"Tarantulas Have 2 Left Feet When It's Hot" - study regarding leg coordination of A. hentzi

[edesign]

http://www.livescience.com/50348-tarantula-temperature-coordination.html

Excerpts:

"The researchers studied eight adult Texas brown tarantulas (Aphonopelma hentzi). They tested the spiders' speed and agility at four different temperatures: 59, 75, 88 and 104 degrees Fahrenheit (15, 24, 31 and 40 degrees Celsius). When the spiders were placed in temperatures that were higher or lower than that range, they tended to turn around and get into an attack stance, Ahn said."

"But at the higher temperatures, and the faster running speed, the two joints were less coupled," or less coordinated, Ahn said. "The two joints on each leg were a lot less well controlled at the higher temperatures."

"To give an idea of the spiders' speed, imagine a 2.1-inch (5.5 centimeters) tarantula. On average, the spiders moved about four body lengths a second at 62 F (17 C), and about 10 body lengths a second at 100 F (38 C), a 2.5-fold increase."

That last paragraph makes it obvious why it it is recommended to transfer/maintain more challenging specimens when it's a cool morning :wideyed: And obviously 100F is an extreme.

 

[8Legs8Eyes]

Very interesting! Thanks for sharing

 

[Tygarys]

What happens to the other 2 left feet when it gets hot?

(Sorry, had to ask!)

 

[Dovey]

When the spiders were placed in temperatures that were higher or lower than that range, they tended to turn around and get into an attack stance, Ahn said."

Um, so would I.

 

[edesign]

What happens to the other 2 left feet when it gets hot?

(Sorry, had to ask!)

lol, good question, I didn't even catch that the title is missing a few feet!

Um, so would I.

No doubt, especially the heat. I was waiting for someone to say it should be "defense stance"

 

[edesign]

From the actual study and to expand on the note in the link above regarding speed, the stride length of the hentzi did not change, only the frequency, and became less coordinated as speed/temp increased. The study also discusses the viscosity of the hemolymph versus temperature. All T's were acclimated to the testing temp for one hour prior to testing. The discussion section is fascinating and worth a few minutes to read if you're remotely curious about how T's move and what might limit their top speed. Lots of other factors that could be in play are noted.

Full study here:
http://jeb.biologists.org/content/jexbio/218/7/977.full.pdf

To change walking and running speed, animals can vary stride frequency and/or stride length. The contributions of stride frequency and stride length to modulate locomotor speed differ among arthropod species, and can also change with speed within a given species. Cockroaches, for example, vary stride frequency more at lower speeds, while varying stride length at higher speeds (Full and Tu, 1991). Grammostola tarantulas and Hololena spiders increase both stride length and frequency when increasing speed (Biancardi et al., 2011; Spagna et al., 2011). However, variation in running speed is due exclusively to variation in stride frequency in Brachypelma tarantulas and teneriffid mites (Anderson and Prestwich, 1985; Wu et al., 2010).

Instead, as temperature and stride frequency increased, the proximal and distal hydraulically extended, in-series joints of the forelegs and hindlegs in the tarantulas were less tightly coupled (Figs 5, 6), which supports hypothesis 2. Stride frequency may limit the time available for hemolymph to flow completely into and out of the leg.

The current study did not consider the possible effects of desiccation and drier air at increased temperatures that could negatively affect the hydraulic mechanism by increasing the hemolymph osmolality (Punzo, 1991).

 

[Dovey]

"The current study did not consider the possible effects of desiccation and drier air at increased temperatures that could negatively affect the hydraulic mechanism by increasing the hemolymph osmolality (Punzo, 1991)."

What, it's a dry heat?