A comparative study of incisor procumbency and mandibular morphology in vampire bats

Abstract

The three species of vampire bats (Phyllostomidae: Desmodontinae), Desmodus rotundus, Diaemus youngi, and Diphylla ecaudata, are the only mammals that obtain all nutrition from vertebrate blood (sanguinivory). Because of the unique challenges of this dietary niche, vampire bats possess a suite of behavioral, physiological, and morphological specializations. Morphological specializations include a dentition characterized by small, bladelike, non-occlusive cheek teeth, large canines, and extremely large, procumbent, sickle-shaped upper central incisors. The tips of these incisors rest in cuplike pits in the mandible behind the lower incisors (mandibular pits). Here, we use microCT scanning and high-resolution radiography to describe the morphology of the mandible and anterior dentition in vampire bats, focusing on the relationship between symphyseal fusion, mandibular pit size, incisor size, and procumbency. In Desmodus and Diaemus, highly procumbent upper incisors are associated with relatively small mandibular pits, an unfused mandibular symphysis with substantial bony interdigitations linking the dentaries, and a diastema between the lower central incisors that helps to facilitate the lapping of blood from a wound. In Diphylla, less procumbent upper incisors are associated with relatively large mandibular pits, a completely fused mandibular symphysis, and a continuous lower toothrow lacking a central diastema. We hypothesize that symphyseal morphology and the presence or absence of the diastema are associated with the angle of upper incisor procumbency and mandibular pit development, and that spatial constraints influence the morphology of the symphysis. Finally, this morphological variation suggests that Diphylla utilizes a different feeding strategy as compared to Desmodus and Diaemus, possibly resulting from the functional demands of specialization on avian, rather than mammalian, blood.

The mechanical significance of morphological variation in the macaque mandibular symphysis during mastication

“…The question that needs to be asked is not which type of loading accounts for a specific morphology but what determines which of these mechanical viable solutions develops in the symphysis. The close relationship between the morphology of the incisors and symphyseal region (including symphyseal fusion) has been noted in previous studies (Williams et al, 2008;Davis et al, 2010;Cobb and Panagiotopoulou, 2011).…”

The adaptive significance of mandibular symphyseal fusion in mammals

“…(2008) argued that the symphyses of camelid artiodactyls are fused because the large, medially positioned mandibular incisor roots of these species would compromise the structural integrity of a partially fused joint. This hypothesis was invoked by Davis et al. (2010) to explain variation in fusion in vampire bats (Desmodontinae).…”

Vampire Bat Rabies: Ecology, Epidemiology and Control

“…Firstly, the species feeds on a wide range of hosts, including humans, although will preferentially feed on large livestock such as cattle and horses. The teeth of D. rotundus are blade-like (Figure 1a) and undergo thegosis, a process of self-sharpening in which the upper incisors brush against the lower canines [19]. This ensures that the bat can deliver a virtually painless bite, creating a distinctive crater-like wound on the host.…”