Breeding and Egg Development of Hymenochirus boettgeri 

Log 4

by David Cecere 

March 24, 1998

40+ tadpoles (Batch 10/11/12)
80+ tadpoles - Batch 13 (laid 3/22)

Batch 11 is 14 days old!  This beats my previous longevity by 2 days.  There has been some attrition (which I expected) and based upon the size of the dead tadpoles my guess is that most of them where from Batch 12.  I am still adding both the brine shrimp larvae and the infusoria because any survivors from Batch 12 are still too young for the brine shrimp.  Most of the tadpoles appear to be  feeding on the shrimp. They swim through the cloud of shrimp repeatedly changing their direction numerous times within a few seconds.  Since the shrimp are from my frozen supply of larvae they don't stay suspended in the water for more than a few minutes.  I use the Monoject syringe with tubing attached to gently push a stream of water upwards from the bottom of the net.  The tadpoles quickly resume feeding on the floating shrimp.  I also place shrimp into the submerged algae.  I've noticed that the older (larger) tadpoles will feed from a position lower in the net than the smaller (younger) ones. My theory is that the younger tadpoles detect the infusoria that naturally collect just below the water's surface. I believe that the tadpoles detect the infusoria's motion by a tactile sense, possibly by means of some type of  lateral line organ.

Batch 13 is residing in a 3"X6" floating tank designed for breeding guppies.  It has holes in the bottom to allow an exchange of water within the tank.  I will try raising this batch in the tank as it's larger than the net and I have better visibility of the tadpoles.  This last batch has also had a very high viability with fewer than a dozen eggs failing to develop.  Most of this batch had hatched by 07:00.

A note on infusoria: My current culture was started on March 17.  This morning I verified with my microscope that the culture is still viable with a high concentration of protozoa and paramecia.  I keep the container covered in a room that stays between 65° and 70° F.  I removed the excess lettuce after 3 days to prevent bacterial overgrowth.  There was an odor of sulphur after 4 days which dissipated by day 6.

March 27

40+ tadpoles Batch 10/11/12
80+ tadpoles Batch 13
Batch 14 laid 3/25
Batch 15 laid 3/26

Needless to say, I have no shortage of eggs or tadpoles.  I am feeding Batch 10/11/12 (B10-2) exclusively on brine shrimp larvae (nauplii).  I added live nauplii this morning and the response of the tadpoles was definite and immediate: swimming through the suspended nauplii and feeding actively.  The appearance of  B10-2  has not changed except for their size.  They are longer by about 1 mm. and wider by about 1 mm.  I have had zero attrition for the past 2 days. I will try raising some of the nauplii to the next stage so that the tadpoles in B10-2 will have larger food.

I started adding tadpoles from Batch 14 to the breeding tank where Batch 13 is living.  I will do the same with tadpoles hatching from Batch 15.  I will refer to that combination as B13-2.

My infusoria culture from March 17 became very alkaline (pH about 9.0).  I threw it out and started a new one on 3/25 (about 1 liter).  In addition to lettuce I also added 5 drops of Liquifry No. 1 on 3/25 and 3/26 to speed the growth of the infusoria.  I will check the culture tonight for pH reading and viability and if all is well I will start adding it to B13-2.

March 30

50+ tadpoles B10-2
80+ tadpoles B13-2
Batch 16 laid 3/30

B10-2 has continued to grow and some are showing limb buds near the base of their tails.  B13-2 is feeding on infusoria from my new culture.  I placed B10-2 in a breeding tank like B13-2 is in.  I modified the tank by cutting off the bottom and replaced it with the very fine-meshed nylon from a filter bag.  The filter bag was purchased from an aquarium supply store.  I modified the tank to prevent the nauplii from falling through the holes in the bottom.  I can see the tadpoles much better in the tank and realized that I have about 50 or more.

I have had no attrition in B13-2 so far.  This is exceptional compared to the attrition that I had been seeing in earlier batches. I lost one tadpole from B10-2 on 3/28.  He was the smallest of the group and I suspectthat his problems were cardiovascular.  I will be using the dead tadpole for my illustrations.

April 5

50+ tadpoles B10-2
Batch 17 laid 4/1

The good news: B10-2 is continuing to develop.  Mose are showing limb buds that will become back legs. They are continuing to grow with the largest at about 1 cm. in length and about 3 or 4 mm. wide.  I am raising nauplii in a 4 liter (1 .25 gallon) container which gives me a ready supply of live food for the tadpoles.  For those interested, the nauplii are in a solution of 11 grams (4 oz.) of marine salt to 3.78 liters (1 gallon) of filtered water at 30° C. (85° F.).  The container is kept covered to exclude as much light as possible and gentle aeration is provided.  The nauplii are being fed with Liquifry No. 1.

The bad news: B13-2 had 100% attrition over a 48 hour period between 4/1 and 4/3.  I was very surprised and suspected that my infuoria culture had died out and that the tadpoles had starved.  I viewed a sample at 100X and saw a lot of activity.  I also saw a worm that turned out to be in the order Turbellaria as shown in the example labeled "21".  The worm itself isn't harmful to the tadpoles but its parasitic larva (cercaria) is.  I had seen a cercaria in my culture a week or two ago and didn't know what it was.  I took note of it because it wasn't like any paramecium I had ever seen but I never suspected that it was dangerous to the tadpoles.  Based on what I've read so far, the cercaria will invade the abdominal cavity of the tadpole and cause problems when it forms a cyst.  There is a Web site that discusses this problem as it relates to deformities in frogs.  I believe that due to the small size of the Hymenochirus tadpole the attack of the cercariae killed them instead of merely causing abnormalities.  I fear that 3 tadpoles from B10-2 are also infected.  They each have a gas bubble in their abdomen which is large enough to turn them upside down.  They are still feeding however.  I've noticed that when they fill their stomachs with nauplii they are able to swim normally again.  I will continue to watch them.

The main question on my mind was where the worms came from.  I was stumped for awhile until I remembered that I had used water from my other tank to start my infusoria culture and that that tank has two aquatic snails.  I learned a hard lesson but it was even harder on the tadpoles.

April 10

100+ eggs B18-1

B10-2 is still going strong. The three tadpoles I observed last week that had gas trouble have recovered. They are probably playing host to one or more cercarie so I'll be keeping a watch for abnormalities.  The limb buds are continuing to grow but don't look like legs yet.  I just tried a new food: frozen adult brine shrimp. I used a spoon to smash the shrimp into bite-sized pieces.  They seem to accept them and even take on the larger pieces. Motion seems to be an important factor in stimulating the tadpoles to feed.  At this stage they appear to be locating their food by sight.  I've found that blowing water down toward the bottom of the enclosure will cause the tadpoles to begin feeding as the bits of food swirl by.  I have also seen some of the larger tadpoles picking food from the bottom.  I hope that the frozen adult shrimp proves to be acceptable as this will save me the work of hatching the nauplii.  I've had problems keeping my nauplii cultures alive for more than three days.  I suspect that the Liquifry is not a good food for them despite what the package says.

I didn't save any eggs from batch 17 because I was concerned that there were still high numbers of cercarie in the tank.  I was also concerned about what to feed a new batch since I don't want to risk another disaster with a "home grown" infusoria culture.  I am assuming that any remaining cercarie have died off by now.  I have ordered a pure culture of paramecium and sterile medium from Blue Spruce Biological Supply to serve as food for B18-1. B18-1 is a combination of batches 18 and 19 are are due to hatch by 4/12.

I've completed an illustration (finally) which shows a profile view of a tadpole at about 25 days of age.  I should have it ready for the Web early next week.

I am trying to aquire reprints of two papers by Sokol that Dr. Rabb referenced in his paper.  I want to read them because they describe Hymenochirus tadpoles in detail.  I'm curious to see if my specimens match Sokol's descriptions.  I will post excerpts if I manage to find copies.

April 17

100+ eggs B18-2

B10-2 is continuing to develop but the changes in the past week were not as significant as they have been in previous weeks.  The largest tadpole is now over 1.5 cm. long.  It's apparent that hind legs are developing under the skin.  The limb buds are continuing to grow and metamorphosis should happen in the week to 10 days.  I've added eggs from batch 20 to the ones from B18-1. The older tadpoles are feeding on the culture from Blue Spruce.

I was able to locate a source for Sokol's papers. The University of Washington has them in the Journal Copiae. His paper from 1959 is in German but the one from 1962 is in English and is titled, The tadpole of Hymenochirus boettgeri.  I ordered a reprint of that paper and it should be arriving soon.

I've posted an illustration of a 25 day-old tadpole.

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