First report on the maternal transfer of total and intracellular metals and metalloids in the critically endangered spiny butterfly ray (Gymnura altavela)

Increasing risks from metal and metalloid contamination, mainly due to human activities, have become of particular concern for endangered species that already face multiple pressures. These contaminants can bioaccumulate in exposed organisms and induce oxidative stress, cellular damage, reproductive impairments, and embryonic alterations. In viviparous species like the critically endangered Spiny butterfly ray (Gymnura altavela), maternal transfer is a relevant but still underexplored contaminant exposure pathway during early development. This study provides the first evidence of maternal transfer of several elements in G. altavela through integrated maternal and embryo tissue and reproductive fluid analyses. Samples were obtained from artisanal fisheries in Rio de Janeiro, southeastern Brazil, elemental determinations were performed employing inductively coupled plasma mass spectrometry (ICP-MS) and oxidative stress biomarkers were investigated by spectrophotometry. Maternal offloading was verified for most determined elements, with accumulation observed in various embryo tissues. Several metals and metalloids were also observed as capable of traversing the blood-brain barrier, suggesting neurotoxicity potential, as well as accumulating in the rectal gland, possibly resulting in osmoregulation alterations. Higher contaminant levels were noted in the left side of the reproductive system, potentially due to ovarian asymmetry and greater embryonic loads in this side. Reproductive and yolk-associated tissues exhibited higher metal and metalloid concentrations when compared to other batoid species, suggesting high local contamination. These findings highlight maternal transfer as a critical exposure route and suggest that pregnant females and their embryos may be significantly affected in contaminated areas. This supports conservation actions, such as incorporating contaminant monitoring into management plans and prioritizing pollution mitigation in identified G. altavela nursery and fishing grounds.