Fig. 3.4 (a–s) Morphology of Hyphochytriomycota
and associated genera.(a–h) Drawings illustrating
development ofRhizidiomyces apophysatusparasitiz-
ing oogonia ofAchlya racemosa. An encysted spore
germinates to produce branched rhizoids and a swollen
apophysis (a–d) within the host tissue and an epibion-
tic papillate thallus (d–e). Mature thalli release an
undifferentiated spore mass (f) that differentiate extra-
sporangially (g) to form anteriorly flagellate zoospores
(h). An oogonium ofAchlyathat is heavily parasitized
byR. apophysatusshowing a range of thallus develop-
mental stages (i). (i–k) Drawings ofHyphochytrium
catenoidesshowing bead-like swellings interconnected
by short hypha-like segments (i) and part of a mature
rhizomycelial thallus showing elongate discharge tubes
(j) that give and uniflagellate zoospores (k). All from
Karling ( 1977 ). (m–r) Drawings ofAnisolpidium ecto-
carpiillustrating sexual reproduction in which adjacent
gametes encyst and release thalli, which immediately
fuse (m), followed by karyogamy (n–o). The fused cell
develops into a vacuolate sporangium (p), which differ-
entiates (q) into uniflagellate zoospores (r). From Kar-
ling ( 1981 ), after Johnson ( 1957 )Systematics of the Straminipila: Labyrinthulomycota, Hyphochytriomycota, and Oomycota 47