. Bulletin. Natural history; Natural history. Aug. 1981 Dreier & Tranq^uilli: Corbicula 383 Table 1.âAverage numbers of larvae (veHger or trochophore) and eggs in marsupial gills of Corbicula from the three arms of Lake Sangchris during 1975- Five clanns from each area were examined on each date. Discharge Arm Intake Arm Control Arm Date Larvae Eggs Larvae Eggs Larvae Errs April 23 27 0 May 8 20 418 400 0 3 6 May 21 3,304 0 0 7,303 0 June 5 0 2 0 1,001 10 June 17 1,016 2 0 214 0 July 16 2 19 0 0 649 July 30 0 4 1,665 1,426 14 0 Aug 14 0 0 83 0 977 0 Aug 26 0 0 20 0
. Bulletin. Natural history; Natural history. Aug. 1981 Dreier & Tranq^uilli: Corbicula 383 Table 1.âAverage numbers of larvae (veHger or trochophore) and eggs in marsupial gills of Corbicula from the three arms of Lake Sangchris during 1975- Five clanns from each area were examined on each date. Discharge Arm Intake Arm Control Arm Date Larvae Eggs Larvae Eggs Larvae Errs April 23 27 0 May 8 20 418 400 0 3 6 May 21 3,304 0 0 7,303 0 June 5 0 2 0 1,001 10 June 17 1,016 2 0 214 0 July 16 2 19 0 0 649 July 30 0 4 1,665 1,426 14 0 Aug 14 0 0 83 0 977 0 Aug 26 0 0 20 0 0 2 Sept 14 0 0 23 0 233 0 Sept 23 4 0 220 2,281 0 0 Oct 8 1,129 0 3,399 1 0 0 Oct 22 6,196 0 55 4 4,684 0 Nov 14 97 0 1,379 0 81 0 Dec 31 0 0 2 0 24 1 at water temperatures above °C. The number of larvae in clams from the discharge and control arms on 21 May represented the maximum number found in those two arms during the spring or summer, whereas reproduction continued in the intake arm until an average of 8,954 larvae per clam was found on 16 July. Thus, a major spawn began in mid-May in all three arms of Lake Sangchris, lasting through mid- June in the discharge and control arms and through the end of July in the intake arm. Low levels of larval production occurred throughout the summer in the intake and control arms, but not in the discharge arm. Apparently, elevated water temperatures in the discharge arm during July and August (39° to 40»C) suppressed larval production there, whereas lower maximum temperatures (34°C) in the intake and control arms allowed larval production to continue. An increase in the production of larvae by clams in all three arms of the lake during the fall of 1975 indicated a second major spawn (Fig. 2) that started in the discharge and intake arms between 23 September and 8 October, when mean weekly water temperatures (N = 3) were ; and °C, respectively. Larval production increased in the control arm between 8 Oct
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