Genetics of the Gold & Red-Spot Severum Varieties

Here I’ll examine the genetics behind the false severum cichlid (Heros efasciatus). This fish is available in a number of colour morphs, with the most common being the wild-type green, red-shoulder green, gold and red-spot gold.  The true severum (Heros severus) is of less importance to this topic, as it is nearly identical in appearance, but is a mouth-brooder instead of an egg-layer, and to my knowledge has not been involved in creating the fancy colour morphs we see in shops today.

Some photos of the various colour morphs available…

Severum Genetics

Though I have not personally produced the results below, my understanding is that the green gene is dominant and the gold gene is recessive, requiring two copies of the gold gene, one from each parent, to be present in order for a fish to be gold in colour. This gene produces what is known as a xanthistic (or xanthochromatic) fish, where excess amounts of yellow pigment are present or where the darker pigments are reduced, thereby allowing the yellow to shine through more prominently. A bird showing this trait is often known as a ‘lutino’. Fish that also displays this recessive trait include the gold Jack Dempsey and gold angelfish.

This can be depicted as follows:

Genes:
G = the dominant wild-type green gene
g = the recessive xanthistic gold gene

Fish:
(G/G) = a wild-type green severum
(G/g) = a gold-gene green severum (only carries the gold gene)
(g/g) = a gold severum 

Which gives rise to the following potential crosses:
(I'll spare you the Punnett squares this time)

G/G x G/G = 100% wild-type green
G/G x G/g =  50% wild-type green, 50% gold-gene green
G/g x G/g =  25% wild-type green, 50% gold-gene green, 25% gold
G/g x g/g =  50% gold-gene green, 50% gold
g/g x g/g = 100% gold

My understanding is that the red-spot severum is a just a variant of the gold severum that has been severely line-bred for added red colour, but observations of some offspring will hopefully allow for a more conclusive statement to be made.

Questions to Answer:

1. What gene(s) is/are responsible for the red-shoulder green severum (aka rotkeil)? How do they relate to the genes on the gold/green locus? Can these genes be passed to a gold severum, producing a red-collar gold severum or is this a trait exclusive to the green variant only?
2. What gene(s) is/are responsible for the red-spot gold severum? Does a red-spot x gold cross produce a different amount of spotting between offspring, an intermediate amount of spotting on all offspring, a 50-50 split or all either gold or red-spot offspring? This translates to figuring out if there is a separate red spot gene and whether the interaction with the gold gene produces variable expressivity, co-dominance, or full dominance/recessivity or not.

---

Sexing

These cichlids follow the same rules as most and can be sexed by either comparing the length and pointedness of fins or by venting. However, males of this species generally have slightly more intense colours, particularly in the form of red spangles around the head. One method of sexing I’ve found pretty reliable so far is the “squiggle” method. If you draw a thick imaginary band on top of the head that connects one eyeball to the other, looking down on it you will notice that females have a pronounced absence of any spangles, pattern or added colour in this region, where males have squiggles or stripes that continue throughout this region. Check the above photos for some good examples.

It’s somewhat harder to notice the colours on green specimens, however, if you get them when they’re calm and put them in a tank with a light-coloured substrate, it makes things easier as the blacks and reds become a lot more pronounced and the greens take on a more olive hue.

Pairing

These fish are notoriously choosy about their mates. Convicts, for example, will swap mates faster than a college student at a singles bar on a Friday night, should the pecking order in the tank be disrupted, if a particular pair is isolated, or if a different pairing happens to be feeling ready first. However, out of the seven severa that I’ve raised, I was able to obtain only one pair. The remaining male would not take to any of the four females from which he had to choose, beating them up quite severely as he chased them from his territory.

The pair I did find is the red-spot gold male and gold female, shown at the top of this post. To find a pair, it’s best to obtain a number of specimens of roughly the same size and age and raise them together. Of course, if you can get them from different sources, this will improve the genetic base some. Once you notice two swimming together, preparing a spawning site, guarding a territory or even protecting eggs, you know you have a pair! I’ve found my pair to be quite monogamous thus far.

Red-Spot x Gold Spawn

My pair has spawned a number of times, but I have been unable to have any fry survive to reach any sort of observable size as yet. After a few attempts at getting their eggs to hatch and survive, I think I’ve found a recipe that works! I found with the first few attempts that the eggs would be eaten or that conditions were not quite right for them to hatch.

The issue of the eggs being eaten was solved by letting the parents guard the eggs for no more than one night. Even in isolated quarters, I found one parent or the other would get nervous/hungry and gobble up the eggs (though this may be a function of the pair being young and inexperienced). So, before the second day, the hunk o’ clay flowerpot upon which the eggs were laid was removed and placed in a floating bucket within the same tank as the parents. This bucket was made from a 15-litre clear recyclable water cooler jug with the top cut off. The water was part tank water, part conditioned fresh water that was allowed to match temperature before the eggs were transferred. A small (primed) sponge filter was added with a moderate-to-heavy airflow.

The next hurdle was fungus. Without a parent constantly fanning eggs, allowing fresh water to reach them, and picking off the dead eggs, fungus tends to spread and wipe out the good eggs at a much faster rate. Usually, it’s the third day after the eggs are laid when this happens. Added aeration can help, but there’s a delicate balance between having enough water movement and whisking the eggs away in too much current. As an added measure, 2.303% solution methylene blue was added to the water  at a concentration of about 1 drop per litre, perhaps a little less. The suggested dosage is about 3 times this, which I found to be too strong, killing the eggs as well as the fungus! You’re aiming for a dose of about 1 ppm. Note: Methylene blue is one of those magic chemicals that can be really hard to find on store shelves. Perhaps it’s one of those things that has been banned in places as it’s “known to cause cancer in the state of California”. Now, whether this means that only people in California get cancer from the worldwide use of methylene blue, whether methylene blue can give you cancer when you arrive in California, or whether people living in California exposed to methylene blue have had cancer, I don’t quite know, but as a precaution, treat it as something you do not want to get on your skin, regardless. It leaves a really nasty blue stain (surprise!) on most anything it touches, so consider yourself warned!

It is critical that, between the eggs being laid and the fry becoming free-swimming, all dead eggs/wrigglers be removed on a daily basis to avoid poisoning of the survivors. These are easy to differentiate, as they have a distinctly-white colour as compared to the live ones. Fertilised eggs and wriggles will also show eye spots after a couple of days, which unfertilised eggs will not have. Dead eggs are pretty easy to flick off with something small, and pointy (toothpick, chopstick, fork, etc.). Wrigglers are pretty easy to pour/siphon off and separate with a large eyedropper. In this way, dead eggs and debris are removed with some of the water and the healthy wrigglers are replaced along with some fresh water. It is not necessary to re-dose with methylene blue at this time.

Within a week, the fry should have finished off their egg sacs, become free-swimming and will zip around the isolation tank looking for their first meal. Turn down the aeration to moderate-to-light and raise the fry as you would any other, perhaps transferring them to a small grow-out tank after they appear strong enough.

Observations

With New Year’s celebrations, I kinda lost track of the exact date the eggs were laid, so let’s just say December 29th will be our starting point and count from there…
Day 5/Jan 3rd, 2011 – Wrigglers finishing off their egg sacs atop a sponge filter inside a floating isolation bucket. They appear to be doing all right so far. *crosses fingers*

Day 6/Jan 4th, 2011 – Wrigglers turning into free-swimming fry and starting to explore the tank a bit. Mom and dad still watch them, protectively.

---

Day 20/Jan 18th, 2011 – Only a small handful of fry left, but they’re growing slowly and steadily.

---

Day 28/Jan 26th, 2011 – Down to only one. Man, are these fry fragile!

Day 39/ Feb 6th, 2011

---

February 1st, 2011 – A new batch of eggs was laid last night!

Revised: 2012-02-21

---

References:

• methylene blue info
• methylene blue from Big Al’s Online (Canada / US)