Mytilus-Venus

Mytilus-Venus - Dissection guide for Mytilus californianus...

Info icon This preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Dissection guide for Mytilus californianus and Venus merceanaria Each student (along with their partner) should accomplish the following during the lab: 1. Sketch the external anatomy of your animal (shell, ligament etc.) 2. Sketch the generalized internal anatomy of your animal (making sure to label all relevant features) 3. Sketch and compare the relative anatomy of the ctenidia 4. Expose and sketch the circulatory system in the region of the heart 5. Time permitting dissect and sketch the digestive system (stomach, style, intestine) Remember... Annotate, annotate, annotate! Introduction Your first reaction to this lab might be: "Ugh--bivalves. All they do is filter feed seawater". That's quite true--that's pretty much all they do most of the time. But the extreme adaptations to filter - feeding one sees in bivalves are part of what makes them such fascinating objects of study. And even though all bivalves utilize basically the same food source, they inhabit a variety of habitats. The forms you will study today--the mussels and the quahog clam -- inhabit places as different as night and day: the mussel, the wave swept mid - tidal zone: the quahog, the sand or mud of quiet bays. As you go through this lab, keep comparing/ contrasting the two animals in the light of their different habitats and lifestyles, but don't lose sight of the fact that they are built on the same basic plan. Once you identify the elements in this plan, it will be easier for you to get a handle in the modifications each form has undergone. A Little Background In bivalves, or pelecypods ("knife-foot" in Latin) the mantle has become greatly enlarged, and covers the head. The gills are highly modified for filter feeding; because the food particles they eat are so small, bivalves have no need for the scraping radula and muscular buccal apparatus seen in most other mollusks. Today you will be looking at typical representatives of the two largest bivalve groups: the Pteriomorpha, which have adapted themselves primarily to living attached to a substrate, and the Hterodonta, which are mainly burrowers in mud or sand. Like many of its pteriomorph relatives, the mussel ( Mytilus californianus ) has the comparatively primitive "lamellibranch" or fillibranch ctenidia, in which the individual filaments are not bound together. The quahog clam ( Venus mercenaria ), a typical heterodont, has the more complex eulamellibranch ctenidia, with cross linked filaments. In addition to this, pteriomorphs have a comparatively weak hinge area, without true teeth, and they draw sea water in and out through a simple opening in a fused region of the mantle rather than trough true inhalant and exhalant siphons, as heterodonts do.
Image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Life Histories Unlike its relatives, the oysters and rock scallops, which attach their lower shell valve to the substrate, Mytilus attaches itself with elastic byssal threads. You can see these threads protruding from the valves of your specimens.
Image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern