Use of neuroactive catecholamines to chemically induce metamorphosis of hatchery-reared flat oyster, Ostrea angasi, larvae

Low numbers and unreliable wild catch of the native flat oyster, Ostrea angasi, spat has resulted in the NSW flat oyster industry being reliant on hatchery-produced spat. The need to produce culchless spat in the hatchery stimulated investigation of several catecholamines to induce metamorphosis in O. angasi larvae. Larvae were treated with one of four neuroactive catecholamines (epinephrine, epinephrine bitartrate, l-Dopa and GABA) at one of four concentrations (10 ^-3, 10 ^-4, 10 ^-5 or 10 ^-6 m) for one of three treatment durations (0.5, 1-2 h) to determine morphogenic action for culchless spat production. Epinephrine bitartrate at 10 ^-3 and 10 ^-4 m and epinephrine at 10 ^-3, 10 ^-4 and 10 ^-5 m, for a treatment duration of 1-2 h, produced significantly greater numbers of spat and culchless spat, compared with any other treatment combination. The other catecholamines tested did not induce a significant increase in the total number of spat or culchless spat, over untreated controls. Separate trials found that long-term treatment (24 h) with epinephrine bitartrate and epinephrine at morphogenic concentrations inhibited metamorphosis. Consecutive daily use of epinephrine bitartrate increased the numbers of spat and culchless spat produced, but did not affect larval or short-term post-larval survival. Treatment with 10 ^-3 m epinephrine bitartrate or 10 ^-4 m epinephrine for 1 h is recommended for routine commercial production of culchless flat oyster spat.