Internal distributions of a radio-element array in cartilaginous and bony marine fishes: different and heterogeneous

This experimental study determined internal distributions of an array of radio-elements (⁵⁴Mn, ⁶⁰Co, ⁶⁵Zn, ¹³⁴Cs, ²⁴¹Am, ¹⁰⁹Cd, ^110mAg, ⁷⁵Se and ⁵¹Cr) accumulated from seawater by three chondrichthyan fish species (Scyliorhinus canicula (dogfish), Raja undulata (undulate ray) and Torpedo marmorata (spotted torpedo)) and three teleost species (Scophthalmus maximus (turbot), Sparus aurata (seabream) and Dicentrarchus labrax (seabass)). The study tested the hypothesis that the chondrichthyan (cartilaginous) fish taxon and teleost (bony) fish taxon have different patterns of bioaccumulation of these radio-elements in six body components (head, digestive tract, liver, kidneys, skin and muscle), consistent with their long period of evolutionary divergence. Comparisons of body component CFs between the two taxa for each radio-element and the full array of radio-elements showed highly significant differences (p ≤ 0.001) between cartilaginous and bony fishes in each body component, confirming the existence of a strong and pervasive phylogenetic signal; however, the subset of radio-elements most determinant of these differences were unique for each body component. Partitioning between the three individual bony species and the three individual cartilaginous species also occurred repeatedly among their body components, particularly for bony fishes. Distributions of these radio-elements among body components were typically highly heterogeneous for both fish taxa.