Whirling Disease: Reviews and Current Topics

Triactinomyxon Production as Related to Rearing Substrate and Diel Light Cycle

Ronney E. Arndt, Eric J. Wagner, Quinn Cannon, and Mark Smith

doi: https://doi.org/10.47886/9781888569377.ch8

ABSTRACT. The culture of the aquatic worm Tubifex tubifex, the alternate host of whirling disease, is necessary to conduct research regarding triactinomyxon (TAM) viability, controlled infection studies, and methods of disease control. Presumed infected worms collected from the field may produce TAMs for several months, but production generally decreases after a few months. To ensure a stable supply of TAMs, we investigated the effects of rearing substrate on TAM production and worm survival. We also analyzed the time of TAM release during 24-h periods divided into 12 h light:12 h dark.

Mixed species of field-collected worms were placed into culture with the following substrates: organic debris, silt, and sand. The controls were reared without a substrate. After nine weeks, worms in the silt substrate produced significantly more TAMs than worms in either the control or sand substrate. The worms in silt also produced significantly more TAMs than the worms in organic debris in four of seven bi-weekly samples where significant treatment differences were found. The estimated average daily TAM production during weeks 9–27 averaged 149 for control worms, 754 for the organic, 231 for the sand, and 2,573 for worms in the silt substrate. By the end of the study (week 27), average total worm weight for the controls was 0.8 g, 3.3 g for the organic, 2.6 g for the sand, and 7.5 g for the silt. The silt treatment had significantly higher worm mass than any of the other treatments, and was the only treatment to increase in mass from the starting weight of 4.5 g.

During two separate periods, worms were also observed for TAM release within 24-h cycles composed of 12 h light:12 h dark cycles. During the first period, there were slightly more TAMs released during the light period (59%) compared with 41% for the dark. For the second period, slightly more TAMs were released during the light period (56%) compared with 44% for the dark. For both tests however, these differences were not significant. These results indicate that, at least in the laboratory, there is no relationship between daylight hours and TAM production.