Effect of neuroactive compounds on larval metamorphosis of New Zealand geoduck (Panopea zelandica)

We present here the first laboratory study on the effects of pharmacologically active compounds on the larval metamorphosis of the New Zealand geoduck, Panopea zelandica (Quoy and Gaimard, 1835). Two batches of competent hatchery-reared larvae were exposed to acetylcholine chloride, epinephrine hydrochloride and excess potassium ions in the form of KCl and K2SO4. None of the tested chemicals increased the proportion of metamorphosed geoducks, and in some cases, the chemical caused significant mortality, despite having been used extensively with other species, such as mussels and oysters. This might indicate that geoduck larval physiology and development differs from other bivalves. Geoducks may have evolved distinct chemoreceptor patterns that facilitate metamorphosis under environmentally favourable conditions for subtidal soft sediment habitats suitable for burrowing. Thus, further research is needed to identify alternative cues (e.g. conspecific adults, sediment characteristics and surface biofilm) and understand their role in settlement and metamorphosis. This information will aid the design of reseeding methods and contribute to the development of reliable hatchery production of geoduck spat.