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VICTORIA LÓPEZ-RODAS Y COLS. AN. R. ACAD. NAC. FARM.

few species. We only found four cosmopolitan mesophile species
of phytoplankters: three Chlorophyceans and one Cyanobacteria
species. They are:

Symploca dubia (Nägeli, 1849) Gomont, 1892. Cyanobacteria,
Oscillatoriales, Phormidiaceae. Fascicles of filaments parallel
oriented to the surface, without branched, and anastomosed. The
filaments are more 1 mm of wide, and without heterocysts (Figure
2a). Cell density this species was of 98 ± 16 filaments ml–1.

Chlamydomonas dinobryonis G. M. Smith, 1920. Chlorophyceae,
Volvocales, Chlamydomonadaceae. The motile cells are pyriforms,
and it presents a small parietal pyrenoid. 5.5 µm in diameter. The
palmoid form presented three-dimensional without branched, and
without spines (Figure 2b). Cell density this species was of 2100 ±
200 cells ml–1.

Scenedesmus obtusus Meyen, 1829. Chlorophyceae, Chlorococ-
cales, Oocystaceae. Cenoby usually in 2-4-cells (rarely 8 or more)
retained within persistent mother cell wall. Cells of the more
common 4-celled colonies laying in the same plane, however, cell
can be displaced in the axis. Cells oval 7.5 µm diameter major and
6.5 µm in diameter minor (Figure 2d). Cell density this species was
of 9.200 ± 700 cells ml–1.

Finally, Chlorophyceae, Chlorococcales, Oocystaceae a species
with cenoby usually in 2-4-cells cells, 4-celled colonies laying in the
same plane, however, cell can be displaced in the axis. Cells almost
spherical (only lightly oval) around 5.5 µm diameter major and
around 5.0 µm in diameter minor (Figure 2c). After consult several
taxonomic expertise, this species seem to be a Scenedesmus, perhaps
a new species (Scenedesmus rapoporti). To confirm this, a molecular
genetic characterization (DNA sequenciation, immunological and
lectin binding patterns) is in process. Cell density this species was of
7.200 ± 300 cells ml–1.

Clonal cultures of these four species were established in
laboratory. The four strains were able to grow in BG-11 medium in
absence of petroleum. The strains were propagated in cultures
exclusively by asexual reproduction. The two species of Scenedesmus
grow rapidly around one doubling every two days. Symploca dubia

890