'Stick men' may be rendered obsolete in insect world

March 24, 2010
Dr Mary Morgan-Richards with a female stick insect.

(PhysOrg.com) -- Male stick insects are becoming increasingly redundant, with new research showing some New Zealand female stick insects can reproduce as efficiently on their own as with a male mate.

Not only that, the females capable of reproducing without male help, always produce female .

The research, by Dr Mary Morgan-Richards of the Ecology Group, describes the distribution and of sexual and asexual populations of the stick insect.

The work was a collaboration with Dr Steve Trewick, also of the Ecology Group, and Dr Ian Stringer, from the Department of Conservation in Wellington. The findings featured in a paper entitled Geographic parthenogenesis and the common tea-tree stick insect of New Zealand, published in the International journal Molecular Ecology.

The team conducted several experiments involving the reproduction of the species. Some populations have equal numbers of males and females that reproduce sexually, but others have unmated females that lay eggs that hatch and produce offspring identical to the mother, a process known as parthenogenesis.

The research also indicates that all of the southern parthenogenic populations seem to have the same . “That was unexpected,” Dr Morgan-Richards says. “It seems extraordinary when any single female is capable of reproducing parthenogenically.”

The team took females out of sexual populations and raised them on their own. Despite the lack of a male to mate with, the stick insects that usually reproduced sexually were capable of reproducing asexually.

“All of the parthenogenic populations of stick insect are to the south in New Zealand compared to the sexual populations more to the north,” Dr Morgan-Richards says. They don’t have a clear idea exactly of why that is but it seems to fit with the idea of range expansion—organisms moving to warmer places further north when the climate cools and expanding their population mid-range by going south when the climate warms.

The researchers found similar hatching success in mated and unmated females. Mated females produce equal numbers of male and female offspring, with most hatching within 9-16 weeks. In contrast, most of the offspring of unmated females were female, and the eggs took 21-23 weeks to hatch.

The difference in the development rate of the eggs “may have to do with the mechanism that they use to grow without sperm—but we don’t know", Dr Morgan-Richards says. She suggests that competition between the two sexual forms could be influenced by an extended development rate in the south.

Females from sexual populations that had access to mates did not reproduce asexually, even though they were capable of doing so. Also, from parthenogenic populations were able to reproduce sexually if they were given a male, but only about 10 per cent of their offspring were the result of sex. “It seemed that reverting to being sexual isn’t an easy step.”

The next phase of the research will try to determine the cause of such low rates of sexual reproduction from formerly parthenogenic populations.

Explore further: Do female guppies risk their lives to avoid sex?

Related Stories

Do female guppies risk their lives to avoid sex?

June 8, 2006

Sexual harassment is burden that females of many species face, and some may go to extreme lengths to avoid it. In a paper published in The American Naturalist, Dr Darren Croft from the University of Wales, Bangor and a research ...

The cost of keeping eggs fresh for mother cockroaches

February 26, 2007

One of the defining differences between the sexes is in the size of their gametes. Males make many tiny sperm while females make only a few large eggs. This suggests that sperm are cheap while eggs are expensive.

Sex in the morning or the evening?

June 26, 2007

Most research on sexual conflict ignores the fact that the fitness pay-offs of mating may change drastically over a short timescale, for example over a single day.

Sex is thirst-quenching for female beetles

August 28, 2007

Female beetles mate to quench their thirst according to new research by a University of Exeter biologist. The males of some insect species, including certain types of beetles, moths and crickets, produce unusually large ejaculates, ...

Orchid sexual deceit has male wasps in a loved-up frenzy

April 29, 2008

Orchids are admired by humans and insects alike, but according to Macquarie University research, one Australian wasp is so enthralled by ‘Orchid Fever' that actually he ejaculates while pollinating orchid flowers.

Female guppies risk death to avoid sexual harassment

August 6, 2008

Sexual harassment from male guppies is so bad that long-suffering females will risk their lives to escape it, according to new research from Dr Safi Darden and Dr Darren Croft from Bangor University. Their work, which was ...

Recommended for you

Study suggests fish can experience 'emotional fever'

November 25, 2015

(Phys.org)—A small team of researchers from the U.K. and Spain has found via lab study that at least one type of fish is capable of experiencing 'emotional fever,' which suggests it may qualify as a sentient being. In their ...

A huge chunk of a tardigrade's genome comes from foreign DNA

November 23, 2015

Researchers from the University of North Carolina at Chapel Hill have sequenced the genome of the nearly indestructible tardigrade, the only animal known to survive the extreme environment of outer space, and found something ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.