Tegula - Lab 1 A dissection of the trochid gastropod Tegula...

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Lab 1: A dissection of the trochid gastropod Tegula funebralis . Intro: The basic molluscan body plan has been modified through the course of the phylum’s evolutionary history to address the challenges associated with a variety of diverse habitats and life histories. Today we will compare how this basic invertebrate body plan has been modified to suit a benthic, creeping, herbivorous lifestyle representative of many marine snails. We will focus on four major areas: 1) general morphology and orientation of the external body and mantle cavity, 2) cephalization with respect to sensory structures, 3) the circulatory/respiratory system and 4) the digestive system. Throughout the entire lab exercise, you should consider how the basic mollucscan body plan consisting of a shell, muscular/creeping foot, mantle with the underlying visceral mass and associated mantle cavity, and radula have been modified to address the unique demands of this organism’s habitat and lifestyle. Sounds like prime material for annotation to me! Obtaining your animal: We will be working with live (and anesthetized) snails There will be some un-narced snails available for live observations but you should use the MgCl 2 narced snails for dissection. Your lab instructor will direct you to where you can obtain a specimen. Sketch 1- External observations: In this section you should familiarize yourself with the general external anatomy of the organism. Make sure you can identify all of the relevant axes (dorsal/ventral, anterior/posterior etc.) Locate and identify all of the obvious features especially those that reveal the organism’s molluscan heritage such as mantle, foot, shell, visceral mass, radula (note these may not all be apparent in an external view) Figure1: External view of T. funebralis (shell removed) Observe first a live and locomoting Tegula in seawater. Note the cephalic tentacles and epipodial tentacles (What do they do?). Apologize to your animal and remove its shell (using a narced specimen). This can be difficult. Tegula's soft body and very hard shell make its
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extraction akin to cracking open a Brazil nut and removing the meat intact. The best method is to use a vise or screw-clamp. A few minutes of steady stress in the vise's jaw will crack the shell with no damage to the animal. Remember that the animal is attached to the shell at a point along the columella just inside the aperture. The muscle here must be cut for removal. If you end up with what looks like a lump of mutilated flesh, that is exactly what you have and you should go get another animal. All of the features described below should be visible. Many organs are visible at this point, so it is good time to get oriented. Place the
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This lab report was uploaded on 04/16/2008 for the course BIO 120 taught by Professor Idk during the Winter '04 term at UCSC.

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Tegula - Lab 1 A dissection of the trochid gastropod Tegula...

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