The bizarre mating rituals of deep-sea squid have been revealed in a recent investigation by Dutch marine biologist Henk-Jan Hoving.
Hoving, who was recently awarded a PhD by the University of Groningen for this research, studied the reproductive techniques of ten different species of deep-sea squid and cuttlefish ranging from sizes of 25 mm to 12 m, and has uncovered some fascinating insights into the biology of these molluscs.
He found that the males of the species Taningia danae give the females cuts of at least 5 cm deep in their necks with their beaks or hooks before inserting spermatophores (packets of sperm) into the cuts.
In another species (Onykia ingens, formerly Moroteuthis ingens), the spermatophores are introduced less violently and enter the skin of females by secreting an enzyme-like substance that dissolves tissues, a phenomenon that Hoving was the first to prove by placing spermatophores on the skin of freshly caught individuals.
This observation was supported by a bizarre incident in Japan, where a diner had to undergo an operation to remove a spermatophore lodged in his throat after eating squid.
The mini squid Heteroteuthis dipar was found to be an internally fertilizing species. Females possess a special pouch in their bodies in which the sperm is stored, with the stored sperm accounting for up to 3% of its body weight.
Some males of the species Ancistrocheirus lesueurii resemble females externally. Hoving speculates that this may either be the result of anthropogenic hormones or hormone-like substances in the water, or an adaptation to allow the males to get closer to the females.
Hoving hopes that his research will contribute to sustainable exploitation of the deep ocean. Fishing is taking place at deeper and deeper depths. The deep ocean is a very vulnerable ecosystem, however. We desperately need to learn more about this ecosystem.
For more information, see also the following papers:
Hoving, HJT and V Laptikhovsky (2007) Getting under the skin: autonomous implantation of squid spermatophores. The Biological Bulletin 212, pp. 177"179.
Hoving, HJT, MAC Roeleveld, MR Lipinski and Y Melo (2004) Reproductive system of the giant squid Architeuthis in South African waters. Journal of Zoology 264, pp. 153"169.
Hoving, HJT, MAC Roeleveld, MR Lipinski and JJ Videler (2006) Nidamental glands in males of the oceanic squid Ancistrocheirus lesueurii (Cephalopoda: Ancistrocheiridae) " sex change or intersexuality? Journal of Zoology 269, pp. 341"348.