Total RNA from ,10 6 cells of both Perkinsus species and four strains of dinoflagellates in our previous studies [8] , [9] , including Prorocentrum minimum (CCMP696), Polarella glacialis (CCMP2088), Karenia brevis (CCMP2228) and Karlodinium veneficum (CCMP1975) were used for RNA blots. RNA samples were loaded onto an 8% acrylamide/8 M urea gel, a medium resolution gel optimal for RNAs below 350 nt, electrophoresed, and transferred to nylon membranes [22] . Oligonucleotide probes used for hybridization included dinoSLa/s for detection of the general dinoflagellate SL RNAs and the two types of Perkinsus SL RNAs (PmaSL-La/s and PmaSL-Sa/s hybridizing to exons and PmaSL-Li and PmaSL-Si to introns) ( Table 1 ). The cDNA clones containing the two P. marinus SL RNAs were dot blotted to serve as positive controls for detection of the specific substrate SLs on RNA blots. Total RNA from Leishmania tarentolae cells was included to provide size markers. Oligonucleotide probes were labeled with cP 32 -ATP for hybridization [22] .