Genomic and Phenotypic Analyses of Polychaete Sibling Species <i>Platynereis dumerilii</i> and <i>Platynereis massiliensis</i> in Relation to Ocean Acidification

The increase of anthropogenic carbon dioxide emissions and the subsequent uptake of CO₂ by the sea, is leading to a decrease in the pH of the oceans, a process known as Ocean Acidification. One of the main challenges of the current research on climate change is to determine how marine species respond to low pH/elevated <i>p</i>CO₂ conditions. <br></br><br></br> This thesis has investigated the effects of natural OA on the polychaete species <i>Platynereis dumerilii</i> and its sibling <i>P. massiliensis</i> (Annelida, Nereididae) as driver of genetic differentiation and phenotype/genotype selection. <i>Platynereis</i> spp. populations were sampled in five geographical areas situated along a thermo-latitudinal gradient along the Italian coasts, characterized by different pH conditions (acid <i>vs</i> normal). A multidisciplinary approach, focused on different aspects of the target species biology, was chosen and the following analyses were performed: (a) morphological and morphometric analyses of different populations/genotypes; (b) laboratory rearing of different populations to study the reproductive biology and gamete morphology; (c) population genetics by the amplification of a mitochondrial DNA marker (COI); (d) population genomics by a next-generation sequencing approach (RAD-seq); (e) background analyses and a long term laboratory experiment on selected genotypes/populations to study physiological responses to different pH conditions. <br></br><br></br> This work has confirmed that <i>Platynereis dumerilii</i> and <i>P. massiliensis</i> represent two complexes of sibling species characterized by contrasting life history traits, reproductive biology and gamete morphology. The overall <i>Platynereis massiliensis</i> predominance in the CO₂ vent systems is not a direct consequence of elevated <i>p</i>CO₂, but it seems to derive from a winning reproductive strategy (brooding habit) in low pH conditions. Unlike <i>Platynereis dumerilii, P. massiliensis</i> is potentially able to thrive in the CO₂ vents thanks to the higher stability of its antioxidant defence systems over temporal scale and its greater responsiveness to extreme hypercapnia conditions.

Name dc:type.qualificationname

phd

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

The Open University

Year dc:date.issued

2018

Author dc:creator

• Valvassori, Giulia

Language dc:language

en