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Biology 03050, Invertebrate Zoology

Handout for Laboratory 8: MOLLUSCS

Lab Manual: Hickman et al., 9th ed., Exercise 12, pp. 175-192



WORD BANK (terms that you are responsible for):


  1. adductor muscle (anterior vs. posterior)
  • anterior (anatomic position)
  • anus
  • aperature--excurrent
  • aperature--incurrent
  • arm
  • beak
  • cecum
  • chromatophore
  • Class Bivalvia (clams)
  • Class Cephalopoda (squids)
  • Class Gastropoda (snails)
  • Class Polyplacophora (chitons)
  • Class Scaphopoda (tooth or tusk shells)
  • coelom (body cavity--small in molluscs)
  • digestive glands
  • dorsal (anatomic position)
  • eye
  • foot
  • foot retractor muscle
  • gill (ctenidium)
  • glochidium
  • gonad
  • head
  • head-foot
  • heart
  • hinge ligament
  • ink sac
  • intestine
  • kidney
  • labial palp
  • lateral fin
  • layers of shell: if asked, be able to distinguish nacreous layer, prismatic layer, periostracum
  • left (anatomic position)
  • lens
  • lines of growth
  • liver
  • mantle
  • mantle cavity
  • mouth
  • nerve fiber
  • nidamental gland
  • ovary
  • pallial line (margin of mantle)
  • pen
  • pericardial membrane
  • posterior (anatomic position)
  • radula
  • right (anatomic position)
  • shell
  • siphon (funnel)
  • stomach
  • sucker
  • tentacle
  • testis
  • umbo
  • valve (left vs. right)
  • ventral (anatomic position)
  • visceral mass
  • whorl of shell

    Using your lab manual, peform those parts of Exercise 12 listed below:

    12: Read over the introduction to the phylum, pp. 175-176. Think about the relative proportions of visceral mass, mantle (and mantle cavity), and head-foot in each of these different specimens. Also think about the anatomic orientation (anterior, posterior, etc.) of members of the different classes of molluscs.

    12A: Examine external and internal features of a clam, highlighting the terms listed above. We will be dissecting preserved clams, so that the appearance will not be as"fresh" as described in the lab manual. In addition to the diagrams in your lab manual, use the model of clam anatomy to help find your way around. Demonstration slides and specimens of other bivalves will be available for comparison.

    12B: Examine a living snail and/or slug in a small glass container, testing aspects of behavior mentioned in the lab manual. Examine different shells of snails and be able to tell right-handed from left-handed shells. Compare gastropod shells to those of tusk shells--what are differences? If interested, there are preserved snails to observe anatomy (no dissecting of these, please).

    12C: Examine the external features of both small and large preserved chitons. Can you find the mantle cavity and the gills (ctenidia)?

    12D: Examine the external features of available cephalopods (before dissecting). What are major differences among squids, octopi, and cuttlefish? Note the presence of the internal shell (pen), particularly in the cuttlefish specimen. What is the anatomic orientation of a squid? Examine the sectioned shell of a nautilis (if available)--how does this shell compare to the shells of other cephalopods?

    12D: Examine the internal features of a squid with dissection. Be sure to avoid the"mine fields" of ink sac, liver, and cecum. If your squid fills with a dark black or brownish mess, rinse it out in the sink. Compare your dissection with Figure 12-15--how many structures are you able to find and characterize? Why is the set up in the squid so different from that of the clam?

    Your instructor may assign you additional questions from the lab manual as homework or as items for quizzes.

    Your notes and drawings (looks like the back will have more space than below!):

    |main page| |background| |03028: Physiology| |03048: Anatomy|

    |03050: Invertebrate Zoology| |03051: Vertebrate Zoology| |03074: Economic Botany|


    Please send comments and questions to: cronewil@hvcc.edu


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    This page updated October 8, 1999