Data from: Morphology and performance of the trap-jaw cheliceral strikes in spiders (Araneae, Mecysmaucheniidae)

Mecysmaucheniidae spiders have evolved ultra-fast cheliceral strikes four
times independently. The mechanism for producing these high-speed strikes
is likely due to a latch/spring system that allows for stored energy to be
rapidly released. This study examines two different sister-lineages:
Zearchaea has ultra-fast cheliceral strikes and Aotearoa, based on
external morphology, is hypothesized to have slower strikes. Using
high-speed videography, I gather kinematic data on each taxon and test the
hypothesis that external morphology predicts cheliceral strike
performance. Then, using histology and data from
&[mu]-Computed-Technology scanning I ask whether internal muscle
morphologies also correspond to performance differences. Results from
high-speed video analysis reveal that Zearchaea sp. achieves peak angular
velocities of 25.0 &[plusmn] 4.8 x 103 rad s-1 (mean
&[plusmn] standard deviation) in durations of 0.0843
&[plusmn] 0.017 ms. The fastest recorded strike had a peak angular
and linear velocity of 30.8 x 103 rad s-1 and 18.2 m s-1, respectively.
The slower striking sister-species, Aotearoa magna, was three orders of
magnitude slower in velocity and longer in duration. Histology revealed
sarcomere length differences, with some muscles specialized to be slow and
forceful, and others to be fast and non-forceful. 3D printed models reveal
structural differences that explain how the chelicerae hinge open and
closed. Combining all of this evidence I put forth a hypothesis for the
ultra-fast trap-jaw mechanism. This research documents the morphological
shifts that accompany ultra-fast movements and result in increased
rotation in joints and increased muscle specialization.