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Vandenberg ML, Cohen KE, Rubin RD, Goldbogen JA, Summers AP, Paig-Tran EWM, Kahane-Rapport SR. Formation of a fringe: A look inside baleen morphology using a multimodal visual approach. J Morphol 2023; 284:e21574. [PMID: 36807194 DOI: 10.1002/jmor.21574] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Revised: 12/22/2022] [Accepted: 12/26/2022] [Indexed: 02/23/2023]
Abstract
Filter-feeding has been present for hundreds of millions of years, independently evolving in aquatic vertebrates' numerous times. Mysticete whales are a group of gigantic, marine filter-feeders that are defined by their fringed baleen and are divided into two groups: balaenids and rorquals. Recent studies have shown that balaenids likely feed using a self-cleaning, cross-flow filtration mechanism where food particles are collected and then swept to the esophagus for swallowing. However, it is unclear how filtering is achieved in the rorquals (Balaenopteridae). Lunging rorqual whales engulf enormous masses of both prey and water; the prey is then separated from the water through baleen plates lining the length of their upper jaw and positioned perpendicular to flow. Rorqual baleen is composed of both major (larger) and minor (smaller) keratin plates containing embedded fringe that extends into the whale's mouth, forming a filtering fringe. We used a multimodal approach, including microcomputed tomography (µCT) and scanning electron microscopy (SEM), to visualize and describe the variability in baleen anatomy across five species of rorqual whales, spanning two orders of magnitude in body length. For most morphological measurements, larger whales exhibited hypoallometry relative to body length. µCT and SEM revealed that the major and minor plates break away from the mineralized fringes at variable distances from the gums. We proposed a model for estimating the effective pore size to determine whether flow scales with body length or prey size across species. We found that pore size is likely not a proxy for prey size but instead, may reflect changes in resistance through the filter that affect fluid flow.
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Affiliation(s)
- Megan L Vandenberg
- Department of Biology, University of Washington, Seattle, Washington, USA
- Friday Harbor Laboratories, University of Washington, Friday Harbor, Washington, USA
| | - Karly E Cohen
- Department of Biology, University of Washington, Seattle, Washington, USA
- Friday Harbor Laboratories, University of Washington, Friday Harbor, Washington, USA
| | | | - Jeremy A Goldbogen
- Hopkins Marine Station, Stanford University, Pacific Grove, California, USA
| | - Adam P Summers
- Department of Biology, University of Washington, Seattle, Washington, USA
- Friday Harbor Laboratories, University of Washington, Friday Harbor, Washington, USA
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Segre PS, Weir CR, Stanworth A, Cartwright S, Friedlaender AS, Goldbogen JA. Biomechanically distinct filter-feeding behaviors distinguish sei whales as a functional intermediate and ecologically flexible species. J Exp Biol 2021. [DOI: 10.1242/jeb.238873] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
ABSTRACT
With their ability to facultatively switch between filter-feeding modes, sei whales represent a functional and ecological intermediate in the transition between intermittent and continuous filter feeding. Morphologically resembling their lunge-feeding, rorqual relatives, sei whales have convergently evolved the ability to skim prey near the surface of the water, like the more distantly related balaenids. Because of their intermediate nature, understanding how sei whales switch between feeding behaviors may shed light on the rapid evolution and flexibility of filter-feeding strategies. We deployed multi-sensor bio-logging tags on two sei whales and measured the kinematics of feeding behaviors in this poorly understood and endangered species. To forage at the surface, sei whales used a unique combination of surface lunges and skim-feeding behaviors. The surface lunges were slow and stereotyped, and were unlike lunges performed by other rorqual species. The skim-feeding events featured a different filtration mechanism from the lunges and were kinematically different from the continuous filter feeding used by balaenids. While foraging below the surface, sei whales used faster and more variable lunges. The morphological characteristics that allow sei whales to effectively perform different feeding behaviors suggest that sei whales rapidly evolved their functionally intermediate and ecologically flexible form to compete with larger and more efficient rorqual species.
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Affiliation(s)
- Paolo S. Segre
- Hopkins Marine Station, Stanford University, Pacific Grove, CA 93950, USA
| | | | | | | | - Ari S. Friedlaender
- Institute of Marine Sciences, University of California, Santa Cruz, Santa Cruz, CA 95064, USA
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Werth AJ, Sformo TL, Lysiak NS, Rita D, George JC. Baleen turnover and gut transit in mysticete whales and its environmental implications. Polar Biol 2020. [DOI: 10.1007/s00300-020-02673-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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Lanzetti A. Prenatal developmental sequence of the skull of minke whales and its implications for the evolution of mysticetes and the teeth-to-baleen transition. J Anat 2019; 235:725-748. [PMID: 31216066 DOI: 10.1111/joa.13029] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/15/2019] [Indexed: 12/13/2022] Open
Abstract
Baleen whales (Mysticeti) have an extraordinary fossil record documenting the transition from toothed raptorial taxa to modern species that bear baleen plates, keratinous bristles employed in filter-feeding. Remnants of their toothed ancestry can be found in their ontogeny, as they still develop tooth germs in utero. Understanding the developmental transition from teeth to baleen and the associated skull modifications in prenatal specimens of extant species can enhance our understanding of the evolutionary history of this lineage by using ontogeny as a relative proxy of the evolutionary changes observed in the fossil record. Although at present very little information is available on prenatal development of baleen whales, especially regarding tooth resorption and baleen formation, due to a lack of specimens. Here I present the first detailed description of prenatal specimens of minke whales (Balaenoptera acutorostrata and Balaenoptera bonaerensis), focusing on the skull anatomy and tooth germ development, resorption, and baleen growth. The ontogenetic sequence described consists of 10 specimens of both minke whale species, from the earliest fetal stages to full term. The internal skull anatomy of the specimens was visualized using traditional and iodine-enhanced computed tomography scanning. These high-quality data allow detailed description of skull development both qualitatively and quantitatively using three-dimensional landmark analysis. I report distinctive external anatomical changes and the presence of a denser tissue medial to the tooth germs in specimens from the final portion of gestation, which can be interpreted as the first signs of baleen formation (baleen rudiments). Tooth germs are only completely resorbed just before the eruption of the baleen from the gums, and they are still present for a brief period with baleen rudiments. Skull shape development is characterized by progressive elongation of the rostrum relative to the braincase and by the relative anterior movement of the supraoccipital shield, contributing to a defining feature of cetaceans, telescoping. These data aid the interpretation of fossil morphologies, especially of those extinct taxa where there is no direct evidence of presence of baleen, even if caution is needed when comparing prenatal extant specimens with adult fossils. The ontogeny of other mysticete species needs to be analyzed before drawing definitive conclusions about the influence of development on the evolution of this group. Nonetheless, this work is the first step towards a deeper understanding of the most distinctive patterns in prenatal skull development of baleen whales, and of the anatomical changes that accompany the transition from tooth germs to baleen. It also presents comprehensive hypotheses to explain the influence of developmental processes on the evolution of skull morphology and feeding adaptations of mysticetes.
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Affiliation(s)
- Agnese Lanzetti
- Department of Biology, San Diego State University, San Diego, CA, USA
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Werth AJ, Blakeney SM, Cothren AI. Oil adsorption does not structurally or functionally alter whale baleen. ROYAL SOCIETY OPEN SCIENCE 2019; 6:182194. [PMID: 31218043 PMCID: PMC6549998 DOI: 10.1098/rsos.182194] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/22/2018] [Accepted: 04/24/2019] [Indexed: 06/09/2023]
Abstract
Mysticete whales filter small prey from seawater using baleen, a unique keratinous oral tissue that grows from the palate, from which it hangs in hundreds of serial plates. Laboratory experiments testing effects of oils on material strength and flexibility, particle capture and tissue architecture of baleen from four mysticete species (bowhead, Balaena mysticetus; North Atlantic right, Eubalaena glacialis; fin, Balaenoptera physalus; humpback, Megaptera novaeangliae) indicate that baleen is hydrophilic and oleophobic, shedding rather than adsorbing oil. Oils of different weights and viscosities were tested, including six petroleum-based oils and two fish or plankton oils of common whale prey. No notable differences were found by oil type or whale species. Baleen did not adsorb oil; oil was readily rinsed from baleen by flowing water, especially from moving fringes. Microscopic examination shows minimal wrinkling or peeling of baleen's cortical keratin layers, probably due to oil repelling infiltrated water. Combined results cast doubt on fears of baleen fouling by oil; filter porosity is not appreciably affected, but oil ingestion risks remain. Particle capture studies suggest potentially greater danger to mysticetes from plastic pollution than oil.
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6
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Laitman JT, Albertine KH. The Anatomical Record
Returns to the Sea: Exploring the Great Whales and Their Interesting Relatives. Anat Rec (Hoboken) 2019; 302:659-662. [DOI: 10.1002/ar.24119] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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7
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Werth AJ, Rita D, Rosario MV, Moore MJ, Sformo TL. How do baleen whales stow their filter? A comparative biomechanical analysis of baleen bending. ACTA ACUST UNITED AC 2018; 221:jeb.189233. [PMID: 30337355 DOI: 10.1242/jeb.189233] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Accepted: 10/11/2018] [Indexed: 11/20/2022]
Abstract
Bowhead and right whale (balaenid) baleen filtering plates, longer in vertical dimension (≥3-4 m) than the closed mouth, presumably bend during gape closure. This has not been observed in live whales, even with scrutiny of video-recorded feeding sequences. To determine what happens to the baleen during gape closure, we conducted an integrative, multifactorial study including materials testing, functional (flow tank and kinematic) testing and histological examination. We measured baleen bending properties along the dorsoventral length of plates and anteroposterior location within a rack of plates via mechanical (axial bending, composite flexure, compression and tension) tests of hydrated and air-dried tissue samples from balaenid and other whale baleen. Balaenid baleen is remarkably strong yet pliable, with ductile fringes, and low stiffness and high elasticity when wet; it likely bends in the closed mouth when not used for filtration. Calculation of flexural modulus from stress/strain experiments shows that the balaenid baleen is slightly more flexible where it emerges from the gums and at its ventral terminus, but kinematic analysis indicates plates bend evenly along their whole length. Fin and humpback whale baleen has similar material properties but less flexibility, with no dorsoventral variation. The internal horn tubes have greater external and hollow luminal diameter but lower density in the lateral relative to medial baleen of bowhead and fin whales, suggesting a greater capacity for lateral bending. Baleen bending has major consequences not only for feeding morphology and energetics but also for conservation given that entanglement in fishing gear is a leading cause of whale mortality.
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Affiliation(s)
- Alexander J Werth
- Department of Biology, Hampden-Sydney College, Hampden-Sydney, VA 23943, USA
| | - Diego Rita
- Department of Evolutionary Biology, Ecology, and Environmental Science, University of Barcelona, 08028 Barcelona, Spain
| | - Michael V Rosario
- Department of Ecology & Evolutionary Biology, Brown University, Providence, RI 02912, USA
| | - Michael J Moore
- Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
| | - Todd L Sformo
- Department of Wildlife Management, North Slope Borough, Barrow, AK 99723, USA.,Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775, USA
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Lanzetti A, Berta A, Ekdale EG. Prenatal Development of the Humpback Whale: Growth Rate, Tooth Loss and Skull Shape Changes in an Evolutionary Framework. Anat Rec (Hoboken) 2018; 303:180-204. [DOI: 10.1002/ar.23990] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2017] [Revised: 01/15/2018] [Accepted: 01/24/2018] [Indexed: 01/01/2023]
Affiliation(s)
- Agnese Lanzetti
- Department of BiologySan Diego State University San Diego California
| | - Annalisa Berta
- Department of BiologySan Diego State University San Diego California
| | - Eric G. Ekdale
- Department of BiologySan Diego State University San Diego California
- San Diego Natural History Museum San Diego California
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Werth AJ, Potvin J, Shadwick RE, Jensen MM, Cade DE, Goldbogen JA. Filtration area scaling and evolution in mysticetes: trophic niche partitioning and the curious cases of sei and pygmy right whales. Biol J Linn Soc Lond 2018. [DOI: 10.1093/biolinnean/bly121] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Affiliation(s)
- Alexander J Werth
- Department of Biology, Hampden-Sydney College, Hampden-Sydney, VA, USA
| | - Jean Potvin
- Department of Physics, Saint Louis University, St. Louis, MO, USA
| | - Robert E Shadwick
- Department of Zoology, University of British Columbia, Vancouver, B.C., Canada
| | - Megan M Jensen
- Department of Biology, Hopkins Marine Station, Stanford University, Pacific Grove, CA, USA
| | - David E Cade
- Department of Biology, Hopkins Marine Station, Stanford University, Pacific Grove, CA, USA
| | - Jeremy A Goldbogen
- Department of Biology, Hopkins Marine Station, Stanford University, Pacific Grove, CA, USA
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Vogl W. A "Welcoming" Introduction to a Canadian Northwest Coast Thematic Papers Issue. Anat Rec (Hoboken) 2018; 300:1930-1934. [PMID: 28971625 DOI: 10.1002/ar.23675] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Accepted: 08/05/2017] [Indexed: 12/21/2022]
Abstract
In this commentary, I provide an introduction to and the context for the four articles in the thematic series published to celebrate the Editorial Board Meeting of the Anatomical Record in Vancouver, British Columbia, Canada in July of 2017. The articles describe various aspects of whale anatomy and the potential for a new generation of digital tags to provide information on functional anatomy of free swimming animals in the wild. The whales described are all native to the northwest coast of North America, as well as being found elsewhere, and the authors are related in some way to the University of British Columbia in Vancouver. Anat Rec, 300:1930-1934, 2017. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Wayne Vogl
- Department of Cellular and Physiological Sciences, Life Science Centre, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
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