CD15 in trophotaeniae of the viviparous goodeid fish Xenotoca eiseni (Cyprinodontiformes, Teleostei).

The antigen CD15, also known as 3-fucosyl-N-acetyl-lactosamine (FAL), or Stage Specific Embryonic Antigen (SSEA-1) is a cell membrane and cytoplasmic antigen, that is present in several mammalian tissues. Using immunohistochemistry the monoclonal antibodies 3B9 and B4,3 detected CD15 in whole mount preparations of trophotaeniae of embryos of the matotroph viviparous teleost Xenotoca eiseni. A specific localization is encountered in the ecto- and entodermal portion of the trophotaenial epithelium. A positive reaction in the fibrocytes of the inner mesenchymal core of trophotaeniae is doubtful since a relative high background is present in these cells. CD15 positivity has been observed in all developmental stages studied. The exact role of CD15 is unclear. An involvement in endocytic activity is postulated.