Common Squid eggs
Perhaps more often seen on the dinner plate than in the sea, squid are actually a common visitor to UK shores where they come to breed in the summer. Nonetheless, Egg cases belonging to the common squid made for a surprising find by researchers from the University of York after analysing thousands of photos of the seafloor here in Lamlash Bay.
Squid may not look related to scallops and clams, but they are in fact highly evolved molluscs, with substantial nervous and muscular systems, vision and intellect. Mating is equally complex, fascinating and horrifying, involving a dazzling array of luminescent colours given off by both sexes and the transfer of spermatophores (sperm-containing packages) from the male to the female. When activated by pressure, these spermatophores explode, puncturing the female’s skin and injecting the sperm inside her body. Coincidentally, this is also why squid must be prepared and cooked properly before eating.
Once pregnant, females lay their characteristic white sausage-shaped egg cases and attach them to the seabed. These cases contain hundreds and thousands of glistening transparent eggs, each containing a single squid embryo. After 2-3 weeks the tiny hatchlings enter the water column. Growth is rapid, with individuals reaching a maximum of 20cm in length after 1-2 years. Squid rarely live longer than this short time span.
Once adult, they have torpedo-like speed and agility thanks to their jet propulsion, making them voracious predators of fish and crustaceans, which they eat and tear using their sharp parrot-like beak.The common squid is also a vital food source to many larger fish and mammals.
By Prêtre [Public domain or Public domain], via Wikimedia Commons
The common squid has a cylindrical spotted body, with short tentacles protruding from its mouth, hiding an exceptionally sharp beak for tearing prey. Two longer tentacles either side of its body reach over half its total length, each equipped with 6-8 suckers for clasping prey. The tail is shaped like a spade from a pack of playing cards, beginning wide and curved, before tapering to a thin point. It occurs widely throughout Northern Europe and the Mediterranean, and spends the majority of its life in deeper waters between 50-500m depth. It is recorded in particularly high numbers in the Irish, Celtic and North Seas, and turns up in by-catch from bottom trawl fisheries. Despite this, the common squid is of little importance to UK fisheries, caught in small and variable quantities in the Moray Firth and other locations.
Latin name: Alloteuthis subulata
Habitat: Sandy, muddy and hard sea bottoms 50-500m depth
Distribution: From the North Sea to Portugal, and the Mediterranean
Size: Approx 20cm
Sources: FAO Species Catalogue for Fishery Purposes No. 4, Vol. 2 http://www.fao.org/docrep/014/i1920e/i1920e02.pdf
Hastie et al. (2009) Reproductive biology of the loliginid squid, Alloteuthis subulata, in the north-east Atlantic and adjacent waters Aquatic Living Resources, Vol. 22, pp 35–44
Video: Squid changing colour