Larvae of the different groups
of
bivalves grow at different rates.
Those of scallops and clams have initially larger D-larvae
and
reach settlement size
and
metamorphosis at a considerable smaller shell length (210 to 230 µm) than do larvae
of
the oviparous oysters (320 to 340 µm).
Comparative growth rate
of
a number of species cultured at 24+2ºC is shown in Figure 66.
Some species,
including the calico scallop,
are slower in reaching an exponential rate of growth.
They tend to have a lag phase before rapid growth commences.
Others like the Manila clam
and
Pacific oyster grow rapidly from the initial D-stage.
Growth rate slows in all species as they approach the settlement stage.