Melanin factors and colour varieties
|hypo melanism||albinism||total albinism||M-t+ factor||ino||sex-linked|
|Definition: Total albinism is the complete drop out of melanin, in the plumage, eyes and skin.
Mutation factor: t+ = tyrosinase positive. Melanine is formed in the pigment production cells. The enzym tyrosinase is needed to start the melanin production process and keep it in progress. The melanine pigment granule start as a colourless proteïne matrix. This is composed of many albumin. When one of this albumin is missing the production process deviates. Too small and deformated matrices are developing. Too little melanin granules is formed. Colouring of the granules is a problem, even when the activity of the tyrosinase is high. When the melanin grains are transported to the feather they do not influence the colour of the plumage at all. You can see the grains with the electron microscope only. The eye colour is red.
Colour varieties: .Colour varieties are: albino, lutino and rubino..Alba(Greek)=white. Luteus (Greek)=yellow. Rubor (Latin)=red. Some examples are: Albino Turdus merula , lutino Budgerigar, lutino Splendid, rubino Galah, rubino Bourke's parrot.
|hypo melanism||albinism||total albinism||M-t- factor||ino||recessive|
|Mutation factor: t- = tyrosinase negative. Colourless matrices develop. There is no oxidation of melanin grains. The colourless matrices are transported to the feathers and the retina of the eye. The effect of colourless matrices on the plumage is nihil. All brown and black melanin is prevented. The cause is the inactivity of the enzym tyrosinase.
Colour varieties: There are ino's in some bird species: Lutino Elegant, lutino Redrump, etc.
|hypo melanism||incomplete albinism||partial albinism||M-p factor||edged||recessive|
|Definition: Partial albinism is a partial drop out of melanin production with a pied colour variety as result.
Mutation factor: p = pigment production cell. Van Eerd suggested that the possible cause is the destruction of pigment production cells by overproduction of melanin granules. In the beginning melanin is transported and deposition in the growing feather takes place. Then the production cell burst. Further melanin deposition is impossible. This can be the reason that the tips of the feathers are pigmented and the remains of the feather becomes no melanin at all. This we see in the wing feathers and the tail. The loss of melanin pigment is variable. This can be slight. The only sign is found in the flights. The loss can be strong. The whole back, wings and tail is without melanin pigment with exception of the feathertips and pigmentation of the head. The eyes are coloured normal like all pied colour varieties. The inheritance is recessive. More males than females are born.
Colour varieties: The "gezoomde" Bourke's parrot. The name gezoomd (Dutch) can be translate by edged. Some examples: Wildtype edged, Yellow back edged, Yellow edged with a red suffusion (Aprikot)
Remark: The spangle Budgerigar is not the same colour variety. The melanin wing pattern is different. The mutation factor is herediting dominant.
|hypo melanism||incomplete albinism||partial albinism||M-di factor||opaline||sex-linked|
|Mutation factor: di = distribution. Beckmann (1966) describes the opalin colour variety as change of the distribution of black melanin in a part of he wing pattern and the undulation pattern of the hind neck and upper back (saddle). The transport means, the dedrites and the enzyme myosine are normal. He describes the distortion of the pattern as a change in the distribution of the black eumelanin. The margins of the wingcoverts become the colour of the body, because the remove of the melanin in the cortex some space is made for psittacine pigment . The white under wing band is broader than normal. The loss of eumelanine beginning by the entachment of the feather at the bonestructure till the half of the feather is characteristic of all opaline varieties. A second white band can be formed in the same way in the underwing coverts. The eye colour is normal.
Colour varieties: Opaline budgerigar in different colour series. The yellow and red opaline Turquoisine, the rose, red and yellow opaline Bourke's parrot etc.
|hypo melanism||incomplete albinism||schizo-melanism||M-t- factor||phaeo||recessive|
|Schizo-melanism is the total loss of one melanin pigment, the eumelanin or the phaeomelanin, with preservation of the other melanin pigment.
Phaeomelanin does not exists in parrots. We find this in finche species like the canary. But the mutations are interessant for parrots breeders too because there are a lot of parallel mutations.When there is less activity of tyrosinase, the eumelanin production cells produce only colourless matrices. These are deposited in the feathers, but they do not have any effect on the colour. The pheomelanin production cells are still producing coloured grains. Then the phaeo colourvariety comes into being. The colour of the eye exclusive determined by eumelanin. So the eye colour is red.
Steiner named this devision of the two melanin pigments, visible in the plumage schizo-melanism. The mutation factor is t negative.The inheritance is recessive.
Colour varieties: Phaeo canary, etc.
|hypo melanism||incomplete albinism||schizomelanism||M-t+ factor||satinet, isabel||sex-linked|
|Matrices for the production of melanin granules are formed in the pigment production cells. These matrices are made of proteins. When an albumin fails the formation of matrices is disturbed. The format of the grains is decreasing. There is a deformation of the form of the grains. The amount of grains produced is decreased also. Compared with eumelanin granules with their fixed form, phaeomelanin is much more vulnerable for change in form and format. The activity of tyrosinase is higher than normal. The influence of the higher level of activity of tyrosinase cannot compensate this. The plumage is colouredby the eumelanin grains only . The colourvariety of the canary is the satinet. This is a kind of albinisme also. The mutation factor is named t positive. The inheritance is sex linked.
Colour varieties: Satinet canary, etc.
|hypo melanism||incomplete albinism||leucism||M-s factor||pied||dominant|
|Leucism alters the deposition of the melanin. Normal pigmented feathers or part of feathers are complete free of melanin pigment. Leucos (Greek) = white.
Mutation factor: s= skin. According to Mutavi, the skin area, where the feather follicle is developing, is changed. Deposition of melanin pigment becomes impossible. Some pigment free areas come into being. The eyes are coloured normal.
Colour varieties: We know some different pied colour varieties in the Budgerigar. The pigment patterns are different. Beckmann describes 1-factor and 2-factor Dutch pied and Australian pied with a band around the belly. The yellow black eyed is probably a combination of Danish pied and Dutch pied, a combination of the cumulative effect of the recessive Danish pied factor and the 2-factor dominant Dutch pied factor.
|hypo melanism||incomplete albinism||leucism||M-g factor||pied||recessive|
|Mutation factor: g = germ cells. There is a reduction of melanin pigment production. According to Kop the reason is found in a shortage of germ cells. Some feathers stay without pigment production cells because no germ cells arrive. At this places no pigment production takes place. The myosine enzyme for transport is functioning normal but there are no granules to deposit.
Colour varieties: An example is the Danish pied variety of the budgerigar. It is called recessive pied. This pied was found in the Bourke's parrot also. The psittacine pigments are developing normal. At the places where no melanin is found the colour of the feathers is red, yellow or white, depending of the possession of psittacine pigments of the parents. Thusfare no development of a strain of this pied colour variety of the Bourke is reported in Holland.
|hypo melanism||incomplete albinism||dilutism||M-a-factor||bronze fallow||recessieve|
|Dilutism is a equal decrease of the melanin colouring of the plumage.
Mutation factor: a = amount of melanin grains is decreased. The activity of the tyrosinase is decreased and less than normal. This results in a change of the eye colour and the colour of plumage, skin and horn parts. Beckmann: The fallow colour variety has red eyes and shows bleaching of the plumage because of decrease of the amount of melanine granules. The decrease in the barbules is 50% and in the barbs 75%. Mutavi: There is a relationship between the M-a factor (fallow) and the recessive M-t- factor ( ino). The difference between them is the activity of the enzym tyrosinase and the amount of melanin grains that is produced.The bronze fallow (fallow type 1) is bleached and has red eyes.
Colour variety: In the description fallow varieties Mutavi starts from bird species with black melanin, like the Neophema. The change of the colour of melanin granules goes from black to ashgrey, greybrown, brown to lightbrown. The fallow type 1, is called bronze fallow. Martin presents a picture of the bronze Bourke's parrot (pg. 77). But the fact that the colour of the Bourke is brown is neglected by Mutavi. The only change in colour is from brown to sand coloured brown due to a reduction of quantity.
|hypo melanism||incomplete albinism||dilutism||M-f factor||pale fallow||recessive|
|Mutation factor: f= form and format. The form and format of the melanin grains is abnormal. In the production of the melanin grains there is a quality problem. The colourless matrices of proteins are not of good quality. The developing of the melanin grains and the colouring of the grains takes place but they are to small and deformated. The colour of the grains is grey-brown.When they are deposited the colour of the feathers is pale, compared with the wildtype. The eyes are red. There is a relationship between the sex-linked M-t+ factor and this M-f factor. The resemblance is that he activity of the tyrosinase is increased and higher than normal. The difference between them is that there is production of coloured melanin grains but of less quality.
Colour varieties: This change of the melanin production causes a pale fallow colour variety with red eyes. Mutavi named this colour variety fallow type 2, or dun fallow. The Bourke has no black pigment. The name dun fallow cannot be used fot a Bourke variety.
|hypo melanism||incomplete albinism||dilutism||M-r factor||pastel||recessive|
|Mutation factor: r = reduction There is a strong reduction of the amount of melanin grains. It gives an equal bleaching because of the decrease of the amount of melanin grains in the plumage. The form, format and colour of the grains is normal. The colour of the eye is dark. Beckman who studied cross sections of feather barbs estimates the reduction in the barbules 50% and the reduction in the barbs about 100%. The bleaching of the plumage of the pastel variety is stronger than the fallow. Such a strong reduction of the melanin makes that the psittacine pigments manifest themselves clear in the plumage. The plumage is much brighter than in the fallow variety.
Colourvariety. The Dutch yellow pastel Bourke has red eyes. Beckmann wrote that this variety, developed in the fifthies in Holland had dark eyes. Maybe breeders tried to develop a much more yellow variety by combining two factors fallow and yellow. But this is a supposition. There is a red pastel Bourke also. These is a little bit darker than the yellow pastel and has red eyes too.
|hypo melanism||incomplete albinism||dilutism||M-s factor||light||recessive|
|Mutation factor: s = slight reduction of the melanin.There is a minimal bleaching of the plumage compared with the wildtype. The exact cause is not studied thusfare. The bleaching of the plumage is even in the whole plumage.
Colour varieties: Martin named this colour variety faded. In Europe this minimal bleaching was called recessive isabel. The name isabel should be used only for the schizo-melanistic loss of the phaeomelanin. Phaeomelanin is not a melanin pigment found in parrots.
|hypo melanism||incomplete albinism||dilutism||M-de factor||silver||dominant|
|Mutation factor: de = dendrites. There are two means of transport of the eumelanin grains, the dendrites (long processes) of the production cells and the enzym myosine. Normally the dendrites grow out of the pigment production cells and reach the growing barb.When the dendrites are deformated less melanin grains is deposited in the growing feather. Martin: The possible cause is the deformation of dendrites, one of the means of transport.
Colour variety: Martin reports of the silvergrey cockatiel. He named this dominant dilute. (pg75) The grey back becomes silvergrey. The eye colour is black. The colour is not equal everywhere. And this can refer to the fact that distortion of the processes of the pigment production cells is not equal everywhere.
|hypo melanism||incomplete albinism||dilutism||M-w factor||suffused||recessive|
|Mutation factor w = wing pattern. There is an equal reduction of the eumelanin in the wing pattern. The pattern becomes lighter and dilutes. Beckmann reports about the grey wing and the white wing budgerigar. The second black band of the wing coverts, de black undulation in backside of the head, hindneck, wings and tail feathers are influenced. The black undulation becomes grey and very light grey. There is a difference in melanin reduction. In the greywing there is a reduction of 50%. Melanin reduction in the white wing and yellow wing is ca. 100%. In the suffused only a little bit melanin is left. This causes a faint pattern. Mutavi explains that the grains are formed normally but there is a transport problem. The grains are cluttered and are forming macro grains. This is not seen with the bare eye.
Colour varieties: Budgerigar greywing, whitewing and suffused. The Englisch term: clearwing is used for white wing and yellow wing as well.
|hypo melanism||incomplete albinism||dilutism||M-o factor||cinnamon||sex-linked|
|Mutation factor: o = oxidation. There are some phases of oxidation of the eumelanin grains. When the last phase of oxidation is missing, brown granules are produced in stead of black grains. This brown coloured plumage gives a cinnamon coloured variety. The overall colour is a bit lighter than normal. The eyes are red in the beginning . After the moult they are darker than before. The cause is the activity of the enzym tyrosinase.
Colour varieties: cinnamon Turquoisine, cinnamon Scarlet-chested, etc.
|hyper melanism||total melanism||nigrigism||M-ti factor||black||recessive|
|Hyper melanism is a hyper function of melanin production. Much more melanin grains are produced and deposed in the feathers.
Mutation factor: ti = total increase of melanin production There is an abnormal enhancement of the amount of melanin grains and distribution in the whole plumage.
|hyper melanism||partial melanism||acromelanism||M-pi factor||black face||recessive|
|explanation: pi = partial increase of melanin production There is a abnormal increase of melanin production and deposition in part of the plumage. Some examples are: black face Budgerigar,|
Altering of the production, transport and deposition of melanin grains
In the zone of differentiation, in the base of the feather follicle, is decided if the germ cells grow out as an eumelanin or a phaeomelanin production cell. The phaeomelanin granules are smaller and more amorf than the eumelanin grains. For the production of pheomelanine, cysteine an amino acid, is needed. Both melanin pigments need tyrosinase for starting and keeping the melanin production in progress . But there is a difference. The production of phaeomelanin is less dependent of the enzym tyrosinase.
Schizomelanism is found in birds with both melanins, the eumelanin and the phaeomelanin. In finches the same mutation factors of the tyrosinase t- and t+, are found, they belong to albinism. But this was discovered later because of the remaining colouring of the plumage by the other melanin pigment.
The inactivity of the tyrosinase ( M-t- factor) causes colourless eumelanin matrices transported to the feathers. The eumelanin is gone from the wing and tail feathers. The red brown phaeomelanin granules are colouring the plumage. A fox brown phaeo colour variety comes into being.
The M-t+ factor means that a lack of a proteine causes deformed and small matrices. The matrices of the pheomelanin are more vulnerable because they are small and more amorf. No phaeomelanin grains are deposited in the feathers. Kop named this the first reduction factor. The colour varieties are named agaat and isabel. When the reduction of phaeomelanin goes further till about 100% the colourvariety is named satinet.
Dilutism as a classification category
Overlap between melanin and psittacine categories has to be avoided. Ditutism is used as a M-categories only.
Namegiving of the Bourke's mutations:
The Bourke is an exception to the rule that parrots have black eumelanin. In the classification of the Bourke's mutations the different possesion of colouring elements of the Bourke's parrot compared with the other parrot species is been neglected. I give some examples of the eumelanin:D
The Bourke has brown eumelanin pigment. Change from black to brown (cinnamon), reducing to brown of grey family pigments (bronze fallow) black reducing to grey-brown (dun fallow), reducing the amount of black pigment (faded) are definitions that don't fit to the Bourke's parrot. The description of two forms of dilute, yellow pastel and green suffused fits to the green turqoisine but not to the Bourke. The Bourke has brown eumelanin and red and yellow psittacine pigments.