ANATOMY OF THE DOGFISH SHARK
Date: August 28, 2014
Can you imagine how and what it could be like when an organism does not have a specified structure and surface? Plants have cell walls; even amoebae have plasma membranes that wall off the protoplasm from the water surrounding it. In humans, perhaps, no other organ receives so much attention both from its owner and the eyes of the others. The skin is always the first line of defense against the dangers of the outside world. Though not always clearly, evidences of some internal disorders, external affronts—bumps, cuts, chafe, insect bites, and other reactions. The external morphology identifies what one is. The integument serves as a factor for survival. The integument system of the aquatic and terrestrial organisms conforms to a basic morphologic pattern, with a multi-layered epidermis derived from ectoderm and a dermis from a mesoderm. The protective roe of the integument is primary to protect the internal organs from injuries and from other substances, the rays of the sun, fur of a threatened mammal, danger alert. On the other hand, the skin is also for respiration, excretion of carbon dioxide, thermoregulation, locomotion, homeostasis maintenance, for nourishment and skin coloration signals. The integument system of dog fish shark, Squalus acanthias, is portion of what makes up its external morphology. In this experiment, integument comes along with the external features of the shark—its gills, scales and appendages in the form of fins. Shark, a typical vertebrate means that its head is incased in a cranium and its vertebrae are associated with the notochord. More of its external morphology will be discussed here.
By the end of the experiment, the students should be able to: 1. To be able to have a fuller understanding of the structure of the skin of the shark. 2. To be able to identify the different parts of the shark and its functions. 3. To be able to determine how the shark differs from us, humans.
To start off with the external morphology of the shark, we had to start by viewing its external features. We examined it while it was still intact to reveal the following features: Its head, trunk, tail, external gill slits, spiracle, eyes, lateral line canal, pectoral fins, pelvic fins, dorsal fins, fin spines, caudal fin, external nares, mouth, labial pouch and groove, teeth, endolymphatic pores, ampullae of Lorenzini, claspers, cloaca, papilla and abdnominal pores. Then we examined its integumentary system. We chose three different areas where to remove a small thin piece of the shark’s skin from the body surface and these were from the ventral, caudal and anterior areas. After removing a piece of skin from each area by the use of the scalpel, scissors and other dissecting tools, we placed it in a glass slide then viewed it directly under a microscope. A cover slip was not needed for its preparation. The scales can be easily seen so there was no need to soak it in glycerine solution overnight or to place it in a solution of sodium hypochlorite for a few hours.
You can describe the skin layer a little and then come to the scales. You can talk on the orgin of scales. Then give some examples how the external morphology of the shark is for the shark’s adaptation in water. ANSWERS TO QUESTIONS
1. How is the shark’s nose different from our own?
The shark’s nose differs from us in a way that they are located in each side of the head, cranial from the eyes. There are two pairs of openings or nostrils. One is much smaller than the other and this takes in water while the other one expels water. The water passes by a sensory membrane allowing the shark to detect chemicals in the water. 2. Why are the Spiracles important?
The spiracles are important because it allows water to pass through the gills even when the...
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