Captain Phasmatodea and the Attack of the (Not Really) Clones

Star Wars excitement just won’t seem to quit for our Life Sciences Team. Several of us have commented that the Imperial Storm Troopers seem to come in two flavors: clone and not-clone. Simple. But for the Phasmatodae, it’s complicated.

Phasmatodea is the group of insects that include all the stick insects. Here at Pacific Science Center you can see three representatives, Medauroidea extradentata and Lonchodiodes samarensis (Vietnamese and Samar stick insects) and Extatosoma tiaratum (Australian prickly sticks).

Some species of stick insects can reproduce without males, a process called parthenogenesis. Our Vietnamese stick insect population has not produced a male in years.

This is a fast way for a female to make her own “clone army”, producing large numbers of offspring without the risks and lost energy of seeking a mate. For an insect with an abundant food source, this lets her colonize it faster. So why do some of their near relatives go through the entire mating thing?

It turns out that the stick insects’ process is little more complex and varied than creating identical clones as single cells do (or sea anemones). The female doesn’t make duplicates of herself, but instead generates a bit of diversity by creating eggs with different combinations of her own chromosomes. Like shuffling the same cards again and again, she will produce many combinations. As long as the combinations fit the environment, this is a speedy and efficient system.

But there is no room for new genes to be introduced. Over time, species that become parthenogenic become less and less able to mate and get locked into their reproductive pattern. When the environment changes, it may be harder for these species to adapt, as they have a smaller group of genes to draw on. Under such circumstances, a similar species that reproduced sexually might prevail.

Again, it’s complicated.

For the in depth story please see the following articles:

http://phasmid-study-group.org/sites/phasmid-study-group.org/files/More1996.pdf

http://link.springer.com/article/10.1007%2FBF00328476

http://rspb.royalsocietypublishing.org/content/280/1764/20130823.abstract


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A Stick Bug Mystery

When Animal Care recently received a shipment of stick insects identified as Baculum extradentatum, (Giant Vietnamese stick insects), we naturally assumed that would be what we were getting. We were planning on adding this shipment of walking sticks to our current population to add in some genetic diversity and hopefully a few males to our all-female parthenogenic group.

As soon as we unpacked this new group of phasmids, it was clear that they were not the same as our current population. Perhaps we were looking at males instead of all the females we are accustomed to. But soon we realized that there were more differences. We were looking at a new species.

When we receive a new species of stick insect, we don’t simply slap a new sign onto a cage. These animals have the potential to become as invasive as the Indian stick insects in California. We first needed to figure out what species these insects were and then make sure we had a permit for them – fast! Otherwise, we wouldn’t be able to keep the new shipment.

Thanks to the powers of the Internet, Lead Animal Caretaker Lauren Bloomenthal contacted phasmid authority, Paul Brock, of London’s Natural History Museum. With full body photographs and a couple of shots of the insect’s head and genitalia, the expert soon replied with a name: Lonchodiodes samarensis. Their common name is Colorful Samar walking stick and "colorful" they are!

Unfortunately, even though we had a name, this species still wasn’t on our permits, so their fate was still up in the air. Life Sciences Manager Sarah Moore contacted our officer with the United States Department of Agriculture and explained our situation, fearing that nothing could be done to keep these animals. But he wrote back to say that the USDA would add the phasmids to our permit. We could keep and display these beautiful stick insects! Perhaps our excellent record of care worked in our favor to make this possible.

Lonchodiodes samarensis are now on display in the Insect Village. They are originally native to the Northern Province of the Island of Samar in the Philippines. Very little information is known about this species but we look forward to learning more about them as we see them grow and thrive in their new home.


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