Lampriformes in the Mediterranean Sea: distribution and life-history traits with whole genome sequencing of Zu cristatus (Bonelli, 1819)

The biodiversity of Mediterranean fish has been continuously evolving in the last decades because of non-indigenous species' invasions and the influences of global climate change. The distribution of teleost fishes is of fundamental importance to comprehending how these species contribute to the ecological equilibria of marine areas, especially in a semi-closed basin such as the Mediterranean Sea. Moreover, due to their biological features, several rare fish species are challenging to detect and identify during commercial fishing activities, and both morphological and genetic data on their regard are poor. Molecular approaches have recently provided several new insights into phylogeny classifications and genetics, but a broader database is required to boost these research fields. The fishes of the order Lampriformes are circumglobally distributed and characterized by a peculiar morphology, but the information on this fish group is scarce to absent due to their rarity. Here we report the occurrence in the Ionian Sea of Zu cristatus (Bonelli, 1819), a mesopelagic species from the order Lampriformes considered rare in the Mediterranean basin. The specimen was captured off the coast of Noto (Sicily, Italy) by deep-sea longline fisheries at a depth of 720 m. The sample was transported to the University of Messina laboratories for morphological identification and in-depth morphometric and meristic data analysis. The whole genome sequencing of the species was carried out on Illumina and Nanopore platforms in collaboration with the Nord University of Bodø, Norway. The final draft shows 82% completeness (BUSCO) compared to the actinopterygian genes database. The first complete mitogenome for the species was isolated and annotated on the GenBank database (Acc. PRJNA845808), and an extensive analysis of its features reveals exciting insights. Phylogenetic reconstruction of the order Lampriformes base of the mt-co1 sequences was performed; moreover, the phylogenetics relationships with other related orders were evaluated based on the entire mtDNA structure. An investigation of the opsin- like gene products found in the Z. cristatus genome draft was performed, with a reconstruction of the five sub-families. Identity comparisons and alignment analysis reveal similarities and discordances with some teleost fish species from different orders, mainly related to different habitats. Considering the difficulty of collecting data on this rare taxon, this contribution can help improve the knowledge of this species’ distribution, genetic structure, and features. Further analysis will lead to the complete annotation of the whole genome of the species, a milestone that allows future studies on morpho-physiological and genetic adaptation to the geographical and bathymetrical distributions of this species.