the outer parts such as the tympanic membranes which they use for hearing and the antennas which they use for feeling surfaces and sensing danger around them.  

Perch Fish Dissection:

Turn the perch onto its dorsal side and begin a rectangle shaped incision in the operculum and peel back in order to reveal the organs. Below the operculum are the bony gill rakers. In the gills are the cartilage support called the gill arch along with soft gill filaments that make up each gill. At the posterior end of the stomach are the coiled intestines. The pericardial cavity contains the heart. The upper part of the body below the lateral line is the swim bladder.

Crayfish Dissection:

First step is to lay the crayfish on its side. Locate the cephalothorax and the abdomen region. Turn it with its dorsal side upward and locate the rostrum (beneath it should be the eyes). Locate where the appendages in the head region are and find the antennae. The, study the mouth which have mandibles behind the antennae. The largest part of the appendages is the chelipeds or the claws. Behind each of these are walking legs. Then turn the crayfish central side up to locate the appendages from the ventral side. Lift away the carapace and using scissors cut the case of the tail and lift the parts of the carapace to reveal the gills and other organs. The maxillae passes the food and travels down the esophagus to the stomach. When opened up, one is able to see the intestine, the stomach and the anus of the crayfish.In the tail, we can see the intestines and tail muscles which help crayfish swim through the water.