Pond Study Day at Alder Creek
1Mr. Ewan Achterberg's eighth grade class spent a pond study day at the Alder Creek Nature Center. Students swept dip nets through the cattails and put drops of pond water under microscopes. Paloma Szabo found water fleas, green strands of algae and a few mosquito larvae wriggling head down. Next to the wild pond is a small display pond full of koi, with orange, red, white and black patches.
2A guide explained that koi are a colorful kind of common carp. Wild carp are mostly a dull olive-bronze. About 200 years ago, farmers in Japan raised carp in ponds as food and noticed a few fish with red or white patches. They kept those fish and bred them, and over many generations the bright patterns of today's koi appeared. A local koi club still breeds koi and gives young fish to the nature center.
3In 2022 the club raised 200 young koi from its usual parent fish. At six months old, each fish was photographed and scored by the share of its skin covered in red patches. For the next round, the club chose 8 parents only from fish that scored 60% or more. In 2024, it raised 200 young from those parents in the same pond, on the same food, and scored them the same way at the same age.
4After lunch, Dr. Nnamdi Valcourt from the county mosquito control lab spoke to the class. The yellow fever mosquito lays its eggs in small pools of water such as flowerpot saucers and old tires. Only females bite, and they can spread viruses such as dengue and Zika. Male mosquitoes do not bite. The county is testing an engineered strain of this mosquito. Its males carry a gene that scientists built from bacterial and viral DNA. Daughters that inherit the gene die as larvae, while sons survive. The strain also carries a marker gene from a coral that makes larvae glow red under a special microscope light.
5To check the strain, the lab set up two cages, each with 50 regular females. Cage A also got 50 regular males, and Cage B got 50 engineered males. The lab raised 400 eggs from each cage in trays of water and counted the larvae and the adults that came out. Paloma's group looked at the larvae under the special light.