Aug 23, 2003

Quantitative differences in the pineal ultrastructure of perinatal and adult harp (Phoca groenlandica) and hooded seals (Cystophora cristata)

Journal of Pineal Research
J J Aarseth, Karl-Arne Stokkan

Abstract

Seals are unique among mammals in that newborns have a large pineal gland and extremely high plasma levels of melatonin at birth. Melatonin levels are also high in the seal fetus but decline rapidly during the first few days of life. The aim of the present study was to provide quantitative information about the ultrastructure of the seal pineal gland using fetal, newborn, and adult hooded seals (Cystophora cristata), and newborn and adult harp seals (Phoca groenlandica). The relative and absolute volumes of pinealocytes (Pi), arteries and veins, nerves, connective tissue, capillaries and glial cells, as well as mitocondria and lipid droplets in Pi, were calculated by use of point count analysis. Whereas the pineal ultrastructure was similar in fetuses and newborns, both seal species showed a pronounced and particular reduction in the volume of Pi and a similar reduction in pinealocyte mitochondria. There was also a shift from unmyelinated to myelinated pineal nerves in adults compared with fetal/newborns. The selective and marked reduction of Pi may explain the zonated pineal structure typical of the adult seal. The results demonstrate that the fetal gland is as large and active as that of the newborn seal and support the notio...Continue Reading

Mentioned in this Paper

Fetal Structures
Phocidae
Mitochondria
Metazoa
Pineal Gland

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