Gross Dissection of the Stomach of the Lobster, <em>Homarus Americanus</em>

Abstract

The stomach of the American lobster (Homarus americanus) is located in the cephalothorax, between the rostrum and the cervical groove. The anterior end of the stomach is defined by the mouth opening and the posterior end by the bottom of the pylorus. Along the dorsal side of the stomach lies the stomatogastric nervous system (STNS). This nervous system, which contains rhythmic networks that underlie feeding behavior, is an established model system for studying rhythm generating networks and neuromodulation 1,2 . While it is possible to study this system in vivo 3 , the STNS continues to produce its rhythmic activity when isolated in vitro. In order to study this system in vitro the stomach must be removed from the animal. This video article describes how the stomach can be dissected from the American lobster. In an accompanying video article 4 we demonstrate how the STNS can be isolated from the stomach. 4. Remove the carapace from around the stomach, (i.e. the head region between the cervical groove and the rostrum).5. Detach the face (region including eyes, and rostrum).1. Use a twisting motion to rip off the front claws. 2. Remove the abdomen (tail portion) by using the large scissors to make a deep cut between the cephalothorax and abdomen. This cuts the giant fiber tracts controlling the tail flip response. Then proceed to cut off the abdomen. 3. Remove the antennae by trimming them off with scissors, and twist off the legs and the third maxillipeds.1. Starting on the lateral edge of this section use rongeurs and spatula to carefully remove the hard carapace, while leaving the reddish underlying hypodermis intact. The spatula is useful for separating the layers so that the carapace can be broken off with the rongeurs. 2. Moving toward the eyes you find bilateral lightly calcified small oval plates (IIIa ossicles). As close as possible to these ossicles, carefully detach the muscle from the ossicles using the small scissors. 3. Using spatula and rongeurs remove carapace from between the eyes and the caudal portion (approx. 1 centimeter) of the rostrum.

<em>Homarus Americanus</em> Stomatogastric Nervous System Dissection

“…Prior to beginning this protocol the stomach of the lobster must be removed from the animal and prepared as described in the companion JoVE article (Bierman & Tobin, 2009). The majority of the steps outlined below are to be performed under a dissection microscope.…”