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Project Lab 

January 28, 2014

Specimen of the week: Rattus norvegicus

The last few weeks up in the Project Lab, I have been preparing some study skins and skeletons of Rattus norvegicus.  But before you wonder where these specimens were found and call the exterminator, I should specify that these are domestic rats, which are slightly different from the rat one may imagine hiding out in the alley.

So what is a Rattus norvegicus?  Its most common names include Brown Rat, Norway Rat and Hanover Rat.  This species is thought to have originated from Asia, and is now found on almost every continent except Antarctica.  This prolific species has also given rise to the “laboratory rat” and also our furry, friendly domesticated house pets, the “fancy rat.”  Although these fancy rats are still considered the same species, Rattus norvegicus, they can look quite distinct from the same species found in the wild.

 

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The main and most conspicuous difference between fancy rats and wild rats is color.  Fancy rats can exhibit a wide variety of colors from white to black, and many shades of brown.  This color variation is extremely rare in wild populations and would most likely be a detrimental feature if exhibited frequently – a white rat is much easier to spot by potential predators!  There are also some temperament differences in domesticated rats that make them more sociable towards their pet guardians.

 

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But why would we have these domesticated breeds in our collections?  If you’ve ever walked through the museum, you may have noticed a small display of domestic dog breed skulls hanging on the wall near Tusher African hall.  Although we may think of dogs as separate breeds, they are all considered to belong to one species, Canis familiaris.  This may bring up the question then, what is a species?  There are many definitions. One definition, perhaps the best known, suggests that a species is a group of organisms that can interbreed and create fertile offspring.  So most dog breeds have arisen with artificial selection, and once established can reproduce on their own, which is also the case in the domesticated fancy rats.  While it may not seem as important to keep specimens of these domesticated animals, they can still give researchers insight into how species have changed over time. Whether it is a morphological difference like pelage (fur) color, size, or shape, or whether it is a genetic variation, these specimens can help researchers piece together the puzzle of a species’ history.

 

Codie Otte

Curatorial Assistant and Specimen Preparator

Ornithology & Mammalogy Department


Filed under: Uncategorized — project_lab @ 11:00 am

January 15, 2014

Marsh Birds

This week, I prepared a study skin of a wetland bird called a Black-crowned Night-Heron (Nycticorax nycticorax), the most widespread heron species in the world. There are 64 species in the heron family (Ardeidae), which also includes egrets and bitterns.  Black-crowned Night-Herons forage for fish, amphibians, insects, and other types of food during the evening, avoiding competition with the other heron species that use the same wetlands during the day. Night-Herons nest in colonies with other heron and egret species in trees or other vegetation, usually over water. Adults and juveniles look drastically different, with adults sporting long white ornamental plumes on their heads.

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These birds, like most bird species, will raise any chick in its nest, meaning that they are unable to distinguish between their own biological offspring and those of other parents. In a previous blog, Codie talked about brood parasitism, which occurs when a bird lays its eggs in another bird’s nest, leaving that parent to raise offspring that aren’t biologically theirs. This can be done by more species than the commonly known Cowbirds and Cuckoos! By not being able to distinguish between chicks in their nest, Night-Herons can become victim to this kind of brood parasitism, and have been documented to be parasitized by Black-headed ducks. There is, however, another kind of brood parasitism called “conspecific brood parasitism.” This strategy is when a bird lays its eggs in the nest of a bird of the same species. This occurs in another marsh bird species, the American Coot (Fulica Americana), which has a high rate of conspecific brood parasitism. Females will lay their eggs in other females’ nests, potentially increasing their own reproductive success. Unlike Night-Herons, however, Coots have developed strategies to recognize their own young and reject the young of competing parents.

 

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The strategies that different species evolve to make them as biologically successful as possible are fascinating, from brood parasitism to elaborate dances and plumages, and can be seen in all types of birds. If you’re interested in seeing Black-crowned Night-Herons in San Francisco, you can find them year-round in different wetland areas such as the lakes in Golden Gate Park as well as harbors and piers.

 

Laura Wilkinson

Curatorial Assistant & Specimen Preparator

Ornithology & Mammalogy


Filed under: Uncategorized — project_lab @ 11:20 am

January 5, 2014

Woah, look at that spider!

 

spider on scope

 

Due to the holidays, I’ve spent extra time in the Project Lab over the last few weeks. One thing that has really surprised me lately is the reaction that a certain member of our lab gets from visitors.  You see, Vic, our Entomology imaging specialist, has a couple of plush spiders at our Big Kahuna imaging station.  Over the last few weeks, I’ve heard, “woah, look at that spider!” more times than I can count (yes, we can hear you through the glass!).  I recognize that some folks are teasing each other about the giant spider toy, but I also get the impression that some guests have mistaken this spider for a real animal. I’m a bit shocked that so many people seem to think that this is a real spider.  So, this week I decided to set the record straight-sorry folks, but it’s a stuffed animal (not of the taxidermy variety).

 

 

spider puppet

 

Now, I’d like to arm you with some spider facts to help you from getting tricked by big fake spiders in the future (which will be particularly useful during Halloween time)-

 

Our spider puppet is humongous!   I took a ruler to it, and the body, not including the legs, is about 6 inches long and 3.5 inches wide.  If you include the legs, the puppet is about 17” wide!   So how large can the largest real spider get?  The largest spiders in the world are the Goliath Birdeater, sometimes known as the bird-eating spider, and the Giant Huntsman Spider.   Here is how they measure up to our spider puppet:

 

Project Lab spider puppet Goliath birdeater Giant Huntsman
Body length  6” (15.2)  4.7” (11.9 cm)  1.8” (4.6cm)
Leg span  17” (43.2cm)  11” (28cm)  12” (30cm)

 

 

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So, as far as we know, there are no real spiders out there that are as big as our Project Lab puppet spider.

 

Now, of course, if we had a live spider in the Project Lab, we would keep it in a terrarium, not sitting on top of a microscope.   As for preserved spiders, typically, spiders are not preserved as dry specimens (unlike other arthropods like beetles or butterflies).  The reason spider specimens are not stored dry is because they are quite soft-bodied, even though they have an exoskeleton.  Dry spiders shrivel up and are not useful for research purposes (nor do they look all that good).    Occasionally, you may see framed dry spiders available for sale as decorations or educational displays, but this is not the case for research.  Instead, spiders are kept in alcohol as wet specimens.  This prevents spiders from drying out and shriveling up, and allows researchers to be able to bend and manipulate the legs.

 

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spider puppet 2

So the next time you pass by the Project Lab, feel free to say hi to the spider puppet.  I’m not sure if this spider has a name yet, I’ll ask Vic and get back to you!

 

Vanessa Knutson

Project Lab Coordinator


Filed under: Uncategorized — project_lab @ 12:48 pm

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