In vitro cultivation and temperature-dependent growth of two strains of Spironucleus barkhanus (Diplomonadida: Hexamitidae) from Atlantic salmon Salmo salar and grayling Thymallus thymallus

Abstract

Spironucleus barkhanus from muscle abscesses of farmed Atlantic salmon Salmo salar L., and from the gall bladder of grayling Thymallus thymallus (L.) was cultivated axenically in a medium routinely used for cultivation of the human pathogen Giardia duodenalis. Trophozoites multiplied by binary division, but multinucleated cells (<10 nuclei) were frequently observed. Complete cell divisions were never observed in these cells. Both strains grew at all temperatures tested (5, 10, 15 and 20°C). However, continuous growth of the salmon strain at 20°C was not possible. Growth potential, calculated as minimum generation time, showed relatively small differences both between strains and among temperatures, but the results indicate that the grayling strain had both a slightly higher optimum temperature and a higher upper temperature limit than the salmon strain.