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Fig. 5 | EvoDevo

Fig. 5

From: Gastrulation occurs in multiple phases at two distinct sites in Latrodectus and Cheiracanthium spiders

Fig. 5

Cell morphology at two loci of internalization in Latrodectus species. a Beginning of gastrulation: presumptive cumulus cells internalize through central blastopore (arrowhead). Bottle cell outlined. L. geometricus. b Slightly later stage: most deep cells are cumulus mesenchyme (circled). Cumulus has begun to migrate. A few primitive plate cells have ingressed (green arrowheads). L. geometricus. c Closeup of boxed area in b. d Mid-gastrula: cumulus (circled) has migrated to edge of germ disc. Blastopore is not in plane of section. L. mactans. e. Late gastrula: primitive plate comprises two to three layers of deep cells. Internalization continues at central blastopore (arrowhead). Two bottle cells outlined. L. mactans. f Mitotic spindles are oriented such that daughter cells typically remain in the same cell layer (black arrowheads), although some cell divisions are vertical (white arrowhead). L. mactans. g Section through rim of germ disc late in gastrulation showing a chained array of large, round cells (yellow arrowheads). Green arrowheads indicate some mesenchymal cells in the deep layer. L. mactans. Scale bars 50 µm

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