Black Lightning Angelfish

In the early years of breeding angelfish for color types, aquarists developed black angelfish that were all the same genotype, having two doses of the gene for dark (Norton, 1971). Later mutations, which resulted in marble and gold angelfish, made possible two more black genotypes, dark-marble and dark-gold (Norton, 1982). The dark-gold marble genotype is the most recent black and happened to be the genotype of the first black lightning angelfish that I had.

In the adult black lightning angelfish,the body is near black, and mottled, similar to that of a homozygous marble (see photo of homozygous marble in Norton, 1990). It also has white streaks in one or more of the dorsal, anal, and caudal fins. In some individuals, there is white in one or both of the ventral fins. The most showy individuals are black veiltails that have bold white streaks in the fins, whereas others have fine white striations in their fins. I named this angelfish "black lightning" because of its striking white markings on black.

My first black lightning angelfish came from Tim Anderson, who told me that they were in a spawn of 100% blacks in which about half of them had white streaks. Their male parent was black, without streaks; the female was non-black. The same black male, crossed with a different non-black female, again produced 100% blacks, but none had white streaks. I suspected that the first female that Mr. Anderson used had a gene that caused the streaked pattern, but she was no longer available for further crosses.

One of the streaked blacks that Mr. Anderson gave me turned out to be a dark-gold marble genotype male; I knew this because a gold female and this male produced  156 gold marble and 149 black offspring. Some of these blacks were streaked. Next, by crossing the same streaked black male with a silver female that carried gold, I discovered that he was heterozygous not only for dark and gold marble but also for stripeless. This cross of streaked black male x silver female also produced some streaked offspring. There were 73 with the gene for dark (black, black lace, and butterfly) and 68 marble (some each of gold marble and barred marble). There were two new phenotypes, streaked black lace (heterozygous for dark) and streaked butterfly (heterozygous for dark and stripeless). Streaked black lace and streaked butterfly have some light colored patches on the body. As might be expected, the streaked trait was not noticeable in the marbles, which have streaked fins and marbled bodies anyway.

I kept two streaked black females from the gold female x Anderson streaked black male. Because the genes for dark, gold, marble, and gold marble act as alleles (Norton, 1982, 1988), and individual can have one or two doses (no more) of these genes. I knew that these streaked black females had the dark-gold genotype, having gold (from their mother) and dark (from their father), but no gene for gold marble. Thus the streaked pattern is not dependent on the gene for gold marble combined with the gene for dark. One of these streaked black females was mated to a gold male, which resulted in 81 golds and 96 blacks, some of which were streaked. The other streaked black female, mated to a silver male that carried gold, produced silver, gold, black, and black lace offspring. Some of the black and black lace were streaked. No streaking was seen in the silvers.

It then appeared that the streaked trait is due to a dominant gene, which was present in the first female that Mr. Anderson crossed with the non-streaked black male. That female was not streaked, even though she carried the gene for streaked, because she did not have the gene for dark.

To further investigate whether the streaked trait is due to a dominant gene, I mated the Anderson streaked black male and a streaked black daughter (from gold female x Anderson male). The male was known to be heterozygous for both dark and gold marble, and supposedly was heterozygous for streaked. The female was known to be heterozygous for both dark and gold and supposedly heterozygous for streaked. Six spawns from this mating consisted of 778 black (some of which were streaked) and 236 gold marble. This is the predicted result because four types of offspring are expected:

 

1. genotype dark-dark (black phenotype)
2. genotype dark-gold marble (black phenotype)
3. genotype dark-gold (black phenotype)
4. genotype gold-gold marble (gold marble phenotype)

Of the blacks in the first three of the above described spawns, 140 were streaked and 41 were not streaked. This agrees with the hypothesis that streaked is due to a dominant gene that can exist in either single or double dose. That is, it is not lethal in double dose.

I know from personal experience that some blacks heterozygous for streaked are large, vigorous, and fecund. They have produced some spawns of over 500. Whether a fish is heterozygous or homozygous for streaked has no effect, as far as I can see, on the growth of young fish up to nickel to quarter body size. One person to whom I sent some small black lightning angelfish, including some each of fish heterozygous and homozygous for streaked, had some losses later. Also, I once kept several black lightning individuals that could have been either heterozygous or homozygous for streaked. When about half-grown, these fish became lethargic and had decreased appetites while mollies in the same tank remained active and apparently healthy. These problems may or may not be due to a deleterious effect of a double dose of the gene for streaked. More work is needed to find out. Until we know whether fish homozygous for streaked have decreased vigor in later life, I recommend producing black lightning angelfish that have only one dose of the gene for streaked. One cross to use is gold (not from streaked strain) x black lightning. Half of the black offspring will be heterozygous for streaked. Or you could cross gold marble and black lightning.

I do not know how common the gene for streaked is, but it can exist in various types, including silver and gold, in which it is not evident. I have seen photos of angelfish that resembled black lightning, but the publications included no comments to explain the genetic makeup of these fish.

In summary, the black lightning angelfish is genetically a black with a dominant gene, which I call streaked. In my stock, the gene for streaked originally came from a female that carried the gene for streaked but did not show the pattern because she did not have the gene for dark. Streaked is expressed in angelfish besides black that have the gene for dark (such as black lace and butterfly), but it is especially striking and attractive in black, black veiltails in particular.