A child presses close to the glass tank, an expression of wonder on his face.   Inside the tank three frogs hang suspended in the water, motionless.  Their webbed hands and feet splayed and held askance.  The child bangs the glass with his hand, willing them to move.  “Don’t tap on the glass!” his harried mother intones.  The stillness of the animals within their tank contrasts starkly with the swirl of activity just beyond.

It is a crowded Saturday afternoon at the special exhibit “Frogs: A Chorus of Colors” on display at the Museum of Science.  Children and adults bustle from tank to tank, curiously peering at the wonderful and weird creatures within.  The Xenopus laevis calmly survey the chaos from the protection of their watery sanctuary.  These aquatic denizens may not be as eye-catching as their cousins Dendrobates azureus, the blue poison dart frogs, or as bizarre and bumpy as Theloderma corticale, the Vietnamese mossy frogs, but they have a rich history in scientific research.

Xenpus laevis, commonly known as the African clawed frog, has been used to study topics as diverse as development, neuroscience, and cloning.  However, their treatment in research labs has not always been on par with their valuable contributions.  Dr. Hazel Sive, the Associate Dean of the School of Science and Professor of Biology at MIT, has a long history of working with Xenopus and early in her career, spearheaded a movement toward more humane treatment of these slippery model organisms.

Sive first encountered the African clawed frog while doing undergraduate research in South Africa, where she was raised.  She returned to frogs for her postdoctoral work in the lab of Dr. Harold Weintraub at the Fred Hutchinson Cancer Center in Seattle, Washington.  It was there that she began to notice differences between the ways frogs were kept and treated in South Africa and the US.

In South Africa, where Xenopus are native, they can be harvested from the wild and mate spontaneously, after which eggs can be collected for use in research.  However, in the US they are not found in the wild and must instead be injected with hormones which cause them to lay eggs.

Sive describes this process.  “To get frogs to lay eggs you inject them with hormone, then collect the eggs manually.  You actually pick up the frog,” she gestures with an imaginary frog in her hands, “and hold her over a petri dish.  If you do it just right she’ll lay a bunch of eggs into the dish.”

After harvesting eggs, the frog is placed in a bucket of water until it is returned to the tank where it lives.  Due to the injection the frog will continue laying eggs in the bucket throughout the course of the day.  If left too long, the eggs begin to soil the water and rot.  This can lead to a huge bacterial bloom if the water isn’t changed.

“The bacteria will infect the frogs which have very, very thin skin, only two cells thick.”  Sive explains gravely, “The frogs get terribly sick.  They get gangrene and neurological degeneration and they die what I’m sure is an absolutely horrible death, even though they can’t say anything.”

A defining moment in Sive’s relationship with frogs occurred when she once neglected her own frogs in a bucket of water over a weekend.  “One time, I left my frogs for the weekend and came back and the frogs were rotten and the water was rotten and I thought, My God what have I done?”  It was terrible for her and for her frogs.

But she learned from her mistake, “I said this is never going to happen again.  I started making sure my frogs were always gorgeous and healthy and clean.”  Not only did she apply this to herself, she went about ensuring her colleagues’ frogs were also treated well.  If people left their frogs in disgusting water she would change it.  Once, incensed by her colleague’s neglect of his frogs, which were close to death, she went a step further.  “I actually put them on his desk in the bucket and said ‘Here, look what you’ve done.’  I think he was more diligent after that.”

She began to notice other things, “People would talk about squeezing the frogs to get the eggs.  Some people, instead of holding the frog gently and letting her lay would actually squeeze the frog like a tube of toothpaste, and I realized this was wrong.

“I thought about how frogs naturally mated which is really cute.  The male comes up behind the female and puts his little feet around her belly,” she again picks up her imaginary frog, “and gives very gentle little squeezes that stimulate the female to lay.”  She gives her ‘frog’ gentle little squeezes.

“I started telling people you have to be like the male frog, you have to be real gentle to the female.  It was interesting to see the reactions, people laughed at me initially.” says Sive.

There was a pervading sense that no one wanted to be bothered.  “That really made me so angry,” she laughs remembering, “and so of course I did bother them, a lot.”  Sive’s pursuit was not made easier being only one of two women working in the lab, but she is not one to be easily deterred.

Sive realized that frogs were probably being mistreated in more than just her own lab.  “I thought that this must be going on across the world.” says Sive.  “Frogs are funny because they don’t say anything and they can be in the most terrible pain.  It struck me that was just not fair to the frogs.”

To address the problems she was seeing, Sive set out to organize a course at Cold Spring Harbor Laboratory.  Situated in a picturesque location on Long Island Sound, Cold Spring Harbor is renowned for its quality yet notoriously intensive course offerings on topics spanning the life sciences.  She envisioned a course teaching people how to care for their frogs as well as scientific techniques for studying development using frog embryos.  She was invited to Cold Spring Harbor to present her ideas and convince them to host the course.  Despite what Sive describes as their “mildly enthusiastic” reaction, they decided that a course on early Xenopus development would be quite useful.

Sive brought in Dr. Richard Harland, an assistant professor at Berkely at the time, to help her cobble together the first course.  “It really was an enormous amount of work.  We were there from six am to two at night.”  Sive chuckles, “And I had two small babies at the time.  I left them for two weeks, much to my husband’s alarm.”

The first course was a success with about 20 attendees.  Many had never held a frog before, and says Sive, “some were terrified of frogs, but their supervisors had sent them because they wanted them to work with frogs.”  Sive describes the course as, “not meant to proselytize but to get people to understand that frogs could be looked after well or not well, and that well was better for everybody.”  She notes, “Frogs are nice, gentle creatures, and you are powerful and you have the right and responsibility to look after them properly.”

She also introduced some interesting terminology during the course.  “We did not allow the word ‘squeeze’ but we said you could ‘massage’ the female frog.” says Sive.  In the second year of the course, “my co-teacher, Dr. Rob Grainger,” Sive lets out a big laugh, “gave me a t-shirt with the words “MASSAGE ME” with a picture of a frog.”

After four years, Sive handed off the course to two other colleagues, and it continues to be taught every year at Cold Spring Harbor.  Sive, Harland and Grainger have also published a textbook entitled Early Development of Xenopus laevis based on course material.

When asked what young researchers can learn from her ordeal, Sive pauses, reflecting. First, she says, “get the information you need about the animal” and second, she gives “everybody permission to question whether their experiments are worth the discomfort that they may be causing to the animal.”

Pictures from Prof. Hazel Sive’s Lab in the MIT Department of Biology, provided by Dr. Amanda Dickinson:

A picture of the tadpole face at 66 hours of development. The primary mouth opening is outlined in black dots. The sagittal section through the head of an embryo at the same stage is shown next to it. This image of a fluorescently rendered embryo was taken on a laser scanning confocal microscope to obtain an optical section.

An image of a face transplant in frog embryos. The face of a fluorescently labeled embryo (in green) was transplanted to an unlabeled embryo and then allowed to heal and develop. This technique allows the manipulation of genes and proteins in the face and the exploration of the effects on primary mouth development when the rest of the embryo is normal.

An image of a female Xenopus laevis (larger frog) and Xenopus tropicalis (smaller frog), the two types of frog studied by Prof. Sive’s lab.