The stars of the show this week are the wonderfully weird 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. But Ophiuroid evolution 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.
Given their appearance, you quickly understand that 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. But I digress…
That tangled mass of arms provides a clue as to this animal groups’ preferred method of feeding. A hungry Gorgonocephalus will typically mount a nearby rocky outcrop, or other suitable pedestal, and extends its mass of arms into the current. It then utilizes its collection of bifurcating arms to capture passing small crustaceans and other tiny prey through a form of filter feeding.
Prey items that get too close are ensnared by layers of both macroscopic and microscopic hooks on the surface of the Gorgonocephalus appendages which trap the unfortunate animals long enough for the Gorgonocephalus to ferry them to its rather ominous-looking mouth. You can watch a video of that feeding process, complete with menacing mouthparts, courtesy of the Seattle Aquarium below.
In terms of habitat, a study conducted by Rosenbert et. al in 2005 (PDF available) demonstrated that at least the basket star G. caputmedusae appeared to have specific habitat requirements. Utilizing a Phantom S4 ROV, the team observed that G. caputmedusae inhabited 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 G. caputmedusae and various deepwater corals (Lophelia sp. and Paramuricea sp.)
The Rosenberg article is fantastic and I highly recommend it if you’d like to have a solid introduction to the biology of G. caputmedusae.
- Gorgonocephalus photo essay – Echinoblog
- Are Basket Stars Sea Stars? – Seattle Aquarium
- Barboza, C. A., Mendes, F. M., Dalben, A., & Tommasi, L. R. (2010). Echinodermata, Ophiuroidea, Gorgonocephalus Leach, 1815: First report of the genus for the Brazilian continental margin. Check List, 6(2). PDF Available
- Herrero-Pérezrul, M. A., Granja-Fernández, R., Hoyos-Padilla, M., & Reyes-Bonilla, H. (2014). New record of the basket star Gorgonocephalus eucnemis (Ophiuroidea: Gorgonocephalidae) at the Pacific coast of Mexico. Marine Biodiversity Records, 7, e33. PDF Available
- Rosenberg, R., Dupont, S., Lundälv, T., Sköld, H. N., Norkko, A., Roth, J., … & Thorndyke, M. (2005). Biology of the basket star Gorgonocephalus caputmedusae (L.). Marine Biology, 148(1), 43-50. PDF Available