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Denk M, McLellan W, Pabst DA, Rommel S, Keenan T, Sharp S, Niemeyer M, Hunter N, Block G, Nelson N, Harms C, Thornton S, Costidis A, Moore M. Melon and rostral muscle morphology of Gervais' beaked whale (Mesoplodon europaeus): Alternating patterns of bilateral asymmetry. Anat Rec (Hoboken) 2024; 307:633-657. [PMID: 37548999 DOI: 10.1002/ar.25301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Revised: 07/08/2023] [Accepted: 07/20/2023] [Indexed: 08/08/2023]
Abstract
Toothed whales utilize specialized nasal structures such as the lipid-rich melon to produce sound and propagate it into the aquatic environment. Very little nasal morphology of mesoplodont beaked whales has been described in the literature, and the anatomy of the melon and associated musculature of Gervais' beaked whale (Mesoplodon europaeus) remains undescribed. Heads of three (n = 3) Gervais' beaked whales were examined in detail via dissection as well as computed tomography (CT) and magnetic resonance imaging (MRI). Two additional Gervais' beaked whale individuals (n = 2) were studied via archived CT and MRI scans. Representative transverse dissection sections of the melon were processed for polarized light imaging to verify the presence of tendons inserting into the melon tissue. Three-dimensional (3D) CT reconstructions of the melon, rostral muscles, and associated structures were performed to assess morphology and spatial relationships. In all individuals, the melon's main body demonstrated a bilaterally asymmetrical, curvilinear geometry. This curvilinear shape was defined by a pattern of alternating asymmetry in the medial rostral muscles that projected into the melon's tissue. In transverse polarized light imaging, a network of tendons originating from these asymmetrical rostral muscle projections was observed permeating the melon's lipid tissue. This curvilinear melon morphology and associated asymmetrical musculature suggest a means of lengthening the lipid pathway within a relatively short dimensional footprint. In addition, the species-specific arrangement of muscular projections suggests complex fine-tuning of the melon's geometry during echolocation. Further studies may lend additional insight into the function of this unusual melon morphology.
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Affiliation(s)
- Michael Denk
- Biology Department, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA
- Cape May Whale Watch and Research Center, Cape May, New Jersey, USA
| | - William McLellan
- Department of Biology and Marine Biology, University of North Carolina Wilmington USA, Wilmington, North Carolina, USA
| | - D Ann Pabst
- Department of Biology and Marine Biology, University of North Carolina Wilmington USA, Wilmington, North Carolina, USA
| | - Sentiel Rommel
- Department of Biology and Marine Biology, University of North Carolina Wilmington USA, Wilmington, North Carolina, USA
| | - Tiffany Keenan
- Department of Biology and Marine Biology, University of North Carolina Wilmington USA, Wilmington, North Carolina, USA
| | - Sarah Sharp
- International Fund for Animal Welfare, Yarmouth Port, Massachusetts, USA
| | - Misty Niemeyer
- International Fund for Animal Welfare, Yarmouth Port, Massachusetts, USA
| | - Nicole Hunter
- International Fund for Animal Welfare, Yarmouth Port, Massachusetts, USA
| | - Gary Block
- Ocean State Veterinary Specialists, East Greenwich, Rhode Island, USA
| | - Nathan Nelson
- Department of Molecular Biomedical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina, USA
| | - Craig Harms
- Department of Molecular Biomedical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina, USA
| | - Steven Thornton
- Department of Biology and Marine Biology, University of North Carolina Wilmington USA, Wilmington, North Carolina, USA
| | | | - Michael Moore
- Biology Department, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA
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Frainer G, Huggenberger S, Moreno IB, Plön S, Galatius A. Head adaptation for sound production and feeding strategy in dolphins (Odontoceti: Delphinida). J Anat 2021; 238:1070-1081. [PMID: 33319356 PMCID: PMC8053589 DOI: 10.1111/joa.13364] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Revised: 10/29/2020] [Accepted: 11/02/2020] [Indexed: 01/01/2023] Open
Abstract
Head morphology in toothed whales evolved under selective pressures on feeding strategy and sound production. The postnatal development of the skull (n = 207) and mandible (n = 219) of six Delphinida species which differ in feeding strategy but exhibit similar sound emission patterns, including two narrow-band high-frequency species, were investigated through 3D morphometrics. Morphological changes throughout ontogeny were demonstrated based on the main source of variation (i.e., prediction lines) and the common allometric component. Multivariate trajectory analysis with pairwise comparisons between all species was performed to evaluate specific differences on the postnatal development of skulls and mandibles. Changes in the rostrum formation contributed to the variation (skull: 49%; mandible: 90%) of the entire data set and might not only reflect the feeding strategy adopted by each lineage but also represents an adaptation for sound production and reception. As an important structure for directionality of sound emissions, this may increase directionality in raptorial feeders. Phylogenetic generalized least squares analyses indicated that shape of the anterior portion of the skull is strongly dependent on phylogeny and might not only reflect feeding mode, but also morphological adaptations for sound production, particularly in raptorial species. Thus, postnatal development seems to represent a crucial stage for biosonar maturation in some raptorial species such as Pontoporia blainvillei and Sousa plumbea. The ontogeny of their main tool for navigation and hunting might reflect their natural history peculiarities and thus potentially define their main vulnerabilities to anthropogenic changes in the environment.
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Affiliation(s)
- Guilherme Frainer
- Programa de Pós-Graduação em Biologia Animal, Departamento de Zoologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | | | - Ignacio B Moreno
- Programa de Pós-Graduação em Biologia Animal, Departamento de Zoologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.,Centro de Estudos Costeiros, Limnológicos e Marinhos (CECLIMAR/CLN/UFRGS), Universidade Federal do Rio Grande do Sul, Imbé, Brazil
| | - Stephanie Plön
- Bayworld Centre for Research and Education (BCRE), Port Elizabeth, South Africa
| | - Anders Galatius
- Marine Mammal Research, Department of Bioscience, Aarhus University, Roskilde, Denmark
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Frainer G, Moreno IB, Serpa N, Galatius A, Wiedermann D, Huggenberger S. Ontogeny and evolution of the sound-generating structures in the infraorder Delphinida (Odontoceti: Delphinida). Biol J Linn Soc Lond 2019. [DOI: 10.1093/biolinnean/blz118] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
AbstractThe ontogeny of the structures involved in sound generation and modulation in dolphins was investigated through a comparison of the soft nasal structures of foetal, perinatal, neonatal and adult specimens of Pontoporiidae, Phocoenidae and Delphinidae. Foetal samples were sectioned at 10 µm in the saggital and coronal planes, and stained for histological examination. Computed tomography and magentic resonance imaging scan series were combined with new data to represent the ontogenetic stages of the three groups. The images were analysed in 3D-Slicer to characterize the general head topography. The origins of the melon and the vestibular air sac were detected between Carnegie stages C16 and F22. The three groups analysed showed distinct formation of the nasal plug and nasal plug muscles, mainly with regard to the loss of fat pathways (or their maintenance in Pontoporiidae) and the development of the nasal plug muscles on both sides (during perinatal development of Phocoenidae) or just on the left side (during postnatal development in Delphinidae). Broadband vocalizing delphinidans might have evolved under heterochronic events acting on the formation of sound-generating structures such as the rostrum and vestibular air sacs, and on the transformation of the branches of the melon, probably leading to a reduced directionality of the sonar beam.
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Affiliation(s)
- Guilherme Frainer
- Programa de Pós-Graduação em Biologia Animal, Departamento de Zoologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
- Centro de Estudos Costeiros, Limnológicos e Marinhos (CECLIMAR/UFRGS), Campus Litoral Norte, Universidade Federal do Rio Grande do Sul, Imbé, Brazil
- Department II of Anatomy, University of Cologne, Cologne, Germany
| | - Ignacio B Moreno
- Programa de Pós-Graduação em Biologia Animal, Departamento de Zoologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
- Centro de Estudos Costeiros, Limnológicos e Marinhos (CECLIMAR/UFRGS), Campus Litoral Norte, Universidade Federal do Rio Grande do Sul, Imbé, Brazil
| | - Nathalia Serpa
- Programa de Pós-Graduação em Biologia Animal, Departamento de Zoologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
- Centro de Estudos Costeiros, Limnológicos e Marinhos (CECLIMAR/UFRGS), Campus Litoral Norte, Universidade Federal do Rio Grande do Sul, Imbé, Brazil
| | - Anders Galatius
- Department of Bioscience, Aarhus University, Roskilde, Denmark
| | - Dirk Wiedermann
- Max Planck Institute for Metabolism Research, Cologne, Germany
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