Resumen del producto

Maternal transfer is the process by which the offspring receive non-genetic factors through the mother, such as trace elements. An important factor to consider when maternal transfer is evaluated is the reproductive strategy of the species. Placental and yolk-sac viviparity are among the different kinds of reproductive strategies in elasmobranchs. Placental embryos are nourished, at first, by yolk and later from a direct supply by the umbilical cord. The offspring of yolk-sac elasmobranchs are nourished by yolk during all gestation. The aim of this study is to compare the maternal transfer of total mercury (THg) of the Pacific sharpnose shark Rhizoprionodon longurio (placental species) and the speckled guitarfish ray Pseudobatos glaucostigmus (yolk-sac species). Muscle and liver samples from mothers and their respective embryos were evaluated, as well as yolk of P. glaucostigmus embryos. Analyses were done in a Milestone Direct Mercury Analyzer 80 (DMA-80). R. longurio females had a higher THg concentration (wet weight bases) in muscle (mean = 0.73 µg/g) and liver (mean = 0.14 µg/g) than P. glaucostigmus females (mean muscle = 0.09 µg/g; mean liver = 0.07 µg/g). For R. longurio, embryo THg concentration in muscle increased (from 0.006 to 0.125 µg/g) with embryo total length and with the pregnant female THg muscle concentration. For P. glaucostigmus, 58.8% of muscle (mean = 0.003 µg/g) and 79.4% of liver samples (mean = 0.006), as well as, 100% of the yolk samples did not present detectable levels of mercury. Mercury was transferred from mother to embryos in both species; however, their transfer rate was significantly higher in R. longurio than P. glaucostigmus.

Palabras clave: Pseudobatos glaucostigmus; Rhizoprionodon longurio; Maternal transfer; Mercury

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