Close up view of the amazing rotating hooks on a freshly thawed colossal squid
More news from the squid tank. This morning I caught up with Robert Clendon the conservator who is looking after the work on the squid.
Over the past few weeks we’ve been a bit concerned about the hooks on the tentacles and the arms. It looked as though the hooks could be disappearing. Not something we wanted to hear, as these are one of the most interesting and distinctive features of the colossal squid.
Robert has been away in Wichita, Kansas looking after Te Papa’s touring exhibition Whales | Tohorā so we had to wait until he was back to see what could be going on.
With the lid off the tank and some of the liquid drained away Robert has been able to take a good look at the hooks. We’re happy to hear the excellent news that the hooks aren’t dissolving – it just looks that way!
The hooks on the squid’s tentacles and arms have tissue around them. When the squid was first thawed and dissected the hooks were very prominent and stood well up from the surrounding tissue.
After being preserved and sitting in the glycol for several months the tissue around the hooks has swelled up and is now covering more of the hooks.
So it just looks as if the hooks have disappeared, but in fact they are still there – which is a relief. A colossal squid with no amazing, big hooks is not a good look.
The hooks seem to grab everyone’s attention, so here’s an update
tentacle club swivelling hook and arm sucker dissected out from the fleshy suckers
Other squid families have hooks on the arms, or the tentacles, or both, but the colossal squid is the only hooked squid in its family (the Cranchiidae, about 20 species). It possesses hooks on each of the eight arms, and also on the club ends of the two long tentacles, but the arm-hooks and tentacle-hooks are very different.
The tentacular hooks are the swivelling hooks. Each sits on a short stalk, flush with the oral surface of the tentacle club, in a flattened depression that allows the flattened ‘back’ surface of the hook to rotate. The hooks can swivel 360 to 720 degrees, but it is not known whether the squid actively controls each hook individually, or whether the hooks swivel passively once latched onto the prey, in order to keep the best grip. There are 22 to 25 hooks in two rows on the middle part (manus) of the tentacle club, and each row is flanked by a row of tiny marginal suckers. The swivelling hooks are smaller than those on the arms and have only a singe main ‘claw.’
The arm hooks do not swivel. They are set in a double row in the middle of each arm, preceded and followed by the more standard toothed suckers. The arm hooks are set in fleshy, very muscular sheaths and are strongly attached to the arms. They are likely to assist in holding and immobilising struggling prey as it is being killed and eaten. Most of the arm hooks have the main strong ‘claw’, and also two smaller auxiliary cusps closer to the hook’s base, making them three-pointed and maximising their ability to hold and dig in. The base of each hook also has a complex structure that is set deep into the surrounding musculature. The top picture shows the hook and serrated sucker im structure dissected out from the fleshy part of the suckers.
Non-swivelling arm hooks
Now that we have some time, we will upload some of the other photos taken.
Dr Tsunemi Kubodera, Steve O’Shea and Olaf Blaauw examine the smaller, damaged colossal squid on Tuesday, 29th April. Below are some of the close ups of the tentacles, suckers and hooks.
You can find out more about the hooks and suckers here
http://blog.tepapa.govt.nz/2008/04/30/hooks-and-suckers/
