The resistivity, ac susceptibility, ultrasonic sound velocity and attenuation have been measured in the single-phase La0.57Ca0.43MnO3 bulk sample. Sharp attenuation peaks and dramatic stiffening in sound velocities for both longitudinal and transverse waves were observed near the paramagnetic to ferromagnetic phase transition temperature, T-C, implying a strong Jahn-Teller effect. The ultrasonic anomalies near TC are interpreted in terms of a significant reduction of the Jahn-Teller distortion of the Mn3+O6 octahedra, resulting from the coupling of the ferromagnetic spin ordering to the crystal lattice (i.e. spin-lattice coupling) below T-C. The resistivity undergoes a broad insulator-metal transition far below T-C. This phenomenon is related to a sufficiently strong electron-lattice coupling in the ferromagnetic state. (C) 2002 Elsevier Science B.V. All rights reserved.