Many populations of the narrow-clawed crayfish Astacus leptodactylus in Turkey, including those inhabiting Lake Eg irdir, declined drastically in the mid-1980s due to introduction of crayfish plague Aphanomyces astaci. However, unlike many other localities, there has been some recovery in the A. leptodactylus population inhabiting this lake even though crayfish plague has been suspected to have persisted since then. In support of this, DNA from 5 of 34 healthy-looking crayfish sampled recently from the lake tested positive by both conventional and real-time PCR using species-specific primers targeting the rDNA internal transcribed spacer region, and product sequence analysis confirmed the identification of A. astaci. This complies with other recent reports of coexistence of native European crayfish with this pathogen, and further research is now needed to identify the key mechanisms allowing it.KEY WORDS: Aphanomyces astaci · Astacus leptodactylus · Host−pathogen coexistence · Melanisation · rDNA-internal transcribed spacer sequence · Lake Eg irdir
Resale or republication not permitted without written consent of the publisherDis Aquat Org 98: [255][256][257][258][259] 2012 dramatically reduced. However, there were exceptional cases where crayfish numbers either remained continuously high or recovered enough to sustain commercial harvesting despite the presumed presence of the crayfish plague pathogen (Rahe & Soylu 1989, Harliog lu 2004, 2008.Crayfish resistance and/or unique water chemistries have been assumed as reasons facilitating the long-term coexistence of Aphanomyces astaci in crayfish inhabiting such lakes (Rahe & Soylu 1989, Harliog lu 2008. A. astaci was unambiguously proven as the cause of crayfish mortalities in the 1980s (Baran & Soylu 1989, Rahe & Soylu 1989, Huang et al. 1994. However, its later presence in Turkish lakes (e.g. Aydin & Dilek 2004, Harliog lu 2004, 2008 has only been assumed from symptoms that are not specific for the crayfish plague pathogen (Cerenius et al. 1988, Oidtmann et al. 1999. As A. astaci should not survive at a locality when its crayfish hosts disappear (Söderhäll & Cerenius 1999) and its presence in Turkey after 1989 has not been proven definitively, its distribution in the country might now be more restricted than assumed.The narrow-clawed crayfish population inhabiting Lake Eg irdir (Isparta Province; 38°N, 31°E, altitude 917 m above sea level [a.s.l.], area 482 km 2 ) collapsed in 1986, presumably due to crayfish plague (Fürst & Söderhäll 1987). By 1999, numbers recovered sufficiently to allow commercial harvesting, although catch sizes have been lower and prone to fluctuations (Fig. 1). The aim of this study was to examine Lake Eg irdir crayfish using PCR and rDNA sequence analysis to test for the contemporary presence of A. astaci.
MATERIALS AND METHODSOver 2 occasions in 2009, a total of 32 crayfish (mean body length ± SD: 111 ± 22 mm) were caught in fyke-net traps in the southern part of Lake Eg irdir (37°53' N, 30°53' E). In March, 2 egg-bearing fem...
