Hemiray Bifurcation and its effect on swordtail caudal selection

TH U RSD AY, N OVEMBER 3 , 2 0 11 Hem iray Bifurcation and its effect on sw ordtail caudal selection... © Alan S. Bias Permission granted for nonprofit reproduction or duplication of photos and text with proper credit for learning purposes only. H e m iray Bifu rcatio n can qu ickly be d e fin e d as : "A d ivis io n o r fo rk in th e rays o f m ale an d fe m ale gu p p y fin s ." Swordtail Female with Hemiray Bifurcation evident Th is is o n e o f th o s e to pics that generates very little documentation in the hobbyist world. In the scientific comm unity it is just the opposite and a num ber of com prehensive studies have resulted in excellent publications. What is not so easily gauged and often overlooked is the effect of Hemiray Bifurcation in a Swordtail strain. The weaknesses it creates and how you should base breeder selections. As Swordtail Guppy breeders, we deal prim arily with m ale finnage as clear &/ or roundtail is the norm for fem ales in all but a few strains. From the start we are at a distinct disadvantage vs. broad tail breeders. The sim ple reason being mother-nature goes against us at every chance. Bifurcation alone creates an ever broadening of the caudal. We start with naturally occurring tail extensions that are very sm all, thin & short. These having evolved over countless generations with well defined characteristics into rigid gene com plexes. Then we attem pt to force not only lengthening, but thickening in the process. In the end retain a distinct point while encom passing an increased num ber of colored hem irays at m aturity. Bifurcation and effect on fin edge The problem with this desired end result stem s from the very nature of the processes involved in the growth of fins. As a rule a guppies finnage including caudal, dorsal, pectoral, anal and pelvic have been regulated by gene com plex through the eons to m aintain a well defined shape and structure. Fairly sm ooth edges and round in m ost fins. Though, points are considered norm al as evidenced in the shape of vent fins and sm all swords in otherwise round caudals. One m ight say, "Evolution has m ade it easy for us to keep and breed guppies as long as one stays within the confines it has established." Effect of bifurcation on round caudal The trouble is few of us as Guppy Breeders have chosen to do so over the last 10 0 years. Not only do we attem pt to force m odifications into color & pattern, but also fin shape & extension. For m ost of us this is lim ited to a num ber of established configurations in the caudal and dorsal. Exceptions would include extension genetics involved with long-fin phenotypes variously referred to as; Berlin - Geissen - Ribbon Swallow. In all instances you will still be forced to m ake decisions as a breeder based on the influences of Hem iray Bifurcation. At first the process of enlarging a naturally occurring fin type, ie swordtails, seem s like it would sim ply involve traditional breeding techniques with a sufficient number of tanks to let trial and error work its course over a number of generations. After all, we are sim ply trying to use extension genetics to force m ore growth into hemirays already part of an occurring tail shape. Or are we? Type 1 Swordtail Type 2 Swordtail This is where the bifurcation com es into play. It is the root cause that will lead to a breeder culling m any of the Swordtail m ales produced in both fixed strains and outcross. Most swordtail strains not only include a lengthening, but also an encompass an increased number of rays. To this day the actual genetic m akeup of swordtail guppies is still the topic of hot discussion and alot of speculation with breeders around the world. From m y experience Swordtails are com prised of two distinct types. Type 1, in general, result from several genes (m ore likely groups of genes) either individually or in com plex to include Elongatus, Aureus, Lineus and Arm atus. Producing not only Top & Lower Swords, but also Double Swords as evidenced by those who exhibit an im balance not only in shape, but also growth between the upper and lower swords. Type 2 is likely the result of the Double Sword gene (Ds) and a lack of Pigm entierte caudalis (Cp). Type 1 Swordtail showing about 1/2 of mature length As a guppies fins continue to grow each hem iray at a fixed point will split and fork in two. Under norm al conditions it will then continue to grow for a fixed length and again fork. This process will continue for as long as each individual fin ray grows. Regardless of shape. Herein, lies first issue we try to circum vent as Swordtail breeders. How do you force a fork into a point? Th e a n s w e r is y o u ca n n o t . Though, through selection you can create the illusion of a point. In theory this should be pretty easy as we are dealing with a lim ited total number of hem irays. In practice each is an independent entity with a purpose of it's own. Through a com bination of consistent selection for the best tail shape it can be done. But keep in m ind you are also trying to load balance your other desired traits for color, shape, size, pattern, growth, m aternal, longevity to name but a few. If you concentrate heavily on tail shape then these areas m ay suffer. It is often necessary to utilize a breeder m ale that has a weaker point or lessor length. Not only to m aintain your established strain, but more often to identify and create additional phenotypes. Lower Swordtail "pencil tail" Lower Swordtail not yet mature If you work with Swordtails long enough you will realize that m any are m ore often "cam ouflaged" Lyretails that have been forced into a swordtail configuration via breeder selection to m eet a standard. Why, you ask? It is m uch easier to create the illusion of a nice clean point from fewer hem irays. I find good swordtail caudal extension contains a larger number of colored & extended rays starting from at rays 3-5, with an increasing number all extending to the final point. The best swords are often com posed of a single ray or two form ing the entire outside length. Many lines of swordtails to m aintain length and clean points have evolved into "pencil tails" with as few as 2-3 total rays showing extension and lacking color on the interior side. Avoiding clear rays on the interior of the swords will help alleviate some issues. Lyretail In contrast many Lyretail's extension start from rays 5-7 with extension in only the next 2-3. Initial Lyretail rays can taper off into those rays that lengthen and extend to the final point, often with those on the interior reversing the process and shortening. A prim e exam ple are Schimm elpennig Platinum 's. Both pattern and tail shape are closely linked from a com plex of Y-link and autosomal traits. It is easily m aintained as a true Lyretail and possible to create a Schim . Double Sword. Still m ost of those offered by breeders for sale or exhibition as Double Swords are frequently Lyres. Exam ination of which rays form the extension under m agnification will confirm this. While the Schim . Lyres have thick rays and stable extensions, the doubles are very prone to splitting and even stray growths. What always perplexed me is why? They reportedly evolved from m utation within Vienna Em erald. As a rule VEG strains have very stable fin type. After 10 years of breeding Schim s the only hypothesis I can offer is it results from the com bination of Ds and m etal in the m ales. Lower Sword exhibiting weakness at bifuracations One of the com m on problem s that arises in a swordtail is fin splitting on the interior portion of a sword, ie the top side of a lower or the under side of a top. This results from weaknesses created where each ray forks. Having put quite a few under m agnification, it is rare see a split that happens any distance before a fork. J ust at a fork or shortly thereafter is the norm . It is often difficult to distinguish splits resulting from genetic weaknesses and those from environm ental issues such as frequent fighting between m ales. The prior should be frowned upon in breeder selection and preferably culled from a program . While splits resulting from environm ental issues will usually heal and continue to grow it is not without consequence on males intended for exhibition. Hem iray growth after an injury, be it natural or surgical, follows a different course from rays unaffected. Not only will the circum ference of rays be sm aller, the natural segments of each will not be evenly paired with other rays. Additional bifurcation is also reduced if not elim inated in dam aged rays. This is often visible in Delta strains in which ragged caudal edges have been surgically altered. The ends of the caudal are clean from new tissue growth surrounding rays that have regrown without forks. Given tim e new color cells will m igrate to the areas of new growth and darken them . Young Vienna Type Double For those of your wishing to read further on H e m ir a y Bifu r ca t io n a num ber of published studies dealing with Zebra Fish are readily available. Two I have found of interest are: 1. Gro w th Co n tro l in th e Re ge n e ratin g Ze brafis h On to ge n e tic an d Fin Stephen L. J ohnson* and Paul Bennettt 2 . Po s itio n d e p e n d e n ce o f h e m iray m o rp h o ge n e s is d u rin g tail fin re ge n e ratio n in D an io re rio C. Murciano a, J . Pérez-Claros b, A. Sm ith c, F. Avaron c, T.D. Fernández a, I. Durán a, J . Ruiz-Sánchez a, F. García a, J . Becerra a, M.-A. Akim enko c, M. Marí-Beffa a,