Most species of the viviparous teleost family Goodeidae exhibit an unusual placental relationship. Embryos lay free within the single, hollow ovary where they are bathed by the ovarian fluid. Nutrients are absorbed from the fluid through distinctive perianal processes called trophotaeniae. Trophotaeniae represent the embryonic component of the placenta and may be functionally divided into protein endocytosing and nonendocytosing types. The maternal component of the placenta is the internal ovarian epithelium (IOE). Since embryos undergo dry weight increases ranging from 68-to 387-fold compared to the dry weight of mature ova, there must be substantial nutrient transfer from the maternal organism during gestation. Transmission electron microscopy of the IOE of gravid females of three goodeid species fails to reveal evidence of significant synthetic activity by the IOE, although occasional budding of parts of IOE cells occur, and the IOE of one species, G. atripinnis, contains substantial amounts of lipid. Electrophoretic comparison of nongravid females of two species establishes that the protein pattern of the ovarian fluid is similar to that of the female blood serum. In gravid females whose embryos bear proteinendocytosing trophotaeniae, protein is undetectable in the ovarian fluid during mid-and late gestation, suggesting efficient protein absorption by the trophotaeniae. In gravid females whose embryos bear nonendocytosing trophotaeniae, serum proteins are present in the ovarian fluid at midgestation, but are reduced to only a trace at late gestation suggesting possible imbibition by the embryos. o 1995 Wiley-Liss, Inc. ReceivedAuast 30, 1994; revision accepted November 14,1994. Address reprint requests to Frank Hollenberg, Department of Biocomposed of an outer epithelium surrounding a logical Sciences, Clemson University, Clemson, sc 29634-1903. 0 1995 WILEY-LISS, INC.

Embryos of most species within the viviparous teleost family Goodeidae develop characteristics perianal processes that are considered to be derivatives of the embryonic hindgut. These processes, termed trophotaeniae, are covered with an epithelium that is continuous with the absorptive epithelium lining the hindgut. Gestation is intraovarian, and trophotaeniae mediate the uptake of maternally provided nutrients into the embryo from the ovarian fluid. Ultrastructural examination of the trophotaeniae of four goodeid species reveals substantial diversity in the organization of the epithelium within the family. The trophotaeniae of Alloophorus robustus, Zoogoneticus quitzeoensis, and Ilyodon furcidens have morphological features associated with the endocytosis of macromolecules and can be shown to endocytose the exogenous protein tracer horseradish peroxidase (HRP) rapidly. The trophotaenial epithelia of these species differ from one another with respect to other morphological features such as cell height, organization of the brush border, and the complexity of the intercellular spaces. The trophotaeniae of Goodea atripinnis lack an endocytotic apparatus and do not endocytose HRP. However, the overall organization of G. atripinnis trophotaenial cells suggests a function as a transporting epithelium. The cells have a dense brush border, numerous mitochondria, and many mitochondria that are enveloped by lamellar sheets of intracellular membrane. Post-fixation with osmium and potassium ferrocyanide reveals a marked difference in the complexity of the subepithelial connective tissue. Alloophorus robustus and Z. quitzeoensis exhibit an extremely electron-dense ground substance containing many acellular components. Goodea atripinnis exhibits an electron-lucid ground substance with few acellular components. © 1994 Wiley-Liss, Inc.