Radiata2008(3)e

Oliver Römpp Mating,

Oliver Römpp Mating, oviposition and incubation I have been observing turtles of all four species to attempt mating and copulate on numerous occasions, but especially when there was a shift in temperatures, be it a function of the natural seasons or the result of my exchanging their water. Oviposition usually takes place in the evening or late evening. A nest pit of 5-8 cm in depth is excavated. Average clutch sizes vary from two or three in Acanthochelys pallidipectoris to five to seven or even more in the larger species. The eggs are hard-shelled and almost perfectly spherical. Incubation of the eggs has remained a challenge, as all of them probably need to pass through more or less pronounced diapauses. As yet, only a few keepers managed to successfully propagate these species in captivity, but these results were often sporadic and/or once-off events (Lehmann 1987); most have never been published. Artner (2007) was the first to successfully breed Acanthochelys spixii and Acanthochelys macrocephala over several years. The problem of propagating these turtles is aggravated by the fact that, like with many other South American turtle species, hatchlings often find it difficult to crack their eggs (Lehmann 1987). It is often presumed that babies are unable to penetrate the shell of their eggs with their legs because it is too solid (Lehmann 1987). Thus unable to leave its egg, the hatchling will inevitably perish if the keeper does not intervene in time. Relatively little information has emerged as yet regarding the required diapause. A period of coolness during incubation has Fig. 5. Spines on the hind leg of an Acanthochelys pallidipectoris. proven to be beneficial in any case, but which temperatures are best and how long this period should last are details that are still insufficiently understood. In Acanthochelys spixii, Acanthochelys pallidipectoris and Acanthochelys macrocephala it would appear that relatively low temperatures are required, whereas the species with the most northerly distribution, namely Acanthochelys radiolata, would only need a weak diapause at slightly reduced incubation temperatures. The shift from a cool phase to the actual incubation temperature then kicks off the embryonic development, which will normally ensure in the wild that the turtles hatch at a time when water temperatures are favourable and food is abundant. If artificially incubated eggs are not “deceived” with seasonal temperature changes, they remain dormant and the embryos fail to start developing. For a clutch of Acanthochelys pallidipectoris eggs, I initially selected a constant incubation temperature of 25-28 °C. Several weeks later, there were still no signs whatsoever that development had begun. A diapause of two 42 RADIATA 17 (3), 2008

South American Swamp Turtles of the Genus Acanthochelys months in duration at 15 °C was inserted, but no development was notable during the following warm phase either. Now, the eggs were again exposed to a cool phase, this time at 8 °C, for another two months before incubation was continued at 25-28 °C (see diagram). It was only then that development set in, with blood vessels forming to show that embryos were developing. Ten weeks later, one hatchling emerged (out of a total of three eggs). A similar situation is currently experienced with a clutch of Acanthochelys radiolata, which needed a moderate diapause at 18 °C to start showing signs of development in the shape of blood vessels. Janet Eldrige of Palo Alto (California, USA; pers. comm.) hatched Acanthochelys spixii as long ago as in 1991. Her case is noteworthy insofar as she had first sold her turtles and then the technical equipment of their terrarium while the latter was then left standing in a room with little heating. It took several months before the installation was eventually dismantled and it was only then that a clutch of eggs was discovered buried in the terrestrial part of the turtle terrarium. These were now placed in an incubator and hatched successfully. This incident demonstrates that the eggs require a cool phase followed by a warm one to terminate the diapause. Artner (2007) has been experimenting with incubation strategies for eggs of Acanthochelys spixii and Acanthochelys macrocephala for years. In the process, several clutches hatched after they had been exposed to two to three months at reduced temperatures of 12 °C and then incubated at higher values. It appears that even lower temperatures of 3-5 °C for a brief period of time will produce the desired results and can be applied to other chelonians, such as Kinosternon herrerai, as well. Another deciding factor appears to be the moisture level of the incubation substrate that is used after the cool phase (Artner 2007). I have been using a commercially built incubator (Lucky Reptile) for the incubation of eggs that require an intermittent diapause. This model is based on a bar fridge with Peltier technology and can be used in heating mode for the incubation of reptile eggs as well as in cooling mode for hibernating small tortoises and turtles. Temperature control is almost infinitely variable from 3 to 35 °C. This fridge is quite perfectly suited for setting a constant temperature between 3 and 18 °C and creating the necessary diapause. I have also been applying this method with success to the incubation of eggs of Macrochelodina expansa (Römpp 2004), which is a species from southern Australia that requires a moderately distinct diapause. Raising babies of these swamp turtles is generally easy. They are initially fed with live foods (red and white mosquito larvae) or small earthworms and frozen foods (mosquito Diagram: Course of temperatures including diapause for the eggs of Acanthochelys pallidipectoris. RADIATA 17 (3), 2008 43