Portuguese Man-of-War

Portuguese Man—of—War

In 1941, on a sweltering August afternoon, a boy ran screaming from the surf off Rockaway Beach, New York. Bathers tore at the bluish strings that were draped over the boy's neck and shoulders, and soon they too were writhing in agony. The boy had encountered a Portuguese man—of—war.

Viewed from shipboard, a fleet of Physalia makes an impressive sight. They look like iridescent blue—purple balloons floating gracefully on a white—crested sea. To the British sailors of three centuries ago they looked like miniature Portuguese galleons and thus were named the Portuguese man—of—war.

The float is really part of an enormous colony of jellyfish all living together as a single organism. Each member of the colony performs a particular function ranging from reproduction to searching for food. Just under the float are digestive polyps whose sole function is feeding. The digestive nutrients are distributed to each member of the colony.

Hanging from the float are many hunting tentacles that may range up to sixty feet in length. These tentacles bear thousands of stinging capsules that secrete a poison as potent and toxic as that of a cobra. There is no known antidote to it, and a human, depending on health and age, can succumb in minutes. Even a beached Physalia is dangerous, and to step on a dried blue string will cause an excruciating hotfoot or worse.

Like the rhinoceros groomed of insect pests by the tickbird, the Physalia has its own symbiotic relationship. Nomeus, a small fish immune to the deadly poison, darts in and out of the mass of tentacles. Swimming in circles, it lures larger fish looking for a meal into what must appear to be a forest of seaweed. Here the victim is quickly overwhelmed by the lethal tentacles, Thus little Nomeus procures prey for the jellyfish and in return is protected and fed by tearing pieces from the victims.

The immense jellyfish is well adapted to survive harsh weather without any particular strain. During a storm Physalia deflates its bladder, thereby losing buoyancy. It then sinks below the surface, safe from churning waves until the sea is calm again. Within a few minutes it can reinflate itself by producing gas from a special gland.

As deadly and invulnerable as this jellyfish appears, it does have a natural enemy — the huge, lumbering loggerhead turtle. Five—hundred—pound turtles have been observed plowing through colonies of Physalia with their mouths trailing strings of tentacles like blue streamers from a maypole. In their wake the water is clear, but on either side are bobbing blue floats and streamers that are at last quite defenseless. The Portuguese man—of—war has met its match and lost.

From the book: 
Our Fascinating Earth