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Name derivation:
leptos (Gr.) – thin; cylindrus – cylinder. Thin cylinder.
Classification:
Leptocylindrus Cleve 1889; 5 of 6 species descriptions are currently accepted taxonomically (Guiry and Guiry 2013). Order Leptocylindrales; Family Leptocylindraceae
Morphology:
The cells are cylindrical and can be either in chains or single cells. The chains are connected at the flattened valve faces. The central part of the valves can be either convex or concave. There are short flap-like or triangular shaped spines between the valve face and the mantle. They appear to have half bands around the chain that have a trapezoidal outline. Chains can have various epiphytes. Can have resting spores within a sphere that looks like a auxosphore that is different than the other vegetative cells.
Similar genera:
Corethron generally has longer barbed spines or short hook-like spines. Can easily be mistaken for an unbranched green trichome at first observation.
Sexual and asexual life cycles
Of 71 clones isolated from Narragansett Bay Rhode Island USA, only two had a sexual stage that produced an auxospore. All the rest produced auxospores asexually (French III and Hargraves 1986). the auxospores can excyst (germinate) forming large vegetative cells in as little as three days (French 1982). Germination of auxospores has an action spectrum similar to that of its chloroplast, with peaks at 44 nm and 680 nm (Shikata et al. 2011).
Dark respiration sensitivity to preconditioning light intensity
L. danicus dark respiration increases cell photosynthate loss when cells were pre-exposed to higher light intensity, seven fold from 5 to 20 C, equivalent to a Q10 of 4.0. (Verity 1982a). Most likely this response is proportional to the cellular photosynthate available for respiration, as seen also in light-dark experiments with colonies of Nostoc pruniforme (Arvidson and Baker, unpublished data).
Growth sensitivity to temperature and light:
Lepocylindrus danicus had a higher cellular chlorophyll a. carbon and nitrogen content when grown at 15-20 C than at 5-10 C, and at higher light intensity. Cellular mass ratios of carbon to nitrogen were 4.4 – 6.7 (Verity 1981), slightly lower than the Redfield Ratio atomic ratio prediction of 107:16 or mass ratio of 124:17 = 7.94. Growth in batch cultures was also proportional to temperature from 5 – 20 C, while no growth occurred at 2 and 25 C (Verity 1982b).
Formation of resting spores during nitrogen deficiency:
Spores heavily armed with spines were produced and sank when nitrate levels were < 0.5 μm within a mesocosm with a 10 m diameter and 30 m depth (2356 m3) at Sanich Inlet, British Columbia Canada (Davis et al. 1980). .
Symbiotic relationship:
L. mediterraneus frequently has the epiphytic protist Solenicola setigera attached to the region of its girdle. the nonphotosynthetic epiphyte probably is attracted to exudates from the host cell. In turn the photosynthetic picoplanktonic cyanobacterium Synechococcus forms a coat on Solenicola setigera, presumably benefitting from the attachment that should reduce its loss to predators, and apparently being ingested occasionally by Solenicola (Buck and Bentham 1998). In the equatorial and southern Pacific ocean S. setigera often covers the entire frustules of L. mediterraneus (Gomez 2007).
Habitat:
Marine species are found from the Antarctic to the Arctic. They are seldom dominant, except for in the Norwegian fjords in the summer
References:
Buck, K.R., and W.N. Bentham 1998. A novel symbiosis between a cyanobacterium, Synechococcus sp., an aplastidic protist, Solenicola setigera, and a diatom, Leptocylindrus mediterraneus, in the open ocean. Marine Biology 132:349-355. Davis, C.O., J.T. Hollibaugh, D.L.R. Seibert, W.H. Thomas and P.J. Harrison 1980. Formation of resting spores by Leptocylindrus danicus (Bacillariophyceae) in a controlled experimental ecosystem. Journal of Phycology 16:296-302. French III, F.W. 1982. Investigations on marine diatom resting spores. Ph.D. Dissertation, University of Rhode Island (218 pp). French III, F.W., and P.E. Hargraves 1986. Population dynamics of the spore-foprming diatom Leptocylindrus danicus in Narragansett Bay, rhode Island. Journal of Phycology 22:411-420. Gomez, F. 2007. the consortium of the protozoan Solenicola setigera and the diatom Leptocylindrus mediterraneus in the Pacific Ocean. Acta Protozoologica 46:15-24. Guiry. M.D. and G.M. Guiry 2013. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 21 Dec 2013. Heimdal, B R.1983. Phytoplankton and nutrients in the waters north-west of Spitsbergen in the autumn of 1979. Journal of Plankton Research 5:6 pp.901-918. Hasle, G. et al. Identifying Marine Phytoplankton. Academic Press. (1997). Shikata, T., M. Iseki, S. Matsunaga, S. Higashi, Y. Kamel and M. Watanabe 2011. Blue and red light-induced germination of resting spores in the red-tide diatom Leptocylindrus danicus. Photochemistry and Photobiology 87:590-597. Verity, P.G. 1981. Effects of temperature, irradiance, and daylength on the marine diatom Leptocylindrus danicus Cleve. I. Photosynthesis and cellular composition. Journal of Experimental Marine Biological Ecology 55:79-91. 1982a. Effects of temperature, irradiance, and daylength on the marine diatom Leptocylindrus danicus Cleve. III. Dark Respiration. Journal of Experimental Marine Biological Ecology 60:197-207. 1982b. Effects of temperature, irradiance, and daylength on the marine diatom Leptocylindrus danicus Cleve. IV. Growth. Journal of Experimental Marine Biological Ecology 60:209-222.