Category Archives: Invertebrates

Water flea: small critter, big genome

Daphnia pulex (water flea) with a brood of genetically identical future offspring.

Daphnia pulex (water flea) with a brood of genetically identical future offspring. (Photo/Paul D.N. Hebert, University of Guelph)

In an interesting science factoid of the week, researchers at the University of Guelph have just found the animal with the most genes.

Ringing in at a whopping 31,000 genes, the winner is a near-microscopic crustacean called daphnia, or water flea. In case you’re wondering, humans tally a mere 23,000, about 8,000 less than this little aquatic critter.

Daphnia‘s high gene number is largely because its genes are multiplying, by creating copies at a higher rate than other species,” said project leader and CGB genomics director John Colbourne in a press release. “We estimate a rate that is three times greater than those of other invertebrates and 30 percent greater than that of humans.”

So let that be a lesson. Just because you’re little, doesn’t mean you can’t be big at something.

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Bad Ladybug

Different types of Harlequin ladybug, a rapidly spreading invasive pest. ©Entomart

Different types of Harlequin ladybug, a rapidly spreading invasive pest. ©Entomart

Ladybugs, once the championed protectors of backyard gardens, are showing spots of a less flattering color, and their public image looks like it could be taking an even bigger turn for the worse. A new study has found that invasive Harlequin ladybugs crossbreeding with a species of flightless ladybugs are creating a super strain of a buggy pest.

In recent years, ladybugs have taken their voracious appetites around the world, and they don’t just gobble up target insects. Couple this with plagues of ladybugs infesting homes, and you’ve got an unseemly problem on your hands.

To fight their spread, flightless ladybugs were released as a biological control agent. The idea being that the walk-only ladybugs wouldn’t spread as far as quick. Harlequin’s aren’t to be put off it would seem. The two types of ladybugs can hybridize, giving rise to offspring that are larger, faster-growing, and generally more robust than either of its parent species. Preliminary research suggests that the cross-bred young are even better-equipped to deal with starvation.

The findings by BenoÎt Facon of UMR Centre de Biologie et de Gestion des Populations in Cedex, France, and his colleagues are just a beginning. Researchers want to test multiple generations of hybrid and subject them to different conditions to unravel the magnitude of the Harlequin ladybug dilemma.

You can read more about their discoveries in the current issue of Evolutionary Applications.


Changing Chesapeake Bay acidity endangers oysters

New research shows that the shell growth of Crassostrea virginica from Chesapeake Bay could be compromised by current levels of acidity in some Bay waters. (Photo/Chris Kelly, UMCES Horn Point Laboratory)

Growing up at the mouth of the Lynnhaven River in Virginia, where the river meets the Chesapeake Bay and the bay meets the ocean, I can’t tell you how many mornings I woke up and looked out my window to see neighbors wading in rubber boots, harvesting oysters from the beds just off our riverbank. For some, like my neighbors, oysters were a way to connect with the land and make a little extra dough. For others it was their livelihood. The act was something that just was. It never occurred to me that the oysters could one day be gone.

That’s why I was especially alarmed to read this new report from the University of Maryland Center for Environmental Sciences. Rising acidity levels in the Chesapeake Bay are making it harder for oysters to grow their shells. I’ve heard the news before that rising ocean acidity from sources such as carbon dioxide can spell disaster for marine wildlife, but this new study shows that acidity is rising faster in the Chesapeake Bay than in the ocean and having a measurable impact on Bay wildlife.

“With oyster populations already at historically low levels, increasingly acidic waters are yet another stressor limiting the recovery of the Bay’s oyster populations,” said marine biologist Dr. Roger Newell of the UMCES Horn Point Laboratory in a press release.

But don’t turn around to blame climate change just yet. The story is a bit more nuanced than that, though the source of the problem still has to do with us. In the saltier areas of the bay, the acidity is going up, leading to thin shell growth that makes oysters more vulnerable to predators, including crabs. But in more freshwater portions of the Bay, acidity is actually going down, said the study, which looked at more than 20 years of historical water quality data from the Bay.

The difference seems to be not atmospheric carbon dioxide, but the base of the food chain. In freshwater areas along the upper Chesapeake, sewage and agricultural runoff cause phytoplankton blooms, which consume carbon dioxide and lower acidity, said the study. Sounds good at this point right? Here’s the catch. As phytoplankton drift through the Bay, they are eaten by animals and other bacteria, releasing the carbon dioxide that the plankton so diligently consumed in the first place. This carbon dioxide lingers in the water, leading to spikes in acidity in the saltier regions of the Bay near the ocean.

“While these variations in acidity may improve conditions for shellfish in some areas, they may also magnify detrimental impacts in others,” said lead author Dr. George Waldbusser of Oregon State University in a press release. “What our study indicates is there may be an important shifting baseline and without better measurements we will fail to fully understand impacts on estuarine biota.”

Beyond the science itself, this study highlights how connected and varied our environment is. It lays out a pathway of human-induced consequences to an ecosystem, and teaches that we need to look beyond one-to-one cause and effect. Erin Voigt, an undergraduate student who worked on the study puts it well. “The complex response of oyster shell formation to temperature, salinity, and acidity highlights the need to understand how the entire ecosystem is changing, not just acidity,” she said.

And that ecosystem includes us.

You can view the article online in the journal Estuaries and Coasts.


Saving snails: an invasive species becomes an unlikely hero

A land snail (Photo/ Petr Kratochvil)

Now, I know snails don’t come with the same poster-child charisma factor of more fuzzy, wide-eyed creatures  like pandas or baby tigers. But I hope you’ll imagine a tiny, high-pitched, “Help me!” issuing from the leaf litter at your feet, and stick with these little guys for a minute.

With that said, I’d like to tell you a story of a rat, a snail and a tree. They all live on the tiny island of Anijima, one of several in a chain of islands off the southeastern coast of Japan. The snail is critically endangered. The rat and tree are invasive species. You know those bullies of the natural world, the unwelcome visitors, the home wreckers of entire ecosystems. But before you go, “Oh here comes another invasive species story,” here’s the kicker – one of these encroachers, the tree, is actually in a sense the hero of this story, buying time for the snail and those trying to save it. The study, published online in the journal Conservation Biology, offers conservationists a new framework for restoring native ecosystems.

Anijima is part of the Ogasawara Island chain, a remote group of islands off Japan nominated for World Heritage listing. It’s also snail central. These islands are home to more than 100 species of land snail, 94 percent of which are endemic to those islands. Many of the snails have disappeared over the years, thanks in part to habitat loss and introduced predators.

Anijima was the exception. No one has lived there since the 1830s, and until recently, the environment looked much like it did 100 years ago. But a plant, the Casuarina tree has taken over the mid-western part of the island, converting natural forestland into a monoculture of dry coniferous forest. This delivered a significant blow to the land snails, as the snail’s home was turned into less ideal living quarters. Another blow came with the introduction of black rats in the 1930s. These voracious predators, gobble up the slow-movers, and since about 2006, have enjoyed an unprecedented population boom on the island, likely due to the eradication of goats – a competitor for food – and of feral cats – the rat’s main predator. In short, things weren’t looking good for the snails.

One might think, “Well, if you want to save the snails, just go in there and clear out the invasives.” But not all invasive species are created equal, and one scientist, Satoshi Chiba, with Tohuku University in Japan, has figured out that the Casuarina tree is actually helping the snail weather the rat boom.

Chiba looked specifically at the Ogasawarana genus of snails, a critically endangered group of snails considered a “natural monument” by the Japanese government. They are the only group of snails on the island still living on native vegetation on the island. Chiba surveyed plots in both Casuarina-laden habitat and native habitat, clearing sites of leaf litter, counting and identifying snail species and then returning everything to its place. Chiba also checked for rat carnage, and found that while initially, the tree causes a decline in snail populations, once the rat population went crazy, the Casuarina tree actually provided the snail with a better refuge from the predator than the snail’s native habitat.

The ground litter in the Casuarina habitat is deeper and denser than the snails’ natural environment. Black rats like to forage at the surface, and thus, the snails stand a better chance of avoiding a rat’s tooth and claw in the debris of a Casuarina forest.

The lesson here is not that an invasive species is necessarily good, but that there is an order to things when it comes to restoring an environment impacted by multiple non-native species. For Anijima Island, and the Ogasawarana snails, if they are to be saved, it’s likely that the black rats need to go before the invasive trees.

So, do you care a little more about a tiny mollusk? I don’t know, but at the very least, the story has a rich history, and just think how many other species suffering from a similar tale this study could help.


Lady bug swarm turns Green Mountain red

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Lady bugs unite! When a friend of mine posted some photos she took while on a hike on Boulder’s Green Mountain, I couldn’t believe my eyes. I saw entire tree trunks covered in red. The red was lady bugs, a mass gathering of a gardener’s best friend, as they search for mates and prepare to hibernate for the winter. Now this was something I had to see for myself.

Of course, not everyone can make the hike to Green Mountain, but hopefully you can live a little vicariously through this slide show, and learn a little something new about this “cuter” member of bug-dom.

There are more than 400 species of lady bugs, (or as they’re more officially known ladybird beetles), in North America. This year has been an unusual one for lots of natural phenomena in Colorado — a wet, cool summer has led to an endless green summer and multitudes of wildflowers — and this year’s lady bug gathering is no exception. Boulder Open Space and Mountain Parks estimates that this could be a record-setting year for the annual swarm.

Besides the slideshow, I’ve made a little list of interesting lady bug facts you might not know.

  • They’re cannibals.
    • at least during their larval stage. Researchers recently discovered lady bug babies hatch and eat their siblings. Don’t get too disillusioned. They grow out of it.
  • They don’t change their spots.
    • Some people think you can tell the beetle’s age by the number of its spots, but according to the Boulder Open Space and Mountain Parks, you keep what you’re born with when it comes to the dots.
  • They “play dead.”
    • If an adult ladybug feels threatened it will fall down and “die,” or let off a foul yellow ooze from its leg joints that most animals won’t want to eat, (University of Arizona)

Bait fisheries drive decline of bird species

(Photo/Andrew Easton, 2004)

(Photo/Andrew Easton, 2004)

Every year the horseshoe crabs gather to spawn, releasing thousands of eggs along the Delaware Bay coast. And with timing perfected by evolution, red knots, a bird enduring one of the most impressive yearly migrations from the Arctic to the Tierra del Fuego, arrive just in time to gorge on the eggs of the horseshoe crab. It is a vital stop on the “peeps'” spring migration. But the crabs and their eggs are disappearing, a loss with dire consequences for the little birds.

Red knot populations have fallen more than 75 percent in recent years, and new research published in this month’s issue of Bioscience reveals that Red knots can thank the bait fisheries for their hungry stomachs. Within half a decade the fisheries harvesting horseshoe crabs grew 20-fold, gobbling up more than 2 million crabs a year and effectively eliminating 90 percent of the eggs that red knots rely upon to survive their almost 19,000 mile migration.

But this research is not just a blame game for the fisheries. A coalition of scientists worked together on this study to help draft recommendations for the adaptive management of the bait fisheries that could help all three groups survive.


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