Sacoglossan Sea Slug Question

[Anemone]

Hi Dr. Ron,

I picked up a very neat Sacoglossan Sea Slug this weekend at a shop that didn't really know what it was (I wouldn't have known either, except for this forum).

My question is in regard to their diet - can these slugs eat any variety of caulerpa, or are they species-specific? They had this slug in a mixed algae tank, but the caulerpas were only feather-types. I have (I believe) C. taxifolia in a couple of my tanks. The slug has 4 camouflage appendages attached to its shell or mantle, but these appendages look more "razor-caluerpa" like (rather than feathery) - leading me to believe that this slug was originally found in a different species of caulerpa. There was no algae similar in appearance in the dealer's tank, and they said they had the slug for several weeks. I'm hoping these slugs are generalized caulerpa feeders and it can survive on my variety, as differing varieties of caulerpa have gotten a bit harder to come by in California recently :D

I'll get a picture tomorrow (I just put the slug in my 6 gallon nano at work so I can keep an eye on it), but due to dsl connectivity problems (for some reason, my DSL won't connect to RC anymore - goes everywhere else fine, just not RC :(), I probably won't be able to post the pic(s) until Wednesday.

Thanks,
Kevin

[rshimek]

Hi Kevin,

Sacoglossans, as a rule, tend to be quite specialized in their diets. There may be some latitude, but I suspect that the range of potential foods is quite narrow.

Good luck in your quest to keep it. These animals are often quite beautiful.

:D

[Anemone]

Okay, here are a few pics....I just wish I could figure out how to put more than one picture in a single post. The head of this critter is in the lower left, the smooth green area in the center is the shell, and anything else green in the picture that doesn't look like taxifolia belongs to the snail.....

Kevin

[Anemone]

Another.....

[Anemone]

And finally......

[schemo]

that nudi is cool looking!!! how much did you pay for it???
schemo

[rshimek]

Hi

Kevin,

It appears to be a species of Lobiger, albeit not the usual Lobiger souverbiei sometimes seen imported from the Caribbean. I would guess that a Caulerpa is the food source, but judging by the shape of the projections on the back, I suspect the food may be Caulerpa cupressoides or C. racemosa rather than C. taxifolia.

Schemo,

As a point of order, it is not a nudibranch :D, Sacoglossans are a different type of slug - no nudibranch is herbivorous.

[Anemone]

Originally posted by rshimek
I would guess that a Caulerpa is the food source, but judging by the shape of the projections on the back, I suspect the food may be Caulerpa cupressoides or C. racemosa rather than C. taxifolia.


That was my thought as well, as I haven't seen it eat any of the caulerpa in my tank. <sigh> Don't know if I'll be able to find any of the "correct" type to feed it.:(

Kevin

PS - Schemo - $10

[reefgal]

I thought I would add my 2 cents as well....I had a very similar animal (although it did not have a shell) growing in my refugium. It was eating the grape caulerpa. However, the population got so high that it overwhelmed the caulerpa and almost wiped it out. I went hunting for them and removed 30 adults and five egg cases. I'm keeping an eye out now and removing any I find. I'm trying to let the macro algae recover.

Just keep an eye on 'em and make sure they don't go crazy!

[Anemone]

An update. The slug seems to be doing all right. It spends most of its time on the caulerpa, but I can't tell if it is feeding or not. One thing I have noticed in the past few days is that I have a lot more "free floating" pieces of caulerpa - basically fairly long single "fronds" of caulerpa that look like they've been snipped from their runner or bottom portion of the leaf. I've read that Sacoglossan's are "juice suckers" that drink the fluids from the caulerpa, but I'm hoping that maybe these free floating pieces indicate the slug is munching (although the pieces don't look particularly withered or "juiceless").

Still keeping my fingers crossed...

Kevin

PS - I now think my slug may be Lobiger serradifalci - and the picture says it was photographed on C. Taxifolia so maybe I lucked out!!!:)

http://www.medslugs.de/E/Mediterranean/Lobiger_serradifalci_01.htm

[Anemone]

I love computers - the more I look, the better this gets. My last post noted all the cut fronds. Here is the abstract from a short paper I found at:

http://www.unice.fr/LEML/Thierry/Jmba3761.pdf


In order to control the spread of the invasive Caulerpa taxifolia (Chlorophyta) in the Mediterranean, in situ experimnets were conducted with the specialized predator Lobiger serradifalci (Mollusca: Ascoglossa=Sacoglossa). An unexpected effect of L. serradifalci on C. taxifolia was observed. Instead of destroying the algal frond, the ascoglossan cut fronds into tiny living fragments capable of regenerating. thus, L. serradifalci may facilitate C. taxifolia dispersal instead of controlling it.

Kevin

[rshimek]

Kevin,

THANK YOU, SIR!!!.

Great information. Thanks for sharing it with us. It does look like the slug is eating.

:D

[Anemone]

Well, now I have another question. I came to work this morning and found a good sized egg strand (probably 2" by 1/8"). So, my question is - would this slug lay a strand of unfertilized eggs, or can I expect these eggs to hatch? Any idea (or literature) on the life cycle of the juvenile. Any chance they'll settle out in this small chance, or are they just going to be fish food for the small damsel and yellow watchman goby?

As always, thanks!

Kevin

[rshimek]

Hi Kevin,

It is possible the eggs are fertilized. Most snails of this type can store sperm for extended periods, and copulation could have occurred prior to collection. However, they also are known to deposit unfertilized eggs.

In either case the egg mass jelly coat will dissolve in a few days, releasing the eggs. If they are not fertilized they will be food for something in the clean-up crew. If they are fertilized, the larvae will go into the plankton.

Sacoglossan larvae feed on phytoplankton, and many of them have an extended planktonic period (several weeks to a couple of months), but I don't know specifically about yours.

I suspect they will become fish or somebody else's food, however, there is always the chance a few of them will make it through the period and show up as tiny slugs in a couple of months.

Generally as well, when sacoglossans start to spawn, their days are numbered; I would expect the adult to live only a few more weeks but, of course, I may be wrong.

:D

[Anemone]

Originally posted by rshimek
Generally as well, when sacoglossans start to spawn, their days are numbered; I would expect the adult to live only a few more weeks but, of course, I may be wrong.

Aw, darn!

Kevin

[Anemone]

You were right:( . The sacoglossan died last night. It really did a number on the taxifolia in the tank, and was eating up until the end (or at least as of Friday, a few days ago). Too bad, it was a very cool critter.

Kevin

[rshimek]

Hi Kevin,

Shucks! :(

Sorry to hear of its demise, they are beatiful and interesting animals.

It probably lived out a relatively normal life span, however, they do tend to be somewhat "transitory" in nature.

[thanks] for sharing the images and information.

[ranaman]

You might be surprised. I got a few Oxynoe antillinarum from an LFS. Now the tank is crawling with different size ones and almost all the caulerpa is gone.