Nine image curly haired tarantula (Brachypelma albopilosum) molt sequence
March 2, 2012 by allthingsbiological
Tarantulas, like other arthropods, must periodically shed their old exoskeleton to allow for growth. The new, softer shrunken exoskeleton is produced under the old exoskeleton. The frequency of this shedding (referred to as ecdysis or molting) varies. Young spiderlings shed numerous times during a year, while mature females, which may live up to 40 years, may shed every other year.
- Toward the end of premolt, the period prior to molting, activity becomes limited as muscles detach from the old exoskeleton and connect to the new, slightly larger, folded, inner exoskeleton. Exuvial fluid is then secreted between the inner and outer exoskeletons. Enzymes digest the endocuticle, effectively separating the two skeletons.
The transitory period between premolt and the actual molt is signaled by the tarantula spinning a bowl-shaped web, often called a molting mat or molting cradle. The spider then rolls over and remains relatively stationary, aside from limited leg movements, for an extended period. This was how I discovered the tarantula Sunday afternoon.
At the beginning of the molt, the carapace loosens, allowing for full view of the new, much enlarged chelicerae.
The tarantula slowly emerges from its old exoskeleton using continual, virtually imperceptible pumping motions. Molt duration ranges from 20 minutes (young spiderlings) to several days (mature females). The photos comprising this sequence were taken over a five hour period.
After molting the spider remains upside down for several hours, moving its legs slightly.
During the molt, the tarantula is entirely helpless. Flight or defense are not possible. The hours really did feel like hours...
It is important not to handle the tarantula from pre-molt to the point that the tarantula will accept food. I try to stay strictly hands off throughout the entire molting process and next several days afterward. This spider (which I had purchased several days prior) was in a container that was smaller than ideal for its size. The spider moved all of the coconut mulch bedding to one side the day prior, and was upside down on a smooth plastic ridged surface, struggling to find a foothold. I knew that was bad, and it certainly would not have been the case in a more natural setting. As I moved the bedding so that it could gain a foothold, one leg came into contact with my finger. I certainly didn't want to push it off at that point, so I let it attach to my hand, right itself, and then move off on its own to the newly spread bedding.
During the next several days, designated post-molt, hemolymph movement within the body, causes the body to expand, resulting in a larger size. During this time cross linkages occur between molecules comprising the exoskeleton. The linings of the mouth, pharynx and pumping stomach are also shed, so the tarantula will not be able to eat until the new parts harden.