Species Confusion? DD. imitator vs. lamasi

John Skillcorn

This short article was originally meant to be a very general account of breeding Dendrobates imitator, a very small and very arboreal Peruvian frog.  A couple of months ago I completed that article, but have been forced to put it to one side, at least for the time being.  The truth of the matter is I have become very confused about the exact species of frog about which I had been writing!

The frogs were bought on my behalf in Holland earlier this year (2001), and were sold under the name of D. imitator Panguana.  So far, no problems.  The frogs turned out to be two males and one female, and started to breed almost as soon as they were put into their vivarium.  Only now have they started to slow down a little.  

I have kept and bred D. imitator before, and have photographs with which I can compare my frogs then and now.  My first D. imitator were, indeed, textbook examples, down to the two black patches on the snout.  I had, and still have, no doubt that they were true D. imitator.  The frogs with which I am currently dealing, however, are not the same.

Two of the frogs - a male and the female - have parallel lines running the length of the body with no interconnecting bars.  These lines are reasonably broad and of a metallic yellow/green.  The legs are pinkish grey in colour, and are covered in medium-sized, round, black spots.  These characteristics are passed on to the offspring in about 60 percent of cases.  This is quite unlike my original frogs which had a much more reticulate pattern on their limbs, while their back was coloured with a very fine tracery of metallic green lines.  My main cause for concern, however, was the tadpole.

The males transport the tadpoles.  They will carry their tadpoles around, one by one, for over twelve hours if no suitable body of water is available.  They seem unwilling to use film canisters and much prefer natural bromeliads.  Unfortunately, the tadpoles are almost impossible to extract from these niches, so they were left in situ for their parent/s to rear.  Occasionally, the males do use the film canisters, and it is from there that I obtain my tadpoles for artificial rearing.  In addition, I might sometimes find clutches of eggs (always just two) and use them similarly.

The tadpoles are very dark grey - almost black - on hatching.  However, after only a few days they begin to develop a metallic, almost fluorescent, stripe across the top of the snout.  This colouration is quite striking, and even though the tadpole might be deep inside a bromeliad leaf axil its presence is made obvious.  And this is where my confusion begins.

Now, I am the first to admit that I am no expert on Dendrobatid frogs.  Nevertheless, I do know about the frogs I have kept and bred.  Moreover, I do have the ability to make intelligent conjecture, and this is what the rest of this article is dependent upon.

While corresponding with other members, and by researching other Dendrobatid-based Websites, it has been suggested to me that this fluorescent stripe across the tadpole's head is unique to only one species.  And this species is not D. imitator.  It is, in fact, a known characteristic of D. lamasi.  Peter Kuitert informs me that adult D. lamasi currently known and identified as such in the hobby have broad yellow stripes.  He also relates that this does not represent the holotype very accurately.  However, he considers that the frog known as D. imitator Panguana fits the holotype closely, apart from the ground colour of the legs being grey instead of blue.  The Swedish Dendrobatid Society carries good quality photographs of these frogs, and those with Internet facilities might want to have a look for themselves: 
http://hem.passagen.se/frogkeeping/index.html

Peter also mentions differences in their call volume and frequency, but notes that these might be due to variations in the overall size of the frogs themselves.
 
So what purpose might these coloured stripes serve?  I have made some observations of my own and have come to my own conclusions.  It is always the male who transports the tadpoles, quite unlike, for example, D. pumilio.  Females, therefore, can have no idea where the tadpoles are.  Literature states that the tadpoles are both egg feeders and omnivorous.  So if they are fed on eggs, how does the female know where to place the food eggs seeing as only the male knows where he has put the tadpoles?  I have noted many times that a male will constantly call to a female, and the pair will climb along the bromeliad leaves until they are in very close proximity to the water in one of the leaf axils.  Here, the male will actually sit in the water while still calling to the female.  The sound he makes changes at this time because his vocal sac is at water level, and the water alters the pitch of his call.  But it is also at this time that the tadpole begins to behave very strangely.

Normally, as soon as tadpoles of this species are disturbed they swim deep into the leaf axils, from where they are inextricable.  After a while, when all is once again calm and quiet, they will reappear.  However, when a male is present the tadpole is very much in evidence, swimming around the male's hind legs and wriggling and twisting its body in an eel-like manner.  His fluorescent upper lip glows in the dim light of the bromeliad.  The female eventually lays one or two eggs at water level.  I do not know if these are actually fertilized by the male.

In closing, I believe the coloured stripe is a signal to the female to produce a food egg for the larva, and that she is led to larvae for precisely that purpose by the male.  Hence the vocalisation of the male, together with the visual signals from the tadpole, must act as strong stimulants to the female for the production of food eggs.  In the wild, these signals could be vital for the survival of the tadpole.  Furthermore, it is my belief that, although the colouration of the parents might vary a great deal (as in D. pumilio, for example) it is very unlikely that there will be much variation in tadpoles either in their colouration or their habits.  And if one of the characteristics under observation is a fluorescent stripe along the upper jaw, then I cannot see how some tadpoles could carry this signal and some not, yet all still have an equal chance of being identified by their parent and thence being supplied with food.

Remember, though, that this article is concerned with solving the true identity of the frogs I am keeping.  If you have bred both DD. imitator and lamasi I would like to hear from you, especially if you can give me descriptions of their respective larvae.