The Scutulum and the Pre-Auricular Aponeurosis in Bats.

The external ear in eutherian mammals is composed of the annular, auricular (pinna), and scutellar cartilages. The latter extends between the pinnae, across the top of the head, and lies at the intersection of numerous auricular muscles and is thought to be a sesamoid element. In bats, this scutulum consists of two distinct regions, (1) a thin squama that is in contact with the underlying temporalis fascia and (2) a lateral bossed portion that is lightly tethered to the medial surface of the pinna.

The hyoid as a sound conducting apparatus in laryngeally echolocating bats.

The morphology of the stylohyal-tympanic bone articulation found in laryngeally echolocating bats is highly indicative of a function associated with signal production. One untested hypothesis is that this morphology allows the transfer of a sound signal from the larynx to the tympanic bones (auditory bulla) via the hyoid apparatus during signal production by the larynx. We used µCT data and finite element analysis to model the propagation of sound through the hyoid chain into the tympanic bones to test this hypothesis.

Reinforcement of the larynx and trachea in echolocating and non-echolocating bats.

The synchronization of flight mechanics with respiration and echolocation call emission by bats, while economizing these behaviors, presumably puts compressive loads on the cartilaginous rings that hold open the respiratory tract. Previous work has shown that during postnatal development of Artibeus jamaicensis (Phyllostomidae), the onset of adult echolocation call emission rate coincides with calcification of the larynx, and the development of flight coincides with tracheal ring calcification. In the present study, I assessed the level of reinforcement of the respiratory system in 13 bat species representing six families that use stereotypical modes of echolocation (i.

Megachiropteran bats profoundly unique from microchiropterans in climbing and walking locomotion: Evolutionary implications.

Understandably, most locomotor analyses of bats have focused on flight mechanics and behaviors. However, we investigated nonflight locomotion in an effort to glean deeper insights into the evolutionary history of bats. We used high-speed video (300 Hz) to film and compare walking and climbing mechanics and kinematics between several species of the suborders Megachiroptera (Pteropodidae) versus Microchiroptera (Vespertilionidae and Phyllostomatidae).

Calcification of the lower respiratory tract in relation to flight development in Jamaican fruit bats (Phyllostomidae, Artibeus jamaicensis).

The production of echolocation calls in bats along with forces produced by contraction of thoracic musculature used in flight presumably puts relatively high mechanical loads on the lower respiratory tract (LRT). Thus, there are likely adaptations to prevent collapse or distortion of the bronchial tree and trachea during flight in echolocating bats. By clearing and staining (Alcian blue and Alizarin red) LRTs removed from nonvolant neonates, semivolant juveniles, volant subadults, and adult Jamaican fruit bats (Artibeus jamaicensis), I found that calcification of the tracheal, primary bronchial, and secondary bronchial (lobar) cartilage rings occurs over the span of about 3 days and coincides with later developmental stages of flight and the increased production of echolocation calls.

Postnatal ontogeny of the cochlea and flight ability in Jamaican fruit bats (Phyllostomidae) with implications for the evolution of echolocation.

Recent evidence has shown that the developmental emergence of echolocation calls in young bats follow an independent developmental pathway from other vocalizations and that adult-like echolocation call structure significantly precedes flight ability. These data in combination with new insights into the echolocation ability of some shrews suggest that the evolution of echolocation in bats may involve inheritance of a primitive sonar system that was modified to its current state, rather than the ad hoc evolution of echolocation in the earliest bats. Because the cochlea is crucial in the sensation of echoes returning from sonar pulses, we tracked changes in cochlear morphology during development that included the basilar membrane (BM) and secondary spiral lamina (SSL) along the length of the cochlea in relation to stages of flight ability in young bats.

Ontogeny of the larynx and flight ability in Jamaican fruit bats (Phyllostomidae) with considerations for the evolution of echolocation.

Echolocating bats have adaptations of the larynx such as hypertrophied intrinsic musculature and calcified or ossified cartilages to support sonar emission. We examined growth and development of the larynx relative to developing flight ability in Jamaican fruit bats to assess how changes in sonar production are coordinated with the onset of flight during ontogeny as a window for understanding the evolutionary relationships between these systems. In addition, we compare the extent of laryngeal calcification in an echolocating shrew species (Sorex vagrans) and the house mouse (Mus musculus), to assess what laryngeal chiropteran adaptations are associated with flight versus echolocation.