Lipocalins in Marine Mammals
Benzon Symposium No. 50 - The Lipocalin Protein Superfamily, Copenhagen, Denmark, August 24-28, 2003
The lipocalin beta lactoglobulin has been purified from the milks of a number of marine mammals, and both complete and partial sequences have been obtained. Using a variety of phylogenetic reconstruction methods several evolutionary controversies have been addressed: (1) whether the pinnipedia are monophyletic or diphyletic, (2) the nearest extant terrestrial relative of the pinnipedia, and (3) the relatedness of the walrus (Odobenus rosmarus), and the Odobenidae, to the two other pinniped families, i.e. the Otariidae and the Phocidae. Our results support the monophyly of the Pinnipedia, suggest that the Mustelidae are the closest extant terrestrial relative, and perhaps the ancestor group, of the pinnipedia, and suggest a relationship between the walrus and the Phocidae. Additionally our results indicate a connection between a member of the Sirenia, the Florida manatee (Trichechus manatus latirostris), and the Perissodactyla. These results also support the close affinity of the cetacea to the artiodactyla as determined by studies using other milk proteins.
The analysis is complicated by the fact that the bottlenose dolphin (Tursiops truncatus), and some other terrestrial mammals, posses two forms of the protein, which segregate to different parts of the phylogenetic tree, indicating that gene duplication likely occurred prior to species divergence. The phylogenetic distribution of beta lactoglobulin in the milks of some, but not all, mammals parallels patterns of placentation, and suggests a function of this protein in the transfer of passive immunity from mother to nursing neonate.
The use of milk proteins in phylogenetic analysis is attractive because they can be obtained with minimal trauma to the individual animal, are relatively easy to purify, and can be obtained in quantities sufficient for sequencing.
Keith, Edward O.; Pervaiz, S.; and Brew, K., "Lipocalins in Marine Mammals" (2003). Oceanography Faculty Proceedings, Presentations, Speeches, Lectures. 354.