We missed a great opportunity at Black Rock this year: hunting for crayfish worms aka branchiobdellidans. These tiny critters (<12 mm) are worms of the phylum Annelida, the same group that includes leeches, earthworms, and polychaetes.
Branchiobdellidans spend their whole lives on the exoskeleton of crayfish like the ones inhabiting the streams of Black Rock Forest. Some species may be parasitic, others muralists, sometimes it depends on their population density, and in most cases, we just don’t what impact - if any - branchiobdellidans have on their crayfish hosts.
With so little known about its ecology, it should comes as no surprise that their evolutionary relationships relative to other annelids, especially the true leeches (Hirudinida) and freshwater parasitic worms (Acanthobdellida) is equally murky. This murkiness is at the center of Michael Tessler, Magda and Olivia’s SRMP research.
Long story short: if you use shared characteristics in sperm morphology to recreate evolutionary relationships, you would find Hirudinida and Acanthobdellida
to be more closely related. But if you use the CO1 and 18S genes,Hirudinida and branchiobdellidans are more closely related.
Michael and his SRMP students are adding additional species and genes to form a more robust dataset to, hopefully, resolve the relationships. While Michael & Co work on that, I’ll practice saying “branchiobdellidans” 5x fast.