Autotomy of Globiferous Pedicellariae in the Sea Urchin: Lytechinus variegatus (Echinodermata: Echinoidea)

Abstract

Pedicellariae are small structures on sea urchins used in cleaning the test and in defense. In most species, when globiferous pedicellariae (one of 4 types) contact an object it causes the pedicellariae to grasp the object in a defensive reaction. Very few instances have been documented where pedicellariae are released into the water column. Lytechinus variegatus was exposed to 4 treatments of control, physical tapping, water swirling around the animal, and direct jet of water at the animal in 4 separate experiments including two live field tests, an anesthetized test, and a euthanized test. Globiferous pedicellariae were released into the water in response to the direct jet of water, with the greatest response seen in individuals tested in the field and the least response in euthanized urchins. The other treatments did not elicit a large response. Release of pedicellariae into the water may be a preemptive defense before coming in physical contact with a predator.