A Recipe for Hundreds of Millions of Years of Success by Chip Hannum.
Take some eggs, fresh water, sunlight and let them simmer for just 48hours at 22°C…
Conversely, water in an established body has a high level of dissolved minerals and organics - it has relatively high osmotic pressure. Why is this important?
Triops, especially when young, lack the mobility, size, and biological weaponry to avoid any sort of predator their size or larger. An established body of water may contain fish, aquatic insects, amphibians, or even other triops which will make short work of the hatchlings. Further, an established body of water may be an older pool which will not last much longer. So, unless water conditions indicate a new freshwater body, the eggs won’t hatch.
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| Left: the intact egg of L. apus lubbocki; Right: cross section of egg showing the alveolar layer structure lying between the outer and inner membranes. Below you can see Triops cancriformis about to lay some eggs (clutch of pink dots near the rear). |
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Just as important as not hatching into a pond full of hungry minnows, is not hatching into 20 cm of mud. The shell of triops eggs has an alveolar layer - this means it is a spongy matrix of hundreds of tiny, interconnected chambers, all in an egg less than 0.5 mm! When the eggs are first laid, the alveolar layer is filled with fluid and the egg sinks. Here, the eggs can be buried in sediment where they can begin their wait and are less likely to be eaten by the adult triops.
After drying, though, the alveolar layer is empty of fluid and instead filled with air. When the eggs are hydrated, if they aren’t buried in sediment, they will float to the surface and be exposed to sunlight. The presence of light is what tells the egg it isn’t buried and it is safe to hatch. After a period of floating, water again fills the alveolar layer and the eggs sink again; if they don’t hatch, they will again be buried to wait and avoid being eaten by their brethren that do hatch out.
The final trick is sensitivity is to environmental temperature. Triops eggs will generally hatch out within a temperature range of 15° - 30°C (59° - 86°F). Still, this is indicative of a wide range of environmental conditions and triops growth rate is directly tied to temperature right up it becomes life threatening. As a consequence, there is a narrow range of temperature for each species that is indicative of ideal conditions, neither too cool, nor too warm. If the environment is cooler than optimal, growth rate will be impacted and hatchlings may not have enough time to develop before the pool dries. If the environment is too warm, the hatchlings may die once the pool reaches its maximum temperature. Hence, the closer to this ideal range, the higher the percentage of eggs that hatch. Taken together, the adaptations involving their eggs make the triops into wonderfully cautious opportunists.
22°C (71.6°F) appears to be the optimum temperature for hatching.
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