WAR  of  the  MICROWORLDS  

How do I kill Thee?   Let me count the Ways!   (# 29)  click here for full list

(Images from Mycoalbum CD)

Pythium caudatum: This endoparasite of  nematodes produces large, biflagellate zoospores that mature in external vesicles after the protoplasm is extruded through filamentous evacuation tubes.   Originally described under Lagenidium this species was transferred to Pythium by Dick based on the large zoospores, the production of external vesicles, and the extensive filamentous thallus inside the host.  OOMYCOTAFor more information on this species see Barron, G.L. 1976. Can. J. Bot. 54: 1-4.

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Pythium (Lagenidium) caudatum

   Zoospores are attracted to secretions from the body orifices of nematodes e.g. buccal cavity (=mouth) and anus, and encyst in clusters at these locations (see diagram below).  Each cyst germinates to produce a fine hypha that passes through the body orifice into the host and proliferates to produce a tightly packed thallus of narrow assimilative hyphae.   These secrete enzymes to digest the body contents of the host completely.  At maturity filamentous evacuation tubes break out to the exterior at a number of points around the dead nematode.   A vesicle develops at the tip of each evacuation tube and protoplasm is evacuated into this vesicle.  Biflagellate zoospores then differentiate inside the vesicle.   The wall of the vesicle breaks down at maturity of the zoospores and they swim off to initiate attacks on new hosts.    The nature of its parasitic attack suggests that it is probably not host specific and may well have been described elsewhere on some other host.

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