• Dr Norton Article: Cobra Angelfish and Continuous Light Affects

    Dr. Norton's Articles - Part 7

    Reprinted with permission from:
    Dr. Joanne Norton
    Freshwater And Marine Aquarium magazine
    Angelfish Genetics
    Photos and Text by Dr. Joanne Norton
    FAMA: November 1982, Vol. 5, #11

    Part Seven
    In 1974, a tropical fish dealer, Cleo Poe, bought three "cobra" angelfish from a Minneapolis wholesaler. These had fin markings like those of a zebra lace (which has one dose of dark and one or two doses of zebra), and the body was uniformly covered with dark dots on a gray background (Figure 1). These cobras, which cost $10.00 each (dealer price), were given to me with the understanding that I would share the offspring with Mr. Poe. Unfortunately, they never reproduced, so I did not learn anything about the inheritance of cobra.

    Figure 1: Cobra angelfish, bought from a wholesaler in 1974
    Two years later, Robert Commins wrote an article, "He's Hoping to Create an Angel," in a Michigan newspaper, The Ann Arbor News, Wednesday, March 24, 1976. This article was reprinted in the May-June, 1976, issue of NAC News, the bulletin of the National Aquarium Club. I could tell from the picture in that article that the tail pattern of this angelfish, which was raised and called "cobra" by Ed Sayer, looked like the tail pattern of the cobras I had two years previously. Although the body pattern of Mr. Sayer's angelfish was not clear in the photograph, it appeared to have some dark, vertical partial stripes, different from the 1974 cobras, which had smaller markings in the form of fairly uniform dots, with no vertical bars. According to the Michigan article, Mr. Sayer's cobras had "black and gray splashes on a silver underlay." The article gave no information on the genetics or parentage of the fish. The author stated that Mr. Sayer had many cobras that came from a cross of two other varieties, of which Mr. Sayer said, "Which two I'd rather not say."

    Over the past eight years I occasionally have made angelfish crosses in an attempt to produce some cobras like the ones I had in 1974. It was not until this year that I was successful. After none of my crosses produced the cobra pattern, I began to suspect that day length might be a factor. I already knew the effect of continuous light on the patterns of silver, black lace and zebra angelfish.

    In Part Six I discussed some angelfish pigment patterns that are altered by continuous light. For example, a silver angelfish raised by continuous light has no body stripes, and a black lace is dusky-colored with little or no striping. A zebra angelfish raised with the lights off at night has three vertical stripes on the body. In contrast, a zebra raised in continuous light has only dots and sometimes several very narrow, irregular, vertical dark markings on the body.

    Figure 2: Zebra lace (one dose of zebra and one dose of dark) raised in continuous light for two months, then at a 14-hour day. Photo taken one year after end of continuous light exposure.
    I obtained some zebra lace angelfish from a cross of silver with zebra lace. These, which has one dose of dark and one dose of zebra, were raised in continuous light for seven months. Instead of developing the three vertical body stripes characteristic of zebra lace raised with the lights off at night, like the fish in Figure 2, these zebra lace had two partial vertical stripes on a gray background (Figure 3). Some of the same spawn were raised in continuous light for only two months and then were switched to a 14-hour day. These looked like the fish in Figure 3 at two months, but gradually developed the 3-stripe pattern after they were switched to a 14-hour day. The photo (Figure 2) was taken one year after the end of the 2-month exposure to continuous light. Unlike the modified black lace pattern that was "set" by two months of continuous light (Part Six), the modified zebra lace pattern was not set by only two months of continuous light.

    Figure 3: Zebra lace (one dose of zebra and one dose of dark) raised in continuous light for seven months. This photo taken seven months later.
    I still did not have the dotted pattern, with no vertical bars, of the 1974 cobras. I then decided to raise in continuous light some zebra lace with two doses of zebra. I had a pair of zebra lace that were double-dose zebra (each produced 100% zebra offspring, some with and some without dark, when tested by crossing with wild-type). These zebra lace, each of which had two doses of zebra and one dose of dark, were mated, which produced zebra, black and zebra lace offspring, all having two doses of zebra; they were raised in continuous light. At last! There were three different patterns in the offspring: light ones (double-dose zebra, no dark), black (double -dose zebra, double-dose dark), and dark ones (two doses of zebra and one dose of dark). The dark one (Figure 4) looked exactly like the 1974 cobras, having dark dots on a gray background, and no stripes or partial stripes.

    Figure 4: Cobra (two doses of zebra and one dose of dark, raised in continuous light), five months old.
    Many organisms that are affected by day length will react the same to various lengths of long day. for example, and 18-hour day might produce the same results as a 20-hour day. I have not raised angelfish in an extremely long day, with the lights off only a few hours at night, to see if this has the same effect as continuous light on their patterns.

    Figure 5: Each of these fish has two doses of zebra.
    Cobra angelfish are not true breeding since they are heterozygous for dark (one dose of dark). It may be possible to raise spawns of 100% cobra angelfish. To do this, you would need to cross a female double-dose zebra (Figure 5) with a black zebra male (Figure 6, two doses of zebra and two doses of dark). I suggest using a black zebra male rather than female since black males without zebra can be effective breeders for numerous spawns, while black females may spawn only a few times and then quit reproducing. The required breeders can be obtained from any zebra lace parents, which produce zebra, zebra lace and black offspring, and also silver and black lace if both parents have only one dose of zebra. The slow-growing zebras would be the ones to select, since they are the ones with two doses of zebra (see Part Four). The black zebras also are slow-growing, like blacks without zebra.

    Figure 6: Black zebra (two doses of dark and two doses of zebra).
    If the black double-dose zebra proves to be a poor breeder, which would not surprise me, then the next best way to get cobras is from zebra lace parents. You can get 50% cobras from zebra lace parents that are homozygous for zebra (two doses of zebra and one dose of dark). There will be some of this type of zebra lace in spawns in which both parents are zebra lace. Again, select the slow-growing zebra lace, as these are the ones likely to have two doses of zebra. A zebra lace can be tested by mating it with silver. If it is a double-dose zebra, then all of the offspring of this cross will have the zebra pattern (three vertical stripes), with or without dark, so there will be 50% zebra and 50% zebra lace.

    The cobra angelfish is no longer a mystery; it can be raised by anyone who knows what parents to use and that the spawns should be raised in continuous light. I have never seen cobra angelfish in shops or in shows, so I have the impression that they are rare in the hobby and trade. Perhaps, with knowledge now available on how to produce them, more of this attractive angelfish will be seen in the future. It is important, however, for anyone who buys cobra angelfish to realize that these fish will produce no cobra offspring if the spawns are raised with the lights off for a long period (how long is not yet known) at night.