Larvae dropping like flies

[benjamin]

Well for the first month everything was going well, but over the last month and a half I have encountered almost every problem: floaters, cannibalism, foul water, and food fussies. Now that I've solved all these problems the larvae still find a way to die

. It's very frustrating to go to great lengths to save something, and then have it just die on you. Now it seems as though the last few casualties have just lost the will to live. They somewhat gradually become senseless and immobile (over about a day), and then are pounced upon and torn to shreds by planarians (usually they're still twitching when this happens but by the time it does there's no hope for the larvae anyway, so I don't think the planarians are at fault). Could some one please help me?

 

[edward]

Ben it would help if you listed the species involved, the diet, temp, pH, ammonia, nitrite and nitrate levels of the tank.

Ed

 

[alan]

If you have a large population of planarians, this suggests that the tank is not nearly clean enough to raise larvae well. Much more cleaning - daily small water changes with vacuming of the bottom, don't overfeed.
You could even consider moving the larvae into clean containers regularly, e.g. every 4-7 days.

 

[jennifer]

I've been thinking about writing an article, or subsection, called "why larvae die". I would summarize it as:
1. lack of live food
2. water quality issues
3. mass infection
4. stress
Anyone have any other categories to suggest?

I don't know if any of these apply, Ben. I'd be happy to go into more detail as needed. I agree that the planaria are probably not at fault.

(Message edited by jennewt on March 14, 2005)

 

[benjamin]

The species is Cynops orientalis. There is certainly no lack of food, they were moved recently so stress could be a slight factor and all the water is relatively new and clean. The temp is about 17-20º c. I give them both daphnia and blood worms but I find that larvae tend to specialize into either blood worms or daphnia and very rarely eat both. Ph is at 7 so I don't see anything wrong there. I do not have a large population of planarians about 0-4 per tupperware container, but they are large 8-15mm and eat quickly. I'm beginning to think infection could be the cause, one other wise healthy newtlet just shed its tail, it still eats normally though.

 

[joseph]

Jenn: That would be a great article!

Might also want to add something about weak larvae etc.

I'd remove the planarians(extra bioload if for any other reason) and keep up the water changes.

 

[pin-pin]

Jenni,

I can think of disaster

subsections including:

oxygen (under air quality)
crowding/canabalism
parasites

It will be great to have another comprehensive FAQ though!

 

[jennifer]

Ben - It is unclear from your description how you are housing them. If they are in Tupperware, how did the planaria get in there? As Alan suggests, maybe the containers should be cleaner.

I believe there are 2 basic housing methods that work for raising larvae (at least for me). One, a well-cycled well-planted tank with the larvae kept at low density. Two, simple containers with bare bottom, with 100% of the water changed every couple of days, and the container itself replaced or wiped out inside when the water is changed. On the occasions that I have tried forms of housing that were intermediate between these two types of housing, disaster has often ensued.

If you suspect infection, try antibiotics and fresh clean containers. I actually had dramatically good results in arresting an episode of larval die-off using a broad-spectrum antibiotic for fish (kanamycin + nitrofurazone).

Joseph and Pin-pin - thanks for the suggestions!

 

[edward]

I have the best results with bare bottomed enclosures with at least 50% water changes every couple of days and I do not disturb the biofilm.

Ed

 

[benjamin]

I keep them in bare bottomed tupperware containers. The planarians came with the eggs, they were on the plants the eggs were on. I suppose I do have an intermediate setup: individual-small groups in a tupper ware container with a few plants. All the dead larvae have one thing in common, very reduced gills. Here's a picture of one of the dead amazingly well preserved.

Though you can't see much detail in this picture (macro on the camera isn't so great) you can see the position it's in. I was wondering if this position along with gill shrinking could be a symptom of anything in particular.

 

[corrina]

I have two bare bottom containers used for my larvae and up until recently had been dealing with the same situation. They were not overcrowded. To prevent problems with things coming in with plants, I use silk plants and a clean sea sponge for hiding areas. Right now I have 6 larger larvae (some appearing to be leucistic) and 7 smaller larvea in the smaller container. The dead ones, as far as I can see, have had some abnormalities such as very small gills, or odd shapes. They can't all survive, as much as we try our best, so I try not to take it personally, but I usually always do.

 

[jennifer]

I don't have any scientific evidence to back this up, but I suspect that the short-term biofilm that develops inside a larva-rearing tub is very different from the long-term biofilm that is found in an established cycled tank. Because of the high density of food in a larva rearing tub, it seems logical to me that the short-term film would be more likely to harbor mold or undesirable bacteria. I believe that I have better success when I keep the containers clean; it may be pure superstition, but I'll probably keep doing it anyway.

Ben and Corrina - I don't know of any information one can get from the specific abnormalities seen near death. When I had a clear case of bacterial infection (which I know only because antibiotics stopped the die-off abruptly), the larvae just before death had their tail tips bent and the gills pointed forward and redder than usual.

 

[justin]

One method I've experimented with, as far as water quality is concerned and young larvae, is using plastic tubs with submersible filters (bottom intake).

I bury the lower portion of the filter with 'pea-sized' gravel...about 1.5"-2" deep and surround the smaller pebbles with stones about 2" in circumference to prevent them from settling away from the filter...Usually placing the filter in the corner of the tub. The rest of the tub is bare, and I've had pretty good luck using this to prevent larvae from getting sucked into the filter, and keeping the water clean. The bare portion of the tub is easy to wipe clean with a sponge.

Most larvae, if fed regularly, grow beyond 'intake size' fairly quickly. However, I've only done this with axolotls and maculatum larvae.

The filter has an adjustable flow that I keep on it's lowest setting. The pea-sized gravel surrounding the uptake don't seem to affect it's filtering ability, and there are far less entire water changes to deal with.

 

[caleb]

Regarding gravel- Pat Wisniewski suggested in the 1980s that young larvae of Euproctus might do better with a gravel substrate, as they will be able to keep their gills exposed to the water by resting between the gravel. With a bare base, they might roll onto their sides, affecting the gill function.

Obviously this wouldn't apply to species whose larvae are able to hang on vertical surfaces.

I don't know if anyone's experimented with this since...

 

[edward]

Hi Caleb,
To date, I am only aware of this being a problem with some fast stream dwelling species. This does not appear to be an issue with slow or still water species (here is the reference Wisniewski, Patrick J. 1986. Substrate and tadpole survival in Euproctus a. asper. British Herpetological Society Bulletin. (18):19. )

Jen,
The biofilm will also be heavily populated with the nitrigen fixing bacteria.

Ed