Aquatic Fungi of Iceland: Pythium

Abstract

SUMMARY Descriptive notes are given for the following species of Fythium recovered from soil and water in various localities in Iceland: P. debaryanum, P. dissotocum, P. echinulatum, P. gracile, P. inflatum, P. mamillatum, P. middletonii, P. monospermum, P. pulchrum, P. rostratur, P. tenue, P. torulosum, P. ultimum, P. undulatum, and P. vexans. A form of P. tenue is reported as a possible intermediate between this species and P. gracile, and a species (of the filamentous sporangiate series) lacking an antheridial apparatus is described but not named. Representatives of Pythium Pringsheim, particularly those forms that fail to produce the sexual apparatus in gross or pure culture, are common in Iceland. Earlier (13), four species were identified, and notes on two unnamed representatives were subsequently (11) published. In this paper I present a descriptive and taxonomic account of sixteen aquatic species of Pythium found in Iceland. One of the two unnamed taxa described in 1969 (11) is assigned to Hesse's Pythium debaryanum on the basis of morphological evidence from cultures grown on hempseed. Save for the species occurring in algae, the fungi reported were isolated and propagated on potato dextrose agar (Difco, dehydrated). Subsequently, the isolates were grown on hempseed halves in sterile, distilled water, and characterized. Specimens preserved on slides are deposited in collections in the Museum of Natural History, Reykjavik. A key to the species of Pythium [exclusive of one unnamed taxon (11)] now known to occur in Iceland, follows.