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 £at oyster, Ostrea angasi, spat has resulted in the NSW £at 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 (103,104,105 or106 M) for one of three treatment durations (0.5,1^2 h) to determine morphogenic action for culchless spat production. Epinephrine bitartrate at 103 and 104 M and epinephrine at 103, 104 and 105 M, for a treatment duration of 1^2 h, produced signi¢cantly greater numbers of spat and culchless spat, compared with any other treatment combination. The other catecholamines tested did not induce a signi¢ cant increase in the total number of spat or culchless spat, over untreated controls. Separate trials found that long-termtreatment (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 aiect larval or short-term post-larval survival. Treatment with 103 M epinephrine bitartrate or 104 M epinephrine for 1h is recommended for routine commercial production of culchless £at oyster spat.