LOLIGO GAHI – KELP FORESTS HIDE A FASCINATING STORY
The Falklands calamary, Loligo gahi
Almost everyone would agree that the Loligo squid or calamary is one of the tastiest sea creatures. Even before the Iron Age they were sought after by humans for food and also featured in ancient artworks. Loligo were one of the most popular subjects depicted on Cretan platters and were no doubt consumed by offended Mycenaeans while they sharpened their bronze swords and plotted revenge against Troy for the abduction of the beautiful Helen. Important things attract much attention and squid reproduction was investigated first by the ancient Greeks and then described by Aristotle in about 350 B.C. (a century after the “300 Spartans” event). He wrote:
Molluscs, such as the octopus, the sepia, and the calamary, have sexual intercourse all in the same way; that is to say, they unite at the mouth, by an interlacing of their tentacles. Some assert that the male has a kind of penis in one of his tentacles, and that the latter enables it to enter the nostril or funnel of the female… Now calamaries swim about closely intertwined, with mouths and tentacles facing one another and fitting closely together, and swim thus in opposite directions; and they fit their so-called nostrils into one another, and the one sex swims backwards and the other frontwards during the operation. And the female lays its spawn by the so-called 'blow-hole'; and, by the way, some declare that it is at this organ that the coition really takes place.
A close look at the everchanging chromatophores.This very precise description was also very accurate. How was it possible for the Greek scientists of antiquity to observe this behaviour without SCUBA equipment, indeed even without a simple snorkel and mask? Yes, male Loligo squid has a specialised arm which acts as a kind of penis. Squid sperm is packed into worm-like tubes called spermatophores (scientists did think for a while they actually were worms) and the male simply grasps an armful of them and places it inside the female via her funnel, the ‘blow-hole’ of Aristotle. Alternatively, they can also employ a type of oral sex during which spermatophores are placed at the female’s mouth, where the seminal receptacle is situated. Females can store sperm in this receptacle for several weeks or months, and actually do not need an immediate male presence to lay eggs. However, spawning grounds are always attended by large numbers of competing males, some having harems and some opportunists sneaking to a neighbour’s ‘garden’. In some loliginid species these aggregations are so abundant they can provide a valuable resource for both fishermen and fish. The squad’s curious reproductive behaviour was studied in all aspects over the years, including aquarial observation. For example, in the early 20th century an American scientist, Gilman Drew, decided to investigate squid’s priorities: hunger or sex. He put a hungry Loligo male in an aquarium with a female. The male subsequently demonstrated where his priorities lay, first mating with the female, and then killing and eating her.
Preparing to place the eggs in the egg cluster.
The Falkland Loligo gahi is a unique cold water species well suited to life in the harsh sub-Antarctic environment. This required several specific reproductive adaptations in response to this hostile habitat. It is the only loliginid species that does not lay its eggs on the ground, but attaches them tightly around kelp stalks instead. Being situated well clear of the seabed, these egg masses are not accessible to most of the predatory benthic invertebrates. Another particular aspect of their reproduction is that although you can find their egg masses everywhere in the kelp, you can never see them in great numbers at any single site. Each egg mass contains many egg strings often laid by different females because, for Loligo, an existing mass acts as a stimulus to add one’s eggs to it. Each string of eggs deposited in one of these clusters by L. gahi contains relatively small amount of eggs, because every female tends to put their eggs in as many baskets as possible, distributing their eggs widely in the unpredictable inshore environment around these South Atlantic islands.
Female squid placing eggs within an egg cluster.
This species appears to spawn all year round. Upon foraging on the shelf edge, females move to inshore waters to lay eggs, mostly in spring and autumn. Despite the biology of this valuable commercial species being well studied, nobody has ever seen any spawning aggregations of L. gahi
. In an exciting discovery during an expedition to the Jason Islands, which lie to the northwest of the main Falkland Islands, a spawning female was observed for the first time ever by Judith Brown and two other SMSG divers. The divers were rewarded with a close up display of a single animal adding her eggs to an existing cluster. For a Loligo
squid there is nothing unusual about that, because female can store sperm. However, it is the first record of a single spawning squid. There were no mass aggregations, no males and no harems. Just a single gravid animal which ignored the watching divers and continued carefully depositing her eggs to a kelp stalk.
Close examination of the clusters reveal the eggs within.
The Falkland Islands is a unique environment – more than seven hundred islands and islets combined with fjord-corroded shores result in an immense length of shoreline located in such a small part of the vast Atlantic ocean. Just three centuries ago these waters harboured such a huge abundance of sea birds and marine mammals, that any attempt by tasty squid to aggregate in very shallow waters for spawning would be suicidal. South African scientists demonstrated that spawning concentrations of another species, L. reynaudi
could temporarily disintegrate under extreme predatory presence. But predatory flocks and packs can not forecast the appearance of a single spawning female and we believe this underlies the spawning strategy demonstrated by L. gahi
This image shows the height above the seafloor of the egg clusters which can be seen in front of Jude Brown.
So, to increase the chances of females to successfully lay eggs, spawning by Falklands Loligo squid probably evolved to be very dispersed both in space and in time, being virtually invisible to hungry bird and dolphin eyes, as well as those of marine scientists – until now. The photographs on this page represent the only known record of this unique behaviour and are, like many scientific discoveries, the result of sheer luck (and the sharp eye of Jude Brown).
Dr Laptikhovsky examining a cluster of Loligo eggs