Brachygnathia Superior Observed in a Juvenile Common Bottlenose Dolphin (Tursiops truncatus)

Brachygnathism is a congenital malformation involving an abnormal truncation of the maxillae (brachygnathia superior) or mandibles (brachyg nathia inferior), which can lead to a severe malocclusion (Barker etal., 1993). This condition iscommonly seen in species such as cattle (Kene & Uwagie-Ero, 2001; Citek et al., 2009; Hoy et al., 2011), dogs (Fox, 1963; Borissov et al., 2004), wild ungulates (Hoy et al., 2011), and humans (Mackay et al., 1992; Ariji et al., 2000). The few descriptions of brachygna thism in cetaceans have resulted from examinations of stranded dolphins. Elorriaga-Verplancken et al. (2015) reported a live stranded common bottlenose dolphin (Zursiops truncatus; hereafter bottlenose dolphin), which presented with both brachygnathia superior and a severe oral infestation of rabbit-ear barnacles (Conchoderma auritum). In this case, the distal halves of the maxillae were abnormally truncated, measuring approximately one half the length of the mandible. Traumatic injury could not be ruled out as the cause of this particular deformity, perhaps in part due to the damage incurred from the described barnacle infestation. However, the authors posited that the barnacle growth was facilitated by the presence of exposed teeth caused by the rostral deformity. In this case, the animal presented with a healthy overall body condition, suggesting that the deformity did not significantly affect the animal's ability to hunt. Similar observations of brachygnathia infe-Tior were observed by Van Bressem et al. (2006) in a long-beaked common dolphin (Delphinus deiphis [originally reported as D. capensis}) taken as fisherles bycatch in Peru. In this case, the distal halves of the maxillae and mandible were curved upwards, and the mandible was observed to be shorter than both the maxillaries and premaxillaries; however, a similar barnacle infestation was not observed. This animal also presented with a healthy body condition, indicating that the animal was able to forage effectively. © 2021, Aquatic Mammals. All Rights Reserved.