Home / Greens / Colonial / Flagellated / Pleodorina
Click on images for larger format
Name derivation:
“Sail gift” -- Sail Pleo- gift –dorina
Classification:
Pleodorina W.R.Shaw 1894; 6 of 8 species descriptions are currently accepted taxonomically (Guiry and Guiry 2013). Order Chlamydomonadales; Family Volvocaceae
Morphology:
Mostly spherical colonies formed from individual spherical cells radially located in the periphery of their gelatinous matrix. Each individual cell has two equal flagella, a stigma, and many contractile vacuoles while most others have only two. The colonies contain mostly reproductive cells with a small group of somatic cells at the anterior end. The colonies are asymmetric with a gradient in cell size from one pole to the other. Smaller cells remain flagellated for the life of the colony, while some of the larger cells lose their flagella, enlarge further into reproductive ‘gonidia’, then reproduce either sexually of asexually. Separation of growth from cell division is called ‘palintomy’, and is found with other volvicine genera starting with Chlamydomonas (Leliaert et al. 2012). Origin of asymmetry in colonial chlorophyceae is open to speculation. One intriguing possibility is that light is concentrated by cells facing the sun by acting as lenses, and projecting the concentrated light on cells on the more shaded side of the colony. The downwelling horizontal beams of the sun are converted to converging beams, and these arguably cause as differentiation in cell growth (Kessler et al. 2015). However, given the random revolving movement of the colonies, it seems likely that all cells are equally influenced by the lens effect.
Similar genera:
Habitat:
Freshwater, more common in reicher waters
References:
Guiry, M.D. and G.M. Guiry 2013. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 10 September 2013. Kessler, J.O., A.M. Nedelcu, C.A. Solari and D.E. Shelton 2015. Cells acting as lenses: A possible role for light in the evolution of morphological asymmetry in multicellular volvocine algae. In: Ruiz-Trillo and Nedelcu, Eds.0 Evolutionary Transitions to Multicellular Life:225 – 243. Springer. online Leliaert, F., D.R. Smith, Herve Moreau et al.  2015.  Phylogeny and molecular evolution of the green algae Critical Reviews in Plant Sciences 31:1-46.  online Shaw, W.R 1894. Pleodorina, a new genus of the Volvocineae. Botanical Gazette 19: 279-283, pl. XXVII.