There are four main COI haplotypes of H. dedritifera suggesting that it may be a species complex with at least two different species, an arctic one (two haplotypes with 1 base pair difference: D16ROS and D28ROS) and a boreal one (two haplotypes with 1 base pair difference: D6ROC and DN3ROC). More specimens of the arctic haplotype from the Flemish Cap (off Newfoundland) were sequenced in Cárdenas (2016, p. 344).
Reveillaud, J.; Remerie, T.; Van Soest, R.; Erpenbeck, D.; Cárdenas, P.; Derycke, S.; Xavier, J. R.; Rigaux, A.; Vanreusel, A. (2010). Species boundaries and phylogenetic relationships between Atlanto-Mediterranean shallow-water and deep-sea coral associated Hexadella species (Porifera, Ianthellidae). <em>Molecular Phylogenetics and Evolution.</em> 56(1): 104-114. Available for editors [request]