nightfly's picture

Edit- Not Shark but Anglerfish.

Observed: 11th June 2008 By: nightflynightfly is knowledgeable about Fishnightfly’s earned reputation in Fishnightfly’s earned reputation in Fishnightfly’s earned reputation in Fish
Summer 2008 found by John and Stephen Mc Allister at Ring while riddling gravel. Jaw of a fish, small species of shark perhaps, bullhuss
Summer 2008 found by John and Stephen Mc Allister at Ring while riddling gravel. Jaw of a fish, small species of shark perhaps, bullhuss.
Summer of 2008 found by John and Stephen Mc Allister at Ring while riddling gravel. Jaw of a fish, small species of shark perhaps, bullhuss
Description:
Identifications
Species interactions

No interactions present.

Comments

nightfly's picture

This is quite similar to

This is quite similar to this:-

http://www.ispot.org.uk/node/248361#comment-101728

The above could well be an Angler Fish lower jaw?

Cathal.

ChrisMcA's picture

(just following your lead,

(just following your lead, obviously)

nightfly's picture

Thanks for the confirmation

Thanks for the ID and confirmation Chris. Its an impressive set of nashers. The one thing that didnt seem to fit for an angler fish was the narrow gape of the bone when viewed from above. I would have expected it to be much more openned out. But thats not from experience of taking angler fish apart, its just from looking into the wide open gubs of small anglers I used to see in a commercial salmon net in the 90's.

Cathal.

ChrisMcA's picture

you might be right, it's much

you might be right, it's much wider in the illustration.
Looking in nhm's biodiversity,
http://www.nhm.ac.uk/research-curation/scientific-resources/biodiversity...
there's another angler fish L.budegassa shallow to 500m but also pretty wide.see http://species-identification.org/species.php?species_group=fnam&id=1547
(& it's all bone where a shark's jaw's cartilage)

See also http://www.wildaboutbritain.co.uk/forums/water-life-forums/9405-unknown-...
It looks like lower jaw's in 2 parts; is the join flexible?

nightfly's picture

Hi Chris,Marineboy sounds

Hi Chris,

Marineboy sounds like he knows his stuff, do you know him?
I know shark bones are cartilage and this jaw is definitely boney but with all the 'boney' looking shark jaws pictured online I ignored this aspect. Yes this is true bone no doubt.

Those preserved sharks jaws online- are they hard like bone or flexible cartilage. Reason I ask is that they look hard and boney. Ive never had a shark jaw to hand to get the feel of it.

The join didnt seem to have any flexibility. Cant check it again until I am at my friends house again where the jaw is kept. Thanks for all the above.

Cathal.

nightfly's picture

Hi Chris, I had the

Hi Chris,

I had the opportunity to examine angler fish jaw structure at the weekend. They are hinged in the front centre. This explains the narrow posture of the jaw above. The example above has been glued together for robustness but on the living animal, the jaw is flexible and jointed at the centre.

Cathal.

dejayM's picture

'mazing..

Yes, remarkable.
Tag ProjectM1 (no gaps). Please?
ð

nightfly's picture

Hi Derek, The other

Hi Derek,

The other remarkable thing about these jaws are the collapsble teeth towards the rear of the gum. The largest teeth visible here are anchored to the jawbone by flexible stilts. The teeth collapse backwards into the mouth but lock hard if pulled in a forwards direction. They are clearly designed to take a lot of abuse but to not allow escape by struggling prey.

On the dried specimen above the flexible teeth anchors are quite rigid but on a fresh fish they are like bendy plastic. Maybe you have experienced these things before. I now have another jaw to compare with this one when the flesh has been fully removed.

Cathal.

ChrisMcA's picture

All new to me

Fascinating info Cathal; I've not yet found 1 of these

nightfly's picture

Hi Chris, Yes these teeth

Hi Chris,

Yes these teeth are an interesting design. When I first noticed the teeth lying down when touched I thought they were broken but it turns out they are designed to fall down rearwards. Being curved rearwards also, they act like many fish teeth (pike and trout come to mind) and are well shaped to grasp slippery prey.

They are like the one way road 'stinger' out of Crawfordsburn Country Park near Belfast, completely harmless in one direction and fairly hostile the other way.

Cathal.

nightfly's picture

It would be amazing to see an

It would be amazing to see an anglerfish feed in slow motion. It would tell a lot about the structure and design of the fish. Having studied the jaw structure of the fish, it is clearly designed to be a fish which is virtually flat, but only while at rest. This isn't a 'flat' fish, its a collapsible fish.

That jaw is designed to be cavernous and toothy but also to be collapsible when not in use. It is remarkable engineering. The posture of the jaw above is what it would be with the mouth open- ie, in the act of engulfing something. Once the food item is swallowed and the fish resettles to the sea bed the posture of the jaw becomes completely different as the hinge in the centre of both upper and lower mandibles alows the jaws to flex away from each other laterally.

I know there are many amazing jaw designs in fish but this one is really interesting. I played about with the posture of a fresh fish recently and discovered that the flattened shape I was familiar with was only half the story. It is not so flattened a fish at the moment of attack, its head and mouth become an open bucket into which prey larger than you might think can disappear. There were 9 and 10 inch herring folded over in the stomachs of some of the anglers I examined last week, the anglerfish were the same length as the herrings or slightly longer, 9-12 inch anglers.

Just a thought- as the entire point of this jaw seems to be to lie as flat and inconspicuous as possible when not in use, maybe the collapsible teeth are a necessary feature to facilitate the transformable mouth structure. This jaw has to go through quite a shift between resting position and eating posture, teeth of this size would have to be collapsible or they would get in the way. Jaw and teeth alike here are designed to be put away and kept out of site until the moment of attack. Im starting to think its the action of the opening jaw that makes the teeth rise into feeding mode, I need to get another fresh specimen and study the movement more.

Cathal.

dejayM's picture

Some

Yes, the more we read, the more we are amazed.
Here's some footage (as they say). The second one suggests they may not be so good at swallowing!
And 4 is a whole new look at 'chipping a fish' get it?
1 http://www.arkive.org/anglerfish/lophius-piscatorius/video-08
2 https://www.youtube.com/watch?v=GxUUsdBsvnA
3 https://www.youtube.com/watch?v=UPaPiBt_wTE
4 https://www.youtube.com/watch?v=RwyyzORftS0
More
The whole head structure is here https://www.flickr.com/photos/galleriejc/12521039265/
More will be found with an intensive search for "Lophius piscatorius hyoid apparatus"

nightfly's picture

Thanks for the links Derek,

Thanks for the links Derek,

I am having streaming issues and I have only got to watch the first one so far. I must try your 'head structure' link now. I am currently trying to prepare a head by first letting the flesh decay. To get a good look at the structure. It will take a bit of luck to get it at the right point before everything disintegrates, the smell is unearthly. Its out the back in a box.

Derek I just viewed the skull in your link. It is brilliant. I don't think mine will turn out so good. You can see the collapsible structure clearly. That entire head structure is designed to fall flat backwards. Its almost like a pack of cards. It is a very elastic construction. Thanks for sharing, that image shows the nature of this construction so well.

Have you any advice on fish skull preparation? I have some decaying heads at the moment and I would love to get a result somewhere near to the skull in the link.

Cathal.

nightfly's picture

Hi Derek, I watched the 2nd

Hi Derek,

I watched the 2nd video. Its brilliant. Going by the size of the scales coming off that fish it could well be a pilchard. I realise this is in NH but it might well be Sardina pilchardus, the scales are huge.

The most common food item in the anglerfish I tailed last weekend were herring. Some of them were a lot larger in relation to the anglerfish than that 'pilchard' was to its engulfer. I'm not surprised that fish had a swallowing issue. All the herring I found inside the angler were folded over in a U shape for them to be accommodated within the very circular shaped stomach. I did not post any of these as the herrings were all semi-digested and were really stinking.

As you know I did post an anglerfish/plaice interaction, the plaice was 7.5 inched long an it had to be doubled over, just as the herrings were, inside the 13" angler in which it was found. I suspect that bit of swallowing work in the video might have been something to do with getting the prey item comfortably accommodated inside the stomach. I have no doubt that that fish could deal with considerably larger prey after what I took from anglerfish stomachs last weekend.

Anglerfish with plaice folded over within (I know you've already seen it Derek but it compliments the 2nd video link above regarding the swallowing issue )----

http://www.ispotnature.org/node/646298?nav=latest

Cathal.