SERIES: Invertebrate of the Week

Invertebrate of the Week #15 – Gorgonocephalus Basket Stars

Gorgonocephalus. Image: Alexander Semenov
Gorgonocephalus. Image: Alexander Semenov

The stars of the show this week are Gorgonocephalus basket stars. Members of the Class Ophiurodea, these bizarre deep-sea echinoderms are members of the same evolutionary group that brought us all those brittle stars with the five long, slender arms that we know and love.

Ophiuroid evolution, however, took a turn when it came to the Gorgonocephalus group and produced an absolutely otherwordly morphology.  Rather than bearing whip-like arms, Gorgonocephalus sport a set of five arms that progressively bifurcate; creating the appearance of a tangled mass of wriggling worms.

Gorgonocephalus off the coast of Alaska. Image: John Rix

Given their appearance, these animals are aptly named. The term Gorgonocephalus derives from “gorgos” and “-cephalus“, Greek for “Gorgon’s head”. Not ringing any bells? The monster Medusa was a particularly infamous Gorgon that you may have heard of.

That tangled mass of arms provides a clue as to this animal groups’ preferred method of feeding. First, a hungry Gorgonocephalus will typically mount a nearby rocky outcrop or another suitable pedestal. It then extends its mass of arms into the current. Its net of bifurcating arms subsequently captures small crustaceans and other tiny prey in the water column through a form of filter-feeding.

Gorgonocephalus. Image: Alexander Semenov
Detail of Gorgonocephalus arms. Image:John Rix

Prey items that get too close are ensnared by layers of both macroscopic and microscopic hooks on the surface of the Gorgonocephalus arms. You can watch a video of that feeding process, complete with menacing mouthparts, courtesy of the Seattle Aquarium below.

Gorgonocephalus spine morphology. Image: Rosenberg et al., 2005
Gorgonocephalus feeding

In terms of habitat, a study conducted by Rosenbert et. al in 2005 demonstrated that the basket star Gorgonocephalus caputmedusae has specific habitat requirements. Utilizing a Phantom S4 ROV, the team observed that Gorgonocephalus caputmedusae is restricted to deep waters between 85 and 120 meters with “rather uniform annual temperatures (4–8 C) and salinities and probably rather constant bottom currents.

Rosenberg and the research team also noted a strong association between Gorgonocephalus caputmedusae and various deepwater corals (Lophelia sp. and Paramuricea sp.)

Paramuricea coral attached to the hull of a shipwreck. Image: Peter Etnoyer/NOAA.
Lophelia coral in the Gulf of Mexico. Image: NOAA

The Rosenberg article is fantastic and I highly recommend it if you’re craving a solid introduction to the biology of G. caputmedusae.

Further Reading

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