The earliest fishes arose circa 500 million years ago (mya) during the Ordovician and persevered throughout several mass extinction events. Unknown fishes' lines became extinct in life history (e.g., conodonts, ostracoderms, acanthodians, placoderms, etc.). It is so that extant lineages may be speculated to have been successful due to several hypotheses: i) an internal milieu composition that provided a buffering medium, protecting them from acute and threatening changes (e.g., ion compositions, temperatures, pH, etc.) and supporting life and giving time for adaption; ii) an high evolving plasticity, thus, generating heritable phenotypes and diversifying species across a wide range of habitats (resilience); and/or iii) the influence of stochastic processes on genetics fate. Most of this Ph.D. Thesis aims to provide new insights into the ion regulatory mechanisms in different fishes' intestines to compare them. Specifically, we focus on crucial ion transporter proteins such as Na+/K+-ATPase (NKA), H+-ATPase (VHA), Na+:K+:2Clˉ cotransporter (NKCC), Na+:Clˉ (NCC). Moreover, we provide new insights on the molecular and physiological mechanisms in the most basal ion- and osmo- regulator, the sea lamprey (Petromyzon marinus), and in a much recent diverged teleost, the Senegalese sole (Solea Senegalensis). Additionally, aquafeeds' effects contaminated with aflatoxin B1 on growth performance and intestinal physiology are also examined, using gilthead seabream (Sparus aurata), a well-known farmed biological model. |
