Home / Chrysophyceae / Unicells / Amoeboid / Rhizochrysis
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Name derivation:
Classification:
Rhyzochrysis Pascher 1913; 7 of 13 species descriptions are currently accepted taxonomically (Guiry and Guiry 2014). Order Chromulinales; Family Chrysamoebaceae Probably are derived from flagellated forms (Huber-Pestalozzi 1962). May be synonymous with Chrysamoeba (Hibberd 1971, Starmach 1985).
Morphology:
Golden amoeboid unicells lacking other cell stage types, usually with 1 – 10 contractile vacuoles near the anterior end, and with or without a stigma (eyespot).   Regard by some authors as the amoeboid stage of Chrysamoeba (Ibid). Cell size and seudopod number, shape and size can be used to separate at least seven species. Minute cells are 3 – 5 μm (Rhizochrysis planctonica), larger cells are up to 7.5 μm (R. polymorpha), and still larger cells are 10 – 15 μm in diameter with fine and long pseudopods either branching (R. scherffelii) or not (R. gracillima). Where pseudopods are few or only one, they may be either pointed (R. major) or broadly lobed (R. crassipes). The largest described species has spherical cells 35 – 45 μm diameter and atypical numerous long pseudopods called ‘acicula’ or rhizopodia). May form colonies. More description in Kristiansen and Preisig (2001).
Similar genera:
Population control with biocides:
Biocidal agents successful in limiting the growth of Rhziochrysis are those that are derived from acrylonitrile (Gerharz et al. 2011).
Habitat:
Freshwater; free-swimming or sessile, at least some species neustonic. Rhizochrysis at Lake Erie were highly responsive to nutritional changes in the water, increasing in concentration when there was a decreased phosphorus concentration. (Rattan et al. 2012).
References:
Gerharz, T., König, T., Sauer, F., Uhr, H., and Ulfik, B. (2011). U.S. Patent Application 13/088,718. Guiry, M.D. and G.M. Guiry 2014. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 30 May 2014. Hibberd, D.J. 1971. Observations on the cytology and ultrastructure of Chrysamoeba radians Klebs *(Chrysophyceae). Brithish Phycological Journal 6(2):207-223. Huber-Pestalozzi, G. 1962. Das Phytoplankton des Susswassers (Die Binnengewasser, Band XVI). Teil 2. (i) Chrysophyceen, farblose Flagellaten, Heterokonten E. Schweizerbart’sche Verlagsbuchhandlung. Stuttgart. 365 pp. (Translation to English online). Kristiansen, J. and H.R. Preisig 2001. Encyclopedia of Chrysophyte Genera. Bibliotheca Phycologica 110: 1-260. Pascher, A. 1913. Crysomonadinae (Pascher, A. & E. Lemmermann: Flagellatae II). In: Die Süsswasserflora Deutschlands, Österreichs und der Schweiz.. (Pascher, A. Eds) Vol. 2, pp. 1-95. Jena, Germany: Gustav Fischer Rattan, K., Smith, R. E. H., and Taylor, W. D. (2012). Nutrient status of phytoplankton across a trophic gradient in Lake Erie: evidence from new fluorescence methods. Canadian Journal of Fisheries and Aquatic Sciences 69, 94-111. Doi: 10.1139/f2011-135. Starmach, K.  1985.  Chrysophyceae and Haptophyceae.  In: Ettl, H., J. Gerloff, H. Heynig, and D. Mollenhauer, Eds.  Susswasserflora von Mitteleuropa 5.  Gustav Fischer, Stuttgart:1-515.