Parasitism On Graptoloid Graptolites

A review of evidence for parasitism on graptoloid graptolites is presented. The phenomenon is rare, having been recorded in only a few biserial forms and straight monograptids. Most periderm outgrowths secreted as a response to parasitism are small and blister‐like, but in two new specimens remarkable tubular outgrowths occur. These would have had a detrimental, but clearly not fatal, influence on the functioning of these graptolites, particularly with regard to the hydrodynamics and buoyancy of the rhabdosome and the energy expended in secreting additional periderm.