Squid beak variation (and stuff)

Steve O'Shea

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This rather poor scan (something in prep) is of the upper and lower beaks of Pholidoteuthis boschmai . The upper illustrations are from a female (lower beak, left; upper beak, right), and the lower illustrations from the male (lower beak, left; upper beak, right).

Pholidoteuthis is generally thought to be quite a rare squid (although some 30+ mature specimens exist in the collections - probably more than anywhere else). Two 'forms' have been referred to in the literature - long and short rostrum. In redescribing this species (in prep - some major changes to be made) we determined the 'long rostrum' form was simply the male, and the 'short rostrum' form the female.

I've included these pics, and will include pics of others shortly, to emphasise that there's a lot of variation in beak shape within a species, between sexes, and sometimes ontogenetically. In other words, identifying beaks, often partially digested, from stomach contents isn't exactly an 'exact science', and we still know very little of the biology and morphometric/anatomical variation of these deep-sea squid species.

What is REALLY interesting is that almost every beak recovered from the stomachs of these sperm whales to date has been male (long rostrum form). Bizarre!

Pholidoteuthis is one of a very few species of squid that is almost exclusively found on seamount/deep-sea reef habitat in New Zealand waters. Interesting ay what! (Are the whales eating on seamounts/reef?)

 

Steve O'Shea

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And these two figures of Lepidoteuthis grimaldii (upper block of three figures), showing ontogenetic variation in darkening of both upper and lower beaks.



The lower block is of Octopoteuthis spp. There's not much in this!! (Although you do look at a few other character states that I've not illustrated - but even then I'm pulling my hair out!)



I might add that the relationship between Lepidoteuthis and Octopoteuthis is probably a lot closer than has earlier been recognised, following our description last year of hooks in the male of Lepidoteuthis (and these two genera both have 8 arms as adults, and dermal scuplture of one sort or another).

The upper three figures are of the hook in the male of Lepidoteuthis; the lower images of a variety of considerably smaller species of Octopoteuthis. The hooks of Octopoteuthis sp. 'giant' (n.sp.) [another manuscript in prep] are quite sensational.

 

WhiteKiboko

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If there's variation in beak design, how can you be sure that a beak is from a certain species and not a close relative?
 

Steve O'Shea

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In very speciose groups, the likes of Enoploteuthidae (generally small-bodied), Histioteuthidae (small- to moderate sized), Onychoteuthidae (small to giant), Octopoteuthidae (genus Octopoteuthis) (small to giant), Mastigoteuthidae/Chiroteuthidae (small to giant), there is always going to be some doubt, unless you've got complete series of male and female beaks from actual specimens, throughout their ontogenetic range. If you do you can make some value judgement and say it's x or y.

Fortunately speciation in many of these groups/families has occurred not just in acquisition of new characters or charater states, but in size, so you get monster species and closely related pint-sized species. This is quite true of the Onychoteuthidae and some species in Mastigoteuthidae. As the whales are generally eating large-bodied squid, and within each family there aren't too many large-bodied species, attributing a beak to species often isn't challenging (famous last words...). You just look at the general darkening of the beak (an indication of maturity) and size, and by process of elimination attribute it to the appropriate species (small and dark, small-bodied species; small and not dark, juvenile of larger-bodied species; large and dark, mature large species; large and not dark .... monster species).

The problem is when small-bodied things are eaten the size of a matchbox or cigar; these beaks can be quite challenging to identify. I've a couple of very distinctive sets to attach names to, but in all honesty, attaching a genus to them should not prove too difficult.
 

Steve O'Shea

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Someone asked somewhere to see the various 'mega squid' beaks compared.

Well, from left to right: Taningia danae, Kondakovia longimana, Architeuthis dux and Mesonychoteuthis hamiltoni.

Both the Kondakovia and Architeuthis lower beaks have been taken from carcasses of squid; the Taningia and much-degraded (damaged; only partial beak) Mesonychoteuthis are both ex whale stomach content samples. I do have somewhere 'perfect' beaks of Taningia (larger than this one), but not a lot better of fully mature Mesonychoteuthis (the beaks would be considerably larger than those of Architeuthis if intact; they are considerably thicker!!).



Or, alternatively (beak type obvious from above)

 

Steve O'Shea

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Identification of beaks is further complicated by digestion of delicate wing and wall margins. Certain beak types have caused considerable confusion over the years.

Fig. 1 (in the block below) is taken from Clarke's 1980 monograph on squid beaks from whale stomachs (Discovery Report), wherein these problematic beaks are illustrated and referred to as Moroteuthis A, with a comment to the effect that the beak-type was so different from others in the genus that it should be accommodated in a separate genus altogether. Figs 2-4 are of similar beaks from one of the whales here (nice to get them in this condition); Figs 5 and 6 from the same whale, easily identified as those of Moroteuthis ingens; and Figs 7 and 8 of M. ingens beaks taken from a fresh specimen (without the margins digested away).

Interesting that these 'aged' Moroteuthis beaks are about as dark as those of Mesonychoteuthis, whereas when fresh they are anything but.



Moroteuthis ingens beaks are also demonstrably sexually dimorphic (something Kat will work on shortly), so identifying these things really can be a challenge.
 

Phil

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Steve,

All the Mesonychoteuthis beaks I have seen images of have been exceptionally dark. Why don't other large squid types appear this way, or have I simply not seen the appropriate images?

Many thanks,

Phil
 

Steve O'Shea

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It's not an easy one to address Phil. We were talking about this last week. I'm kicking myself as not once have I done a pH test in the stomach of one of these whales. I'd like to try and duplicate the darkening in the lab ... if it is simply a pH thing (it's the most obvious place to start, but it might not be the answer - it could be a bag of ammonium ions dumped in the gut after eating Mesonychoteuthis).

The aforementioned, aged Moroteuthis ingens beaks (certainly not black on any of the millions and squillions of these things I've processed fresh over the years) are dark also, so I think it has to have something to do with digestion.

The beaks on the small Mesonychoteuthis here in the office (~ 1 m ML) and the larger one of last year are not black (not that I recall). I'd love to see more of them!!
 

Phil

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Thanks for the information Steve.

For what little it is worth, the mature example on display in the BMNH's 'Darwin Centre' in London is charcoal black too. It is certainly larger than than an adult Architeuthis beak but cannot really be measured from a vantage point from behind a plate of glass! I'm sorry that I do not have an image or a reference to show you but perhaps next time I go up I'll try and snap an image.

Thanks again!
 

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