Powered control mechanisms contributing to dynamically stable swimming in porcupine puffers (Teleostei: <Emphasis Type="Italic">Diodon holocanthus</Emphasis>)

Balances of multiple varying forces must be the basis for the unusually great dynamic stability of swimming pufferfishes. We used high-speed digital video recordings to study biomechanics and kinematics of rectilinear swimming at different speeds of five porcupine puffers in a water tunnel. We measured critical swimming speeds (U _crit); fin biomechanics, kinematics, and coordination; recoil movements; and gait changes. Major propulsors were pectoral fins at lower speeds; dorsal, anal, and caudal fins at higher speeds. Precise coordination of fin movements produced small recoil movements at speeds below U _crit. The unusual body shape probably contributes to unconscious stability control.     

13C Kinetic Isotope Effect of the Pudovik Reaction

Abstract

¹³C kinetic isotope effect (KIE) was determined by means of ¹³C NMR for the carbonyl atom in 2-nitrobenzaldehyde in its reaction with 2H-2-oxo-5,5-dimethyl-4-phenyl-1,3,2-dioxaphosphorinane in acetonitrile at 25°C. The observed isotope effect k₁₂/k₁₃ = 1.0238 ± 0.0031 evidences that the formation of the P?C bond in the Pudovik reaction catalyzed by triethylamine is less advanced than the π-bond breakage of the aldehyde carbonyl group.