Abstract
A new species of turbellarian, provisionally placed in the genus Paravortex (Graffillidae, Rhabdocoela) is a parasite of marine tropical fishes and has become a conspicuous problem in saltwater aquaria. The worm infects fishes in several families and is most often seen on the yellow tang Zebrasoma flavescens, which is the principal host in this study. Worms increase in length and then leave the host. Off-host worms continue to grow and as many as 160 young develop within them. Ciliated young discharged from a rupture in the body wall of the adult quickly reinfect available hosts, and this alternate on and off-host pattern results in a periodicity of infections. The life cycle requires about 10 days at 24.5°C, with infections of as many as 4500 worms per fish after three generations. Heavily infected fish, with worms concentrated on the body, develop an acute focal dermatitis with an associated Vibrio infection. A formalin bath was effective in eradicating the parasite, but neon gobies (Gobiosoma oceanops) were ineffective as cleaner fish and they became infected as well.
