Desmids are a diverse group of freshwater green algae that are widespread in aquatic habitats throughout the world. They are characterized by their beautiful and intricate cell walls that are often highly ornamented and symmetrical. These algae are important indicators of water quality and can be used to assess the health of aquatic ecosystems.
Southern India is home to a wide variety of freshwater ecosystems, including rivers, lakes, ponds, and wetlands. These ecosystems are known to harbor a rich diversity of desmids, which play important ecological roles in these habitats. The distribution, diversity, and taxonomy of desmids in southern India have been the subject of several studies in recent years.
One such study was conducted in Tamil Nadu, a state located in the southern part of India. The study aimed to document the diversity of desmids in this region and to supplement this documentation with detailed SEM observations and molecular identifications using the rbcL marker. The study focused on two species of desmids, namely Cosmarium subcostatum Nordstedt and Cosmarium laeve Rabenhorst.
The study found that desmids were widely distributed in the freshwater habitats of Tamil Nadu, including rivers, lakes, and ponds. A total of 35 species of desmids were identified during the study, belonging to 11 genera. The most diverse genera were Cosmarium, Staurastrum, and Closterium, which together accounted for more than 50% of the total species diversity.
The two species that were the focus of the study, C. subcostatum and C. laeve, were found to be relatively common in the freshwater habitats of Tamil Nadu. C. subcostatum was observed to have a distinctive morphology, with a large, central constriction that gave it a unique appearance. C. laeve, on the other hand, was more variable in its morphology, with some individuals exhibiting a smooth cell surface and others exhibiting a finely ornamented surface.
SEM observations of the desmid cell walls revealed intricate and highly varied patterns of ornamentation, including ribs, ridges, spines, and pits. Molecular identification using the rbcL marker confirmed the identity of the two species and revealed their phylogenetic relationships with other desmids from around the world.
Overall, the study demonstrated the rich diversity of desmids in the freshwater habitats of southern India and highlighted the importance of detailed morphological and molecular investigations for accurate species identification. The findings of this study provide a valuable baseline for future studies on the ecology and biogeography of desmids in this region, as well as for efforts to monitor and conserve the biodiversity of freshwater ecosystems in southern India.
