Differentiation of Philonema spp. (Nematoda; Philometridae) in British Columbia Salmonid Fishes Using DNA Restriction Fragment Length Differences

Abstract

Restriction fragment length differences were compared in Philonema spp. (Nematoda; Philometridae) parasitizing kokanee and sockeye salmon (Oncorhynchus nerka) and rainbow and steelhead trout (Oncorhynchus mykiss) from various British Columbia localities. DNA extracted from individual worms was digested with various restriction enzymes and the resulting fragments were separated by horizontal gel electrophoresis to reveal bands representing cleavage sites within repetitive DNA sequences. Banding patterns reveal that worms from the two host species represent distinct genetic stocks. Kokanee and sockeye salmon from all localities sampled harboured the same stock of Philonema, identified as P. oncorhynchi. Worms from rainbow and steelhead trout were clearly distinguished from P. oncorhynchi and are assigned to P. agubernaculum. Philonema aguhernaculum from different localities were distinguishable by their banding patterns; material from Pennask Lake resembled that from Babine Lake and could be distinguished from that from O'Connor Lake on Vancouver Island. This similarity may indicate a common postglacial ancestor for Pennask Lake and Babine Lake worms, perhaps by postglacial colonization from the Columbia River system.