Mad Science.
The latest cool reptile research from around the globe.
What came first – the lizard or the egg?
W
ell, in this case, it was the eggs, but the lizard
wasn’t far behind. Recently, researchers observed
a Three-toed Skink (Saiphos equalis) lay eggs; later the
female gave birth to a live young from the same litter, the
first time this has been witnessed in a vertebrate.
At first glance, there is little remarkable about the Three-
toed Skink, other than the fact that it is sufficiently
distinct to warrant its own genus. It is a small, coppery-
coloured lizard with shortened limbs that is common near
the east coast of Australia, from central NSW to southern
Queensland. It burrows under surface debris and feeds
upon invertebrates at night. But S. equalis is one of only
two Australian skinks that are capable of bimodal
reproduction (perhaps that should be trimodal – more
later); that is, they both lay eggs and bear live young, and
this makes them of special interest to evolutionary
biologists.
Egg-laying is the ancestral strategy, and although the
transition to live birth requires significant physiological,
anatomical and behavioural change, this has occurred
independently in many different lineages of reptiles.
There are advantages to both forms of reproduction.
Egg-laying is less arduous and entails less risk for the
female, as she does not have to carry large young to term
in a lengthy pregnancy. This means that she can take
advantage of favourable conditions, with bigger clutches,