Dendronotus Density Dispatch

Today at Haystack a startling abundance of nudibranchs in the genus Dendronotus appeared.

The name Dendronotus is derived from dendrite, Greek for "treelike." In human anatomy, dendrites are the branching projections of brain cells that receive impulses, allowing us to perceive nudibranchs and feel wonder at their strangeness.

Upon close examination, these sea slugs with branching bodies did indeed appear treelike. They reminded me of miniature versions of Ents, the towering tree-creatures from Lord of the Rings. (First photo: An individual dendronotid sea slug against a background bryozoan.)

From a distance, however, the dendronotids looked like a dense growth of algae carpeting the floor of the pool. (Second photo: The "blob" in the left-hand corner is a slug "walking" upside down by moving its foot across the surface tension of the water; the "fuzzy growths" covering the sand are clusters of dendronotids in staggering numbers.)

Stranger than the appearance of these tidepool tree-animals is their hermaphroditic form of sexual reproduction; stranger yet is their ability to produce sounds audible to the human ear. A researcher keeping dendronotid specimens in an aquarium reported the sounds they made "resemble very much the clink of a steel wire on the side of the jar, one stroke only been given at a time, and repeated at intervals of a minute or two."

Scientists speculate that these beings at the edge of the alien sea might use their metallic sounds for mating, or maybe for defense.

I will return to the tidepools with ears wide open, listening for the call of a tiny tree-beast clicking into the deep as it searches for sex or fends off death.