Tissue-specific expression of candidate Aplysia chemoreceptors. Schematic representation of Aplysia californica showing the location of selected sensory tissues (rhinophore, oral tentacle, skin), central nervous system (CNS) and reproductive organs (albumen gland (AG), ovotestis, large hermaphroditic duct (LHD)) used for RNA isolation and RT-PCR. Amplification products were 756 bp, 832 bp, 512 bp for AcCRa, AcCRb and AcCRc, respectively. The PCR control, using water instead of cDNA, was negative (cont -ve). Actin cDNA was amplified from each tissue preparation (224 bp).