Gastrulation in the spider Zygiella x‐notata involves three distinct phases of cell internalization

Abstract

The cell movements of gastrulation were analyzed in embryos of the spider Zygiella x-notata, using timelapse video, cell tracing, and improved histology. Cells are internalized near the center of the germ disc in three distinct phases. First, cumulus mesenchyme cells ingress and migrate as a group beneath the superficial layer. Second, mass internalization through a blastopore yields a diffusely organized deep layer. Third, superficial cells accumulate at the center of the germ disc to form the caudal bud. The floor is internalized, and the caudal bud moves over the nascent dorsal field to form the caudal lobe. This pattern of gastrulation differs from the canonical pattern described in the historical literature: (1) the cumulus of Z. x-notata is completely formed before any other cells internalize; and (2) the caudal lobe is formed by means of the caudal bud, which is a locus of cell internalization. Developmental Dynamics 236:3484 -3495, 2007.

Embryonic development and staging of the cobweb spider Parasteatoda tepidariorum C. L. Koch, 1841 (syn.: Achaearanea tepidariorum; Araneomorphae; Theridiidae)

“…They migrate radially along the entire distance from the centre to the edge of the equator (comparable to the rim of the germ disc; Wolff and Hilbrant 2011). Our results support earlier findings (Akiyama- Oda and Oda 2003;Yamazaki et al 2005;Kanayama et al 2010) and correct the view that P. tepidariorum shows a canonical mode of gastrulation (Anderson 1973;Chaw et al 2007). …”

“…In addition to previous studies focusing mainly on behaviour, physiology and neuronal aspects of spiders (i.e. Melchers 1963;Seitz 1966;Weygoldt 1985;Miyashita 1987a, b;Kim and Roland 2000;Barth 2002;Stollewerk 2002;Morewood et al 2003;Hajer and Hrubá 2007;Weihmann et al 2010;Doeffinger et al 2010) and several dealing with chelicerate development (Yoshikura 1955(Yoshikura , 1958Crome 1963Crome , 1964Chaw et al 2007;Weygoldt 1965Weygoldt , 1975Weygoldt , 1979etc. ), chelicerates have become increasingly valued for comparative studies dealing with arthropod relationships and arthropod evolution during recent decades.…”

Velvet worm development links myriapods with chelicerates

“…861405, Sigma-Aldrich; 1 mg ml 21 in PBS) was applied for 15 min. (Sekiguchi 1973;Chaw et al 2007;McGregor et al 2008). Transplantation or removal of the cumulus results in duplication or complete loss of the dorsal embryonic region (Holm 1952), while a gene expression study has revealed that the cumulus functions as an organizer that determines the dorsal region via decapentaplegic signalling (Akiyama-Oda & Oda 2003).…”

The embryonic development of the central American wandering spider Cupiennius salei

“…With multiple cell layers underneath the blastoderm (now ectoderm) this area represents the mesendodermal mass (mesodermal and endodermal cells). In many spider species, the formation and subsequent differentiation of the blastopore takes place at the centre of a structure called a germ disc [31,32]. This is a regional differentiation of blastodermic cells that migrate together, aggregating in the form of a disc.…”