The challenge of proving the existence of metazoan life in permanently anoxic deep-sea sediments.
The demonstration of the existence of metazoan life in absence of free oxygen is one of the most fascinating and difficult challenges in biology. Danovaro et al. (2010) discovered three new species of the Phylum Loricifera, living in the anoxic sediments of the L'Atalante, a deep-hypersaline anoxic basin of the Mediterranean Sea. Multiple and independent analyses based on staining, incorporation of radiolabeled substrates, CellTracker Green incorporation experiments and ultra-structure analyses, allowed Danovaro et al. (2010) to conclude that these animals were able to spend their entire life cycle under anoxic conditions. Bernhard et al. (2015) investigated the same basin. Due to technical difficulties in sampling operations, they could not collect samples from the permanently anoxic sediment, and sampled only the redoxcline portion of the L'Atalante basin. They found ten individuals of Loricifera and provided alternative interpretations of the results of Danovaro et al. (2010). Here we analyze these interpretations, and present additional evidence indicating that the Loricifera encountered in the anoxic basin L'Atalante were actually alive at the time of sampling. We also discuss the reliability of different methodologies and approaches in providing evidence of metazoans living in anoxic conditions, paving the way for future investigations.This paper is a response to Bernhard JM, Morrison CR, Pape E, Beaudoin DJ, Todaro MA, Pachiadaki MG, Kormas KAr, Edgcomb VG. 2015. Metazoans of redoxcline sediments in Mediterranean deep-sea hypersaline anoxic basins. BMC Biology 2015 13:105.See research article at http://bmcbiol.biomedcentral.com/articles/10.1186/s12915-015-0213-6.
Department of Life and Environmental Sciences, Polytechnic University of Marche, Via Brecce Bianche, 60131, Ancona, Italy. r.danovaro@univpm.it.|Stazione Zoologica Anton Dohrn, Villa Comunale, 80121, Naples, Italy. r.danovaro@univpm.it.
Roberto
R
Danovaro
Department of Life and Environmental Sciences, Polytechnic University of Marche, Via Brecce Bianche, 60131, Ancona, Italy.
Cristina
C
Gambi
Department of Life and Environmental Sciences, Polytechnic University of Marche, Via Brecce Bianche, 60131, Ancona, Italy.
Antonio
A
Dell'Anno
Department of Life and Environmental Sciences, Polytechnic University of Marche, Via Brecce Bianche, 60131, Ancona, Italy.
Cinzia
C
Corinaldesi
Department of Life and Environmental Sciences, University of Cagliari, Via Fiorelli, 1, Cagliari, Italy.
Antonio
A
Pusceddu
Biozentrum, University of Basel, Klingelbergstrasse 50, CH - 4056, Basel, Switzerland.
Ricardo Cardoso
RC
Neves
Natural History Museum of Denmark, Zoological Museum, Biosystematics Section, Universitetsparken 15, DK-2100, Copenhagen, Denmark.
Reinhardt Møbjerg
RM
Kristensen
D000693:Anaerobiosis; D000818:Animals; D019015:Geologic Sediments; D008522:Mediterranean Sea; D008660:Metabolism; D013045:Species Specificity; D013194:Staining and Labeling