The gastrotrich is a microscopic creature native
to both marine and freshwater environments. It grows to
a maximum of 3 mm in size and is flat, transparent and
rather
like a pineapple.
Intellectually, gastrotrichs appear to be on
the simple side; two ganglia, each attached to a single nerve cord
and connected by a commisure, are the whole of their think-box. However, they have been observed to display shockingly complex social
behaviours, acting in a way that ought to be precluded by their
limited mental capacities.
Gastrotrich spend their short three-day lifespans
in herd-like schools of 40-50 members. They spend 9-12 hours of each day
inactive, although not, strictly speaking, in a sleep-state. During
this time, the gastrotrich layer themselves atop each other to
form a sphere with the most juvenile of their number at its centre.
The surface of this conglomerate sphere will then gently expand and
contract, in a pulsing manner some say resembles the movements of certain species of Ctenophora. Although now believed to
be a form of Batesian mimicry, earlier researchers were perplexed,
one of them famously likening the behaviour to "some kind of noodly potluck".1
This is the origin of the expression "crowded as a gastrotrich
potluck", still in use in anatomy labs across the
Eastern United States (the site of most early gastrotrich research).
Most surprising of all, however, is an event that
occurs only once every five years, or so the last six decades of
observation has led scientists to believe. At such time, either on the evening of June 15 or the morning of June 16, depending on one's
timezone, gastrotrichs will form 'fleets' consisting of nine- to
ten-thousand specimens. How such primitive organisms locate each
other, sometimes travelling most of their brief lives to do so, is a
complete mystery, second only to the puzzle of how it is they know
when to do it. Statistically speaking, only about one in
six-hundred gastrotrichs will live during a quinquennial Fleet
Day. During these Fleet Days, gastrotrichs do not gather in their usual
sphere-states but rather collaborate to form larger and more complex
arrangements and designs. The most common motif by far is a series of
great arrows pointing to the bottom of the sea. In the case of
freshwater gastrotrichs, these arrows will simply indicate the
direction of the nearest ocean or sea; this phenomenon does not depend
on the colony having had direct experience of such bodies of water and
has even been observed in freshwater tanks in no way connected to the
ocean.
Despite the advanced state of study in modern marine microbiology labs, the gastrotrich remains a perennial 'problem species'. Group behaviour may be partly innate, but even so it must still be stored within the animal mind — and scientists are
at a loss as to where exactly the gastrotrich has found the room. Recent years have seen a renaissance in Gastrotrichology,
and the emergence of several high-profile research labs devoted solely to the organism. The largest and best-funded of these is the
Gastrotrich Language Project at MIT, a group whose mandate is establishing lines of
communication with the gastrotrich by means of flavoured jelly arrays.
1Dr. Harold Cowper, American
Gastrotrichology in its Infancy, New York: Cambridge University Press, 2005