Linda A. Warner Lays an Egg

William J. Bennetta

Among the species of fish that commonly spawn in captivity -- i.e., the species for which we have the most reliable information -- fertilization rates typically run at or near 100%. It is rare for any eggs, let alone any significant percentage of a batch, to be left unfertilized. This is well known among aquarists, fish-breeders and scientists, and it explains (I believe) why fertilization rates are rarely mentioned in published reports about spawnings. Such rates don't constitute an important variable, because fertilization always proceeds with perfect or near-perfect effectiveness.

My statement about published reports is based upon my own survey of the pertinent literature. I began by searching through the classic compendium Modes of Reproduction in Fishes, issued in 1966 by The Natural History Press (Garden City, New York). In accounts of thousands of species, I found exactly five references to fertilization rates; in each case, the rate was 100%.

Looking at other sources, I found only these items:

• A paper in Marine Fisheries Review for March 1979 said that "Egg loss from nonfertilization is generally minimal." The authors cited losses of 1% or less (i.e., fertilization rates of 99% or more) in salmonid fishes and in Baltic herring.

• A report printed in 1950 in Journal of the Fisheries Research Board of Canada referred to an earlier study in which some 15,000 sockeye-salmon eggs had been retrieved from a stream: More than 98% of the eggs had been fertilized.

• Black Bass Biology and Management, issued in 1975 by the Sport Fishing Institute (Washington, D.C.), said: "Dead eggs may be present [in smallmouth-bass nests] for several reasons, including adverse temperature changes or nonfertilization of some eggs at the time of spawning." It then noted a study in which 6% of the eggs in seventeen nests had been found to be inviable, though the nests hadn't undergone harmful temperature changes. Presumably, the fertilization rate had been about 94%.

• A photograph in the 1953 edition of Exotic Aquarium Fishes, issued by the Innes Publishing Company (Philadelphia), showed a part of an egg mass of the South American fish Copeina arnoldi. All the eggs had embryos, so all had been fertilized.

Maybe, however, I had missed something. Maybe there existed some information, somewhere, that could lend a wisp of support to Heath's caption. With that in mind, I wrote to the first author shown on the title page of Heath's book: "Linda A. Warner, Middle School Master Science Teacher, Laboratory School, University of Northern Colorado, Greeley, Colorado." In fact, I wrote to Warner three times, by certified mail, asking her to cite the scientific literature on which she had based her claim about "a good chance that many eggs will not be fertilized." She did not reply.

I infer, then, that Heath's caption is just a case of ladder-peddling. Because they regard fishes as "low" and contemptible, ladder-peddlers are sure that fishes' reproductive mechanisms are clumsy and inefficient; the religion of the ladder demands that this be true, so there is no need to study the matter. Similarly, ladder-peddlers know that reproduction in the human -- the species that perches at the top of the ladder and is the biblical god's favorite -- must be a marvel of efficiency. But the peddlers are wrong about that, too.

When a female human is born, her ovaries carry 1 million to 2 million primary oocytes -- cells that have the potential to develop into eggs. More than half of these cells, however, degenerate before the female becomes sexually mature; only a few hundred thousand remain viable during puberty and later life. Of those few hundred thousand, only a few hundred ever become eggs and move to the Fallopian tubes, where fertilization may take place. And out of those few hundred, only two dozen or so can actually be fertilized, even in a female that breeds as often as is possible.

If, therefore, we want to cite an animal in which the utilization of oocytes or eggs is ineffective -- spectacularly ineffective -- we should point not to a fish but to our own kind. So much for the ladder-peddlers.

William J. Bennetta is a professional editor, a fellow of the California Academy of Sciences, the president of The Textbook League, and the editor of The Textbook Letter. He writes frequently about the propagation of quackery, false "science" and false "history" in schoolbooks.

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