With all of the vicious ophiuroid feeding going on, I am recently reminded by a neat paper written by James Morin at UCLA from the 1988 International Echinoderms Conference. about Ophiarachna incrassata, what he describes as "crepuscular and nocturnal predator "...
His paper describes an AWESOME feeding method!! Something that he calls "The Body Spiral Behavior"...and you KNOW its good when its
- Sounds like wrestling!!
At night (this behavior was only observed using night-vision), this species will sit up on its armtips and form a "pseudocrevice" , maintaining the top position for many minutes without moving. Apparently, he found many individuals found in this posture during the night.
From here, it gets interesting.
Short version: Fish get too close..and then... Ophiarchna will RAPIDLY wrap its body into aspiral (as above) ..forming the "body spiral". This action apparently takes less than a SECOND.
The fish is trapped by the elongate spines on the arms creating "bars" to a "prison" formed by the helically arranged arms.
The brittle star holds the position for several minutes, gradually lowering the disk toward the bottom and moves its arms outward.
Prey captured was digested head first as it was swallowed WHOLE by the ophiuroid.
Interestingly, Ophiarachna takes advantage of several of these fish's natural nocturnal behavior to find hiding spaces. And although they feed on a variety of items (e.g., algae, etc.) this behavior was observed to be quite successful.