The Glowworm Nautilus and her Passengers

As promised, here's a more detailed discussion of some of the critters we caught on our way to Opitz Station

GLOWWORM NAUTILUS

(Velabrachius lucifer)

The female of this species possesses two extra-long arms with sail-like flaps called vela (the name is singular and plural), which she clamps along the sides of her loosely- coiled shell to form a chamber. Eggs are deposited into this chamber, and the larvae remain within until they are large enough to survive on their own. Males are similar in size, though they do not possess the long arms nor the vela.

Both male female V. lucifer possess bioluminescent organs, called photophores, along their arms. Glowworm Nautili can "wink" their lights on and off, producing flashing patterns, probably as a form of communication.

For more details, see: Irvine, Gene The Luminous Sea: A Bioluminescent Nautiloid from the Middle Devonian (2011) Journal of Cephalopod Studies 134:45 pgs. 345-362

PASSENGERS

In addition to young V. lucifer (b), several other organisms frequently take up residence in the Nautilus' brood chamber. Copepods (A.), Ostracods (E.) and pelagic trilobites (D.) are abundant, as are planktonic crustacean larvae such as this crab zoea (C.). The identity of (F.) remained a mystery for quite some time. Clearly it was some sort of larvae, but we couldn't identify the adult form until Dr. Alonso successfully managed to raise a few to adulthood in his lab tanks. It turns out this spiny critter is actually the young of the anomalocarid Schinderhannes bartelsi! I'll have a lot more on Schinderhannes in a later post.

ECHIDNA SHRIMP

(Echinodorsus gladiocaudus)

In addition to Glowworm Nautili, we also find an abundance of this prickly-backed shrimp in the Glowing Sea. Despite its name, the Echidna Shrimp is actually a phyllocarid (a primitive group believed to be ancestral to crabs, lobsters and true shrimp). While most phyllocarids are bottom-dwellers, E. gladiocaudus is entirely pelagic.

Echidna shrimp are frequently preyed upon by Glowworm Nautili. Though the shrimp's prickly carapace protects it from most predators, the V. lucifer gets around this difficulty by grasping the shrimp's tail and stripping off the shell with its tentacles before consuming the hapless prey.