EEB 109 Week 3 Lab Manual

EEB 109 Week 3 Lab - EEB 109 LAB INTRODUCTION TO MARINE SCIENCE Summer 2007 INVERTEBRATES II The Mollusks Introduction Having studied lower

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EEB 109 LAB INTRODUCTION TO MARINE SCIENCE Summer 2007 INVERTEBRATES II The Mollusks Introduction Having studied lower invertebrate phyla last week, we will now focus attention on higher invertebrates (Phyla Mollusca , Arthropoda , and Echinodermata) ,. The mollusks are largely marine but also include many freshwater and terrestrial species. This is a very diverse animal group, with several members exhibiting complex and evolutionarily advanced structures. Most members of this phylum have a hard, calcareous external shell that surrounds an unsegmented, soft body. Usually a large muscular foot is also present. The phylum is composed of seven classes (you should know the ones in bold ): Phylum: Mollusca Class: Polyplacophora – chitons Class: Gastropoda – limpets, snails, slugs and abalone Class: Bivalvia – clams, mussels and oysters Class: Cephalopoda – squids, octopuses, nautiloids and cuttlefish Class: Scaphopoda – tusk or tool shells Class: Aplacophora Class: Monoplacophora Four of these classes ( bolded ) are quite common and representatives of each are included in the figure below (Fig. 1). The figure below (Fig. 2) shows the general molluscan body plan as it has been modified in animals representing four of the seven classes. The digestive tract is shaded, the head- foot is stippled, and the shell is indicated by a heavy black line. Clams are similar in 41 A B C D mantle shell siphon cutting teeth accessory shell plates Figure 1:
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body plan to snails and chitons, except they have become dorso-ventrally extended. The head-foot of a squid is elongated and divided into tentacles, but otherwise is similar to the head-foot of a snail. Figure 2: General molluscan body plan as it has been modified in animals representing four of the seven classes. Exercises: 1) A representative bivalve You will examine live specimens of the California mussel, Mytilus californianus, that will serve as a representative bivalve mollusk for observation (Figs. 3 and 4). a. Study the external anatomy of the specimen. The animal is entirely enclosed in a bivalved shell . The hinged area where the valves are joined is the dorsal or top part, whereas the margin of the shell is the ventral part. b. To study the soft internal parts of the animal, it will be necessary to remove one valve of the shell. This should be done carefully in the following manner. 1. Pry the shell open slightly with the knife or scalpel provided. While prying the shell open, you might speculate on the strength and tenacity of their predators. 42 chiton clam snail squid
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2. Be careful not to damage more soft tissue inside than necessary. Be careful not to damage your hand too! Insert a knife or scalpel between one shell and its mantle lining, and sever the large posterior and smaller adductor muscles (See figure below to locate their positions.). The valves should now open easily. Remove one shell valve, leaving all the soft tissue of the animals “on the half shell”. To maintain the animal in
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This note was uploaded on 03/05/2008 for the course EE BIOL 109 taught by Professor Cassano during the Winter '08 term at UCLA.

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EEB 109 Week 3 Lab - EEB 109 LAB INTRODUCTION TO MARINE SCIENCE Summer 2007 INVERTEBRATES II The Mollusks Introduction Having studied lower

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