Some chytrids of Taiwan (IV)

Fung. Sci. 20(3–4): 69–76, 2005
Some chytrids of Taiwan (IV)
Shu-Fen Chen
Department of Health and Nutrition, Chia Nan University of Pharmacy and Science, Tainan 71710, Taiwan
(Accepted: October 17, 2005)
ABSTRACT
The diversity of the Chytridiomycota in Taiwan is not completely known. I baited for these microscopic fungi,
isolated them into pure culture and photographed their development. Herein I document and illustrate three
species of Chytridiales and one species of Spizellomycetales: Catenochytridium hemicysti Knox, Phlyctochytrium reinboldtae Persiel, Rhizophydium sp. and Powellomyces variabilis Powell & Koch ex Longcore, D.J.S.
Barr & N. Désaulniers. The genus Powellomyces and the species described above are new to Taiwan.
Key words: Chytridiales, Spizellomycetales, Powellomyces, Taiwan.
Introduction
The Chytridiomycota (chytrids) are true
fungi that are characterized by producing posteriorly uniflagellate zoospores. Based on differences in zoospore ultrastructure, which have
become ordinal characteristics (Barr, 1980,
1984; Longcore, 1995a), the Chytridiomycota
contains five orders: Chytridiales, Spizellomycetales, Monoblepharidales, Blastocladiales and
Neocallimasticales (Hawksworth et al., 1995);
however, molecular analyses sometimes place
the Blastocladiales outside of the Chytridiomycota (James et al., 2000). Type of development,
thallus morphology and form of rhizoids have
been the important classification criteria for
genera of Chytridiales and Spizellomycetales
(Barr, 1980); however, analyses of 18S rDNA
sequences have shown that these characters do
not always yield monophyletic genera. For example members of the Chytridiales that were
formerly classified in Chytriomyces because of
their thallus development and morphology belong in two different clades (James et al., 2000;
Letcher et al., in press). Regional studies of
chytrids are important not only to document diversity but also to have pure cultures available
that are needed to update the taxonomy of the
Chytridiomycota so that it reflects phylogeny.
About thirty-three species of Chytridiales
and six species of Spizellomycetales have been
reported in Taiwan (Volz et al., 1976; Konno,
1984; Chen and Chien, 1995, 1998; Chen et al.,
2000; Chen, 2002). The following four monocentric chytrids were isolated from fresh water
and soil. They include three species of Chytridiales and one species of Spizellomycetales.
Materials and Methods
Samples of water and soil were baited with
pine pollen (Barr, 1987). Emerson’s 1/4 YpSs
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Fung. Sci. 20(3, 4), 2005
agar (containing 250 ppm penicillin G and 250
ppm streptomycin sulfate) was used to isolate
and culture the organisms. The medium consisted of soluble starch 5 g/L, yeast extract 0.25
g/L, K2HPO4 0.25 g/L, MgSO4·7H2O 0.125 g/L
and agar 12 g/L (or agar 1 g/L as 1/4 YpSs
slush). Developmental stages and morphological characters were examined using the light
microscope. Specimens were identified by consulting with papers or monographs by Sparrow
(1960), and Karling (1977). Axenic cultures
were kept on Emerson’s 1/4 YpSs slush in
screw-cap tubes, and transferred every three
months. All pure cultures are deposited at the
mycological laboratory in Chia Nan University
of Pharmacy and Science and are available for
research purposes.
brown.
Specimen examined. Hwalien: Kwangfu,
Mataian wetland, 7 Jan. 2004, CHNA 6901c.
Isolated on pine pollen from water. Spirodela
sp., Ludwwigia sp., Azolla sp., Nelumbo sp. are
predominant plants at the collection site.
Notes. The exo-endogenous form of thallus
development is similar to the Chytridium type
(Whiffen, 1944). Catenulate segmented rhizoids are a main character of this species. The
flexuous nature of the operculum in C. hemicysti is also an important character. There is no
hyaline area under the operculum and the zoospores drift apart before swimming away.
These are additional important differences with
the remaining three species of the genus Catenochytridium (Barr et al., 1987).
Taxonomy
Phlyctochytrium reinboldtae Persiel, Arch.
Mikrobiol. 32: 411–415, 1959. (Fig. 2, A–C)
On pine pollen: Thallus monocentric, epibiotic, eucarpic. Mature sporangium with 3 to 10
tapering horns, 5 µm in length, these horns are
devoid of protoplasm, they are hyaline. The
sporangial wall is thin and colorless. Rhizoids
arise from a globose apophysis, 6–8 µm in
diam. Zoosporangial discharge was not observed.
Specimen examined. Taiton: Kungshanlingshan, altitude 3,500 m, soil under moss, 18
Jul. 2004, CHNA 7706b. Isolated on pine pollen from soil.
Notes. This species is saprophytic on pine
pollen, but did not grow on 1/4 YpSs. The main
character was the three to ten tapering horns
around the sporangial wall. This distinctive
sporangial appearance is probably sufficient for
identification (Booth, 1969). Phlyctochytrium
Catenochytridium hemicysti Knox, Mycologia
79: 588–591, 1987. (Fig. 1, A–J)
In 1/4 YpSs slush: Thallus monocentric, eucarpic; prosporangium formed in the germ tube
and sporangium epibiotically following discharge of the protoplasm through the zoospore
cyst. Sporangium spherical to subspherical, 31–
49 µm in diam. Discharge pore single, comprising a flexuous operculum, 10–12 µm, that folds
following zoospore release. Zoospores released
as a globose mass and soon drift away before
becoming motile. Zoospores globose, 5–6.5 µm
in diam, with a lateral globule. Rhizoids arise
from 1–3 axes on the sporangium and are sparingly branched and highly strangulate, having a
catenulate appearance. Resting spores spherical, thick, smooth-walled, 15.5–18 µm in diam,
and formed asexually. Color of colony dark
Some chytrids of Taiwan (IV)
71
Fig. 1. Catenochytridium hemicysti. In 1/4 YpSs slush. A. Zoospores. B & C. Thallus development showing the zoospore
cyst (ZC), prosporangium (arrowhead), and rhizoids. D. Prosporangium (arrowhead) at the base of the developing sporangium (S), rhizoids strangulate, having a catenulate appearance. E & F. Mature sporangium with smooth wall. G. The mass
of zoospores escaping from the sporangium. H. The orifice (arrow) after zoospore release. I. The flexuous operculum (arrow). J. Resting spore with thick wall. bars = 10 µm.
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Fung. Sci. 20(3, 4), 2005
reinboldtae was originally observed from halophilic soil by Reinboldt (1951), and subsequently was observed from halophilic soil by
Booth (1969) et al. Now this strain is identified from high mountain soil.
Rhizophydium sp. (Fig. 2, D–I)
On pine pollen: Thallus monocentric, epibiotic, eucarpic. Mature sporangium clavate to
ovate, 20–27 × 22–25.5 µm, borne on an extramatrical stalk, 3–11 µm long; rhizoids
branched and inserted into substrate. Sporangial wall thin, smooth, with 3 to 4 apical or
subapical exit papillae. Zoospores spherical, 2–
4 µm in diam, discharging and swimming away
immediately.
On 1/4 YpSs agar: Sporangium spherical or
subspherical, 30 × 37 µm in diam, rhizoids
branched and tapering. Zoospores numerous,
spherical, discharge may be in mass, escaping
through 3 to 4 exit pores.
Specimen examined. Taipei: Yangmingshan, Chuanszu waterfalls, 2 Aug. 2003, CHNA
2501a. Isolated on pine pollen from water.
Notes.
A predominantly extrametrical,
clavate stalk, discharge through multiple pores,
and a small, spherical zoospore were the main
characters available at the light microscopic
level. The clavate stalk resembles those of
Rhizidium tomiyamanum Konno and Rhizophydium pedicellatum Paterson. The exit papillae
of R. pedicellatum, however is single (Paterson,
1956) whereas this isolate and Rhizidium tomiyamanum (Konno, 1969) have multiple exit papillae. Letcher et al. (2004) studied the phylogeny of Rhizophydium isolates from North
America and Australia and found, based on ultrastructural and large subunit RNA characters,
that has been considered the genus Rhizophydium represents multiple genera. Because current species have been described without pure
cultures, older species accounts are unreliable
and I cannot place this isolate in a species with
confidence. This isolate is saprophytic on pine
pollen, and grows weakly on ¼ YpSs.
Powellomyces variabilis Powell & Koch ex
Longcore, D.J.S. Barr & N. Désaulniers,
Can. J. Bot. 73: 1385–1390, 1995. (Fig. 3,
A–L)
≡ Entophlyctis variabilis Powell & Koch, Can. J. Bot. 55:
1668–1685, 1977.
On pine pollen: Thallus interbiotic or endobiotic, monocentric or somewhat polycentric.
Interbiotic sporangia variable shape, rhizoids
from several sites, with one to three discharge
tubes. Endobiotic sporangia spherical. 20–28
µm in diam, one discharge tube extending out
of substrate.
On 1/4 YpSs agar or slush: Thallus monocentric, eucarpic; sporangium formed endobiotically from the germ tube after protoplasm
moves out of the zoospore cyst. Sporangium
spherical, 75–112.5 µm in diam; number and
length of discharge tubes variable, the tubes up
to 22.5 µm in length. Rhizoids arise from several sites over the sporangium. Zoospores globose, 5–6.5 µm in diam, with a lateral globule.
Color of colony vandyke brown.
Specimen examined. Taiton: Kungshanlingshan, altitude 3500 m, soil under moss, 18
Jul. 2004, CHNA 7702a, 7706a. Isolated on
pine pollen from soil.
Notes. The thallus development is similar to
the Entophlyctis type (Whiffen, 1944). Species
in this genus that were once identified as spe-
Some chytrids of Taiwan (IV)
73
Fig. 2. A–C. Phlyctochytrium reinboldtae. On pine pollen. A. Young sporangium with three horns. B. Sporangium with
five horns. C. The horns devoid of protoplasm (arrow). D–I. Rhizophydium sp. D–H: On pine pollen. I: On 1/4 YpSs agar.
D. Young sporangium borne on an extrametrical stalk (arrowhead). E. Developing sporangium. F. Mature sporangium with
3 to 4 papillae. G. Discharging sporangium. H. Empty sporangium. I. Zoospores discharge in mass (arrow). bars = 10 µm.
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Fung. Sci. 20(3, 4), 2005
Fig. 3. Powellomyces variabilis. A–C: On pine pollen. D–K: On 1/4 YpSs agar. L: In 1/4 YpSs slush. A. Endobiotic sporangium. B & C. Interbiotic sporangium with rhizoids embedded in several pollen grains. D. Zoospores on agar surface. E–
H. Immature thallus showing polarity of rhizoidal development relative to the zoospore cyst (arrows). I. Mature sporangium with discharge tube, a discharge plug (arrowhead) rests at the tip of tube. J. Discharging sporangium. K. Empting
sporangium. L. Sporangium with several discharge tubes and radial arrangement of rhizoids. bars = 10 µm.
Some chytrids of Taiwan (IV)
cies of Entophlyctis (Booth, 1971; Barr, 1971;
Powell, 1977a, 1977b; Longcore, 1995b) are
ubiquitous in soil. On the basis of zoospore ultrastructural characters, some species of this
genus that had broad rhizoids and spizellomycetalean types of zoospore were reclassified to
the Spizellomycetales (Longcore, 1995a). A
study of the molecular genetics of the Chytridiomycota (James et al., 2000) indicates that
Powellomyces species are in a distinct clade
that contains named and un-named isolates.
Based on analyses of 18S rDNA sequences
(unpublished), I identify my isolate as Powellomyces variabilis; the genus is new to Taiwan.
Acknowledgements
The author thanks Mr. Kun-Chan Tsai for
collecting soil samples. This study was financially supported by grant (NSC 93-2621-B041-002) from the National Science Council of
R.O.C.
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臺灣產壺菌 (IV)
陳淑芬
嘉南藥理科技大學保健營養系，臺南縣仁德鄉二仁路一段 60 號，臺灣
摘
要
本 文 描 述 四 種 具 有 後 生 單 鞭 毛 游 孢 子 的 壺 菌 ， 分 別 是 ： 壺 菌 目 Catenochytridium hemicysti 、
Phlyctochytrium reinboldtae、Rhizophydium sp. 及小壺菌目 Powellomyces variabilis，均為臺灣新紀錄
種。
關鍵詞：Powellomyces、小壺菌目、壺菌目、臺灣。