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MELANISM-MELANISTIC-MELANIN-MELANISTIK--part 1
MELANISM-MELANISTIC-MELANIN-MELANISTIK--part 2
MELANISM-MELANISTIC-MELANIN-MELANISTIK--part 3
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Melanism terkait dengan proses adaptasi yang
disebut adaptif. Paling umum, individu berwarna gelap menjadi bertahan untuk bertahan hidup dan bereproduksi di
lingkungan mereka karena mereka disamarkan dengan lebih baik. Hal ini membuat
beberapa spesies kurang mencolok bagi predator, sementara yang lain, seperti
kumbang hitam, menggunakannya sebagai keuntungan mencari makan selama berburu
malam. Biasanya, melanism adaptif adalah diwariskan: merupakan sebuah gen dominan, yang seluruhnya atau hampir seluruhnya dalam
phenotype, bertanggung jawab untuk jumlah melanin yang berlebihan .
Melanism merupakan pengembangan dari
pigmen melanin berwarna gelap pada kulit atau pelengkap dan berlawanan dengan
albinism . Kata melanism berasal dari bahasa Yunani:. Μελανός ( "pigmen
hitam")
Pseudo-Melanisme, juga disebut abundism,
adalah varian lain dari pigmentasi, yang ditandai dengan bintik-bintik gelap
atau garis-garis yang diperbesar, yang menutupi sebagian besar tubuh hewan,
sehingga tampak melanistic. Kekurangan
atau total ketiadaan pigmen melanin disebut amelanism
melanism industrial adalah efek dari polusi perkotaan di banyak
spesies arthropoda. Ini adalah fenomena organisme berkembangnya pigmentasi gelap saat terkena lingkungan
tercemar oleh deposito jelaga gelap dan penumpukan sulfat dari polusi industri.
Dalam jenis melanism industrial ini ,
individu berpigmen gelap mengembangkan pertahanan yang lebih tinggi dan disukai oleh seleksi
alam. Perubahan ini sebagai akibat dari modifikasi tekanan seleksi yang
merupakan salah satu kasus yang paling
mencatat pada evolusi Darwin. Kasus yang paling umum dari adaptasi ini
ditemukan dalam urutan arthropoda Lepidoptera.
hewan melanistic ditemukan untuk membawa
setidaknya satu salinan dari urutan MC1R alel mutan, bearing 15-base pair
inframe deletion.
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Melanism merupakan perkembangan yang tidak semestinya dari pigmen berwarna gelap di kulit atau pelengkap dan merupakan kebalikan dari albinisme. Kata 'melanism' disimpulkan dari kata Yunani yang berarti pigmen hitam. Pseudo-Melanisme, juga disebut abundism, adalah varian lain dari pigmentasi, yang ditandai dengan bintik-bintik gelap atau garis-garis diperbesar, yang menutupi sebagian besar tubuh hewan sehingga tampak melanistic.
Melanism terkait dengan proses adaptasi disebut adaptif.
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melanism industri, gelap-pada kulit, bulu, atau bulu-diakuisisi oleh populasi binatang yang hidup di sebuah kawasan industri di mana lingkungan ber jelaga gelap. melanisasi dari populasi meningkatkan kemungkinan bahwa organisme akan bertahan hidup dan bereproduksi; itu berlangsung selama beberapa generasi sebagai hasil dari seleksi alam, dari hewan yang lebih mencolok oleh predator.
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Dari awal beberapa penyebab telah diusulkan untuk perubahan frekuensi gen melanic di ngengat peppered Biston betularia dan ngengat melanic industri lainnya. Hal ini termasuk intrinsik yang lebih tinggi dari bentuk melanic dan predasi selektif untuk kamuflase. metode baru analisis harus memberikan informasi lebih lanjut tentang sistem melanic dan migrasi yang akan melengkapi pemahaman kita tentang contoh penting dari evolusi cepat.
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Varian gelap, di sisi lain, sekarang disamarkan, dan lebih mungkin untuk bertahan hidup dan berkembang biak. Dalam kasus buku teks melanism industri, hanya dalam beberapa generasi, varian gelap menjadi yang paling umum.
Dalam lebih dari 50 tahun, berbagai variasi gelap naik hanya 2% dari populasi untuk membentuk lebih dari 95%, perubahan yang tidak bisa dijelaskan dengan teori selain seleksi alam dan melanism industri.
Insiden melanism industri adalah proses yang disebut micro-evolusi, di mana tekanan seleksi dalam spesies menyebabkan perubahan.
melanism industri dapat didefinisikan sebagai peningkatan proporsional gelap, atau melanin, pigmen pada individu dari suatu populasi, yang disebabkan oleh perubahan lingkungan yang dihasilkan dari polusi industri.
JENIS INDUSTRI melanism
Tiga kategori melanism industri :
A. industri penuh polimorfisme melanic melibatkan bentuk melanic berbeda yang telah muncul sejak revolusi industri dan telah meningkat sebagai konsekuensi dari efek industrialisasi terhadap lingkungan.
B. Partial industri polimorfisme melanic melibatkan spesies polimorfik yang memiliki bentuk melanic yang berbeda sebelum revolusi industri.
Bentuk-bentuk telah meningkat dalam frekuensi sebagai konsekuensi dari efek industrialisasi.
C. poligenik melanism industri melibatkan spesies di mana warna tanah beberapa atau semua anggota populasi telah gelap secara bertahap sebagai akibat dari efek industrialisasi.
Perlu dicatat bahwa melanism adalah fenomena umum di seluruh kerajaan hewan, dengan banyak faktor yang tidak terkait dengan industrialisasi atau polusi mempengaruhi keberhasilan bentuk melanic di beberapa spesies, termasuk manusia.
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J jaguar melanistic pada Henry
Doorly Zoo. Melanism adalah hasil dari sebuah alel dominan tetapi
tetap relatif langka di jaguar.
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Mungkin dari kita semua
jarang mendengar kata ini. Melanistic adalah kelainan kulit, yang bertolak
belakang dengan Albino, namun hewan hewan Melanistic pun sangatlah
menawan
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Melanisme
merupakan perkembangan yang tidak semestinya dari pigmen warna gelap di kulit
dan merupakan kebalikan dari albinisme. 'Melanisme' berasal dari kata Yunani
yang berarti pigmen hitam. Pseudo-Melanisme, juga disebutabundism, merupakan
varian dari pigmentasi, yang ditandai dengan bintik hitam atau garis yang
diperbesar, yang menutupi sebagian besar tubuh hewan sehingga tampak
melanistic.
Melanisme yang terkait dengan proses adaptasi
disebut adaptif.
Paling umum, individu gelap menjadi lebih bisa bertahan hidup dan bereproduksi
dalam lingkungan mereka karena mereka disamarkan dengan lebih baik. Hal ini
membuat beberapa spesies kurang mencolok atau terlindung dari predator,
Biasanya Melanisme adaptif adalah diwariskan:
Sebuah gen dominan, yang seluruhnya atau hampir seluruhnya dalam phenotype
bertanggung jawab atas jumlah berlebihan melanin. Melanisme Adaptif telah
terbukti terjadi dalam berbagai hewan, termasuk mamalia seperti tupai, kucing,
dan ular karang.
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Melanism industri adalah istilah
biologi mengacu pada hewan. Itu berarti merujuk penggelapan dari kulit atau
yang di tempatnya seperti bulu
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Perkembangan yang meningkat dari melanin pigmen berwarna gelap di kulit dan rambut binatang disebut melanism, dan merupakan kebalikan dari Albinisme. Sama seperti hasil Albinisme pada hewan yang memukau putih, melanism dapat membuat hewan semua hitam
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Melanin adalah pigmen gelap yang bertanggung jawab untuk proses penyamakan yang terjadi pada manusia ketika mereka terkena sinar matahari. Pada orang sebenarnya merupakan reaksi terhadap kerusakan sel-sel kulit. hewan melanistic memiliki peningkatan jumlah pigmentasi hitam atau hampir hitam di kulit, bulu, rambut, atau jaringan luar lainnya. Melanism adalah kebalikan dari albinisme dan terjadi dengan sekitar frekuensi yang sama.
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Biasanya, melanism didefinisikan oleh kenaikan hadirnya pigmentasi gelap pada sebuah organisme.
Melanism adalah variasi genetik yang menyebabkan hewan untuk memiliki terlalu banyak pigmentasi. Ini adalah fenomena yang telah diamati pada banyak spesies dari hewan.
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Dalam ngengat noctuid Panthea furcilla (Packard) melanism meningkat dengan cepat di Putnam, Connecticut, Sepenuhnya melanic dan melanistic sangat kuat yang dominan atas abu-abu normal, dan sepenuhnya melanic dominan atas sangat kuat melanistic yang sangat kuat . melanism larva independen dari melanism dewasa.
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Melanistic adalah istilah yang digunakan untuk
harimau yang kelebihan pigmen, ini adalah kebalikan dari ablonisium yang tidak
memiliki pigmen. Harimau melanistic hampir semua hitam dengan garis-garis
kuning jeruk terutama pada bagian bawahnya.
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Melanistic (black beauties)
Ketika ada kelainan dimana pigmen
warna melanin kekurangan, yang disebut albino, maka ada pula yang memiliki
kelebihan gen warna hitam ini, disebut sebagai black beauties
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Melanic (berpigmen gelap) fenotipe pada mamalia menyediakan sistem ampuh di mana untuk belajar dasar genetik yang terjadi secara alami fenotipe mutan karena melanism terjadi di banyak mamalia, dan pigmentasi jalur mamalia dipahami dengan baik
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Dermal melanin diproduksi oleh sel-sel kulit yang disebut melanosit. Manusia umumnya memiliki konsentrasi yang sama dari melanosit di kulit mereka. Namun, melanosit pada beberapa individu atau kelompok etnis mengekspresikan melanin memproduksi gen lebih atau kurang sering mengakibatkan konsentrasi yang lebih besar atau lebih kecil dari melanin kulit.
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Albinisme melanism albinisme Disebabkan oleh kekurangan melanin
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Melanistic warna mantel terjadi sebagai polimorfisme umum di 11 dari 37 spesies felid dan mencapai frekuensi populasi yang tinggi dalam beberapa kasus tetapi tidak pernah mencapai fiksasi lengkap
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. Namun, populasi gelap (melanic) tikus ditemukan pada lava gelap, dan warna menyembunyikan ini memberikan perlindungan dari predator burung dan mamalia.
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Dalam jaguar dan jaguarundi, pigmen gelap terkait dengan dua mutasi yang berbeda pada gen yang sama, MC1R. MC1R milik keluarga gen dimana kode untuk protein yang disebut (tujuh helix) reseptor transmembran permukaan sel.
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Melanictic adalah semua
warna hewan berwarna hitam, kebalikannya dari jenis albino yang bisa terjadi di
alam
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Melanophores: produce black pigment (melanin).
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Semua
orang pasti sudah tahu tentang Albino yaitu kelainan pigmen yang menyebabkan
sekujur tubuh pengidap kelihatan putih. Namun bagaimana dengan dengan
Melanisme?
Melanisme bisa dibilang lawan dari Albino, jika penderita kelihatan Putih maka kebalikannya penderita Melanisme kelihatan sangat hitam.
Kata 'Melanisme' berasal dari bahasa Yunani : μελανός , yang berarti pigmen hitam. Penyakit Melanisme merupakan perkembangan pigmen hitam yang pesat sehingga tubuh kelihatan sangat hitam.
Melanisme bisa dibilang lawan dari Albino, jika penderita kelihatan Putih maka kebalikannya penderita Melanisme kelihatan sangat hitam.
Kata 'Melanisme' berasal dari bahasa Yunani : μελανός , yang berarti pigmen hitam. Penyakit Melanisme merupakan perkembangan pigmen hitam yang pesat sehingga tubuh kelihatan sangat hitam.
Melanisme atau melanosis pada manusia terjadi di organ
tertentu. Misalnya, melanosis coli mengacu pada peningkatan pigmentasi pada
lapisan usus besar. Ini sebenarnya karena penggunaan berlebihan obat pencahar
dan merupakan sedikit keliru karena tidak disebabkan meningkatnya pigmen
melanin, melainkan, lipofuscin dalam makrofag.
Melanisme terkait dengan proses adaptasi disebut adaptif.
Paling umum, individu gelap menjadi bugar untuk bertahan hidup dan bereproduksi
dalam lingkungan mereka karena mereka disamarkan baik. Hal ini membuat beberapa
spesies predator kurang mencolok, sementara yang lain seperti macan kumbang
hitam menggunakannya sebagai keuntungan berburu mencari makan pada malam hari.
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Morph melanistic benar-benar warna morph pertama dan morph warna paling klasik dari Thamnophis.
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Melanism adalah bentuk warna di mana individu memiliki jumlah abnormal pigmen hitam. dasar genetik yang tidak dipahami dengan baik, tetapi perkawinan sedarah dianggap bagian dari penyebabnya.
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melanism. Melanism dasarnya kebalikan dari albinisme
melanism adalah hal mekanin yang meluap-luap , menyebabkan seorang individu dengan jumlah abnormal warna hitam. Melanistic ular garter Timur dapat ditemukan di sepanjang Barat Basin Danau Erie dan pada beberapa Lake Erie Islands. Beberapa populasi bisa sampai 50% melanistic di daerah ini, yang berarti akan ada campuran individu normal dan melanistic dalam satu wilayah.
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Meskipun penelitian yang luas, fungsi dan signifikansi adaptif dari melanism tetap controversial.pada ular, individu melanistic menikmati keuntungan termal dibandingkan dengan individu normal berwarna karena kemampuan termoregulasi superior. Konsekuensi hipotetis keunggulan thermal ini adalah bahwa individu melanistic memiliki periode hari yang lebih panjang dan periode aktif musiman, dan dengan demikian dapat mengumpulkan lebih banyak makanan, sehingga membuat tingkat pertumbuhan yang lebih tinggi dan ukuran tubuh yang lebih besar.
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ular garter melanistic (sirtalis Thamnophis) yang biasa umum di dekat Danau Erie, rupanya karena seleksi untuk kemampuan termoregulasi di habitat danau-shore yang dingin (yang morphs melanistic) melebihi seleksi untuk crypsis (yang morphs bergaris).
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pigmen neuronal tipe melanic diidentifikasi dalam putamen, korteks, serebelum, dan daerah besar lainnya dari otak manusia. Pigmen ini terdiri dari butiran 30 nm dalam ukuran, yang terkandung dalam organel bersama-sama dengan tetesan lipid, dan mereka terakumulasi dalam penuaan, mencapai konsentrasi setinggi 1,5-2,6 mg / mg jaringan di daerah otak besar. pigmen ini, yang neuromelanins, mengandung komponen melanic, lipid, dan peptida.
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melanin, pigmen biologi gelap (biochrome) ditemukan di kulit, rambut, bulu, sisik, mata, dan beberapa membran internal, itu juga ditemukan dalam peritoneum di banyak hewan (misalnya, katak),
Melanism mengacu pada deposisi melanin dalam jaringan hewan hidup. Prose Kimia tergantung pada metabolisme asam amino tirosin, tidak adanya yang menyebabkan albinisme, atau kurangnya pigmentasi.
"Industri" melanism telah terjadi pada populasi ngengat tertentu, di mana warna dominan telah berubah pucat abu-abu untuk individu berwarna gelap
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Penelitian ini berusaha untuk menentukan apakah pigmen yang dihasilkan oleh Proteus mirabilis dari bentuk-L berbagai asam amino aromatik di bawah kondisi aerobik adalah melanic di alam. Ini adalah pigmen hitam-coklat yang berperilaku seperti melanin dalam banyak hal, yaitu fitur kelarutan, pemutihan oleh agen pengoksidasi dan respon positif terhadap uji Fontana-Masson.
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Pigmen coklat gelap yang berasal dari teh dan teh polifenol dipelajari. sifat fisik dan kimia mengungkapkan bahwa pigmen langsung diekstrak dari daun teh dan berasal dari polifenol teh yang mirip dengan melanins yang khas. Penyelidikan lebih lanjut menunjukkan bahwa kedua pigmen melanic dimiliki kemampuan antioksidan yang sama, karena kelat dan pembilasan sifat mereka.
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Mimikri dan melanism di Lepidoptera memberikan contoh meyakinkan pertama dari seleksi alam dalam tindakan. Analisis genetik kini telah menunjukkan bahwa, secara mengejutkan, mimikri di kupu-kupu Heliconius dan melanism pada ngengat diaktifkan tepat pada gen yang sama: korteks.
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MC1R, juga dikenal sebagai gen ekstensi, mengontrol produksi pigmen pada melanosit. Bentuk dominan dari gen, "E" alel, memungkinkan anjing untuk menghasilkan eumelanin, yang merupakan pigmen hitam. Sebuah mutasi dalam gen MC1R menyebabkan sel penghasil pigmen hanya menghasilkan phaeomelanin, mengubah semua eumelanin dalam mantel untuk phaeomelanin. Bentuk gen diwakili sebagai "e" alel. "E" alel resesif, yang berarti bahwa anjing harus memiliki dua salinan dari mutasi MC1R untuk mengekspresikan warna bulu kuning atau merah. merah resesif dapat menutupi varian warna lain bahkan masking Merle.
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melanism industri mengacu pada evolusi warna tubuh gelap spesies hewan yang hidup di habitat menghitam oleh jelaga industri. Fenomena ini telah didokumentasikan dalam banyak spesies yang bersembunyi dari predator dengan membaur dengan latar belakang mereka. ngengat memberikan salah satu contoh. Sebelum revolusi industri, ngengat di Inggris abu-abu pucat, tapi setelah habitatnya menjadi tercemar dengan jelaga dari industri batu bara, fenotipe melanic (hitam) menjadi banyak dan menyebar ke daerah lain
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variasi morfologi dalam populasi alami adalah test bed genom untuk mempelajari antarmuka antara molekul evolusi dan populasi genetika, tetapi beberapa pertanyaan yang paling menarik melibatkan organisme non-model yang referensi genom dijelaskan kurang baik . Banyak felid polimorfisme spesies exhibit untuk melanism tetapi peran relatif dimainkan oleh hanyutan genetika, seleksi alam, dan antar spesies hibridisasi tetap tidak menentu.
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Terjadinya melanism (gelap dari warna latar belakang) didokumentasikan dalam 13 spesies felid, dalam beberapa kasus mencapai frekuensi tinggi pada tingkat populasi.
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Dua makalah baru-baru ini atas dasar molekul melanism memperkuat rantai bukti yang menghubungkan genotipe dan fenotipe di alam.
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Article Citation:
Richard B. King (2003) MENDELIAN INHERITANCE OF
MELANISM IN THE GARTER SNAKE THAMNOPHIS SIRTALIS. Herpetologica: December 2003,
Vol. 59, No. 4, pp. 484-489.
ARTICLES
MENDELIAN INHERITANCE OF MELANISM IN THE GARTER SNAKE THAMNOPHIS
SIRTALIS
The results of 11 captive matings among nine female
and six male descendents of six wild-caught female common garter snakes from
polymorphic populations near Lake Erie confirm that melanism is inherited as a simple Mendelian
trait and is recessive to a striped pattern. The make-up of litters born to 71
wild-caught females from five sites corroborate this result: striped females
never produced all melanistic litters and the frequency of entirely striped,
mixed, and entirely melanistic litters conforms to expectations based on
estimated allele frequencies. Possible explanations for a previously reported
non-Mendelian inheritance of melanism include the occurrence of a somatic
mutation or bias in sperm production and fertilization ability.
Accepted: March 26, 2003;
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TUESDAY,
MAY 19, 2015
Melanistic Garter Snake
For half of this summer, I'll be living up in Northern Ohio
helping with some salamander research as a field assistant. It's only been 2
weeks so far, but we've found so many interesting and wonderful things. The
best find of last week came from one of the field sites on South Bass Island in
Lake Erie.
Olivia Brooks, who is the one behind the nature-oriented Twitter account Wild Earth, is the other field
assistant. We're always on the lookout for snakes, and while in the middle of
trying to find salamanders, Olivia yelled "snake!" We ran toward
Olivia and were met by a very young Eastern Garter Snake. I've covered Eastern
Garter Snakes before, and
you might notice that this one doesn't really look like a garter at all. The
coloration is all wrong, right? Garter snakes aren't black?!
This is indeed an Eastern Garter Snake, Thamnophis sirtalis sirtalis,
but it is an individual with melanism.
Melanism is essentially
the opposite of albinism. While albinism is the absence of melanin (a
dark colored pigment found in skin), melanism is the overabundance of melanin, leading to an individual with
an abnormal amount of black coloration. Melanistic Eastern Garter Snakes can be
found along the Western Basin of Lake Erie and on some of the Lake Erie
Islands. Some populations can be up to 50% melanistic in this area, meaning
there will be a mixture of normal-looking and melanistic individuals within one
area.
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Does the thermal advantage of melanism produce size
differences in color-dimorphic snakes?
Author information
Abstract
Despite
extensive research, the function and adaptive significance of melanism remain
controversial.In snakes, melanistic individuals enjoy a thermal advantage
compared with normal-colored individuals due to superior thermoregulatory
capabilities. The hypothetical consequences of this thermal advantage are that
melanistic individuals have longer daily and seasonal active periods, and thus
collect more food, resulting in a higher growth rate and larger body size. To test
the generality of this hypothesis, I made intermorph comparisons of body size
using a melanistic/striped color-dimorphic snake (Elaphe quadrivirgata) on
Yakushima Island, Japan. Melanistic individuals were not significantly larger
in body size than striped individuals in either males or females, and the
largest individual was a striped morph in both sexes. Thus, the pattern
predicted based on the hypothetical consequences of the thermal advantage of
melanism was not observed in E. quadrivirgata on Yakushima Island. Based on
this coupled with the results of a previous survey on the thermal ecology of
the snake, I conclude that melanistic individuals of E. quadrivirgata on
Yakushima Island may benefit from fast body warming, which shortens the time of
basking, but this benefit is not sufficient to realize larger body size
compared to that of striped individuals, and/or such a benefit is not realized
in the hypothesized way. The thermal advantage of melanism in nature may be
more limited in scope than has been assumed.
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Grass Snake
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Common name:
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Grass snake
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Taxonomy:
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Natrix natrix helvetica (Linnaeus 1758)
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Other Names:
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Collared snake
Neidr y gwair (Welsh) Ringed snake (Archaic) Common snake (Archaic) Green snake (Archaic) Hedge snake (Archaic) Water snake (Archaic) |
Morphology
Occasional cases of
polymorphism turn up and have been recorded in the UK, including several
sightings of melanistic
individuals, off white/buff and completely green colouration although
these sightings are very rare.
.......................
Gene
flow and melanism
in Lake Erie garter snake populations
Authors
·
Robin Lawson,
1.
·
Richard B. King
1.
·
Citation tools
·
*Department of Biological Sciences, Northern Illinois University,
DeKalb, IL 60115, U.S.A.
Abstract
Melanistic
garter snakes (Thamnophis sirtalis) are unusually
common near Lake Erie, apparently because selection for thermoregulatory
ability in cool lake-shore habitats (which favours melanistic morphs) outweighs
selection for crypsis (which favours striped morphs). However, morph frequencies are highly variable
among sites, suggesting that random genetic drift also influences colour
pattern. In an effort to better understand the evolutionary processes influencing
garter snake colour patterns, we estimated Fx and Nm (the number of migrants
per generation) among island and mainland populations from patterns of
allozymic variation detected using electrophoresis. Estimates of Nm were high,
ranging from 2.7 to 37.6 between pairs of study sites and making it unlikely
that differences in morph frequencies among sites were solely the result of
random genetic drift. Furthermore, differences in Fst estimates between colour pattern (a
one-locus two-allele trait) and allozyme loci suggest that colour pattern
alleles are not in Hardy-Weinberg equilibrium, most likely as a result of
natural selection. Comparison of allozymic data from Lake Erie with those from
more distant sites suggests that gene flow occurs over long distances in T. sirtalis.
.............................
Thermal Aspects of Melanistic and Striped Morphs of the Snake Elaphe quadrivirgata
Department of Zoology, Graduate School of Science, Kyoto
University, Sakyo, Kyoto 606-8502, Japan
* Corresponding author. Phone: +81-75-753-4099; Fax :
+81-75-753-4113; E-mail:koji@ethol.zool.kyoto-u.ac.jp
Abstract
Temperature is a critical factor limiting various aspects
of the biology of ectotherms. In addition to environmental factors, coloration
and body size are two physical properties that influence ectotherms' body
temperature (Tb). I compared the influences of these
properties on thermal aspects of the two morphs of the color-dimorphic snake (E.
quadrivirgata) under experimental conditions. First, I fitted Tb data during heating to the von Bertalanffy equation, but
considered parameter values of the equilibrium temperature obtained to be
biologically meaningless. Alternatively, I limited the data for comparison of the
morphs to Tb≤35°C, which was the Tb at which snakes began to move vigorously
in the experiment. The rate of Tb increase was significantly greater in the
melanistic morph than in the striped morph. Heating rate was negatively
correlated with body size in both morphs. The interaction of body size and
heating rate did not significantly differ between the two morphs. The
possibility of linkage, due to thermal advantage, between small body size and
the prevalence of melanism in the population studied is briefly discussed.
Rapid increase of Tb is biologically advantageous because
snakes with such ability would be released from various time and environmental
constraints associated with thermoregulation under particular environmental
conditions.
Received: March 23, 2005; Accepted: August 1, 2005
....................
New melanic pigments in the
human brain that accumulate in aging and block environmental toxic metals
1.
Contributed by Nicholas J. Turro,
September 9, 2008 (received for review August 7, 2008)
2.
Full Text
Abstract
Neuronal pigments
of melanic type were identified in the putamen, cortex, cerebellum, and other
major regions of human brain. These pigments consist of granules 30 nm in size,
contained in organelles together with lipid droplets, and they accumulate in
aging, reaching concentrations as high as 1.5–2.6 μg/mg tissue in major brain
regions. These pigments, which we term neuromelanins, contain melanic, lipid,
and peptide components. The melanic component is aromatic in
structure, contains a stable free radical, and is synthesized from the
precursor molecule cysteinyl-3,4-dihydroxyphenylalanine. This contrasts with
neuromelanin of the substantia nigra, where the melanic precursor is
cysteinyl-dopamine. These neuronal pigments have some structural similarities
to the melanin found in skin. The precursors of lipid components of the
neuromelanins are the polyunsaturated lipids present in the surrounding
organelles. The synthesis of neuromelanins in the various regions of the human
brain is an important protective process because the melanic component is
generated through the removal of reactive/toxic quinones that would otherwise
cause neurotoxicity. Furthermore, the resulting melanic component serves an
additional protective role through its ability to chelate and accumulate metals,
including environmentally toxic metals such as mercury and lead.
......................
melanin, a dark biological pigment (biochrome) found in skin, hair,
feathers, scales, eyes, and some internal membranes; it is also found in the
peritoneum of many animals (e.g., frogs), but its role there is not
understood. Formed as an end product during metabolism of the amino acid tyrosine,
melanins are conspicuous in dark skin moles of humans; in the black dermal
melanocytes (pigment cells) of most dark-skinned peoples; and as brown, diffuse
spots in the epidermis.
Melanism refers to the deposition of
melanin in the tissues of living animals. The chemistry of the process depends
on the metabolism of the amino acid tyrosine, the absence of which
results in albinism, or lack of pigmentation. Melanism
can also occur pathologically, as in a malignant melanoma, a
cancerous tumour composed of melanin-pigmented cells.
Melanic
pigmentation is advantageous in many ways: (1) It is a barrier against the
effects of the ultraviolet rays of sunlight. On exposure to sunlight, for
example, the human epidermis undergoes gradual tanning as a result of an
increase in melanin pigment. (2) It is a mechanism for the absorption of heat
from sunlight, a function that is especially important for cold-blooded
animals. (3) It affords concealment to certain animals that become active in
twilight. (4) It limits the incidence of beams of light entering the eye and
absorbs scattered light within the eyeball, allowing greater visual acuity. (5)
It provides resistance to abrasion because of the molecular structure of the
pigment. Many desert-dwelling birds, for example, have black plumage as an
adaptation to their abrasive habitat.
“Industrial” melanism has occurred in certain moth
populations, in which the predominant coloration has
changed pale gray to dark-coloured individuals. This is a striking example of rapid evolutionary change; it
has taken place in less than 100 years. It occurs in moth species that depend
for their survival by day on blending into specialized backgrounds, such as
lichened tree trunks and boughs. Industrial pollution, in the form of soot,
kills lichens and blackens the trees and ground, thus destroying the protective
backgrounds of light-coloured moths, which are rapidly picked off and eaten by
birds. Melanic moths, by their camouflage, then become selectively favoured.
“Industrial” melanic moths have arisen from recurrent mutations and have spread
via natural selection. See coloration; integument.
..................
Study of a melanic pigment of
Proteus mirabilis.
Author information
Abstract
The
present study sought to determine whether the pigment produced by Proteus
mirabilis from the L-forms of various aromatic amino acids under aerobic
conditions is melanic in nature. It is a black-brown pigment which behaves like
a melanin in many respects, namely solubility features, bleaching by oxidizing
agents and positive response to the Fontana-Masson assay. In the
present study, for the first time, it was shown by electron spin resonance
analysis that a bacterial melanin is able to act as a free radical trap, as was
previously demonstrated for other melanins. Scanning electron microscopy
studies showed a specific organized structure of the pigment as rounded
aggregates of spherical bodies. DNA hybridization data did not reveal, in the
P. mirabilis genome, any nucleotide sequence related to Shewanella colwelliana
mel A, one of the two melanogenesis systems already defined at the molecular level
in bacteria. Results obtained from experiments on pigment production inhibition
suggest a possible role of tyrosinase in P. mirabilis melanogenesis. In
conclusion, from the bulk of our results, it appears that the pigment produced
by P. mirabilis is melanic in nature.
..................
Pigments in hybrid, variant and melanic tanagers (birds)
Author links open the overlay panel. Numbers correspond to the affiliation
list which can be exposed by using the show more link.
Abstract
1.
1. Rump feathers in
parental and hybrid populations of Ramphocelus tanagers along an altitudinal cline varied from scarlet to lemon
yellow. However, spectral and chromatographic data indicated the presence of
only a single carotenoid pigment. Dilution and statistical tests indicate that
the observable colors were a function of pigment concentration. Spectral
differences may be correlated with a single peak (470 nm) in the absorbance
curve.
2.
2. In a color variant of R. passerinii the spectral and
chromatographic data suggest only a difference in pigment concentration. In
both cases, these results were unexpected when compared to previous studies on
seasonal change and the pigmentation of genetic mutants.
3.
3. Melanic mutant scarlet
tanagers retained the feather structure typical of carotenoid-containing
feathers.
4.
4. These observations
relate to other studies on the biochemistry, metabolic and genetic control of
avian carotenoid pigments and to proposed relationships between feather
structure and pigment content.
....................
Isolation
and characterization of melanic
pigments derived from tea and tea polyphenols
Abstract
The dark brown pigments derived from tea and tea
polyphenols were studied. Physical and chemical properties revealed that
pigments directly extracted from tea leaves and derived from tea polyphenols
were similar to typical melanins. Further investigation showed that both
melanic pigments possessed similar antioxidant capability, due to their
chelating and scavenging properties. The inhibitory effect of melanic pigments, either from tea or
tea polyphenols, was significantly stronger than that of non-treated tea polyphenols.
According to these properties, we have extracted melanin from tea. In addition,
oxidation of tea polyphenols also provided an alternative method to maximize
the yields. The extracted melanin is an antioxidant, which interrupted free
radical reactions at a step in the development chain by its scavenging
properties and, at the step of initiation, by its ability to chelate metals.
.........................
Isolation and characterization
of melanic pigments
derived from tea and tea polyphenols.
(AGR:IND23244504)
Abstract
The dark
brown pigments derived from tea and tea polyphenols were studied. Physical and chemical
properties revealed that pigments directly extracted from tea leaves and
derived from tea polyphenols were similar to typical melanins.
Further investigation showed that both melanic pigments possessed similar
antioxidant capability, due to their chelating and scavenging properties. The
inhibitory effect of melanic pigments, either from tea or tea polyphenols, was
significantly stronger than that of non-treated tea polyphenols.
According to these properties, we have extracted melanin from tea. In addition, oxidation of tea polyphenols also provided an alternative method to
maximize the yields. The extracted melanin is an antioxidant, which interrupted free
radical reactions at a step in the development chain by its scavenging
properties and, at the step of initiation, by its ability to chelate metals.
......................
melanic
pigments
Food Colorants:
Chemical and Functional Properties
diedit oleh Carmen Socaciu
.......................
melanic
pigments
The Fungal Spore
and Disease Initiation in Plants and Animals
diedit oleh G.T. Cole,H.C. Hoch
......................
The Genetic Basis of Melanism in the Gray Squirrel (Sciurus carolinensis)
+Author Affiliations
1.From the Department of Life Sciences, Anglia
Ruskin University, Cambridge CB1 1PT, UK (McRobie) and the Department of Life
Sciences, Anglia Ruskin University, Cambridge CB1 1PT, UK (Kelly and Thomas)
1.
Address correspondence
to Helen McRobie at the address above, or e-mail:helen.mcrobie@anglia.ac.uk.
Abstract
The black squirrel is a melanic variant of the gray squirrel (Sciurus carolinensis). We found 3 coat color variants in the gray squirrel: the
wild-type gray, a jet-black, and a brown–black phenotype. These 3 morphs are
due to varying distributions of eumelanin and phaeomelanin pigment in hairs.
The melanocortin 1 receptor (MC1R) plays a central role in regulating eumelanin
and phaeomelanin production. We sequenced theMC1R gene for all 3 coat color phenotypes and found a 24 base-pair
deletion. The gray phenotype was homozygous for the wild-type allele E+, the
jet-black phenotype was homozygous for the MC1R-Δ24 allele EB, and the
brown–black phenotype was heterozygous for the E+ and EB alleles. We
conclude that melanism in gray squirrels is associated with the MC1R-Δ24 EB allele at amino acid positions 87–94 and that this allele is
incompletely dominant to the wild-type allele. We predict that the MC1R-Δ24 EB allele encodes a constitutively active or hyperactive receptor.
...................
Molecular genetics and evolution
of melanism in the
cat family.
Author information
Abstract
Melanistic coat coloration occurs as a common
polymorphism in 11 of 37 felid species and reaches high population frequency in
some cases but never achieves complete fixation. To investigate the genetic
basis, adaptive significance, and evolutionary history of melanistic variants
in the Felidae, we mapped, cloned, and sequenced the cat homologs of two
putative candidate genes for melanism (ASIP [agouti] and MC1R) and identified
three independent deletions associated with dark coloration in three different
felid species. Association and transmission analyses revealed that a 2 bp
deletion in the ASIP gene specifies black coloration in domestic cats, and two
different "in-frame" deletions in the MC1R gene are implicated in
melanism in jaguars and jaguarundis. Melanistic individuals from five other
felid species did not carry any of these mutations, implying that there are at
least four independent genetic origins for melanism in the cat family. The
inferred multiple origins and independent historical elevation in population
frequency of felid melanistic mutations suggest the occurrence of adaptive evolution
of this visible phenotype in a group of related free-ranging species.
................
Ecological Genetics: A Key Gene for Mimicry and Melanism
,
Mimicry and melanism in Lepidoptera provided the first
convincing examples of natural selection in action. Genetic analysis has now
shown that, surprisingly, mimicry in Heliconius butterflies and melanism in peppered
moths are switched at precisely the same gene: cortex.
......................
E-Locus (Recessive Red/Yellow, Melanistic Mask
Allele)
Description:
MC1R, also known as the extension gene,
controls production of pigment in melanocytes. The dominant form of the gene,
the "E" allele, allows the dog to produce eumelanin, which is a black
pigment. A mutation in the MC1R gene causes the pigment-producing cells to only
produce phaeomelanin, turning all eumelanin in the coat to phaeomelanin. This
form of the gene is represented as the "e" allele. The "e"
allele is recessive, meaning that a dog must have two copies of the MC1R
mutation to express the yellow or red coat color. Recessive red can mask other
color variants even masking merle.
A third allele exists in the extension gene, Emwhich is also dominant. This causes the dog to have a black mask on their face, also known as a melanistic mask. This allele acts similarly to the E allele, in that it causes a black-based coat. Because it is dominant, a dog only needs one copy of the Em allele to express this trait. In solid black dogs with a copy of the Em allele, the mask is hidden. However, it can still pass on the melanistic mask to future offspring.
The "ee" genotype can vary in expression between different breeds. In some breeds, the difference between a black or brown dog and a yellow dog is obvious, such as in Labrador Retrievers. However, in other breeds, such as Cocker Spaniels, this difference may be more subtle. Other breeds express the "ee" phenotype as a red color.
It is important to note that the extension gene is only one of four important genes in determining the coat color of a canine. The dog's color can vary greatly with different mutated alleles on other genes. Dogs that are "ee" will always be yellow. However, there is a great deal of variation of dogs that are "EE" or "Ee," depending on the B-Locus, A-Locus, K-Locus, and D-Locus.
E Locus
Testing:
The
MC1R gene, or E Locus, has three possible forms: Black (E), melanistic mask (Em),
and Red/Yellow (ee). The E-Allele test determines how many copies of the
recessive "e" alleles a dog carries. The Em-Allele test
determines how many copies of the melanistic mask allele a dog carries.
Sample
Type:
Animal Genetics accepts buccal swab, blood, and dewclaw samples
for testing. Sample collection kits are available and can be ordered at Canine Test Now.
Testing is
Relevant for the Following Breeds:
All
breeds.
Results:
Animal
Genetics offers DNA testing for both E and Em alleles. The genetic test verifies the
presence of these mutations and presents results as one of the following:
e-Allele
Results:
|
E/E
|
Black
|
The dog carries two copies of the
dominant E allele. The dog will produce normal black pigmentation, and will
always pass on the "E" allele to any potential offspring.
|
|
E/e
|
Black carries Red/Yellow
|
Both the dominant and recessive copies
of the E allele are present. The dog will produce normal black pigment, but
carries the allele responsible for the Red/Yellow phenotype. The dog can pass
on either allele to potential offspring.
|
|
e/e
|
Red/Yellow
|
Two copies of the recessive allele are
present. The dog has a Red/Yellow coat, and will always pass on the recessive
allele to all potential offspring.
|
Em-Allele
Results:
|
Em/Em
|
Black Mask
|
The dog carries two copies of the
melanistic mask allele. The dog has a melanistic mask, and will always pass
on a copy of the Em allele
to potential offspring. All offspring will also have a melanistic mask.
|
|
Em/n
|
Black Mask
|
One copy of the melanistic mask allele
is present, and the dog will have a black mask. The dog has a 50% chance of
passing on this allele to potential offspring.
|
|
n/n
|
No Black Mask
|
Dog tested negative for the melanistic
mask allele. The dog will not have a black mask, and cannot pass a copy on to
any offspring.
|
Combination
E-Locus Results:
|
E/E
|
Black
|
Dog carries two copies of the dominant
E allele. The dog does not carry the alleles for the black mask or recessive
Red/Yellow.
|
|
Em/Em
|
Black Mask
|
Dog carries two copies of the black
mask allele, and will always pass on a copy of the mask allele to any
offspring. The dog does not carry recessive Red/Yellow.
|
|
Em/E
|
Black Mask
|
Dog carries one copy of the mask
allele, and does not carry the allele for recessive Red/Yellow.
|
|
Em/e
|
Black Mask
|
Dog carries one copy of the mask allele
and one copy of the recessive allele. The dog could pass on either allele to
any offspring.
|
|
E/e
|
Black
|
Dog carries one copy of the recessive
allele, and does not carry the mask allele.
|
|
e/e
|
Red/Yellow
|
Dog has two copies of the recessive
allele, and does not have the mask allele. The dog will always pass on a copy
of the recessive allele to any offspring.
|
Submit a
Sample for Testing:
To submit a sample for testing please go to Canine Test Now.
To order a sample collection kit please go to Order Sample Collection kits.
To order a sample collection kit please go to Order Sample Collection kits.
.................
Industrial Melanism
Bruce S
Grant, College of William and Mary, Williamsburg, Virginia, USA
Published
online: June 2012
DOI:
10.1002/9780470015902.a0001788.pub3
Abstract
Industrial melanism refers to the
evolution of dark body colours in animal species that live in habitats blackened
by industrial soot. The phenomenon has been documented in numerous species that
hide from predators by blending in with their backgrounds. Peppered moths
provide one example. Before the industrial revolution, peppered moths in the UK
were pale grey, but after their habitats became polluted with soot from coal‐fired industries, melanic (black)
phenotypes became numerous and spread to other regions. Away
from industrial centres, the pale phenotype remained common. Following clean
air legislation a century later, the atmosphere improved, soot‐damaged habitats gradually recovered, and
the pale phenotype returned as the predominant form. Parallel changes have
occurred in America. The melanic and pale phenotypes are determined by genes,
and the changes in their percentages in populations reflect natural selection.
Experiments identify bird predation on the moth phenotypes as the agent of
selection.
Key Concepts:
·
The natural colour patterns of animals are adaptations produced
by natural selection.
·
A change in frequency (percentage) of genetically determined
phenotypes in natural populations is direct evidence of evolutionary change.
·
Mutations introduce new genetic variation to a population, but
recurrent mutations occur too rarely to bring about rapid changes in the
frequency of genes.
·
Random changes in the frequency of genes (genetic drift) are
irregular and unpredictable in direction.
·
Directional, rapid changes in the frequency of genetically
determined phenotypes in populations result from natural selection.
·
Historical records on phenotypic frequencies from population
samples allow the assessment of natural selection.
·
Gene flow (migration) retards genetic differentiation among
geographically widespread populations.
·
Clines indicate different selection pressures along
environmental gradients; when selection is removed, migration homogenises the
differences along a cline.
·
Parallel evolution is ‘nature's replicate experiment’.
..........................
Recurrent
Evolution of Melanism
in South American Felids
Abstract
Morphological variation in natural populations is a
genomic test bed for studying the interface between molecular evolution and
population genetics, but some of the most interesting questions involve
non-model organisms that lack well annotated reference genomes. Many felid
species exhibit polymorphism for melanism but the relative roles played by
genetic drift, natural selection, and interspecies hybridization remain
uncertain.
We identify mutations of Agouti signaling protein
(ASIP) or the Melanocortin 1 receptor
(MC1R) as independent causes of melanism in three closely related South
American species: the pampas cat (Leopardus
colocolo), the kodkod (Leopardus
guigna), and Geoffroy’s cat (Leopardus
geoffroyi). To assess population level variation in the regions
surrounding the causative mutations we apply genomic resources from the
domestic cat to carry out clone-based capture and targeted resequencing of 299
kb and 251 kb segments that contain ASIP and MC1R, respectively, from 54
individuals (13–21 per species), achieving enrichment of ~500–2500-fold and
~150x coverage. Our analysis points to unique evolutionary histories for each
of the three species, with a strong selective sweep in the pampas cat, a
distinctive but short melanism-specific haplotype in the Geoffroy’s cat, and
reduced nucleotide diversity for both ancestral and melanism-bearing
chromosomes in the kodkod. These results reveal an important role for natural
selection in a trait of longstanding interest to ecologists, geneticists, and
the lay community, and provide a platform for comparative studies of
morphological variation in other natural populations.
...........................
How the Leopard
Hides Its Spots: ASIP Mutations and Melanism in Wild Cats
Abstract
The occurrence of
melanism (darkening of the background coloration) is documented in 13 felid
species, in some cases reaching high frequencies at the population level. Recent analyses have
indicated that it arose multiple times in the Felidae, with three different
species exhibiting unique mutations associated with this trait. The causative
mutations in the remaining species have so far not been identified, precluding
a broader assessment of the evolutionary dynamics of melanism in the Felidae.
Among these, the leopard (Panthera
pardus) is a particularly important target for research, given the
iconic status of the ‘black panther’ and the extremely high frequency of
melanism observed in some Asian populations. Another felid species from the
same region, the Asian golden cat (Pardofelis
temminckii), also exhibits frequent records of melanism in some
areas. We have sequenced the coding region of the Agouti Signaling Protein(ASIP)
gene in multiple leopard and Asian golden cat individuals, and identified
distinct mutations strongly associated with melanism in each of them. The
single nucleotide polymorphism (SNP) detected among the P. pardus individuals was caused
by a nonsense mutation predicted to completely ablate ASIP function. A
different SNP was identified in P. temminckii, causing a predicted
amino acid change that should also induce loss of function. Our results reveal
two additional cases of species-specific mutations implicated in melanism in
the Felidae, and indicate that ASIP mutations may play an important role in naturally-occurring
coloration polymorphism.
........................
Mammalian melanism:
natural selection in black and white
,
Abstract
Two recent papers on the molecular basis of melanism strengthen the
chain of evidence linking genotype and phenotype in nature.
Research on coat colour polymorphisms in rock pocket mice from differently coloured
rock substrates provides a compelling example of the genetics of adaptation and
the serendipitous nature of darwinian selection. Mutations in one gene,
melanocortin-1-receptor, are perfectly associated with dark coat colour on
black lava. Comparative sequence analysis shows that the same gene is involved
in melanic polymorphism in some cats.
..........................
Genetics,
development and evolution of adaptive pigmentation in vertebrates
Abstract
The study of pigmentation has
played an important role in the intersection of evolution, genetics, and
developmental biology. Pigmentation's utility as a visible phenotypic marker
has resulted in over 100 years of intense study of coat color mutations in
laboratory mice, thereby creating an impressive list of candidate genes and an
understanding of the developmental mechanisms responsible for the phenotypic
effects. Variation in color and pigment patterning has also served as the focus
of many classic studies of naturally occurring phenotypic variation in a wide
variety of vertebrates, providing some of the most compelling cases for
parallel and convergent evolution. Thus, the pigmentation model system holds
much promise for understanding the nature of adaptation by linking genetic
changes to variation in fitness-related traits. Here, I first discuss the
historical role of pigmentation in genetics, development and evolutionary
biology. I then discuss recent empirically based studies in vertebrates, which
rely on these historical foundations to make connections between genotype and
phenotype for ecologically important pigmentation traits. These studies provide
insight into the evolutionary process by uncovering the genetic basis of
adaptive traits and addressing such long-standing questions in evolutionary
biology as (1) are adaptive changes predominantly caused by mutations in
regulatory regions or coding regions? (2) is adaptation driven by the fixation
of dominant mutations? and (3) to what extent are parallel phenotypic changes
caused by similar genetic changes? It is clear that coloration has much to
teach us about the molecular basis of organismal diversity, adaptation and the
evolutionary process.
....................
