Curiosty , What is the "HORN" for in the -Chilobrachys- species

seanrc

Arachnoknight
Old Timer
Joined
Aug 2, 2006
Messages
165
ive noticed there the only ones who have the HORN ..
i looked it up and i got multiple answers. so i cant rely on those so by anychance do any of you guys know?
 

butch4skin

Arachnoprince
Old Timer
Joined
Feb 15, 2007
Messages
1,380
I believe you mean the Ceratogyrus genus. Though none know for sure, some have speculated that, being from semi-arid environments, the "horn" of these sp. serves as an anchor for increased musculature associated with the sucking stomach(supposedly enabling the spider to "suck up" fluids faster, in preperation for innevitable drought), and also that the "horn serves as a hollow cavity that the sucking stomach can expand into to store fluid and nutrition for lean times. That said, it should be noted that not all Ceratogyrus sp. have this growth, though they may live in equally arid environments as those that do.
 

butch4skin

Arachnoprince
Old Timer
Joined
Feb 15, 2007
Messages
1,380
I believe you mean the Ceratogyrus genus. Though none know for sure, some have speculated that, being from semi-arid environments, the "horn" of these sp. serves as an anchor for increased musculature associated with the sucking stomach(supposedly enabling the spider to "suck up" fluids faster, in preperation for innevitable drought), and also that the "horn" serves as a hollow cavity that the sucking stomach can expand into to store fluid and nutrition for lean times. That said, it should be noted that not all Ceratogyrus sp. have this growth, though they may live in equally arid environments as those that do.
 

Fenrir

Arachnosquire
Old Timer
Joined
Sep 23, 2007
Messages
119
No one is 100% positive what its for but gsal28's explanation sounds good.
 

butch4skin

Arachnoprince
Old Timer
Joined
Feb 15, 2007
Messages
1,380
Heh, not really my explanation, just something I read somewhere. I think that was Rick West's theory regarding the subject, actually.
 

lucanidae

Arachnoprince
Old Timer
Joined
Jan 15, 2006
Messages
1,081
Don't forget also there is a new world species Sphaerobothria hoffmani that has a small horn. I've dissected the horn on three Ceratogyrus species and I'm doubtful of the faster/expanded stomach hypothesis; the cavity is far too small to make a difference. What is really interesting about the horn is how far it goes into the body, not out of it.
 

butch4skin

Arachnoprince
Old Timer
Joined
Feb 15, 2007
Messages
1,380
Don't forget also there is a new world species Sphaerobothria hoffmani that has a small horn. I've dissected the horn on three Ceratogyrus species and I'm doubtful of the faster/expanded stomach hypothesis; the cavity is far too small to make a difference. What is really interesting about the horn is how far it goes into the body, not out of it.
Is S. hoffmani even a xeric sp.?
 

Mina

Arachnoking
Old Timer
Joined
Oct 4, 2005
Messages
2,136
The only reason for the horn I've ever heard suggested was that it was for different muscle attachments. I didn't understand it at the time. I don't think that they are any faster or have an abilities that any T without a horn would have.
No idea really. Good question!
 

lucanidae

Arachnoprince
Old Timer
Joined
Jan 15, 2006
Messages
1,081
Is S. hoffmani even a xeric sp.?
No, I believe most of it's range is in Costa Rica and can't imagine it is hurting much for water. Like I said, the volume that even that largest horns can hold is pretty small when compared to the body. I really don't think the adaptive value has anything to do with the external horn; the movement of muscle and gut into that space is probably an aftereffect of the extension of the fovea.
 
Top