Citation:

Specht, D. AND H. II. DIRECT MEASUREMENT TECHNIQUE FOR THE DETERMINING VENTILATION RATE IN THE DEPOSIT FEEDING CLAM, MACOMA NASUTA (BIVALVIA, TELLINACEAE). U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-89/142 (NTIS PB90125733), 1989.

Description:

An exposure chamber, the "clambox", was developed to measure ventilation rate, sediment processing rate, and efficiency of pollutant uptake byMacoma nasuta Conrad, a surface surface deposit-feeding clams. Clams, collected from Yaquina, Bay, Oregon, USA, were cemented into a hole in a piece of rubber dental dam so that the inhalant and exhalant siphons were seperated by a membrane. he dental dam was then clamped between two glass chambers. The inhalant and exhalant siphons were thus directed into separate chambers of the device so that the amounts of water or feces discharged into the exhalant chamber provided direct measures of ventilation rate and sediment processing rate respectively. Clams exhibited no stress from the procedure. entilation rate was not affected by the imposition of a 5mm hydraulic head in the exhalant chamber, by having sediment only in the inhalant chamber, or by exposure to organic-free sediment. he mean weight-specific ventilation rate for M. nasuta was 7.3 ml g -1h-1 on a wet-flesh basis. his low rate, compared to rates for filter-feeding bivalves, supports the contention that deposit-feeding is the dominant feeding mode for M. nasuta. he short-term pattern was for ventilation and then a resumption of the normal rate. ess than 3% of the total water flux could be attributed to water which entered the body cavity across the mantle margin. ater exhaled from the inhalant siphon during the ejection of pseudofeces was <10% of the ventilation rate. he clambox technique should be adaptable to studies on other tellinid bivalves.

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