Members of the Blastocladiales are saprobes and parasites that occur on a broad range of substrates. They are most easily found on decaying fruits (e.g., rose hips) and partially decorticated twigs. Thalli in the group can be monocentric or polycentric to mycelial in Allomyces spp. Several members of the order are facultative anaerobes and grow under foul conditions. Some representative genera are: Catenaria, Physoderma, Blastocladiella, Blastocladia, Coelomomyces and Allomyces. Physoderma spp. are parasitic on higher plants, Coelomomyces is parasitic on animals, and the other genera listed here are weak parasites or saprobes.
All members of this order have zoospores with a distinct nuclear cap that surrounds the nucleus. This ribosome-filled cap is easily observed with an oil immersion lens and phase contrast or differential interference microscopy. The nucleus has a pointed end that terminates near the kinetosome. In most members of the order, 27 microtubules radiate forward from the proximal end of the kinetosome and surround the nucleus in groups of three.
References, Keys and Illustrations:
Alexopoulous, C.J., Mims, C.W., and M. Blackwell. 1996. Phylum Chytridiomycota. In: Introductory Mycology. John Wiley & Sons, New York.
Karling, J.S. 1977. Chytridiomycetarum Iconographia. Lubrecht and Cramer, Monticello, New York.
Longcore, 1996. Chytridiomycete taxonomy since 1960. Mycotaxon 60: 149-174.
Sparrow, F.K. 1960. The aquatic Phycomycetes, 2nd edn. Rev. Univ Michigan Press, Ann Arbor.