Have you ever heard of a human-hamster hybrid? It may sound like something out of science fiction, but it is very real. Interested in learning more? Read on.

What is a humster?

A humster is a human-hamster hybrid embryo that forms when a human sperm fertilizes a hamster egg. Unlike the bobcat-domestic cat hybrid embryo, the humster is unable to progress to the cellular division phase of development.

A human-hamster hybrid. Zona-free hamster oocytes incubated with pretreated human spermatozoa for 30 min and then rinsed. A, an oocyte (X245) incubated with control spermatozoa; ie, spermatozoa that had been preincubated for 10 hr and then treated for 12 min with the Sephadex G-75 column buffer. No spermatozoa are bound. Nomarski differential interference micrograph of living oocyte. B, an oocyte ( X 245) incubated with spermatozoa pretreated with the active Sephadex G-75 fraction of human follicular fluid. Spermatozoa are tightly bound to the oocyte surface. Nomarski differential interference micrograph of a specimen fixed briefly in formalin to stop flagellar motion. C, an oocyte ( ~ 4 2 5 ) incubated with spermatozoa pretreated with the active Sephadex G-75 fraction of human follicular fluid and incubated an additional 2.5 hr after rinsing. Phase contrast micrograph of a fixed oocyte stained with acetolacmoid. Several flagella appear on the upper half of the oocyte. Decondensed sperm heads and pronuclei are indicated by arrows.
This is a humster Source

What is the point of human-hamster hybrids?

Due to political regulations, along with general societal outrage attached to testing on human embryos, humster embryos are often created and used for scientific research instead. For example, human/hamster hybrid cells are useful when studying new methods of gene therapy and the effects of radiation on egg cells.

Hamsters and Human Fertility Treatments

A diagram showing the process of how a human-hamster hybrid is created. The title says "Hamster zona-free ovum test diagram." There is a drawing of a hamster being injected with the hormones PMS and HCG. An arrow labeled "egg retrieval" is pointing to an illustration of a cumulus-enclosed egg. An arrow labled hyaluronidase is pointing to a zona pellucida. From the Zona Pellucida, an arrow labeled "trypsin" is pointing to an illustration of a zona free egg. Then, separately, is an illustration of human sperm labeled "Capacited human sperm" has arrows pointing to the zona free egg labled "penetration" and another illustration of sperm labled "sperm survival."
A diagram of how human-hamster hybrids are made

While human-hamster hybrids are now created almost exclusively for research purposes, these hybrids were initially created mainly by sperm banks and fertility doctors to test male fertility. The process of creating a human-hamster hybrid to test male fertility is known as the hamster zona-free ovum test. First, a female hamster is injected with some hormones that remove the zona, or the protective membrane, around the egg cell. This membrane generally prevents other species from fertilizing the egg. However, with the zona gone, fertilization of the hamster egg by other species is now possible. This is when the male fertility test comes in. If the sperm can penetrate and fertilize the egg, that means the sperm is healthy and the man is fertile. Today, fertility clinics rarely use hamster test. Compared to other methods, humsters just aren’t all that great at determining fertility when compared to other methods.

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Nessie O'Neil

Educator

About the Author

Nessie O'Neil is an educator, costume designer, and biologist currently researching the impact of tourism on the critically endangered pygmy raccoon.

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