Saltcorner
By Bob Goemans
By Bob Goemans
Hi Bob,
I was wondering if you have any experience with this. In my 240 gallon reef tank I have a good number of small brown tube worms that live in clusters. I read somewhere that they may be one of the life stages of a jellyfish. The reason I ask is that this morning I found about a dozen small jellyfish in my tank. They are about 1/4" diameter, do not appear to have tentacles, and swim in a typical jellyfish pulsing manner.
My fish do not bother them, however, they do take a look at them, but then swim away. Unfortunately, the current blows around these little guys rather rapidly. When they reach a calm area of the tank (albeit momentarily) they rise to the top and after a moment begin to color up in a brown/pink color that seems to indicate the presence of zooxanthellae. I know they will not survive very long in this tank. Even if they escape my more actively feeding corals (Frogspawn, yellow and button polyps, Rhodactis mushrooms) they will be destroyed by the man made predators in the tank (impellers).
Do you have any information about them? Are they a reason for concern? And, of course, since the rock is at least 4 years old (some older) in the tank, why would they go to this life cycle stage now? Are they a potential problem for my desirable life forms - fish, corals?
Any information would be appreciated.
Thanks,
Charlie Greiner
Hi Charlie,
Thanks for a very interesting letter, and no I've not had any experience with this species, however, do have some insight as to their origin and classification. They are not tubeworms, as they are actually the polyp stage of a jellyfish, probably Nausithoe punctata. They appear tube-like with numerous tentacles surrounding the opening of the tube. They can encrust large areas, especially where light is strong as they do have zooxanthellae and either use that or capture planktonic organisms for nutrition. They are almost feather duster-like in appearance. The medusa larvae forms on top of the tube-like polyp and are stacked like coins, i.e., one on top of another and are released one at a time. And they can for years remain in the polyp stage, then some biological event triggers them and produce what you are now seeing. Adding a moon light, changing the intensity of the lamps, change in salinity or temperature, change photoperiod, adding a different type of suspension type foodstuff, are some of the possible reasons that may cause this change to the existing status.
In fact, a photo of this species polyp stage appears in Vincent Hargreaves book "The Complete Book of the Marine Aquarium" on page 197. I contacted Vincent and asked his help in identifying this organism. He was most helpful and supplied the following:
"Nausithoe species belong to the 'Crown Jellyfish' group (Order Coronatae) and the free-swimming medusae usually have a diameter of 2 to 25 cm. The name refers to the umbrella form of the individual medusa that gives the impression of a crown. Underneath the crown there is a circle of thick feet (Pedalia). Almost all of these feet possess a single tentacle. Most specimens are imported from the Indo-Pacific on live rock or invertebrate colonies such as corals, zoanthids and corallimorpharians. Generally, in this polyp stage, they look like colonial hydroids. Many species live in deep and colder water. They are extremely attractive, often with striking colors and sometimes luminescence (bioluminescence). The few species that inhabit tropical reef shallows are from the genus Nausithoe whose medusae seldom reach a diameter of more than 2 to 3 cm. In an aquarium, the polyp stage is easily visible as a brownish colony of swaying tentacles, the medusae are not frequently seen. Zooxanthellae is usually present in the medusa stage, but this is not so readily apparent in the polyp stage. The polyps can reproduce asexually and the ephyra-larvae of the polyps are stacked like coins, one on top of the other throughout the height of the polyp column. These are released one after the other by strobilation to form free-swimming medusae."
I doubt the free-swimming medusae will remain a viable organism in a closed system. And, they probably will end up being sucked into a pump or simply flowing over the edge of a surface drain and be killed. If you notice them going to waste, it may be better to net them out so water quality is not affected. Otherwise, they would not harm anything in your aquarium.
Cheers,
Bob
