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Daniel E. Wujek

Department of Biology

Central Michigan University

Mt. Pleasant, MI 48859


The coccoid green alga Borodinella polytetrasMiller is reported for the first time in North America. Borodinella polytetras was collected from rock scrapings at Gull Lake in Kalamazoo County, Michigan. The species has been previously reported from three sites in Europe, Iceland, and one in Asia.

KEYWORDS: Borodinella, Chlorococcales, Chlorosarcinales, epilithic algae


The nonmotile coccoid green algae belonging to the Division Chlorophyta are diverse, both morphologically and ecologically. They are divided into six classes and ten orders (Shubert and Gärtner 2015), and their environments range from freshwater to marine habitats. At a quick glance, these organisms, commonly called “little green balls,” might all look alike. However, detailed and careful observations reveal stable and distinct morphological characters that separate many of the genera from each other (Prescott 1978; Dillard 2008). Species identification is even more difficult.Although the taxa are non- motile in the vegetative stage, some species produce flagellated or quiescent stages during their life cycle. In some genera, culturing may be necessary, along with electron microscopy (TEM or SEM) or even molecular genetics, to make a final identification, especially at the species level (Lemieux et al. 2014; Štenclová et al. 2017).

Previous investigations by Wujek and co-workers from Michigan have revealed a diverse algal flora in the state and that have resulted in the descriptions of new genera and species and new state and national records (Wujek 1996, 2003, 2006, 2007, 2009, 2012, 2013, 2017a, 2017b, 2018; Wujek and Thompson 2002, 2003, 2008, 2012; Thompson et al. 1996; see Wujek and Igoe 1989 for extensive additional citations). This paper reports the first occurrence of the chlorococcoid green alga Borodinella polytetras Miller (1927) from Michigan and from North America.


FIGURE 1. Borodinella polytetras. Solitary and dividing cells with chloroplasts possessing radiating outgrowths (arrow). Scale = 10 µm.


Samples containing Borodinella polytetras were collected in June 1976 from rock scrapings at the beach in front of Michigan State University’s biological station at Gull Lake in Kalamazoo County, Michigan. Observations were made from freshly collected material in strewn preparations with an A.O. Spencer microscope (bright field only) at time of sampling and a Zeiss Photoscope II light microscope using BF field, phase contrast, and Nomarski interference contrast in the laboratory. A formalin preserved sample has been deposited in the Central Michigan University herbarium (CMC). The three reliable characteristics used by Starr (1955) in identifying green chlorococcalean algae were used in distinguishing Borodinellafrom other fresh-water coccoid forms. In an attempt to place the alga into culture, I returned 15 years later, but I found no evidence of its presence in rock scrapings.


The cells are globose and solitary, although some were observed in tight aggregates during the course of asexual reproduction (Figure 1). The chloroplast is axial, stellate, and often with radial outgrowths (Fig. 1, arrows). The cells from my collections were primarily epilithic, but a few were observed to be neustonic (floating on the surface of the water). I did not observe the tri-, tetra-, or many- celled aggregates observed or reported by some researchers (Korshikov 1953; Fritsch and John 1942; Bourrelly 1966) or any zoospore reproduction, as I did not have the alga in culture.



Borodinella polytetras is cited by Shubert and Gärtner (2015) as one of 76 coccoid genera that are “suspected” to occur in North America, but that “are not commonly encountered in aquatic samples”. Their report, which is a treatment of green coccoid genera, describes and illustrates over 200 genera that occur in North America. My observation of B. polytetrasfrom Gull Lake (Figure 1) represents the first report of this species from North America. It had previously been reported from only five sites, three of them in Europe—Ivanovo Province, Russia, the type location (Miller 1927), Great Britain (Fritsch and John 1942), and Georgia (Barinova et al. 2011)—and one each from Iceland (Broady 1982) and Bangladesh in southern Asia (Aziz and Tanbir 2003; Ahmad et al. 2008). Borodinella polytetras is currently the only species recognized in the genus (Guiry 2017).

There has been some confusion as to the order and family placement of B. polytetras (Table 1). Most of this uncertainty has been in regard to which order of green algae it belonged to: Chlorosarcinales or Chlorococcales. It was not until Groover and Bold (1969) provided a firm basis for distinguishing between the two orders that characters were defined in recognizing two separate orders. The chlorococcacean taxa do not exhibit desmoschsis (vegetative cell division by the formations of common cross walls) and the chlorosarcinacean taxa do. Now that Borodinella’s distinctive cell division is used in separating it from the order Chlorococcales, family Chlorococcaceae into its presently accepted order Chlorosarcinales, the family Borodinellaceae first described by Korshikov (1953). As Borodinella is monotypic, its identification using light microscopy is easily made from its most closed related genus Pseudotrebouxia. Thus its identification from other member of the Chlorosarcinales is made more easily without the necessity of having to culture it for any of the extensive laboratory procedures described above.

Perhaps because my samples were taken in late spring when water temperatures are relatively lower than the higher summer temperatures, environmental conditions had not yet favored the Borodinellacells to develop beyond their uniand di-ad stages. In addition to the cell arrangements I observed, other researchers have observed tri-, quatra-celled, and eventually aggregate colonies,

TABLE 1. Changes in the order and family classification of Borodinella since its original description.

Author Order Family Miller (1927) Protococcales Protococcaceae Fritsch and John (1942) Chlorococcales Chlorococcaceae Korshikov (1953) Vacuolales Borodinellaceae Bourrelly (1966) Chlorococcales Chlorococcaceae Grover and Bold (1969) Chlorosarcinales Chlorosarcinaceae Tschermak-Woess (1982) Chlorosarcinales Chlorosarcinaceae Fott (1983) Chlorosarcinales Chlorosarcinaceae Komarék and Fott (1983) Chlorosarcinales Chlorosarcinaceae Aziz and Tambir (2003) Chlorosarcinales Borodinellaceae This study Chlorosarcinales Borodinellaceae


particularly in cultured material (Miller 1927; Fritsch and John 1942; Aziz and Tanbir 2003).

The following key distinguishes between Borodinella, and similar green coccoid green algae, of which only the last two in the key below have been observed in North America (Guiry 2017). The first two genera in the key, as was Borodinellain this report, are cited by Shubert and Gärtner (2015) as one of 76 coccoid genera that are “suspected” to occur in North America. It possesses an axial chloroplast, frequently lobed or possessing radiating outgrowths. A single pyrenoid is centrally located within the chloroplast. Although I did not observe any zoospores, they are biflagellate with the cell bearing a papilla (Fritsch and John 1942).

Key to the genera in the coccoid green alga family Borodinellaceae

1. Cells coccoid or forming a filamentous thallus in culture .............................BotryokoryneReisigl 1. Cells unicellular to pseudoparenchymatous....................................................................................2 2. Cells spherical to slightly ovoid, cells attached to substrate by posterior colorless parts ....................................................................................................................Chloroplana Hollerbach 2. Cells not as above.......................................................................................................................3 3. Lobes of the chloroplast possessing radiating, sometimes long outgrowths up to the cell wall .............................................................................................................................Borodinella Miller 3. Axial chloroplast on the edge, wavy to irregularly lobed; lobes +/- short, do not reach to cell wall.........................................................................................................PseudotrebouxiaArchibald Hopefully this brief note will alert other Michigan phycologists, limnologists, or individuals conducting environmental studies to examine their samples a little more closely.


I acknowledge the late Dr. R. H. Thompson for his confirmation of the alga’s identification, Philip Oshel of the Imaging Facility at Central Michigan University and Brian Roberts for assistance in the preparation of the figure. Anonymous reviewers, and especially the editor, Dr. M. Huft, are acknowledged for their constructive comments.


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