Tailtype defenitions & genetics
This term is used to indicate all tailtypes of Betta splendens from which the caudal is made up out of one single part [1-5]. Familiar tail types which are singletails are: veiltails, deltas, superdeltas, halfmoons and roundtails.
The term plakat is used to describe the short-finned tail type which is originally found with the wildtype Betta splendens [1-5]. This shortfinnage makes it sometimes very hard to distinguish males from females for the untrained eye, especially with young fish.
Because of this is sometimes happens that pet- and aquariumstores sell plakat males for females to beginners in this hobby. This most of the time because of a lack of experience and knowledge. Currently three different types of PKs have been recognized at shows around the world, more on this can be found by clicking here.
A long-finned form of Betta splendens [1-5]. The tail is asymmetric which is broad at the basis and becomes pointed towards the outer edge. When the male is not flaring the tail hangs down. This tail type is commonly found with petstore bettas.
As the name already indicates, this tail type of Betta splendens has a round appearance [1-5]. This tail type is often found in spawns of delta, superdelta and halfmoon bettas.
Delta (D) and Superdelta (SD):
The delta tail is a long-finned form of Betta splendens [1-5]. This type of tail is symmetric, triangular shaped and has long, rays. The delta tail is broad at the basis and becomes wider towards the end.
The tail called a superdelta when the spread is between 160 and 179 degrees. Delta tail betta splendens often have rounded edges.
Red/blue multi superdelta male
Halfmoons are probably the popular long-finned tail type of Betta splendens at this time. The caudal of a good halfmoon has two important characteristics: (1) long and straight rays and (2) a 180 degree spread (when the spread is bigger than 180 degrees, the tail type is called an overhalfmoon (oHM)) [1-5]. The shape of a good halfmoon tail is that of a semi-circle (comparable with a “flipped” capital letter “D”). The secret of a good halfmoon tail iare the rays. The stronger the rays, the better the tail is supported during the spreading. This support is especially important when the fish become older and their fins become longer. Selective breeding led to the development of halfmoon fish with a different amount of ray splittings (4-, 8-, 16-ray or even more). This gave rise to a new development in the betta splendens tailforms, the rosetail, a tailtype which is characterized by an extensive ray-splitting.
Yellow (type2) BF HM male 
Red HM male 
Turquoise oHM male 
But keep in mind that when two halfmoon fish are bred together this doesn’t mean that you will get halfmoon in the next generation. You must be very happy with maybe 10% or less. The reason for this is the fact that the halfmoon trait is not simple the combination of one or two genes but is “multifactorial”. This means that “multi-genes” are involved . For instance:
– Genes that make the rays straight.
– Genes that control the ray-splitting (into 4-, 8-, 16-ray or even more).
– Genes that make caudal spread to 180 degree (or more).
– Genes that give the finnage a fuller appearance (for instance the dt-gene).
– and more….
If one or two of these important genes is not present in the offspring, they probably will not possess the halfmoon finnage but are only delta or superdelta tails.
Here the tail rays extend beyond the tail edge, producing a crown-like appearance [1-5]. How much the rays may extend depends on the genetic makeup of the fish. The crowntail trait can be found in betas of any tail type and shape. For instance it can be seen in VT, D, SD, HM (CTHM = half-sun) and DT. The crowntail gene intermediary inherited. This means that crowntail carriers most of the time already show more or less extended rays beyond the tail edge.
Tailtype defenitions & genetics