Wonderful! What great pics!
(P.S. Don't trust the old quasi-glossary thing where you got "spermaphors", that's not actually a thing and that quasi-glossary is all kinds of wrong. I'm currently working on rewriting it. Sadly, I'm obligated to use terms for parts like "palpal bulb", "cymbium", "embolus", etc., to describe the palpal glands, rather than "weenie fingers". lol)
But what fantastic pics, such great shots of the anatomy, thanks for sharing!
@CommanderBacon I think it's awesome that you want to know, thank you. Yay good information, yay you!
That paper is accurate of course, but misleading- it's about Phildromjs cespitum, which is a crab spider in an entirely different family and infraorder (family: Philodromidae infraorder: Araneomorphae). Tarantulas are in the family Theraphosidae and infraorder Mygalomorphae. Palpal gland anatomy often varies species to species, and there can be big differences genus to genus and family to family and infraorder to infraorder. For example, the Theraphosidae don't have spermaphors, not a thing for them. The three main structures in Theraphosidae are the cymbium, palpal bulb, and embolus. Together they make up the palpal gland of the males' pedipalp. (Of course you could get more technical, but those three are the gist.) The cymbium was the tarsal segment of the pedipalp and ultimately becomes the kinda protective housing for everything, the palpal bulb is the roundish vessel that holds the sperm, and the embolus is the tube that sucks up the sperm into the palpal bulb.
@Feral That paper seems to be concerned with the shape of the outer structures, not the inner structures, which I am discussing. My presumption is that all male spider anatomy more or less would have the same function and same major components, and this appears to be confirmed by Rainer F Foelix's Biology of Spiders book, which I am looking at right now. Do you have something that calls the sperm ducts within the emboli something else?
You were saying that you see an internal stucture in those photos? I don't understand that.
In any case...
The various parts of the palps in male spiders vary quite a bit, with the Mygalomorphae having a relatively simplistic structure compared to some other "true" spiders. Not all structures are homologous. In Theraphosidae and similar spiders, I've just seen the internal structure that carries the sperm to terminate at the embolus as being called the seminal duct. The Wikipedia page on palpal glands does a fairly good job at explaining some anatomical differences and varying complexity phylogenetically, as well as how/why some spiders evolved more complicated palpal glands than others: https://en.m.wikipedia.org/wiki/Palpal_bulb
My assumption is that the spermaphor structure is found within spiders who transfer spermatozoa via spermatophores, instead of just sperm (like Theraphosidae do), but I'm still trying to find explicit confirmation of this. Whatever the reason, I've never seen spermaphor it in Mygalomorphae.
On that page you can see the second image is three different views of the palpal organs of Thaida chepu, which is relatively complex, compared to the third image of the palpal organs of Unicorn catleyi, which is much simpler and very similar to the structure of a Theraphosid.