Breeding and Egg Development of Hymenochirus boettgeri 

Log 5

by David Cecere 

April 21, 1998

50+ tadpoles B18-2

I am seeing a high mortality rate on B18-2 and I not sure why.  My culture from Blue Spruce is active and pure.  It doesn't seem likely that there are still cercariae present in the tank.  I'll be looking at some of the dead tadpoles under the microscope to see what I can see.  It's possible that the water flow in the tank is high enough that the paramecia are being swept out of the net too quickly.

I wrote Dr. Sessions who is conductiong Trematode research.  I explained my setup and tadpoles and asked him if the cercaria I saw could explain the 85 deaths in B13-2.  Here is his response:

Dear Dave,
This is absolutely amazing. Yes, I have seen tadpoles die as result of cercarial infestation. Also, I've heard from other people who have had strange deformities, possibly connected with trematodes, showing up in their captive frog populations. The figure you mentioned (13c) is of a kind of cercariae (called an "armatae" cercaria) that has a stylus on the oral sucker and can usually penetrate a tadpole wherever it wants to, and it can cause localized bloody damage. One species that we have identified is Paralechriorchis syntomentera. Most tadpoles are not unduly harmed by even a heavy infestation, but I can imagine that it could be devastating to really small individuals. I suggest checking your snails for infection. This can be done by smashing them in a petri dish and examining with a diseecting scope. I often see rediae as well as cercariae this way.
Stan Sessions

I did as he suggested and examined 3 snails last weekend.  I found what appeared to be a redia on one of my slides but I'm not 100% certain.  One thing I am certain of is the need to eradicate all the snails in that tank.
Keeping a pure culture: It's not that difficult if you follow a few rules.
When I ordered my paramecium I also ordered sterile medium and a 500 ml. Erlenmyer flask  An Erlenmyer flask is cone shaped with a flat bottom and a short neck.  It's very handy for keeping liquid culture medium because of its design. I placed the medium in the flask and boiled it for about 5 minutes to make sure everything was sterilized.  I covered the neck with a paper towel and let the medium cool to room temperature.  I carefully added the paramecium culture making sure not to get the neck of the flask wet on the inside.  I used a large wad of sterile cotton to stopper the flask.  The cotton is a good barrier to bacteria as long as it stays dry.  It also lets gasses vent from the flask and allows air in.  When I need more culture for the tadpoles I use a sterile eyedropper to move culture from the flask into a small container.  I've had my culture going since 4/16 and so far it is still uncontaminated.

My guess on how the tadpoles in B10-2 would develop legs was wrong.  The hind limb buds have elongated into small legs.  The knee joint is visible and what will become a foot can be seen. The tadpole can move the legs at the pelvis but the the rest of the leg does not appear functional due to a lack of muscle.  Several of the tadpoles with hind legs have also sprouted front legs. They're very tiny when they emerge and are just barely visible to the naked eye.

I have a favor to ask

I'd like to get some data about which companies are supplying H. boettgeri to pet stores in the US and where the frogs are coming from.  I made some calls in my area (Seattle, Washington) and it appears that the main supplier is African Northwest. They were willing to tell me that they buy theirs from "out of state" but that was all.  They are also willing to buy my frogs for 25 cents each which makes me think that they're not buying from a breeder.

If any readers are willing to make some phone calls to pet stores in their area I'd be happy to compile and post the information. When you talk to the pet store say that you want to talk to their amphibian supplier for some additional information on the frog, the Latin name for example.  When you talk to the supplier you can say that you just bought a couple of the frogs from such-and-such pet store and that you're curious about where they come from, etc.  Ask if they're captive bred or imported and if they're imported who is importing them.  I have a feeling it's a big outfit on the east coast but I'd like to know for sure.

April 28

7 tadpoles B18-2
25 eggs B21 (laid 4/27)

I received Sokol's 1962 paper this week.  Instead of verifying Rabb, Sokol's observations are in direct opposition to Rabb's on numerous points.  I wonder if Rabb even read Sokol's paper before writing his own.  It's now unclear whether I'm dealing with H. boettgeri or H. curtipes or even a hybrid of the two!  I am working on a point-by-point comparison so that others can see the discrepancies for themselves. I have also ordered Sokol's 1959 article to see if it might help clarify the issues.  Errors in observation are easy to make. I realized this week that I had made one when doing my tadpole illustration.  I will correct it and post the new illustration this week.  I will also be posting an illustration from Sokol's paper for comparison.  If there is a lesson here it's something like, Don't be too quick to make someone an "authority".

All the members of B10-2 are doing well.  All are showing signs of limbs and so far none have any abnormalities.  The oldest members have both front and rear legs and are becoming very frog-like in appearance and behavior.  I've been trying to coax them into eating chopped blood worm but they prefer the nauplii.

I made a few changes last week:

  1. I raised the temperature in the breeding tank from 75° F. to 81° F. on 4/22.
  2. I moved B10-2 to their own 5-gallon tank also at 81° F., pH 7.8 with filtration on 4/26.

I raised the temperature based on Sokol's assertion that curtipes tadpoles survive better at higher temps.  I have not lost any tadpoles from B18-2 since raising the temperature buts it's too soon to tell if that was the contributing factor. B-21 was the first batch laid since the temp. was raised.  The development of the larvae is going much faster and they should all be hatched by tonight.

May 2

40+ tadpoles B22 hatched 5/2

I've spent some time over the last few days going over Sokol's papers.  His paper from 1959 is in German but it contains 6 drawings of the H. curtipes tadpole which he refers to in his 1962 paper.  By comparing them to a deceased member of B-21 it appears that I'm dealing with H. boettgeri after all. I still believe it's possible that I'm raising a hybrid but I'm not going to commit myself to that until I finish doing my point-by-point comparison of Rabb, 1963 and Sokol, 1962.  I'm also going to scan some drawings from both papers and post them on the Illustrations page so that it will be easier to understand what I'm talking about.

A member of B10-2 died suddenly last night or early this morning. He looked well fed and otherwise healthy. I decided to see if I could figure out what killed him.  His body length was 8 mm and his overall length was 1.7 cm.  He was about 40 days old with well-developed front and hind legs.  His face had begun to elongate but he still had gills.  One of the drawings from Sokol, 1962 is a good likeness of him.

It's not easy dissecting something that small but using a magnifier on a makeshift stand and a desk lamp I managed to open his abdomen using a sharp X-Acto knife.  The likely cause of his death appears to have been intestinal blockage caused by unhatched brine shrimp eggs.  I removed over 2 dozen eggs from his abdomen. I try to be careful when I feed them to avoid putting the unhatched eggs into the tank but it's almost impossible to avoid all of them.  I see the unhatched eggs in the feces so I never worried about them causing any harm. Perhaps he had other problems or simply ate too many eggs at once and couldn't pass them.

Two of my oldest members of B10-2 will be frogs soon.  Their tails are shrinking at a rapid rate and they are breathing from the surface.  It appears that their gill slits have closed and they are relying on their lungs for oxygen.  The "oral tube", as Sokol refers to the cylinder-shaped tadpole mouth, has widened into an adult-like mouth.  Their behavior is changing to be much more like the adult frogs—they rest at the surface and use their front feet to dig into the gravel when looking for food.

Tips on examining tadpoles
If you decide to raise tadpoles you will definitely lose a few along the way and you might want to examine them under a magnifier or a microscope.  The biggest problem that I had was keeping the tadpoles  hydrated while I was examining them.  They will dehydrate very quickly when they are removed from water.  I solved this problem by using glycerin.  You can buy glycerin in 4 oz. bottles in drug stores or large grocery stores.  It's quite safe and is used as a moisturizer for chapped skin.  It's completely colorless and is soluble in water but it won't evaporate like water does.

The best way to examine the small tadpoles is to place one on a welled slide.  A welled slide has a small depression in the middle large enough to hold two or three drops of water.  Place the tadpole in the well and add a drop or two of glycerin. If you don't have a slide any small shallow container will work.

May 30

[I've been on a bit of a hiatus the last few weeks.  I will be resuming my regular log entries in June.]

About half of B10-2 have become frogs.  I lost a total of 6 tadpoles in the first several weeks after moving B10-2 to their own tank.  My guess is that all the deaths were due to intestinal blockages from unhatched brine shrimp eggs.  I am feeding B10-2 exclusively on chopped blood worm twice daily. The remaining tadpoles in this group are at various stages of development.  It seems to me that all the members of this group should have metamorphosed by now.  I'm wondering if there is a genetic reason for the slowness in development.  There is a remarkable variety in size and coloration of the frogs in this group.  The coloring ranges from a very light grey with slightly darker spotting to nearly black overall.  The largest is nearly 2 cm and the smallest is about half that size.

My most recent death in this group came on the morning of the 24th.  It was a tadpole (one of the smaller ones) at the stage shown here.  It appeared as though he had an infection on his tail.  The last third of its tail had a white fuzzy appearance. Under 400X it looks like a fungus—long strands of mycelium emerging from the fin tissue.  It could also be a infection caused by a streptomyces since the appearance would be similar.  I don't have any of the microbial stains that are needed to make a better identification. It's likely that his tail was injured by a larger tankmate during feeding. I've seen frogs bite each other when one gets too close to a another who is on the trail of a blood worm.  It doesn't appear to be an aggressive act, just overzealousness.

The last batch I've kept records for is #22 and was laid on 4/30.  I've had several batches laid since then but didn't take the time to make notes.  I am raising another small group of 8 tadpoles which is a combination of survivors from two recent layings.  A third batch died with 24 hours after I moved it from the hatching net to the floating tank.  I'm very puzzled by this.  I can't imagine what could account for the attrition.  One possibility is that that particular batch would have died off anyway due to some defect or problem with their development.

I am currently raising a batch of about 50 tadpoles that were laid on 5/26 (B5/26).  I am reasonably certain that I know which of the two females laid this batch: female #2.  I will keep records of their progress to compare with eggs and tadpoles from female #1.  I just started feeding B5/26 on a culture of mixed protozoa from Blue Spruce Biological Supply.

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