Adult Age-Specific Embryonic Viability of the Northern Quahog

Abstract

Abstract This study assesses the viability of gametes produced by various age-classes of the northern quahog Mercenaria mercenaria (Linnaeus, 1758). Using weight of gonadal material, previous investigators concluded that reproductive senescence did not occur in older northern quahogs. However, the viability of the gonadal material in older clams was not determined in those studies. We established two replicates of eight age-groups (2–5, 6–10, . . ., 26–30, 31–34, and >34 years of age) and tested gamete viability. Age of clams had no significant effect on embryonic survival at 48 h. For all ages of parents, embryonic survival to day 2 was 20% with a range of 2. 1% to 32.8%. Within and among age-class groups, variability in survival levels was similar. Unfertilized egg size (mean ± SE) was 87.97 ± 0.25 um, and the size-frequency of eggs was normal. Individual unfertilized egg sizes (mean ± SE) ranged from 77.3 ± 1.07 to 100.5 + 1.19 μm. No linear relationship was evident between mean egg size and northern q...