Off with His Leeeeg!

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A bird-eating spider like Mino

Mino is a spider—a really, really big one! In fact, he is a goliath bird-eating spider, one of the largest tarantula species in the world. With a leg span of around 9 to 11 inches (23 to 28 centimeters) measured toe to toe across the body, an abdomen covered with urticating or barbed, itchy hairs, and an attitude, he is a perfect example of “look but don’t touch.”

So what happens when you have to get up close and personal with this guy? You do it very, very carefully!

Mino’s keeper, Chris, noticed recently that his right rear leg had developed a necrotic area near the “knee.” Mino is an old guy (for a male tarantula), and we expect him to go on for another few months at best, so we opted to wait and see if he could get the leg portion off or if it would dry up and fall off on its own. Since Mino’s leg was not leaking hemolymph (spider blood), we felt safe to watch it for a while. Chris became concerned about a week later, when the leg “rot” seemed to have traveled to the segment closest to his body, so we decided it was time to intervene.

The typical response to a leg injury for a tarantula is to remove the leg, or portion of it, at the closest joint, and then stem the flow of hemolymph with superglue or other quick-drying adhesive (no, I am not kidding!). I decided on Saturday morning that we should proceed with the surgery as soon as possible, and Isabel and I got him prepped while we waited for our veterinary technicians, Marianne and Jill.

Tarantula, and really any invertebrate, medicine has been historically limited; however, there have been many advances in recent years within the veterinary community, and of course our vet staff has been riding the wave. I was prepared to provide anesthesia in the form of carbon dioxide (CO2) gas for Mino, both to reduce the stress of the procedure and ensure the safety of those of us sticking our hands in his tank! Thanks to Kim, the nursery keeper that day, we had a lab tray ready with long-handled cotton swabs and a big syringe with a curved tip for irrigation. Isabel and I were suited up with safety glasses for the hairs that aerosolize when kicked off, leather gloves, and a CO2 tank and plastic cover for administering the anesthesia.

A word about anesthesia and invertebrates: within the invertebrate collection, we regularly use CO2 to ensure the safety of the keepers and animals. When I moved the leafcutter ant queen and workers over to their new home on exhibit, I used CO2 to “chill them out” during the move and avoided being ravaged by the huge soldier ants. When Ester services the assassin bug exhibit, she uses CO2 to do a thorough cleaning, rather than have to dodge the piercing mouthparts of 300 venomous bugs! Using CO2 seemed like the logical step for Mino’s surgery, though we had never before needed to use it on a tarantula.

When Marianne and Jill got there, I went over what I thought would be the best plan: gas, forceps, irrigation, swabs, glue, new enclosure. Any questions? Marianne then told me that she had attended a veterinary lecture dealing specifically with tarantula leg removal (wow, what are the odds?!), and that the use of CO2 would interfere with the animal’s natural mechanism to cast the leg. She also said that when the spider wakes up from the anesthesia, it can be very aggressive as a result. Armed with this information, and since I already consider Mino to be a fairly aggressive spider, we decided to go cold turkey.

I coaxed Mino out of his burrow. His leg looked close to coming off, but still needed some help. I put a clear, square plastic container over his body to protect Marianne as she grabbed the end of the leg with forceps and applied pressure. Mino bared his fangs and protested, but, to my surprise, eventually began rotating in a circle (as Isabel chased him with the flashlight), almost like he knew what was going on and wanted to help. That is me being incredibly anthropomorphic, but in reality his behavioral responses are probably lined up for something like this if it happened in the wild! After a few minutes, the leg released, cleanly separating from the joint near the base. We moved him to a new enclosure with a more sterile substrate, and since no hemolymph was leaking at all, we didn’t even have to apply the glue. Success—and high fives all around!

The ailing leg, along with tools of the trade

Mino is still in recovery but doing well. Chris and I have since been using a natural umbilical cord-care powder on the stump, and it looks dry and clean. Since he is not getting too defensive when we reach in to apply the powder, he is still getting his attitude back—but we have every reason to believe he will recover and live out the rest of his days in seven-legged peace.

This was a great example of how progressive our vet staff is and how we all have new things to learn, every day. And also how to give TLC to an animal that can be hard to get close to, in more ways than one! Look for more adventures from Mino’s “brothers” in future blog posts—we are working on breeding this species, and since we have one receptive female and several males, it is going to be an interesting summer.

Paige Howorth is an animal care manager at the San Diego Zoo.