Extensively remodeled, fractured cetacean tympanic bullae show that whales can survive traumatic injury to the ears

Abstract

Underwater human activities and anthropogenic noise in our oceans may be a major source of habitat degradation for marine life. This issue was highlighted by the opening of the United States Eastern Seaboard for seismic oil and gas exploration in 2014, which generated massive media coverage and widespread concern that seismic surveys could kill or deafen whales. We discovered 11 new specimens of fractured and healed cetacean ear bones, out of a survey of 2127 specimens housed in museum collections. This rare condition has been previously reported only in two specimens of blue whales (Balaenoptera musculus) from the early 1900s, summarized by Fraser & Purves (1953). All of our new specimens are represented by species for which this condition had never been reported previously, including both baleen and toothed whales. The baleen whale specimens (Balaenoptera physalus, Balaenoptera borealis, Balaenoptera acutorostrata) were collected during Canadian commercial whaling operations in the Atlantic Ocean in the 1970s; the specimens include ear bones with well-healed fractures, demonstrating that baleen whales are capable of overcoming traumatic injury to the ears. The toothed whale specimens (Delphinus sp., Berardius bairdii) were found dead on beaches in 1972 and 2001, respectively, with less remodeled fractures. Thus, ear injuries may be more lethal to the echolocating toothed whales, which rely on hearing for navigation and foraging. We explore several hypotheses regarding how these injuries could have occurred, and conclude that the most parsimonious explanations appear to be both direct and indirect effects of lytic processes from disease or calcium depletion, or damage from external pressure waves. Although further research is required to confirm whether the fractures resulted from natural or human-induced events, this study underscores the importance of museum collections and the work of stranding networks in understanding the potential effects of modern human activities on marine mammal health.

Extreme biomineralization: the case of the hypermineralized ear bone of gray whale (Eschrichtius robustus)

“…Commonly such specimens represented in other studies remains to be white in color (see [23]) due to harsh initial chemical treatment using diverse bleaching reagents, or hydrogen peroxide. We have found photographs of similarly pigmented tympanic bullae only in the monograph by Huggenberger and coworkers [26] and in the paper by Yamato and co-workers [38]. To our great surprise, we managed to find this pigmentation after a bone fracture under a mechanical press (Fig.…”

“…In addition, the nature and origin of the "organic matrix" not only with respect to commonly recognized collagenous template need to be studied in details. Obtaining of such data could be crucial for our understanding of remodeling and self-healing of fractured cetaceans tympanic bullae reported in the literature [38]. The mechanism underlying remineralization in vivo is unknown.…”

Traumatic Tympanic Bulla Fracture in a Cat With Severe Head Trauma

“…There have been only a very few reports describing traumatic tympanic bulla fractures in the veterinary literature ( 4 – 6 ). To the author's knowledge, there is only one case reported of traumatic tympanic bulla fracture in the cat ( 5 ), which lacks the case follow up and only use plain x-rays as diagnostic imaging test.…”

“…The presence of traumatic tympanic bullae fractures in whale skulls has also been reported (6). Humans lack tympanic bulla, but fractures affecting the tympanic region of the temporal bone are much more common and well-described in the literature.…”