Squid beak sizes


May 4, 2019

I hope I'm writing in the correct forum. This one seems to fit best to my question - sorry if not!

I would like to ask if there are any publications on the maximum beak sizes of Architeuthis and Dosidicus?

I could only find the maximum size for Mesonychoteuthis with a LRL of 48-49 mm (depending on the source), but nothing for the other ones.

Are there any other species with a similar size and verified data? Onykia? Others?

Best regards,
There's a tremendous amount of information published on Dosidicus, wherein data on their beaks are provided (LRL [rostral length of the lower beak], and regression equations in predator/prey studies) if you use "Dosidicus gigas LRL" as keywords in a Google search.

Whether anyone has actually specified the 'maximum' LRL of beaks of D. gigas is another matter altogether, but you would at least be able to extract a maximum LRL from each paper, and then when you have reviewed as many papers as you can, generate a maximum value for yourself. The same applies to those beaks of Architeuthis.

As I am not sure how much you know about these things (if you are a beginner to ceph taxonomy, predator/prey studies, or squid beaks), I'm just warning you that the maximum LRL value of Architeuthis and Dosidicus will be considerably less than that for Mesonychoteuthis because the beaks are very different shapes. LRL is only half of the story; by itself you cannot use it to rank squid size. You also need regression equations that relate LRL to ML (mantle length), TL (total length) and weight of the squid, to make sense of the number (it is quite possible for a squid to have a small LRL value and another species to have a large LRL value, but for the former species to be very much longer and heavier than the latter).

When compiling your information (regarding max values for LRL for a species), make sure you look at predator/prey studies, fisheries studies, and taxonomic descriptions. Taxonomic descriptions seldom dwell on beak morphology (taxonomists as a rule don't like beaks), predator/prey studies (such as those dealing with shark or toothed whale/dolphin diets) oftentimes report very large beaks (larger than reported in taxonomic works, or those from fisheries surveys), and fisheries studies report many beaks (with excellent regression equations).

You must be careful in your review, because someone may have specified a 'maximum LRL' in 1960, 1980, or 2012 (for instance), but additional collections or larger specimens may have been reported since. Just because someone says 'maximum' doesn't mean that this is the largest they get, so don't stop your literature search until you've exhausted everything through to 2019 (to be sure you've captured the full reported variation for any taxon).

I hope that in some way helps. You'll need to do a bit of research yourself. It is, however, a rewarding exercise.

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