Friday, May 5, 2006
When and where found: Copepods are extremely common in both salt water and freshwater. Cyclops is one of the freshwater genera and can be found near the edges of ponds, lakes, and ditches. The specimen in the photo was scooped up in a bucket of pond water from a shallow pool in the Fox Hill conservation land across the road from Kimball Farms ice cream stand on March 28. Even though they are tiny, they are relatively easy to spot if you set a glass pie plate on a sheet of white paper, pour in pond water to a depth of about a quarter inch, and then scan the area for small moving things. You will be able to tell the female Cyclops from the other tiny animals by the two darkish-colored eggs sacs. Then you can scoop her up in a teaspoon, put her in a smaller dish and look at her with a microscope. If you blot up most of the water with a paper towel and leave her just a little droplet, she will remain in your field of view. The photo was taken at 40x magnification on my dissecting microscope.
Characteristics: Cyclops is small — anywhere from one to two millimeters long. The most conspicuous feature is the large pair of egg sacs on the female. The egg sacs are a darker color than the rest of the creature. The antennae are prominent and hairy. There are two sets of tail bristles of equal length. The eye is a problem. Mine looked like it had the single eye of its namesake but one of my sources (Guide to Microlife) says that there are really two eye spots which appear as one under low magnification. I don't have a higher powered microscope or other sources to confirm this. In addition to the slow oar-footed means of locomotion, Cyclops can also move in fast jerky bursts using its seven pairs of legs. This jerky movement can help you spot it when scanning a dish of pond water with the naked eye. Ostracods (or seed shrimp) are about the same size as Cyclops and also move in bursts, but they are more oval and they don't have external egg sacs.
Life cycle: The eggs hatch into larvae which molt as they grow, going through five or six stages. The larvae are smaller and rounder than the adults and they have fewer legs. They reach maturity in three to four weeks depending on the temperature of the water. The adults are predators and are themselves important prey in the food chain. Copepods can survive drought by forming cysts or cocoons and so are able to inhabit vernal pools.
Word for the day: Nauplius is the term for the first larval stage of many crustaceans. Cyclops eggs hatch into very distinctive nauplius larvae. As the salamander larvae often say, "Oh please, not nauplius sashimi for dinner again!"
References: Borror and DeLong, Introduction to the Study of Insects; Mike Morgan's article at www.microscopy-uk.org/mag/articles/cyclops.html; Leo P. Kenney and Matthew R. Byrne, A Field Guide to the Animals of Vernal Pools; Kenneth G. Rainis and Bruce J. Russell, Guide to Microlife; George K. Reid, Golden Guide Pond Life (This guide covers flora from algae to woody plants and trees, and fauna from protozoa to birds and mammals.)
Feel free to write the Biodiversity Corner on any living thing large or small that interests you. The only requirements are that it exists in the wild and was seen in Carlisle. Send a note to Kay Fairweather at firstname.lastname@example.org
© 2006 The Carlisle Mosquito