|MadSci Network: Zoology|
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
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