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Figure 1. Coscinodiscus wailesii, living cell. Diameter approximately 250 µm.

Figure 2. C. wailesii valve structure, under light microscope.

Figure 3. C. wailesii, image via oblique SEM . Visible are: girdle bands; two regular rows of rimoportulae (2-3 areolae from margin and at valve face/mantle junction); one irregular row of rimoportulae near center; irregular hyaline central area. Scale bar equals 10 µm.

Species Name: Coscinodiscus wailesii Gran et Angst
Common Name: Diatom
Synonymy: None

    Kingdom Phylum/Division Class: Order: Family: Genus:
    Protista Bacillariophyta Coscinodiscophyceae - - Coscinodiscus

    Use your mouse to rollover the terms in purple for their definitions. If this feature is not supported by your browser, please refer to the accompanying glossary for terminology.

    Species Description

    The cells of Coscinodiscus wailesii are cylindrical or tympaniform, with the pervalvar axis varying from about one half to the whole length of the diameter. In valve view, the cell is circular (Figures 1, 2) and living cells have many small chloroplasts (Figure 1). The transition from valve face to valve mantle is abrupt, forming nearly a 90° angle (Figure 3). The valve center is irregularly hyaline due to a variable termination of the radial rows of areolae, which number 5-6 in 10 µm (Figures 2, 3). At the small end of its size spectrum, the valve structure is significantly altered, and a central rosette replaces the hyaline area (Schmid 1990). The valve mantle is large, usually 30-40 µm in the pervalvar direction, with slightly larger areolae, 4-6 in 10 µm. The cingulum of each theca (Figure 3) consists of a broader valvocopula (approximately 50-60 µm) and a narrower copula (20-25 µm). Occasionally, there are three bands in the cingulum (Schmid & Volcani 1983).

    There are three rings of rimoportulae (labiate processes). One ring is at the base of the mantle, 2-3 areolae in from the margin. Each rimoportula is the terminus of a hyaline line (interstriae). The rimoportulae are about 10-18 µm apart (Figure 3). In this ring are also two larger rimoportulae (macrolabiate processes), separated by an angle of 120-180 degrees. The second ring is at the valve/mantle junction, difficult to see with light microscopy, and individual rimoportulae may be about 5-15 µm apart. The third ring is irregular, and at about one third the radial distance from the center. Each rimoportula is the terminus of an incomplete radial row of areolae.

    The broad mantle with its hyaline lines, coupled with the irregular hyaline area and irregular third rimoportula row, are distinctive features. For further discussion of frustule morphology, see Gran & Angst (1931) and Hasle & Lange (1992).

    The valve diameter in litt. of natural populations is about 160-500 µm. However, cells in cultures have been found as small as 50 µm in diameter (Schmid 1990) and post-auxospore cells as large as 550 µm. In cell volume, this is one of the largest diatoms: for a cell of 500 µm in diameter and a pervalvar axis of 350 µm, the volume is about 6.9 X 107 µm3. However, since most of the volume is vacuole, metabolic activity is mostly confined to areas adjacent to the frustule wall.

    Potentially Misidentified Species

    C. wailesii has been mistakenly identified as Coscinodiscus nobilis.


    Habitat & Regional Occurence

    C. wailesii is a large solitary diatom found in coastal and oceanic waters, primarily in the Pacific and Atlantic Oceans, and missing from boreal polar environments. It has been found throughout the Pacific Ocean since its first description. Apparently an invasive species in the Atlantic Ocean, C. wailesii was first observed in 1977 in the English Channel (Boalch & Harbour 1977), where it was misidentified as Coscinodiscus nobilis, and was seen along the U.S. East coast in the late 1970s.

    It is absent from a 1964-74 survey of diatoms along the U.S. East coast (Marshall 1976). It appeared in Narragansett Bay in 1978 (Hargraves, unpubl.), and was found in the Chesapeake Bay in 1980 (Marshall 1982). The earlier report of the species from Chesapeake Bay (Patten et al. 1963) cannot be confirmed. During the next decade, it spread to the South Atlantic, both eastern (Senn 2002) and western (Fernandes et al. 2001; Lutz et al. 2006) sides. It was not present in the Indian Ocean during the 1964-65 R/V ‘Meteor’ expedition, according to Simonsen (1974). Current status in the Indian Ocean could not be confirmed, but it may have also invaded there. Its ability to survive long periods in darkness (Nagai 1995) suggests that transport in ballast water may have aided in its distribution.

    Indian River Lagoon Distribution

    In the Indian River Lagoon, C. wailesii is found in low numbers (except in summer), particularly where exchange rates with coastal water are more rapid. It has not been seen in the Banana River or Mosquito Lagoon. Because of its size, distinctive morphology and relative ease of cultivation, more information is available for this species than any other species of Coscinodiscus.  Although it is primarily a coastal species, it occasionally is found beyond the continental shelf and in estuaries. When abundant, it apparently produces copious amounts of polysaccharide exudates (‘slime’ or ‘mucilage’) that can interfere with fisheries activities by clogging nets (Boalch & Harbour 1977; Mahoney & Steimle 1980), and is therefore considered a potential Harmful Algal Bloom (HAB) species.



    Details of the sexual cycle (auxospore formation) have not appeared in detail. However, spermatogenesis was examined by Jensen et al. (2003), and the asexual mitotic events were documented by Schmid & Volcani (1983). No morphologically distinct resting spore is known. Nagai (1995) reports resting cells in the sediments of Seto Inland Sea, distinguished by partly plasmolyzed cells that responded quickly to increased illumination. About 70% of resting cells ‘rejuvenated’, and 80% of these divided within 48 hours. Nagai also reports dark survival of at least 15 months. Several reports of an indirect negative effect on ‘Nori’ (Porphyra) aquaculture have been reported, when C. wailesii blooms outcompete Porphyra for nutrients (Nishikawa et al. 2010).

    Cytological events associated with cell wall morphogenesis and the internal organelle structure have been studied by Schmid & Volcani (1983), and subsequently expanded by Schmid (1984, 1988, 1990). As with many planktonic diatoms, the greater portion of the cell volume (as much as 90%) consists of a vacuole - in this case with an interior of extremely acidic pH (Kesseler 1967).


    No known toxicity. Chemical constituents of C. wailesii natural populations have been reported by Ono et al. 2008.


    C. wailesii is subject to parasitic infections by the nanoflagellate Pirsonia diadema, which is at least partly specific to this diatom (Kuehn 1998). Fatal infections by the bacterium Alteromonas sp. are also known (Nagai & Imai 1998). It is likely other pathogens exist.


    No information is available at this time


    No information is available at this time


    No information is available at this time


    Boalch, GT & DS Harbour. 1977. Unusual diatom off the coast of southwest England and its effect on fishing. Nature 269: 687-688.

    Fernandes, LF, Zehnder-Alves, L & JC Bassfeld. 2001. The recently established diatom Coscinodiscus wailesii (Coscinodiscales, Bacillariophyta) in Brazilian waters. I. Remarks on morphology and distribution. Phycol. Res. 49: 89-96.

    Gran, HH & EC Angst. 1931. Plankton diatoms of Puget Sound. Publ. Puget Sound Biol. Sta. 7: 417-529.

    Hasle, GR & CR Lange. 1992. Morphology and distribution of Coscinodiscus species from the Oslofjord, Norway, and the Skagerrak, North Atlantic. Diatom Res. 7: 37-68.

    Jensen, KG, Moestrup. O & A-M Schmid. 2003. Ultrastructure of the male gametes from two centric diatoms, Chaetoceros laciniosus and Coscinodiscus wailesii (Bacillariophyceae). Phycologia 42: 98-105.

    Kesseler, H. 1967. Untersuchungen ueber die chemische Zusammensetzung des Zellsaftes der Diatomee Coscinodiscus wailesii. Helgoland. Wiss. Meer. 16: 262-270.

    Kuehn, SF. 1998. Infection of Coscinodiscus spp. by the parasitoid nanoflagellate Pirsonia diadema: II. Selective infection behaviour for host species and individual host cells. J. Plank. Res. 20: 443-454.

    Lutz, VA, Subramanian, A, Negri, RM, Silva, RI & JI Carreto. 2006. Annual variations in bio-optical properties at the ‘Estación Permanente de Estudios Ambientales (EPEA) coastal station, Argentina. Cont. Shelf Res. 26: 1093-1112.

    Mahoney, JB & FW Steimle. 1980. Possible association of fishing gear clogging with a diatom bloom in the middle Atlantic Bight. Bull. New Jersey Acad. Sci. 25: 18-21.

    Marshall, HG. 1976. Phytoplankton distribution along the eastern coast of the USA. I. Phytoplankton composition. Mar. Biol. 38: 81-89.

    Marshall, HG. 1982. The composition of phytoplankton within the Chesapeake Bay plume and adjacent waters off the Virginia coast, USA. Estuar. Coast. Shelf Sci. 15: 29-43.

    Nagai, S, Hori, Y, Manabe, T & I Imai. 1995. Morphology and rejuvenation of Coscinodiscus wailesii Gran (Bacillariophyceae) resting cells found in bottom sediments of Harima-Nada, Seto Inland Sea, Japan. Nippon Suisan Gakk. 61: 179-185.

    Nagai, S & I Imai. 1998. Killing of a giant diatom Coscinodiscus wailesii by a marine bacterium Alteromonas sp. isolated from the Seto Inland Sea of Japan. 402-405 In: Reguera, B. et al. (Eds.) Harmful Algae. VIII International Conference, Vigo. 1997. Xunta de Galicia and IOC-UNESCO.

    Nishikawa, T, Tarukani, K & T Yamamoto. 2010. Nitrate and phosphate uptake kinetics of the harmful diatom Coscinodiscus wailesii, a causative organism in the bleaching of aquacultured Porphyra thalli. Harmful Algae 9: 563-567.

    Ono, A, Tada, K & K Ichimi. 2008. Chemical composition of Coscinodiscus wailesii and the implication for nutrient ratios in a coastal water, Seto Inland Sea, Japan. Mar. Pollut. Bull. 57: 94-102.

    Patten, BC, Mulford, RA & JE Warinner. 1963. An annual phytoplankton cycle in the lower Chesapeake Bay. Chesapeake Sci. 4: 1-20.

    Schmid, A-M & BE Volcani. 1983. Wall morphogenesis in Coscinodiscus wailesii Gran and Angst. I. Valve morphology and development of its architecture. J. Phycol. 19: 387-402.

    Schmid, A-M. 1984. Valve morphogenesis in diatoms. In: Bach, K & B Burckhardt (Eds), Diatoms 1. Schalen in Natur und Technik. Mitteilungen des Instituts fuer leichte Flachentragwerke 28: 299-317.

    Schmid, A-M. 1988. The special Golgi-ER-mitochondrium unit in the diatom genus Coscinodiscus. Plant Syst. Evol. 158: 211-223.

    Schmid, A-M. 1990. Interclonal variation in the valve structure of Coscinodiscus wailesii Gran et Angst. Beih. Nova Hedwigia 100: 101-119.

    Senn, DG. 2002. Forms of plankton from the Benguela Current off Swakopmund (Namibia). Mitt. Naturforschenden Gesell. Beider Basel 6: 23-28

    Simonsen, R. 1974. The diatom plankton of the Indian Ocean expedition of R/V “Meteor” 1964-1965. “Meteor” Forschungsergebnisse D19: 1-107.

Unless otherwise noted, all images and text by PE Hargraves
Editing and page maintenance by LH Sweat
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Page last updated: 14 June 2011


An unperforated siliceous strip between two striae.


Tube-like openings through the cell wall, each with an internal flattened tube or lip-like slit; also called labiate processes.


Regularly repeated perforations through the cell wall.

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