Loligo (Alloteuthis) subulata

DWhatley

Cthulhu
Staff member
Moderator
#2
How many hearts do squid have?

The dark spot in one of the pictures reminded me of the way two of the hearts look on the Mercatoris. It occurred to me that I did not know if other cephs share the multiple heart or the circular brain biology. I am assuming not but thought to ask.
 

monty

Colossal Squid
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#3
dwhatley;117388 said:
The dark spot in one of the pictures reminded me of the way two of the hearts look on the Mercatoris. It occurred to me that I did not know if other cephs share the multiple heart or the circular brain biology. I am assuming not but thought to ask.
All cephs, including Nautilus have the donut-brain, although there are some variations... in particular, Nautilus lacks the vertical lobe that's been shown to be important in memory formation in other cephs, yet (as Robyn has shown!) they are quite capable of learning, so they probably have a similar brain area that hasn't been identified. Anyway, the gross neuroanatomy is pretty consistent across coleoids and Nautilus is surprisingly similar, considering how long ago the lineages split. The brain is more like a "nerve cord" with the individual lobes less distinct than most other cephs, and of course, there are no chromatophore lobes, since it has no chromatophores. The optic lobes are grossly similar to those of coleoids (in both, they stick out from the sides, and aren't part of the "donut" brain.) There's some difference, though, in that the image on the optic lobes isn't "flipped upside down" like it is in coleoids (except Vampyroteuthis) and the optic lobe's detailed anatomy is a bit different as well. They make up for some of this by having more sophisticated olfactory organs and lobes, though: Young reports from a discussion with Saunders that Nautilus lives by "smelling and groping" rather than "visual spotting and attacking" like most coleoids. (Although, frankly, many octopuses seem as happy with tactile hunting as visual.)

I'm less sure about the hearts, but I have books to substitute for my ignorance :read:... all cephs including Nautilus have 3 hearts, one central "systemic" heart and 2 "branchial" hearts for the gills. However, one of the main relics(?) that makes Nautilus different from all the coleoids is that Nautilus has 4 gills rather than the two found in all other cephs. I put the (?) for relics, though, because there are some strangenesses: the gills develop sequentially in the embryo, which makes one wonder if the 4 gills is a recent adaptation in Nautilus rather than the primitive condition... we don't have any other ancient or modern nautiloids or ammonoids to compare it to.
 

DWhatley

Cthulhu
Staff member
Moderator
#4
Thanks Monty. I was not sure if the hearts and brains were something that tied them together or not and I either did not ingest the info when presented or have only read enough repetition to "know" the octo configuration.
 

DWhatley

Cthulhu
Staff member
Moderator
#5
Identification of cephalopod species from the North and Baltic Seas using morphology, COI and 18S rDNA sequences
Katharina Gebhardt, Thomas Knebelsberger 2015 (subscription)
Abstract
We morphologically analyzed 79 cephalopod specimens from the North and Baltic Seas belonging to 13 separate species. Another 29 specimens showed morphological features of either Alloteuthis mediaor Alloteuthis subulata or were found to be in between. Reliable identification features to distinguish between A. media and A. subulata are currently not available. The analysis of the DNA barcoding region of the COI gene revealed intraspecific distances (uncorrected p) ranging from 0 to 2.13 % (average 0.1 %) and interspecific distances between 3.31 and 22 % (average 15.52 %). All species formed monophyletic clusters in a neighbor-joining analysis and were supported by bootstrap values of ≥99 %. All COI haplotypes belonging to the 29 Alloteuthis specimens were grouped in one cluster. Neither COI nor 18S rDNA sequences helped to distinguish between the different Alloteuthis morphotypes. For species identification purposes, we recommend the use of COI, as it showed higher bootstrap support of species clusters and less amplification and sequencing failure compared to 18S. Our data strongly support the assumption that the genusAlloteuthis is only represented by a single species, at least in the North Sea. It remained unclear whether this species is A. subulata or A. media. All COI sequences including important metadata were uploaded to the Barcode of Life Data Systems and can be used as reference library for the molecular identification of more than 50 % of the cephalopod fauna known from the North and Baltic Seas.
 

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