A Contribution to a Better Understanding of the Nitella axillaris Group (Charales, Charophyceae): A Taxonomic Re-Examination of the Nitella translucens Collected in the Province of Ferrara, Italy

The identification of a charophyte population found in a rice field in Ferrara, North Italy, collected in 1999 and initially identified as Nitella translucens, has been reevaluated. Detailed morphological observations here reported have suggested that the specimen displays characteristics more akin to Nitella axillaris, particularly in the structure of its bicellular dactyls and axillary heads. Additional examinations, including scanning electron microscopy (SEM) of oospores and analyses of herbarium specimens—encompassing original materials of N. axillaris, N. axillaris f. tenuoir, and N. translucens f. confervoides—support this reclassification. Notably, the Ferrara specimens exhibit reticulate oospores and specific morphological traits that align well with N. axillaris. However, a syntype of N. axillaris housed at the BM Herbarium presents an anomaly, as it features granulate rather than the expected reticulate oospores. This discrepancy indicates a need for further studies, given that the lectotype of N. axillaris lacks oospores altogether. For now, the charophyte population from Ferrara can be provisionally assigned to N. axillaris “sensu Auctores”. Additionally, it appears to be an alien species introduced into the rice fields of Northern Italy, highlighting the need for further investigation into its taxonomy and distribution.