Re: How are planaria affected by substances of different pHs

First, I have to admit that I have not been involved in research in planaria and therefore am not a true expert on these organisms.

Planarians are found in marine and terrestrial environments and belong to the phylum Platyhelminthes and the class Turbellaria. This includes many free-living flatworms and a few parasitic organisms. In general, the free- living flatworms are carnivorous. They can be lured to pieces of beef or liver placed in springs or streams. They naturally prey on small live animals or scavenge on larger dead ones. A few scrape algal films from rocks or eat other plant material. Flatworms can be found in very large numbers in marine and fresh waters. Most planarians are rather small, 1-2 cm long, but some terrestrial species can be as large as 60 cm. Free- living organisms must search for food. Thus, they are exposed to many hazards in the environement. Flatworms will be preyed upon by larger animals. Some flatworms are parasites and live in the guts of animals. Several are human pathogens, like the tapeworm.

Flatworms have sensory organs that allow them to detect food, light, and water currents. I don't have any specific information about pH effects. So, I don't know whether they respond to pH changes. It is clear that flatworms will have a pH which is optimum for their growth. It is likely a little different for each species, but should fall in a range near neutral pH (perhaps pH 5-9). In the extremes of pH, the organism will likely be killed or injured. Strong acids and bases can disrupt living systems in a number of ways, including: uncoupling energy transduction systems, inhibiting ion transport systems, denaturing proteins, displacing metal ions on membranes or cell walls, inhibiting enzyme activities. These can lead to cell lysis and death.

As I said, this is a bit out my wheelhouse. I picked up some of this information from a book: Living Invertebrates, edited by Pearse, Pearse, Buchsbaum and Buchsbaum, published by Blackwell Scientific Publications, Palo Alto, in 1987. I hope that the information I provide here is helpful. If you have further questions, I can try to answer them as well.

Cheers,

Dr. Mark.
schneegurt.1@nd.edu