Analysis of the morphological structure of diapausing propagules as a potential tool for the identification of rotifer and cladoceran species

Abstract

The study of zooplankton diversity through the analysis of the active community implicates repeated samplings at different sites of the lake, throughout different seasons and years. A valid cost-effective alternative for the analysis of zooplankton species richness is represented by the study of their diapausing propagules. This method allows retrieving in a single sampling the same number of species found in the water column over a period of many years. However, the lack of a reference database of diapausing propagules’ diagnostic characters has, so far, precluded the use of morphology for the identification of egg species. In the present study, an analysis of the morphological characters of rotifer and cladoceran diapausing propagules was performed with Light Microscope (LM) and Scanning Electron Microscope (SEM) to identify possible diagnostic features that would allow identification of their species without having to incubate the sediment first to obtain adults that can be identified. A total of 3780 diapausing eggs of 23 species of rotifers and cladocerans, collected in eleven lakes from five different regions of Spain and Mexico, were morphologically analyzed. High evidence of species-specificity was observed in most rotifer species, while cladoceran diapausing propagules could be only identified to genus level.