Potentially Misidentified Species: C. wailesii has been mistakenly identified as Coscinodiscus nobilis.
Habitat & Regional Occurrence: 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.
Reproduction: 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).
Toxicity: No known toxicity. Chemical constituents of C. wailesii natural populations have been reported by Ono et al. 2008.
Parasites: 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.
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.
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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.
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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.
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