Sclerotised spermatheca

[PhilBugs]

I often see reference to waiting until the spermatheca is sclerotised before a female is mature, however, I can't find any information on what the indicators that a spermatheca is sclerotised are. Is it just colour?

Does the spermatheca in the attached photo look sclerotised or not?

 

[viper69]

To me yes

 

[fcat]

It feels rigid, hardens, and if you have previous molts to compare to, the color of the tissue becomes darker. The species I'm familiar with anyway.

You should be able to 'feel' how firm it is even with an accessory/tool, it won't be jelly like the rest of the tissue...

 

[PhilBugs]

It feels rigid, hardens, and if you have previous molts to compare to, the color of the tissue becomes darker. The species I'm familiar with anyway.

You should be able to 'feel' how firm it is even with an accessory/tool, it won't be jelly like the rest of the tissue...

Thank you, that's useful advice.

 

[cold blood]

Does the spermatheca in the attached photo look sclerotised or not?

not to me

 

[IntermittentSygnal]

Is there any other way to know if a female is mature without the molt?

 

[gabrieldezzi]

Is there any other way to know if a female is mature without the molt?

I thought the general rule was if the female was 75% of adult full size but I’m not sure how true that is.

 

[l4nsky]

Maturity can best be judged by size for the species and the darkening of the spermatheca. You can make a guess with one piece of the puzzle, but both are better. Without knowing the species or size, my guess is the same as @cold blood, this female isn't mature yet. The spermatheca will be much darker in their entirety once mature. For reference here's a MF Phormingochilus sp Akcaya who was a bit over 6" DLS at the time:

P Akcaya Female Spermatheca (1).jpg

• l4nsky
• Aug 21, 2021
• akcaya female phormingochilus phormingochilus sp "akcaya" spermatheca

0.1 Phormingochilus sp Akcaya, ~6.25" DLS

 

[cold blood]

I thought the general rule was if the female was 75% of adult full size but I’m not sure how true that is.

its not...very often females are mature way earlier than that.

 

[fcat]

Is there any other way to know if a female is mature without the molt?

I thought the general rule was if the female was 75% of adult full size but I’m not sure how true that is.

I had a young tappie drop a sac at about 50% of her max size...just barely 2" at the time. Then she molted and finally achieved her adult coloring. She was still a baby to me

 

[spideyspinneret78]

It looks to me like the process is starting, but she's not quite mature yet. Might be ready for breeding within the next molt or two.

 

[PhilBugs]

Maturity can best be judged by size for the species and the darkening of the spermatheca. You can make a guess with one piece of the puzzle, but both are better. Without knowing the species or size, my guess is the same as @cold blood, this female isn't mature yet. The spermatheca will be much darker in their entirety once mature. For reference here's a MF Phormingochilus sp Akcaya who was a bit over 6" DLS at the time:

P Akcaya Female Spermatheca (1).jpg

• l4nsky
• Aug 21, 2021
• akcaya female phormingochilus phormingochilus sp "akcaya" spermatheca

0.1 Phormingochilus sp Akcaya, ~6.25" DLS

The species is Psalmopoeus irminia and by size I'd guess that she is maybe 2 moults until MF. I also feel like her spermatheca is only partly darkened.

Thanks for your input (and everyone else who has contributed to the thread). I feel like 'sclerotised' is a term that is thrown around with an assumption that everyone knows exactly what it looks like whereas in reality it's not always something that can be judged at a glance unless you are familiar with mature females of that particular species. As you say, it's just one piece of the puzzle.

 

[AphonopelmaTX]

I feel like 'sclerotised' is a term that is thrown around with an assumption that everyone knows exactly what it looks like whereas in reality it's not always something that can be judged at a glance unless you are familiar with mature females of that particular species. As you say, it's just one piece of the puzzle.

You are exactly right and this is why the generalized advice of looking for the hardening of the spermathecae is not a good way to determine if your female tarantula is mature and ready for breeding.

As you see in the Psalmopeous species, not all tarantulas have sclerotized spermathecae and others have various levels of hardening. In the taxonomic literature, subjective terms such as weakly, highly, strongly, etc. are used to describe the various levels of hardening, but the pictures in the research papers are far more telling. From the included picture of Psalmopoeus irminia you could describe the spermathecae as having the distal ends of the receptacles as strongly sclerotized, but not at all sclerotized from the base to the subapical restriction.

Species of the genus Thrixopelma have strongly sclerotized spermathecae even as small immatures which makes the generalized suggestion of looking for the hardening as an indicator of sexually maturity even more ill advised. Species of the genera Grammostola and Aphonopelma have weakly sclerotized spermathecae which fully develop at immature stadia. Species of Brachypelma have moderately to strongly sclerotized spermathecae which develop at immature stadia, but Brachypelma spp. (as well as Aphonopelma spp.) have baseplates seen in ventral view when removed from the abdominal wall which are strongly sclerotized providing a better indication of maturity.

The commonly repeated statement of looking for sclerotization of the spermathecae as an indicator of sexually maturity doesn't even consider species which don't have spermathecae at all!