Figure 1From: Of tests, trochs, shells, and spicules: Development of the basal mollusk Wirenia argentea (Solenogastres) and its bearing on the evolution of trochozoan larval key featuresOocytes, early development, and gonad structure in Wirenia argentea. A, B. Adult specimen bearing eggs in the gonad (arrowheads) and pericardium (pd). A. Scale bar 500 μm; B. Arrow indicating posteriormost part of the gonad containing white sperm, scale bar 250 μm; C. Gonad of W. argentea, histological cross section. Oocytes of different developmental stages with large nuclei (n) containing two dark-staining nucleoli are attached to a median diaphragm (arrows) and surrounded by spermatogonia (sc); bw: body wall, mg: midgut; scale bar 50 μm; D, E. Scanning electron micrographs of an uncleaved embryo (D) and a 32 cell stage (E) covered by the smooth egg hull, scale bars 30 μm; F-H. Light micrographs of 2-cell stage (F), 4-cell stage (G), and 8-cell stage (H), macromeres conventionally marked, the arrow in F points to the egg hull. Note that the CD, D and 1D blastomeres are larger than the other blastomeres; scale bar 40 μm; I. Larva 12 hours after hatching, light micrograph, scale bar 40 μm; J. Schematic drawing of a pericalymma larva depicting apical cap and trunk, stomodaeum (st), protonephridium (pn), as well as the main ciliary bands; at: apical tuft, fc: foot ciliation, ot: oral troch, pro: prototroch, tt: telotroch.Back to article page