Mechanics of venom expulsion in Crotalus, with special reference to the role of the fang sheath

Abstract

A combination of anatomical and experimental preparations were used to explore the function of the venom delivery system in rattlesnakes (Crotalus). The distal end of the venom duct is compressed near the point where it empties into the venom chamber, a space surrounding the fang defined by the fang sheath. Within the venom chamber, the inner fang membrane lies obliquely over the base of the fang at least partially occluding the entrance orifice. When the fang is retracted the combination of the compressed venom duct and the spatial position of the inner fang membrane serve to inhibit or block venom flow. As the fang is erected beyond approximately 60°(relative to the roof of the mouth) localized compression of the fang sheath decreases the size of the venom chamber, relieves the compressive force from the venom duct, and displaces the inner fang membrane away from the entrance orifice of the fang. Pressure recordings taken at different locations along the venom delivery system demonstrate that the venom gland produces suction during relaxation of the extrinsic glandular musculature. These findings suggest that the venom delivery system of Crotalus is both more flexible and more regulated than previously assumed. Anat Rec 264: [415][416][417][418][419][420][421][422][423][424][425][426] 2001.

Sharp and fully loaded: 3D tissue reconstruction reveals how snake fangs stay deadly during fang replacement

“…In contrast to our findings and those of Schaefer (1976), Mead (1702) and more recently Young et al, (2001) proposed the existence of a venom reservoir anterior to the fang of viperid snakes. Mead (1702: 43–44) described the path of the venom in viperids as follows: “ ’Tis a Conglomerated Gland , composed of many smaller ones contained in a common Membrane ; each of These send off an Excretory Vessel , all which do afterwards Unite and Form one Duct , which running towards the Roots of the Fangs , discharges the Yellow Liquor into a Bag .…”

“…palaestinae and E . coloratus ) had no venom reservoir, although it has been previously observed in a viperid species (Mead, 1702; Young et al, 2001). We are aware that the two species examined by us represent a very small part of viperid diversity and, therefore, encourage others to further investigate the presence of a venom reservoir in many other Viperidae species as well as in Atractaspidinae.…”

“…Young and colleagues verified Mead's findings by injecting the distal part of the venom duct of Crotalus atrox (viperid) with blue India ink. They found that venom pooled at the base of the ankylosed fang and confirmed the presence of a tissue chamber (Young et al, 2001).…”

Sharp and fully loaded: 3D tissue reconstruction reveals how snake fangs stay deadly during fang replacement

“…In contrast to our findings and those of Schaefer (1976), Mead (1702) and more recently Young et al, (2001) proposed the existence of a venom reservoir anterior to the fang of viperid snakes. Mead (1702: 43–44) described the path of the venom in viperids as follows: “ ’Tis a Conglomerated Gland , composed of many smaller ones contained in a common Membrane ; each of These send off an Excretory Vessel , all which do afterwards Unite and Form one Duct , which running towards the Roots of the Fangs , discharges the Yellow Liquor into a Bag .…”

“…palaestinae and E . coloratus ) had no venom reservoir, although it has been previously observed in a viperid species (Mead, 1702; Young et al, 2001). We are aware that the two species examined by us represent a very small part of viperid diversity and, therefore, encourage others to further investigate the presence of a venom reservoir in many other Viperidae species as well as in Atractaspidinae.…”

“…Young and colleagues verified Mead's findings by injecting the distal part of the venom duct of Crotalus atrox (viperid) with blue India ink. They found that venom pooled at the base of the ankylosed fang and confirmed the presence of a tissue chamber (Young et al, 2001).…”

The buccal buckle: the functional morphology of venom spitting in cobras

“…The similarity between our findings and the earlier experimental study of the viperid Crotalus (principally Young et al, 2000Young et al, , 2001a suggests functional convergence between these two lineages.…”

Viper Fangs: Functional Limitations of Extreme Teeth

“…Combining the critical flow data from Young and Zahn (2001) with all the other morphological and kinematic data produced by Young and colleagues (Young et al 2000(Young et al , 2001a(Young et al , 2001b(Young et al , 2002Young and Kardong 2007) provides compelling support for the hypothesis that venom expulsion results from the fang sheath sliding upward (unplugging the discharge orifice) combined with entry of the discharge orifice into prey tissues having hydrostatic pressures lower than those in the venom duct and venom canal. The possible dependence of venom injection on sensory feedback may underlie the relatively long duration of the bite phase.…”

Sharp and fully loaded: 3D tissue reconstruction reveals how snake fangs stay deadly during fang replacement

“…In contrast to our findings and those of Schaefer (1976), Mead (1702) and more recently Young et al, (2001) proposed the existence of a venom reservoir anterior to the fang of viperid snakes. Mead (1702: 43–44) described the path of the venom in viperids as follows: “ ’Tis a Conglomerated Gland , composed of many smaller ones contained in a common Membrane ; each of These send off an Excretory Vessel , all which do afterwards Unite and Form one Duct , which running towards the Roots of the Fangs , discharges the Yellow Liquor into a Bag .…”

“…palaestinae and E . coloratus ) had no venom reservoir, although it has been previously observed in a viperid species (Mead, 1702; Young et al, 2001). We are aware that the two species examined by us represent a very small part of viperid diversity and, therefore, encourage others to further investigate the presence of a venom reservoir in many other Viperidae species as well as in Atractaspidinae.…”

“…Young and colleagues verified Mead's findings by injecting the distal part of the venom duct of Crotalus atrox (viperid) with blue India ink. They found that venom pooled at the base of the ankylosed fang and confirmed the presence of a tissue chamber (Young et al, 2001).…”

The buccal buckle: the functional morphology of venom spitting in cobras

“…The similarity between our findings and the earlier experimental study of the viperid Crotalus (principally Young et al, 2000Young et al, , 2001a suggests functional convergence between these two lineages.…”

Viper Fangs: Functional Limitations of Extreme Teeth

“…Combining the critical flow data from Young and Zahn (2001) with all the other morphological and kinematic data produced by Young and colleagues (Young et al 2000(Young et al , 2001a(Young et al , 2001b(Young et al , 2002Young and Kardong 2007) provides compelling support for the hypothesis that venom expulsion results from the fang sheath sliding upward (unplugging the discharge orifice) combined with entry of the discharge orifice into prey tissues having hydrostatic pressures lower than those in the venom duct and venom canal. The possible dependence of venom injection on sensory feedback may underlie the relatively long duration of the bite phase.…”

Sharp and fully loaded: 3D tissue reconstruction reveals how snake fangs stay deadly during fang replacement

“…In contrast to our findings and those of Schaefer (1976), Mead (1702) and more recently Young et al, (2001) proposed the existence of a venom reservoir anterior to the fang of viperid snakes. Mead (1702: 43–44) described the path of the venom in viperids as follows: “ ’Tis a Conglomerated Gland , composed of many smaller ones contained in a common Membrane ; each of These send off an Excretory Vessel , all which do afterwards Unite and Form one Duct , which running towards the Roots of the Fangs , discharges the Yellow Liquor into a Bag .…”

“…palaestinae and E . coloratus ) had no venom reservoir, although it has been previously observed in a viperid species (Mead, 1702; Young et al, 2001). We are aware that the two species examined by us represent a very small part of viperid diversity and, therefore, encourage others to further investigate the presence of a venom reservoir in many other Viperidae species as well as in Atractaspidinae.…”

“…Young and colleagues verified Mead's findings by injecting the distal part of the venom duct of Crotalus atrox (viperid) with blue India ink. They found that venom pooled at the base of the ankylosed fang and confirmed the presence of a tissue chamber (Young et al, 2001).…”

The buccal buckle: the functional morphology of venom spitting in cobras

“…The similarity between our findings and the earlier experimental study of the viperid Crotalus (principally Young et al, 2000Young et al, , 2001a suggests functional convergence between these two lineages.…”

Viper Fangs: Functional Limitations of Extreme Teeth

“…Combining the critical flow data from Young and Zahn (2001) with all the other morphological and kinematic data produced by Young and colleagues (Young et al 2000(Young et al , 2001a(Young et al , 2001b(Young et al , 2002Young and Kardong 2007) provides compelling support for the hypothesis that venom expulsion results from the fang sheath sliding upward (unplugging the discharge orifice) combined with entry of the discharge orifice into prey tissues having hydrostatic pressures lower than those in the venom duct and venom canal. The possible dependence of venom injection on sensory feedback may underlie the relatively long duration of the bite phase.…”