Last updated: 2012-03-12 — Created: 2010-09-08
There’s a quick mention of breeding EBJDs in the February 2012 Freshwater Q & A section (page 6) of Aquarium Fish International magazine. Check it out!
If anyone has had the opportunity to see one of these stunning Rocio octofasciata fish in real life, s/he’ll agree that few other cichlids come even close to the wow-factor that these maintain. In hopes of producing some EBJD offspring, I’ve started to grow out one male EBJD and three female regular JDs.
Jack Dempseys can be sexed the same way as most cichlids – males have the typical long, pointed fins where females have shorter, rounded ones. In addition though, female JDs have a blue spangling on their cheeks, as can be seen from the above photo, where the males just have the underlying body colour.
This large male was in Big Al’s Scarborough and has a gorgeous, almost electric blue appearance. However, he is indeed a standard JD with the standard underlying dark body colour. You can also see here the lack of blue spangling on his cheek, as compared to the female in the previous photo.
Theories of whether the electric blue variant is a natural colour morph or has been hybridised are abound and have been hotly debated. I’ve talked to a gentleman who has worked in ornamental fish wholesale, saying to have seen many EBJDs that possessed traits more like a Cuban cichlid (Nandopsis tetracanthus) than a Jack Dempsey during his tenure. Others have claimed that the EBJD also has part Haitian cichlid (Nandopsis haitiensis) in it. It could be that many generations of out-crossing to regular JDs has aligned and stabilised the EBJD genes. However, until someone actually repeats the hybridisation and provides actual photographic proof of the process (a good start is here), I’m sticking with the natural colour morph theory. After all, it’s just as likely (if not more likely) that a natural colour morph EBJD was hybridised to a Cuban cichlid to produce these Cuban-looking EBJDs. I do not believe that a regular JD was hybridised to a Cuban cichlid to arrive at the EBJD we now know and love! The topmost photo in this post shows one of my EBJD males next to a JD female and it leaves no question in my mind that EBJDs are just a variant with albino-like mutation. Red pigment in this fish is limited regardless, so this explains the yellow eyes instead of red. So, with this said for the sake of exploring the possibilities, let’s continue…
EBJDs are the result of a semi-lethal recessive gene mutation that reduces the typical pigmentation of the fish, giving rise to the truly-sweet electric-blue colouration. They are a natural variant, however, they aren’t found in the wild because the weaker blue fry do not survive. The double-dose of the blue gene causes the EBJD to grow much more slowly and become a tad less nasty than its wild-type counterpart. As a result, blue fry must be carefully separated from their black brothers and sisters and raised in isolation in order to survive. This was originally done by a fellow named Hector Luzardo in 1985. Slower growth also means that while your EBJD and JD juveniles may be the same size when you purchase them, they will be of radically different sizes within a few months. You will probably have to give your original EBJD some lead time to grow before getting him/her a mate.
To further complicate the issue, the inherent weakness of the EBJD means that if two EBJDs are mated together directly, while they will indeed produce 100% EBJD offspring, these offspring will be so weak, the pairing will almost surely also result in 100% dead offspring. So, how do we obtain blue offspring if we can’t use the blue fish to do it, you may ask? The answer lies in making use of blue-gene carriers, as was originally done when these fish were first discovered. The fish that carry the gene, but look like regular ol’ Jack Dempseys, are known as BGJDs, blue-gene Jack Dempseys.
Genes: eb = the electric-blue gene JD = the wild-type gene Fish: JD/JD = WTJD - A regular/ordinary/wild-type JD JD/eb = BGJD - A blue-gene JD (looks like a wild-type JD) eb/eb = EBJD - An electric-blue JD
So, at the locus that controls electric-blue colouration:
- A wild-type JD has two copies of the wild-type gene and no blue genes.
- A blue-gene JD has one copy of the wild-type gene and one copy of the blue gene (but looks exactly the same as the wild-type JD)
- An electric-blue JD has two copies of the blue gene and no wild-type genes.
Ideally, we would just be able to randomly put two Jack Dempseys together and have them mate to produce some electric-blue offspring, as Mr. Luzardo did, however, the chances of this are pretty slim, and it would involve more time and tank space than the average aquarist would typically have. So, we must rely on other means. The first step is to out-cross our EBJD in order to preserve the blue gene, but allow stronger genes to be used in creating future generations. It doesn’t matter which parent is which colour, however, since a lot of male cichlids are known to be more temperamental and beat up their mistresses, I have opted to use a blue male and regular females. I would much rather replace and re-grow a $7 JD than a $48 EBJD should anything go awry. I’ve seen both males and females in stores, so perhaps I will reverse the colours in the future, once I’ve acquired more experience.
Please note: The projections suggested below are completely theoretical – reality is rarely so exact. Genetics may do its part to produce a ratio as is described, however, unpredicted gene interactions, male growth superiority, bad environmental conditions, bacteria, disease, competition for food, sibling cannibalism, fish defects, etc. all can skew these numbers.
Mate: Outcross EBJD to WTJD x | JD | JD | ----+-------+-------+ eb | JD/eb | JD/eb | ----+-------+-------+ eb | JD/eb | JD/eb | ----+-------+-------+ Result: 100% BGJDs (look like wild-type JDs)
Now that we have a spawn containing all blue-gene carriers, the next step involves a number of options, each with major benefits and drawbacks. While it is unknown whether all EBJDs out there descend from the same pair or not, we do know that there is an inherent lack of vigour in the blue offspring. Whether this is due to inbreeding depression caused by inheriting multiple identical copies of certain bad genes, or whether it’s just something about the double-dose of blue that makes the fish weak by nature, is unknown. Regardless, we can’t do anything about the blue fish being weaker, but there are some things we can do to ensure all of the other genes involved are as varied and strong as is possible. If we know there’s a weakness in the blue fish, our goal should be to ensure that we select non-blue fish that are totally unrelated and share no common ancestry. Do this by purchasing only one fish from each store/chain/hobbyist and ensure that they don’t use the same supplier as other places you shop. Obviously, selecting siblings from the same tank in the same store from the same supplier is no way to go about obtaining genetic variety! Now, on to creating the actual EBJDs…
Option 1: Inbreed Mate: BGJD to BGJD, brother to sister x | JD | eb | ----+-------+-------+ JD | JD/JD | JD/eb | ----+-------+-------+ eb | JD/eb | eb/eb | ----+-------+-------+ Result: 25% WTJDs 50% BGJDs (look like wild-type JDs) 25% EBJDs Pro: Cheapest - only one EBJD involved, used in one spawn. Pro: Brothers and sisters are about the same size. Pro: No risk of losing expensive EBJDs. Con: Wild-type offspring will be mixed with blue-gene carriers. Con: Least genetic variety (inbreeding is worse than back-crossing).
Option 2: Back-cross Mate: BGJD to EBJD, father to daughter or mother to son x | JD | eb | ----+-------+-------+ eb | JD/eb | eb/eb | ----+-------+-------+ eb | JD/eb | eb/eb | ----+-------+-------+ Result: 50% BGJDs (look like wild-type JDs) 50% EBJDs Pro: Cheapest - only one EBJD involved, used in two spawns. Pro: Highest output of EBJD fry possible. Con: Original parent must be re-introduced to a new mate. Con: Potential size mismatch with new pair. Con: Reduced genetic variety from re-use of original parent. Option 3: Cross with 2nd EBJD. Mate: BGJD to unrelated EBJD x | JD | eb | ----+-------+-------+ eb | JD/eb | eb/eb | ----+-------+-------+ eb | JD/eb | eb/eb | ----+-------+-------+ Result: 50% BGJDs (look like wild-type JDs) 50% EBJDs Pro: Highest output of EBJD fry from an adequate genetic base. Con: Added cost of 2nd EBJD parent. Option 4: Perform Step 1 with two different sets of parents, resulting in unrelated spawns A and B (all BGJDs). Mate: A males to B females, B males to A females x | JD | eb | ----+-------+-------+ JD | JD/JD | JD/eb | ----+-------+-------+ eb | JD/eb | eb/eb | ----+-------+-------+ Result: 25% WTJDs 50% BGJDs (look like wild-type JDs) 25% EBJDs Pro: Most varied genetic base, strongest offspring. Pro: No risk of losing expensive EBJDs. Con: Added cost of 2nd EBJD parent. Con: Wild-type offspring will be mixed with blue-gene carriers. Con: Must grow out each pair and each spawn in separate tanks!
From my understanding of genetics, these options are in order of least-to-most preferable. I will personally be attempting Option 3, which would be my recommendation to anyone trying this at home. Also, if there’s anything you can do to ensure that your two EBJDs come from as varied a source as possible as well, it should further increase the strength of your line.
Things to Note:
- Do not mix EBJDs with any kind of aggressive cichlid. They will die!
- EBJDs have a very high mortality rate and will often die off before they reach about 7 cm in length, especially if stressed. Do what you can to limit this stress!
- Make small, frequent water changes. If you must remove a large amount of water, replace it slowly, in stages, allowing enough time for the water temperature to stabilise – limit the stress from temperature and chemical changes in the water.
- Do not mix small & timid EBJDs with large & nasty Jack Dempseys!
- EBJDs don’t grow as fast, but do grow as big as their wild-type counterparts, up to 25 cm in length. They will start of a pale gold colour and will be fully-blue by the time they reach about 4-5 cm.
- EBJDs are f#*%ing expensive, so be nice to them! 😛
- Buy EBJDs as big as you can find them. Having going through five (yes, FIVE!) 3 cm fish at $30-35 apiece, I finally splurged on the larger male pictured above.
As you can see, creating healthy EBJDs requires patience in successfully breeding two generations of fish. Your first EBJDs will be the grandchildren of your original EBJD specimen. This explains why the high cost is usually associated with this glamourous variant!
Random thought: The colours of various fish scales are dependent on cells called chromatophores, including: melanophores (black), xanthophores (yellow), erythrophores (red), iridophores (silver/metallic/iridescent) and leucophores (white). Let’s think about colour theory here for a moment, specifically the additive (light) and subtractive (pigment) colour models. These are the three intersecting circles of primary colours: red-green-blue or cyan-magenta-yellow, respectively. EBJDs, as compared to wild-type JDs are definitely missing most of their black pigment. If we shine white light on the fish and most of its cells that reflect red light are missing and most of its cells that reflect yellow light are missing, what is left? Try opening Photoshop or your favourite application with a colour picker and make your own custom colour. If you start with white in the RGB model, remove some (say 40%) red and then remove some yellow too (yellow is a combination of red and green, so remove equal amounts of each of these, say 60%), what colour do you get?
WHITE (#FFFFFF) – RED (#660000) – YELLOW (#999900) = (#0066FF)
It would seem that EBJDs have not only reduced amounts of black pigment in their scales, but also don’t produce normal amounts of red and yellow, resulting in a cyan-blue hue. Question: Is there anything on which a fish missing the ability to synthesise certain compounds into coloured pigments might lose out? Is there a beneficial side-effect of creating certain pigments?
Update: I have personally seen what I believe to be both male and female EBJDs in multiple pet shops (“females” were smaller, paler and had shorter, rounded fins as compared to their “male” tankmates), so I do not believe in any sort of sex-linked genes that results in only one gender of these fish. However, after some discussion with other breeders, it would seem that there can be variations in the male-female ratio of blue offspring produced. The exact cause of this is still to be proven, but it’s likely related to water chemistry. The current working theory is that harder/alkaline water produces more males, where softer/acidic water produces more females. The acceptable pH range for these fish seems to vary wildly from one source to the next, but 6.5 to 8.5 seem to be the extremes. Fish eggs in hard water will have a shorter time to be fertilised time than those in soft water. Male (Y-chromosome) sperm are apparently faster, but have a shorter life, while female (X-chromosome) sperm will bring up the rear and stick around a little longer. By putting these two pieces of information together, short fertilization time in alkaline/hard water means more males (all, in extreme cases), while longer fertilization time in acidic/soft water means more females are conceived. Alternatively, with Betta fish, it’s been noted that the age of the parents can affect the sex ratio of the offspring, which is another possibility to test for EBJDs. Younger males mated to older females (hence mother to son) produce more male offspring, where younger females mated to older males (hence father to daughter) produce more females.
- It’s been suggested that the blue-gene JDs (that are apparently indistinguishable from their wild-type brothers and sisters) in fact are distinguishable once they reach a certain size. By looking at the underlying body colour, particularly in the forehead area, BGJDs apparently have a magenta hue to them, where wild-type JDs are a darker grey.
- Skeletal deformities are common with this fish, which apparently onset during the 2-4 cm size range. These deformities may be caused by poor water quality, bacteria or bad diet.
- As a preventative measure during the formative months for these fish, one must ensure their diet contains sufficient calcium, as well as phosphorus, which is required for proper calcium absorption. The gills can absorb calcium from the water from a concentration of 5 ppm, but phosphorus needs to be ingested. The best source of these elements is skeletal, so try to ensure some fish meal or bone-containing organisms are fed to your fish. Magnesium must also be present, though most foods will contain adequate amounts.
- I’ve been advised to raise fry in soft water for as long as possible, until the fish are at least 4-5 cm in length. It is when the fish has fully blue and no longer shows any golden blotches that you can relax a bit, as most deformities will show up by this time if they are going to.
- Eye problems are inherent in these fish, so keep your popeye medication handy just in case something flares up. My older specimen had cloudy eyes for the duration of his stay with me and the younger one has developed a haemorrhaging inside his eyeball, making his entire pupil look red instead of black. Gross!
Questions to Answer:
- What is the ideal pH/water hardness to produce a 1:1 sex ratio of EBJDs.
- Does the choice of crossing options in Step 2 affect the strength of the offspring?
- Does the age of the parents in relation to each other affect the sex ratio of offspring?
- Does the age of the parents affect the number of EBJD offspring?
- What causes deformities in the EBJD offspring?
March 8, 2011 – Experiment rebooted. After losing my old JD to age/bloat and my young one to an eye infection, I recently found EBJD #8 at my local PJ’s for a great price. He’s smaller than I would have usually bought, but bigger than the ones that went belly-up on me previously, so it’s going to work out, I hope. I think I will name him something mean, so this way he can’t die. The only question is, will big mama take to him all right?
September 12th, 2011 – After losing another EBJD male today, I’m putting this experiment on hold indefinitely. Perhaps when I have larger tanks, UV sterilisation and better filtration in place, I’ll try again, but it’s getting way too expensive losing these fish repeatedly to warrant continuing for the time being!
March 12th, 2012 – Experiment rebooted…again. I was in a store yesterday, where I had a bunch of unclaimed credit, and they had a number of small EBJDs available at a pretty good price: $50/3. So, here I go again! I’m going to grow this trio out a bit in an isolation bucket within my angelfish tank, before releasing them into the community. I’m hoping that the larger volume of water and lower aggression levels will help prevent any health issues this time around. *crosses fingers*
December 15th, 2012 – Out of EBJDs…again. I give up…for now. 😦
November 5th, 2013 – Found this lively EBJD male for just $38 at a really nice size. He’s taken to my last female, so I’m going to give it one last ditch effort. With both fish mature already, the grow-out phase can be skipped, so I hope it’s just a matter of conditioning and letting them get to work!
For more info:
- The Jack Dempsey Database
- Colour Theory
- Effect of pH on the Fry Sex Ratio