A Unique Guppy Strain By Chris Ng The guppy has attracted many hobbyists due to their vibrant colours and ease of keeping. From its humble beginnings, the guppy has been developed from a small sized fish with a few colour spots to today’s varieties of fascinating patterns and colors. It is amazing that the guppy has so many different forms, attributed to the genes that existed in them. One of the aims of breeding guppies is to develop a strain further and perhaps create a new strain. These aims are not easy to execute and requires a good eye to recognize the traits to keep and those to eliminate. When a mutation or recombination of genes occurs, which is likely to be found in only a few fishes in a batch of fry, these abilities are the key to developing a new strain. In this article, I like to share a variety that is created due to a good eye and also by a stroke of luck. My friend, Jerry, had developed this fish below… Mature Emerald Male. Photo Credit: Jerry He had nicknamed this strain as Japan-blue emerald.                         Characteristics This variety's base colour is blond, which accentuates the soft, pastel-like colours. The uniqueness of this variety is in its shimmering scales of the males. Under different light angles, its coloration morphs… silvery-blue or green or turquoise or yellow. This is what fascinated many people when they first saw it. This attribute also makes photographing it difficult, as it is hard to capture its true colours. The females have a shimmering sheen on them too, only that it is noticeable if you look closely. This is a small-sized (around 4cmTL) and slow-growing strain. It takes around 6-8 months for it to grow to its full potential, in short, for the body size and finnage to grow fully. Its colouration develops fully around the 3month old mark. Young male & female. Photo Credit: Jerry               History Jerry created this fish from a unique male thrown out by his Japan-blue grass strain, which he had kept for 2 years. This particular male is a shining yellow fish, i.e. the body is covered with gold scales; coupled with its blond base colour, it is extremely spectacular, hence his desire to breed this male. However, It is hard to track the genetic background, as Jerry does not keep any written records. Original JB male (albino) Photo Credit: Jerry           Jerry mated this male to his mother. For the following generations until F5, he did sibling crosses, which consists of direct brother-sister crosses and also half-sibling crosses. Then he did a back cross when the colouration of the strain became consistent. In the earlier generations, a mix of this strain and “wild-type” Japan blues were produced. This aspect is attributed later to the selection of females. Certain females produce Japan blues only; others produce emeralds. However, in mating these Japan blues, a phenotype, which can be described as full Japan blue, is produced, the males have an even, intense blue colouration. Currently, Jerry’s strain is at the F8-F10 stage. A discussion on Emerald Based on the appearance of JB emerald, there are several traits that can be observed. The distribution of iridophores is particularly dense throughout the body of males. In typical Japan blue strains, the iridophores concentrated on the posterior half appears to be blue; this form of blueness is due to the Tyndall Effect. The blond gene affects the melanophores located beneath the blue iridophores found in the half-black region, thus the blue appears lighter, in fact, and the effect of the melanophores is minimized. In this strain, the location of the iridophores seems unique, as various hues of reflected colours- white, blue, and green, yellow are visible throughout. The distribution of highly reflective “lime-white” iridophores around the gill covers and body of the females suggests that its similarities to the colouration of the males. Iridophores around the female’s head Photo Credit: Jerry                 In the aspect of colour pigments, the xanthophores and pteridines are present in this strain. Noticeably, red is minimized to a red bar by the head and covered up. This strain can be simply described to have 2 key colours -yellow and blue. The emerald’s colouration is a matt yellow to a light blue from the head to the caudal peduncle. Apparently there is a concentration of xanthophores at the head region and its distribution seemingly reduced after it passes the mid-body of the male guppy. Visible spectrum The effect arising from the combination of pigment cells and iridophores appears familiar; In fact, it presents a continuum reflecting the colours around the middle range of the visible spectrum. This is interesting because this shimmering effect originated from a single fish with a proliferation of reflective iridophores. A microscope will be of great help in identifying the makeup of its cells and offering more insights into this strain. In Jerry’s endeavour to improve this strain, particularly in the growth rate, size and finnage, he had done some crosses with German yellow tuxedos and Moscow blue. From these crosses, the peculiarities of this strain can be seen. Emerald X Moscow Photo Credit: Jerry Emerald X German yellow tuxedo Photo Credit: Jerry                   There are black spots above the anal fin. This trait, existing on some of Jerry’s original Japan-blue males, is strongly Y-linked. These spots couldn’t be seen in emeralds, which imply that the reduced melanophores are suppressed by the iridophores. The dark finnage of Moscow blue parent is not evident in the cross. There appears to be a negative relationship between these 2 types of colour cells. The emerald-Moscow males have the same parents but there is a difference in the display of their Japan –blue trait; neither of them has a blue shine, a likely possibility is that the Japan- blue gene has a co-dominant nature. The red bar by the head is revealed in the tuxedo outcross but in most specimens, it is covered up by the iridescence of the scales. Noticeably, there isn’t a major effect on the size and shape of the finnage. The resultant offspring has a pastel blue on the half black area and yellowish highlights around the chest region. The Moscow strain used is a big-bodied, large, wide finnage line but surprisingly, the resultant offspring are small-sized and have small round finnage, suggesting that the gene relationship between Emeralds and Moscows could be complex. The original traits such as the red head bar, the black spots remain Y-linked. In addition, the outcross had shown that the Japan-blue remains Y-linked and that the Japan blue gene shows co-dominance with other colour cells. One trait, which the original Japan-blue strain is absent of, is the green-yellow iridescence around the chest region. This trait is evident on all the males of the outcrosses and also in emerald females. Subsequent generations will reveal the inheritance pattern. Conclusion In the pursuit for perfection, it will be good to stop and smell the roses. Although Jerry’s aim to create a full colour guppy did not succeed, he had identified a new development during the process and modified his path. Observing the development of our beloved guppies in a wider perspective does have its benefits. Part of my discussion about Emerald is by piecing bits of evidences and linking them up into some hypothesis, hence the information only provides a general idea of its genetic make-up.