You probably have this reference, but just in case...it is from the Journal of Morphology
Takahama, H., Kinoshita, T., Sato, M. and F. Sasakim, 1991,
Fine structure of the spermatophores and their ejaculated forms, sperm reservoirs, of the Japanese common squid, Todarodes pacificus,
Journal of Morphology 207(3), 241-251.
*Correspondence to Fumie Sasaki, Department of Biology, School of Dental Medicine, Tsurumi University, 2-1-3 Tsurumi, Tsurumi-ku, Yokohama 230, Japan
Spermatophores in a squid, Todarodes pacificus, were observed by light and electron microscopy and were further analyzed by X-ray microanalysis (XMA) of frozen thin sections. Each spermatophore consists of a sperm mass, a cement body, an ejaculatory apparatus, and some fluid materials, all of which are covered by an outer tunic. The outer tunic consists of about 20 membranous layers, each containing straight, parallel microgrooves. Each layer's microgroove pattern is roughly in an orthogonal arrangement with respect to the next layer's pattern. The sperm mass, which is the only cellular component, consists of a sperm rope which is coiled more than 500 times. Most of the spermatozoa in the rope are arranged regularly and are enveloped in materials which are well-stained by Alcian blue. The cement body is located between the sperm mass and ejaculatory apparatus and has a hard outer shell with an arrowhead-like structure, presumably for penetration into the tissue of the female. Calcium and phosphorus are present in the shell of the cement body, which also has an affinity for alizarin red. The ejaculatory apparatus consists of two tubes, designated as the inner tunic and the inner membrane.
After the spermatophoric reaction, a sperm reservoir is formed at the anterior end of the extruded and inverted ejaculatory apparatus. The sperm reservoir, which encases the sperm mass, is composed of the cement body at the anterior end and the inner tunic of the ejaculatory apparatus at the posterior end.
A bit late, but I'm inclined to agree with the previously stated theory that the sperm are release out into the water instead of into the mantle. That is what I was thinking as I read your inital post, Kat, only to find that others had come to the same conclusion.
And as far as the release factor goes, I prefer the chemical signal idea instead of direct manipulation. The chemical signals could come from the female, but I think it would be more likely to come from the eggs/egg mass. If the female signalled for the sperm to be released, the timing would have to be exceptional as she has to release the eggs and manipulate them towards the spermatophores before the sperm is released. Hormones released into the blood would take time to reach the spermatophores, and I don't think she wants to be caught mid-way through the procedure by a sperm whale. Instead, I think that she lays her eggs, mixes them with the jelly to make the egg mass and then places that near the spermatophores. The chemical signals are received due to proximity to the egg mas and it is showered with sperm. However, I'm not sure if sperm would be able to find the eggs to fertilize them through the jelly. Hmmmm...
Hey guys, sorry for floating this thread and then apparently abandoning it. I am still puzzling this out, and have been corresponding with a few other ceph-heads about it. The latest development is that Dick Young was in Bergen, where he examined the Type of Chaunoteuthis mollis, and took the attached photo for me of... the same kind of implanted spermatophores! (Actually, spermatangia - and thanks for posting that animation, that was very cool.) C. mollis appears to be a spent Onychoteuthis, but we don't know what species yet - tentacles are lost of course, so the beaks need examining.
I like the theory about the sperm being released through (or creating) the external bulb-like structures, especially since the implanted spermatangia in the male O. meridiopacifica don't have this structure, and wouldn't have released the sperm.