iHerp Australia Issue 6 - Page 5

Chimera (kī-mîr′ ə, kĭ-) n. A hybrid, female creature composed of part lion, part goat and part snake (Greek mythology); any fictitious monster consisting of disparate elements; a harbinger of doom. T he fearsome fire-breathing chimera of antiquity first appeared in Homer’s Iliad, and apparently tormented the region of Lycia until it was ultimately dispatched with a lump of molten lead. The origin of this legend may be traced to a series of vents in a hillside in southern Turkey that to the present day emit burning plumes of methane, and were important landmarks for ancient sailors. Later, the title of chimera became applied to any fictitious animal composed of a mismatch of body parts. More recently, geneticists appropriated the term to describe a rare state in which a single organism contains cells of different genotypes, the expression of which may give rise to a heteroge- nous appearance. The most familiar example to anyone with an interest in herpetology is the ‘Paradox’ albino - but these stunning, highly-prized animals could hardly be described as monsters! This article was inspired by the recent birth of a beautiful, brand new Paradox albino Spotted Python (Antaresia maculosa). iHerp Australia then canvassed some of the handful of breeders around the country who have been lucky enough to produce and work with Paradox snakes. The more research we did, the bigger the story grew, assuming almost epic proportions - as did our collection of incredible photos - but becoming increasingly fascinating in the process. Before introducing some of these amazing creatures, it is worth briefly examining the nature and inheritance of this condition, which is often shrouded in as much mystery as the original chimera of the Iliad! should not occur. How does this happen? One explanation is that Paradox albinos are true genetic chimeras that result from the fusion of two different zygotes into one organism. So they contain both normal and albino genotypes, which create a ‘patchwork’ phenotype. Depending on which genotype creates the gonads, or sex organs, it is therefore possible that Paradox albinos will produce gametes containing either the recessive albino allele, or the ‘normal’ one. In other words, they are capable of producing albino or normal-looking progeny. Since it is due to the chance merging of two fertilised eggs, the Paradox condition created under these circumstances is not genetically heritable. A small number of Paradox albino Darwin Carpet Pythons have been around for a few years here in Australia, and in late 2016 K Brothers Pythons (Troy and Denver Kuligowski) produced a fascinating YouTube video in association with Morelia Magic (Wayne and Deb Larks) that examined the issue of a pairing of two Paradox albino specimens. Similar numbers of albino and het hatchlings were produced, as may be expected from a conventional albino to het pairing, thereby supporting the notion that this form of Paradox is a chimera originating from the fusion of two eggs (you can view the video here: https:// www.youtube.com/watch?v=jFNrnlk6ogM). . However, some pairings tend to throw the odd Paradox on a regular basis, and breeders in this country and overseas (the latter principally working with Paradox albino Ball Pythons and sand boas) have noticed a degree of heritability. This may be explained by an alternative theory for the creation of a Paradox phenotype; spontaneous loss or gain of function caused by mutation of the albino/wild-type alleles. Sounds complicated, but let’s look at a couple of simple examples. Take an embryo that is het for albino; if the wild-type allele is rendered non-functional (or deleted) in a single cell early in development, all cells derived from this cell will behave as albino, resulting in a patchy appearance. A similar effect could be produced in a homozygous albino by an albino allele that ‘reverted’ back to wild type (gain of function). If the gene concerned is inherently unstable, this would account for some heritablility. This is an example of a phenomenon that geneticists refer to as ‘mosaicism’, in which different genotypes exist in a single organism due to early mutation. ‘A Paradox albino exhibits areas of melanin deposition that simply should not occur .’ Albinism (derived from the Latin albus for ‘white’) is a simple recessive trait, found in all types of vertebrates, in which melanin (the black/brown pigment in skin and other tissues) is either not produced, or prevented from gaining access to the chromatophores. In mammals, which possess only a single type of pigment-bearing cell, this results in an all-white phenotype with pinkish-looking eyes. Reptiles, however, have additional chromatophores containing red and yellow pigments, as well as deposits of purine crystals that reflect light and may create an iridescent effect. Therefore, albino reptiles will not necessarily appear pure white, although they will not possess dark eyes. A paradox is a contradiction that should not normally exist, and thus a Paradox albino is an albino animal that exhibits areas of melanin deposition that, under normal circumstances, simply