ΤΑ ΣΥΜΠΕΡΑΣΜΑΤΑ ΔΙΚΑ ΣΑΣ,ΓΙΑ ΤΟ ΠΑΡΑΚΑΤΩ ΑΡΘΡΟ!!!!!

[ASCCO1]

BETTAS...AND MORE
By
Dr. Leo Buss



Genetics and Show Classification
On the show Betta circuit, it is a maxim that the standards by which fish
are judged are not isomorphic with our understanding of Betta genetics.
Some classes are founded on single-gene effects on pigment (e.g., black),
others distribute the effects of single-gene into multiple classes (e.g.,
steel, blue, turquoise), and yet other show classes deliberately combine
colors known to be genetically distinct (e.g., yellow and clear).
Moreover, some pigmentation genes have no show class(es) predicated upon
their effects (e.g., black lace). The classic example of the mismatch
between genetics and show categorization is the fact that a fish carrying
the mutant allele of the opaque gene can be shown in either the opaque
class or the pastel class, depending upon whether the opaque effect is, or
is not, evident.
At first blush this may appear an untidy and unfortunate way to organize
affairs. There are, however, a number of quite good reasons why one would
not like to arrange matters on strictly genetic lines. As a simple
practical matter, if we were to create a class for every genetic
combination of even the well-known genes, we would have vastly too many
classes to deal with. Consider the numbers. With one gene, we will have
either two or three recognizably different forms, corresponding to genes
that are dominant or codominant respectively. So that we are dealing with
minimal numbers in the discussion to follow, let us imagine that genes
yield only two alternative appearances. If we designate a gene by a number
and its distinct appearance by a letter, then a single gene gives two
combinations (1A is gene 1 producing appearance A, 1B is gene 1 producing
appearance B). Now, consider a second gene. We have four possible
combinations (1A2A, 1A2B, 1B2A, 1B2B). A third gene ramifies the
possibilities: 1A2A3A, 1A2A3B, 1A2B3A, 1A2B3B, 1B2A3A, 1B2A3B, 1B2B3A, and
1B2B3B. The effects of a single gene gives 2 possibilities, two genes 4
possibilities, and three genes 8 possibilities. The series of 1,2, 3 genes
yields 2, 4, 8 possible combinations, so the general solution is the
number of combinations equals 2m, where m=the number of genes. Thus if we
were to organize show classes on genetically separable criterion, 10 genes
would yield 1,024 different show classes.
Inevitably only a handful of very specific combinations map to existing
show classes. These particular combinations are chosen not on genetic
grounds per se, but because these specific combinations of genes yield a
pleasing result. Humans like pure colors and contrasting patterns. The
show classes reflect these aesthetics. The tiny subset of vast universe of
possible genetic combinations that do correspond to show categories are
chosen because they generate the purest solid colors or those that produce
the most striking of patterns. For example, the show class for blacks
calls for the fish to be black, only black, and the blackest of imaginable
black. The ideal is never realized, but is best approximated when the show
animal has two copies of the mutant allele at the melano locus (=gene).
This genetic configuration is necessary, but not sufficient. We further
require that the animal have one or no copies of the mutant allele at the
cambodia locus, that the animal have two copies of the wild-type allele at
the "spread iridescence" locus, as well as various other preferred states
at each of the other known genes. Aesthetic criteria define the ends;
genetics provide the means.
No less compelling a reason for the decoupling of show classes from the
underlying genetics is that many eye-pleasing forms and color patterns of
Betta do not have adequate genetic interpretations. We lack a satisfactory
genetic understanding of most of the pattern variations. Pattern
variations include bicolor, the appearance of one color on the fins and
another on the body; butterfly, the appearance of two colors bisecting the
fins along the proximal-distal axis; and marble, the ontogenetic
appearance and disappearance of pigments in patches in the body and (to a
lesser extent) fins. All await genetic explanation. A genetically-based
show system would preclude such forms.
A show system based on genetics would likewise impose intolerably long
delays in introducing new show categories. New colors and new forms of
Betta are continuously being developed. Among the colors, orange and
copper are recent additions. Recent form variants include the crowntail, a
striking and extreme form of the combtail trait, the halfmoon discussed in
my column of November 2003, and the short moon, an attractive new form
generated by repeated crosses of halfmoon fish to short-finned plakats.
The orange color was developed by selective breeding by Gilbert Limhengco
and is now being "worked" by a number of breeders. The copper color
emerged from Thailand in 2002 and is said to have been developed by
introgression from wild animals. Although anecdotes abound, hard data of
the transmission of these traits in crosses between animals of known
phenotype are lacking. There is no reason, though, that the show circuit
must wait until someone has the inclination to make the half-dozen or so
crosses required to establish the genetics issues firmly. Science takes
time, commitment, and money. The show circuit cannot be held hostage to
waiting for this constellation of conditions to be satisfied.
While neither orange nor copper and its variants are yet recognized as
classes in the International Betta Congress (IBC) show system, their
inclusion is not precluded by a lack of genetic understanding. For the
perspective of a breeder of show animals, the concern is not precise
predictability, as guaranteed by the "dance of the chromosomes" which
yields simple Mendelian ratios, but only that the trait appears with
sufficient predictability to permit and sustain a breeding program.
While genetics need not be a precise map to show categories, genetic
considerations are far from irrelevant. Indeed, they are an essential
component of the entire enterprise. The mission of the IBC includes the
preservation and enhancement of the animal. The show classes put the power
of our competitive spirit to meet the mission of enhancement. Setting
standards at the highest level, even if those goals are rarely realized,
guarantees that breeders will continue to attempt to produce the cleanest
of reds, yellowest of yellows and the blackest of blacks. An understanding
of the underlying genetics allows one to plot the most rapid route to this
desired end. It allows one to appreciate that the quickest route, for
example, to greens is not by breeding blue to yellow, but rather by
breeding blue to blue.
The show system plays another vital, albeit less appreciated role.
Establishing and maintaining show categories attracts breeders to those
categories. This, in turn, assures that the relevant genetic combinations
specific to that category are preserved. This point bears elaboration and
emphasis. If there is not a system in place that assures otherwise,
genetic variation will be lost.
The relevant genetics here are not the inheritance rules known to most
breeders, but are rather derived from an allied field called population
genetics. Population genetics, to a first approximation, can be thought of
as the science that arises when one combines the Mendel's inheritance
rules with demography. It deals with genetic expectations within whole
populations. Among the problems posed to population geneticists are ones
like: "How large must a population of endangered species be to ensure that
genetic information will not be lost" or "How many seeds must be stored to
ensure that we preserve the known genetic diversity of maize." These
questions are but rephrasing of the one we wish to ask.
Imagine that there were no show system and that breeders did not design
crosses based on an appreciation of genetics. If all crosses were made by
choosing parents at random, the odds of losing an allele by chance alone
is approximated by 1/2N, where N is the number of breeders. If we assume
that the number of active show breeders in the IBC in any given year is
15, then the chance of losing an allele in that year is 6.7%, an
appreciable risk. Given that this risk would apply year in and year out,
it is effectively certain that genetic variation would eventually be lost
unless some convention precludes it.
Population genetics tells us that genetic variation is vulnerable to
extinction in a small population of breeders. It likewise tells us how
this danger can be mitigated. There are two ways. We could breed at
random, but increase the number of breeders. If we had 100 active
breeders, the chance of losing an allele is vastly lower (0.1%). An
alternative solution lies in non-random breeding. Indeed, this is
precisely how the show system ameliorates extinction risk. By providing
classes for specific combinations, it essentially guarantees that someone
will breed that combination and in so doing guarantees that the genetic
variation required to produce that combination is maintained. If we are
concerned with maintaining the genetic variation required to produce an
opaque Betta, that variation will be maintained as long as a single
breeder is working opaques.
The judging standards and show system acts as a modulator of the
population genetics of Betta. Recognizing this is helpful. One might look
at the fish at an annual convention and bemoan the fact that "the
cambodians are not what they used to be" or that "there are no good
pastels," and so on. Such variation in quality is inevitable with a large
number of classes in a labor intensive hobby in a world where most find
themselves time-constrained. Yet, if we remind ourselves that the foremost
reason for a show category is preservation and that enhancement is a
secondary consideration, today's poor cambodias are insurance that
variation is available for future enterprising breeders. Indeed, a wise
judge will take a new breeder on a tour of classes with less than stellar
animals and explain what might be achieved.
These considerations hardly exhaust the interface between judging
standards and genetics. Any number of topics are germane. Is it more
important to establish a class if the new trait is polygenic than if it is
a simple Mendelian trait? [Yes] Do systems established on a color
hierarchy result in larger number of classes than systems based on other
criteria (e.g., form, pattern)? [Not necessarily] If classes ever need to
be eliminated or combined, are there genetic grounds for preferring one
elimination of one class over another. [Yes]
The job of maintaining International Betta Congress (IBC) show standards
and judging criterion falls to the IBC Judging Board (JB). The importance
of their work is recognized by the special status accorded their
decisions. While all other matters are subject to membership approval, the
show standards are solely the responsibility of the JB. What makes the
work of JB among the most challenging is not the technical content
emanating from genetics, but rather the vastly more complex matter of
balancing genetic knowledge with aesthetic sense in a fashion that
supports rather than erodes the social fabric of the organization. This
may in practice be quite difficult to achieve, but then that is what makes
the job of interest.