title: Precocious Ossification of the Tympanoperiotic Bone in Fetal and Newborn Dolphins: An Evolutionary Adaptation to the Aquatic Environment?
abstract: The present study, performed with a dual-energy X-ray (DXA) bone densitometer on a series of fetal and newborn striped and short-beaked common dolphins, shows that the bone density of the area of the tympanic bulla within the tympanoperiotic complex starts with 0.483 g cm(-2) in 5- to 6-month-old specimens of striped (or common) dolphin fetuses and reaches 1.841 g cm(-2) in newborn striped dolphins, with values consistently higher than in other parts of the skull or elsewhere in the skeleton. The same results apply to the common bottlenose dolphins, in which the area of the tympanic bulla has a density of 0.312 g cm(-2) in 5-month-old specimens and becomes four times as much in newborns. Regardless of the areal bone density results correlated to the DXA-technique, comparisons with DXA-bone density data in the literature referred to other mammals emphasize the presence of very high mineral deposition in the area of the tympanoperiotic bone in fetal and newborn dolphins and the most dense part of it belongs to the tympanic bulla. The early osseous maturation of the tympanic bulla area may be compared to what described in fin whales and may represent an unique ontogenetic and phylogenetic feature of cetaceans, possibly related to the development of essential acoustic sense and establishment of immediate post-natal mother-calf relationship.
authors: Department of Comparative Biomedicine and Food Science, University of Padova, Legnaro, (PD), 35020, Italy.
authors: Bruno
authors: B
authors: Cozzi
authors: Museum of Natural History of Milan, Milan, 20121, Italy.
authors: Michela
authors: M
authors: Podestà
authors: Department of Animal Medicine, Production and Health, University of Padova, Legnaro, (PD), 35020, Italy.
authors: Calogero
authors: C
authors: Vaccaro
authors: Civic Museum of Natural History "G, Doria,", Genova, 16121, Italy.
authors: Roberto
authors: R
authors: Poggi
authors: Department of Comparative Biomedicine and Food Science, University of Padova, Legnaro, (PD), 35020, Italy.
authors: Sandro
authors: S
authors: Mazzariol
authors: Department II of Anatomy, University of Cologne, Cologne, 50924, Germany.
authors: Stefan
authors: S
authors: Huggenberger
authors: Department of Animal Medicine, Production and Health, University of Padova, Legnaro, (PD), 35020, Italy.
authors: Alessandro
authors: A
authors: Zotti
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000818:Animals; D000831:Animals, Newborn; D005075:Biological Evolution; D004289:Dolphins / Q000502:physiology*; D017753:Ecosystem; D010012:Osteogenesis / Q000502:physiology*; D013701:Temporal Bone / Q000502:physiology*
keywords: DXA; dolphins; fetal development; tympanic bulla; tympanoperiotic bone