NOREPINEPHRINE AND DOPAMINE CONTENT OF LARVAE AND SPAT OF THE PACIFIC OYSTER, CRASSOSTREA GIGAS

Oyster larvae and spat of varying ages were homogenized and analyzed for catecholamine content using high-performance liquid chromatography with electrochemical detection. Norepinephrine (NE) and dopamine (DA) were found in appreciable quantities, with more DA present than NE. The presence of epinephrine was equivocal. Norepinephrine levels were low in young larvae (0.062 ± 0.035 pg/µg protein), then increased to an intermediate level (0.517 ± 0.031 pg/µg protein) for most of the larval period and finally increased again just before metamorphosis to 1.08 ± 0.09 pg/µg protein. Dopamine levels in the corresponding larval groups did not change significantly, with 11.5 ± 1.9, 8.58 ± 0.98, and 7.47 ± 0.92 pg DA/µ protein, respectively. The levels of NE (1.00 ± 0.04 pg/µg protein) and DA (7.13 ± 0.29 pg/µg protein) present in spat following metamorphosis were not significantly different from the pre-metamorphic values. The presence of NE in oyster larvae at the time of metamorphosis supports the hypothesis of a role for endogenous NE in mediating metamorphosis.