Figure. Spermatophore from Doryteuthis pealii. The sperm mass is artificially colored blue. Drawing modified from Drew, 1919.
The following account is drawn from Drew (1919).
Below is an enlargement of one portion (oral end) of the above spermatophore to show the structure and secreted layers that comprise this portion. The white area is a fluid-filled space. The peculiar spiral filament is not a spring. It lines the inside wall of the middle membrane (Drew calls this wall the inner membrane) and appears to keep this tube from collapsing. The spiral filament is broken into fragments as the tube expands in diameter and the tube walls thin during ejaculation. The fragments continue to adhere to the wall of the middle membrane of the evaginated tube.
Figure. Oral end of the spermatophore of D. pealeii. Drawing modified from Drew, 1919. Colors are artificial.
Below is a simplified spermatophore that is slowly ejaculating. Compare the color-coded layers with the illustration above. The cap and thread have already come off and the middle tunic has started to swell. The ejaculation continues to the formation of the spermatangia containing the sperm mass.
Figure. Discharging spermatophore. Illustration modified from Drew, 1919. Colors match the color coding of the previous drawing.
Drew (1919) suggested that ejaculation is initiated by the male squid pulling on the thread with its arms as the spermatophore is transferred to the female. The pull causes the cap to pop off and ejaculation ensues. Ejaculation typically takes about 10 sec. The force propelling ejaculation seems to come from the tension of the elastic outer tunic and osmotic action that involves the swelling of the middle tunic. Often just placing fresh spermatophores in seawater is sufficient to initiate ejaculation so the role of the thread is uncertain.
The spermatangia is a tough sac that contains the sperm mass and an external cement material at one end. The spermatangia can often be found attached to a previously mated female by the cement and sometimes the spermatangia is embedded well into the tissue of the female presumably due to the caustic effect of the cement. Attachment sites of spermatangia vary depending on the species.
