MARE 394 – Dissection #5 – Ratfish
You will be responsible for all systems listed in the lab whether there is a specific figure to represent
each in your dissection guide. You are asked to draw each of the tissues as they appear in your animal not as they appear in the dissection guide.
1. External Anatomy
Orient yourself to the ratfish by identifying the following external features:
a. Lateral line
b. Anterior dorsal fin
c. Posterior dorsal fin
d. Pectoral fin
e. Caudal fin
f. Pelvic fin
g. Spiracle
h. Lateral line
i. Eye
j. Gill slits
k. Nostrils
l. Cloacal opening
m. Ampullae of Lorenzini
n. Clasper (♂)
o. Endolymphatic pore
2. Digestive and Respiratory Systems
Using scissors, make a cut from the corner of the jaw through the five gill arches. Just posterior to the
fifth gill arch, make a cut across the throat just between the heart (anterior) and the abdominal cavity
(posterior).
Identify the following features from the mouth and pharynx in Fig 8 (p.15).
3. Esophagus
9. Gill rakers
17. Pharynx
18. Spiracle
20. Tongue
Using the scalpel, make a shallow incision in the middle of the abdominal cavity halfway between the
cloaca and the pharyngeal cavity. Once the incision has been made, carefully insert forceps to pull the
abdominal wall away from the internal organs so that the incision can be extended to the pharynx
(anteriorly). Cut transversely across the abdominal wall at the pharynx and just above the cloacal
opening so that the wall sections can be folded open to expose the internal organs. Pin the abdominal
walls to the dissection pad to hold them in place; you may need to score the internal abdominal wall to
relieve the tension.
Identify the following features of the digestive system from Fig. 11 (p.19).
3. Bile duct
4. Body of stomach
5. Cardiac region of stomach
9. Colon
13. Dorsal lobe of pancreas
14. Duodenum
15. Falciform ligament
16. Gall bladder
22. Left lobe of liver
25. Median lobe of liver
33. Pyloric region of stomach
34. Rectal gland
35. Right lobe of liver
37. Spleen
39. Valvular intestine
41. Ventral lobe of pancreas
Using scissors or scalpel, cut open portions of the esophagus to expose the papillae, the stomach to
expose the rugae, and the intestine to expose the spiral valve following the figure on page 22. Examine
the gut contents of the stomach and compare with other students.
3. Heart
Use the schematic on page 23, Fig 13 (p. 24) and Fig 17 (p. 29) to identify the following structures of
the heart.
Conus arteriosus
Atrium
Ventricle
Sinus venosus
Dorsal aorta
Coronary artery
Afferent branchial arteries
Efferent branchial arteries
Celiac artery
Ventral aorta
4. Urogenital system
Use figure 19 (p. 33) to identify the following features of the ♂ urogenital system.
4. Clasper
5. Cloaca
6. Colon
8. Ductus deferens
9. Epididymis
10. Kidney
12. Left testis
13. Leydig’s gland
16. Opening siphon into clasper tube
21. Right testis
22. Seminal vesicle
23. Siphon
24. Sperm sac
25. Urogenital papilla
IF WE HAVE FEMALE RATFISH
Use figure 20 (p. 35) to identify the following features of the ♀ urogenital system
4. Cloaca
5. Colon
9. Embryo with uterus
12. Kidney
13. Left oviduct
16. Opening of uterus into cloaca
5. Brain
Cerebellum
Cerebrum
Optic lobe
Olfactory Lobe
Olfactory Bulb
17. Ostium to oviducts
18. Ovary containing eggs
20. Oviduct
23. Urogenital papilla
24. Uterus containing embryos
26. Yolk sac