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Instituto de Botánica Spegazzini, 53 No. 477, (1900) La Plata, Buenos Aires, Argentina
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIAL AND METHODSTAXONOMYDISCUSSIONLITERATURE CITED |
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Brevilegnia ensenadensis sp. nov. is described from litter (floating twigs, leaves, and roots) in a man-made, polluted channel near a petroleum refinery, in Buenos Aires Province, Argentina. The species is illustrated and compared with other species of the genus; it can be identified by the preponderance of smooth or papillate oogonia, with a distinctive irregular inner wall, borne in bent or coiled oogonial stalks, which are terminal, lateral or of the intercalary position. The oogonia often are irregular in shape, and the oospheres mostly are immature. The single oospore is eccentric inside the great oogonia, and the species develops mainly diclinous antheridial branches and has fewer monoclinous and androgynous ones.
Key words: Oomycota, Straminipiles, systematics
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIAL AND METHODSTAXONOMYDISCUSSIONLITERATURE CITED |
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), and 13 species were recognized in the genus (Dick 1973, 2001), but at present only 10 species are accepted (Johnson et al 2002). The genus is characterized by depauperate mycelia, monosporous oogonia and brevilegnoid spore release. Some species demonstrate achlyoid- or dictyucoid-type spore-discharge patterns, in addition to the brevilegnoid type, so they have been reasigned to the genus Achlya Nees or Dictyuchus Leitg, proposed by some authors (Chiou and Chang 1976, Langsam 1987). For this reason, only 10 species currently are recognized as belonging to this genus (Johnson, Seymour and Padgett 2002). All the species and varieties of this genus have been isolated mainly from soil; only one unidentified species has been isolated from the mud of an eel-culture pond in Japan (Hoshina et al 1960).
During a survey of zoosporic organisms in hydrocarbons polluted water and organic matter in streams and channels, near the YPF-Repsol Petroleum refinery, Partido de Ensenada, Buenos Aires Province (Argentina), the author found a species belonging to the genus Brevilegnia, with distinctive features separating it from other species in the genus. It is named here B. ensenadensis Steciow (Saprolegniales, Straminipila). Previous contributions about zoosporic organisms isolated from this habitat also have been made (Steciow et al 2001a, b, Steciow 2002a, b).
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MATERIAL AND METHODS |
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, Johnson (1956) and Sparrow (1960) were used. Samples of brown, decaying twigs, leaves and wood of the local dominant vegetation were collected from a man-made channel and taken to the laboratory in separate sterile polythylene bags. The channel is located at Partido de Ensenada, Buenos Aires Province, Argentina. It receives the effluents of the refinery, and of COPETRO, a coke-producing company. Aliphatic (15.390 µg/L) and aromatic (3.327 µg/L) hydrocarbons were found in the water samples, estimated by gas chromatography. The samples were placed and distributed in water culture in sterilized Petri dishes containing several halves of hemp seeds (Cannabis sativa) and were incubated at room temperature (15–20 C). After growth of the fungus on the seeds, a single hypha, or spore, was isolated and transferred to cornmeal-agar medium to obtain axenic culture. After 3–4 d, a block of agar from the edge of each colony was cut off and placed in sterilized Petri dishes containing distilled water. Hemp seed halves were added to obtain sister colonies. After the colony had grown out and reproductive structures formed, measurements and observations were made with an Olympus BX 40 microscope (Olympus Optical Co. Ltd., Tokyo, Japan) equipped with phase-contrast optics.
Some colonies were incubated at 5, 15 and 25 C to observe the possible effect of temperature on the variations of sexual structures. Diameters of fungus colonies, oogonia and oospores, and size of zoosporangia were calculated from 50 counts of each of three replicates. Means were compared using Tukey's multiple-range tests. The total percentage of type of antheridial branches was calculated from all these replicates. The type specimen of Brevilegnia ensenadensis is deposited in the mycological herbarium of Spegazzini Institute (LPS 45799); its culture collection is No. 743.
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TAXONOMY |
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TOPABSTRACTINTRODUCTIONMATERIAL AND METHODSTAXONOMYDISCUSSIONLITERATURE CITED |
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[Mycelium densum, cultura in seminibus Cannabis sativae L. circa 1–2.5 cm diam. Hyphae ramosa, pleraque 30–77 µm late ad basim. Sporangia copiosa in culturis juvenilibus, fusiformia, filiformia, cylindrica, vel clavata, (218–) 237–490 (–613) µm longa et 20–76 µm lata. Ejecto sporarum pro genus typica, zoospori incystatis globosi 5–10 (–15) µm. Gemmae frequentis. Oogonia copiosa, sphaerica, subglobosa et pyriformia, 29–67 (–92) µm diam. Paries oogonia foveatus, laevis vel papillatus, ramulus lateralibus, terminalibus vel intercalaribus provenientia, 12–291 (853) µm. Oospori 1 per oogonium, excentrici, 26–39 µm diam. Ramulus antheridialis, ramosus, 78% ± 11 diclina, 13% ± 5 monoclina et 9% ± 7 androgina.]
Mycelium extensive, denser near substratum, 2-wk-old hemp seed colony, 1–2.5 cm diam; principal hyphae stout, sparingly branched, 30–77 µm diam at the base. Gemmae abundant, cylindrical, pyriform or irregular, single or often catenulate, functioning as zoosporangia. Zoosporangia fusiform, filiform, cylindrical or claviform; straight or sinusoid and curved at the tips; (218–) 237–490 (–613) x 20–76 µm; usually terminal, renewed usually by distinctive sympodial or cymose branching. Zoospore discharge brevilegnoid, sometimes dictyucoid in primary ones, in young cultures, usually with two or three rows of spores. Encysted spores more or less angular, rarely cylindrical mostly 5–10 (–15) µm diam. Oogonia very abundant, lateral or terminal, frequently intercalary; spherical or subspherical, sometimes obovate, pyriform, oval or irregular in shape, apiculate or naviculate, 29–67 µm diam; when dolioform or cylindrical in intercalary ones, reaching 71–92 µm diam. Oogonial wall smooth or with ornamentation, papillate; unpitted or pitted only under attachment point of antheridial cell; inner wall surface irregular, slender. Oogonial stalks straight or frequently bent, curved and coiled once or many times; 12–291 (–853) µm long, sometimes branched. Oospheres infrequently maturing. Oospore eccentric, single, filling or not the oogonium; spherical or ellipsoid; 26–39 µm diam. Antheridia always present. Antheridial branches slender, principally diclinous (78% ± 11), occasionally monoclinous (13% ± 5), rarely androgynous (9% ± 7), branched, often wrapping the oogonia. Antheridial cells simple or branched; attached by projections, apically or laterally appressed. Fertilization tube not observed.
HOLOTYPE. ARGENTINA. BUENOS AIRES: Ensenada, polluted, man-made channel, on floating litter; 3 Apr 01, leg. M. Steciow, LPS No. 45799; culture collection No. 743.
Etymology. The name refers to the locale (Ensenada) where this new species was found.
The shape and size of oogonia, type of oospore and of antheridial branches are constant features in B. ensenadensis. The type and size of zoosporangia, exposed to different temperatures, did not vary much; they are fusiform, filiform, cylindrical or claviform and reach a length of 218–613 µm. Oogonia are constant in shape, mainly spherical or subspherical, sometimes obovate, apiculate or naviculate, rarely pyriform, often irregular and ornamentated, mainly papillate. Measurements of colonies, oogonia diameters, oospores diameters, length of oogonial stalks and size of zosporangia were taken under three different temperature regimes (Table I). The initial growth rate in B. ensenadensis was faster at higher temperatures, under which it formed larger colonies with a greater number of zoosporangia, but after 25 days the mean colony diameters differed little under the three regimes (Table I).
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At all temperatures, gemmae became more abundant as the cultures aged.
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DISCUSSION |
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, Johnson 1950).
Furthermore, these features also are known to vary from isolate to isolate in a species (Johnson et al 1973, Johnson 1974, 1977). In contrast, characteristics such as the type of antheridia, general morphology of the oogonia, the size of oospores and the manner of sporangial proliferation are regarded as relatively stable (Johnson 1950, Inaba and Tokumasu 2002).
Brevilegnia ensenadensis Steciow has strong affinities to B. irregularis Rossy-Valderrama. This species was recognized by Khulbe (2001) and Dick (2001) and reduced to synonymy of B. unisperma (Coker and Braxton) Coker by Johnson et al (2002). Both species have oogonia, with the wall thin and the outer surface smooth or occasionally sparsely papillate and the inner wall surface usually irregular. They also develop lateral and irregular hyphal swellings, suggestive of deformed or abortive oogonia; the antheridial branches usually are diclinous, infrequently monoclinous and rarely androgynous in B. ensenadensis, and they are monoclinous or androgynous in B. unisperma, when present. However, B. ensenadensis has an unpitted or pitted oogonial wall under the attachment point of the antheridial cell, on lateral or characteristic intercalary oogonia, which are larger 29–67 (–92) µm, and the oogonia stalk are bent, curved or coiled, whereas in B. unisperma the oogonial wall always is unpitted, the oogonia are (14–) 18–24 (–45) µm diam and the oogonial stalk is straight, occasionally curved or bent, frequently branched (Rossy-Valderrama 1956, Johnson et al 2002).
The zoosporangia are longer (218–)237–490(–613) µm and the oospores are slightly larger 26–39 µm in B. ensenadensis, whereas in B. unisperma the zoosporangia are 31–408 µm and the oospores are smaller (12–)14–17(–23) µm (Johnson et al 2002).
Brevilegnia linearis Coker & Braxton also has a bent or coiled oogonial stalk, but it has mainly androgynous antheridial branches, rarely diclinous or monoclinous, often absent on some oogonia, and it has characteristic zoospores arranged in a single row inside the terminal or intercalary zoosporangia (Coker and Braxton 1926).
B. indica Phrabhuji & Sinha., an illegitimated species from India (Dick 2001), is similar to this new Argentine species, in having smooth or rarely papillate oogonia, which are spherical or angular, often in intercalary position, or on a stout, bent or once-coiled oogonial stalk, but it is different in that it has smaller oogonia (18–30 µm diam), oospores and zoosporangia (90–270 x 20–50 µm); gemmae are absent and the antheridial branches are mainly monoclinous, and it also has diclinous as well as androgynous ones (Phrabhuji and Sinha 1993, Khulbe 2001).
The great oogonia size of B. ensenadensis resembles that of B. megasperma JV Harv. This latter species is easily distinguished from the other species by relatively large oogonia and oospores, and the production of gemmae. B. megasperma includes two varieties, var. brevicaulis Rossy-Vald. and var. megasperma J.V. Harv. (Harvey 1930, Rossy-Valderrama 1956). The former could be distinguished from the latter by relatively short and stout oogonial stalks, smaller oogonia and oospores, and by commonly producing intercalary oogonia.
Furthermore, according to Rossy-Valderrama (1956), two varieties would differ in appearance of the antheridial branches and those of the variety brevicaulis are almost monoclinous, whereas the variety megasperma produces only androgynous and hypogynous ones. In Brevilegnia megasperma var. megasperma intercalary oogonia seldom occur, whereas in the variety brevicaulis they are common. However, Johnson et al (2002) consider that both varieties overall are not distinctive enough from the species to be retained.
Antheridial branch origin in B. ensenadensis is similar to that of B. longicaulis Johnson, particularly in the preponderance of diclinous branches (Johnson 1950). In the former, however, monoclinous and androgynous branches are produced, which does not occur in B. longicaulis. Diclinous antheridial branches are sparingly produced by B. diclina J.V. Harv. (Harvey 1927); the Argentine species consistently produces abundant antheridial branches.
Tabulate comparisons of the main morphological characters among this new Argentine species and all those species recognized by Johnson et al (2002) are made in Table II.
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ACKNOWLEDGMENTS |
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FOOTNOTES |
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Accepted for publication February 8, 2003.
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LITERATURE CITED |
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Coker WC., 1923 The Saprolegniaceae with notes on other water molds. Chapel Hill, North Carolina: University of North Carolina Press. p 201
Coker WC., 1927 Other water molds from the soil. J Elisha Mitchell Sci Soc 42:207-226
Coker WC., Braxton HH., 1926 New water molds from the soil. J Elisha Mitchell Sci Soc 42:139-149
Dick MW., 1973 Saprolegniales. In: Ainsworth GC, Sparrow FK, Sussman AS, eds. The fungi, an advanced treatise. Vol IV B. New York,United States: Academic Press. p 113–144
Dick MW., 2001 Straminipilous fungi. Dordrecht,. The Netherlands: Kluwer Academic Publishers. 670 p
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Hoshina T, Sano T, Sunayama M., 1960 Studies on the saprolegniasis of eel. J Tokyo Univ Fish 47:59-79
Inaba S, Tokumasu S., 2002 The genus Brevilegnia (Saprolegniales, Oomycetes) in Japan. Mycoscience 43:59-66
Indoh H., 1941 Observations on some aquatic molds collected from Micronesia (preliminary note). Hakubutsugaku-Zasshi Tokyo (Mag Nat Hist) 38:86-91
Johnson TWJr., 1950 A study of an isolate of Brevilegnia from New Caledonia. Mycologia 42:242-252
Johnson TWJr., 1956 The genus Achlya: morphology and taxonomy. Ann Arbor, Michigan: Univ. Michigan Press. 180 p
Johnson TWJr., Howard KL, Padgett DE., 1973 Aquatic fungi of Iceland: Brevilegnia Coker and Couch. Acta Bot Islandica 2:7-24
Johnson TWJr., 1974 Aquatic fungi of Iceland: Brevilegnia bispora Couch, and some related forms. Acta Bot Islandica 3:3-20
Johnson TWJr., 1977 Aquatic fungi of Scandinavia: species of Brevilegnia. Mycologia 69:287-298
Johnson TWJr., Seymour RL, Padgett DE., 2002 Biology and systematics of the Saprolegniaceae. Online publication: http://www.ilumina-dlib.org. 1028 p
Khulbe RD., 2001 A manual of aquatic fungi (Chytridiomycetes & Oomycetes). Delhi, India: Daya Publishing House. 255 p
Langsam DM., 1987 Notes on the genus Brevilegnia: two excluded taxa. Mycologia 79:323-324
Prabhuji SK, Sinha SK., 1993 Two new water molds from India: Allomyces recurvus sp. nov. and Brevilegnia indica sp. nov. Neo Botanica 1:31-38
Rossy-Valderrama C., Some water molds from Puerto Rico. J Elisha Mitchell Sci Soc 72:129-137
Salvin SB., 1942 Variations of species and varietal character induced in an isolate of Brevilegnia. Mycologia 34:38-51
Sparrow FKJr., 1960 Aquatic phycomycetes. 2nd ed. Ann Arbor, Michigan: University of Michigan Press. 1187 p
Steciow MM, Elíades LA, Arambarri AM., 2001a Nuevas citas de Blastocladiales (Chytridiomycota) en ambientes contaminados de Ensenada (Buenos Aires, Argentina). Darwiniana 39:15-21
Steciow MM, Elíades LA, Arambarri AM., 2001b El género Gonapodya (Monoblepharidales, Chytridiomycota) en ambientes contaminados de Ensenada (Buenos Aires, Argentina). Bol Soc Argent Bot 36:203-208
Steciow MM, 2002a A. robusta sp. nov., a new species of Achlya (Saprolegniales, Straminipila) from a polluted Argentine channel. Microbiol Res 157:177-182[Medline]
Steciow MM, 2002b A new species of Saprolegnia (Saprolegniales, Straminipila), from a polluted Argentine channel. New Zealand Journal of Botany (In press)
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