Page  197 ï~~2006 THE MICHIGAN BOTANIST 197 THE FIRST OCCURRENCE OF THE CHRYSOPHYTE ALGA AMPHIRHIZA EPIZOOTICA FROM NORTH AMERICA Daniel E. Wujek Department of Biology Central Michigan University Mt. Pleasant, MI 48859 INTRODUCTION There are numerous genera of golden-brown algae (Chrysophyta, Chrysophyceae) living in freshwater habitats. Reports of their distribution had been scattered throughout the algal literature for a long time, but only recently have these been summarized for North America (Nicholls & Wujek 2003). This paper reports the occurrence of the chrysophycean alga Amphirhiza epizootica Skuja in Michigan, a species first described from Sweden (Skuja 1948). METHODS AND MATERIALS Phytoplankton samples containing Amphirhiza were collected with a 20 m plankton net from Green's Lake, Beaver Island, Charlevoix County, Michigan, in September 1969, July 1970, and again in August 1977. Observations using a Zeiss Photoscope II were made both from freshly collected material, and from short term cultures grown in soil water extract or Bold's Basal Medium (Bold 1967) with additional soil water extract. Attempts to maintain cultures for extended periods failed; cultures no longer survive. Green's Lake is dystrophic with an average depth of one meter. Approximately 88% of the lake is bordered by a Sphagnum bog. The pH of the lake's water ranges from 5.6-5.9. Water chemistry data include: hardness 5-10 mg/l, phosphates 0.03 mg/l, dissolved oxygen 5.4-10 mg/l, and no detectable nitrates. More detailed data are available in Griffith (1978) and Benjamin (2006). RESULTS AND DISCUSSION Amphirhiza epizootica has not been observed since its original description from Sweden (Skuja 1948). This report is its first for North America. Other authors who have written about this organism mention only Skuja's report without adding any new locations (Bourrelly 1957, 1981; Starmach 1986). Amphirhiza epizootica Skuja was detected growing attached to the rotifer Collotheca sp. in plankton samples taken from Greene's Lake, Beaver Island, Charlevoix County (Figs. 1-3). Skuja's (1948) original description of this alga also illustrated the same genus of rotifer as the substrate. Of the more than 50 sessile Collotheca species, most live in a clear, gelatinous tube; only five are free-swimming and lack the gelatinous tube (Edmondson 1959). Because my samples were collected with a plankton net dragged through aquatic vegetation,

Page  198 ï~~198 THE MICHIGAN BOTANIST Vol. 45 198 THE MICHIGAN BOTANIST Vol. 45 I 1 2 3 FIGURES 1-3. Amphirhiza epizootica. 1. Cells attached to the rotifer Collotheca sp. 2. Recently attached zoospore. 3. Rhizopodial stage of an attached vegetative cell. Scale bars = 3 m it was impossible to determine if my rotifer species was a sessile or planktonic form. If such a tube was present, the alga was attached directly to the rotifer and not on an inconspicuous sheath. The number of rotifers was relatively low. Water temperatures at the times of sampling were between 20-220C. This corresponds with Edmondson's (1944, 1945) observations that sessile species are never present in quantities at temperatures below of 150C, with the largest populations always being found at temperatures above 200C. Like Skuja, I also observed only two plastids, and these were without stigmas or pyrenoids. Cell division was observed only in the evening or night. Each daughter cell received one each of the vegetative cell's original two plastids. A new flagellum and new contractile vacuoles were seen before separation was complete. While it appeared that each new daughter cell received one of the two parental plastids, the formation of new ones was not seen. Indeed Starmach

Page  199 ï~~2006 THE MICHIGAN BOTANIST 199 TABLE 1. Systematic placement of Amphirhiza epizootica Skuja. Author Order Family Skuja (1948) Rhizochrysidales Euchromulinaceae Bourrelly (1981) Chromulinales Chrysamoebaceae Starmach (1986) Chromulinales Chrysamoebaceae (1986) added to the cell's description by noting it contained 2-4 plastids without ever observing a cell. The cells were very sensitive to changes in the environment. If they were not mounted, along with the rotifer, carefully onto clean glassware, they soon disintegrated. Some cells in formalin fixed samples broke free from the rotifer and became distended. Cells remaining attached either burst or also became distended. No stomatocysts were observed. As noted by Skuja (1948), these chrysomonads live attached beneath the oral orifice of the rotifer (Fig. 1). Colonization of the host is via what appear to be uniflagellate zoospores (Fig. 2) or more often simply by vegetative division of the rhizopodially attached cells (Fig. 3). A zoospore's attachment begins at the flagellar end. As soon as this takes place, rhizopodia begin to form (Fig. 2). Recent authorities place Amphirhiza epizootica in the family Chrysamoebaceae (Table 1). It is hoped that by drawing aquatic biologists attention to what until now has been a rarely reported alga, reports of this unusual rhizopodially epizoic alga will become more common. ACKNOWLEDGMENTS I thank the late Dr. R.H. Thompson for drawing my attention to this organism in a sample he had collected from an unknown Kansas site, and for his sketches on which the figures are based. Brian Roberts assisted in the preparation of the illustrations, Scott McNaught identified the rotifer, and Ryan Dziedzic provided translations of the German literature. LITERATURE CITED Benjamin, D.W. 2006. The lakes of Beaver Island. Central Michigan University Biological Station. Unpublished. 12 pp. Bold, H.C. 1967. A Laboratory Manual for Plant Morphology. Harper & Row, New York. 123 pp. Bourrelly P. 1957. Recherches sur les Chrysophyc6es. Revue Algologique, M6moire Hors-S6rie No. 1, 412 pp. Bourrelly P. 1957. 1981. Les algues d'eau douce. Vol. II. Les Algues Jaunes et Brunes, Chrysophyc6es, Phaeophyc6es, Xanthophyc6es et Diatom6es, rev. ed. N. Boub6e et Cie, Paris. 517 pp. Edmondson, W.T. 1944. Ecological studies of sessile Rotatoria. Part I. Factors affecting distribution. Ecological Monographs 14: 31-66. Edmondson, W.T. 1945. Ecological studies of sessile Rotatoria. Part II. Dynamics of populations and social structures. Ecological Monographs 15: 141-172. Edmondson, W.T. 1959. Rotifera. Pp. 420-494. In: Fresh-water Biology, 2nd ed. (ed. W.T. Edmondson). John Wiley & Sons, Inc., NY. Griffith, S.P. 1978. The desmid flora of Green's Lake, Beaver Island, Michigan. M.S. Thesis, Central Michigan University. Nicholls, K.H. & D.E. Wujek. 2003. Chrysophycean Algae. Pp. 471-509. In: Freshwater Algae of North America (eds. J.D. Wehr and R. G. Sheath). Academic Press, NY.

Page  200 ï~~200 THE MICHIGAN BOTANIST Vol. 45 Skuja, H. 1948. Taxonomie des Phytoplanktons einiger Seen in Uppland, Schweden. Symbolae Botanicae Uppsaliensis 9: 1-399. Starmach K. 1986. Chrysophyceae und Haptophyceae. Pp. 1-515. In: Stisswasser von Mitteleuropea (eds. H. Ettl, J. Gerloff, H. Heynig & D. Mollenhauer). Gustav Fischer Verlag, Jena.