Differences in viability and reactivity of actinospores of three myxozoan species upon ageing

Abstract

Abstract.Little is known about the viability of myxozoan actinospore stages after harvest from laboratory cultures of infected oligochaete worms. The viability and reactivity of actinospores of three myxozoan species was evaluated after short-term storage at 4°C and 12°C. Two methods of determining actinospore viability were compared: differential fluorescent staining and direct microscopic observation of morphological indicators of spore integrity. Spore reactivity was quantified by measuring polar filament discharge rates in a micro-assay with fish mucus substrate and mechanical stimulation by vibration. The age-dependent viability of the three species showed clear differences. Myxobolus cerebralis actinospores had the shortest effective life span whereas Henneguya nuesslini actinospores survived significantly longer. Storage at lower temperatures yielded higher viability in all species. Myxobolus pseudodispar actinospores were significantly robust up to 12°C when assessed by staining, but showed similar viability characteristics as H. nuesslini when analyzed morphologically. Evaluation of spore viability by fluorescent staining correlated with morphological assessment, although fewer viable actinospores were usually detected microscopically. Polar filament discharge activity of morphologically intact actinospores did not significantly decrease until the third day of storage compared to freshly harvested samples. The results indicate that durability and reactivity trends during storage of actinospores differ among myxozoan species.

In vivo exposure of susceptible and non-susceptible fish species to Myxobolus cerebralis actinospores reveals non-specific invasion behaviour

“…As shown by qPCR detection, the staining procedure did not affect the ability of spores to attach onto the fish host surface. Although FDA may cause spontaneous discharge of polar capsules (Kallert & El-Matbouli 2008), it was not possible to measure whether a greater number of unstained actinospores would attempt penetration after anchorage to the host. Differences in absolute numbers of parasites found on rainbow trout gills in the different analyses (despite using the same spore concentrations) highlight the importance of using the same parasite aliquots for comparison of all samples.…”

“…Several other species of actinospores showed polar filament discharge or sporoplasm emission when they were offered mucus samples of non-susceptible hosts (Yokoyama et al 1993, 1995, McGeorge et al 1997, Özer & Wootten 2002, Yokoyama & Urawa 1997, Kallert & El-Matbouli 2008. However, reports on pronounced host specificity during reactions to host stimuli among actinospores are scarce.…”

Parental genetic diversity of brown trout (Salmo trutta m. fario) brood stock affects offspring susceptibility to whirling disease

“…TAMs were harvested by filtering the water from the culture containers through 20 μm mesh. TAMs used for the infection trials were less than 48 h old [47,48]. Fish were exposed individually to 3000 freshly filtered TAMs/fish in 500 ml dechlorinated tap water at 15°C for 3 h. Fifty-three individuals per group were exposed.…”

Modeling the Effects of Climate Change on Disease Severity: A Case Study of Ceratonova (syn Ceratomyxa) shasta in the Klamath River

“…However, actinospores may be more negatively affected by temperature than myxospores, which are comparatively stable due to the hardened valves that surround the sporoplasm (Hedrick et al 2008). For example, M. cerebralis actinospores remain viable for *15 days at 15°C and only 1 day at 23°C, whereas myxospores remain viable for >60 days at <10°C and 7 days at 22°C (El-Matbouli et al 1999;Hedrick et al 2008;Kallert and El-Matbouli 2008). Similar relationships were observed for C. shasta: actinospores were viable for *7 days at 4°C and for *4 days at 20°C and myxospores persisted for >150 days at 4°C and for 50 days at 20°C (Foott et al 2007;Bjork 2010;Chiaramonte 2013).…”