Frame in (E) marks approximately the region magnified in (C). (D, F) Schematics of animals in (C, E) highlighting the main axonal fibers. (C, E) Reconstructions of confocal stacks of acetylated α-tubulin-immunostained animals visualizing the axonal scaffold and ciliary bands. (A) Seven days old (B) 5 weeks old (C–J) 5 days old Platynereis worms. Relative position (A, B), innervation (C–F) and musculature (G–J) of head appendages and anterior segments before (A, C–J) and after metamorphosis (B). 2001 Damen 2002b Hughes and Kaufman 2002b Prud'homme et al. 1998 Telford and Thomas 1998 Telford 2000 Arendt et al. 1996 Rogers and Kaufman 1996 Damen et al. Light gray in (B): developing parapodial appendages Dark gray, mouth opening Yellow, neuroectoderm. An1, first antennal An2, second antennal Ch, cheliceral Ic, intercalary L1, first leg L2, second leg Md, mandibulary Mx, maxillary Pp, pedipalpal perist, peristomium prost., prostomium ps, parasegments pyg, pygidium I–VI, Platynereis larval segments. Segment abbreviations represent extant chelicerate, crustacean and insect segments having evolved from a common ancestral segment. Schematic summary correlating the posterior (orthodenticle/otx) and anterior expression borders of gbx/unplugged, hox1/labial, hox4/deformed and lox5/fushi-tarazu to the position of parasegment and segment boundaries marked by engrailed expression in the neuroectodermal regions of the hypothetical ancestral arthropod (A) and the annelid Platynereis (B). Our data thus support the view that an ancestral ground pattern of segmental identities existed in the trunk of the last common protostome ancestor that was lost or modified in protostomes lacking overt segmentation. This molecular segmental topography matches the segmental pattern of otx, gbx, and Hox gene expression in arthropods. This and the subsequent three chaetigerous larval segments harbor the anterior expression boundary of gbx, hox1, hox4, and lox5 genes, respectively. The first segment is a 'cryptic' segment that lacks chaetae and parapodia. We find that Pdu-otx defines a brain region anterior to the first discernable segmental entity that is delineated by a stripe of engrailed-expressing cells. To elucidate the evolution of segmentation and, ultimately, to align segments across remote phyla, we undertook a refined expression analysis to precisely register the expression of conserved regionalization genes with morphological boundaries and segmental units in the marine annelid Platynereis dumerilii.

Wood air core offers durable off-trail performance with air channels for reduced weight Read MoreSUMMARY Annelids and arthropods, despite their distinct classification as Lophotrochozoa and Ecdysozoa, present a morphologically similar, segmented body plan. Our short size concept increases maneuverability, control, and ease-of-use Partial steel edges stop short of the tip and tail for a balance of edge control and lightweight glide Waxless Positrack base features a positive base structure for the best blend of kick and glide in all snow conditions The ski is compatible with the Turnamic® binding system for unparalleled snow feel.Īctiv Cap offers a balance of torsional rigidity and supple flex from tip to tail for all-conditions stability

The ski's shorter, more accessible length is easy to turn and maneuver in trees and off-trail snow, while a waxless Positrack base offers the best blend of grip and glide in all snow conditions with no prep required.

Wide dimensions and partial metal edges enhance stability and edge control for off-trail snow conditions. The Evo OT 65 bridges the gap between off-trail skiing and backcountry touring.

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