DAO 112:219-228 (2015)  -  DOI: https://doi.org/10.3354/dao02811

Eroded swimmeret syndrome in female crayfish Pacifastacus leniusculus associated with Aphanomyces astaci and Fusarium spp. infections

Lennart Edsman1, Per Nyström2, Alfred Sandström1, Marika Stenberg2, Harri Kokko3, Vesa Tiitinen4, Jenny Makkonen3, Japo Jussila3,*

1Institute of Freshwater Research, Department of Aquatic Resources, Swedish University of Agricultural Sciences, 178 93 Drottningholm, Sweden
2Ekoll AB, Majgatan 17 b, 215 65 Malmö, Sweden
3Department of Biology, University of Eastern Finland, Kuopio campus, PO Box 1627, 70211 Kuopio, Finland
4South Karelian Fisheries Advisory Center, Hietakallionkatu 2, 53850 Lappeenranta, Finland
*Corresponding author:

ABSTRACT: We describe a novel syndrome in crayfish, eroded swimmeret syndrome (ESS), affecting wild female signal crayfish Pacifastacus leniusculus. ESS causes partial or total swimmeret erosion. We observed ESS only in female signal crayfish larger than 40 mm carapace length, i.e. sexually mature and probably having carried eggs at least once. The eroded swimmerets were melanised, indicating a crayfish immune system response. We isolated Fusarium tricinctum species complex (SC), F. sambucinum SC, Saprolegnia parasitica and S. australis from the melanised tissue of the eroded swimmerets. ESS includes chronic Aphanomyces astaci infection and a secondary infection by Fusarium sp. In Sweden, we found female signal crayfish with ESS in 6 out of 11 populations with a prevalence below 1% in lakes with commercially productive signal crayfish populations and higher than 29% in lakes with documented signal crayfish population crashes. In Finland, the ESS prevalence was from 3.4 to 6.2% in a commercially productive population. None of the sampled male signal crayfish showed signs of ESS. A caging experiment indicated that females with at least 1 lost swimmeret carried on average 25% fewer fertilized eggs compared to females with intact swimmerets. ESS could significantly reduce individual female fecundity and thus could also affect fecundity at the population level. The decline in reproductive success due to ESS could be among the factors contributing to fluctuations in wild signal crayfish populations.

KEY WORDS: Signal crayfish · Reproduction · ESS · Crayfish plague · Opportunistic infection

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Cite this article as: Edsman L, Nyström P, Sandström A, Stenberg M and others (2015) Eroded swimmeret syndrome in female crayfish Pacifastacus leniusculus associated with Aphanomyces astaci and Fusarium spp. infections. Dis Aquat Org 112:219-228. https://doi.org/10.3354/dao02811

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