Meeting Abstract
The genus Ototyphlonemertes is diagnosed by the presence of a pair of statocysts and is the iconic representative of the Phylum Nemertea among marine mesopsammic meiofauna. The genus comprises 26 species thought to be valid but up to 90 varieties have been reported based on morphology alone. This variety can be captured by six general morphotypes but these lack evident synapomorphies. The genus represents a paradox among nemerteans. It consists of the smallest worms in the phylum, evidently achieved by miniaturization and reduction of structures. Yet, the proboscis exhibits greater variation than is known for the remainder of the Order Monostilifera (excluding symbiotic species). A number of these characters, however, are continuous variables of relative size or proportion, and it’s unknown the extent to which these are intra-specific ecological variables versus representing interspecific diagnostics. DNA sequence data allege multiple instances of sympatrically occurring cryptic species that could not be distinguished morphologically, suggesting that there are substantially more species than anticipated by morphology. One can recognize readily two apparent clades of Ototyphlonemertes, one with polygranular statocysts and a helically sculpted proboscis stylet, and one with oligogranular statocysts and a smooth stylet. Recent DNA evidence supports uniting these as a monophyletic clade but unpublished phylogenetic analyses with many species reveal the two groups as either reciprocally monophyletic or offer conflicting paraphyletic results. DNA sequences suggest a recently re-discovered species appears to resolve the question. We also use DNA sequence data to test monophyly of the six morphotypes.
