Introduction Vernix caseosa has long been thought to be a uniquely human substance, not demonstrated in any other species. Monomethyl branched chain fatty acids (BCFA) synthesized by the sebaceous glands are at uniquely high concentration in vernix and serves as a marker for skin lipids. Amniotic fluid-borne vernix particles appearing in the last third of human gestation are swallowed by the fetus and deliver BCFA throughout the GI tract where they appear in meconium at birth. We found physical vernix on the skin of newborn California sea lions born in captivity, and collected amniotic fluid, gastric contents, serum, and meconium.
Our aim was to determine whether California sea lions have physical vernix resembling humansthat can serve as a vehicle for BCFA delivery to the fetal gut.
Methods. Skin surface debris present at delivery(vernix), amniotic fluid, serum, gastric contents, and meconium were collected from five California sea lions at birth and analyzed for BCFA structure and profile.
Results. California sea lions have a white waxy vernix-like material on their skin. Amniotic fluid, vernix, gastric contents, serum, and meconium had 18%, 5%, 3.6%, 1.2%, and 12% by w/w BCFA. BCFA chain lengths were from C15 to C24. iso-BCFA dominated with iso-20:0, iso-22:0, and iso-18:0 as the highest in most samples. anteiso-BCFA totaled about 0.5%. Total meconium BCFA of 12% is more similar to the human level of about 17% than to other dog and piglet meconium BCFA which were <1%. The serum BCFA suggests that some is absorbed.
Conclusion. California sea lions are born with a vernix like material with much lower BCFA concentration than humans (29%), however meconium BCFA are similar to humans suggesting that vernix delivers BCFA to the fetal gut in a manner similar to humans.