14 Aug 2007

Invasion of the Sideswimmers

Dear Blue Lobster:

I was was in a boat on Lake Erie and I threw a bucket down on a 150ft. of rope and dredged for a while. I wanted to see if I could find any Zebra Mussels. I found some, as well as a strange white crustacean that looks like a cross between a shrimp and a water flea. What the heck! I had no idea anything like that lived in the lake. I will never go swimming here again. What was it?


Dear Gentle Sir:

What you encountered was Gammarus tigrinus, commonly known as the Sideswimmer. This species is native to the North Atlantic Coast but has been introduced to the Great Lakes in the last decade in a controversial effort to limit the Zebra Mussel population.

Instead, the Sideswimmers have joined the mussel in the benthic zone of the lake, feeding upon valuable plankton. Fish populations, such as the small mouth bass, are in a freefall thanks to this meddling by scientists.

One positive aspect of the infestation of this invasive species is that the lake, heavily polluted by post-World War II industry and subsequently cleaned up by the Zebra Mussel in the Eighties, is now even more pristine. Thanks to the Sideswimmer, you can now enjoy a glass of water straight out of the lake.

Measures to control the Sideswimmer population are in order. A genetically engineered virus is being tested that would render adult Sideswimmers infertile. Wildlife officials are also stocking a Bluegill/Pumpkinseed hybrid (Lepomis gibbosus × macrochirus) in hopes it will eat the Sideswimmer.

As these silent underwater wars go on, rest assured the lake is still safe to swim in. These tiny creatures generally don't come to shore, instead preferring the dark silence of the bottom. Perhaps you'd like to take the Sideswimmer home and study them, along the some Zebra Mussels, in your aquarium!

8 Aug 2007

What Makes a Rusty Crayfish Red?

Dear Blue Lobster:

i caught a rusty crayfish and my cousin says its red because it is in hot water. i think it's red because its parents were red. my paw paw says it's because god made it that way. who's right? what makes a rusty crayfish red?


Dear Gentle Sir:

The Rusty Crayfish (Orconectes rusticus) is red because that is its natural colour morph; that is, it is red due to its genetics just as your skin colour was inherited from your parents and their parents, etc. This is called a heritable trait.

Orconectes rusticus became red, however, because its ancestor habited areas with high concentrations of ferrous oxide, commonly known as rust, in the water. Because of this the Orconectes expressed red and orange colors and since they matched the environment better these colour morphs eventually became endemic to their population. This resulted in the speciation of rusticus.

Today you can hunt Rusty crayfish with a metal detector thanks to their high iron content and doctors often prescribe the species to anaemic women during pregnancy as well. One may even find carnival-goers during the Mardi Gras dressed in costumes made of scrap metal painted red replete with refrigerator magnets honouring bebe rouillé, the little red bug.

1 Aug 2007

Can Crayfish Get Goitre?

Dear Blue Lobster:

I can see the need for iodine in salt water or brackish water animals, but fresh water crays have no natural source of iodine. Has anyone seen any studies that prove it is beneficial?

In the shrimp world we've established that in small doses it dooesn't hurt, but long term keeping in side by side tanks have shown no benifit at all.


Dear Gentle Sir:

In marine environments, the level of dissolved minerals generally satisfies a crustacean's need for iodine. Fresh water, however, lacks the dissolved minerals and crayfish, as well as other crustaceans, may experience iodine deficiency. This can result in a number of disorders.

Goitre, as you mentioned, is one such consequence of hypoiodinism. In crays this manifests itself as a large goiter just the under the head segment, often making the cray look as if its head were about to explode. Native North American tribes would avod eating such specimens, as their flesh was loose and sickly; animals too avoid bulbous-headed crays.

Sluggishness and mental retardation are other symptoms. If your cray is acting slow, weak, or generally lethargic, lack of iodine may be the cause. Likewise, a cray that eats its own appendages or feces may suffer from iodine deficiency.

Some crays have developed numerous methods to obtain it in other ways. One tropical species combs the brackish deltas of the Amazon and its tributaries for kelp detritus with antennas adapted to detect iodine molecules from up to eight kilometers (five miles) away.

If your cray is not lucky enough to have these adaptations, there are ways to introduce iodine to your aquarium. The simplest way is to add iodized table salt. Add one ounce a week until symptoms subside.

If your cray is sensitive to salt, add pure iodine crystals to the water. To obtain these, empty a bottle of iodine tincture onto a flat plastic container and leave in the sun. When the alcohol and water have evaporated, use a straight razor to scrape the remaining crystals into your cray's tank. Stop when the water begins to take a lavender hue.