Scientific Illustration

factstofigures:

Contributing Artists: Simon Chew, Daniel Cole, Nigel Gerke, R. Gibson, Toni Hargreaves, P. J. Hayward, Phyllis Knight-Jones, Paul J. Llewellyn, P. J. A. Pugh, J. S. Ryland, and Nathalie Yonow.

Hayward, P. J. and Ryland, J. S. (Eds.) (1995). Handbook of the Marine Fauna of North-West Europe. New York: Oxford University Press Inc.

biomedicalephemera:

Limbs of the Cephalopoda

Whether squids, octopuses, and nautilus have “arms” or “tentacles” is often simply a matter of semantics, but the most accepted definitions (from what I’ve found) tend to define the “arm” as a tapered limb, with two rows of suckers along its entire length. “Tentacle” is typically a length of tapered limb with no suckers, leading to a distal club-like appendage, covered in suckers.

One exception would be limbs in the nautilus - they have up to 90 un-suckered limbs, but their limbs are called “tentacles” by those who study them, even without the terminal club.

Images:
Top right: Octopus vulgaris and detail of beak and arms
Top left: Detail of tenticular clubs in squid, from the Expedition of the Valdivia
Bottom right: Arm of Illex illecebrosis (Northern Shortfin Squid)
Bottom left: Tentacle of Illex illecebrosis

biomedicalephemera:

Japetella diaphana tentacles and buccal cavity

Japatella diaphana is an octopus member of the Bolitaenidae family, and like the other members of its family, is very small - 12 cm long at most. They live, eat, and breed in the pelagic zone of the ocean, unlike deep-sea squid, which rarely spend their entire lives at such depths. 

Mature females have a bioluminescent photophore encircling their beak.

Die Cephalopoden. Ewald Rubasmen, 1910.

biomedicalephemera:

Fun fact: If you Google “loligo japonica”, all but one site on the first page is trying to sell you frozen squid.

Cephalopoda

1. Loligo ellipsura - [nomen dubium - junior syn. of Loligo gahi] Patagonian Squid  

2. Loligo japonicum - Japanese Squid

The Voyage of the HMS Challenger: Report on Cephalopoda Specimens. 1854.