The embryonic development of the central American wandering spider Cupiennius salei

Abstract

BackgroundThe spider Cupiennius salei (Keyserling 1877) has become an important study organism in evolutionary and developmental biology. However, the available staging system for its embryonic development is difficult to apply to modern studies, with strong bias towards the earliest developmental stages. Furthermore, important embryonic events are poorly understood. We address these problems, providing a new description of the embryonic development of C. salei. The paper also discusses various observations that will improve our understanding of spider development.ResultsConspicuous developmental events were used to define numbered stages 1 to 21. Stages 1 to 9 follow the existing staging system for the spider Achaearanea tepidariorum, and stages 10 to 21 provide a high-resolution description of later development. Live-embryo imaging shows cell movements during the earliest formation of embryonic tissue in C. salei. The imaging procedure also elucidates the encircling border between the cell-dense embryo hemisphere and the hemisphere with much lower cell density (a structure termed 'equator' in earlier studies). This border results from subsurface migration of primordial mesendodermal cells from their invagination site at the blastopore. Furthermore, our detailed successive sequence shows: 1) early differentiation of the precheliceral neuroectoderm; 2) the morphogenetic process of inversion and 3) initial invaginations of the opisthosomal epithelium for the respiratory system.ConclusionsOur improved staging system of development in C. salei development should be of considerable value to future comparative studies of animal development. A dense germ disc is not evident during development in C. salei, but we show that the gastrulation process is similar to that in spider species that do have a dense germ disc. In the opisthosoma, the order of appearance of precursor epithelial invaginations provides evidence for the non-homology of the tracheal and book lung respiratory systems.

Comparative study of spinning field development in two species of araneophagic spiders (Araneae, Mimetidae, Australomimetus)

“…Thus, using the example of a specimen presented extensively in this paper, a 4 th instar that undergoes apolysis, considered as a whole, remains a 4 th instar throughout proecdysis, and the pharate 5 th instar constitutes only a part (albeit the predominant part) of this proecdysial 4 th instar. As proposed by Downes (1987), and adopted by others (e.g., Townley and Tillinghast 2009, Wolff and Hilbrant 2011, Hilbrant et al 2012, Mittmann and Wolff 2012, when an embryo hatches, the postembryo is released, and ecdysis in the postembryo, including the discarding of its exuvium (shed exoskeleton), produces the 1 st instar and marks the start of the 1 st stadium. The molt between the postembryonic stage and 1 st stadium is taken to be the 1 st molt (Downes 1987).…”

Evolutionary crossroads in developmental biology: the spiderParasteatoda tepidariorum

“…Interestingly, a second region of internalising , showing an elongated germ band with extended legs; stage 17, the end of inversion, at which point the embryo has enveloped the yolk; stage 20, the prosoma (Pro) and opisthosoma (Op) become pronounced when the tissue between them (arrowhead) constricts; postembryo, the stage directly after eclosion; 1st instar, the stage that leaves the cocoon; 3rd instar, one of a series of immature free-foraging instars; adult female. Stages 2, 4 and 8 were defined by Akiyama-Oda and Oda (Akiyama- Oda and Oda, 2003) and Yamazaki et al (Yamazaki et al, 2005), Stages 12, 17 and 20 are inferred from corresponding Cupiennius salei stages (Wolff and Hilbrant, 2011). Anterior is to the left in all images.…”

“…During an intricate sequence of tissue movements called inversion (Wallstabe, 1908;Wolff and Hilbrant, 2011), the embryo then envelops the yolk ( Fig. 2A, stage 17).…”

“…Between 65 and ~90 hAEL, during a period of development comparable to Cupiennius stages 9 to 12 (Wolff and Hilbrant, 2011), most segments of the opisthosoma (see Glossary, Box 1) are added sequentially from the posterior segment addition zone (SAZ) (see Glossary, Box 1). Concomitantly, the appendages begin to form and the central nervous system starts to differentiate, as also observed in other spiders (Liu et al, 2009;Wolff and Hilbrant, 2011) (Fig. 2A, stage 12).…”

Migration ofDrosophilaintestinal stem cells across organ boundaries

“…Subsequently, germ layers split into smaller units with even more restricted fates. Gastrulation in insects is a process by which the ventral domain and polar domain of the blastoderm become internalized to form the 'gastral groove' or 'ventral furrow' (Anderson, 1973;Alwes and Scholtz, 2006;Biffis et al, 2009;Wolff and Hilbrant, 2011;Brenneis et al, 2011). Cells of the gastral groove form the mesoderm (in the center) and the endoderm (anterior and posterior tip).…”