Biology Reference
In-Depth Information
Figure 5: Members of Nostocales.
Anabaena
sp. (A),
Nostoc
sp. (B),
Gloeotrichia
sp. (C),
Scytonema
sp. (D) and
Nodularia
spumigena
(E). Magnifi cation bar represents 5 µm (C), and 10 µm (A, B, D and E). Pictures A to D courtesy G. L. Tiwari,
Department of Botany, University of Allahabad, Allahabad-211002, India. Picture E courtesy Christina Esplund, Linnaeus
University, School of Natural Sciences, Department of Marine Ecology, SE-391 82 Kalmar, Sweden.
Some distinctive features of the classifi cation of Hoffmann
et al
. (2005) are: (i) Coccoid species of
Merismopedia
have been separated on the basis of cell size (small-celled Merismopedias included in
Synechococcales of the fi rst sub-class Synechococcineae and large-celled Merismopedias included
in Chroococcales of the second sub-class Oscillatorineae). (ii) The members of heterocystous,
true-branched members have been separated into three families of Nostocales on the basis of type
of branching. Members with Y-shaped branching have been placed in Symphonemataceae while
those with T-shaped branching pattern are included in Hapalosiphonaceae.
Stigonema
which exhibits
multiseriate branching was placed in Stigonemataceae. However, Komárek (2005) pointed out that
(i) molecular (phylogenetic) data should be accepted as the basic criterion for the classifi cation; (ii)
