Are these parasites?

[Ruthie Kansas]

I haven't added fish to my aquarium yet. I recently added a clean-up crew and I noticed some strange things on some of the snail shells. Should I be concerned and is there something I should do about them before I add fish?

Here are the pictures. The last one isn't on a snail, but I was also curious about it. Thanks for your help.

http://reefcentral.com/gallery/data/500/6282805.JPG

http://reefcentral.com/gallery/data/500/6282804.JPG

http://reefcentral.com/gallery/data/500/6282803.JPG

http://reefcentral.com/gallery/data/500/6282802.JPG

http://reefcentral.com/gallery/data/500/6282801.JPG

[rshimek]

Hi Ruthie,

The brown things on the snail shells are other snails' shells... :D These are the shells of a type of "worm" snail or vermetid gastropod. You can read a bit about them in this article (http://www.aquarium.net/0897/0897_8.shtml) I wrote several years ago.

In the bottom image, you show another snail, this time one where the adult is without a shell. This particular type of slug is called a sacoglossan, and it is probably in the genus Thuridilla. These slugs are generally thought to be herbivorous. You might wish to investigate the various species in that genus at the Sea Slug Forum. (http://www.seaslugforum.net).

[adrinal]

The link didn't work :(

[rshimek]

Hi,

Nope, not any more. The page is gone and as far as I know there are no cached copies.

Here is some information about these animals.

Classification: Mollusca; Gastropoda; Prosobranchia
Common name: Worm Snails
Common species:
Dendropoma species; Serpulorbis species; Spiroglyphus angulatus.

Worm snails, or as they are known scientifically, vermetid gastropods are another of the many strange organisms found amongst the snails. They are recognized by their hard calcareous tubes which look rather like small feather-duster tubes. However, instead of a crown of tentacles, only strands of mucus are ever seen coming from the tubes. Some have a small round brown cap that plugs the end of the tube when they retract into it.

These are animals that for about an hour or less of their lives, look and act like good little snails. They have a coiled shell and are quite mobile. As larvae they are brooded inside the shell of their female parent. They live there and go through embryonic development all within their parent's tube. When they become mature enough, they leave the parent's tube and strike out on their own, for a few minutes at least. They crawl a short distance and choose a place of their liking and cement their shell to it. From this point on they are immobile.

They live as suspension-feeders. They exude strands of mucus from the aperture of their tube into the water surrounding it. Particulate material adheres to the strand, and short time later the animal reels it in. A colleague of mine once referred to this as the "fly-fishing mode" of suspension-feeding, but actually instead fishing for flies, it is catching small particulate material.

Once fastened to the rock these animals don't look at all like snails. The shells become sort of loosely coiled and look, at best, like a pile of tooth paste squeezed from the tube or a piece of loosely coiled calcareous spaghetti. Generally, the final part of the shell extends upward some distance off the substratum.

Although several species are found occasionally in our systems, generally entering on live rock, one variety in particular may become very abundant, and be a serious nuisance in some systems. Interestingly, we don't really know the name of this species for sure. It probably is Spiroglyphus angulatus, which is a small vermetid originally from the Caribbean. However, there are similar small species from elsewhere in the world, and they all look pretty much alike. It will probably take genetic testing to verify the identity of our aquarium friends.

Whatever species it is, this particular one has small individuals. The tube seldom is over one or two millimeters wide. The shell is typically reddish or reddish brown, some even are tinged with violet. The animal forms a small calcareous shell mound and then sends up a short, three to five millimeter long, vertical stalk. The upper edge of this tube may be razor sharp, and may inflict rather nasty cuts. A few of these would be no real problem; however, this animal reproduces very well in marine aquaria. Left unchecked, they can reach populations of over several thousand in a few months. They prefer high current areas, and will infest and clog plumbing significantly reducing water flow. In severe infestations they can clog and shut down pumps. The only situation in cases like these is physical removal of the animals using whatever method is easiest (a muriatic acid bath works well).

Fortunately, some fishes such as Copperbanded butterfly fishes, seem to eat them, and some hermit crabs will eat them as well. Eating these worm snails may well be the only truly beneficial use of hermit crabs in aquaria.

The larger vermetids, in the genera Dendropoma and Serpulorbis do not seem to reproduce well in our systems and never obtain the plague proportions of their smaller cousins. The larger species tend to enter our systems on live rock or in coral, and are more interesting curiosities than any kind of pest.

[adrinal]

Thanks for the paste. :)