In the face of such an assault as by a reef glider, the ocean phantom has evolved a brilliant symbiotic defense mechanism.Some of the suction bells of ocean phantoms have ceased function as hunters. Instead, they are troop carriers. Should a reef glider be unlucky enough to brush against one of these modified bells, a horde of spindly-legged spindletroopers, with their slashing chelae and slicing chelicerae, emerges. It is an army come to the rescue of its host.
Throughout history (sea spiders in general dating back to the Late Cambrian), shallow water sea spiders have been small, ranging in size from 0.0390625 inch (1 millimeter) to over 2.25 feet (69 centimeters) in some deep water species. With a legspan of 11.78125 inches (30 centimeters), the spindletrooper is far larger than most of its relatives.
Before forming their symbiotic relationship with the ocean phantoms, spindletroopers live on the algal reefs, occasionally raiding an ocean phantom's suction bells for food. Soon some begin to remain safely inside the bells for longer periods of time. Eventually those particular spindletroopers adapt to fold up and fit nearly inside a suction bell, which in turn modifies itself to house and feed the spindletrooper.When hungry, an ocean phantom-guarding spindletrooper scratches at the walls of its home bell, stimulating it to regurgitate food from the rest of the colony. In return, the spindletrooper provides defense, coming out to fight when its ocean phantom colony is threatened. Spindletroopers have large chelicerae full of sharp fangs, capable of delivering an injection of painful venom. With these and their long chelae, they slash at anything that attacks their ocean phantom home.