Few people ever observe the world's most prevalent animal, but scrutiny by University of Hawaii researchers may change the way scientists look at the little insect-like ocean-dwelling invertebrates known as calanoid copepods. The UH researchers have discovered that nerve cells of the species Undinula vulgaris are coated with myelin -- a substance generally thought to be limited, with very few exceptions, to humans and other vertebrates. If upheld, their findings, which are reported in the April 15 issue of the journal Nature, will require revision of basic biology textbook discussions of the difference between vertebrates and invertebrates.
Researchers at the University of Hawaii at Manoa's Pacific Biomedical Research Center, observed myelin in transmission electron microscope images of the calanoid copepods collected in Oahu's Kaneohe Bay. The authors had previously observed that Undinula vulgaris are unusually fast in sprinting from danger -- responding to stimuli about a hundred times faster than humans. Myelin is a white fatty sheath that coats parts of the vertebrate nervous system, including the long axons of nerve cells. Like insulation on an electric wire, myelin protects and speeds the electrical signal, providing a competitive advantage for organisms that must respond quickly to capture food or escape predators. Such an advantage is particularly important for large animals, in which nerve signals must travel long distances from sensory cells to brain and brain to muscles, and scientists had assumed myelin was a feature nearly exclusive to vertebrates.
Most calanoid copepods are only 3 millimeters long or less and eat phytoplankton
(plant plankton), other zooplankton or detritus. The most prevalent of the
zooplankton, they constitute the biggest source of protein in the ocean and form
a critical link in the marine food chain between the phytoplankton on which they
feed and the krill, fish and whales that feed on them. In essence, they are the
Contact: Petra Lenz
University of Hawaii