In the absence of sexual prospects, parasitic male worms go spermless

Nov 10, 2008

When females aren't around, one species of parasitic nematode worm doesn't even bother to make any sperm, reveals a new report in the November 11th issue of Current Biology, a Cell Press publication.

" This is very unusual for a male to need a female to be present before he produces sperm," said Christine Griffin of the National University of Ireland, Maynooth. "We searched the literature but could find no report of this in any other animal. Animals have evolved all sorts of strategies, some quite bizarre, to increase their lifetime reproductive success, but this particular one does not appear to be common." Lifetime reproductive success refers to the number of offspring produced over the course of a lifetime.

Scientists have generally considered sperm production to be cheap relative to the production of eggs in females, she said. But that notion has been challenged of late in animals that must produce a lot of sperm or particularly large sperm. The males of some other species of rodents, fish, and insects, for example, cut back on sperm according to their social circumstances. But they generally don't go without.

The researchers haven't yet shown how this behavior in the parasitic nematodes known as Steinernema longicaudum benefits the males of the species. But, they say, this newly discovered behavior makes some sense in light of the worms' unusual life history.

" Most animals can move around in search of a mate, and so should be ready to make the most of any opportunities that present themselves," Griffin explained. "Like many parasites, Steinernema enter their host insect when they are still juvenile and develop inside. A male that finds himself alone cannot leave the insect to search for a mate." Since only juvenile worms invade insects, those solitary males just have to wait until a young mating prospect joins him and grows up. Under these circumstances, she said, a mating partner can't appear suddenly, leaving the male no reason to be sexually mature.

Griffin's team, which included Lemma Ebssa, now at Rutgers University, made the discovery while studying the reproductive behavior of the nematode. They were surprised to find that it took some time before successful mating occurred between a pair of worms placed together.

"Initially, we thought that perhaps the female was unreceptive and/or immature, as this would be the more normal situation in animals," Griffin said. "However, further experiments showed that it was the male that was unready. We then took a closer look and discovered to our great surprise that the reproductive tract of naive males was smaller than that of males that had been with a female for some time, and it contained no sperm."

The researchers think that the signal from females to mature may be chemical in nature, since lone males matured even when females were placed on the other side of a permeable barrier. (The nematodes don't have eyes with which to see.) The researchers don't yet know whether the pheromones that stimulate male maturity are the same as those that sexually attract him to females.

Source: Cell Press

Explore further: Rare new species of plant: Stachys caroliniana

add to favorites email to friend print save as pdf

Related Stories

A battle for ant sperm

Oct 28, 2014

And you thought the sexual battles between people could get weird and fierce? Try ants. In a new study, biologists at the University of Vermont have discovered some queen ants that make sexual bondage into ...

Sex, genes, the Y chromosome and the future of men

Nov 14, 2014

The Y chromosome, that little chain of genes that determines the sex of humans, is not as tough as you might think. In fact, if we look at the Y chromosome over the course of our evolution we've seen it shrink ...

How adult fly testes keep from changing into ovaries

Nov 13, 2014

New research in flies shows how cells in adult reproductive organs maintain their sexual identity. The study, publishing online on November 13 in the Cell Press journal Developmental Cell, also identified a mutation that c ...

Recommended for you

Seychelles poachers go nutty for erotic shaped seed

5 hours ago

Under cover of darkness in the steamy jungles of the Seychelles thieves creep out to harvest the sizeable and valuable nuts of the famous coco de mer palm, and their activities are threatening its long-term ...

Rare new species of plant: Stachys caroliniana

Nov 21, 2014

The exclusive club of explorers who have discovered a rare new species of life isn't restricted to globetrotters traveling to remote locations like the Amazon rainforests, Madagascar or the woodlands of the ...

Mysterious glowworm found in Peruvian rainforest

Nov 21, 2014

(Phys.org) —Wildlife photographer Jeff Cremer has discovered what appears to be a new type of bioluminescent larvae. He told members of the press recently that he was walking near a camp in the Peruvian ...

User comments : 0

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.