Morphological and environmental characterization of Terpsinoë musica (Biddulphiaceae, Bacillariophyceae) in tropical streams from Mexico

Abstract

The morphological and environmental characteristics of the genus Terpsinoë were assessed from five populations from tropical streams in central Mexico. Four populations of Terpsinoë musica were characterized by one eccentric rimoportula with a short stalk. Only one population was characterized by one to three eccentric rimoportulae. For the first time the external process known as a rota is described for this genus, a taxonomic character employed to differentiate genera and species in other members of the Biddulphiaceae. Populations of T. musica occurred in warm freshwater habitats (20–29°C), neutral to slightly alkaline waters (pH 7–8), with medium to high ionic content (specific conductance 268–2640 μS cm⁻¹) and dominance of sulphate/bicarbonate and calcium/magnesium. Highest abundances occurred in microhabitats at shallow depths, with variable water flux, low to medium irradiance on the bedrock, suggesting that T. musica is an abundant fresh hard-water species, even though it could be found over a wide range of conditions. The morphological analysis identified all the studied populations as T. musica. However, the morphological and morphometric variation found in these populations suggests ecophenotypic variation, broadening the taxonomic characteristics of this species.

Keywords:

• Biddulphiaceae
• morphology
• ecology
• Mexico
• streams
• Terpsinoë musica

Acknowledgements

We thank Silvia Espinosa Matias for technical support in the SEM, Sergio Castillo (ICMyL-UNAM), Alejandra Aguayo Ríos, Nora Ceniceros and Olivia Cruz (IG-UNAM) for nutrient determination, Miriam Bojorge García for the revision of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.