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Brandon AA, Michael C, Carmona Baez A, Moore EC, Ciccotto PJ, Roberts NB, Roberts RB, Powder KE. Distinct genetic origins of eumelanin levels and barring patterns in cichlid fishes. PLoS One 2024; 19:e0306614. [PMID: 38976656 PMCID: PMC11230561 DOI: 10.1371/journal.pone.0306614] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Accepted: 06/20/2024] [Indexed: 07/10/2024] Open
Abstract
Pigment patterns are incredibly diverse across vertebrates and are shaped by multiple selective pressures from predator avoidance to mate choice. A common pattern across fishes, but for which we know little about the underlying mechanisms, is repeated melanic vertical bars. To understand the genetic factors that modify the level or pattern of vertical barring, we generated a genetic cross of 322 F2 hybrids between two cichlid species with distinct barring patterns, Aulonocara koningsi and Metriaclima mbenjii. We identify 48 significant quantitative trait loci that underlie a series of seven phenotypes related to the relative pigmentation intensity, and four traits related to patterning of the vertical bars. We find that genomic regions that generate variation in the level of eumelanin produced are largely independent of those that control the spacing of vertical bars. Candidate genes within these intervals include novel genes and those newly-associated with vertical bars, which could affect melanophore survival, fate decisions, pigment biosynthesis, and pigment distribution. Together, this work provides insights into the regulation of pigment diversity, with direct implications for an animal's fitness and the speciation process.
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Affiliation(s)
- A. Allyson Brandon
- Department of Biological Sciences, Clemson University, Clemson, South Carolina, United States of America
| | - Cassia Michael
- Department of Biological Sciences, Clemson University, Clemson, South Carolina, United States of America
| | - Aldo Carmona Baez
- Department of Biological Sciences, Genetics and Genomics Academy, North Carolina State University, Raleigh, North Carolina, United States of America
| | - Emily C. Moore
- Department of Biological Sciences, Genetics and Genomics Academy, North Carolina State University, Raleigh, North Carolina, United States of America
| | - Patrick J. Ciccotto
- Department of Biology, Warren Wilson College, Swannanoa, North Carolina, United States of America
| | - Natalie B. Roberts
- Department of Biological Sciences, Genetics and Genomics Academy, North Carolina State University, Raleigh, North Carolina, United States of America
| | - Reade B. Roberts
- Department of Biological Sciences, Genetics and Genomics Academy, North Carolina State University, Raleigh, North Carolina, United States of America
| | - Kara E. Powder
- Department of Biological Sciences, Clemson University, Clemson, South Carolina, United States of America
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2
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Liu J, Bitsue HK, Yang Z. Skin colour: A window into human phenotypic evolution and environmental adaptation. Mol Ecol 2024; 33:e17369. [PMID: 38713101 DOI: 10.1111/mec.17369] [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: 01/31/2024] [Revised: 04/13/2024] [Accepted: 04/17/2024] [Indexed: 05/08/2024]
Abstract
As modern humans ventured out of Africa and dispersed around the world, they faced novel environmental challenges that led to geographic adaptations including skin colour. Over the long history of human evolution, skin colour has changed dramatically, showing tremendous diversity across different geographical regions, for example, the majority of individuals from the expansive lands of Africa have darker skin, whereas the majority of people from Eurasia exhibit lighter skin. What adaptations did lighter skin confer upon modern humans as they migrated from Africa to Eurasia? What genetic mechanisms underlie the diversity of skin colour observed in different populations? In recent years, scientists have gradually gained a deeper understanding of the interactions between pigmentation gene and skin colour through population-based genomic studies of different groups around the world, particularly in East Asia and Africa. In this review, we summarize our current understanding of 26 skin colour-related pigmentation genes and 48 SNPs that influence skin colour. Important pigmentation genes across three major populations are described in detail: MFSD12, SLC24A5, PDPK1 and DDB1/CYB561A3/TMEM138 influence skin colour in African populations; OCA2, KITLG, SLC24A2, GNPAT and PAH are key to the evolution of skin pigmentation in East Asian populations; and SLC24A5, SLC45A2, TYR, TYRP1, ASIP, MC1R and IRF4 significantly contribute to the lightening of skin colour in European populations. We summarized recent findings in genomic studies of skin colour in populations that implicate diverse geographic environments, local adaptation among populations, gene flow and multi-gene interactions as factors influencing skin colour diversity.
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Affiliation(s)
- Jiuming Liu
- Tianjian Laboratory of Advanced Biomedical Sciences, Academy of Medical Sciences, Zhengzhou University, Zhengzhou, China
| | - Habtom K Bitsue
- Tianjian Laboratory of Advanced Biomedical Sciences, Academy of Medical Sciences, Zhengzhou University, Zhengzhou, China
| | - Zhaohui Yang
- Tianjian Laboratory of Advanced Biomedical Sciences, Academy of Medical Sciences, Zhengzhou University, Zhengzhou, China
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3
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Elkin J, Martin A, Courtier-Orgogozo V, Santos ME. Analysis of the genetic loci of pigment pattern evolution in vertebrates. Biol Rev Camb Philos Soc 2023; 98:1250-1277. [PMID: 37017088 DOI: 10.1111/brv.12952] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Revised: 03/08/2023] [Accepted: 03/14/2023] [Indexed: 04/06/2023]
Abstract
Vertebrate pigmentation patterns are amongst the best characterised model systems for studying the genetic basis of adaptive evolution. The wealth of available data on the genetic basis for pigmentation evolution allows for analysis of trends and quantitative testing of evolutionary hypotheses. We employed Gephebase, a database of genetic variants associated with natural and domesticated trait variation, to examine trends in how cis-regulatory and coding mutations contribute to vertebrate pigmentation phenotypes, as well as factors that favour one mutation type over the other. We found that studies with lower ascertainment bias identified higher proportions of cis-regulatory mutations, and that cis-regulatory mutations were more common amongst animals harbouring a higher number of pigment cell classes. We classified pigmentation traits firstly according to their physiological basis and secondly according to whether they affect colour or pattern, and identified that carotenoid-based pigmentation and variation in pattern boundaries are preferentially associated with cis-regulatory change. We also classified genes according to their developmental, cellular, and molecular functions. We found a greater proportion of cis-regulatory mutations in genes implicated in upstream developmental processes compared to those involved in downstream cellular functions, and that ligands were associated with a higher proportion of cis-regulatory mutations than their respective receptors. Based on these trends, we discuss future directions for research in vertebrate pigmentation evolution.
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Affiliation(s)
- Joel Elkin
- Department of Zoology, University of Cambridge, Downing Street, Cambridge, CB2 3EJ, UK
| | - Arnaud Martin
- Department of Biological Sciences, The George Washington University, 800 22nd St. NW, Suite 6000, Washington, DC, 20052, USA
| | | | - M Emília Santos
- Department of Zoology, University of Cambridge, Downing Street, Cambridge, CB2 3EJ, UK
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4
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Brandon AA, Michael C, Carmona Baez A, Moore EC, Ciccotto PJ, Roberts NB, Roberts RB, Powder KE. Distinct genetic origins of eumelanin intensity and barring patterns in cichlid fishes. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.02.547430. [PMID: 37461734 PMCID: PMC10349982 DOI: 10.1101/2023.07.02.547430] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 07/25/2023]
Abstract
Pigment patterns are incredibly diverse across vertebrates and are shaped by multiple selective pressures from predator avoidance to mate choice. A common pattern across fishes, but for which we know little about the underlying mechanisms, is repeated melanic vertical bars. In order to understand genetic factors that modify the level or pattern of vertical barring, we generated a genetic cross of 322 F2 hybrids between two cichlid species with distinct barring patterns, Aulonocara koningsi and Metriaclima mbenjii. We identify 48 significant quantitative trait loci that underlie a series of seven phenotypes related to the relative pigmentation intensity, and four traits related to patterning of the vertical bars. We find that genomic regions that generate variation in the level of eumelanin produced are largely independent of those that control the spacing of vertical bars. Candidate genes within these intervals include novel genes and those newly-associated with vertical bars, which could affect melanophore survival, fate decisions, pigment biosynthesis, and pigment distribution. Together, this work provides insights into the regulation of pigment diversity, with direct implications for an animal's fitness and the speciation process.
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Affiliation(s)
- A. Allyson Brandon
- Department of Biological Sciences, Clemson University, Clemson, SC 29634, USA
| | - Cassia Michael
- Department of Biological Sciences, Clemson University, Clemson, SC 29634, USA
| | - Aldo Carmona Baez
- Department of Biological Sciences, and Genetics and Genomics Academy, North Carolina State University, Raleigh, NC 27695, USA
| | - Emily C. Moore
- Department of Biological Sciences, and Genetics and Genomics Academy, North Carolina State University, Raleigh, NC 27695, USA
- Department of Biological Sciences, University of Montana, Missoula, MT 59812, USA
| | | | - Natalie B. Roberts
- Department of Biological Sciences, and Genetics and Genomics Academy, North Carolina State University, Raleigh, NC 27695, USA
| | - Reade B. Roberts
- Department of Biological Sciences, and Genetics and Genomics Academy, North Carolina State University, Raleigh, NC 27695, USA
| | - Kara E. Powder
- Department of Biological Sciences, Clemson University, Clemson, SC 29634, USA
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5
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Tobler R, Souilmi Y, Huber CD, Bean N, Turney CSM, Grey ST, Cooper A. The role of genetic selection and climatic factors in the dispersal of anatomically modern humans out of Africa. Proc Natl Acad Sci U S A 2023; 120:e2213061120. [PMID: 37220274 PMCID: PMC10235988 DOI: 10.1073/pnas.2213061120] [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: 07/29/2022] [Accepted: 03/14/2023] [Indexed: 05/25/2023] Open
Abstract
The evolutionarily recent dispersal of anatomically modern humans (AMH) out of Africa (OoA) and across Eurasia provides a unique opportunity to examine the impacts of genetic selection as humans adapted to multiple new environments. Analysis of ancient Eurasian genomic datasets (~1,000 to 45,000 y old) reveals signatures of strong selection, including at least 57 hard sweeps after the initial AMH movement OoA, which have been obscured in modern populations by extensive admixture during the Holocene. The spatiotemporal patterns of these hard sweeps provide a means to reconstruct early AMH population dispersals OoA. We identify a previously unsuspected extended period of genetic adaptation lasting ~30,000 y, potentially in the Arabian Peninsula area, prior to a major Neandertal genetic introgression and subsequent rapid dispersal across Eurasia as far as Australia. Consistent functional targets of selection initiated during this period, which we term the Arabian Standstill, include loci involved in the regulation of fat storage, neural development, skin physiology, and cilia function. Similar adaptive signatures are also evident in introgressed archaic hominin loci and modern Arctic human groups, and we suggest that this signal represents selection for cold adaptation. Surprisingly, many of the candidate selected loci across these groups appear to directly interact and coordinately regulate biological processes, with a number associated with major modern diseases including the ciliopathies, metabolic syndrome, and neurodegenerative disorders. This expands the potential for ancestral human adaptation to directly impact modern diseases, providing a platform for evolutionary medicine.
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Affiliation(s)
- Raymond Tobler
- Australian Centre for Ancient DNA, The University of Adelaide, Adelaide, SA5005, Australia
| | - Yassine Souilmi
- Australian Centre for Ancient DNA, The University of Adelaide, Adelaide, SA5005, Australia
- Environment Institute, The University of Adelaide, Adelaide, SA5005, Australia
| | - Christian D. Huber
- Australian Centre for Ancient DNA, The University of Adelaide, Adelaide, SA5005, Australia
| | - Nigel Bean
- Australian Research Council Centre of Excellence for Mathematical and Statistical Frontiers, The University of Adelaide, Adelaide, SA5005, Australia
- School of Mathematical Sciences, The University of Adelaide, Adelaide, SA5005, Australia
| | - Chris S. M. Turney
- Division of Research, University of Technology Sydney, Ultimo, NSW2007, Australia
| | - Shane T. Grey
- School of Biotechnology and Biomolecular Sciences, Faculty of Science, University of New South Wales, Sydney, NSW2052, Australia
- Transplantation Immunology Group, Translation Science Pillar, Garvan Institute of Medical Research, Darlinghurst, NSW2010, Australia
| | - Alan Cooper
- Australian Centre for Ancient DNA, The University of Adelaide, Adelaide, SA5005, Australia
- Blue Sky Genetics, Ashton, SA5137, Australia
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6
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Kratochwil CF, Kautt AF, Nater A, Härer A, Liang Y, Henning F, Meyer A. An intronic transposon insertion associates with a trans-species color polymorphism in Midas cichlid fishes. Nat Commun 2022; 13:296. [PMID: 35027541 PMCID: PMC8758764 DOI: 10.1038/s41467-021-27685-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Accepted: 12/01/2021] [Indexed: 11/09/2022] Open
Abstract
Polymorphisms have fascinated biologists for a long time, but their genetic underpinnings often remain elusive. Here, we aim to uncover the genetic basis of the gold/dark polymorphism that is eponymous of Midas cichlid fish (Amphilophus spp.) adaptive radiations in Nicaraguan crater lakes. While most Midas cichlids are of the melanic "dark morph", about 10% of individuals lose their melanic pigmentation during their ontogeny and transition into a conspicuous "gold morph". Using a new haplotype-resolved long-read assembly we discover an 8.2 kb, transposon-derived inverted repeat in an intron of an undescribed gene, which we term goldentouch in reference to the Greek myth of King Midas. The gene goldentouch is differentially expressed between morphs, presumably due to structural implications of inverted repeats in both DNA and/or RNA (cruciform and hairpin formation). The near-perfect association of the insertion with the phenotype across independent populations suggests that it likely underlies this trans-specific, stable polymorphism.
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Affiliation(s)
- Claudius F Kratochwil
- Zoology and Evolutionary Biology, Department of Biology, University of Konstanz, Universitätsstrasse 10, 78457, Konstanz, Germany.
- Institute of Biotechnology, HiLIFE, University of Helsinki, Helsinki, Finland.
| | - Andreas F Kautt
- Zoology and Evolutionary Biology, Department of Biology, University of Konstanz, Universitätsstrasse 10, 78457, Konstanz, Germany
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA, 02138, USA
| | - Alexander Nater
- Zoology and Evolutionary Biology, Department of Biology, University of Konstanz, Universitätsstrasse 10, 78457, Konstanz, Germany
| | - Andreas Härer
- Zoology and Evolutionary Biology, Department of Biology, University of Konstanz, Universitätsstrasse 10, 78457, Konstanz, Germany
- Division of Biological Sciences, Section of Ecology, Behavior & Evolution, University of California San Diego, La Jolla, CA, USA
| | - Yipeng Liang
- Zoology and Evolutionary Biology, Department of Biology, University of Konstanz, Universitätsstrasse 10, 78457, Konstanz, Germany
- Department of Biology, University of Virginia, Charlottesville, VA, 22903, USA
| | - Frederico Henning
- Department of Genetics, Institute of Biology, Federal University of Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil
| | - Axel Meyer
- Zoology and Evolutionary Biology, Department of Biology, University of Konstanz, Universitätsstrasse 10, 78457, Konstanz, Germany.
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7
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Beninde J, Möst M, Meyer A. Optimized and affordable high-throughput sequencing workflow for preserved and nonpreserved small zooplankton specimens. Mol Ecol Resour 2020; 20:1632-1646. [PMID: 32677266 DOI: 10.1111/1755-0998.13228] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Revised: 07/12/2020] [Accepted: 07/13/2020] [Indexed: 12/12/2022]
Abstract
Genomic analysis of hundreds of individuals is increasingly becoming standard in evolutionary and ecological research. Individual-based sequencing generates large amounts of valuable data from experimental and field studies, while using preserved samples is an invaluable resource for studying biodiversity in remote areas or across time. Yet, small-bodied individuals or specimens from collections are often of limited use for genomic analyses due to a lack of suitable extraction and library preparation protocols for preserved or small amounts of tissues. Currently, high-throughput sequencing in zooplankton is mostly restricted to clonal species, that can be maintained in live cultures to obtain sufficient amounts of tissue, or relies on a whole-genome amplification step that comes with several biases and high costs. Here, we present a workflow for high-throughput sequencing of single small individuals omitting the need for prior whole-genome amplification or live cultures. We establish and demonstrate this method using 27 species of the genus Daphnia, aquatic keystone organisms, and validate it with small-bodied ostracods. Our workflow is applicable to both live and preserved samples at low costs per sample. We first show that a silica-column based DNA extraction method resulted in the highest DNA yields for nonpreserved samples while a precipitation-based technique gave the highest yield for ethanol-preserved samples and provided the longest DNA fragments. We then successfully performed short-read whole genome sequencing from single Daphnia specimens and ostracods. Moreover, we assembled a draft reference genome from a single Daphnia individual (>50× coverage) highlighting the value of the workflow for non-model organisms.
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Affiliation(s)
- Jannik Beninde
- Department of Biology, University of Konstanz, Konstanz, Germany
| | - Markus Möst
- Department of Ecology, University of Innsbruck, Innsbruck, Austria
| | - Axel Meyer
- Department of Biology, University of Konstanz, Konstanz, Germany
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8
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Aardema ML, Stiassny MLJ, Alter SE. Genomic Analysis of the Only Blind Cichlid Reveals Extensive Inactivation in Eye and Pigment Formation Genes. Genome Biol Evol 2020; 12:1392-1406. [PMID: 32653909 PMCID: PMC7502198 DOI: 10.1093/gbe/evaa144] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/06/2020] [Indexed: 12/21/2022] Open
Abstract
Trait loss represents an intriguing evolutionary problem, particularly when it occurs across independent lineages. Fishes in light-poor environments often evolve “troglomorphic” traits, including reduction or loss of both pigment and eyes. Here, we investigate the genomic basis of trait loss in a blind and depigmented African cichlid, Lamprologus lethops, and explore evolutionary forces (selection and drift) that may have contributed to these losses. This species, the only known blind cichlid, is endemic to the lower Congo River. Available evidence suggests that it inhabits deep, low-light habitats. Using genome sequencing, we show that genes related to eye formation and pigmentation, as well as other traits associated with troglomorphism, accumulated inactivating mutations rapidly after speciation. A number of the genes affected in L. lethops are also implicated in troglomorphic phenotypes in Mexican cavefish (Astyanax mexicanus) and other species. Analysis of heterozygosity patterns across the genome indicates that L. lethops underwent a significant population bottleneck roughly 1 Ma, after which effective population sizes remained low. Branch-length tests on a subset of genes with inactivating mutations show little evidence of directional selection; however, low overall heterozygosity may reduce statistical power to detect such signals. Overall, genome-wide patterns suggest that accelerated genetic drift from a severe bottleneck, perhaps aided by directional selection for the loss of physiologically expensive traits, caused inactivating mutations to fix rapidly in this species.
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Affiliation(s)
- Matthew L Aardema
- Department of Biology, Montclair State University.,Sackler Institute for Comparative Genomics, American Museum of Natural History, New York, New York
| | - Melanie L J Stiassny
- Department of Ichthyology, American Museum of Natural History, New York, New York
| | - S Elizabeth Alter
- Department of Ichthyology, American Museum of Natural History, New York, New York.,The Graduate Center, City University of New York.,Department of Biology, York College/The City University of New York
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Liang Y, Meyer A, Kratochwil CF. Neural innervation as a potential trigger of morphological color change and sexual dimorphism in cichlid fish. Sci Rep 2020; 10:12329. [PMID: 32704058 PMCID: PMC7378239 DOI: 10.1038/s41598-020-69239-w] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2020] [Accepted: 07/09/2020] [Indexed: 12/24/2022] Open
Abstract
Many species change their coloration during ontogeny or even as adults. Color change hereby often serves as sexual or status signal. The cellular and subcellular changes that drive color change and how they are orchestrated have been barely understood, but a deeper knowledge of the underlying processes is important to our understanding of how such plastic changes develop and evolve. Here we studied the color change of the Malawi golden cichlid (Melanchromis auratus). Females and subordinate males of this species are yellow and white with two prominent black stripes (yellow morph; female and non-breeding male coloration), while dominant males change their color and completely invert this pattern with the yellow and white regions becoming black, and the black stripes becoming white to iridescent blue (dark morph; male breeding coloration). A comparison of the two morphs reveals that substantial changes across multiple levels of biological organization underlie this polyphenism. These include changes in pigment cell (chromatophore) number, intracellular dispersal of pigments, and tilting of reflective platelets (iridosomes) within iridophores. At the transcriptional level, we find differences in pigmentation gene expression between these two color morphs but, surprisingly, 80% of the genes overexpressed in the dark morph relate to neuronal processes including synapse formation. Nerve fiber staining confirms that scales of the dark morph are indeed innervated by 1.3 to 2 times more axonal fibers. Our results might suggest an instructive role of nervous innervation orchestrating the complex cellular and ultrastructural changes that drive the morphological color change of this cichlid species.
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Affiliation(s)
- Yipeng Liang
- Zoology and Evolutionary Biology, Department of Biology, University of Konstanz, Universitätsstrasse 10, 78457, Konstanz, Germany
| | - Axel Meyer
- Zoology and Evolutionary Biology, Department of Biology, University of Konstanz, Universitätsstrasse 10, 78457, Konstanz, Germany.
| | - Claudius F Kratochwil
- Zoology and Evolutionary Biology, Department of Biology, University of Konstanz, Universitätsstrasse 10, 78457, Konstanz, Germany.
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10
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Liang Y, Gerwin J, Meyer A, Kratochwil CF. Developmental and Cellular Basis of Vertical Bar Color Patterns in the East African Cichlid Fish Haplochromis latifasciatus. Front Cell Dev Biol 2020; 8:62. [PMID: 32117987 PMCID: PMC7026194 DOI: 10.3389/fcell.2020.00062] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2019] [Accepted: 01/22/2020] [Indexed: 12/13/2022] Open
Abstract
The East African adaptive radiations of cichlid fishes are renowned for their diversity in coloration. Yet, the developmental basis of pigment pattern formation remains largely unknown. One of the most common melanic patterns in cichlid fishes are vertical bar patterns. Here we describe the ontogeny of this conspicuous pattern in the Lake Kyoga species Haplochromis latifasciatus. Beginning with the larval stages we tracked the formation of this stereotypic color pattern and discovered that its macroscopic appearance is largely explained by an increase in melanophore density and accumulation of melanin during the first 3 weeks post-fertilization. The embryonal analysis is complemented with cytological quantifications of pigment cells in adult scales and the dermis beneath the scales. In adults, melanic bars are characterized by a two to threefold higher density of melanophores than in the intervening yellow interbars. We found no strong support for differences in other pigment cell types such as xanthophores. Quantitative PCRs for twelve known pigmentation genes showed that expression of melanin synthesis genes tyr and tyrp1a is increased five to sixfold in melanic bars, while xanthophore and iridophore marker genes are not differentially expressed. In summary, we provide novel insights on how vertical bars, one of the most widespread vertebrate color patterns, are formed through dynamic control of melanophore density, melanin synthesis and melanosome dispersal.
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Affiliation(s)
- Yipeng Liang
- Zoology and Evolutionary Biology, Department of Biology, University of Konstanz, Konstanz, Germany
| | - Jan Gerwin
- Zoology and Evolutionary Biology, Department of Biology, University of Konstanz, Konstanz, Germany
| | - Axel Meyer
- Zoology and Evolutionary Biology, Department of Biology, University of Konstanz, Konstanz, Germany
| | - Claudius F Kratochwil
- Zoology and Evolutionary Biology, Department of Biology, University of Konstanz, Konstanz, Germany
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