the dogfish shark, Squalus acanthias.
The dogfish is a small predator that occurs along both coasts of the Atlantic Ocean.
This shark has internal fertilization, with the eggs being retained in the mother during their development (ovoviviparous). The young are then born live. The dogfish has the longest gestation period of any of the sharks, extending for 16 – 20 months. Usually two to six pups are born per litter and will measure approximately six inches long.
The terms to be covered during the examination of external anatomy include:
1. Spiracle: modified gill slit for water intake to mouth and gills
2. Lateral line:
3. Gill slits: sensory cells that pick up vibration in water from over a
600 yard distance!!! water passes over gills and respiration occurs
4. Anterior dorsal fin: bears spine for protection from enemies
5. Posterior dorsal fin: bears spine for protection from enemies
6. Caudal fin: drives shark forward
7. Pectoral fin:
8. Pelvic fin:
9. Clasper:
10. Mouth:
11. Nostrils:
12. Ampullae: swimming and steering swimming and steering if specimen is a male, these fingerlike extensions of the pelvic fin will be used to transfer sperm to the female during mating. note ventral location paired nostrils for olfactory sense can detect blood from a distance of ¼ mile. (one part blood in 100 million parts of water) tiny pores in the face for picking up electric fields in the water to help guide the shark and locate prey at minimal distances.
Placoid Scales: Dermal denticles of the shark’s skin with a similar structure to teeth – gives a sandpaper feel. You will have the opportunity to feel this later.