The Trumpet
Worm: America’s Stone Mason
P996
Prentice K. Stout
A
stonemason is a master craftsman with years of training in his exacting
trade. The great European cathedrals are evidence of the artistry achieved
by such craftsmen, surviving them over centuries.
The trumpet worm, with little
else than two small tentacles and specialized mouth parts, no apprenticeship
required, constructs its building in miniature.
The low tides that lay bare
the sandy expanses of the tidal flats give this extraordinary animal its
habitat. Here, exposed for a brief time until the next rising tide, a
shell remarkably like an ice cream cone can be found. Less than two inches
long, it is composed of sand grains neatly fashioned and glued into a
mosaic of artistic precision. Because the shell is made form the very
sand on which it lives, it usually escapes notice.
This artifact is the domicile
of a worm related to the earthworm, but more closely to the clam worm
Neris Virens so highly prized as bait by fishermen. It belongs to the
class Polychaeta, meaning "many bristles."
The trumpet worm has also been
given the scientific name Pectinaria gloudi, "pectinaria" referring
to the sharp bristles that form the golden combs used to sift the sand
for food. While seemingly fragile, these body parts have amazing strength
and are used much like the blades of a bulldozer.
The formation of the shell
begins soon after the microscopic larva has ceased its planktonic swimming
stage. Carefully burrowing beneath the sandy substrate, out of sight and
hence hard to study, the larva begins its construction of intricate design.
To observe this process, A.T. Watson, a Scottish zoologist, captured larvae
and kept them in shallow dishes with just a few millimeters of sand on
the bottom. He noted that the tiny animal first secreted a membranous
tube about its soft, fleshy body. This became the inner lining of the
shell, providing a foundation on which to affix the mosaic of sand. It
is amazing that the larva has only two tentacles for collecting each particle
of sand and passing it into the mouth.
With attentive precision, each
particle is rolled about, and experimentally sized for the exact space
requirements on the shell. Once suitability has been determined, it is
deposited on a chosen spot at the edge of the tube. If the grain fits
the location, a special cementing fluid from a gland near the mouth is
employed and the grain is secured. Certain shield-like body structures
smooth the grains in place, making sure they fit tightly. Over and over
again this sizing technique is utilized, and more glue is applied until
the abode is completed.
The animal feeds beneath the
sand. Food is composed of microscopic plant and animal life that inhabit
its sandy substrate. Standing on its head, the animal sifts through the
particles, taking in the food and discarding the unwanted material. Throwing
the castoff material over its "shoulder" it swings from side
to side constantly in search of nutrients.
When the animal dies its art
survives; the shell finds its way to the surface of the sand by the action
of the waves, to be discovered by the sharp-eyed beach walker or crushed
by the pounding surf.
12/10/94
