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Berning D, Heerema H, Gross JB. The spatiotemporal and genetic architecture of extraoral taste buds in Astyanax cavefish. Commun Biol 2024; 7:951. [PMID: 39107459 PMCID: PMC11303775 DOI: 10.1038/s42003-024-06635-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2024] [Accepted: 07/26/2024] [Indexed: 08/10/2024] Open
Abstract
Intense environmental pressures can yield both regressive and constructive traits through complex evolutionary mechanisms. Although regression is well-studied, the biological bases of constructive features are less well understood. Cave-dwelling Astyanax fish harbor prolific extraoral taste buds on their heads, which are absent in conspecific surface-dwellers. Here, we present novel ontogenetic data demonstrating extraoral taste buds appear gradually and late in life history. This appearance is similar but non-identical in different cavefish populations, where patterning has evolved to permit taste bud re-specification across the endoderm-ectoderm germ layer boundary. Quantitative genetic analyses revealed that spatially distinct taste buds on the head are primarily mediated by two different cave-dominant loci. While the precise function of this late expansion on to the head is unknown, the appearance of extraoral taste buds coincides with a dietary shift from live-foods to bat guano, suggesting an adaptive mechanism to detect nutrition in food-starved caves. This work provides fundamental insight to a constructive evolutionary feature, arising late in life history, promising a new window into unresolved features of vertebrate sensory organ development.
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Affiliation(s)
- Daniel Berning
- Department of Biological Sciences, University of Cincinnati, Cincinnati, OH, USA
| | - Halle Heerema
- Department of Biological Sciences, University of Cincinnati, Cincinnati, OH, USA
| | - Joshua B Gross
- Department of Biological Sciences, University of Cincinnati, Cincinnati, OH, USA.
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2
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Polat H, Grande G, Aurangzeb Z, Zhang H, Daghfous G, Dubuc R, Zielinski B. The distribution and chemosensory responses of pharyngeal taste buds in the sea lamprey Petromyzon marinus. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2024:10.1007/s00359-024-01708-3. [PMID: 39078515 DOI: 10.1007/s00359-024-01708-3] [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: 03/30/2024] [Revised: 06/07/2024] [Accepted: 06/10/2024] [Indexed: 07/31/2024]
Abstract
Little is known about the chemosensory system of gustation in sea lampreys, basal jawless vertebrates that feed voraciously on live prey. The objective of this study was to investigate taste bud distribution and chemosensory responses along the length of the pharynx in the sea lamprey. Scanning electron microscopy and immunocytochemistry revealed taste buds and associated axons at all six lateral pharyngeal locations between the seven pairs of internal gill pores. The most rostral pharyngeal region contained more and larger taste buds than the most caudal region. Taste receptor cell responses were recorded to sweet, bitter, amino acids and the bile acid taurocholic acid, as well as to adenosine triphosphate. Similar chemosensory responses were observed at all six pharyngeal locations with taste buds. Overall, this study shows prominent taste buds and taste receptor cell activity in the seven pharyngeal regions of the sea lamprey.
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Affiliation(s)
- Hasan Polat
- Department of Integrative Biology, University of Windsor, Windsor, ON, Canada
| | - Gianfranco Grande
- Department of Integrative Biology, University of Windsor, Windsor, ON, Canada
| | - Zeenat Aurangzeb
- Department of Integrative Biology, University of Windsor, Windsor, ON, Canada
| | - Huiming Zhang
- Department of Biomedical Sciences, University of Windsor, Windsor, ON, Canada
| | - Gheylen Daghfous
- Groupe de Recherche en Activité Physique Adaptée, Département des Sciences de l'activité physique, Université du Québec à Montréal, Montréal, QC, Canada
- Department of Neurosciences, Université de Montréal, Montréal, QC, Canada
| | - Réjean Dubuc
- Groupe de Recherche en Activité Physique Adaptée, Département des Sciences de l'activité physique, Université du Québec à Montréal, Montréal, QC, Canada
- Department of Neurosciences, Université de Montréal, Montréal, QC, Canada
| | - Barbara Zielinski
- Department of Integrative Biology, University of Windsor, Windsor, ON, Canada.
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3
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Rizzato PP, Bichuette ME. Gross morphology of the brain and some sense organs of subterranean pencil catfishes of the genus Ituglanis Costa and Bockmann, 1993 (Siluriformes, Trichomycteridae), with a discussion on sensory compensation versus preadaptation in subterranean fishes. JOURNAL OF FISH BIOLOGY 2024; 104:1386-1400. [PMID: 38343097 DOI: 10.1111/jfb.15676] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Revised: 12/13/2023] [Accepted: 01/18/2024] [Indexed: 05/22/2024]
Abstract
Subterranean organisms provide excellent opportunities to investigate morphological evolution, especially of sensory organs and structures and their processing areas in the central nervous system. We describe the gross morphology of the brain and some cephalic sensory organs (olfactory organ, eye, semicircular canals of the inner ear) and the swim bladder (a non-sensory accessory structure) of subterranean species of pencil catfishes of the genus Ituglanis Costa and Bockmann, 1993 (Siluriformes, Trichomycteridae) and compare them with an epigean species of the genus, Ituglanis goya Datovo, Aquino and Langeani, 2016. We compared qualitatively the size of the different brain regions and sense organs of the subterranean species with those of the epigean one, searching for modifications possibly associated with living in the subterranean environment. Our findings suggest that species of Ituglanis exhibit sensory characteristics that are preadaptive for the subterranean life, as only slight modifications were observed in the brains and sense organs of the subterranean species of the genus when compared with the epigean one. Because most subterranean fish species belong to lineages putatively preadapted for subterranean life, our results, discussed in the context of available information on the brain and sense organs of other subterranean species, help identify general trends for the evolution of the brain and sensory organs of subterranean fishes in general.
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Affiliation(s)
- Pedro P Rizzato
- Laboratório de Morfologia, Evolução e Diversidade de Vertebrados, Departamento de Zoologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, Brazil
| | - Maria Elina Bichuette
- Laboratório de Estudos Subterrâneos and Instituto Nacional de Ciência e Tecnologia-Biodiversidade e uso Sustentável de Peixes Neotropicais (INCT Peixes), Universidade Federal de São Carlos, São Carlos, Brazil
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Ikenaga T, Nakamura T, Tajiri T, Tsuji M, Kato DI, Ineno T, Kobayashi Y, Tsutsui N, Kiyohara S. Diversity and evolution of serotonergic cells in taste buds of elasmobranchs and ancestral actinopterygian fish. Cell Tissue Res 2023; 394:431-439. [PMID: 37851111 DOI: 10.1007/s00441-023-03837-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2023] [Accepted: 10/05/2023] [Indexed: 10/19/2023]
Abstract
A subset of gustatory cells are serotonin immunoreactive (ir) in the mammalian taste bud. In the taste bud of lamprey, elongated gustatory-like cells are also serotonin-ir. In contrast, flattened serotonin-ir cells are located only in the basal region of the taste buds in the teleosts and amphibians. These serotonin-ir cells are termed as basal cells. To evaluate the evolution and diversity of serotonergic cells in the taste bud of amniote animals, we explored the distribution and morphology of serotonin-ir cells in the taste buds of ancestral actinopterygian fish (spotted gar, sturgeon, Polypterus senegalus) and elasmobranch (stingray). In all examined animals, the taste buds contained serotonin-ir cells in their basal part. The number of serotonin-ir basal cells in each taste bud was different between these fish species. They were highest in the stingray and decreased in the order of the Polypterus, sturgeon, and gar. While serotonin immunoreactivity was observed only in the basal cells in the taste buds of the ancestral actinopterygian fish, some elongated cells were also serotonin-ir in addition to the basal cells in the stingray taste buds. mRNA of tryptophan hydroxylase 1 (tph1), a rate-limiting enzyme of the serotonin synthesis, is expressed in both the elongated and basal cells of stingray taste buds, indicating that these cells synthesize the serotonin by themselves. These results suggest that the serotonin-ir basal cells arose from the ancestor of the cartilaginous fish, and serotonin-ir cells in the elasmobranch taste bud exhibit an intermediate aspect between the lamprey and actinopterygian fish.
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Affiliation(s)
- Takanori Ikenaga
- Graduate School of Science and Engineering, Kagoshima University, Kagoshima, 890-0065, Japan.
| | - Tastufumi Nakamura
- Graduate School of Science and Engineering, Kagoshima University, Kagoshima, 890-0065, Japan
| | - Tatsushi Tajiri
- Graduate School of Science and Engineering, Kagoshima University, Kagoshima, 890-0065, Japan
| | - Minaki Tsuji
- Graduate School of Science and Engineering, Kagoshima University, Kagoshima, 890-0065, Japan
| | - Dai-Ichiro Kato
- Graduate School of Science and Engineering, Kagoshima University, Kagoshima, 890-0065, Japan
| | - Toshinao Ineno
- Aquaculture Research Institute, Shingu Station, Kindai University, Wakayama, Japan
| | - Yasuhisa Kobayashi
- Department of Fisheries, Faculty of Agriculture, Kindai University, Nara, 631-0052, Japan
- Faculty of Science, Ushimado Marine Institute (UMI), Okayama University, Okayama, 701-4303, Japan
| | - Naoaki Tsutsui
- Department of Life Sciences, Graduate School of Bioresources, Mie University, Mie, 514-8507, Japan
- Faculty of Science, Ushimado Marine Institute (UMI), Okayama University, Okayama, 701-4303, Japan
| | - Sadao Kiyohara
- Graduate School of Science and Engineering, Kagoshima University, Kagoshima, 890-0065, Japan
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Ponnimbaduge Perera P, Perez Guerra D, Riddle MR. The Mexican Tetra, Astyanax mexicanus, as a Model System in Cell and Developmental Biology. Annu Rev Cell Dev Biol 2023; 39:23-44. [PMID: 37437210 DOI: 10.1146/annurev-cellbio-012023-014003] [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] [Indexed: 07/14/2023]
Abstract
Our understanding of cell and developmental biology has been greatly aided by a focus on a small number of model organisms. However, we are now in an era where techniques to investigate gene function can be applied across phyla, allowing scientists to explore the diversity and flexibility of developmental mechanisms and gain a deeper understanding of life. Researchers comparing the eyeless cave-adapted Mexican tetra, Astyanax mexicanus, with its river-dwelling counterpart are revealing how the development of the eyes, pigment, brain, cranium, blood, and digestive system evolves as animals adapt to new environments. Breakthroughs in our understanding of the genetic and developmental basis of regressive and constructive trait evolution have come from A. mexicanus research. They include understanding the types of mutations that alter traits, which cellular and developmental processes they affect, and how they lead to pleiotropy. We review recent progress in the field and highlight areas for future investigations that include evolution of sex differentiation, neural crest development, and metabolic regulation of embryogenesis.
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Affiliation(s)
| | | | - Misty R Riddle
- Department of Biology, University of Nevada, Reno, Nevada, USA;
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Alves APC, Pereira RT, Rosa PV. Morphology of the digestive system in carnivorous freshwater dourado Salminus brasiliensis. JOURNAL OF FISH BIOLOGY 2021; 99:1222-1235. [PMID: 34085710 DOI: 10.1111/jfb.14821] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 05/16/2021] [Accepted: 06/02/2021] [Indexed: 06/12/2023]
Abstract
The digestive system of teleost shows remarkable functional and morphological diversity. In this study, the digestive tract and accessory organs of dourado Salminus brasiliensis are characterized using anatomical, histological, histochemical and immunohistochemical analyses. The existence of taste buds bordered by microridges in the oesophagus of dourado was recorded for the first time, thus showing that the species drives food intake by either swallowing or rejecting the food item. The Y-shaped stomach of dourado consisted of cardiac, cecal and pyloric regions with tubular gastric glands registered solely in the cardiac and cecal segments. The intestine is a short N-shaped tube with two loops, an intestinal coefficient of 0.73. The structure of pyloric caeca is similar to that of the intestine wall, comprising tunica mucosa, tela submucosa, tunica muscularis and tunica serosa layers. Histochemical analyses revealed an increased incidence of goblet cells from the midgut to the hindgut segment. A well-developed enteric plexus of scattered nerve cell and fibres are found along the digestive tract, and the calcitonin gene-related peptide (CGRP) immunoreactive neurons and fibres were identified in the myenteric plexus from the oesophagus to the hindgut. The exocrine pancreas appears diffuse in the mesentery around the stomach, intestine and also reaches the liver, and the endocrine pancreas is organized as a few islets of Langerhans. The liver comprises three distinct, asymmetric lobes, and the portal triad arrangement was registered in this tissue.
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Affiliation(s)
- Angélica P C Alves
- Departamento de Zootecnia, Universidade Federal de Lavras, UFLA, Lavras, Brazil
| | - Raquel T Pereira
- Departamento de Zootecnia, Universidade Federal de Lavras, UFLA, Lavras, Brazil
| | - Priscila V Rosa
- Departamento de Zootecnia, Universidade Federal de Lavras, UFLA, Lavras, Brazil
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Gallman K, Fortune E, Rivera D, Soares D. Differences in behavior between surface and cave Astyanax mexicanus may be mediated by changes in catecholamine signaling. J Comp Neurol 2020; 528:2639-2653. [PMID: 32291742 DOI: 10.1002/cne.24923] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Revised: 04/02/2020] [Accepted: 04/04/2020] [Indexed: 11/07/2022]
Abstract
Astyanax mexicanus is a teleost fish that is in the process of allopatric speciation. Ancestral Astyanax are found in surface rivers and derived blind forms are found in cave systems. Adaptation to life in nutrient poor caves without predation includes the evolution of enhanced food seeking behaviors and loss of defensive responses. These behavioral adaptations may be mediated by changes in catecholaminergic control systems in the brain. We examined the distribution of tyrosine hydroxylase, a conserved precursor for the synthesis of the catecholamines dopamine and noradrenaline, in the brains of surface and cave Astyanax using immunohistochemistry. We found differences in tyrosine hydroxylase staining in regions that are associated with nonvisual sensory perception, motor control, endocrine release, and attention. These differences included significant increases in the diameters of tyrosine hydroxylase immunoreactive soma in cave Astyanax in the olfactory bulb, basal telencephalon, preoptic nuclei, ventral thalamus, posterior tuberculum, and locus coeruleus. These increases in modulation by dopamine and noradrenaline likely indicate changes in behavioral control that underlie adaptations to the cave environment.
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Affiliation(s)
- Kathryn Gallman
- Biological Sciences, New Jersey Institute of Technology, New Jersey, USA
| | - Eric Fortune
- Biological Sciences, New Jersey Institute of Technology, New Jersey, USA
| | - Daihana Rivera
- Biological Sciences, New Jersey Institute of Technology, New Jersey, USA
| | - Daphne Soares
- Biological Sciences, New Jersey Institute of Technology, New Jersey, USA
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Malick C, Chatterjee SK, Bhattacharya S, Suresh VR, Kundu R, Saikia SK. Gustatory ultrastructures of an amphihaline migratory fish hilsa Tenualosa ilisha. Microsc Res Tech 2020; 83:507-513. [PMID: 31951088 DOI: 10.1002/jemt.23439] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Accepted: 12/27/2019] [Indexed: 11/05/2022]
Abstract
This study was conducted with the tongue samples of different life stages of hilsa, that is, adult Marine hilsa, adult Riverine hilsa, and Riverine juvenile hilsa, respectively. Three types of taste buds (Types I, II, and III based on their elevation from the epithelium at different levels) of the tongue, which may be to ensure full utilization of the gustatory ability of the fish were rocorded. Presence of specific taste buds indicate that the fish hilsa dwells in turbid waters with a possible preference toward diatom like planktonic food source. Enhanced expression of taste receptors (T1R1 and T1R3) and associated stimulatory G-proteins subunits on tongue also indicate occurrence of amino acid like substances that guided sensory cues for feeding by this fish. A firm regularity or stringency of the free surface of the epithelial cells may be attributed to compactly arranged microridges. These structures protect against physical abrasions potentially caused during food manoeuvring and swallowing. In our present observations, the surface architectures of the tongue of hilsa are discussed within the background of migratory adaptation of the species in the context of feeding and habitat preferences.
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Affiliation(s)
- Chandan Malick
- Aquatic Ecology and Fish Biology Laboratory, Department of Zoology, Visva-Bharati University, Santiniketan, India
| | - Subhendu Kumar Chatterjee
- Aquatic Ecology and Fish Biology Laboratory, Department of Zoology, Visva-Bharati University, Santiniketan, India
| | - Samir Bhattacharya
- Molecular Endocrinology Laboratory, Department of Zoology, Visva-Bharati University, Santiniketan, India
| | - Vettath Raghavan Suresh
- Riverine Ecology and Fisheries Division, Central Inland Fisheries Research Institute, Barrackpore, Kolkata, India
| | - Rakesh Kundu
- Cell Signaling Laboratory, Department of Zoology, Visva-Bharati University, Santiniketan, India
| | - Surjya Kumar Saikia
- Aquatic Ecology and Fish Biology Laboratory, Department of Zoology, Visva-Bharati University, Santiniketan, India
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Kasumyan AO. The taste system in fishes and the effects of environmental variables. JOURNAL OF FISH BIOLOGY 2019; 95:155-178. [PMID: 30793305 DOI: 10.1111/jfb.13940] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2018] [Accepted: 02/20/2019] [Indexed: 06/09/2023]
Abstract
The adaptability of the taste system in fish has led to a large variety in taste bud morphology, abundance and distribution, as well as in taste physiology characteristics in closely related species with different modes of life and feeding ecology. However, the modifications evoked in the sense of taste, or gustation, particularly during ontogeny when fishes are subject to different environmental variables, remain poorly studied. This review paper focusses on current knowledge to show how plastic and resistant the taste system in fishes is to various external factors, linked to other sensory inputs and shifts in physiological state of individuals. Ambient water temperature is fundamental to many aspects of fish biology and taste preferences are stable to many substances, however, the taste-cell turnover rate strongly depends on water temperature. Taste preferences are stable within water salinity, which gives rise to the possibility that the taste system in anadromous and catadromous fishes will only change minimally after their migration to a new environment. Food-taste selectivity is linked to fish diet and to individual feeding experience as well as the motivation to feed evoked by attractive (water extracts of food) and repellent (alarm pheromone) odours. In contrast, starvation leads to loss of aversion to many deterrent substances, which explains the consumption by starving fishes of new objects, previously refused or just occasionally consumed. Food hardness can significantly modify the final feeding decision to swallow or to reject a grasped and highly palatable food item. Heavy metals, detergents, aromatic hydrocarbons and other water contaminants have the strongest and quickest negative effects on structure and function of taste system in fish and depress taste perception and ability of fishes to respond adequately to taste stimuli after short exposures. Owing to phenotypic plasticity, the taste system can proliferate and partially restore the ability of fishes to respond to food odour after a complete loss of olfaction. In general, the taste system, especially its functionality, is regarded as stable over the life of a fish despite any alteration in their environment and such resistance is vital for maintaining physiological homeostasis.
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Affiliation(s)
- Alexander O Kasumyan
- Department of Ichthyology, Faculty of Biology, Lomonosov Moscow State University, Moscow, Russia
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Kasumyan AO, Marusov EA. Odor Stimulation and Relation to Taste Stimuli in the Blind Cave Fish Astyanax fasciatus. BIOL BULL+ 2018. [DOI: 10.1134/s1062359018060043] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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Hussain JF, Bordoloi S. Adaptive Modifications in Four Fish Species of the Genus Garra (Teleostei; Cyprinidae) in Basistha River, Assam, India. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2018; 24:310-317. [PMID: 29952284 DOI: 10.1017/s1431927618000405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
This paper deals with the study of the surface morphology of barbels, upper lips, and adhesive discs in four hill stream fish species collected from Basistha River, a torrential river in Guwahati city, Assam, India. The four species belonging to the genus Garra namely, Garra gotyla (Gray, 1830), Garra gravelyi (Annandale, 1919), Garra stenorhynchus (Jerdon, 1849), and Garra nasuta (McClelland, 1838) were collected from the same torrential habitat. These fish revealed anatomical peculiarities in their barbels, lips, and adhesive discs which are believed to help them in adapting to such habitats. Organs exhibiting adaptive modifications (barbels, lips, and adhesive discs) were studied with the scanning electron microscope. The study primarily revealed the presence of type I and type II taste buds in the barbels, lips, and adhesive discs, and numerous unculi surrounded by microridges in the upper lips and adhesive discs. A cumulative, intercalated action of these organs enables these fish to adhere and adapt to rocky, torrential streams. Special ability to adapt to these habitats was reflected from the two types of taste buds (I and II) present in the barbels, and the clustering of excrescencies bearing unculi in the lips and adhesive discs of the fish.
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Affiliation(s)
- Jafrin F Hussain
- Biodiversity Laboratory,Resource Management and Environment Section,Life Sciences Division,IASST,Vigyan Path,Paschim Boragaon,Garchuk,Guwahati 781035,Kamrup,Assam,India
| | - Sabitry Bordoloi
- Biodiversity Laboratory,Resource Management and Environment Section,Life Sciences Division,IASST,Vigyan Path,Paschim Boragaon,Garchuk,Guwahati 781035,Kamrup,Assam,India
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Kasumyan AO, Marusov EA. Chemoorientation in the feeding behavior of the blind Mexican cavefish Astyanax fasciatus (Characidae, Teleostei). RUSS J ECOL+ 2015. [DOI: 10.1134/s1067413615060053] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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13
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Gross JB, Meyer B, Perkins M. The rise of Astyanax cavefish. Dev Dyn 2015; 244:1031-1038. [PMID: 25601346 PMCID: PMC4508244 DOI: 10.1002/dvdy.24253] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2014] [Revised: 01/08/2015] [Accepted: 01/10/2015] [Indexed: 01/01/2023] Open
Abstract
Numerous animals have invaded subterranean caverns and evolved remarkably similar features. These features include loss of vision and pigmentation, and gains in nonvisual sensation. This broad convergence echoes smaller-scale convergence, in which members of the same species repeatedly evolve the same cave-associated phenotypes. The blind Mexican tetra of the Sierra de El Abra region of northeastern Mexico has a complex origin, having recurrently colonized subterranean environments through numerous invasions of surface-dwelling fish. These colonizations likely occurred ∼1-5 MYa. Despite evidence of historical and contemporary gene flow between cave and surface forms, the cave-associated phenotype appears to remain quite stable in nature. This model system has provided insight to the mechanisms of phenotypic regression, the genetic basis for constructive trait evolution, and the origin of behavioral novelties. Here, we document the rise of this model system from its discovery by a Mexican surveyor in 1936, to a powerful system for cave biology and contemporary genetic research. The recently sequenced genome provides exciting opportunities for future research, and will help resolve several long-standing biological problems. Developmental Dynamics 244:1031-1038, 2015. © 2015 Wiley Periodicals, Inc.
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Affiliation(s)
- Joshua B Gross
- University of Cincinnati, Department of Biological Sciences, Cincinnati Ohio
| | - Bradley Meyer
- University of Cincinnati, Department of Biological Sciences, Cincinnati Ohio
| | - Molly Perkins
- University of Cincinnati, Department of Biological Sciences, Cincinnati Ohio
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Abstract
We review our recent behavioural and imaging studies testing the consequences of congenital blindness on the chemical senses in comparison with the condition of anosmia. We found that congenitally blind (CB) subjects have increased sensitivity for orthonasal odorants and recruit their visually deprived occipital cortex to process orthonasal olfactory stimuli. In sharp contrast, CB perform less well than sighted controls in taste and retronasal olfaction, i.e. when processing chemicals inside the mouth. Interestingly, CB do not recruit their occipital cortex to process taste stimuli. In contrast to these findings in blindness, congenital anosmia is associated with lower taste and trigeminal sensitivity, accompanied by weaker activations within the 'flavour network' upon exposure to such stimuli. We conclude that functional adaptations to congenital anosmia or blindness are quite distinct, such that CB can train their exteroceptive chemical senses and recruit normally visual cortical areas to process chemical information from the surrounding environment.
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Bichuette ME, Rantin B, Hingst-Zaher E, Trajano E. Geometric morphometrics throws light on evolution of the subterranean catfishRhamdiopsis krugi(Teleostei: Siluriformes: Heptapteridae) in eastern Brazil. Biol J Linn Soc Lond 2014. [DOI: 10.1111/bij.12405] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Maria Elina Bichuette
- Laboratório de Estudos Subterrâneos; Universidade Federal de São Carlos; Rodovia Washington Luís km 235, PO Box 676 13565-905 São Carlos São Paulo state Brazil
| | - Bianca Rantin
- Laboratório de Estudos Subterrâneos; Universidade Federal de São Carlos; Rodovia Washington Luís km 235, PO Box 676 13565-905 São Carlos São Paulo state Brazil
| | - Erika Hingst-Zaher
- Museu Biológico; Instituto Butantan; Av. Vital Brazil, 21500 05503-900 São Paulo São Paulo state Brazil
| | - Eleonora Trajano
- Departamento de Zoologia; Instituto de Biociências; Universidade de São Paulo; Cx. Postal 11461 CEP 05422-970 São Paulo Brazil
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Zachar PC, Jonz MG. Confocal imaging of Merkel-like basal cells in the taste buds of zebrafish. Acta Histochem 2012; 114:101-15. [PMID: 21477848 DOI: 10.1016/j.acthis.2011.03.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2011] [Revised: 03/07/2011] [Accepted: 03/09/2011] [Indexed: 10/18/2022]
Abstract
The oropharyngeal cavity in fish supports a range of sensory modalities, including detection of chemical and mechanical stimuli. Taste buds are found throughout this tissue and may participate in both processes. We used confocal microscopy and immunohistochemistry to characterize the morphology of Merkel-like cells and their association with other cell types and nerve fibers of the taste bud in the vertebrate model, the zebrafish. In addition, we document procedures for the observation of these structures in whole-tissue preparations from larvae and adults using zebrafish-specific and monoclonal antibodies. A single microvillus Merkel-like cell was found in each taste bud regardless of age or location. Merkel-like cells were neurosecretory, as indicated by labelling with the styryl dye, FM1-43, and the synaptic vesicle marker, SV2. Merkel-like cells were associated with SV2- and calretinin-positive taste receptor cells, received innervation from discoid aggregations of nerve fibers, and retained serotonin-filled synaptic vesicles oriented within the cytoplasm toward adjacent innervation. Moreover, a ring-like formation of nerve endings was identified with the neuronal marker, zn-12 that circumscribed the taste receptor area, surrounding calretinin-immunoreactive taste cell microvilli, and appeared to associate with the nerve plexus adjacent to Merkel-like cells. We suggest that these nerve fibers are somatosensory, perhaps associated with mechanoreception or the common chemical sense.
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Fishelson L, Baldwin CC, Hastings PA. Comparison of the oropharyngeal cavity in the Starksiini (Teleostei: Blenniiformes: Labrisomidae): taste buds and teeth, including a comparison with closely-related genera. J Morphol 2012; 273:618-28. [PMID: 22234958 DOI: 10.1002/jmor.20008] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2011] [Revised: 12/08/2011] [Accepted: 12/11/2011] [Indexed: 11/11/2022]
Abstract
The present study describes the distribution of taste buds and teeth in the oropharyngeal cavity of 13 species of adult (18-60 mm SL) Starksiini fishes inhabiting subtidal waters of the Neotropical region. Four types of taste buds described previously in other fish groups were observed within the oropharyngeal cavity, of which type I, situated on prominent protruding papillae, is the most common. The number of taste buds in this cavity varies considerably, ranging from ca. 202 in Starksia lepicoelia to ca. 770 in S. sluiteri. In all the studied species, taste buds are more numerous on the posterior (160-396) than on the anterior (42-294) part of the oropharyngeal cavity. The presence of different numbers of taste buds in different Starksiini species of the same standard length suggests that numbers of taste buds are not directly correlated with size and may be species-specific. Teeth are found on the premaxilla, dentary, vomer, palatine (in some species) and the upper and lower pharyngeal jaws (third pharyngobranchials and fifth ceratobranchials, respectively); the form and number of teeth and taste buds on each of these sites differs among the various species of Starksiini and between them and closely related species of the labrisomid tribes Labrisomini, Mnierpini, and Paraclinini. The results thus suggest potential systematic value in certain features of the oropharyngeal cavity for blenniiform fishes. It is also shown that benthic-feeding omnivorous fishes have higher densities of taste buds than piscivorous fishes. A possible correlation among numbers of taste buds, their positions in the oropharyngeal cavity, and other parameters is discussed.
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Affiliation(s)
- Lev Fishelson
- Department of Zoology, Tel Aviv University, Tel Aviv, Israel.
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19
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Lechner W, Ladich F. How do albino fish hear? J Zool (1987) 2010; 283:186-192. [PMID: 21552308 PMCID: PMC3083522 DOI: 10.1111/j.1469-7998.2010.00762.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2010] [Revised: 08/10/2010] [Accepted: 08/17/2010] [Indexed: 11/28/2022]
Abstract
Pigmentation disorders such as albinism are occasionally associated with hearing impairments in mammals. Therefore, we wanted to investigate whether such a phenomenon also exists in non-mammalian vertebrates. We measured the hearing abilities of normally pigmented and albinotic specimens of two catfish species, the European wels Silurus glanis (Siluridae) and the South American bronze catfish Corydoras aeneus (Callichthyidae). The non-invasive auditory evoked potential (AEP) recording technique was utilized to determine hearing thresholds at 10 frequencies from 0.05 to 5 kHz. Neither auditory sensitivity nor shape of AEP waveforms differed between normally pigmented and albinotic specimens at any frequency tested in both species. Silurus glanis and C. aeneus showed the best hearing between 0.3 and 1 kHz; the lowest thresholds were 78.4 dB at 0.5 kHz in S. glanis (pigmented), 75 dB at 1 kHz in S. glanis (albinotic), 77.6 dB at 0.5 kHz in C. aeneus (pigmented) and 76.9 dB at 1 kHz in C. aeneus (albinotic). This study indicates no association between albinism and hearing ability. Perhaps because of the lack of melanin in the fish inner ear, hearing in fishes is less likely to be affected by albinism than in mammals.
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Affiliation(s)
- W Lechner
- Department of Behavioural Biology, University of Vienna Vienna, Austria
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20
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Varatharasan N, Croll RP, Franz-Odendaal T. Taste bud development and patterning in sighted and blind morphs of Astyanax mexicanus. Dev Dyn 2010; 238:3056-64. [PMID: 19877280 DOI: 10.1002/dvdy.22144] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
In the blind cave-dwelling morph of A. mexicanus, the eye degenerates while other sensory systems, such as gustation, are expanded compared to their sighted (surface-dwelling) ancestor. This study compares the development of taste buds along the jaws of each morph. To determine whether cavefish have an altered onset or rate of taste bud development, we fluorescently labeled basal and receptor cells within taste buds over a developmental series. Our results show that taste bud number increases during development in both morphs. The rate of development is, however, accelerated in cavefish; a small difference in taste bud number exists at 5 dpf reaching threefold by 22 dpf. The expansion of taste buds in cavefish is, therefore, detectable after the onset of eye degeneration. This study provides important insights into the timing of taste bud expansion in cavefish as well as enhances our understanding of taste bud development in teleosts in general.
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21
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Raji AR, Norozi E. Distribution of External Taste Buds in Walking Catfish ( Clarias batrachus) and Piranha (Serrasalmus nattereri). JOURNAL OF APPLIED ANIMAL RESEARCH 2010. [DOI: 10.1080/09712119.2010.9707092] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
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22
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Yamamoto Y, Byerly MS, Jackman WR, Jeffery WR. Pleiotropic functions of embryonic sonic hedgehog expression link jaw and taste bud amplification with eye loss during cavefish evolution. Dev Biol 2009; 330:200-11. [PMID: 19285488 DOI: 10.1016/j.ydbio.2009.03.003] [Citation(s) in RCA: 133] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2008] [Revised: 02/26/2009] [Accepted: 03/04/2009] [Indexed: 12/22/2022]
Abstract
This study addresses the role of sonic hedgehog (shh) in increasing oral-pharyngeal constructive traits (jaws and taste buds) at the expense of eyes in the blind cavefish Astyanax mexicanus. In cavefish embryos, eye primordia degenerate under the influence of hyperactive Shh signaling. In concert, cavefish show amplified jaw size and taste bud numbers as part of a change in feeding behavior. To determine whether pleiotropic effects of hyperactive Shh signaling link these regressive and constructive traits, shh expression was compared during late development of the surface-dwelling (surface fish) and cave-dwelling (cavefish) forms of Astyanax. After an initial expansion along the midline of early embryos, shh was elevated in the oral-pharyngeal region in cavefish and later was confined to taste buds. The results of shh inhibition and overexpression experiments indicate that Shh signaling has an important role in oral and taste bud development. Conditional overexpression of an injected shh transgene at specific times in development showed that taste bud amplification and eye degeneration are sensitive to shh overexpression during the same early developmental period, although taste buds are not formed until much later. Genetic crosses between cavefish and surface fish revealed an inverse relationship between eye size and jaw size/taste bud number, supporting a link between oral-pharyngeal constructive traits and eye degeneration. The results suggest that hyperactive Shh signaling increases oral and taste bud amplification in cavefish at the expense of eyes. Therefore, selection for constructive oral-pharyngeal traits may be responsible for eye loss during cavefish evolution via pleiotropic function of the Shh signaling pathway.
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Affiliation(s)
- Yoshiyuki Yamamoto
- Department of Biology, University of Maryland, College Park, MD 20742, USA
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23
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Synteny and candidate gene prediction using an anchored linkage map of Astyanax mexicanus. Proc Natl Acad Sci U S A 2008; 105:20106-11. [PMID: 19104060 DOI: 10.1073/pnas.0806238105] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The blind Mexican cave tetra, Astyanax mexicanus, is a unique model system for the study of parallelism and the evolution of cave-adapted traits. Understanding the genetic basis for these traits has recently become feasible thanks to production of a genome-wide linkage map and quantitative trait association analyses. The selection of suitable candidate genes controlling quantitative traits remains challenging, however, in the absence of a physical genome. Here, we describe the integration of multiple linkage maps generated in four separate crosses between surface, cave, and hybrid forms of A. mexicanus. We performed exhaustive BLAST analyses of genomic markers populating this integrated map against sequenced genomes of numerous taxa, ranging from yeast to amniotes. We found the largest number of identified sequences (228), with the most expect (E) values <10(-5) (95), in the zebrafish Danio rerio. The most significant hits were assembled into an "anchored" linkage map with Danio, revealing numerous regions of conserved synteny, many of which are shared across critical regions of identified quantitative trait loci (QTL). Using this anchored map, we predicted the positions of 21 test genes on the integrated linkage map and verified that 18 of these are found in locations homologous to their chromosomal positions in D. rerio. The anchored map allowed the identification of four candidate genes for QTL relating to rib number and eye size. The map we have generated will greatly accelerate the production of viable lists of additional candidate genes involved in the development and evolution of cave-specific traits in A. mexicanus.
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Abstract
The distribution and relative frequency of external taste buds (TB) of Garra rufa were studied. TB of Garra rufa were observed on different body location (lips, lateral and ventral areas, forehead, operculum and dorsal-pelvic-pectoral-anal fins). TB are at the highest frequency in lips, forehead, pectoral and anal fins. These structures are moderate as a number in operculum, La2 (between pelvic and anal fins) areas, and then decreased a few in other areas.
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Affiliation(s)
- K Cinar
- Department of Biology, Süleyman Demirel University, 32260 Isparta, Turkey.
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25
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Eram M, Michel WC. Heterogeneous distribution of taste cells in facial and vagal nerve-innervated taste buds. Neuroscience 2006; 138:339-50. [PMID: 16387446 DOI: 10.1016/j.neuroscience.2005.11.018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2005] [Revised: 11/09/2005] [Accepted: 11/14/2005] [Indexed: 11/19/2022]
Abstract
Input from the three gustatory nerves of vertebrates is used to evaluate the nutritional quality of food. In some species, these cranial nerves are modified to accomplish additional specific functions. For example, the facial nerve innervated taste buds distributed over the body surface of catfish aid food search. Physiological studies indicate that this extra-oral taste pathway is more sensitive to amino acids than either the glossopharyngeal or vagal systems of the oral cavity. The current investigation seeks to determine if differences in taste cell subtypes might contribute to the observed differences in sensitivity. The distributions of five low molecular weight metabolites, L-alanine, L-aspartate, L-glutamate, GABA, taurine and the tripeptide glutathione, were examined in 2118 individual taste cells innervated by either the facial or vagal nerve of the channel catfish, Ictalurus punctatus. The metabolite profiles of these cells were determined immunocytochemically and subjected to a k-means clustering algorithm. Fifteen cell classes with quantitatively different patterns of metabolite co-localization were identified. All but one small class of two cells were found in both facial and vagal nerve-innervated taste buds. Four classes (9% of the total cells) had high, two classes (17%) had intermediate and the remaining nine classes (74%) had low levels of GABA immunoreactivity. While the functional significance of differences in metabolite profile remains to be determined, taste cell classes were not uniformly distributed across vagal and facial nerve innervated taste buds and may provide an anatomical basis for previously reported differences in gustatory sensitivity.
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Affiliation(s)
- M Eram
- University of Utah School of Medicine, Department of Physiology, Salt Lake City, UT 84108-1297, USA
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Eram M, Michel WC. Morphological and biochemical heterogeneity in facial and vagal nerve innervated taste buds of the channel catfish, Ictalurus punctatus. J Comp Neurol 2005; 486:132-44. [PMID: 15844211 DOI: 10.1002/cne.20543] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
In catfish, the facial nerve innervates taste buds distributed over the entire body including the barbels, while the glossopharyngeal and vagal nerves innervate oropharyngeal taste buds. Facial nerve innervated taste buds (FITBs) are thought to be involved in food detection and localization, while glossopharyngeal and vagal nerve innervated taste buds (VITBs) evaluate the palatability of food prior to ingestion. Physiological studies indicate that both oral and extra-oral taste buds detect sapid substances such as amino acids and nucleotides, but the facial taste system is more sensitive to some of these substances. The anatomical, molecular, and/or physiological mechanisms underlying the functional differences in these two gustatory pathways remain to be identified. In the current investigation we compare the basic morphological features of FITBs and VITBs and the distribution of the following metabolites: gamma-aminobutyric acid (GABA), glutamate, aspartate, alanine, taurine, and glutathione. Vagal innervated taste buds are significantly longer and narrower than FITBs, with fewer taste cells and a smaller nerve plexus. Each of the metabolites examined was heterogeneously distributed in taste cells with notably more GABA positive cells present in the VITBs. Patterns of metabolite colocalization suggest the presence of several taste cell subtypes. The morphological and metabolite differences noted between FITBs and VITBs provide a potential anatomical basis for the previously noted differences in physiological sensitivity.
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Affiliation(s)
- Mojgan Eram
- University of Utah School of Medicine, Department of Physiology, Salt Lake City, Utah 84108-1297, USA
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27
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Cinar K, Senol N. The Distribution of External Taste Buds in Flower Fish (Pseudophoxinus antalyae). Anat Histol Embryol 2005; 34:176-8. [PMID: 15929733 DOI: 10.1111/j.1439-0264.2005.00590.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Purpose of this study was to determine the distribution of external taste buds of flower fish (Pseudophoxinus antalyae) on different body locations (lip, lateral, ventral and dorsal areas, dorsal-pelvic-pectoral-anal fins). In this species, it was found that the density of taste buds was greater on lip epithelium than that of lateral (between pectoral-anal, anal-caudal fins), ventral (between pelvic and anal fins) and dorsal (close to the head) locations. It was observed that the shape of taste bud changed depending upon the epithelium thickness and it was found that some of these structures protruded towards to the exterior of epithelium.
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Affiliation(s)
- K Cinar
- Department of Biology, Süleyman Demirel University, 32260 Isparta, Turkey.
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28
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Fishelson L. Histogenesis of the oropharyngeal cavity taste buds and the relevant nerves and brain centers in substrate-brooding and mouth-brooding cichlid fish (Cichlidae, Teleostei). ACTA ACUST UNITED AC 2004; 209:179-92. [PMID: 15712011 DOI: 10.1007/s00429-004-0427-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/15/2004] [Indexed: 10/26/2022]
Abstract
This study follows the histogenesis of the oropharyngeal cavity taste buds, along with the development of the relevant neural centers and gustatory nerves, in two cichlid species: the substrate-brooding Cichlasoma cyanoguttatum and the mouth-brooding Astatotilapia flavijosephi, from fertilization to 20-day-old juveniles, grown at a temperature of 26 degrees C. Significant differences in pace of development were shown between the two social types: Substrate-brooders complete embryogenesis and hatch 48 h after fertilization (HAF) and begin to swim 120 HAF, with the yolk sac disappearing 160 HAF, whereas mouth-brooders hatch 84 HAF and begin to swim 196 HAF, with the yolk sac disappearing 360 HAF. Histogenesis of primordial taste buds occurs 75 HAF and 160 HAF in C. cyanoguttatum and A. flavijosephi, respectively. Accordingly, the related sensory ganglia and nerves (VII, IX, and X) develop much earlier in the substrate-brooded larvae and postlarvae. Nerve and brain development in juvenile A. flavijosephi of 13 mm total length (TL) closely resemble those of 8-mm-TL C. cyanoguttatum. These differences in development continue throughout the early stages of growth. Similar differences are observed in the ripening and increase in number of taste buds and dentition on the jaws and pharyngeal bones. The possible triggers and causes of such differences in development, as well as the inductors of taste bud development, are discussed.
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MESH Headings
- Afferent Pathways/embryology
- Afferent Pathways/growth & development
- Afferent Pathways/ultrastructure
- Animals
- Behavior, Animal/physiology
- Brain/embryology
- Brain/growth & development
- Brain/ultrastructure
- Cell Differentiation/physiology
- Cichlids/embryology
- Cichlids/growth & development
- Cichlids/physiology
- Cranial Nerves/embryology
- Cranial Nerves/growth & development
- Cranial Nerves/ultrastructure
- Embryo, Nonmammalian/embryology
- Embryo, Nonmammalian/ultrastructure
- Ganglia, Sensory/embryology
- Ganglia, Sensory/growth & development
- Ganglia, Sensory/ultrastructure
- Larva/growth & development
- Larva/ultrastructure
- Maternal Behavior/physiology
- Microscopy, Electron, Scanning
- Microscopy, Electron, Transmission
- Mouth/embryology
- Mouth/growth & development
- Mouth/ultrastructure
- Pharynx/embryology
- Pharynx/growth & development
- Pharynx/ultrastructure
- Sensory Receptor Cells/embryology
- Sensory Receptor Cells/growth & development
- Sensory Receptor Cells/ultrastructure
- Taste/physiology
- Taste Buds/embryology
- Taste Buds/growth & development
- Taste Buds/ultrastructure
- Tooth/embryology
- Tooth/growth & development
- Tooth/ultrastructure
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Affiliation(s)
- Lev Fishelson
- Department of Zoology, George S. Wise Faculty of Life Sciences, Tel Aviv University, 69978 Tel Aviv, Israel.
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29
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Fishelson L, Delarea Y, Zverdling A. Taste bud form and distribution on lips and in the oropharyngeal cavity of cardinal fish species (Apogonidae, Teleostei), with remarks on their dentition. J Morphol 2004; 259:316-27. [PMID: 14994330 DOI: 10.1002/jmor.10186] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The oral dentition and type and number of taste buds (TB) on the lips and in the oropharyngeal cavity were compared by means of SEM in 11 species of cardinal fishes (Apogonidae) belonging to five genera. The occurrence of a dense cover of skin papillae on the lips of some species (e.g., Apogon frenatus), as well as differences in structure of vomer, tongue, and palatinum, expose additional morphological characters important for clarification of the taxonomy of this group of fishes. Differences are also revealed in the type of dentition, such as on the vomer and epi-hypopharyngeal bones. Strong and dense dentition of the anterior part of the oral cavity and a high number of TB on this site in species feeding on larger prey (e.g., Cheilodipterus spp) is compared to the relatively feeble jaw armor and richness of TB on the more pharyngeal site in species feeding on smaller prey (e.g., Apogon angustatus, A. frenatus). In addition to the three types of TB (Types I-III) previously described from various teleost fish, a fourth type (Type IV), comprising very small buds, was found in some cardinal fish (Apogon angustatus, A. frenatus). The various TB are distributed from the lips to the pharyngeal bones, on the breathing valves, tongue, palatinum, and pharyngeal bones; their number and type on the various sites differ in the different species. In all species studied the Types I and II TB, elevated above the surrounding epithelium, dominated the lips and anterior part of mouth, while Types III and IV, which end apically at the level with the epithelium, dominated the more posterior pharyngeal region. The highest number of TB, around 24,600, were found in Fowleria variegata, a typical nocturnal species, and the lowest in the diurnal and crepuscular Apogon cyanosoma (1,660) and Cheilodipterus quinquestriatus (2,400). Differences are also revealed in the type of dentition, such as on the vomer and epi-hypopharyngeal bones. The number of TB increased with growth of the fishes. The differences in the total number of TB and their distribution in the oropharyngeal cavity in the various species indicates possible different mechanisms of foraging and food-recognition.
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Affiliation(s)
- Lev Fishelson
- Department of Zoology and Laboratory of Electronmicroscopy, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel.
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30
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Abstract
Taste buds are chemosensory endorgans consisting of modified epithelial cells. Fish and other vertebrates use their taste bud cells to sample potential food, either selecting or rejecting substances according to their edibility. The adult gustatory system in fish has been studied thoroughly, including regeneration experiments. Taste buds occur in the epithelia of the lips, the mouth cavity, the oropharyngeal cavity, and also in the skin of the barbels, the head, and sometimes even all over the body surface. Despite its importance for feeding, little is known about the ontogeny of the fish taste system. We examined the development of taste buds in the zebrafish on the light microscopical and the scanning and transmission electron microscopical levels. Taste buds develop later than the olfactory organ and the solitary chemosensory cells, two other chemosensory systems in aquatic vertebrates. The first few taste bud primordia are visible within the epithelia of lips and gill arches 3 to 4 days after fertilization, and the first few taste buds with open receptor areas appear on the lips and simultaneously on the gill arches 4-5 days after fertilization, which coincides with the onset of feeding. Taste buds in the mouth cavity, on the head, and on the barbels are formed later in development. As seen in other fish, zebrafish taste buds contain elongate dark and light cells, termed according to their electron density. Dark cells with a cell apex of many short microvilli appear first, followed by the light cells with one large microvillus. In addition, the zebrafish has a third fusiform cell type, which appears last. This cell type is low in electron density and has a brush-like apical ending with several small microvilli. This cell type has not been described previously. Furthermore, in zebrafish, the ontogenetic processes of taste bud formation differ from regenerative processes described in the literature.
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Affiliation(s)
- Anne Hansen
- Zoological Institute, University of Hamburg, Hamburg, Germany.
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