PCR detection of the crayfish plague pathogen in narrow-clawed crayfish inhabiting Lake Eğirdir in Turkey

Abstract

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...

Differing virulence of Aphanomyces astaci isolates and elevated resistance of noble crayfish Astacus astacus against crayfish plague

“…In Finland, the discussion has focused especially on the As-genotype and its virulence, which in recently reported cases seems to be lowered (Jussila et al 2011a. Similar observations have also been made in Turkey , Svoboda et al 2012, which is within the current distribution range of the As-genotype (Royo et al 2004).…”

“…Along with these new detection methods, several reports of European crayfish species with a latent infection of A. astaci, or acting as carriers of crayfish plague, have been published (Jussila et al 2011a, ViljamaaDirks et al 2011, Pârvulescu et al 2012, Svoboda et al 2012. In Finland, the discussion has focused especially on the As-genotype and its virulence, which in recently reported cases seems to be lowered (Jussila et al 2011a.…”

Aphanomyces astaciPsI-genotype isolates from different Finnish signal crayfish stocks show variation in their virulence but still kill fast

“…In general, this disease has a bad reputation, but some A. astaci strains seem to show signs of avirulence (Jussila et al, 2011a;Makkonen, 2013). Certain strains of this parasite have likely adapted to their fairly recent European hosts, as the As-genotype is currently causing highly variable mortalities among native European crayfish both in laboratory experiments and among wild populations (Jussila et al, 2011Kokko et al, 2012;Svoboda et al, 2012;Caprioli et al, 2013;Kušar et al, 2013). So far, however, the evidence of virulence differences and potential evolution among PsI-genotype, or other more recently introduced A. astaci genotypes, has been lacking.…”

“…Chitinase production has been claimed to be adaptation to parasitic life style and one of the virulence factors (Unestam, 1966;Hochwimmer et al, 2009). The reports of A. astaci adaptation to the European crayfish hosts (Jussila et al, 2011;Viljamaa-Dirks et al, 2011;Kokko et al, 2012;Svoboda et al, 2012;Kušar et al, 2013) are most probably all concerning As-genotype adaptation. The 150 year history in Europe, with high selection pressure, has caused a rather rapid co-evolution of both the host and the pathogen.…”

Variation in Resistance to the Invasive Crayfish Plague and Immune Defence in the Native Noble Crayfish

“…This indicates that individual-and population-specific differences in disease resistance potentially play a role in the crayfish plague dynamics (Makkonen et al 2012b) and have prolonged the existence of the disease in certain waters. Furthermore, there are recent reports on population recoveries after crayfish plague epidemics among the Turkish narrow clawed crayfish populations (Harlioğlu 2008, Kokko et al 2012, Svoboda et al 2012. These crayfish carry the infection and are commercially exploited despite the lack of a long co-evolutionary history with A. astaci.…”