Mechanical Design of Fiber-Wound Hydraulic Skeletons: The Stiffening and Straightening of Embryonic Notochords1

Explosive eversion and functional morphology of the duck penis supports sexual conflict in waterfowl genitalia

“…This unusual organization could be related to spiral shape of the waterfowl penis. Hydrostatic cross-helical skeletons usually do not twist or spiral when they extend because when the fibres perfectly oppose one another, they cause the clockwise and anticlockwise torques to balance (Koehl et al 2000;Wolgemuth et al 2005). In the waterfowl penis, when pressurized lymph is forced into the penis, the inner circumferential collagen layer probably restricts the expansion of the lymphatic lumen to a fixed maximum diameter, thereby forcing additional lymph towards the apical portions of the penis.…”

Structure and function of the notochord: an essential organ for chordate development

“…against the sheath, gives the notochord its characteristic rod-like appearance, and provides mechanical properties that are essential for the proper elongation of embryos and for the locomotion of invertebrate chordates and many vertebrate species (Adams et al, 1990;Koehl et al, 2000). This transition, from chordamesoderm to mature notochord, requires a host of loci that have been identified in zebrafish genetic screens Stemple et al, 1996).…”

“…Chondrocytes normally secrete a highly hyrdrated extracellular matrix, which gives cartilage its main structural properties (Knudson and Knudson, 2001). By contrast, while notochord cells produce a thick basement membrane sheath, they retain hydrated materials in large vacuoles (Adams et al, 1990;Coutinho et al, 2004;Koehl et al, 2000;Parsons et al, 2002). These vacuoles allow notochord cells to exert pressure against the sheath walls, which gives the notochord its structural properties (Adams et al, 1990;Koehl et al, 2000).…”

“…By contrast, while notochord cells produce a thick basement membrane sheath, they retain hydrated materials in large vacuoles (Adams et al, 1990;Coutinho et al, 2004;Koehl et al, 2000;Parsons et al, 2002). These vacuoles allow notochord cells to exert pressure against the sheath walls, which gives the notochord its structural properties (Adams et al, 1990;Koehl et al, 2000). There may be a direct relationship between notochord and cartilage in which cartilage has evolved to secrete certain materials; by rerouting those materials to an internal vacuole, notochord cells have co-opted some of the essential structural properties of cartilage to their needs.…”

Notochord vacuoles are lysosome-related organelles that function in axis and spine morphogenesis

“…This axial support is crucial for locomotion in embryos that develop externally, such as fish and amphibians, to evade predation. The pressure exerted from the inflating notochord vacuoles on the constricting perinotochordal basement membrane gives this structure its flexural stiffness and mechanical strength (Koehl et al, 2000). Notochords dissected from Xenopus laevis embryos are osmotically T he notochord plays critical structural and signaling roles during vertebrate development.…”