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Cervino NG, Elias-Costa AJ, Pereyra MO, Faivovich J. A closer look at pupil diversity and evolution in frogs and toads. Proc Biol Sci 2021; 288:20211402. [PMID: 34403634 PMCID: PMC8370803 DOI: 10.1098/rspb.2021.1402] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Accepted: 07/23/2021] [Indexed: 11/12/2022] Open
Abstract
The eyes of frogs and toads (Anura) are among their most fascinating features. Although several pupil shapes have been described, the diversity, evolution, and functional role of the pupil in anurans have received little attention. Studying photographs of more than 3200 species, we surveyed pupil diversity, described their morphological variation, tested correlation with adult habits and diel activity, and discuss major evolutionary patterns considering iris anatomy and visual ecology. Our results indicate that the pupil in anurans is a highly plastic structure, with seven main pupil shapes that evolved at least 116 times during the history of the group. We found no significant correlation between pupil shape, adult habits, and diel activity, with the exception of the circular pupil and aquatic habits. The vertical pupil arose at least in the most-recent common ancestor of Anura + Caudata, and this morphology is present in most early-diverging anuran clades. Subsequently, a horizontal pupil, a very uncommon shape in vertebrates, evolved in most neobatrachian frogs. This shape evolved into most other known pupil shapes, but it persisted in a large number of species with diverse life histories, habits, and diel activity patterns, demonstrating a remarkable functional and ecological versatility.
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Affiliation(s)
- Nadia G. Cervino
- División Herpetología, Museo Argentino de Ciencias Naturales ‘Bernardino Rivadavia’ – CONICET, Av. Ángel Gallardo 470, Buenos Aires C1405DJR, Argentina
| | - Agustín J. Elias-Costa
- División Herpetología, Museo Argentino de Ciencias Naturales ‘Bernardino Rivadavia’ – CONICET, Av. Ángel Gallardo 470, Buenos Aires C1405DJR, Argentina
| | - Martín O. Pereyra
- Laboratorio de Genética Evolutiva ‘Claudio J. Bidau’, Instituto de Biología Subtropical (IBS, CONICET), Universidad Nacional de Misiones (UNaM), Posadas, Misiones, Argentina
| | - Julián Faivovich
- División Herpetología, Museo Argentino de Ciencias Naturales ‘Bernardino Rivadavia’ – CONICET, Av. Ángel Gallardo 470, Buenos Aires C1405DJR, Argentina
- Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, C1428EGA, Argentina
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Leslie CE, Walkowski W, Rosencrans RF, Gordon WC, Bazan NG, Ryan MJ, Farris HE. Estrogenic Modulation of Retinal Sensitivity in Reproductive Female Túngara Frogs. Integr Comp Biol 2021; 61:231-239. [PMID: 33901287 PMCID: PMC8300951 DOI: 10.1093/icb/icab032] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Although mate searching behavior in female túngara frogs (Physalaemus pustulosus) is nocturnal and largely mediated by acoustic cues, male signaling includes visual cues produced by the vocal sac. To compensate for these low light conditions, visual sensitivity in females is modulated when they are in a reproductive state, as retinal thresholds are decreased. This study tested whether estradiol (E2) plays a role in this modulation. Female túngara frogs were injected with either human chorionic gonadotropin (hCG) or a combination of hCG and fadrozole. hCG induces a reproductive state and increases retinal sensitivity, while fadrozole is an aromatase inhibitor that blocks hCG-induced E2 synthesis. In an analysis of scotopic electroretinograms (ERGs), hCG treatment lowered the threshold for eliciting a b-wave response, whereas the addition of fadrozole abolished this effect, matching thresholds in non-reproductive saline-injected controls. This suggests that blocking E2 synthesis blocked the hCG-mediated reproductive modulation of retinal sensitivity. By implicating E2 in control of retinal sensitivity, our data add to growing evidence that the targets of gonadal steroid feedback loops include sensory receptor organs, where stimulus sensitivity may be modulated, rather than more central brain nuclei, where modulation may affect mechanisms involved in motivation.
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Affiliation(s)
- Caitlin E Leslie
- Department of Integrative Biology, University of Texas, Austin, TX 78712, USA
| | - Whitney Walkowski
- Neuroscience Center, Louisiana State University School of Medicine, 2020 Gravier Street, New Orleans, LA 70112, USA.,Department of Cell Biology and Anatomy, Louisiana State University School of Medicine, New Orleans, LA 70112, USA
| | - Robert F Rosencrans
- Neuroscience Center, Louisiana State University School of Medicine, 2020 Gravier Street, New Orleans, LA 70112, USA
| | - William C Gordon
- Neuroscience Center, Louisiana State University School of Medicine, 2020 Gravier Street, New Orleans, LA 70112, USA.,Department of Ophthalmology, Louisiana State University School of Medicine, New Orleans, LA 70112, USA
| | - Nicolas G Bazan
- Neuroscience Center, Louisiana State University School of Medicine, 2020 Gravier Street, New Orleans, LA 70112, USA.,Department of Ophthalmology, Louisiana State University School of Medicine, New Orleans, LA 70112, USA
| | - Michael J Ryan
- Department of Integrative Biology, University of Texas, Austin, TX 78712, USA
| | - Hamilton E Farris
- Neuroscience Center, Louisiana State University School of Medicine, 2020 Gravier Street, New Orleans, LA 70112, USA.,Department of Cell Biology and Anatomy, Louisiana State University School of Medicine, New Orleans, LA 70112, USA.,Department of Otorhinolaryngology, Louisiana State University School of Medicine, New Orleans, LA 70112, USA
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3
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Zhu B, Zhou Y, Yang Y, Deng K, Wang T, Wang J, Tang Y, Ryan MJ, Cui J. Multisensory modalities increase working memory for mating signals in a treefrog. J Anim Ecol 2021; 90:1455-1465. [PMID: 33666233 DOI: 10.1111/1365-2656.13465] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Accepted: 02/17/2021] [Indexed: 12/21/2022]
Abstract
Animal choruses, such as those found in insects and frogs, are often intermittent. Thus, females sampling males in the chorus might have to remember the location of the potential mates' calls during periods of silence. Although a number of studies have shown that frogs use and prefer multimodal mating signals, usually acoustic plus visual, it is not clear why they do so. Here we tested the hypothesis that preference for multimodal signals over unimodal signals might be due to multimodal signals instantiating longer memories than unimodal signals, particularly during the inter-chorus intervals. We tested this hypothesis in serrate-legged small treefrogs Kurixalus odontotarsus whose males produce advertisement calls accompanied by conspicuous vocal sac inflation. Females were tested with acoustic and acoustic + visual (video of inflating-deflating vocal sac) mating calls. We found that females prefer multimodal calls over unimodal, audio-only calls. Furthermore, multimodal calls are still preferred after a silent period of up to 30 s, a time that spans the average silent period of the chorus. This was not true of unimodal calls. Our results demonstrate that a multimodal signal can engage longer working memory than a unimodal signal, and thus female memory might favour the evolution of multimodal signals in males through sexual selection. Selection might also favour female preference for multimodal signals if longer memory facilitates mate searching and assessment. Our study does not allow us to elucidate the sequence of evolution of this trait and preference.
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Affiliation(s)
- Bicheng Zhu
- Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, China
| | - Ya Zhou
- Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Yue Yang
- Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, China
| | - Ke Deng
- Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, China
| | - Tongliang Wang
- Ministry of Education Key Laboratory for Tropical Plant and Animal Ecology, College of Life Sciences, Hainan Normal University, Haikou, China
| | - Jichao Wang
- Ministry of Education Key Laboratory for Tropical Plant and Animal Ecology, College of Life Sciences, Hainan Normal University, Haikou, China
| | - Yezhong Tang
- Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, China
| | - Michael J Ryan
- Department of Integrative Biology, University of Texas, Austin, TX, USA
| | - Jianguo Cui
- Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, China
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4
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Donner K, Yovanovich CAM. A frog's eye view: Foundational revelations and future promises. Semin Cell Dev Biol 2020; 106:72-85. [PMID: 32466970 DOI: 10.1016/j.semcdb.2020.05.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2020] [Revised: 05/13/2020] [Accepted: 05/13/2020] [Indexed: 12/16/2022]
Abstract
From the mid-19th century until the 1980's, frogs and toads provided important research models for many fundamental questions in visual neuroscience. In the present century, they have been largely neglected. Yet they are animals with highly developed vision, a complex retina built on the basic vertebrate plan, an accessible brain, and an experimentally useful behavioural repertoire. They also offer a rich diversity of species and life histories on a reasonably restricted physiological and evolutionary background. We suggest that important insights may be gained from revisiting classical questions in anurans with state-of-the-art methods. At the input to the system, this especially concerns the molecular evolution of visual pigments and photoreceptors, at the output, the relation between retinal signals, brain processing and behavioural decision-making.
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Affiliation(s)
- Kristian Donner
- Molecular and Integrative Biosciences Research Program, Faculty of Biological and Environmental Sciences, University of Helsinki, Finland; PB 65 (Viikinkaari 1), 00014, University of Helsinki, Finland.
| | - Carola A M Yovanovich
- Department of Zoology, Institute of Biosciences, University of São Paulo, Brazil; Rua do Matão, Trav. 14, N°101, São Paulo, SP, 05508-090, Brazil.
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Leslie CE, Rosencrans RF, Walkowski W, Gordon WC, Bazan NG, Ryan MJ, Farris HE. Reproductive State Modulates Retinal Sensitivity to Light in Female Túngara Frogs. Front Behav Neurosci 2020; 13:293. [PMID: 32076402 PMCID: PMC6985269 DOI: 10.3389/fnbeh.2019.00293] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Accepted: 12/23/2019] [Indexed: 12/31/2022] Open
Abstract
Visual cues are often a vital part of animal communication and courtship. While a plethora of studies have focused on the role that hormones play in acoustic communication of anurans, relatively few have explored hormonal modulation of vision in these animals. Much of what we do know comes from behavioral studies, which show that a frog’s hormonal state can significantly affect both its visual behavior and mating decisions. However, to fully understand how frogs use visual cues to make these mating decisions, we must first understand how their visual system processes these cues, and how hormones affect these processes. To do this, we performed electroretinograms (ERGs) to measure retinal sensitivity of túngara frogs (Physalaemus pustulosus), a neotropical species whose mating behavior includes previously described visual cues. To determine the effect of hormonal state on visual sensitivity, ERGs were recorded under scotopic and photopic conditions in frogs that were either non-reproductive or hormone-treated with human chorionic gonadotropin (hCG) prior to testing. Additionally, measurements of optical anatomy determined how túngara frog eye and retina morphology related to physiological sensitivity. As expected, we found that both sexes display higher visual sensitivity under scotopic conditions compared to photopic conditions. However, hormone injections significantly increased retinal sensitivity of females under scotopic conditions. These results support the hypothesis that hormonal modulation of neural mechanisms, such as those mediating visually guided reproductive behavior in this species, include modulation of the receptor organ: the retina. Thus, our data serve as a starting point for elucidating the mechanism of hormonal modulation of visual sensitivity.
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Affiliation(s)
- Caitlin E Leslie
- Department of Integrative Biology, The University of Texas at Austin, Austin, TX, United States
| | - Robert F Rosencrans
- Neuroscience Center, Louisiana State University School of Medicine, New Orleans, LA, United States
| | - Whitney Walkowski
- Neuroscience Center, Louisiana State University School of Medicine, New Orleans, LA, United States.,Department of Cell Biology and Anatomy, Louisiana State University School of Medicine, New Orleans, LA, United States
| | - William C Gordon
- Neuroscience Center, Louisiana State University School of Medicine, New Orleans, LA, United States.,Department of Ophthalmology, Louisiana State University School of Medicine, New Orleans, LA, United States
| | - Nicolas G Bazan
- Neuroscience Center, Louisiana State University School of Medicine, New Orleans, LA, United States.,Department of Ophthalmology, Louisiana State University School of Medicine, New Orleans, LA, United States
| | - Michael J Ryan
- Department of Integrative Biology, The University of Texas at Austin, Austin, TX, United States.,Smithsonian Tropical Research Institute, Balboa, Panama
| | - Hamilton E Farris
- Neuroscience Center, Louisiana State University School of Medicine, New Orleans, LA, United States.,Department of Cell Biology and Anatomy, Louisiana State University School of Medicine, New Orleans, LA, United States.,Department of Otorhinolaryngology, Louisiana State University School of Medicine, New Orleans, LA, United States
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