Skeletal studies in teleosts have been dedicated to the investigation of osteopathologies in humans and to improve the quality of aquaculture fish production. Recent investigations have highlighted that rearing at low stocking densities in two model fish species, medaka, Oryzias latipes (Di Biagio et al., 2022) and zebrafish, Danio rerio (Martini et al., 2020), as well as the reared marine fish, gilthead seabream, Sparus aurata (Dellacqua et al., 2023) reduces the incidence of some skeletal anomaly types. Medaka seemed to exhibit a reduced magnitude of phenotypical response to augmentation of the density with respect to both zebrafish and gilthead seabream. Noteworthy differences were found between the anomaly types and their localization in the different body regions, highlighting species-specificities. In particular, vertebral centra anomalies (fusions among vertebral centra included) showed a higher response in the hemal, abdominal, and cephalic region in seabream and zebrafish reared at high densities, while medaka show an increased prevalence in the caudal region. Associated vertebral elements responded to density only in the hemal region of zebrafish and in all regions in gilthead seabream, while in medaka only in the modified associated elements of the caudal vertebrae. Gilthead seabream displayed a higher incidence of cephalic vertebral arch anomalies than the other species, while zebrafish showed augmented frequencies of arch anomalies of the abdominal and hemal vertebrae; medaka displayed much lower frequencies of anomalous vertebral arches and rib anomalies in all regions compared to the other species, except for the modified elements in the caudal region. Regarding anomalies of fin rays and pterygophores, density did not play any discernable effect. In general, the caudal fin was the most frequently affected fin, followed by the anal, then dorsal fin, in all three species. Zebrafish displayed the highest frequencies of affected individuals in the caudal fin among the species, while gilthead seabream displayed the highest frequency of individuals affected by anal fin anomalies among the species. Medaka, again, very rarely displayed any fin anomalies.
Detailed anatomical and histological observations carried out on vertebrae fusions revealed further differences among these three species (Fig. 1). All these differences have been analysed under an eco-evo-devo perspective.
This project has received funding from the European Union’s Horizon 2020 Research and Innovation Programme under the Marie Sklodowska-Curie grant agreement No. 766347, BioMedAqu, ETN 766347.