Rhonda Bracey: At Random

I just realised that I haven’t written a few updates about ‘my’ cockroach that’s now living with one of the entomologists from the Australian Museum (do a search on this blog for ‘cockroach’ to see my earlier posts — or just click this link). The quoted bits are from his emails to me advising me of the progress of my cockroach.

April 2010:

At least one of the oothecae ‘your’ female produced did hatch – the young were a pale grey all over – I only found 5 but then they all promptly disappeared into the leaf-litter and in the few rudimentary searches I’ve made I haven’t seen them again. This may mean nothing as their mother can remain hidden and unseen for a few weeks until I get worried and start looking for her – whereupon she is found hale and hearty. The species seems to be very good at avoiding detection and the smaller ones due to their size even more so.

The ‘related’ species they are in with – which seems to be not that closely related based on behaviour – is far more obvious and diurnal and so far NONE of their eggs have hatched. The cockroach expert hasn’t been down to Sydney to have a look at all the bodies of yours and various others – for a while yet so I have nothing to report on that other than it seem to check out now pretty well with Polyzosteria cuprea but the expert on the group will have to let us know if this is indeed correct and or if the locality is a new record for the species or not. Either way they are very useful specimens for us of a species we had very few specimens of before.

8 October 2010:

… your original female cockroach has just emerged from her winters sleep and seems as healthy as ever. I haven’t seen any babies as yet but then considering how well she can hide amongst the leaf litter in the cage there is still hope that they made it through to winter as well.

25 October 2010:

Just thought you’d like to know I saw your cockroach again yesterday and she was carrying yet another ootheca. I have now caught her out of the main cage and put her in a smaller one where I can better track the progress of the eggs. Anyway clearly P. cuprea is a very hardy long lived species! They are also very good at escaping detection – I still haven’t noticed any babies but can’t discount them as the original female was so good at hiding that several times I assumed she was dead and started looking for her body only to find her hale and hearty.

I replied, asking Martyn who the female had mated with! His reply:

Well that’s where it gets tricky. Most insects mate only once and store the sperm for the reproductive life of the female (this can be years). Some long lived species mate several times over a long lifetime, and some, like certain beetles and certain cockroaches can mate with multiple partners and the eggs are either fertilised with a mix of sperm OR the next eggs laid get fertilised by the last male to mate with her – in the latter case the earlier sperm are still viable but must now ‘wait their turn’.

Needless to say this is what I am hoping is the case here as the other species in there with her – although of the same genus – is of a different sub-set of that genus without the speckled legs. It is unlikely to be viable as a cross as a result OR maybe she’s laying blanks like a chicken does. The purpose of this segregation now is to see if the eggs hatch and what they look like.

4 November 2010:

Just thought you’d like to know that the last years babies are starting to appear now in the cage. All look like perfectly normal P. cuprea but all I have seen so far (about 3 ranging from half grown to adult) seem to be females so it might be option 3 and the result of parthenogenesis or it might be that this species throws more female offspring than males. Either way it is good news and the result is a success so far. If the colony can continue from here will be the next milestone.

More updates as they come to hand…

August 2014: The final chapter