ZOO 2700 Lecture Notes - Lecture 17: Gas Exchange, Nephridium, Mechanoreceptor
28 Mar 2018
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Document Summary
Apomorphies: bivalve shell with hinge, adductor muscles, radula lost, most are suspension feeders, siphons for inhalant and exhalant water, relatively long-lived (150 years) Each valve has a dorsal peak called an umbo umbo (beak: rises above the hinge, umbo is the oldest part of the shell. Trifolds: inner: pallial muscles, middle: sensory, outer: secretes shell, periostracal groove. Hinge ligaments: protienaceous (conchiolin, 2 adductor muscles, when the valves are closed by the adductor muscles, the outer hinge ligament is stretched and the inner ligament is compressed, fast twitch muscle, catch muscle. The periostracum seals the extrapallial space and isolates it from the surrounding environment. Circular pedal muscles contract, cause foot to elongate. Further contraction of the circular muscles forces blood into tip of foot causing it to swell, and making it a penetration anchor. Adductors contract, forcing water out of mantle cavity, loosening it. Anterior pedal retractors contract pulling down and rocking to the left.
