Anatomical differences in olfactory structures point to a more highly developed olfactory sense in the frugivorous bat ArEibeus jumuicensis than in the insectivorous bat Myotis lucifugus. Artibeus' nostfils show greater potential for differential control of nasal airstreams. Its nasal cavities, in contrast to Myotis, are clearly demarcated into olfactory and respiratory portions. Both species have seven turbinals, but of the five ethmoturbinals, Artibeus has four endoturbinals and one ectoturbinal whereas Myotis has three and two, respectively. The configuration and histology of the more complex turbinals of Artibeus indicates a greater surface area of olfactory epithelium. The nasal epithelia are thicker in Artibeus. Olfactory receptors appear similar in both species but the thickness and composition of the olfactory epithelium in Artibeus suggests the presence of about twice as many receptors per unit area. This is also reflected in the relative prominence of olfactory nerve bundles. From these and other bulbar relationships we conclude that the proportion of fila olfactoria to large mitral cells, as reflected by the olfactory bulb glomeruli, is some function of a fundamental 2:l relationship. Nasal glands, with flaps covering two of their more prominent ducts, and blood vessels are more pronounced in Artibeus. This presumably correlates with the nasal type of phonation exhibited by this bat as well as a greater ability to condition air per se. Nasopalatine ducts exist in both species but only Artibeus has a vomeronasal organ. A diffuse ganglion accompanies the organ; some of its neurons are associated with the unmyelinated vomeronasal nerve, whereas others are intraepithelial. The vomeronasal nerve terminates in a prominent accessory olfactory bulb.A relatively voluminous literature is available concerning most aspects of chiropteran morphology (Grass&, '55; Wimsatt, '70), but conspicuously few of these works deal specifically with the olfactory system (Allen, 1882; Grosser, '00; Matthes, '34; Kolb and Pisker, '64; Gurtovoi, '66; Suthers, '70; Kolb, '71; Schmidt and Greenhall, '71). Furthermore, none of these studies include a comprehensive interspecific comparison encompassing, in addition to the nasal cavities themselves, the peripheral olfactory organs and accessory structures associated with them. We here present such a comparison in sufficient detail to suggest the scope of associated adaptive problems encountered by macrosmatic and microsmatic bats. Several lines of evidence were used (Bhatnagar, '72) Bony structures were examined in three skulls of Artibeus and five of Myotis. One Artibeus and three Myotis were anesthetized with ether and injected with colored latex via the uropatagial vein to display the veins and via the left ventricle for the arteries. One anesthetized Artibeus and four Myotis were embalmed (with a formalin-ethanol-phenol-glycerine-water mixture) for study of soft tissues in the gross.Three Artibeus and seven Myotis were perfused, via the left ventricle, with 0.9% saline c...

Relationships between the cribriform plate of the ethmoid, the olfactory bulb, and olfactory acuity were explored using material from 13 of the 17 bat families.All megachiropteran cribriform plates were entirely perforated. In contrast, microchiropteran plates showed distinct perforated portions dorsally and nonperforated portions ventrally. The plates of frugivorous species had more foramina than those of insectivorous ones. Bats with mixed dietary habits were intermediate. Our data suggest that the Chilonycterinae were originally frugivorous, and have only secondarily reverted to an insectivorous diet.

The masticatory apparatus of the vespertilionid bat Myotis lucifugus appears generalized. Principal modifications for more efficient trituration have involved accessory tooth cusps. Chewing strokes pass through orbits (up to 7/sec) involving translations along and rotation about three axes. Direction of chewing typically reverses by at least the fifth or sixth consecutive orbit. Reversal involves modification of the downstroke at varying positions along its course. Compared to certain other bats, which do not utilize oral phonation for echolocation, Myotis chews much more rapidly, with many more degrees of freedom in orbital configuration. The overall envelope of motion is remarkably similar in all these species. The jaw muscles of Myotis act asymmetrically, and in more than one direction as the orbit progresses. They overlap in their periods of activity forming a continually-modified muscular sling. Unilateral force couples facilitate orthal rotation at the condyles and movements of them. Bilateral couples, pitting protrusors of one side against retrusors of the other, facilitate lateral translation. The pterygoids are instrumental in continuing motion across the top and bottom of the orbit. Countercontractions are particularly important in stabilizing and protecting the temporomandibular joints. The mandibular symphyseal joint appears to act passively, providing additional flexibility for the system. Higher nervous control beyond the simple jaw-opening reflex appears necessary to explain the firing order of the digastrics and the phase relationship of orbital reversal to overall muscular firing intensity. Control mechanisms, ancillary phenomena and comparative aspects are discussed.

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