KERATINOPHILIC CHYTRIDS. II. PHLYCTORHIZA VARIABILIS N. SP.

IN THE INITIAL publication of this series, the author (1946c) discussed the use of keratinized animal tissues as substrata for isolating and growing keratinophilic chytrids and described Rhizophydium keratinophilum, a saprophyte which had been isolated on human hair. The present paper concerns another chytrid which appears to be limited in occurrence and growth to tissues containing keratin. This species was isolated first on snake skin from water collected in a wayside ditch near Slharon, Connecticut, and later found to be widely distributed in moist, rich soil. Up to the present timie it has been isolated from soil from Porto Velho and Manaus, Brazil, New York City, Staten Island, and Alden, New York, Bergen County, New Jersey, Woods Hole, MIassachusetts, and New Orleans, Louisiana. So far it has grown vigorously on all keratiinized tissues available, including human and snake skin, hair, feathers, processed wool, and slhavinigs of nails, horns, and hoofs but not on celloplhanie, oniion skin, bits of bleached grass leaves, and otlher similar substrata which contain cellulose. All efforts to grow it on the commonly-used agar media as well as special media containing cystine or hydrolysates of human hair and pig skin have failed, although germination of the zoospores and a slight development of the thalli occurred on 0.5 per cent and 1 per cent agar containing 0.1 per cent lacto peptone, 1 per cent dextrose, and 0.1 per cent yeast extract. These results suggest at least that its nutritional requirements may not be as specialized as those of R. keratinophilum. Because of its thinness and relative transparency, iumiian skin is the best keratinized substratum for microscopic study of this fungus. It grows so prolificallv in this tissue that thousands of thalli in various stages of development are formed within a few davs. Human skin is, furthermore, easier to sectioni than hair or feathers and provides thus a suitable medium for cytological study. The structure and appearance of the m-ature tlialli of this chytrid are strikingly similar to those of Rhizophlyctis with the rhizoids arising from several points on the surface of the inoperculate sporangia. However, it differs from species of this genus by the origin of most of the sporangia intramatrically from the germ tube instead of the zoospore. For this reason it cannot be included in Rhizophlyctis as this genus is interpreted by most chiytridiologists. The author (1946b) originally created a new genus, Perirhiza, for this chytrid and name(I it endogena without giving a diagnosis of the genus and species. Since that time Miss Hanson (1946) has established a new inoperculate Rhizo1 Received for publication July 18, 1946. This work bas been greatly facilitated by a Grant-inAid of Research from the Graduate Faculties of Columbia University. phlyctis-like genus, Phlyctorhiza, whichl develops intramatrically also, but in this genus the sporangia are reported to arise by vesiculation of the dorsal side of the rhizoids. No vesiculations of this tvpe have been observed in our species, and although it is not certain that it belongs in Phlyctorhiza, we are nevertheless assigning our species temporarily to this genus instead of creating a new one for it. Approximately 1.5 per cent of the sporangia observed originated directly from the zoospores as in Rhizophlyctis, which shows that our chytrid lhas some tendency towards this type of development also. Because of its variability in type of development and the marked variation in size and shape exhibited by the sporangia it is named P. variabilis. PHLYCTORHIZA variabilis n. sp.-Fungus saprophyticus; sporangiis hyalinis, laevibus, sphaericis (8-70 /L), ovalibus (6-30 X 8-50 u), oblongatis. fusiformibus (10-15 X 14-45 y), pvriformibus, irregularibus vel angularibus, in 1-3 tubulos exeuntibus; zoosporis ovalibus vel oblongatis (2-2.5 X 3.8-4.5 IL), dense minuteque granulosis, flagello 12-14 / longo; sporis perdurantibus dubiis. Thallus eucarpic, monocentric, rarely polycentric, usually wholly intramatrical. Sporangia variable in size and shape; spherical (8-70 ,u), oval (6-30 X 8-50 ,u), oblong, narrowly or broadly fusiform (10-15 X 14-45 /L), pyriform, obpyriform, irregular, angular, or somewhat stellate, witlh one, rarely two or three exit tubes, 4-10 u wide by 10-90 ,u long. Zoospores oval or oblong (2-2.5 X 3.8-4.5 u) with non-guttulate, finely granular content and a slightly tapering posterior end; flagellum 12-14 fi long. Rhizoids richly branched, usually arising from several points on surface of sporangiumn, main axes up to 8 u in diam. and extending for a distance of 250 /A. Resting spores(?) or thick-walled, dormant sporangia of same size and shape as zoosporangia, hyaline, smooth; functioning directly as zoosporangia in germination. Saprophytic in dead keratinized tissues of animals, Porto Velho and Manaus, Brazil; Connecticut, Massachusetts, New York, New Jersey, and Louisiana, U. S. A. DEVELOPMENTAL CYCLE.-Since P. variabilis may sometimes exhibit two types of development these will be described in considerable detail. The zoospores (fig. 1) are minute, oval to oblong in shape with a slightly tapered posterior end and finely granular content. Thus, as far as size, content, manner of emergence from the sporangium, and behavior while swimming are concerned they are strikingly similar to the zoospores of Rozella species (Karling, 1942a). Shortly before the sporangium dehisces they begin to swarm rapidly within, and as the tip of the exit tube deliquesces a globular mass of spores oozes out (fig. 23). This mass soon disperses, and the zoospores within the spo-