Mystery Bug: Gammaridean Amphipod and Disappearing Zoanthids - 7/19/09
Hi,
<Hi y'all, Lynn here today.>
We're wondering if you can help identify the mystery bug in the enclosed photos.
<Yep, it's a harmless Gammaridean amphipod, also known as a scud or Gammarid.>
We have a 30 gallon salt water tank that is about a year old. We've been having some problems with our Zoas (they're disappearing a little at a time as if being eaten) and took them out for a Lugol's dip. This guy was one of the unfortunate victims that came out. Is this a type of copepod?
<Nope. While they're both crustaceans, Gammarids are in the order Amphipoda while Copepods are in the order Copepoda. For more information on Gammarids, please see the following link: http://bb.wetwebmedia.com/viewtopic.php?f=25&t=125&p=2869&hilit=gammaridean#p2869 >
Is he anything that would eat a Zoa?
<I doubt that he'd eat a healthy Zoanthid, but he could potentially eat dying tissue left by a predator. Gammarids can and do however, sometimes act as Zoanthid 'irritators' due to their grazing and foraging habits. Some Zoanthids simply don't like all that contact and react by keeping their polyps closed for extended periods of time. If your Zoanthids are opening as usual, but simply disappearing, I'd look for the usual suspects: Heliacus/sundial snails, Aeolid Nudibranchs, hydroids, etc. Please see the following links for photos and more information:
http://www.zoaid.com/gallery2/main.php?g2_itemId=384
http://www.zoaid.com/index.php?name=FAQ&id_cat=3#q15
http://www.wetwebmedia.com/zoanthidcompfaqs.htm
I'd also recommend checking the remaining Zoanthids for any sign of small light/whitish spots. If so, it could be what some hobbyists call Zoanthid pox. Please see this link for a photo example: http://www.zoaid.com/gallery2/main.php?g2_view=core.DownloadItem&g2_itemId=3573
For treatment, see the first FAQ, titled 'Zoa Pox Treatment -- 05/09/09' at this link: http://www.wetwebmedia.com/furancpdfaqs.htm
More info here regarding diagnosis/treatment: http://www.wetwebmedia.com/zoanthidhlthfaqs.htm >
Thanks for the help,
<You're very welcome and good luck!>
Pegine and William
<Take care, LynnZ>