Sphaerothecum destruens: Life history traits and host range

• Main Author: Andreou, Dimitra
• Format: Thesis
• Language: English
• Published: 2010
• Subjects: QH301 Biology; Brama; Atlantic salmon
• Online Access: https://orca.cardiff.ac.uk/id/eprint/54976/; https://orca.cardiff.ac.uk/id/eprint/54976/1/U585365.pdf

Sphaerothecum destruens is a multi-host parasite which can infect and cause mortality in a number of fish species including Chinook salmon Oncorhynchus tshawytscha, Atlantic salmon S. salar and the sunbleak Leucaspius delineatus. It has been hypothesised that S. destruens has been introduced to the UK with its invasive hosts L. delineatus and topmouth gudgeon Pseudorasbora parva. As the effects of a novel parasite to naive populations could be detrimental, this thesis aimed to better elucidate the life cycle of S. destruens, its prevalence in wild populations and the susceptibility of cyprinid species. S. destruens was able to infect multiple organs (kidney, liver, gill, gonad and intestine) with similar histopathology between L. delineatus, a cyprinid species, and the histopathology reported for salmonid species. Its spore and zoospore life stages displayed a wide temperature tolerance and zoosporulation occurred at temperatures between 4-30 C. A survey of one UK location detected S. destruens in a wild L. delineatus population. A quantitative polymerase chain reaction was developed in order to quantify S. destruens' infection levels. Reproductive L. delineatus were more susceptible to S. destruens and experienced higher S. destruens prevalence and infection levels. The presence of a second host, P. parva, had no influence on S. destruens' prevalence and infection levels. However, presence of P. parva resulted in significantly lower somatic condition in parasitized female L. delineatus. Exposure to S. destruens through immersion in water containing S. destruens spores revealed that bream Abramis brama and carp Cyprinus carpio were susceptible to S. destruens. A. brama experienced high (53 %) mortalities when exposed to S. destruens whilst C. carpio experienced low (8 %) mortalities. The susceptibility of roach Rutilus rutilus and rudd Scardinius erythrophthalmus could not be excluded and needs to be further investigated.