Diatom collections from several lentic aquatic habitats in northern lower Michigan were found to contain a large benthic centric diatom. Comparison with type material revealed this diatom to be Cyclotella gamma Sov. Specimens ranged in size from 20 to 35 μm and had striae densities of 5 to 8 in 10 μm. Valves are granular externally and possess central and marginal strutted processes internally; as well as a single, well-developed labiate process. The striae are alveolate in nature. Cyclotella gamma is probably more common than records indicate which may in part be attributable to its confusion with C. meneghiniana Kiltz

Lowe, Rex. L.

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The Frustular Morphology and Distribution of Cyclotella gamma Sov. (Bacillariophyceae)

University of Northern Iowa

Proceedings of the Iowa Academy of Science Volume 88 Number Article 10 1981 The Frustular Morphology and Distribution of Cyclotella gamma Sov. (Bacillariophyceae) Rex. L. Lowe Bowling Green State University Let us know how access to this document benefits you Copyright ©1981 Iowa Academy of Science, Inc. Follow this and additional works at: https://scholarworks.uni.edu/pias Recommended Citation Lowe, Rex. L. (1981) "The Frustular Morphology and Distribution of Cyclotella gamma Sov. (Bacillariophyceae)," Proceedings of the Iowa Academy of Science, 88(2), 82-84. Available at: https://scholarworks.uni.edu/pias/vol88/iss2/10 This Research is brought to you for free and open access by the Iowa Academy of Science at UNI ScholarWorks. It has been accepted for inclusion in Proceedings of the Iowa Academy of Science by an authorized editor of UNI ScholarWorks. For more information, please contact scholarworks@uni.edu. Proc. Iowa Acad. Sci. 88(2): 82-84, 1981 The Frustular Morphology and Distribution of Cyclotella gamma Sov. (Bacillariophyceae) REX L. LOWE Department of Biological Sciences, Bowling Green State University, Bowling Green, Ohio 43403 and The University of Michigan Biological Station, Pellston, Michigan 49769 Diatom collections from several lentic aquatic habitats in northern lower Michigan were found to contain a large benthic centric diatom. Comparison with type material revealed this diatom to be Cyclotella gamma Sov. Specimens ranged in size from 20 to 35 µm and had striae densities of S to 8 in 10 µm. Valves are granular externally and possess central and marginal strutted processes internally; as well as a single, well-developed labiate process. The striae are alveolate in nature. Cyclotella gamma is probably more common than records indicate which may in part be attributable to its confusion with C. meneghiniana Kiltz. INDEX DESCRIPTORS: Diatoms, Cyclotella, frustule morphology DEDICATION It is with the greatest respect that I salute the long productive career of John D. Dodd. Because of his love of botany and his unique perception of ''the nature of things," many individuals have become psychological captives of life through the microscope. Thank you, Professor Dodd, for providing the support, stability, and, most of all, the freedom, to develop and exercise curiosity. Cyclotella gamma Sov. was first described in 1963 from samples collected in Lake Killebrew, San Juan County, Washington (Sovereign, 1963). This taxon has not been reported from any diatom surveys since the original description even though the frequency of diatom surveys has increased greatly in the past 15 years. During recent surveys in several lakes in northern lower Michigan, a large benthic species of Cyclotella was encountered. Careful examination revealed this diatom to be C. gamma (although this taxon is probably rather broadly distributed) which is the first report of its occurrence outside the type locality. It is my objective in this paper to discuss the distribu-tion and frustular morphology of C. gamma. MATERIALS AND METHODS In the past six years (1974-79) a wide variety of aquatic habitats in northern Michigan were sampled. Many of these samples were taken in conjunction with teaching duties at the University of Michigan Biologi-cal Station. Collections were primarily benthic and usually epipelic or epilithic. In two instances collections were planktonic. Diatoms were cleaned by the hydrogen peroxide method of Werff ( 1955) and mounted in Hyrax. Samples were scanned and those containing specimens of C. gamma were analyzed to determine the relative abundance of this taxon. This analysis included the enumeration of 500 diatom frustules in a microscope. Samples for scanning electron microscopy were cleaned in a similar manner and strewn on a # 1 coverglass which was later bond~ to an aluminum specimen stub with Tube Coat and coated with 150 A of gold with a glow discharge sputtering divice. Speci-mens were examined and photographed on an Hitachi HHS-2R scan-ning electron microscope. For purposes of comparative morphology, isotype specimens of C. gamma were obtained from the Sovereign collection at the California Academy of Sciences. RESULTS Distribution Of the 27 aquatic habitats examined, C. gamma occurred in the following 7: Douglas and Burt Lakes from episammic communities, Dog, Cochran and Wycamp Lakes from artificial polyeurythane sub-strates, Lancaster Lake from epipelic communities, Long Lake from mixed benthic samples and Lakes Huron and Superior from near-shore plankton tows. In all samples analyzed C. gamma comprised less than 1 % of the total community. These data suggest that this taxon is primarily a benthic form as it rarely appears in the plankton of these lakes. The occurrence of C. gamma in the plankton of Lakes Huron and Superior is possibly a phenomenon of periodic suspension of benthic forms. Florin (1970) illustrated a specimen of what appears to be C. gamma from Kirchner Marsh in southeastern Minnesota which she identified as Cyclotella meneghiniana Kiitz. Morphology Sovereign (1963) in his original diagnosis of this taxon described it as a drumshaped diatom, 18 to 33 µmin diameter with 5-7 striae in 10 µm. Sovereign also characterized C. gamma as having an internal membrane ''like Pinnularia '' which caused the appearance of a small circular band crossing the striae. Specimens from northern lower Michigan range from 20 to 25 µmin diameter, with a striae density of 5-8 in lOµm (figs. 1-2). The internal siliceous membrane covers 1h of each stria centripetally (figs. 1, 2, and 4). Scanning electron microscopy reveals the valve surface to be tangentially undulate with scattered granules in the center (figs. 1, 2, and 3). Scattered among the granules are many small pores that do not penetrate the valve and are probably associated with granules on the opposing valve during frustular development. A similar situation has been observed in C. michiganiana Skv. and C. ocellata Pant. (Lowe, 1975). Striae (intercostae) consist of 2 or 3 rows of pores. An internal view of the valve (fig. 4) reveals I to 3 strutted processes located near the margin of the central area which are also visible with the light microscope (figs. 1 and 2). Marginal strutted processes are positioned near the marginal end of nearly every costa. A single well developed labiate process occurs on one costa. This process protrudes well into the valve and is slightly curved at the end (fig. 5) DISCUSSION Cyclotella gamma is probably widely distributed as a benthic alga of lentic habitats in the northern United States but its similarities to C. Meneghiniana have conceivably contributed to the lack of distribution records. Cyclotella meneghiniana has many characteristics in common with C. gamma including a very similar valve ornamentation and an overlapping of the size ranges. Both taxa have striae composed of 2 or 3 parallel rows of punctae (Lowe, 1975). The central areas of both are ornamented by I to several isolated strutted processes. However, only C. gamma has the small granules dispersed over the valve surface 1Lowe: The Frustular Morphology and Distribution of Cyclotella gamma SovPublished by UNI ScholarWorks, 1981MORPHOLOGY AND DISTRIBUTION OF CYCLOTELLA 83 Fig. I , 2. Light micrographs of C. gamma; bar = JO µm. Fig. 3. Scanning electron micrograph of external valve surface; bar = 5 µm. Fig. 4. Scanning electron micrograph of internal valve surface; bar = 5 µm . Fig. 5. Valve margin and labiate process; bar = 1 µm . 2Proceedings of the Iowa Academy of Science, Vol. 88 [1981], No. 2, Art. 10https://scholarworks.uni.edu/pias/vol88/iss2/1084 PROC. IOWA ACAD. SCI. 88 (1981) which have been a constant feature of northern lower Michigan speci-mens. Internally both taxa have marginal strutted processes on the costae and a single well developed labiated process. Cyclotella meneghiniana does not possess the internal siliceous membrane that covers a large portion of the striae in C. gamma which facilitates taxonomic separation with light microscopy. Cyclotella gamma is morphologically most closely related to species of this genus with alveolate striae (Lowe, 1975). These species include among others C. michiganiana Skv., C. operculata (Ag.) Kutz, C. kutzingiana Thwaites and C. comensis Grun. ACKNOWLEDGMENT I thank Barry Rosen, Patti Lease, and Keith Camburn for photo-graphic and editorial assistance. I thank Margaret Hanna and Albert Mahood for providing type material from the Science Museum of the California Academy of Sciences. REFERENCES FLORIN, M.B. 1970. Late-glacial Diatoms of Kirchner Marsh Southeastern Minnesota. Beih. Nova Hedwigia 31: 667-728. LOWE, R.L. 1975. Comparative ultrastructure of the valves of some Cyclotella species. I. Phycology 2: 415-424. SOVEREIGN, H.E. 1963. New and rare diatoms from Oregon and Washing-ton. Proc. Cal. Acad. Sci. 31: 349-368. WERFF, A. VAN DER 1955. A new method for concentrating and cleaning diatoms and other organisms. Int. Ver. Theor. Angew. Limn. Verb. 12: 276-7. 3Lowe: The Frustular Morphology and Distribution of Cyclotella gamma SovPublished by UNI ScholarWorks, 1981

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The Frustular Morphology and Distribution of Cyclotella gamma Sov. (Bacillariophyceae)

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