2 November, 1997

2 November 97

CONDITION III for all locations.

REGIONAL WEATHER SUMMARY...Low pressure system passing to the north is spreading clouds over the region

TODAY ...Cloudy

Visibility: Unrestricted.

Wind (knots): Norrtheast 15 gusting to 20 becooming southeast this afternoon. High -12C/+10F. Lowest Wind-chill -44C/-47F.

SATURDAY...Sunny.

Visibility: Unrestricted.

Wind (knots): Northeast 15 gusting to 20 becoming Southeast this afternoon. High -15C/+05F. Lowest Wind-chill -42C/-43F.

SCOTT BASE 24HR TEMPERATURE FORECAST

High -17C. Low Tonight -23C

ASTRONOMICAL DATA

Next sunrise in February, 1998

YESTERDAY'S EXTREMES -01 Nov, 1997

Maximum Temperature: -12C/+10F

Minimum Temperature: -21C/-06 F

Peak Wind: 36 Knots

Lowest wind chill: -44C/-47F

I did, indeed, need another day to try to get caught up on my work. Although I worked yesterday until about 12:30 AM I didn't come close to finishing.

Stories filtered down through the grapevine that the Halloween party was a big success but I am unable to give you a first hand account.

On Sunday evenings it is customary for visiting scientists to give lectures for the McMurdo community. These are very popular and are geared for the nonscientist. This evening's lecture was given by Dr. Jim McClintock, a marine biologist from the University of Alabama at Birmingham. He discussed his research in Antarctica and some of the subantarctic islands. Much of his research focuses on chemical ecology. This is mainly about how certain marine organisms produce chemicals which they use in defense or to evade predation.

I found one situation parcticularly intriguing. This involves a mollusk found in the waters of McMurdo called, Clione antarctica, more commonly known as the sea angel. It is a type of snail which has lost its shell. through evolution. The outer mantel has developed into wings which it uses to swim through the water resulting in its classification as a pteropod (wingfoot). Because it is a slow swimmer and has no shell it is quite vulnerable. As a defense it has evolved the ability to produce a compound known as pteroenone. This makes it very distasteful to fish who would eat it.

This in itself is a wonderful story of adaptation, but it gets better. Marine communities commonly contain small swimming invertebrates known as an amphipods. One type of amphipod in McMurdo Sound has evolved a behavior in which it captures a sea angel and attaches it to its back. Dr. McClintock has found that amphipods which are able to do this are not eaten by fish. Over time the evolution of the sea angel and this amphipod have been linked. This is known as coevolution. It is not known if the sea angel is harmed by this relationship. It is known that they appear healthy when examined but it is also known that they are not able to feed while they are prisoners

Things to ponder:

1 It takes quite a lot of energy for amphipods to swim while carrying sea angels on their backs. This added weight means they can only swim about half as fast and therefore must obtain more food. Explain why in spite of the extra expenditure of energy this is a good survival strategy for the amphipod. Normally strategies which require less food have the survival advantage.

2. Form an hypothesis about what you think the amphipod population might be like many years from now if only some of them are capable of capturing sea angels. Why?

3. Brainstorm and make a list of other examples of coevolution.

4. Form an hypothesis about the relationship between the sea angel and the amphipod concerning the captive sea angel. How would you explain the fact it appears healthy yet is unable to feed?

5. Organisms which have coevolved form relationships known as symbiosis. Mutualism, commensalism, and parasitism are different categories of symbiosis. Which type of symbiosis best explains the relationship between the sea angel and the amphipod? Explain your reasons.