Morphological and genetic variation in Southern Ocean Echinoderms with main focus on brittle stars (Ophiuroidea)

In recent years, changes to traditional taxonomic methods to incorporate new technologies and techniques have greatly improved the quality of species hypotheses, but more work can be done to improve the speed of new species discovery and documentation. The mitochondrial COI DNA barcode has been successfully used to identify species with high accuracy since the early 2000s and is now currently used in conjunction with morphological examinations to detect and delimit new species. The first aim of this thesis was the definition of a general standard sampling protocol to be applied in remote and extreme areas such as the Southern Ocean to pinpoint new species and the establishment of a procedural approach for samples treatment to obtain and record all the metadata and information associated with the collected organisms that will undergo molecular identification based on DNA barcoding. Distributional information’s regarding the Ross Sea quadrant are still scarce and sparse, despite the continued research that has been held in the area since the 50’s of the past century. To fill this gap, the second objective of the thesis concerns the production of distributional data and species lists of taxa belonging to the phylum Echinodermata from the Terra Nova Bay area (Ross Sea, Antarctica) for which there is still no information in the scientific literature, i.e. the classes Holothuroidea and Crinoidea. To assess this objective, a “Reverse taxonomy” approach was applied to echinoderms samples stored in the permanent biological collections of the Italian National Antarctic Museum (MNA, Section of Genoa). According to this approach, analysis of morphological features (e.g. skeletal elements) was performed only after having obtained molecular data and a robust phylogeny, to assess the congruence between morphological and molecular data. In order to do that, all the available organisms belonging to the phylum Echinodermata suitable for molecular investigation were gathered and analyzed. A collection of cytochrome c oxidase subunit I (COI) sequences amplified from specimen of the MNA collections was produced and used to define species boundaries. DNA sequences were then deposited in permanent databases (BOLD and GenBank). The application of this technique allowed us to increase the available information for the benthic community of the Terra Nova Nay, as well as to re-evaluate the previous knowledge and to correct gross classification mistakes present in literature due to not appropriate approaches in species determination that led to a perpetration of wrong evaluation of biodiversity in the area for more than 50 years. Due to the diversity of the different classes included in the phylum Echinodermata and the specific analyses necessary to assess the correct identification of each taxon, these will be treated and detailed in separate chapters. The Thesis starts with an Introduction, where the most general topics covered by the entire thesis are presented. Each chapter, with the exception of the first one, which has a different structure from the others, has its own specific “Introduction” to the concepts discussed in that study, followed by the sections “Materials and Methods”, “Results” and “Discussion”. Chapters 1 to 4 have already been published as book chapters (Chap. 1 in Marine Genomics - Methods in Molecular Biology), occurrence dataset (Chap. 2, in the Global Biodiversity Information Facility, https://www.gbif.org/) or regular articles in ISI Journals (Chap. 3 and Chap. 4 in Diversity). Considering the specificity of the different chapters, notwithstanding the fact that they pertain to the same, general topic of research, no general Discussion for the entire thesis was produced. Final remarks are instead reported at the end of the whole thesis (“Thesis Conclusions”).