The Cellular Expression and Genetics of an Established Polymorphism in Poecilia reticulata; “Purple Body, (Pb)” is an Autosomal Dominant Gene

Modification of wild-type carotenoid orange and pteridine red coloration and spotting of male ornaments in both wild populations of Poecilia reticulata (Guppies) and modern Domestic Guppy strains by the Purple Body gene has long been overlooked in research articles and little understood in breeder publications. This modification is commonly found in wild-type Poecilia reticulata reticulata populations from numerous collection sites and has been photographed but not recognized in these collections. It is non-existent or near absent in collections taken from variant populations of Poecilia reticulata wingei. We identify and determine the mode of inheritance, cellular and phenotypic expression by the Purple gene in these stocks. The Purple Body color pigment modification is a distinct polymorphism in wild P. reticulata reticulata populations. Its existence suggests multiple benefits that satisfy female sexual selection preferences, and minimize or reduce potential predation risks. Photographic and microscopic evidence demonstrated that Purple Body is a normal polymorphism in wild and domestic guppies modifying color pigment regions. Purple Body is inherited as an autosomal incompletely dominant trait.


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Pb modification, zygosity dependent, removes certain classes of yellow-orange-red color 186 pigment over silver iridophores or white leucophores. The term we use here, "white 187 leucophore", refers to a pigment cell type that was extensively studied both structurally and 188 biochemically in Takeuchi (1976) and identified as a fourth chromatophore type. However

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Kottler, et al (2014) were not able to confirm the presence of leucophores based upon their 190 physical structure. We were not able to determine whether the cells we observed were white 191 leucophores or white iridophores, but will continue to refer to them here as leucophores.

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Pb modifies "other existing" color in both body and fins, thus suggestive of being a "full 193 body" modifier, in homozygous fashion. Dark red pteridine color pigment does not seem to 194 be modified by Purple Body in fins lacking an underlying silver iridophore or white 195 leucophore pattern. Modification by Pb seems limited predominantly to wild-type orange 196 color pigment; i.e. that which also contains yellow carotenoids in addition to red pteridines, 197 over an iridophore pattern.

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Pb is always found in all-purple fish, but is not by itself sufficient to produce the all-

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Additionally noted is an increase and modification in existing melanophore structure and 251 populations.

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Homozygous Pb in both wild-type and domestic individuals alters all orange spots found 253 in the body and in finnage to "purplish-pink". Thus, Pb should be considered a "full body" reveals that ectopic melanophore dendrites are often extremely extended (Fig 5). This 282 occurs either as the result of direct modification by Pb, or indirectly through interactions as 283 a result of xanthophore reductions or removal (Kottler, 2015). Overall dendritic 284 melanophore structure is of a much "finer" appearance as compared to non-Pb. Modified 285 melanophores are more often linked together in "chain-like" strings (Fig 5)  individuals, reveal that dendritic arm structure is extremely extended and finer in 346 appearance (Fig 7). Dendrites are linked together in "chain-like" strings intermingled with

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Two distinct observations are offered based on early coloration. First, violet and blue 373 iridophores appear "randomly collected among themselves" in similar fashion (Fig 9), as 374 opposed to later mature coloration in which violet and blue iridophores are arranged 375 together in "joined alternating color" groupings in dissimilar fashion. This shows that 376 coloration is nearly complete, while migration to their final location is not. Second, 377 melanophore shape is predominately corolla or punctate in early coloration (Fig 9), as  homozygous condition removes red color pigment (Fig 12-14). leaving an underlying "circular ring" of violet-blue iridophores intact. As previously noted,

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Pb in itself has little or no effect on erythrophore populations. Albeit, Pb modification results

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Temperatures ranged from 78°F to 82°F. Virgin females were used in all crosses. Virgin

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The evaluation of color and tail neutral females in wild-type is limited to evaluation of 502 increased violet-blue iridophores along the anterior lateral line. While reliable to a high 503 degree in homozygous Pb specimens, this has not proven a reliable tool for evaluation in 504 heterozygous Pb females.

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In Fig 15,    an autosomal location seems more likely. We realize that a very large sample size would be 611 needed to completely eliminate (or affirm) the sex chromosomal location of Purple Body.

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But the autosomal location of Purple Body is the most likely conclusion.

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Note: For full description of all test breeding's, parental and offspring photos see 615 supplementary appendices: S1

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Further study in the field should show that Pb is an integral part of wild P. reticulata between and beneath dendritic structures, forming similar chromatophore units (Fig 17). A 721 similar association has been shown in general imagery of recent research ( Fig. 1 and Fig.   722 6c, Kottler 2014). Whether this represents increased population numbers or density, or Prior studies heavily focused on the shallow water habitat of Guppies, subject to UV 747 radiance from the sun. None had attempted to assert a direct correlation between UV 748 reflected color, pattern and vision, mate choice, and individual preferences. Several of 749 these earlier studies re-affirmed courtship activity was at its highest during dawn and dusk.

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Smith concluded that there was no discernable UV preference between early morning 753 simulations 1-3 hours after lights on or 1-6 hours, with 1-3 being indicated as traditional 754 testing time by researchers (Smith 2002). This is worthy of note for at least two reasons: angle sunlight non-Pb appears "brighter orange", as compared to Pb appearing "darker 818 orange" (Fig 18B), and is favored as a sign of male fecundity.

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Of five opsins isolated in more recent reticulata studies, two were identified as 847 "maximally sensitive" in producing SWS vision. Of more importance in consideration of 848 potential Pb biotic benefit from modification, it was found that C. frenata was notably

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"insensitive" to UV light, being unable to discriminate hues in the lower part of the visual 850 spectrum (Weadick 2012).

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The predatory prawn (Macrobrachium crenulatum) has been shown capable of UV

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To avoid predation, M. crenulatum, is primarily a nocturnal feeding species (Bauer 2011) 865 that in turn preys heavily on P. reticulata (Magurran 2005). Orange spots on the pinchers

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It is an autosomal trait capable of modifying extent color and pattern found in a 903 population and across populations, acting as "a permanently protected reservoir available in 904 the female population in which, whether they are present in heterozygous or homozygous 905 condition, they are sex limited and will not be phenotypically expressed" (Haskins 1951).

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The Pb gene is partly protected from strong selection by its presence in females, where it is

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Yet, current microscopy reveals female coloration is not solely limited to counter-gradient 927 expression for the benefit of camouflage.

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Females possess all classes of chromatophores, and are subject to Pb modification for 929 expression of near-UV reflective qualities as well. MLH was correlated as a "significant 930 predictor" in relation to overall area of spotting; it was not linked to total numbers of spots.

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The end results favored "genome-wide heterozygosity" based on individual markers for  of Pb (Fig 19).  genotype is now demonstrated to be a potential female study marker in heterozygous and to color and/or pattern as a whole as suggested by Kottler (2014). A mechanism is 1100 identified by which Pb is capable of balancing overall color and pattern polymorphisms, in 1101 turn providing fitness through heterozygosity in diverse complex habitats. We hope that

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Purple will be mapped to its linkage group.

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Throughout this study a recurring thought has consistently arisen in the minds of the

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For purposes of this study low resolution photos were often preferred over higher