Fig 1.
Light microscopy of Volvox sp. Sagami strains 13-614-Vx13 (A-C), 13-614-Vx15 (D-G) and 14-614-Vx04 (H and I). (A) Asexual spheroid with daughter colonies (d). (B-E) Part of asexual spheroids. (B) Side view of anterior cells, showing elongate-ellipsoidal or spindle cell shape, stigma (s) and pyrenoid (p) in the chloroplast. (C) Top view of somatic cells interconnected by cytoplasmic bridges (b). (D) Optical section of top view of cells surrounded by individual sheaths (asterisks). Stained with methylene blue. (E) Optical section of developing embryo during late stage of inversion. Note that gonidia (g) of the next generation are evident. (F) Monoecious sexual spheroid with eggs (e) and sperm packets (sp). (G) Side view of sperm packet (sp) in monoecious sexual spheroid. (H) Mature zygote with short and acute spines developing on the walls. (I) Sexual spheroid with mature zygotes.
Fig 2.
Maximum likelihood (ML) tree of Volvox sect. Volvox based on ITS region of nuclear ribosomal DNA (ITS-1, 5.8S rDNA, and ITS-2) (S1 Table).
Bootstrap values from ML (left) and maximum parsimony (right) analyses are shown on the branches.
Fig 3.
Maximum likelihood (ML) tree of Volvox sect. Volvox and other colonial Volvocales based on rbcL and psbC genes (S1 Table).
Bootstrap values from ML (left) and maximum parsimony (right) analyses are shown on the branches.
Fig 4.
Swimming velocities in various strains of Volvox sp. Sagami. and V. ferrisii Isaka et al.
Swimming velocities during phototaxis in each culture were measured by tracing 20 individual Volvox spheroids. Two media (AF-6/3 and AF-6) were used for each strain. For statistical tests, see S4 Table.