Spiculosiphon oceana (foraminifera) and its affinity to intermediate stress conditions in the Panarea hydrothermal complex (Mediterranean Sea)

Valentina Esposito,Cinzia De Vittor,Teresa Romeo,Simonepietro Canese,Marzia Bo,Franco Andaloro,Gianfranco Scotti

doi:10.1186/s41200-019-0183-4

Abstract

Spiculosiphon oceana Maldonado, López-Acosta, Sitjà, Aguilar, García & Vacelet, 2013 is a Mediterranean endemic giant stalked foraminifer described as a potential bio-indicator of acidic environments, thanks to its ability to cope with stressful chemical conditions. Here, we present the first record and the first video images of living specimens of this giant foraminifera in the Panarea Volcanic Complex (PVC; southern Tyrrhenian Sea), representing the third discovery worldwide. Specimens of S. oceana were identified through microscopic and remotely operated vehicle (ROV) image analyses, in two different areas characterised by water column physico-chemical parameters typical of the non-vented areas, but with some evidence of hydrothermal alteration. This new finding enhances knowledge on the ecology of S. oceana, enlarges its known spatial distribution, and corroborates its affinity to intermediate stress conditions related to hydrothermal activity.

Highlights

Spiculosiphon oceana Maldonado et al 2013 is a recently discovered endemic species of the Mediterranean Sea and is one of two species of the genus Spiculosiphon Christiansen 1964 recognised worldwide
The distinctive traits among the known species mainly concern the size: S. radiata is 2 cm long, while S. oceana is a giant foraminifer that can reach 3–4 cm in length (Maldonado et al 2013). These foraminifera have a peculiar test standing on a hollow tube, that in S. oceana is characterised by a bulb-like proximal end, not observed in S. radiatus, that penetrates into the substratum but is never anchored permanently to it, and a globe-like capitate region
The analysed specimen of Spiculosiphon oceana was identified and photographed during the microscopic analysis of smooth sediments a few centimeters-thick, consisting of an Fe-encrusted deposit collected by the remotely operated vehicle (ROV) from the top of a hydrothermal diffusive pinnacle-like structure described by Bortoluzzi et al (2017) as a diffusive ferruginous seep (DFS), named DFS2 (Fig. 2)

Summary

Introduction

Spiculosiphon oceana Maldonado et al 2013 is a recently discovered endemic species of the Mediterranean Sea and is one of two species of the genus Spiculosiphon Christiansen 1964 recognised worldwide. The distinctive traits among the known species mainly concern the size: S. radiata is 2 cm long, while S. oceana is a giant foraminifer that can reach 3–4 cm in length (Maldonado et al 2013) These foraminifera have a peculiar test standing on a hollow tube, that in S. oceana is characterised by a bulb-like proximal end, not observed in S. radiatus, that penetrates into the substratum but is never anchored permanently to it, and a globe-like capitate region (the distal end of the tube). The resulting body morphology allows S. oceana to capture small planktonic demersal prey such as crustaceans or calcareous foraminifera (Maldonado et al 2013)

Methods

Results

Discussion

Conclusion