Slug/critter ID

[Spiffyguy]

I have noticed a group of critters on my glass. They came with a shipment of TBS rock from Florida. To me they look like a Nudi but I am thinking they are not. I don't have a decent picture yet but I am working on it.

They are white and flat. they have a raised center that looks like a nudi but they are not very long spine like. The weird thing is they have some thin tentacles/whip that come in and out off the creatures back. It is a single strand with small strands coming off of it. They appear to be filter feeding. they extend and retract on a regular basis. I have bunches of them of varying sizes. I am not sure what they are but they are very neat.


Any ideas?

 

[LeslieH]

Sounds like a benthic ctenophore. Basically they're bottom dwelling versions of the typical open-water ctenophores. All of them feed by using the two retractable tentacles you mentioned. the tentacles are coated with sticky cells that catch small crustaceans, other jellies, etc., and bring them back to the mouth. Unlike their cousins the cnidarians (corals, jellies, hydroids, anemones) ctenophores don't have stinging cells which is why they're in a different phylum. You'll find a couple of posts about them here on RC and more on other sites (plus pics) with a google search.

 

[Spiffyguy]

that looks to be what they are? Is there any concerns about having these creatures? I do dose phyto so they should have something to eat. Right now my concern is over population. There are quite a few of them. I don't find them unsightly. They are rather interesting.

 

[LeslieH]

From the past posts I see that some people like them & think they're harmless while others feel they may shade & irritate corals. Depends on what you prefer so it's up to you whether to keep them or not.

 

[billsreef]

I've found them to be interesting and harmless in moderate quantities. Large quantities can be problematic due to food competition, but I've never really seen them cause any actual problems other than get people worked up