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.
Clem