Test morphology and organic layer of Discorinopsis aguayoi (Bermudez): relationship with enviromental conditions

A detailed study of the morphology of Discorinopsis aguayoi (Bermúdez) is carried out by analyzing four populations collected in Recent and Neogene brackish environments of Tuscany (Italy). The finding of fossil D. aguayoi is reported in this study for the first time. The modern populations lived in a thermal pool of Montecatini (Pistoia) and in the Lagoon of Orbetello (Grosseto), two brackish environments characterized by different salinities. The fossil specimens were found in Messinian and Pliocene sediments of two quarries near Leghorn and Florence respectively. The present investigation points out the invariant and the echophenotypic characters of D. aguayoi. Modern specimens exhibit morphological abnormalities, correlated to environmental conditions. In the modern populations, the organic layer, well preserved, has also been analyzed. SEM analysis shows “pore plugs” inside conical elevations beneath the pores. TEM investigation, points out the laminar fibrous nature of the organic layer, and microcavities in the organic thickenings and in the “pore plugs” of Montecatini individuals. The microcavities suggest that underlying structural differences between the two populations may be related to extreme conditions of the thermal pool.