Indeed Joel, that's a good point. Obviousdly I have no idea, but perhaps the sleeper attacks the squid from the rear, avoiding the arms. Unless of course the sleeper is just scavenging corpses. Mind you, that would imply the shark inhabits a benthic environment at the sea bed, I've no idea if this accurate or not.
I'm going to have to look up sleeper sharks, this is all very interesting.
What a buzz!! The 'Colossal Squid' is now recognised as bigger and meaner than the 'Giant Squid' in popular press!! (even if the length of the giant squid depicted in the illustration is cited as 18m, and in text 12m).
I do like the statement that the sharks are taking larger squid (on average) than the sperm whale ....... it means that the beaks we have from whale stomachs might not be the largest beaks known (that the animal could get larger than we know ....)
.... I'll write to Yves (he's a squid beak guru; we're hoping he'll be here this year) and enquire about the citation 'Giant Squid' in Antarctic waters. Architeuthis isn't supposed to move into Antarctic waters (this could be a press booboo). Of course the blue shark is also known to take the adult Architeuthis (and I believe maybe another shark species also), but that doesn't matter - I think they're talking Mesonychoteuthis more than anything.
The actual article cites a maximum LRL of 38.8mm (mean 22.3mm) for M. hamiltoni beaks found in the sharks' stomachs. Estimated ML for the owner of that beak is 2.37 m (apparently). Based on some of the pictures of the Sepioteuthis juvies, I wouldn't be surprised to see that Messie eating the shark.
Cherel, Y. & Duhamel, G. Antarctic jaws: cephalopod prey of sharks in Kerguelen waters. Deep-Sea Research I51, 17-31 (2004).
Good point, um..., and that was my question as well. Now, Pacific sleeper sharks have been known to grow to immense size (great white size and above), but an active predator of the Messie? That sounds interesting... I mean, wouldn't a massie put up a hell of a fight?
Oh, and Steve.. Do you still think the messie is an active hunter or ambush pred like archi?
Oh, and if these are scavenged, does that mean that they may be eating the casualties left ovr after mating and egg-laying, like the Loligo die off we see off the coast in CA after mating?
Stomach contents regularly contained whole specimens of Patagonian toothfish, and discarded fish heads of that species (fishery waste), which were most likely eaten directly in trawls and scavenged at the bottom, respectively. Other prey items were demersal fishes (mainly the skates Bathyraja irrasa and B. eatonii, and the nototheniids Notothenia rossii and Lepidonotothen squamifrons), benthic invertebrates (e.g. sea stars, ophiurids) and carrion. The stomach of nine sharks contained big chunks of flesh (up to 30 kg), which, in 2 cases, were identified as belonging to fur seals (probably the Antarctic fur seal Arctocephalus gazella).
The Greenland sleeper shark is a sluggish creature which dines on active fish like char! How??
Many puzzles still to be sorted out.
Sleepers are known to be persistant feeders on waste animal material, and difficult to drive off.
I saw a docu on animal planet showing sleeper sharks along with hagfish and others feeding on a sunken grey whale carcass. The fish really looked slow and senile,maybe a few of the sharks ate a giant squid carcass and was caught before all of it was digested?
Hmm...this may be a stupid question but if Architeuthis body tissues are saturated with ammonia keeping the animal buoyant, following death would one expect the carcass to rise to the surface, remain floating at depth with a neutral buoyancy before breaking up, or sink to the bottom? Without propulsive power from the fins would the dead animal rise like a cork in a bottle or do the ammonia ions keep it perfectly in balance, as I suspect?
If the sleeper sharks are feeding off corpses, I wonder if the scenario is that they are feeding off drifting bodies or scavenging on the sea bed.
I'd like most to know how far along in the digestive process the squids had advanced before the sleepers were captured, and how long (approx) the sharks had been in the nets before being examined. One possibility is that the sharks find themselves in the nets with the squid and consume them before expiring; that's why I'd be keen to know what condition the squid were in.
Though the sleepers appear quite placid, they are very powerful animals, and well equipped with the sensory panoply that makes sharks such effective hunters. And, despite their huge eyes, even Colossals have blind spots.
Have read that many Greenland shark (Somniosus microcephalus) have a crustacean parasite living on the eye which must render the fish virtually blind. The thought has been raised that they may attract fish by emitting light?
Mentioned in "Sharks of the World" by Rodney Steel, but remember reading more than I can find in that book.
First, big thanks to um.... for supplying Cherel & Duhamel’s paper. VERY interesting stuff.
Although the sleeper shark may be the most spectacular individual shark surveyed, I gotta say, the lantern shark is just as interesting. The ventral surface of this small shark is luminescent, which has led some to speculate that this schooling animal uses light to maintain cohesive formations in the lightless, benthic realm. These schools should also be capable of killing prey items much larger then the individual sharks (which average less than 18 inches in length). (I think schooling attacks on Mesonychoteuthis may have been proposed by some smart person over in the “Colossal Squid Necroscopy” thread.)
Somniosus, the sleeper, is described by Cherel & Duhamel as an almost exclusively benthic predator and scavenger, but in other parts of the world the local sleeper variants are known to feed at the surface, especially where carrion and offal are ejected by fisheries. In that scenario, they would likely follow the trail of descending bits up from the deep to the source. For the most part, however, sleepers stick to the mud. What sticks out from Cherel & Duhamel’s benthic model for Somniosus is the presence of big Architeuthis, up to 220cm mantle length as indicated by recovered beaks. If Archis become more ammoniacal as they mature, and “sink up” when they die, then it seems unlikely that these very large specimens found in Somniosus were scavenged off the sea-floor. Does Archi spend time in the mud, then, or is something else happening?
As for the lack of the vicious scarring about the head associated with Mesonychoteuthis in their death throes, perhaps Somniosus has a particularly thick skin? One very interesting thing about the sleeper is the fact that fish found in its stomach often lack tails. If the shark does in fact use luminescence about its eyes to attract prey, then the tail-less condition of the fish can be explained by the head-first attitude of the attracted prey; they swim in for a look, and the shark snaps them up, severing the caudals. Likewise, if Somniosus of the Antartctic is using glowing peepers to reel in big squid, it can dispatch its prey quickly enough to avoid being injured by arm-hooks.
The bottom of the Southern Ocean must be a scary place.
What sticks out from Cherel & Duhamel’s benthic model for Somniosus is the presence of big Architeuthis, up to 220cm mantle length as indicated by recovered beaks. If Archis become more ammoniacal as they mature, and “sink up” when they die, then it seems unlikely that these very large specimens found in Somniosus were scavenged off the sea-floor. Does Archi spend time in the mud, then, or is something else happening?
Archi's of 220cm ML are female and fully mature/spent. I'll bet a dollar that these animals were not taken in Antarctic waters (about as sure as I am about anything anymore), but were recovered from sharks in subantarctic waters, or sharks that have undertaken some migration from subantarctic waters, or were taken next to some Antarctic/subantarctic water mass convergence. I've yet to read the paper ... tiz sitting in my briefcase right now ...
IF Archi truly is found in the Antarctic then it will open up a can of worms ..... Maybe there's another large-bodied squid down there with Architeuthis-type beaks (this cannot be discounted if the beaks are truly Antarctic in origin). My office is full of worms ... nothing surprises me anymore ... deja vu.
I don't know what effect temperature would have on buoyancy; anyone want to comment?
Unless there is something funny with ammonia (I've worked with gallons of the stuff but only at room temperature) then cooler water is denser and so has a greater bouyancy but if it cools the squid then the squid will also be less bouyant. However, a dead squid would tend to cool and so become less bouyant and, atlhough you'd pos. have to do some sums, a dead squid would be more likely to sink in colder water than warmer water. You could imagine a current carrying dead squid carcasses into colder waters where the squid might sink to the bottom.