20.03.2022
The autotomization of spider legs
We are often asked how to autotomize injured legs in a spider. Like many reptiles, crabs and other arthropods, spiders have the ability to autotomize limbs and replace them later when they molt again. There are many reasons for autotoming. It can serve as a distraction from enemies engaged in a twitching autotomized leg while allowing the spider to flee (Bonnet 1930). Autotomizing can also be a protection if the spider has been stung in the leg by a wasp, for example (Eisner & Camazine 1983). During mating, some males of araneomorphic Spiders autotomize the sperm-transferring palpus to flee and at the same time close the Epigyne to prevent further mating of the female with other males (Dahl 1902, Uhl 2010, Kralj-Fišer 2011, Kralj-Fišer 2012, Lee 2012). Another reason to autotomize a leg of a spider is if there is an injury or wound to a leg in the middle of a leg segment. In the case of a wound, it is closed again with chitin, but it is not uncommon for the spider to remain attached to this wound during a moult. In this case it is better to autotomize the leg before the next moult to guarantee a smooth process of the moult.
Autotomizing plays an important role in tarantulas when the male is grabbed by one leg by the female during mating or when the tarantula is held by one leg during a fight with predators. Sometimes it can happen that young spiders in particular show twisted or crippled legs after moulting into the nymph. This can happen, for example, if they didn't have enough space to molt and thus dry their legs in a twisted position. It can also happen that legs do not come out of the skin properly and the rest of the legs, which are still in the skin, die. If these deformed legs severely restrict the spider's movement, we as keepers should intervene and autotomize these legs. In the first part of the video you can see a nymph that has significant coordination difficulties because the right hind leg is rotated under the body.
Autotomizing doesn't cause any major problems with the spider. The wound is quickly closed by muscle contraction.
You can get the spider to autotomize by grabbing the femur of the affected leg with tweezers and pulling it up. The leg is thrown off at a predetermined breaking point between the coxa and trochanter. Experiments have shown that the spider does this willingly. Anesthetized spiders cannot autotomize their legs (Bonnet 1930). Eisner & Camazine write in 1983 "Under experimental conditions, when spiders are injected into the leg with bee or wasp venom, they shed this appendage. But, if they are injected with only saline, they rarely autotomize the leg, indicating it is not the physical injection or the ingress of fluid per se that causes autotomy.In addition, spiders injected with venom components which cause injected humans to report pain (serotonin, histamine, phospholipase A2 and melittin) autotomize the leg, but if the injections contain venom components which do not cause pain to humans, autotomy does not occur."
If you want to carry out genetic analysis on your tarantula, you can, for example, also autotomize one leg (preferably the 3rd leg) and thus obtain enough genetic material.
The video shows a small tarantula nymph sent to us by Tim Hanl who had significant coordination problems from the molting with twisted and crippled legs. Due to a lack of technical equipment, Tim sent usthis Spider, which we were then able to free from their deformed and disturbing leg with the help of autotomizing. Usually the spiders recover fairly quickly and at the next molt, which soon follows in small Nymphys, these legs are replaced with fully functional but shorter legs. At the end of the video you can see a subadult female having a leg autotomized to obtain genetic material. In the meantime, this leg has been completely replaced after two moults and can no longer be distinguished from the other legs.
Refernece:
Bonnet,P. (1930): La mue,l’autotomie et la régéneration chez les Araignées, avec une étude des Dolomédes d’Europe. Bull.Soc.Hist.Nat. Toulouse 59, 237-700
Dahl, F. (1902). Über abgebrochene Copulationsorgane männlicher Spinnen im Körper der Weibchen. Sitzungsberichte der Gesellschaft Naturforschender Freunde zu Berlin 1902: 36-45.
Kralj-Fišer, S., Kuntner, M. (2012).Eunuchs as better fighters?. Naturwissenschaften 99, 95–101
Uhl, G., Nessler, S. H. & Schneider, J. M. (2010). Securing paternity in spiders? A review on occurrence and effects of mating plugs and male genital mutilation. Genetica 138: 75-104.
YouCut_20220320_125935961.mp4