{"id":6420,"date":"2020-12-16T13:19:48","date_gmt":"2020-12-16T12:19:48","guid":{"rendered":"https:\/\/dev.asleman.org\/?post_type=60_secondes&p=6420"},"modified":"2020-12-16T13:19:48","modified_gmt":"2020-12-16T12:19:48","slug":"n66-saprolegnia","status":"publish","type":"60_secondes","link":"https:\/\/asleman.org\/en\/60_secondes\/n66-saprolegnia\/","title":{"rendered":"No.66: Saprolegnia"},"content":{"rendered":"

(WATCHING THE TROUT LEAVE THE LEMAN RIVER<\/a>) was the headline at the beginning of December, when ASL invited its readers to go and observe this particular phenomenon. Between November and December, \ud835\uddf9\ud835\uddf2\ud835\ude00 \ud835\udde7\ud835\uddff\ud835\ude02\ud835\uddf6\ud835\ude01\ud835\uddf2\ud835\ude00 \ud835\ude03\ud835\uddfc\ud835\uddfb\ud835\ude01 \ud835\uddfe\ud835\ude02\ud835\uddf6\ud835\ude01\ud835\ude01\ud835\uddf2\ud835\uddff \ud835\uddf9'\ud835\uddee\ud835\uddef\ud835\uddfc\ud835\uddfb\ud835\uddf1\ud835\uddee\ud835\uddfb\ud835\uddf0\ud835\uddf2 \ud835\uddf1'\ud835\uddf2\ud835\ude00\ud835\uddfd\ud835\uddee\ud835\uddf0\ud835\uddf2 \ud835\uddf2\ud835\ude01 \ud835\uddf1\ud835\uddf2 \ud835\uddfb\ud835\uddfc\ud835\ude02\ud835\uddff\ud835\uddff\ud835\uddf6\ud835\ude01\ud835\ude02\ud835\uddff\ud835\uddf2 \ud835\uddf1\ud835\ude02 \ud835\udddf\ud835\uddf2\u0301\ud835\uddfa\ud835\uddee\ud835\uddfb \ud835\uddfd\ud835\uddfc\ud835\ude02\ud835\uddff \ud835\uddff\ud835\uddf2\ud835\uddfa\ud835\uddfc\ud835\uddfb\ud835\ude01\ud835\uddf2\ud835\uddff \ud835\uddf9\ud835\uddf2\ud835\ude00 \ud835\uddf0\ud835\uddfc\ud835\ude02\ud835\uddff\ud835\ude00 \ud835\uddf1'\ud835\uddf2\ud835\uddee\ud835\ude02 and find a suitable place for them to breed.<\/p>\n\n\n\n

S\u0335a\u0335p\u0335r\u0335o\u0335l\u0335e\u0335g\u0335n\u0335i\u0335a\u0335. Sapristi. Here's one that jumps. By the way, doesn't she have \ud835\ude01\ud835\uddee\ud835\uddf0\ud835\uddf5\ud835\uddf2\ud835\ude00 \ud835\uddef\ud835\uddf9\ud835\uddee\ud835\uddfb\ud835\uddf0\ud835\uddf5\ud835\uddf2\ud835\ude00 on her body?<\/p>\n\n\n\n

Saprolegnia, Oomycetes, Oomycota, Chromista, a fine array of words to describe this micro-organism. In simpler terms, we can define \ud835\uddf9\ud835\uddf2 \ud835\uddf4\ud835\uddf2\ud835\uddfb\ud835\uddff\ud835\uddf2 \ud835\udde6\ud835\uddee\ud835\uddfd\ud835\uddff\ud835\uddfc\ud835\uddf9\ud835\uddf2\ud835\uddf4\ud835\uddfb\ud835\uddf6\ud835\uddee \ud835\uddf0\ud835\uddfc\ud835\uddfa\ud835\uddfa\ud835\uddf2 \ud835\ude02\ud835\uddfb \ud835\uddfd\ud835\ude00\ud835\uddf2\ud835\ude02\ud835\uddf1\ud835\uddfc-\ud835\uddf0\ud835\uddf5\ud835\uddee\ud835\uddfa\ud835\uddfd\ud835\uddf6\ud835\uddf4\ud835\uddfb\ud835\uddfc\ud835\uddfb \ud835\uddee\ud835\uddfe\ud835\ude02\ud835\uddee\ud835\ude01\ud835\uddf6\ud835\uddfe\ud835\ude02\ud835\uddf2.<\/p>\n\n\n\n

The Oomycetes class is known to be the most widespread 'fungal' (caused by fungi) disease in fish. Saprolegnia is a genus of this order. \ud835\uddd8\ud835\uddf9\ud835\uddf9\ud835\uddf2 \ud835\uddee \ud835\uddf3\ud835\uddee\ud835\uddf6\ud835\ude01, \ud835\uddf0\ud835\uddf2\ud835\ude00 \ud835\uddf1\ud835\uddf2\ud835\uddff\ud835\uddfb\ud835\uddf6\ud835\uddf2\u0300\ud835\uddff\ud835\uddf2\ud835\ude00 \ud835\uddee\ud835\uddfb\ud835\uddfb\ud835\uddf2\u0301\ud835\uddf2\ud835\ude00, \ud835\uddf9\ud835\uddf2\ud835\ude00 \ud835\uddf4\ud835\uddff\ud835\uddfc\ud835\ude00 \ud835\ude01\ud835\uddf6\ud835\ude01\ud835\uddff\ud835\uddf2\ud835\ude00 by attacking trout, particularly in the Doubs. But the fungus is also fond of Grayling and Loche.<\/p>\n\n\n\n

The genus is often presented as a \ud835\uddfc\ud835\uddfd\ud835\uddfd\ud835\uddfc\ud835\uddff\ud835\ude01\ud835\ude02\ud835\uddfb\ud835\uddf6\ud835\ude00\ud835\ude01\ud835\uddf2 \ud835\ude00\ud835\uddee\ud835\uddfd\ud835\uddff\ud835\uddfc\ud835\uddfd\ud835\uddf5\ud835\ude06\ud835\ude01\ud835\uddf2. That is, they feed on inert organic matter such as dead fish eggs. However, some species are \ud835\uddfd\ud835\uddee\ud835\uddff\ud835\uddee\ud835\ude00\ud835\uddf6\ud835\ude01\ud835\uddf2\ud835\ude00, feeding at the expense of a living \"host\".<\/p>\n\n\n\n

The fungus will attack the mucosa and epidermis of the fish, \ud835\uddee\ud835\ude02\ud835\ude01\ud835\uddff\ud835\uddf2\ud835\uddfa\ud835\uddf2\ud835\uddfb\ud835\ude01 \ud835\uddf1\ud835\uddf6\ud835\ude01 \ud835\uddf9\ud835\uddee \ud835\uddf0\ud835\uddfc\ud835\ude02\ud835\uddf0\ud835\uddf5\ud835\uddf2 \ud835\uddf2\ud835\uddfb\ud835\ude01\ud835\uddff\ud835\uddf2 \ud835\uddf9\ud835\uddf2\ud835\ude00 \ud835\uddf2\u0301\ud835\uddf0\ud835\uddee\ud835\uddf6\ud835\uddf9\ud835\uddf9\ud835\uddf2\ud835\ude00 \ud835\uddf2\ud835\ude01 \ud835\uddf9\ud835\uddee \ud835\uddf0\ud835\uddf5\ud835\uddee\ud835\uddf6\ud835\uddff. Infected fish show fungal mats of different colours. While the \ud835\uddf4\ud835\uddff\ud835\uddf6\ud835\ude00\ud835\uddf2 colouration (or even brown or green) suggests a chronic infection soiled by particles in the water and algae, the \ud835\uddef\ud835\uddf9\ud835\uddee\ud835\uddfb\ud835\uddf0 \"cotton\" appearance indicates an acute infection.<\/p>\n\n\n\n

Most of the trout that spawn (swim up the tributaries of Lake Geneva to reproduce) are infested by the fungus. Most often, \ud835\uddf9\ud835\uddf2 \ud835\uddfd\ud835\uddfc\ud835\uddf6\ud835\ude00\ud835\ude00\ud835\uddfc\ud835\uddfb \ud835\uddf2\ud835\uddfb \ud835\uddef\ud835\uddfc\ud835\uddfb\ud835\uddfb\ud835\uddf2 \ud835\ude00\ud835\uddee\ud835\uddfb\ud835\ude01\ud835\uddf2\u0301 \ud835\uddf9\ud835\ude02\ud835\uddf6 \ud835\uddff\ud835\uddf2\u0301\ud835\ude00\ud835\uddf6\ud835\ude00\ud835\ude01\ud835\uddf2. However, the genus Saprolegnia can become lethal for trout tired by travelling and forming their spawning grounds by stirring up gravel. This weakening by Saprolegnia can also be a gateway to other pathogens.<\/p>\n\n\n\n

Some of these strains are even directly fatal to fish. This is the case with Saprolegnia Parasitica, which has been rampant for around ten years in the Doubs, but has also been observed in other rivers such as the Versoix. Don't panic on our side, \ud835\uddf9\ud835\uddf2 \ud835\uddf4\ud835\uddf2\ud835\uddfb\ud835\uddff\ud835\uddf2 \ud835\udde6\ud835\uddee\ud835\uddfd\ud835\uddff\ud835\uddfc\ud835\uddf9\ud835\uddf2\ud835\uddf4\ud835\uddfb\ud835\uddf6\ud835\uddee \ud835\uddfb\ud835\uddf2 \ud835\uddff\ud835\uddf2\ud835\uddfd\ud835\uddff\ud835\uddf2\u0301\ud835\ude00\ud835\uddf2\ud835\uddfb\ud835\ude01\ud835\uddf2 \ud835\uddee\ud835\ude02\ud835\uddf0\ud835\ude02\ud835\uddfb \ud835\uddf1\ud835\uddee\ud835\uddfb\ud835\uddf4\ud835\uddf2\ud835\uddff \ud835\uddfd\ud835\uddfc\ud835\ude02\ud835\uddff \ud835\uddf9\ud835\uddee \ud835\ude00\ud835\uddee\ud835\uddfb\ud835\ude01\ud835\uddf2\u0301 \ud835\uddf5\ud835\ude02\ud835\uddfa\ud835\uddee\ud835\uddf6\ud835\uddfb\ud835\uddf2.<\/p>\n\n\n\n

Photo credits :<\/p>\n\n\n\n

\"\ud83d\udcf8\" Humbert ENS, Berrebi ONEMA<\/a><\/p>\n\n\n\n

Sources : <\/p>\n\n\n\n

\"\ud83c\udf10\" B. Austin (2012), \"Bacteria and bacteriophages as biological agents for disease control in aquaculture\", in. Infectious Disease in Aquaculture: Prevention and Control, 353-393
\"\ud83c\udf10\" J. Meyer, T. M. Donnely (2013), \"Saprolegniasis\", in. Clinical Veterinary Advisor: Birds and Exotic pets, 64-65.
\"\ud83c\udf10\" RTS (2014), \u201cSaprolegnia fungus identified in the Aar, Inn and Versoix rivers\u201d.\u201d<\/a>
\"\ud83c\udf10\" Le Temps (2012), \u201cKiller fungus plagues fish in the Doubs, Loue and Sorne rivers\u201d.\u201d<\/a><\/p>\n\n\n\n

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