Are they Pest?

[the_cat_keeper]

I was diving in Anilao, Philippines a few weeks ago. I noticed this tiny (about 1 - 2mm) bright orange-ish creature crawling over a coral... A while later, I realised that there were legions of them all over the reef. I also saw them later on at Ligpo island. Are they pest?

 

[LeslieH]

The enlarged version of your image wouldn't download so I can't see the animals clearly. Still, I'm pretty sure they're small isopod crustaceans called Santia or something similar. These critters are very neat -- the orange covering is actually cyanobacteria which grows on their bodies. The bacteria taste bad so any fish that tries to eat one of these isopods will rapidly spit it back out. That's why they're one of the few species of isopods which are out crawling around where predators can see them.

 

[the_cat_keeper]

Mmm... so it is bacteria? Are they useful to the reef? I can't see the thumbnail nor open the copy that I had uploaded in this post. Anyway I uploaded another photo onto my photo gallery:

http://www.scubaboard.com/gallery/showphoto.php/photo/55892/cat/1808

 

[archman]

Leslie, you don't happen to know the genus of cyanobacteria on those things, would you? I've never heard of this before, and would like to know oodles more.

Oodles I say.

 

[LeslieH]

Oodles, you say? Odds bodkins, Archman, oodles you can have by reading the article.....

I first learned about this because I photographed a similar Santia cloaked in cyanobacteria from the BVI (http://www.nhm.org/guana/bvi-invt/bvi-surv/images/pera-i04/h0705ax.htm) & was contacted by Niels Lindquist who was studying Indo-Pacific species. His paper came out last year & is available on the web: Lindquist, N., Barber, P.H., Weisz, J.B. Episymbiotic microbes as food and defense for marine isopods: unique symbioses in a hostile environment. Proc. Royal Society B: 272: 1209-1216.
https://darchive.mblwhoilibrary.org/bitstream/1912/246/1/Lindquist+Episymbiotic.pdf

Enjoy!

Cat Keeper -- thanks for posting your other photo. Your animals are indeed Santia. These are very common throughout the Indo-Philippines based on all the images I've seen on the web. Isopods are certainly useful on reefs as cleaners, scavengers, & food for others. Carrying around the cyanobacteria (which are really algae) provides the Santia with protection & food as the isopods will eat it. Isopods are brooders - they keep their eggs attached to their bodies until the young hatch. some of the images I've found show the juveniles on the adults' backs. Lindquist et al believe this is how the young ones transfer cyanobacteria to their own bodies.

 

[Rick Murchison]

The wonders just never cease...
I love it!
Rick

 

[archman]

Thanks for the article link.

I have a picture of a Bathynomus isopod taken by an ROV on our upper continental slope. What's odd is that the exoskeleton has this light orange sheen on it. I'm now wondering if it had some funky bacterial coating on it.

 

[the_cat_keeper]

Leslie,

Thank you so much! The reef never cease to amaze/ captivate me... every so many dives I seem to find something new to awe!

Cat.

 

[Doc]

I saw them in the Philippines (and other places) as well. They are like little moving specks of orange pepper.

They photo-flouresce under black light.

 

[the_cat_keeper]

They photo-flouresce under black light.

Just curious , Why would you dive with a black light?