Jansenii / Oxycephalum

Care Sheet


 by Freight Freitas

Setting aside the many issues that have previously been discussed regarding captive care, I now present the second most major hurdle in my work with Gonyosoma. In the number two spot is the successful incubation and hatching of eggs.

Full term incubation, and subsequent successful hatching of Gonyosoma eggs has been a puzzling, frustrating, and at times highly disappointing process for many keepers. There have been many substrates, moisture and temperature regimes, and incubation methods attempted. Many have failed. Some have produced little more than mediocre results. Yet, a few have been met with profound success. Though I too have experienced abysmal failures in the incubation process, I have overcome many of the issues presented throughout the process, and now have a very high successful hatching rate with Gonyo eggs. It should also be noted that there are numerous records of the successful hatching of oxycephala eggs in Europe.

My incubator is a 48 quart igloo plastic cooler (ice chest) with a small plastic rack inside made simply of a ¾”plastic egg crating deck and ½” pvc legs. At the inside bottom of the cooler lies an 11”x23” Ultratherm under tank reptile heat pad, which is controlled by an ESU 1000w thermostat. There is also a remote digital thermometer used to accurately read temperatures inside the egg box. The egg box is simply a Ziplock 10”l x 10”w x 3”d plastic food storage container with small ventilation holes perforated into the lid, and a slot in the side of the lid for the thermostat and thermometer probe wires to pass through. The incubation substrate is moistened perlite, which provides moisture, as well as humidity for egg development, but has excellent drainage properties due to its granular texture. The perlite should be moist to the touch, but not soaked or soggy, as overly moist conditions can easily drown the developing embryos. There should be very little water collected at the bottom of the egg box after moistening the perlite with water. I use this as my guide to select the proper moisture regime.

Eggs should be placed on top of, and not into, nor buried in, the perlite substrate. The eggs of oxycephala, black janseni, and oxy/jansen hybrids need only be minimally exposed to the perlite as a water source. The eggs of black tailed Sulawesi janseni should be placed on a piece of egg crating, or some other porous and non-absorbent mesh, that is placed on top of the perlite to separate the eggs from direct contact with the moistened perlite substrate. This is a similar method to that used by Chondro python breeders. The lid of the egg box is simply placed loosely on top of the box, and is only fastened securely at the end of incubation to prevent hatchling escape. I sometimes use a screen lid on the egg box to prevent over collection of condensation on the lid, which can inevitably drip on the eggs. Continuous exposure to such water droplets can drown the embryos and over expand eggs, and thusly should be avoided. Such droplets also cause an odd crystallization on the eggshell surface at the point of contact. I have not noticed any detrimental effects from this process, but prefer to avoid it if possible.

There has been rather a broad array of incubation temperatures used with Gonyo eggs in the past ranging from 79-89F (26-32C). Incubation times have been recorded ranging from 87-182 days, which has been at least somewhat dependant on temperatures. More recent information suggests that cooler temperatures and moderate moisture provide a smooth and much more stable path to successful hatching of babies. My own personal success has been achieved by keeping all my Gonyo eggs under 80F for the entire incubation period. The eggs are generally incubated close to hatching at 78F (+/- 1.5F). Toward the end of incubation the temps are dropped slightly into the 76-77F range with 76F being the lowest temp. I also increase the moisture in the substrate slightly, and have found that wrapping moistened folded paper towels around the outside of the clutch making contact with each egg helps to soften the tough egg shells. I do not suggest covering the eggs at any time during the incubation process because these eggs need to be continuously monitored for over-expansion, desiccation, and outer shell deformities throughout the entire incubation process. These are not leave alone eggs.

Incubation times can be highly variable between clutches incubated at the same temps. To date I have only hatched two clutches of oxycephala eggs, which hatched in a range of 110-119 days. I have hatched three clutches of black tailed Sulawesi janseni, which hatched in a range from 125-145 days. All six clutches of oxy/jansen hybrids have hatched in a range from 106-137 days. Initially I started to incubate Gonyo eggs closer to 80F, and over time have found that the 78F range is more appropriate. Despite this slight variation in temperature I still see inconsistencies in overall incubation durations. Janseni eggs, which have been consistently larger than both oxy and hybrid eggs do appear to take a bit longer to hatch. Some have hypothesized that egg size can be a determining factor in overall duration to hatch, which does not appear to be an unreasonable assumption. However, there are a number of factors that set the Sulawesi janseni apart from the rest of the Gonyos including very tough spongiose eggs, large heavy bodied babies and adults, a semi to mostly terrestrial lifestyle, as well as this being a species isolated to one specific island.

All the Gonyo eggs from the species I currently work with appear rather porous and sponge like, and have the ability to take up excess water from the substrate and expand. This expansion can have rather adverse effects on the structural integrity of the egg and should be kept in check if noticed simply by drying out the eggs. When laid, the outer eggshell appears uniform and constant. As the egg develops there will be some increase in both size and weight from both embryonic growth and environmental moisture uptake. Expansion can later be observed as the surface of the egg shell begins to appear striated as long thin strands/stripes of shell running horizontally side by side from one tapered end of the egg to the other. If these strands begin to separate vertically as cracks or splits, or they begin to expose the inner shell membrane (chorion) underneath, then measures need to be taken to dehydrate the eggs, and thusly decrease their turgidity, literally shrinking the egg back to a safe size. Removing the lid of the egg box, and/or opening the lid of the incubator slightly to allow airflow should decrease humidity enough to slightly dehydrate the eggs. In the case of severe expansion, placing the eggs on egg crating above the substrate while ventilating the egg box and incubator at the same time is effective. Generally it will be the eggs in direct contact with the substrate at the bottom of the clutch that expand the most. It is thusly advisable to place a small folded piece of moistened paper towel just at the ends of eggs that are at the top of the clutch during both normal incubation and during the dehydration process to insure moisture availability.

Black tailed janseni eggs appear highly spongiose and have an incredible ability to absorb moisture. As I discovered with my first clutch, these eggs will expand like balloons literally separating the outer calcified portion of the shell from the inner membrane (chorion). I unfortunately made a grave mistake with this clutch by not only placing the eggs on the perlite substrate, but also by surrounding them with sphagnum moss as well. This clutch was laid in a tall stack that prevented the top eggs from being anywhere near the perlite, so it seems I overcompensated with the moss and ended up adding too much moisture around the eggs. I also destroyed an entire clutch of oxy/jansen hybrids in the process. In the last 2-3 weeks of the incubation period both the continuous uptake of water from the substrate, as well as the incredible increase in size of the babies literally caused the eggs to burst! The tremendous pressure inside forced the inner extra-embryonic membranes to be partially expelled out of the shell, and soon after a green fungus formed on the eggs killing the nearly fully formed babies inside. Attempts to bandage the eggs with gauze, tape, and triple antibiotic ointment all failed, and only one in a clutch of seven fertile eggs hatched. Upon dissection of the eggs I discovered that the babies are actually gray until the very end of incubation. One of the babies actually had a green area on the side of its neck indicating a color change just before hatching, as all jansen babies hatch out in some shade of green.