Name: Gross Dissection of the Stomach of the Lobster, Homarus Americanus (Video) | JoVE Journal
Uploaded: 2009-05-22T00:00:00.000+00:00
Duration: 10 min 12 s
Description: Learn gross dissection of the lobster stomach using Homarus americanus to access the somatic gastric nervous system. This method enables researchers to study rhythmic neural circuit behavior in marine biology.

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5 minutes

We would like to acknowledge our advisor, Dr. Eve Marder. This research was supported by National Institute of Health grants NS17813 to Eve Marder and NS059255 to A-E T.

<ol>
<li>Before dissection the lobster should be buried in ice for 30 minutes to anesthetize the animal.</li>
<li>The sex of the lobster can be determined by looking at the shape of the first swimmeret. Males have boney swimmerets and females have feathery swimmerets. <img src="/files/ftp_upload/1320/1320fig1.png" alt="Crustacean sexual dimorphism diagram comparing female and male abdominal structures." data-altupdatedat="1761735611000"></li>
<li>Isolate the cephalothorax.<ol>
<li>Use a twisting motion to rip off the front claws.</li>
<li>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.</li>
<li>Remove the antennae by trimming them off with scissors, and twist off the legs and the third maxillipeds.</li>
</ol></li>
<li>Remove the carapace from around the stomach, (i.e. the head region between the cervical groove and the rostrum).<ol>
<li>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.</li>
<li>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.</li>
<li>Using spatula and rongeurs remove carapace from between the eyes and the caudal portion (approx. 1 centimeter) of the rostrum.</li>
</ol></li>
<li>Detach the face (region including eyes, and rostrum).<ol>
<li>Using small scissors make a horizontal cut across the most rostral exposed tissue in the rostrum to detach it from the exoskeleton. Then use edge of scissors and/or spatula to carefully roll tissue caudally, just past the level of the IIIa ossicles.</li>
<li>Starting dorsally, use small scissors to detach remaining tissue from the face exoskeleton. Cut as close to the hard carapace as possible, stopping when you get near the center and attachment of the mouth.</li>
<li>From ventral view the mandibles should be easily visible. Detach remaining maxillipeds.</li>
<li>Locate soft lip under the mandibles.</li>
<li>Make lateral cuts to detach the face while keeping the lip attached to the stomach. (There is a slightly curved bluish outer mouth part that can be used as a guide.)</li>
</ol></li>
<li>Detach and remove the stomach.<ol>
<li>Hold the lobster in the palm of your hand, ventral side up and so that the anterior end is toward your elbow.</li>
<li>Attach a hemostat to the lip and let gravity pull the hemostat and lip down and away from the ventral body wall.</li>
<li>Using small scissors cut out mandibles.</li>
<li>Locate the dorsal side of the ventral body wall, which forms a hard “shelf” ventral to lip and stomach. Cut just below the "shelf", very close to the body wall, across the entire medial-lateral midline. The entire ventral side of the stomach should now be detached from the body wall.</li>
<li>Turn the lobster so that the dorsal side is up. Cut along the rostral edge of the cervical groove, where the carapace was removed, and gently pulls the stomach out.</li>
<li>Detach any extra intestines that remain attached to the stomach.</li>
</ol></li>
<li>Open the stomach, and prepare it for pinning.<ol>
<li>Hold the stomach in the palm of your hand with the hypodermis-side down. The hemostat should still be attached to the lip and should lie between your fingers.</li>
<li>Use small scissors to make a shallow anterior-to-posterior cut from the mouth opening (below the lip) down through the ventral side of the pylorus.</li>
<li>To further open the stomach, make two lateral cuts along the ossicles running across the center of the stomach.</li>
<li>Cold saline may be poured into the stomach to improve visibility and expel stomach contents.</li>
<li>In order to allow the preparation to lay flat in the dissecting dish use the small scissors to trim the three gastric teeth.</li>
</ol></li>
<li>Pin the stomach down in the dissection dish.<ol>
<li>Place the stomach, hypodermis-side up, in a saline-filled dissection dish.</li>
<li>Place insect pins at the lip and the four corners created when the stomach was opened up. For the anterior corners place pins high and close to the edge, as not to disturb commissural ganglia or inferior oesophageal nerves. For the posterior corners place pins slightly high as not to disturb the pyloric dilator muscle.</li>
</ol></li>
</ol>

<ol><li>Marder, E., Bucher, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Central+pattern+generators+and+the+control+of+rhythmic+movements%5BTitle%5D)+AND+%22Curr.+Biol%22%5BJournal%5D)">Central pattern generators and the control of rhythmic movements.</a> Curr. Biol. 11, R986-R996 (2001).</li>
<li>Nusbaum, M. P., Beenhakker, M. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+small-systems+approach+to+motor+pattern+generation%5BTitle%5D)+AND+%22Nature%22%5BJournal%5D)">A small-systems approach to motor pattern generation.</a> Nature. 417, 343-350 (2002).</li>
<li>Clemens, S., Massabuau, J. C., Legeay, A., Meyrand, P., Simmers, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((In+vivo+modulation+of+interacting+central+pattern+generators+in+lobster+stomatogastric+ganglion%3A+influence+of+feeding+and+partial+pressure+of+oxygen%5BTitle%5D)+AND+%22J.+Neurosci%22%5BJournal%5D)">In vivo modulation of interacting central pattern generators in lobster stomatogastric ganglion: influence of feeding and partial pressure of oxygen.</a> J. Neurosci. 18, 2788-2799 (1998).</li>
<li>Tobin, A. E., Bierman, H. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Homarus+americanus+stomatogastric+nervous+system+dissection%5BTitle%5D)+AND+%22J+Vis+Exp%22%5BJournal%5D)">Homarus americanus stomatogastric nervous system dissection.</a> J Vis Exp. 27, (2009).</li>
<li>Maynard, D. M., Dando, M. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+structure+of+the+stomatogastric+neuromuscular+system+in+Callinectes+sapidus%2C+Homarus+Americanus+and+Panulirus+argus+%28Decapoda+crustacean%29%5BTitle%5D)+AND+%22Philos.+Trans.+R.+Soc.+Lond.+B+Biol.+Sci%22%5BJournal%5D)">The structure of the stomatogastric neuromuscular system in Callinectes sapidus, Homarus Americanus and Panulirus argus (Decapoda crustacean).</a> Philos. Trans. R. Soc. Lond. B Biol. Sci. 268, 161-220 (1974).</li>
<li>Herrick, F. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Natural+history+of+the+American+Lobster%5BTitle%5D)+AND+%22U.S.+Bur.+Fish%22%5BJournal%5D)">Natural history of the American Lobster.</a> U.S. Bur. Fish. , 219-252 (1909).</li>
<li>Marder, E., Bucher, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Understanding+circuit+dynamics+using+the+stomatogastric+nervous+system+of+lobsters+and+crabs%5BTitle%5D)+AND+%22Annu.+Rev.+Physiol%22%5BJournal%5D)">Understanding circuit dynamics using the stomatogastric nervous system of lobsters and crabs.</a> Annu. Rev. Physiol. 69, 291-316 (2007).</li>
</ol>

In our laboratory dissection of the lobster stomach is done to access the stomatogastric nervous system, a network that controls the rhythmic contractions of the stomach. The anatomy of lobster stomach has been well described previously5-7, and we recommend becoming familiar with its anatomy. Doing so will reduce the risk of damaging the delicate nerves and muscle.
Upon completion of the stomach dissection, various portions of the STNS may be further dissected. For example to st...

<table><tbody><tr><td>&lt;em&gt;Homarus americanus&lt;/em&gt;</td><td>Commercial Lobster</td><td></td><td>Can be purchased from any lobster supplier, We specifically request chicken&amp;#8221; lobsters.</td></tr><tr><td>Black Sylgard 170</td><td>Dow Corning</td><td>170</td><td></td></tr><tr><td>Preparation Dish</td><td>Fisher Scientific</td><td>08-807</td><td>Fill 2&quot; with Black Sylgard 170.</td></tr><tr><td>Fine Scissors</td><td>Fine Science Tools</td><td>14090-09</td><td></td></tr><tr><td>Insect Pins size 6</td><td>Fine Science Tools</td><td>26000-65</td><td></td></tr><tr><td>Mayo Scissors</td><td></td><td></td><td>This is a common product offered by many suppliers of dissecting tools.</td></tr><tr><td>Micro-Spatula</td><td>WARD&amp;rsquo;s Natural Science</td><td>15 V 4313</td><td>This is a very common product offered by many suppliers of lab tools.</td></tr><tr><td>Rongeurs</td><td>Fine Science Tools</td><td></td><td>16000-14</td></tr><tr><td>Plastic hemostat</td><td></td><td></td><td>This is a common product offered by many suppliers of dissecting or jewelry making tools.</td></tr></tbody></table>

gross dissection of the stomach of the lobster, homarus americanus

Gross Dissection of the Stomach of the Lobster, Homarus Americanus

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 article4 we demonstrate how the STNS can be isolated from the stomach.

We describe the gross dissection of the stomach of the American lobster (Homarus americanus).

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 procedure for isolating the stemo gastric nervous system from a lobster can be divided into two parts, the gross and the fine dissections. In this video, we demonstrate the gross dissection. The protocol involves isolating the cephalic thax, removing the stomach, and opening the stomach to facilitate the fine dissection of the somatic gastric nervous system.Hi, I am Hilary Bierman from the laboratory of Dr.Eve Martyr at Brenda University. Hi, I'm Annalise Tobin, also from the murder lab. Today we will show you the procedure for the gross dissection of the stomach of the lobster Hamas Americana.We use this procedure in our laboratory to access the somatic gastric nervous system, which we used to study how small neural circuits produce rhythmic behavior. So let's get started. 30 minutes before the dissection anesthetize the lobster by burying it in ice at the beginning of a dissection.The sex of a lobster is determined by looking at the shape of the first swim ette. Males have bony swim ettes and females have feathery swim ettes. Begin the dissection by first isolating the cephalic thax.The first step in doing this is applying a twisting motion to rip off the front claws. Next, remove the abdomen. Begin at the tail portion by using the large scissors and make a deep cut between the celo, thax and the abdomen.This cuts the giant fiber tracks controlling the tail flip response. And now finish cutting off the abdomen. Remove the antenna by trimming them off with scissors and twist off the legs and the third maxillipeds.And next, you will reveal the stomach within the clu thax by removing the surrounding carpus. The stomach is between the cervical groove and the rostrum. Starting on the lateral edge of this section, user on Jos and spatula.To carefully remove the hard carus while leaving the reddish underlying hypodermis intact. The spatula is useful for separating the layers so that the carpus can be broken off. With the Ron Jos moving toward the eyes, you find bilateral, lightly calcified small oval plates.These are the three A OSLs as close as possible. To these ossicles, carefully detach the muscle from the ossicles using the small scissors, using the spatula and Urs, remove the carpus over the first centimeter of the rostrum. Next, using small scissors, make a horizontal cut across the most rostral exposed tissue in the rostrum to detach it from the exoskeleton.Then use the edge of the scissors and or spatula. To carefully roll the tissue coddly just past the level of the oval plates. Starting dorsally.Use the small scissors to detach the remaining tissue from the face and exoskeleton. Using your index finger, press down on the rostrum To better expose this area, cut as close to the carpus as possible and stop. When you get near where the mouth attaches in the center From a ventral view, the mandible should be easily visible.Detach the remaining maxilla bed. Locate the soft lip under the mandibles. This lip must be kept attached to the stomach while it is detached from the face.Find the slightly curved bluish outer mouth part and use it as a guide to make a lateral cuts detaching the lip from the face by cutting between the soft lip and the outer mouth part. Now the face can be removed. Follow the next steps to excise the stomach.Begin by holding what remains of the lobster in the palm of your hand. Ventral side up and rostral end toward your elbow. Now attach a hemostat to the lip and let gravity pull the hemostat and lip down and away from the ventral body wall.Using the small scissors, detach the stomach wall from the mandibles and surrounding tissue. Locate the dorsal side of the ventral body wall, which forms a hard shelf ventral to lip and stomach. Detach the stomach from this body wall by cutting very close to the body wall below the lip cut across the entire medial lateral midline.The entire ventral side of the stomach should now be detached from the body wall. Now flip the lobster over to work on the dorsal side. Cut along the rostral edge of the cervical groove where the carpus was removed and gently pulled the stomach out.Some intestines may come along too, and if they do use scissors to detach them from the stomach. All that's left to do now is to open the stomach and pin it down. Hold the stomach in the palm of your hand with the hypodermis side down.The hemostat should still be attached to the lip and should lie between your fingers. Now use the small scissors to make a shallow incision along the AP axis at the mouth opening, which is ventral to the lip. Extend the incision down through the ventral side of the pylori.To further open the stomach, make two lateral cuts along the ossicles running across the center of the stomach. To improve visibility of the stomach interior, rinse it out with cold saline. In order to get the preparation to be flat in the dissecting dish, use the small scissors to trim the three gastric teeth inside the stomach.Place the stomach hypodermis side up in a saline filled dissection dish. Place insect pins at the lip and the four corners created when the stomach was opened up for the anterior corners. Place pins high and close to the edge as not to disturb the commis ganglia or inferior esophageal nerves for the posterior corners.Place pins anteriorly to the laterally running ics so as not to disturb the p dilator muscle. Now the preparation is ready for fine dissection of the nervous system. We have just shown you how to perform a gross dissection on the stomach of the American lobster Homa Americana.This gross dissection of the stomach is the first step in isolating the somatic gastric nervous system. The next step is to do a fine dissection of the nervous system off of the stomach to see how this is done. Please see our accompanying video protocol in JoVE Once isolated.The somatic gastric nervous system can be used to study various aspects of nervous system function such as the generation of rhythmic behavior. Thanks for watching and good luck with your experiments.

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We describe the fine dissection of the stomatogastric nervous system from the stomach of the American lobster (Homarus americanus).

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Learn gross dissection of the lobster stomach using Homarus americanus to access the somatic gastric nervous system. This method enables researchers to study rhythmic neural circuit behavior in marine biology.

Gross Dissection of the Stomach of the Lobster, Homarus Americanus

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