Two domestic guinea-pigs (Cavia porcellus), bought in Pinheiros, São Paulo State, Brazil, were taken by their owners a farm in the rural district of Capão Bonito, close to the Atlantic Forest, São Paulo, where they both developed tumour-like and ulcerating lesions on the ears. The causative agent was identified as Leishmania (L.) enriettii, based on biological characters and isoenzyme profiles. Sources of the parasite in wild mammals, and the possible sandfly vector species discussed.

The kinematics of each joint of the guinea pig Cavia porcellus were studied during the locomotor cycle at increasing speed by high-speed cinefluorography. The main objective was to reveal the functional specific features of these structural elements in each dynamic phase of the cycle and also which limb joints are important during the increase of animal speed. Most of the analysed angles in C. porcellus were affected as the speed increased, both in trot and gallop. However, only a few of them were correlated with speed. There were also differences with respect to symmetrical or asymmetrical gaits. Both pairs of limbs responded differently to the increase of speed; while the forelimb joints modified the duration of their action (frequency) more than the amplitude (stride length), the hindlimbs acted inversely. The movements of the joints during the stance phase changed dramatically with speed, particularly in the hindlimb. At knee level, the flexion amplitude increases to maintain the stiffness of the leg spring, a principle previously discussed as essential for the running process. In the swing phase, inertial effects are the main constraints and, as in the stance phase, the knee joint in the swing phase is correlated with speed both during trot and gallop, confirming the major importance of this joint to increasing speed.

Caviomorph rodents stand out by showing long gestation periods and by producing few, extremely precocial young. This study compares the energy cost of gestation vs lactation in the guinea pig Cavia porcellus. It tests whether the long gestation period (68 days) relative to the total period of maternal care (88 days) of this species results in a high overall energetic efficiency of reproduction. Although maternal net production during gestation was as high as during lactation, the net energy cost of gestation was much lower than the energy cost of lactation. Mothers' average increase in energy intake (above the non-reproductive level) was only 16% during gestation, but 92% during lactation. Similarly, the peak in maternal energy intake was low during gestation (2.4 times basal metabolic rate) compared to the peak during lactation (3.7 times basal metabolic rate). Consequently, the efficiency of energy conversion into offspring tissue during gestation (62%) was almost twice as high as the efficiency during lactation (35%). The results agree with the hypothesis that a prolonged gestation period increases the overall energetic efficiency of reproduction.