Originally printed as a side-bar to She Spawned Alone ('97) in the AquaNews, a publication of the Minnesota Aquarium Society.

We aquarists have cometo accept several breeding methods as routine or ordinary. For most of us when we entered the hobby, the concepts of livebearing was fascinating. As we delved into fish and their behaviors, we learned--and perhaps experienced?egg placement or scattering, cave/substrate spawning, bubble-nest building, mouthbrooding, mop-spawning, and annual peat-spawning with its required incubation time.

We who have been in the hobby for a while have taken these methods for granted. What catches our attention are certain twists on these themes. Examples include the parasitic egg exchange of Synodontis multipunctatus, or lip-brooding by certain Loricariids. (Both of these documented by M.A.S.?s Paul Turley this past year [?96].)

I have known of another twist for some time, but only now [early '97] have I experienced it.

The Glandulocaudins, a subfamily (Glandulocaudinae) of the S. American Tetras (Characidae), is known for two traits: a gland at the base of the male?s caudal (hence the name), and the breeding method of internal fertilization with a delay of laying/scattering the eggs by the female. While ichthyologists have yet to prove that all Glandulocaudins reproduce this way, they now recognized that most do.

Actually, the female?s eggs are not truly internally fertilized. Rather, the female receives and stores packets of sperm. These packets are called "spermatophores." Well after this "reception," the female will lay or scatter the eggs among plants. The current belief is that the eggs are fertilized while they are laid.

The appearance of fry in tanks that contained only transferred females shocked early aquarists. The opinions as to how Glandulocaudins reproduce has evolved throughout this century.

Initially, some aquarists guessed that these fishes were livebearers. As aquarists realized that eggs were laid, the question arose how and when the eggs are fertilized. Some aquarists observed the male emitting the spermatophore and the female mouthing it. Others observed the female mouthing a leaf before the eggs appeared. Consequently, the theory arose that the female held the spermatophore in her mouth and later spit it onto the spawning site just before scattering her eggs.

An aquarist discovered that some females have delayed egglaying for up to eight months after it was last with a male (Weitzman 85)! Surely this must have cast doubts upon the "mouthing" theory. The question at this point is whether the eggs are fertilized and stay dormant until they are laid, or does the spermatophore remain isolated from the eggs until the laying?

Stanley Weitzman of the Smithsonian has recently answered this question. The spermatophore resides inside the female isolated from the eggs. The eggs are fertilized at the time of expulsion. That sperm can be stored for such a long time should not shock aquarists. Livebearers (poecilids, not goodeids) follow the same pattern: A female stores the sperm and a group of eggs can be fertilized months after insemination.

Weitzman and other colleagues delivered a multi-part essay on the Glandulocaudins in TFH from late ?95 to mid ?96. Weitzman precluded this series with an article on the subfamily in Smithsonian Contributions to Zoology in 1985.