S. Fig. 6.

Diagrammatic representation of cleavage and gastrulatory movements in onychophoran embryos of the yolk-free South African species Peripatopsis balfouri, P. moseleyi, P. sedgwicki and P. capensis as well as the yolk-rich Australasian species Peripatoides novaezealandiae, Eoperipatus weldoni and Euperipatoides kanangrensis. (A) Early cleavage is similar in the South African species and E. kanangrensis with cleavage nuclei or blastomeres being generated at the periphery of the egg while cleavage nuclei are initially generated within the yolk mass in P. novaezealandiae and E. weldoni. (B) The first divisions result in a pattern of nuclei at the surface of the egg with a variable orientation with regard to the long axis of the egg in the South African species and E. kanangrensis, there is no report of this phenomenon in P. novaezealandiae and E. weldoni but nuclei gather at one location at the yolk surface. (C) The dividing blastomeres initially cover part (a saddle) of the egg surface in Australasian and South African species. Cells at the peripheral part of the expanding cell mass (blue) are internalized in P. capensis and P. balfouri (yellow circles) and this has been described as precocious gastrulation. (D) The resulting blastoderm (blue) covers yolk granules in the Australasian species and fluid in the South African species P. sedgwicki and P. moseleyi, while a gastrula has formed in P. capensis and P. balfouri. In P. capensis, this gastrula is open to the outside by a blastopore and a cavity, the archaenteron (ar) lined by endoderm (en), is present inside. In P. balfouri, the internalised cells are vacuolated (vc) and later disappear leaving a blastula-like embryo. (E) Gastrulation begins in all species with the formation of a blastopore in the germinal disc (blue). In P. capensis and P. balfouri, a secondary blastopore is opened, from where mesoderm and endoderm (P. balfouri) or only mesoderm (P. capensis) are formed (arrows). In P. capensis, there is no formation of a germinal disc and all endoderm derives from the previously formed endoderm. In the Australasian species, endoderm is formed from the anterior part of the blastopore (arrow heads). The shape and timing of the separation of the anterior part of the blastopore varies among species. In P. capensis, the anterior part of the blastopore is relatively large and has protruding edges (black, thick-lined oval). The anterior part of the blastopore in P. balfouri is separated very early into the stomodeum and the middle part of the blastopore (white ovals). In P. moseley, P. sedgwicki, E. kanangrensis, P. novaezealandiae and E. weldoni, the anterior blastopore remains slit-like (white, vertical bar) for some time after the first phases of segmentation. Panel A–C & E represent surface views except for grey-shaded embryos that show sagittal sections. Panel D shows sagittal (ovals) and cross sections (circles). The blue lining in panel D represent the cellular surface layer, ectoderm or blastoderm. The present investigation concerns E. kanangrensis only while details of early development in the other species have been taken from the literature as cited.