1
|
Nieto-Miranda JJ, Aguilar-Medrano R, Hernández-Camacho CJ, Peredo CM, Cruz-Escalona VH. Mechanical properties of the California sea lion (Zalophus californianus) and northern elephant seal (Mirounga angustirostris) lower jaws explain trophic plasticity. Anat Rec (Hoboken) 2023; 306:2597-2609. [PMID: 36794994 DOI: 10.1002/ar.25180] [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: 07/05/2022] [Revised: 01/31/2023] [Accepted: 01/31/2023] [Indexed: 02/17/2023]
Abstract
The fossil record of pinnipeds documents a suite of morphological changes that facilitate their ecological transition from a terrestrial to an aquatic lifestyle. Among these is the loss of the tribosphenic molar and the behavior typically associated with it in mammals: mastication. Instead, modern pinnipeds exhibit a broad range of feeding strategies that facilitate their distinct aquatic ecologies. Here, we examine the feeding morphology of two species of pinnipeds with disparate feeding ecologies: Zalophus californianus, a specialized raptorial biter, and Mirounga angustirostris, a suction specialist. Specifically, we test whether the morphology of the lower jaws facilitates trophic plasticity in feeding for either of these species. We used finite element analysis (FEA) to simulate the stresses during the opening and closing of the lower jaws in these species to explore the mechanical limits of their feeding ecology. Our simulations demonstrate that both jaws are highly resistant to the tensile stresses experienced during feeding. The lower jaws of Z. californianus experienced the maximum stress at the articular condyle and the base of the coronoid process. The lower jaws of M. angustirostris experienced the maximum stress at the angular process and were more evenly distributed throughout the body of the mandible. Surprisingly, the lower jaws of M. angustirostris were even more resistant to the stresses experienced during feeding than those of Z. californianus. Thus, we conclude that the superlative trophic plasticity of Z. californianus is driven by other factors unrelated to the mandible's tensile resistance to stress during feeding.
Collapse
Affiliation(s)
- J Jesús Nieto-Miranda
- Instituto Politécnico Nacional, Escuela Superior de Ingeniería Mecánica y Eléctrica Unidad Azcapotzalco, Ciudad de México, Mexico
| | - Rosalía Aguilar-Medrano
- Departamento de Ecología Marina, Centro de Investigación Científica y de Educación Superior de Ensenada, Ensenada, Baja California, Mexico
| | - Claudia J Hernández-Camacho
- Instituto Politécnico Nacional, Centro Interdisciplinario de Ciencias Marinas, La Paz, Baja California Sur, Mexico
| | | | - Víctor Hugo Cruz-Escalona
- Instituto Politécnico Nacional, Centro Interdisciplinario de Ciencias Marinas, La Paz, Baja California Sur, Mexico
| |
Collapse
|
2
|
Werth AJ, Crompton AW. Cetacean tongue mobility and function: A comparative review. J Anat 2023; 243:343-373. [PMID: 37042479 PMCID: PMC10439401 DOI: 10.1111/joa.13876] [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: 02/01/2022] [Revised: 03/26/2023] [Accepted: 03/27/2023] [Indexed: 04/13/2023] Open
Abstract
Cetaceans are atypical mammals whose tongues often depart from the typical (basal) mammalian condition in structure, mobility, and function. Their tongues are dynamic, innovative multipurpose tools that include the world's largest muscular structures. These changes reflect the evolutionary history of cetaceans' secondary adaptation to a fully aquatic environment. Cetacean tongues play no role in mastication and apparently a greatly reduced role in nursing (mainly channeling milk ingestion), two hallmarks of Mammalia. Cetacean tongues are not involved in drinking, breathing, vocalizing, and other non-feeding activities; they evidently play no or little role in taste reception. Although cetaceans do not masticate or otherwise process food, their tongues retain key roles in food ingestion, transport, securing/positioning, and swallowing, though by different means than most mammals. This is due to cetaceans' aquatic habitat, which in turn altered their anatomy (e.g., the intranarial larynx and consequent soft palate alteration). Odontocetes ingest prey via raptorial biting or tongue-generated suction. Odontocete tongues expel water and possibly uncover benthic prey via hydraulic jetting. Mysticete tongues play crucial roles driving ram, suction, or lunge ingestion for filter feeding. The uniquely flaccid rorqual tongue, not a constant volume hydrostat (as in all other mammalian tongues), invaginates into a balloon-like pouch to temporarily hold engulfed water. Mysticete tongues also create hydrodynamic flow regimes and hydraulic forces for baleen filtration, and possibly for cleaning baleen. Cetacean tongues lost or modified much of the mobility and function of generic mammal tongues, but took on noteworthy morphological changes by evolving to accomplish new tasks.
Collapse
Affiliation(s)
- Alexander J Werth
- Department of Biology, Hampden-Sydney College, Hampden-Sydney, Virginia, USA
| | - A W Crompton
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts, USA
| |
Collapse
|
3
|
Valenzuela-Toro AM, Mehta R, Pyenson ND, Costa DP, Koch PL. Feeding morphology and body size shape resource partitioning in an eared seal community. Biol Lett 2023; 19:20220534. [PMID: 36883314 PMCID: PMC9993223 DOI: 10.1098/rsbl.2022.0534] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/09/2023] Open
Abstract
Body size and feeding morphology influence how animals partition themselves within communities. We tested the relationships among sex, body size, skull morphology and foraging in sympatric otariids (eared seals) from the eastern North Pacific Ocean, the most diverse otariid community in the world. We recorded skull measurements and stable carbon (δ13C) and nitrogen (δ15N) isotope values (proxies for foraging) from museum specimens in four sympatric species: California sea lions (Zalophus californianus), Steller sea lions (Eumetopias jubatus), northern fur seals (Callorhinus ursinus) and Guadalupe fur seals (Arctocephalus townsendi). Species and sexes had statistical differences in size, skull morphology and foraging significantly affecting the δ13C values. Sea lions had higher δ13C values than fur seals, and males of all species had higher values than females. The δ15N values were correlated with species and feeding morphology; individuals with stronger bite forces had higher δ15N values. We also found a significant community-wide correlation between skull length (indicator of body length), and foraging, with larger individuals having nearshore habitat preferences, and consuming higher trophic level prey than smaller individuals. Still, there was no consistent association between these traits at the intraspecific level, indicating that other factors might account for foraging variability.
Collapse
Affiliation(s)
- Ana M Valenzuela-Toro
- Department of Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, CA 95060, USA.,Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, DC 20560, USA
| | - Rita Mehta
- Department of Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, CA 95060, USA
| | - Nicholas D Pyenson
- Department of Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, CA 95060, USA.,Department of Paleontology and Geology, Burke Museum of Natural History and Culture, Seattle, WA 98105, USA
| | - Daniel P Costa
- Department of Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, CA 95060, USA.,Institute of Marine Sciences, University of California Santa Cruz, Santa Cruz, CA 95064, USA
| | - Paul L Koch
- Department of Earth and Planetary Sciences, University of California Santa Cruz, Santa Cruz, CA 95064, USA
| |
Collapse
|
4
|
Nourbakhsh H, Adams A, Raverty S, Vogl AW, Haulena M, Skoretz SA. Microscopic Anatomy of the Upper Aerodigestive Tract in Harbour Seals (Phoca vitulina): Functional Adaptations to Swallowing. Anat Rec (Hoboken) 2022; 306:947-959. [PMID: 35719006 DOI: 10.1002/ar.25025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Revised: 05/05/2022] [Accepted: 05/31/2022] [Indexed: 11/07/2022]
Abstract
Abandoned harbour seal pups (Phoca vitulina) are frequently recovered by rehabilitation centres and often require intensive nursing, gavage feeding and swallowing rehabilitation prior to anticipated release. Seal upper aerodigestive tract (UAT) histology descriptions relevant to deglutition are limited, impacting advances in rehabilitation practice. Therefore, we examined the histological characteristics of the harbour seal UAT to understand species-specific functional anatomy and characterize adaptations. To this end, we conducted gross dissections, compiled measurements and reviewed histologic features of the UAT structures of 14 pre-weaned harbour seal pups that died due to natural causes or were humanely euthanized. Representative samples for histologic evaluation included the tongue, salivary glands, epiglottis, and varying levels of the trachea and esophagus. Histologically, there was a prominent muscularis in the tongue with fewer lingual papillae types compared to humans. Abundant submucosal glands were observed in lateral and pharyngeal parts of the tongue and rostral parts of the esophagus. When compared to other mammalian species, there was a disproportionate increase in the amount of striated muscle throughout the length of the esophageal muscularis externa. This may indicate a lesser degree of autonomic control over the esophageal phase of swallowing in harbour seals. Our study represents the first detailed UAT histological descriptions for neonatal harbour seals. Collectively, these findings support specific anatomic and biomechanic adaptations relevant to suckling, prehension and deglutition. This work will inform rehabilitation practices and guide future studies on swallowing physiology in harbour seals with potential applications to other pinniped and otariid species in rehabilitation settings. This article is protected by copyright. All rights reserved.
Collapse
Affiliation(s)
- Hirad Nourbakhsh
- School of Audiology & Speech Sciences, University of British Columbia, Vancouver, BC
| | - Arlo Adams
- Life Sciences Institute & Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC
| | - Stephen Raverty
- Animal Health Center, 1767 Angus Campbell Road, Abbotsford, BC
| | - A Wayne Vogl
- Life Sciences Institute & Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, BC
| | - Martin Haulena
- Vancouver Aquarium Marine Mammal Rescue Centre, Vancouver, BC
| | - Stacey A Skoretz
- School of Audiology & Speech Sciences, University of British Columbia, Vancouver, BC.,Department of Critical Care Medicine, University of Alberta, Edmonton, AB
| |
Collapse
|
5
|
Milne AO, Muchlinski MN, Orton LD, Sullivan MS, Grant RA. Comparing vibrissal morphology and infraorbital foramen area in pinnipeds. Anat Rec (Hoboken) 2021; 305:556-567. [PMID: 34076956 DOI: 10.1002/ar.24683] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Revised: 03/30/2021] [Accepted: 04/21/2021] [Indexed: 12/15/2022]
Abstract
Pinniped vibrissae are well-adapted to sensing in an aquatic environment, by being morphologically diverse and more sensitive than those of terrestrial species. However, it is both challenging and time-consuming to measure vibrissal sensitivity in many species. In terrestrial species, the infraorbital foramen (IOF) area is associated with vibrissal sensitivity and increases with vibrissal number. While pinnipeds are thought to have large IOF areas, this has not yet been systematically measured before. We investigated vibrissal morphology, IOF area, and skull size in 16 species of pinniped and 12 terrestrial Carnivora species. Pinnipeds had significantly larger skulls and IOF areas, longer vibrissae, and fewer vibrissae than the other Carnivora species. IOF area and vibrissal number were correlated in Pinnipeds, just as they are in terrestrial mammals. However, despite pinnipeds having significantly fewer vibrissae than other Carnivora species, their IOF area was not smaller, which might be due to pinnipeds having vibrissae that are innervated more. We propose that investigating normalized IOF area per vibrissa will offer an alternative way to approximate gross individual vibrissal sensitivity in pinnipeds and other mammalian species. Our data show that many species of pinniped, and some species of felids, are likely to have strongly innervated individual vibrissae, since they have high values of normalized IOF area per vibrissa. We suggest that species that hunt moving prey items in the dark will have more sensitive and specialized vibrissae, especially as they have to integrate between individual vibrissal signals to calculate the direction of moving prey during hunting.
Collapse
Affiliation(s)
- Alyx O Milne
- Department of Natural Sciences, Manchester Metropolitan University, Manchester, UK.,Events Team, Blackpool Zoo, Blackpool, UK
| | | | - Llwyd D Orton
- Department of Life Sciences, Manchester Metropolitan University, Manchester, UK
| | - Matthew S Sullivan
- Department of Natural Sciences, Manchester Metropolitan University, Manchester, UK
| | - Robyn A Grant
- Department of Natural Sciences, Manchester Metropolitan University, Manchester, UK
| |
Collapse
|
6
|
Kane EA, Cohen HE, Hicks WR, Mahoney ER, Marshall CD. Beyond Suction-Feeding Fishes: Identifying New Approaches to Performance Integration During Prey Capture in Aquatic Vertebrates. Integr Comp Biol 2019; 59:456-472. [DOI: 10.1093/icb/icz094] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Abstract
Organisms are composed of hierarchically arranged component parts that must work together to successfully achieve whole organism functions. In addition to integration among individual parts, some ecological demands require functional systems to work together in a type of inter-system performance integration. While performance can be measured by the ability to successfully accomplish ecologically relevant tasks, integration across performance traits can provide a deeper understanding of how these traits allow an organism to survive. The ability to move and the ability to consume food are essential to life, but during prey capture these two functions are typically integrated. Suction-feeding fishes have been used as a model of these interactions, but it is unclear how other ecologically relevant scenarios might reduce or change integration. To stimulate further research into these ideas, we highlight three contexts with the potential to result in changes in integration and underlying performance traits: (1) behavioral flexibility in aquatic feeding modes for capturing alternative prey types, (2) changes in the physical demands imposed by prey capture across environments, and (3) secondary adaptation for suction prey capture behaviors. These examples provide a broad scope of potential drivers of integration that are relevant to selection pressures experienced across vertebrate evolution. To demonstrate how these ideas can be applied and stimulate hypotheses, we provide observations from preliminary analyses of locally adapted populations of Trinidadian guppies (Poecilia reticulata) capturing prey using suction and biting feeding strategies and an Atlantic mudskipper (Periophthalmus barbarus) capturing prey above and below water. We also include a re-analysis of published data from two species of secondarily aquatic cetaceans, beluga whales (Delphinapterus leucas) and Pacific white-sided dolphins (Lagenorhynchus obliquidens), to examine the potential for secondary adaptation to affect integration in suction prey capture behaviors. Each of these examples support the broad importance of integration between locomotor and feeding performance but outline new ways that these relationships can be important when suction demands are reduced or altered. Future work in these areas will yield promising insights into vertebrate evolution and we hope to encourage further discussion on possible avenues of research on functional integration during prey capture.
Collapse
Affiliation(s)
- Emily A Kane
- Department of Biology, Georgia Southern University, Statesboro, GA, USA
| | - Hannah E Cohen
- Department of Biology, Georgia Southern University, Statesboro, GA, USA
| | - William R Hicks
- Department of Biology, Georgia Southern University, Statesboro, GA, USA
| | - Emily R Mahoney
- Department of Biology, Georgia Southern University, Statesboro, GA, USA
| | - Christopher D Marshall
- Department of Marine Biology, Texas A&M University at Galveston, Galveston, TX, USA
- Department of Wildlife and Fisheries Sciences, Texas A&M University, College Station, TX, USA
| |
Collapse
|
7
|
Jones A, Marshall CD. Does Vibrissal Innervation Patterns and Investment Predict Hydrodynamic Trail Following Behavior of Harbor Seals (
Phoca vitulina
)? Anat Rec (Hoboken) 2019; 302:1837-1845. [DOI: 10.1002/ar.24134] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Revised: 11/07/2018] [Accepted: 12/09/2018] [Indexed: 12/12/2022]
Affiliation(s)
- Aubree Jones
- Department of Marine BiologyTexas A&M University Galveston Campus Galveston, Texas
| | - Christopher D. Marshall
- Department of Marine BiologyTexas A&M University Galveston Campus Galveston, Texas
- Department of Wildlife and Fisheries SciencesTexas A&M University College Station Texas
| |
Collapse
|
8
|
Kienle SS, Cacanindin A, Kendall T, Richter B, Ribeiro-French C, Castle L, Lentes G, Costa DP, Mehta RS. Hawaiian monk seals exhibit behavioral flexibility when targeting prey of different size and shape. ACTA ACUST UNITED AC 2019; 222:jeb.194985. [PMID: 30679244 DOI: 10.1242/jeb.194985] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Accepted: 01/17/2019] [Indexed: 11/20/2022]
Abstract
Animals use diverse feeding strategies to capture and consume prey, with many species switching between strategies to accommodate different prey. Many marine animals exhibit behavioral flexibility when feeding to deal with spatial and temporal heterogeneity in prey resources. However, little is known about flexibility in the feeding behavior of many large marine predators. Here, we documented the feeding behavior and kinematics of the endangered Hawaiian monk seal (Neomonachus schauinslandi, n=7) through controlled feeding trials. Seals were fed multiple prey types (e.g. night smelt, capelin, squid and herring) that varied in size and shape to examine behavioral flexibility in feeding. Hawaiian monk seals primarily used suction feeding (91% of all feeding trials) across all prey types, but biting, specifically pierce feeding, was also observed (9% of all feeding trials). Suction feeding was characterized by shorter temporal events, a smaller maximum gape and gape angle, and a fewer number of jaw motions than pierce feeding; suction feeding kinematic performance was also more variable compared with pierce feeding. Seals showed behavioral flexibility in their use of the two strategies. Suction feeding was used most frequently when targeting small to medium sized prey and biting was used with increasing frequency on larger prey. The feeding kinematics differed between feeding strategies and prey types, showing that Hawaiian monk seals adjusted their behaviors to particular feeding contexts. Hawaiian monk seals are opportunistic marine predators and their ability to adapt their feeding strategy and behavior to specific foraging scenarios allows them to target diverse prey resources.
Collapse
Affiliation(s)
- Sarah S Kienle
- Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, Ecology and Evolutionary Biology, Santa Cruz, CA 95060, USA
| | - Aliya Cacanindin
- Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, Ecology and Evolutionary Biology, Santa Cruz, CA 95060, USA
| | - Traci Kendall
- Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, Ecology and Evolutionary Biology, Santa Cruz, CA 95060, USA
| | - Beau Richter
- Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, Ecology and Evolutionary Biology, Santa Cruz, CA 95060, USA
| | - Courtney Ribeiro-French
- Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, Ecology and Evolutionary Biology, Santa Cruz, CA 95060, USA.,Monterey Bay Aquarium, Monterey, CA 93940, USA
| | - Leann Castle
- University of Hawai'i at Manoa, Waikiki Aquarium, Honolulu, HI 96815, USA
| | - Gwen Lentes
- University of Hawai'i at Manoa, Waikiki Aquarium, Honolulu, HI 96815, USA
| | - Daniel P Costa
- Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, Ecology and Evolutionary Biology, Santa Cruz, CA 95060, USA
| | - Rita S Mehta
- Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, Ecology and Evolutionary Biology, Santa Cruz, CA 95060, USA
| |
Collapse
|
9
|
Hocking DP, Marx FG, Park T, Fitzgerald EMG, Evans AR. A behavioural framework for the evolution of feeding in predatory aquatic mammals. Proc Biol Sci 2018; 284:rspb.2016.2750. [PMID: 28250183 DOI: 10.1098/rspb.2016.2750] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Accepted: 02/09/2017] [Indexed: 11/12/2022] Open
Abstract
Extant aquatic mammals are a key component of aquatic ecosystems. Their morphology, ecological role and behaviour are, to a large extent, shaped by their feeding ecology. Nevertheless, the nature of this crucial aspect of their biology is often oversimplified and, consequently, misinterpreted. Here, we introduce a new framework that categorizes the feeding cycle of predatory aquatic mammals into four distinct functional stages (prey capture, manipulation and processing, water removal and swallowing), and details the feeding behaviours that can be employed at each stage. Based on this comprehensive scheme, we propose that the feeding strategies of living aquatic mammals form an evolutionary sequence that recalls the land-to-water transition of their ancestors. Our new conception helps to explain and predict the origin of particular feeding styles, such as baleen-assisted filter feeding in whales and raptorial 'pierce' feeding in pinnipeds, and informs the structure of present and past ecosystems.
Collapse
Affiliation(s)
- David P Hocking
- School of Biological Sciences, Monash University, Clayton, Victoria 3800, Australia .,Geosciences, Museums Victoria, Melbourne, Australia
| | - Felix G Marx
- School of Biological Sciences, Monash University, Clayton, Victoria 3800, Australia.,Geosciences, Museums Victoria, Melbourne, Australia.,Directorate of Earth and History of Life, Royal Belgian Institute of Natural Sciences, Brussels, Belgium
| | - Travis Park
- School of Biological Sciences, Monash University, Clayton, Victoria 3800, Australia.,Geosciences, Museums Victoria, Melbourne, Australia
| | - Erich M G Fitzgerald
- Geosciences, Museums Victoria, Melbourne, Australia.,National Museum of Natural History, Smithsonian Institution, Washington, DC, USA.,Department of Life Sciences, Natural History Museum, London, UK
| | - Alistair R Evans
- School of Biological Sciences, Monash University, Clayton, Victoria 3800, Australia.,Geosciences, Museums Victoria, Melbourne, Australia
| |
Collapse
|
10
|
Kienle SS, Hermann-Sorensen H, Costa DP, Reichmuth C, Mehta RS. Comparative feeding strategies and kinematics in phocid seals: suction without specialized skull morphology. J Exp Biol 2018; 221:jeb.179424. [DOI: 10.1242/jeb.179424] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Accepted: 06/04/2018] [Indexed: 12/12/2022]
Abstract
Feeding kinematic studies inform our understanding of behavioral diversity and provide a framework for studying the flexibility and constraints of different prey acquisition strategies. However, little is known about the feeding behaviors used by many marine mammals. We characterized the feeding behaviors and associated kinematics of captive bearded (Erignathus barbatus), harbor (Phoca vitulina), ringed (Pusa hispida), and spotted (Phoca largha) seals through controlled feeding trials. All species primarily used a suction feeding strategy but were also observed using a biting strategy, specifically pierce feeding. Suction feeding was distinct from pierce feeding and was characterized by significantly faster feeding times, smaller gape and gape angles, smaller gular depressions, and fewer jaw motions. Most species showed higher variability in suction feeding performance than pierce feeding, indicating that suction feeding is a behaviorally flexible strategy. Bearded seals were the only species for which there was strong correspondence between skull and dental morphology and feeding strategy, providing further support for their classification as suction feeding specialists. Harbor, ringed, and spotted seals have been classified as pierce feeders based on skull and dental morphologies. Our behavioral and kinematic analyses show that suction feeding is also an important feeding strategy for these species, indicating that skull morphology alone does not capture the true diversity of feeding behaviors used by pinnipeds. The ability of all four species to use more than one feeding strategy is likely advantageous for foraging in spatially and temporally dynamic marine ecosystems that favor opportunistic predators.
Collapse
Affiliation(s)
- Sarah S. Kienle
- University of California, Santa Cruz, Ecology and Evolutionary Biology, Santa Cruz, CA 95060, USA
| | - Holly Hermann-Sorensen
- University of California, Santa Cruz, Ecology and Evolutionary Biology, Santa Cruz, CA 95060, USA
| | - Daniel P. Costa
- University of California, Santa Cruz, Ecology and Evolutionary Biology, Santa Cruz, CA 95060, USA
| | - Colleen Reichmuth
- University of California, Santa Cruz, Institute of Marine Sciences, Santa Cruz, CA 95060, USA
| | - Rita S. Mehta
- University of California, Santa Cruz, Ecology and Evolutionary Biology, Santa Cruz, CA 95060, USA
| |
Collapse
|
11
|
Timm-Davis LL, Davis RW, Marshall CD. Durophagous biting in sea otters (Enhydra lutris) differs kinematically from raptorial biting of other marine mammals. J Exp Biol 2017; 220:4703-4710. [DOI: 10.1242/jeb.162966] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Accepted: 10/24/2017] [Indexed: 01/07/2023]
Abstract
Sea otters represent an interesting model for studies of mammalian feeding evolution. Although they are marine mammals, sea otters returned to the sea relatively recently and feed at the surface. Therefore, they represent a transitional stage of aquatic adaptation. Currently no feeding performance studies of sea otters have been conducted. The main objective of this study was to characterize the feeding kinematic profile in sea otters. It was hypothesized that sea otters would exhibit a terrestrial feeding behavior and that they forcefully crush hard prey at large gapes. As a result, biting kinematics would be congruent with biting behavior reported for their terrestrial ancestors, thus providing additional evidence that raptorial biting is a conserved behavior even in recently aquatic mammals. Sea otters consistently used a durophagous raptorial biting mode characterized by large gapes, large gape angles, and lack of lateral gape occlusion. The shorter skulls and mandibles of sea otters, along with increased mechanical advantages of the masseter and increased bite force, form a repertoire of functional traits for durophagy. Here we consider durophagy to be a specialized raptorial biting feeding mode. A comparison of feeding kinematics of wild vs captive sea otters showed no significant differences in lateral kinematic profiles and only minor differences in three frontal kinematic profiles, which included a slower maximum opening gape velocity, a slower maximum gape opening velocity, and a slower maximum closing gape velocity in captive sea otters. Data indicate functional innovations for producing large bite forces at wide gape and gape angles.
Collapse
Affiliation(s)
- Lori L. Timm-Davis
- Department of Wildlife and Fisheries Sciences, Texas A&M University, College Station, TX 77843, USA
- Department of Marine Biology, Texas A&M University, 200 Seawolf Parkway, OCSB, Galveston, TX 77553, USA
| | - Randall W. Davis
- Department of Wildlife and Fisheries Sciences, Texas A&M University, College Station, TX 77843, USA
- Department of Marine Biology, Texas A&M University, 200 Seawolf Parkway, OCSB, Galveston, TX 77553, USA
| | - Christopher D. Marshall
- Department of Wildlife and Fisheries Sciences, Texas A&M University, College Station, TX 77843, USA
- Department of Marine Biology, Texas A&M University, 200 Seawolf Parkway, OCSB, Galveston, TX 77553, USA
| |
Collapse
|
12
|
Mattson EE, Marshall CD. Follicle Microstructure and Innervation Vary between Pinniped Micro- and Macrovibrissae. BRAIN, BEHAVIOR AND EVOLUTION 2016; 88:43-58. [DOI: 10.1159/000447551] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Accepted: 06/10/2016] [Indexed: 11/19/2022]
Abstract
Histological data from terrestrial, semiaquatic, and fully aquatic mammal vibrissa (whisker) studies indicate that follicle microstructure and innervation vary across the mystacial vibrissal array (i.e. medial microvibrissae to lateral macrovibrissae). However, comparative data are lacking, and current histological studies on pinniped vibrissae only focus on the largest ventrolateral vibrissae. Consequently, we investigated the microstructure, medial-to-lateral innervation, and morphometric trends in harp seal (Pagophilus groenlandicus) vibrissal follicle-sinus complexes (F-SCs). The F-SCs were sectioned either longitudinally or in cross-section and stained with a modified Masson's trichrome stain (microstructure) or Bodian's silver stain (innervation). All F-SCs exhibited a tripartite blood organization system. The dermal capsule thickness, the distribution of major branches of the deep vibrissal nerve, and the hair shaft design were more symmetrical in medial F-SCs, but these features became more asymmetrical as the F-SCs became more lateral. Overall, the mean axon count was 1,221 ± 422.3 axons/F-SC and mean axon counts by column ranged from 550 ± 97.4 axons/F-SC (medially, column 11) to 1,632 ± 173.2 axons/F-SC (laterally, column 2). These values indicate a total of 117,216 axons innervating the entire mystacial vibrissal array. The mean axon count of lateral F-SCs was 1,533 ± 192.9 axons/ F-SC, which is similar to values reported in the literature for other pinniped F-SCs. Our data suggest that conventional studies that only examine the largest ventrolateral vibrissae may overestimate the total innervation by ∼20%. However, our study also accounts for variation in quantification methods and shows that conventional analyses likely only overestimate innervation by ∼10%. The relationship between axon count and cross-sectional F-SC surface area was nonlinear, and axon densities were consistent across the snout. Our data indicate that harp seals exhibit microstructural and innervational differences between their microvibrissae (columns 8-11) and macrovibrissae (columns 1-7). We hypothesize that this feature is conserved among pinnipeds and may result in functional compartmentalization within their mystacial vibrissal arrays.
Collapse
|
13
|
Marshall CD. Morphology of the Bearded Seal (Erignathus barbatus) Muscular-Vibrissal Complex: A Functional Model for Phocid Subambient Pressure Generation. Anat Rec (Hoboken) 2016; 299:1043-53. [DOI: 10.1002/ar.23377] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Revised: 02/01/2016] [Accepted: 04/15/2016] [Indexed: 12/23/2022]
Affiliation(s)
- Christopher D. Marshall
- Department of Marine Biology; Texas A&M University; Texas
- Department of Wildlife and Fisheries Biology; Texas A&M University; Texas
| |
Collapse
|
14
|
Loch C, Boessenecker RW, Churchill M, Kieser J. Enamel ultrastructure of fossil and modern pinnipeds: evaluating hypotheses of feeding adaptations in the extinct walrus Pelagiarctos. Naturwissenschaften 2016; 103:44. [DOI: 10.1007/s00114-016-1366-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Revised: 04/12/2016] [Accepted: 04/15/2016] [Indexed: 01/05/2023]
|