Re: How are limpets adapted on a rocky and sheltered shore.

Greetings,
The following is an article taken from the site,
http://www.nps.gov/cabr/tide.html
It provides an interesting answer for the different sizes of limpets that occur
in the Cabrillow tide pools.


The Cabrillo tidepools are currently being studied to access the                       
impact human visitors have on them. Initial results do seem to
indicate that humans are contributing substantially to the decline
of many species. The National Park Service, however, believes
that we are capable of resolving the problems that face the
inter-tidal animal and plant life, so that we may, hopefully, undo
some of the damage and help these species survive.

For example, here is the owl limpet's plight...

Owl limpets are still fairly common on the rocks of Cabrillo's
tidepools. But so too were abalone at one time. Then people
discovered how good abalone taste and they began
disappearing. Now it is nearly impossible to find even a small
abalone at Cabrillo. Like abalone before them, today Owl
limpets may be in danger of disappearing simply because they
taste good.

In the 1970's, owl limpets that lived in Cabrillo's tidepools were
abundant and averaged 50.25mm across in size. Meanwhile,
only four miles up the coast at Sunset Cliffs, owl limpets at that
time averaged only 30.61mm. The older, larger, owl limpets at
Sunset Cliffs were apparently being gathered for human
consumption. At Cabrillo National Monument, however, no
collecting of any kind is allowed, so the animals are able to
grow older and bigger.

Here is a curious and worrisome twist: owl limpets are
hermaphroditic -- in other words they are both male and female
during their life span. In the case of owl limpets they are male
when they are young (and small), and female when they get
older (and larger). This is important because it may be that owl
limpets are not growing large enough to fulfill the female role of
reproduction at Sunset Cliffs. At Cabrillo, however, the
tidepools are closely monitored and owl limpets are able to
grow to a large, female, size.

It is possible that protected areas like the Cabrillo tidepools
serve an important function as breeding grounds for owl limpets
and other commercially important species in the area. Most
limpets hatch from eggs into a larval form that drifts with the
ocean's currents to their eventual homes. Perhaps many owl
limpets spawned (hatched) at Cabrillo are swimming away and
replenishing other areas of the coastline with young owl limpets.
If this speculation is the case, then it is very important that we
protect and preserve areas like the Cabrillo tidepools.

A recent study, however, suggests that even the Cabrillo owl
limpet population is in danger. Between 1990 and 1995, owl
limpet numbers declined an overall 23%, and individual animals
were found to average only 45mm in length (5.25mm less than
they were twenty years ago). Park rangers do discover people
collecting illegally in the park, and are worried that this
poaching may be causing the decline. The park will be
increasing its park ranger and volunteer presence in the
tidepools, and park rangers take a strong stance on enforcing
the No Collecting rules in the park.

      Thanks for sending in a question to MadSci Network

June Wingert
Research Associate
Lexicon Genetics