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Wednesday, November 16, 2011

Misconceptions based on Phenotypical Observations


Misconceptions based on Phenotypical Observations

© Alan S. Bias
Permission granted for nonprofit reproduction or duplication of photos and text with proper credit for learning purposes only.


I think alot of the misconceptions in Guppy Genetics by hobbyists are based on observations derived from the wrong starting point.  Huh???  How can I say this being an acknowledged livestock breeder who breeds by eye?  Take a peak at the fish below and make an initial assumption on them as a breeder and keep it in mind.  Then, let us back up in time.






Most traditional livestock breeds are defined on a very narrow range of phenotype with broader emphasis on balancing unique specific traits.  The combination of which not only allowed the breed to survive in its native habitat, but also allowed the breeder farmer to do likewise.  Much like any wild species left to its own devices such as Poecilia Reticulata - The Guppy.


Purple Vienna Lower Swords in both body and fins
Too my initial dislike, I've come to the conclusion that guppy strains take the form of commercial breeds of livestock.  Most strains survive and thrive short-term based on fad.  Face it, they evolve by breeder efforts and then remain in existence from further interest by future breeders through marketing and availability.  Very few static strains are maintained long-term by scientists in labs or breeders who persist with them for many years.


The number, types and evolution of strains is in continual state of modification, much like any other commercial breed of livestock.  Here today and gone tomorrow.  Little different than women's shoes or men's ties.  In many minimal value is placed on long-term survival traits.  Modern guppy strains are often not unique in a sense of survive-ability, just expressed phenotype.   


Is this all bad?  No.  To date it has allowed for a continuing evolution in the diversity of phenotype in most of the world.  Think about it.  For the past 100 years breeding and showing of guppies has been based near exclusively on phenotype.   Those that have built in sustainability and not just the latest greatest fad will continue to influence not only further development, but our understanding of the genetics behind it.


Green Vienna Lower Swordtail with yellow finnage
Complex modern guppy strains are often the product of  not only sex-linked traits, but in combination with several autosomal traits.   Is it possible to create and maintain diverse & often delicate phenotypes as strains with built in hardiness?  The answer should be, Yes.  To do so one has to abandon the concept looking at a guppy initially, if not solely, from the standpoint of phenotype.  Ah,  I did it again.   


I am a livestock breeder.  A traditional one at that.  As such I breed by eye and experience.  The experience is an accumulation of knowledge passed down from others and first hand, in conjunction with that acquired from sound scientific exploration.  The latter more often than not the result of others efforts.  Face it most hobbyists, myself included, lack the dedication to implement a breeding program based on scientific method.  Much less document and analyze the results by true scientific principles.



Green Vienna Lower Swordtail with Asian Blau & yellow fins
Good breeders will always breed by eye and intuition.  Successful breeders of stock throughout history have done so.  Of late I also incorporate much more acquired scientific knowledge into the decision making process.  To borrow a coined phrase of another guppy breeder, one must become " A Guppy Designer."  Did these early stock breeders do the same?  Yes, they did without setting out to do so.  The difference is they were fewer in number and likely had a natural ability to do so in a time of limited scientific knowledge.  This through the power of observation, trial and error.  A practice the continues to this day and will do so into the future.  It is an integral part of livestock breeding.  We are in the business of genetic manipulation.  Not the creation of, as the genetics are already in place.


Green Vienna Lower Swordtail with blue peduncles & yellow fins
A breed standard is usually based on expressed, or more often visualized phenotypical traits and has its merit.  It allows for fixed descriptors that are easily interpreted by all breeders.  A good starting point with some common terminology.  Inadvertently, it is also where problems start to arise.  We do not all see color in the same way.  We do not convey in expression what we see in the same way.  We also do not light our fishroom in the same way.  Then, we send our fish to shows that are rarely lit in the same way.


A breeder must be able to develop an understanding of the basis of guppy genotype.  Not only for color and pattern, but also for less visible traits.  These would include fertility, disease resistance, longevity, docility to name but a few.  By doing so you will be able to not only understand how your particular strain evolved, but also how to maintain and improve upon it.  Modern guppy strains are far to complex to do otherwise.


Purple Vienna Lower Swordtail with Asian Blau & yellow fins
Often a hobbyist bases decisions on observations of a specific phenotype and not what genetic design it took to create it.  This perception is often instilled by show standards that in effect ignore the principles of genetics.  A sort of "what you see it what you get" approach.  After many years of breeding largely to a set standard for swordtails I found my fishroom in a state of stagnation.  Though always reserving 10-20% of my tanks for exploration, far too many fish were simply being culled on the basis of not meeting standards.  Little improvement in strains and much more emphasis put on trying to just maintain and produce a couple good fish to show next year.


Grey Bodied Vienna Lower Swordtail female with & yellow fins
About 10 years ago I decided to take a different approach and let the genetics decide much of when, where and how my fish evolved.  To start with I made a drastic decision to reduce not only the type of strains I raised, but the number.  With only 60 tanks at the time I saw no other practical approach.  These days I am only running 40 tanks and even larger collection of genotype.  Largely Vienna Emerald Green (VEG) and Schimmelpennig Platinum's.  In part compatibility of females has allowed for  a reduction in the number of tanks.  
  
At some point a balance must be maintained to allow for selection of breeders that will produce, sustain and improve upon existing strains when attempting to create new ones.  A balance that derives from genetic understanding combined with a breeders eye in effort to produce not only beautiful phenotype, but viable strains with built in hardiness and disease resistance.


Green Vienna Lower Swordtail with Asian Blau & yellow fins
That brings us back to the initial intent of this article.  Based on genotype how would you describe the fish in the very first photo?  Without some understanding of genotype it would be very easy to declare a host of color descriptions and possibly assume the result of a hybrid litter.  These fish will breed true to their type.  All are gold (blond) or grey  in either green or purple body with about half showing the effects of autosomal Asian Blau (Ab) .  While they may be just as diverse in phenotype as genotype they are still basically all one in the same fish.  In fact, siblings from a single litter in a line of my Vienna Type Lower Swordtails.


Over a decade ago I set to undertake a better understanding of the genetics involved in my fish.  A process that is ongoing.  The knowledge gained has  produced a diversity of type in homozygous or heterozygous states.   Resulting in a much greater stability in the fish.  By doing so I hopefully will have created strains that exist into the future.  In a more static state, that mimics a time of traditional breeds and not just a fad...


Green Vienna Lower Swordtail with Bar & yellow fins


~~~  Often the most overlooked tool available to a breeder is an exchange of knowledge and the ability to consider what is offered by others without prejudice based upon your own knowledge.  Then let things stand or fall on their own merit or lack thereof  ~~~

Thursday, November 3, 2011

Hemiray Bifurcation and its effect on swordtail caudal selection...

Hemiray Bifurcation and its effect on swordtail caudal selection...


© Alan S. Bias
Permission granted for nonprofit reproduction or duplication of photos and text with proper credit for learning purposes only.


Hemiray Bifurcation can quickly be defined as:  "A division or fork in the rays of male and female  guppy fins."


Swordtail Female with Hemiray Bifurcation evident

This is one of those topics that generates very little documentation in the hobbyist world.  In the scientific community it is just the opposite and a number of comprehensive 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 primarily with male finnage as clear &/or roundtail is the norm for females in all but a few strains.  From the start we are at a distinct disadvantage vs. broad tail breeders.  The simple 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 small, thin & short.  These having evolved over countless generations with well defined characteristics into rigid gene complexes.  Then we attempt to force not only  lengthening, but thickening in the process.  In the end retain a distinct point while encompassing an increased number of colored hemirays at maturity.


Bifurcation and effect on fin edge
The problem with this desired end result stems 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 complex through the eons to maintain a well defined shape and structure.  Fairly smooth edges and round in most fins.  Though, points are considered normal as evidenced in the shape of vent fins and small swords in otherwise round caudals.  One might say, "Evolution has made 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 100 years.  Not only do we attempt to force modifications into color & pattern, but also fin shape & extension.  For most of us this is limited to a number 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 make decisions as a breeder based on the influences of Hemiray Bifurcation.  At first the process of enlarging a naturally occurring fin type, ie swordtails, seems like it would simply 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 simply trying to use extension genetics to force more growth into hemirays already part of an occurring tail shape.  Or are we?  






Type 1 Swordtail
Type 2 Swordtail
This is where the bifurcation comes into play.  It is the root cause that will lead to a breeder culling many of the Swordtail males 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 makeup of swordtail guppies is still the topic of hot discussion and alot of speculation with breeders around the world.  From my experience Swordtails are comprised of two distinct types.  Type 1, in general, result from several genes (more likely groups of genes) either individually or in complex to include Elongatus, Aureus, Lineus and Armatus.  Producing not only Top & Lower Swords, but also Double Swords as evidenced by those who exhibit an imbalance 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 Pigmentierte caudalis (Cp).


Type 1 Swordtail showing
about 1/2 of mature length
As a guppies fins continue to grow each hemiray at a fixed point will split and fork in two.  Under normal 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 circumvent as Swordtail breeders.  How do you force a fork into a point?  The answer is you cannot.  Though, through selection you can create the illusion of a point.  In theory this should be pretty easy as we are dealing with a limited total number of hemirays.  In practice each is an independent entity with a purpose of it's own.  Through a combination of consistent selection for the best tail shape it can be done.  But keep in mind you are also trying to load balance your other desired traits for color, shape, size, pattern, growth, maternal, longevity to name but a few.  If you concentrate heavily on tail shape then these areas may suffer.  It is often necessary to utilize a breeder male that has a weaker point or lessor length.  Not only to maintain 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 many are more often "camouflaged" Lyretails that have been forced into a swordtail configuration via breeder selection to meet a standard.  Why, you ask?  It is much easier to create the illusion of a nice clean point from fewer hemirays.  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 composed of a single ray or two forming the entire outside length.  Many lines of swordtails to maintain 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 prime example are Schimmelpennig Platinum's.  Both pattern and tail shape are closely linked from a complex of Y-link and autosomal traits.  It is easily maintained as a true Lyretail and possible to create a Schim. Double Sword.  Still most of those offered by breeders for sale or exhibition as Double Swords are frequently Lyres.  Examination of which rays form the extension under magnification 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 mutation within Vienna Emerald.  As a rule VEG strains have very stable fin type.  After 10 years of breeding Schims the only hypothesis I can offer is it results from the combination of Ds and metal in the males.   



Lower Sword exhibiting weakness at bifuracations
One of the common problems 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 magnification, it is rare see a split that happens any distance before a fork.  Just at a fork or shortly thereafter is the norm.  It is often difficult to distinguish splits resulting from genetic weaknesses and those from environmental issues such as frequent fighting between males.  The prior should be frowned upon in breeder selection and preferably culled from a program.  While splits resulting from environmental issues will usually heal and continue to grow it is not without consequence on males intended for exhibition.  Hemiray growth after an injury, be it natural or surgical, follows a different course from rays unaffected.  Not only will the circumference of  rays be smaller, the natural segments of each will not be evenly paired with other rays.  Additional bifurcation is also reduced if not eliminated in damaged 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 time new color cells will migrate to the areas of new growth and darken them.


Young Vienna Type Double 
For those of your wishing to read further on Hemiray Bifurcation a number of published studies dealing with Zebra Fish are readily available.  Two I have found of interest are:


1.  Growth Control in the Regenerating Zebrafish Ontogenetic and Fin

Stephen L. Johnson* and Paul Bennettt


2.  Position dependence of hemiray morphogenesis during tail fin regeneration in Danio rerio

C. Murciano a, J. Pérez-Claros b, A. Smith c, F. Avaron c, T.D. Fernández a, I. Durán a, J. Ruiz-Sánchez a, F. García a, J. Becerra a, M.-A. Akimenko c, M. Marí-Beffa a, 


  


Breeding to a defined standard or personal goal is often
 what initially attracts us to guppies as a breeder . 
Embarking upon a genetic understanding of those fish we choose to cull
and those we decide to retain within a breeding program 
often makes the difference in breeder perseverance...