Congratulations Kecia!

Today is a big day for the CollinLab. 

Kecia Kerr, the first PhD student from the CollinLab successfully defended her dissertation.  After 5 years of hard work and intensive questioning on her research, Kecia will be awarded a PhD from the NEO Program at McGill University.   It’s a great accomplishment and her project has produced some cool results.

Working with fiddler crabs, Kecia focused on how changes in temperature influence the timing of reproduction.  These crabs are good mothers and after brooding their eggs, they time hatching to occur when predation risk is lowest for the hatching larvae.  In most places around the world female crabs release their tiny larvae at night on the days with the biggest tides. We think this is because predatory fish can’t see the larvae very well at night.  And, that during large tides the water sucks the larvae offshore to safer areas; away from predators that are more common in the shallow water.

Climate change is expected to alter the seasonal upwelling of cold water that normally happens between January and May here in Panama.  It is likely that the intensity and also the frequency of these events will increase.  Kecia wanted to know if the crabs will be able to adjust to the more variable temperatures we expect to have in the future.

Changes in temperature can alter the rate of development.  So how can the crabs ensure that their larvae hatch at the right time?  Kecia found that different species do different things.  One species can predict the temperatures that they will experience while they brood.  They use their experience of current temperatures to adjust when they mate and lay their eggs.  Females of the other species are not flexible in when they mate or lay eggs.  Instead these crabs can adjust the temperature experienced by their eggs:  The females move up and down in their burrows finding the right temperatures to keep their eggs on track to hatch on time.

Even with these strategies the crabs sometimes make errors and release their larvae on the wrong days.  How these errors effect the survival of the crabs is a question Kecia hopes to answer in the future.

Kecia’s first dissertation chapter is already published.  You can read it in Marine Ecology Progress Series here:  http://www.int-res.com/articles/feature/m459p001.pdf

Watch these videos to get an idea of what Kecia’s fieldwork is like.

http://www.youtube.com/watch?v=H0sCjgZ5y9A&feature=plcp

http://www.youtube.com/watch?v=hIsy0ZoyxCU&feature=plcp

Failed papaya crop

Almost everywhere you go in Panama you see papaya trees, laden with fruit growing, around the houses.  There are trees dripping with fruit in the parking lot at work.  We pass them walking the narrow trails to reach the beaches where we work.  We see them squeezed in between houses in the city.

I’ve been trying to grow some of my own.  And I’ve discovered that birds feed on them.  Not on the fruit but on the trees themselves.  It seems that for the second year in a row I won’t have much of a harvest, but I’ve seen some interesting birds and their behavior. 

Few birds commonly consume leaves.  But these grey-headed chachalacas are generally herbivorous and seem to enjoy papaya leaves.

Another day I got a clear view of why there are so many flowers but so few fruit. This collared aracari is tossing back the flowers (literally)

Discovering the Newest Calyptraeid Species

It’s official.  This week the newest calyptraeid species officially got a name, Crepipatella occulta.   This gives me a great excuse to talk about the process of discovering and describing new species... And just how long it can take.

The Discovery

It all started several years ago when my friend David Veliz was a student in Coquimbo, Chile.  His thesis project was to use allozymes (a genetic technique) to see how closely related the calyptraeid species in Coquimbo are.  Two of these were Crepipatella dilatata and Crepipatella fecunda.  But at that time they were placed in the genus Crepidula.  Anyway, he kept getting very strange results for these two species.  Results his advisor told him were impossible.

Now, it is very difficult to distinguish C. fecunda from C. dilatata from the adults -  they are very similar in size, shape, and color -  but they have different development and if they are brooding we can distinguish them on how the embryos look. C. fecunda makes lots of small eggs that all develop into feeding larvae. C. dilatata makes many small eggs - about the same size as C. dilatata - but only a few of these even begin to develop.  The few embryos that develop eat the eggs that don’t develop -called nurse eggs- and grow into juveniles before they hatch from the capsule.  David knew this and carefully placed all of the animals with lots of small developing embryos into the C. fecunda sample and all of the animals with large embryos mixed with a few round yolky eggs into the C. dilatata sample.

So what could have gone wrong?

Crepipatella dilatata. The normal
embryo looks like a small snail with
a coiled shell but the nurse eggs are
show no structure. They are simply
balls of yolk

Crepipatella occulta. In this species
The nurse eggs begin to develop and
you can see that they are blobs of
yolk surrounded by more transparent
tissue.

David in 1999 with his new species

When he went back to collect more samples he found that some of the adults had eggs that did not really fit either of these types. Some snails had broods where normal developing embryos were mixed with embryos that had begun to develop but had arrested development.  These nurse eggs were not perfectly round like the nurse eggs from C. dilatata, they were balls of cells covered with a thin epithelium and sometimes even had cilia beating on the outside.  He found that early in development the broods looked just like C. fecunda with all the eggs developing in the same way.  But later in development when they had eaten all of the nurse eggs they look just like C. dilatata. 

When these 3 species were separated his genetic results made perfect sense and showed that the third species is genetically distinct. 

About this time, I was a student traveling around collecting calyptreaid snails in order to sequence their DNA to figure out their relationships.  I visited Coquimbo where David helped me collect samples of all 3 Crepipatella species, and my DNA data verified his results .

These data showed clearly that the third species is different from C. dilatata and C. fecunda BUT it didn’t tell us if it was officially a new species - that is one that has never been described and named.

In the next post we will describe how we demonstrated that this third species was new and needed a name.

For more information about these species and to see the papers we've published on this work:

Veliz et al. 2003.  Developmental and genetic evidence for the existence of three morphologically cryptic species of Crepidula in northern Chile. Marine Biology 143: 131–142.

Collin et al. 2007. Molecular phylogenetic and embryological evidence that feeding larvae have been reacquired in a marine gastropod.  Biological Bulletin  212:  83-92.

 

Veliz et al. 2012.  Crepipatella occulta sp. nov. (Gastropoda : Calyptraeidae), a morphologically cryptic species from northern Chile.  Molluscan Research.  32:  145-153.

Here are a few more photos of the development of our new species, taken by Matt Starr.