Pressure (force/area) with which stylet of nematocyst hits cuticle of prey

Value >=7 GPa
Organism Cnidaria
Reference Nüchter T, Benoit M, Engel U, Ozbek S, Holstein TW. Nanosecond-scale kinetics of nematocyst discharge. Curr Biol. 2006 May 9 16(9):R316-8. p. R317 middle columnPubMed ID16682335
Method Researchers mimicked the receptor potential triggering nematocyst discharge [ref 6 in article] by applying a short-step depolarization and analyzed discharge in >1200 instances with an electronic framing- streak camera (for details see Figure S1 in Supplemental Data). They resolved the ultra-fast phase of discharge by capturing an intermediate stage between the resting capsule and the fully ejected stylet at an exposure time of 200 ns and a framing rate of 1,430,000 fps.
Comments Assuming constant acceleration, researchers calculate that the stylets hit the cuticle with a final velocity (Vmax = a×t) of 18.5–37.1 m/s (BNID 105579). At an average volume (V) of 1,860 µm^3 and a specific density (?) of 1.24×10^6 kg/m3 [ref 7 in article], the stenotele’s mass (m=?×V) is 2.3 ng. Since 40% of this mass gets ejected along with the stylets, the accelerated mass is about 1 ng. This corresponds to an accelerating force (F=m×a) of 13.2–53.1 µN and a kinetic energy (E =1/2×m×Vmax^2) of 0.17–0.7µJ. Due to the extremely narrow tip of stylets (tip radius 15±8nm), the pressure (F/area) at a stylet’s tip can be estimated to be more than 7 GPa, which is in the range of technical bullets. Note-the following calculating 53.1µN/[p×(15nm)^2]=75GPa, a maximum value one order of magnitude greater.
Entered by Uri M
ID 105581