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Stynoski JL, Womack MC, Trama FA, Coloma LA, Hoke KL. Whispers from vestigial nubbins: Arrested development provokes trait loss in toads. Evol Dev 2020; 23:5-18. [PMID: 33107688 DOI: 10.1111/ede.12356] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Revised: 09/21/2020] [Accepted: 09/28/2020] [Indexed: 12/29/2022]
Abstract
Despite the use of acoustic communication, many species of toads (family Bufonidae) have lost parts of the tympanic middle ear, representing at least 12 independent evolutionary occurrences of trait loss. The comparative development of the tympanic middle ear in toads is poorly understood. Here, we compared middle ear development among two pairs of closely related toad species in the genera Atelopus and Rhinella that have (eared) or lack (earless) middle ear structures. We bred toads in Peru and Ecuador, preserved developmental series from tadpoles to juveniles, and examined ontogenetic timing and volume of the otic capsule, oval window, operculum, opercularis muscle, columella (stapes), and extracolumella in three-dimensional histological reconstructions. All species had similar ontogenesis of the otic capsule, oval window, operculum, and opercularis muscle. Moreover, cell clusters of primordial columella in the oval window appeared just before metamorphosis in both eared and earless lineages. However, in earless lineages, the cell clusters either remained as small nubbins or cell buds in the location of the columella footplate within the oval window or disappeared by juvenile and adult stages. Thus, columella growth began around metamorphosis in all species but was truncated and/or degenerated after metamorphosis in earless species, leaving earless adults with morphology typical of metamorphic anurans. Shifts in the timing or expression of biochemical pathways that regulate the extension or differentiation of the columella after metamorphosis may be the developmental mechanism underlying convergent trait loss among toad lineages.
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Affiliation(s)
- Jennifer L Stynoski
- Department of Biology, Colorado State University, Fort Collins, Colorado, USA.,Instituto Clodomiro Picado, Universidad de Costa Rica, Coronado, Costa Rica
| | - Molly C Womack
- Department of Biology, Colorado State University, Fort Collins, Colorado, USA.,Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, DC, USA
| | - Florencia A Trama
- Grupo de Investigación en Entomología y Medio Ambiente, Universidad San Ignacio de Loyola, Lima, Peru.,Centro de Capacitación en Conservación y Desarrollo Sostenible (CDS/CNEH-Perú), Oxapampa, Peru
| | - Luis A Coloma
- Centro Jambatu de Investigación y Conservación de Anfibios, Fundación Jambatu, Quito, Ecuador
| | - Kim L Hoke
- Department of Biology, Colorado State University, Fort Collins, Colorado, USA
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Simmons AM. Tadpole bioacoustics: Sound processing across metamorphosis. Behav Neurosci 2019; 133:586-601. [PMID: 31448929 DOI: 10.1037/bne0000340] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Many species of anuran amphibians (frogs and toads) undergo metamorphosis, a developmental process during which external and internal body morphologies transform dramatically as the animal transitions to a new ecosystem (from aquatic to terrestrial) and develops new behavior patterns (from filter-feeding to active pursuit of moving prey; from mostly mute to highly vocal). All sensory systems transform to some extent during metamorphosis, even in those "primitive" anuran species that remain fully aquatic in adult life. In this article, I review what is known about the development of the auditory system in anuran tadpoles. I identify crucial developmental windows for major maturational events in the ear and brainstem that showcase the structural and physiological reorganization of the substrates for hearing airborne sounds as the animal navigates the metamorphic transition. I argue that auditory development is dynamic and nonlinear, and I point out areas for future investigation. Understanding metamorphosis can shed light on how organisms adapt to major environmental challenges. (PsycINFO Database Record (c) 2019 APA, all rights reserved).
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Womack MC, Stynoski JL, Voyles MK, Coloma LA, Hoke KL. Prolonged middle ear development in Rhinella horribilis. J Morphol 2018; 279:1518-1523. [PMID: 30152036 DOI: 10.1002/jmor.20886] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Revised: 07/12/2018] [Accepted: 07/20/2018] [Indexed: 11/07/2022]
Abstract
Despite the benefit of the tympanic middle ear to airborne hearing sensitivity, anurans range in how soon they develop functional middle ears after transitioning to life on land. Previous evidence suggested that bufonids had particularly slow middle ear developmental rates, but precise timelines have not yet been published for this family. Here, we provide the first age-verified middle ear development timeline for a true toad species (family Bufonidae). We find that although middle ear development begins during metamorphosis in Rhinella horribilis, the middle ear remains incomplete 15 weeks after the transition from aquatic tadpole to land-dwelling toadlet. Using this new middle ear timeline, we discuss commonalities and differences in middle ear development among bufonids, as well as among Anura.
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Affiliation(s)
- Molly C Womack
- Department of Biology, Colorado State University, Fort Collins, Colorado
| | - Jennifer L Stynoski
- Department of Biology, Colorado State University, Fort Collins, Colorado.,Instituto Clodomiro Picado, Universidad de Costa Rica, San José, Costa Rica
| | - Meredith K Voyles
- Department of Biology, Colorado State University, Fort Collins, Colorado
| | - Luis A Coloma
- Centro Jambatu de Investigación y Conservación de Anfibios, Fundación Otonga, San Rafael, Quito, Ecuador
| | - Kim L Hoke
- Department of Biology, Colorado State University, Fort Collins, Colorado
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Womack MC, Christensen-Dalsgaard J, Coloma LA, Hoke KL. Sensitive high-frequency hearing in earless and partially eared harlequin frogs ( Atelopus). ACTA ACUST UNITED AC 2018; 221:jeb.169664. [PMID: 29674377 DOI: 10.1242/jeb.169664] [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: 09/08/2017] [Accepted: 04/11/2018] [Indexed: 11/20/2022]
Abstract
Harlequin frogs, genus Atelopus, communicate at high frequencies despite most species lacking a complete tympanic middle ear that facilitates high-frequency hearing in most anurans and other tetrapods. Here, we tested whether Atelopus are better at sensing high-frequency acoustic sound compared with other eared and earless species in the Bufonidae family, determined whether middle ear variation within Atelopus affects hearing sensitivity and tested potential hearing mechanisms in Atelopus We determined that at high frequencies (2000-4000 Hz), Atelopus are 10-34 dB more sensitive than other earless bufonids but are relatively insensitive to mid-range frequencies (900-1500 Hz) compared with eared bufonids. Hearing among Atelopus species is fairly consistent, evidence that the partial middle ears present in a subset of Atelopus species do not convey a substantial hearing advantage. We further demonstrate that Atelopus hearing is probably not facilitated by vibration of the skin overlying the normal tympanic membrane region or the body lung wall, leaving the extratympanic hearing pathways in Atelopus enigmatic. Together, these results show Atelopus have sensitive high-frequency hearing without the aid of a tympanic middle ear and prompt further study of extratympanic hearing mechanisms in anurans.
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Affiliation(s)
- Molly C Womack
- Department of Biology, Colorado State University, Fort Collins, CO 80523, USA
| | | | - Luis A Coloma
- Centro Jambatu de Investigación y Conservación de Anfibios, Fundación Otonga, Giovanni Farina 566 y Baltra, San Rafael, Quito, Ecuador
| | - Kim L Hoke
- Department of Biology, Colorado State University, Fort Collins, CO 80523, USA
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Womack MC, Christensen-Dalsgaard J, Coloma LA, Chaparro JC, Hoke KL. Earless toads sense low frequencies but miss the high notes. Proc Biol Sci 2018; 284:rspb.2017.1670. [PMID: 28978737 DOI: 10.1098/rspb.2017.1670] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Accepted: 09/04/2017] [Indexed: 01/01/2023] Open
Abstract
Sensory losses or reductions are frequently attributed to relaxed selection. However, anuran species have lost tympanic middle ears many times, despite anurans' use of acoustic communication and the benefit of middle ears for hearing airborne sound. Here we determine whether pre-existing alternative sensory pathways enable anurans lacking tympanic middle ears (termed earless anurans) to hear airborne sound as well as eared species or to better sense vibrations in the environment. We used auditory brainstem recordings to compare hearing and vibrational sensitivity among 10 species (six eared, four earless) within the Neotropical true toad family (Bufonidae). We found that species lacking middle ears are less sensitive to high-frequency sounds, however, low-frequency hearing and vibrational sensitivity are equivalent between eared and earless species. Furthermore, extratympanic hearing sensitivity varies among earless species, highlighting potential species differences in extratympanic hearing mechanisms. We argue that ancestral bufonids may have sufficient extratympanic hearing and vibrational sensitivity such that earless lineages tolerated the loss of high frequency hearing sensitivity by adopting species-specific behavioural strategies to detect conspecifics, predators and prey.
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Affiliation(s)
- Molly C Womack
- Department of Biology, Colorado State University, Fort Collins, CO, USA
| | | | - Luis A Coloma
- Centro Jambatu de Investigación y Conservación de Anfibios, Fundación Otonga, Giovanni Farina 566 y Baltra, San Rafael, Quito, Ecuador.,Universidad Regional Amazónica Ikiam, Muyuna, Tena, Ecuador
| | - Juan C Chaparro
- Museo de Biodiversidad del Peru, Cusco, Peru.,Museo de Historia Natural de la Universidad Nacional de San Antonio Abad del Cusco, Cusco, Peru
| | - Kim L Hoke
- Department of Biology, Colorado State University, Fort Collins, CO, USA
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Goutte S, Mason MJ, Christensen-Dalsgaard J, Montealegre-Z F, Chivers BD, Sarria-S FA, Antoniazzi MM, Jared C, Almeida Sato L, Felipe Toledo L. Evidence of auditory insensitivity to vocalization frequencies in two frogs. Sci Rep 2017; 7:12121. [PMID: 28935936 PMCID: PMC5608807 DOI: 10.1038/s41598-017-12145-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Accepted: 09/04/2017] [Indexed: 11/14/2022] Open
Abstract
The emergence and maintenance of animal communication systems requires the co-evolution of signal and receiver. Frogs and toads rely heavily on acoustic communication for coordinating reproduction and typically have ears tuned to the dominant frequency of their vocalizations, allowing discrimination from background noise and heterospecific calls. However, we present here evidence that two anurans, Brachycephalus ephippium and B. pitanga, are insensitive to the sound of their own calls. Both species produce advertisement calls outside their hearing sensitivity range and their inner ears are partly undeveloped, which accounts for their lack of high-frequency sensitivity. If unheard by the intended receivers, calls are not beneficial to the emitter and should be selected against because of the costs associated with signal production. We suggest that protection against predators conferred by their high toxicity might help to explain why calling has not yet disappeared, and that visual communication may have replaced auditory in these colourful, diurnal frogs.
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Affiliation(s)
- Sandra Goutte
- Laboratório de História Natural de Anfíbios Brasileiros (LaHNAB), Departamento de Biologia Animal, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, São Paulo, 13083-862, Brazil.
| | - Matthew J Mason
- Department of Physiology, Development & Neuroscience, University of Cambridge, Downing Street, Cambridge, CB2 3EG, United Kingdom
| | | | - Fernando Montealegre-Z
- Bioacoustics and Sensory Biology Lab, School of Life Sciences, Joseph Banks Laboratories, University of Lincoln, Green Lane, Lincoln, LN6 7DL, United Kingdom
| | - Benedict D Chivers
- Bioacoustics and Sensory Biology Lab, School of Life Sciences, Joseph Banks Laboratories, University of Lincoln, Green Lane, Lincoln, LN6 7DL, United Kingdom
| | - Fabio A Sarria-S
- Bioacoustics and Sensory Biology Lab, School of Life Sciences, Joseph Banks Laboratories, University of Lincoln, Green Lane, Lincoln, LN6 7DL, United Kingdom
| | - Marta M Antoniazzi
- Laboratory of Cell Biology, Instituto Butantan, São Paulo, 05503-900, Brazil
| | - Carlos Jared
- Laboratory of Cell Biology, Instituto Butantan, São Paulo, 05503-900, Brazil
| | | | - Luís Felipe Toledo
- Laboratório de História Natural de Anfíbios Brasileiros (LaHNAB), Departamento de Biologia Animal, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, São Paulo, 13083-862, Brazil
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