Behavioral and ecological consequences of sex-based differences in gustatory anatomy in Cebus apella.

Fungiform papillae (FPs) are the only gustatory structures on the anterior tongue. Taste buds (TBs), which are located in FPs, house taste receptors. Each TB has a taste pore (TP) by which tastants are transmitted. In humans, FP and TB densities correlate with taste sensitivity and food preferences. Females have higher FP densities than males in Homo, Pan, and Cebus. Homo, Pan, and Cebus also have larger brains, slower ontogenetic development, and higher maternal investment in offspring compared to most primates. An increase in maternal investment places intense pressure on females to 1) obtain high-quality foods, and 2) detect potential toxins at low levels. This study examines sex differences in FPs and TPs (a TB surrogate) in 11 Cebus apella to test the hypothesis that higher FP density in females may be an adaptation specific to reproductive strategies of females. Tongues were imaged using an environmental scanning electron microscope; from these images FP surface area, FP density, TP count, and TP densities were calculated. We found that there were no significant differences between males and females in the number of TPs per FP. However, we did find that females do have larger FP surface areas and higher FP densities than males. The anatomical evidence indicates that females may have greater taste sensitivity than males because females have more FP than males. Future research on food preference and selection in Cebus is expected to show sex-specific behaviors similar to those observed in Homo and Pan.

Microanatomy of the mandibular symphysis in lizards: patterns in fiber orientation and Meckel's cartilage and their significance in cranial evolution.

Although the mandibular symphysis is a functionally and evolutionarily important feature of the vertebrate skull, little is known about the soft-tissue morphology of the joint in squamate reptiles. Lizards evolved a diversity of skull shapes and feeding behaviors, thus it is expected that the morphology of the symphysis will correspond with functional patterns. Here, we present new histological data illustrating the morphology of the joint in a number of taxa including iguanians, geckos, scincomorphs, lacertoids, and anguimorphs. The symphyses of all taxa exhibit dorsal and ventral fibrous portions of the joints that possess an array of parallel and woven collagen fibers. The middle and ventral portions of the joints are complemented by contributions of Meckel's cartilage. Kinetic taxa have more loosely built symphyses with large domains of parallel-oriented fibers whereas hard biting and akinetic taxa have symphyses primarily composed of dense, woven fibers. Whereas most taxa maintain unfused Meckel's cartilages, iguanians, and geckos independently evolved fused Meckel's cartilages; however, the joint's morphologies suggest different developmental mechanisms. Fused Meckel's cartilages may be associated with the apomorphic lingual behaviors exhibited by iguanians (tongue translation) and geckos (drinking). These morphological data shed new light on the functional, developmental, and evolutionary patterns displayed by the heads of lizards.