Name: ___________________
The mudpuppy’s mouth is large and bounded by lips. The lidless eyes are small, as are the widely separated nares, which communicate with the oral cavity (see below). A short neck is present between the head and the long trunk. Notice the lack of tympanic membranes since mudpuppies are found in an aquatic environment and rarely make noise, there is no need for a well developed ear (tympanic membrane) like in frogs and toads. They are more similar to fish and use a lateral line for detecting changes. A lateral line system is present, but is not obvious as in fish.
Posteriorly, the large, flattened tail bears a small, marginal fin, which, however, lacks the supporting rays present in fishes.
Paired pectoral and pelvic limbs are small, but bear the three segments typical of terrestrial tetrapods. The cloaca, marking the posterior end of the trunk, lies ventrally between the pelvic limbs. In males the cloacal aperture is surrounded by small projections or papillae.
The region around the cloaca is swollen due to the presence of the cloacal gland in mature males.
Lastly, note the smooth, scaleless skin, which has an important respiratory function.
Once you have successfully located all that was required below and you are comfortable with identifying these organs if asked or quizzed…on Wednesday, you may explore further – some ideas…

Brain cavity

Eyes – do they have the same “red” hard ball that makes up the eyes like frogs?

How gills connect to the heart
 Anything else you would like to explore…
 If your stomachs seem “full” cut it open…

Dissect the specimens as follows:
Part I: Making the cuts:
1. Start by turning the animal ventral (belly) side up.
2. Pinch the skin slightly with a pair of forceps slightly off to the left the mid-ventral line near the cloaca. (see #1 in diagram)
3. Make a small cut with the scissors though the pinched up skin. The goal is to cut the skin and muscles at the same time – without injuring the organs below.
4. Then continue the cut anteriorly (towards the head) keeping slightly left of center until you get to the jaw line at #2 on diagram. Just like the frog, you will need to turn your scissors sideways to cut through the cartilage to expose the chest cavity
– it’s not tough but stay to the LEFT – be careful! Don’t cut too deep and cut the heart!
5. Make a pair of cuts laterally from the mid-ventral cut immediately posterior to the front limbs (#3 armpit area) and immediately anterior to the hind limbs (#4 just in front of the hindlimbs).
6. Gently spread the abdominal wall
7. You should now be able to fold away the body wall, gaining access to the body cavity and the organs you are interested in. Pin the folds back out of your view.
Part II: Exploring the Digestive Organs: Make sure you are able to identify all organs in bold!! Some parts have questions you must answer…
1. The large, elongated, dark structure midventrally (in middle) is the liver . a. Describe the liver: b. Is it similar to the dogfish shark we dissected first?
2. Lift the cut edge of the body wall to observe the falciform ligament extending between the wall and the ventral surface of the liver. The ligament is much larger than in the other vertebrates considered here. Depending on your mudpuppy this may or may not be clearly obvious – you may need some assistance identifying this ligament.
3. Examine the part of the cavity right above the cloaca area to observe the thinwalled urinary bladder . It is a clear/opaque colored structure.

4. Locate the long, light-colored, tubular stomach . It lies dorsal (behind) and slightly to the left of the liver
(remember left is not your left, it’s the mudpuppy’s left). a. Describe the stomach: b. Is it similar to the dogfish shark? What about the frog from the online dissection? Explain answers
5. Lift the stomach to see that it is supported by the greater omentum. Spread apart the liver and stomach. The gastrohepatic ligament is the small, triangular sheet stretching between their anterior portions.
6. The elongated spleen hangs from the posterior left side of the stomach. It is a darker colored organ.
7. The stomach ends abruptly at the pyloric sphincter , a marked constriction beyond which the digestive tract continues as the long, coiled small intestine , followed by the short, straight large intestine . a. Comparing the dogfish shark’s intestines and the mudpuppy’s intestines, what are some differences? How are they the same?
8. The mesentery supports the small intestine. Spread the coils of the small intestine to observe it.
9. The first loop of the small intestine is the duodenum. Several organs and vessels lie in this region, but may be difficult to discern.
10. The pancreas lies along the duodenum, to help identify it, pull the stomach to your left and reflect the liver to the right to expose its dorsal surface. The pancreas is irregular, but note that part of it extends anteriorly toward the spleen.
11. Next, observe the long, thin transparent pinkish-colored left lung lying behind the stomach (almost along the back side to the side). The right lung is similar in form. You should be able to find both the left and right lungs. The right lung will be more attached to the surrounding mesentery so you may have to carefully tease it away from the tissues. a. From the Mudpuppy Intro you had to read, what is the purpose of the lungs in a mudpuppy? b. What is the main structure used for breathing in mudpuppies?

12.
Next, reflect the stomach to the right (your left), so that it lies on the liver’s dorsal surface (it will be resting on the back side of the liver). Note the relationship among the liver, stomach, spleen, and pancreas, as well as their associated mesenteries. Let the organs fall back in place, and then reflect the liver to the left
13. Examine the lower right (your left) part of the liver for the gall bladder , a thin, translucent sac. Gently lift it and examine the region where it attaches to the liver.
(your right).
14. Once you have located all the digestive organs, carefully put your silver probe into the mudpuppy’s mouth to try to locate the esophagus and push in through the mouth. You know you have located it when your probe will show up moving down towards your stomach.
Part III: Exploring the Urinary and Reproductive Structures
1. Lift the coils of the small intestine in the posterior part of the peritoneal cavity to locate one of the paired gonads (sex organs)
Do you have a male or female? ___________________________
2. For males: In males the testis is an elongated organ posterior (towards tail) in the cavity. There will be one on both sides. The kidney is longer than the testis and is considerably wider at the bottom than at the top. a. The archinephric duct is a longitudinal tube that runs along the lateral margin of the kidney. The portion along the genital part of the kidney is coiled, but its more posterior part, lying along the urinary portion of the kidney, is straight. Trace the duct posteriorly (towards tail) to its entrance into the cloaca . b. In males the duct carries sperm from the testis, as well as urine from the urinary portion of the kidney. Sperm reaches the duct by way of ductules efferentes, which lead into the genital portion of the kidney and thence to the archinephric duct. c. The margins of the male cloaca bear numerous cloacal papillae . Skin the region on one side of the cloaca to expose the cloacal gland , which consists of numerous tiny tubules and is involved in clumping sperm to form spermatophores.

3. For females: In females the elongated ovaries may be quite large. There will be one on both sides near the kidneys . If your female is mature enough you may see the presence of numerous eggs within follicles which gives the ovary a lobulated or granular appearance, in contrast to the more regular surface of the testes. a. The archinephric duct lies along the kidney but is straight and narrower than in the male. In the female it carries only urine from the kidney. Follow it posteriorly to its entrance into the cloaca .
The oviduct is the long, prominent, and convoluted tube lying between the ovary and kidney and extending nearly the length of the peritoneal cavity. b. At its anterior end (towards head) is the open, funnel-shaped ostium, into which the eggs pass after they have been released into the coelom by the ovary. c. Follow the oviduct posteriorly to its entrance into the cloaca . d. Cloacal glands and papillae are absent in the female.
***Whether you have a male or female – make sure you look at another mudpuppy with the opposite sex!!!
Part IV: Heart
1. The pericardial cavity lies just anterior (above) to the liver. It is enclosed by the pericardial sac and contains the heart .
2. Continue the midventral incision of the abdominal wall anteriorly, cutting through the coracoid cartilage, to expose the pericardial cavity if you have not already done so at the beginning of your incisions.
3. Do not injure the posterior vena cava, which passes through the septum to reach the pericardial cavity.
4. Carefully remove the muscles of the ventral cavity to expose the chest cavity.
5. The largest and most visual part of the heart is the ventricle , which occupies the bottom part of the pericardial cavity.
6. The atrium lies just above and behind the ventricle and is partially divided into left and right atria .
Is the heart in this mudpuppy the same as the heart in the dogfish shark? Explain the key differences: