. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 142 O. ELLERS water. The general shape of these clams is also relevant. Using calipers, basic dimension measurements were made of the anterior-posterior, ventral-dorsal, and left-right distances on the same clams. The densities of other bivalve species, chosen haphaz- ardly on North Carolina beaches, were determined in the same way (three specimens each of seven species were measured). Specimens of the same size as a large individ- ual of D. variahilis (2-3 cm long) were used to minimize potential allometric effects on the c
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 142 O. ELLERS water. The general shape of these clams is also relevant. Using calipers, basic dimension measurements were made of the anterior-posterior, ventral-dorsal, and left-right distances on the same clams. The densities of other bivalve species, chosen haphaz- ardly on North Carolina beaches, were determined in the same way (three specimens each of seven species were measured). Specimens of the same size as a large individ- ual of D. variahilis (2-3 cm long) were used to minimize potential allometric effects on the comparison. Density, weight distribution, and size effects on orientation Motions of D. variabilis shells of various sizes with ex- perimentally altered density and weight distribution were qualitatively observed in steady flows up to 60 cm s~' in a recirculating flow tank. Tendency to orient and the flow speed at which orientation occurred were noted. Weight distribution was altered by placing Plasticene in the posterior end and an air bubble in the anterior end (and vice versa), of empty D variabilis shells. (Altering weight distribution also unavoidably altered density.) Density was altered by completely filling empty D. var- iabilis shells with candle wax, Silicone rubber or Plasti- cene; the resulting densities of filled shells were and (X103 kg irT3), respectively. (Altering density un- avoidably alters weight distribution slightly.) Shells were placed in flow with four initial orientations: ventral, dorsal, posterior, or anterior edges upstream. 20 -, o C3 HI 10 -. WIND VELOCITY (ms-1) Figure .V The wind-speed distribution in the tunnel in which pressure measurements on the clam model were made. The mainstream velocity was equivalent to 'in seawater. The clam was well inside the boundary layer, and is shown for scale (it was not in the tunnel while the speed distribution was measured). Error bars show I SD. 10-, 5- n Q. CO LLJ cc Pl
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
