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.

Crepidula fornicata: descriptive name or tasteless joke?

The name Crepidula fornicata always elicits giggles.  Understandably.  The last place anyone expects to see rude jokes is in an official Latin name.

The snails themselves are the most abundant and widely recognized slipper snails.  They are originally from the east coast of North America.  But they were introduced into England in the late 19^th century and are now also widely distributed in Europe.  Like all calyptraeids they change sex from male to female.  One unusual thing about Crepidula fornicata is that the animals often stack up one on top of the other. The males, which are smaller, sit on the backs of the females (can you see where this is going?). 

Clusters of Crepidula fornicata attached to a clam shell.

So how does this relate to the name Crepidula fornicata? 

The genus name, Crepidula, is straightforward Latin and refers to a small slipper or sandal.  This name was first applied to slipper shells in 1822 by the great evolutionary biologist and natural historian Jean-Baptiste Lamarck, and has been used every since.   

The species name, fornicata (giggle), which distinguishes this species from other species of Crepidula is even older, and the meaning is not so clear.  Following the system designed by Carl Linnaeus - the originator of the naming system we use today – the species name is usually descriptive.  This helps biologists remember the names of the species:  Crepidula plana is flat; Crucibulum spinosum is spiny; and so forth.

So the serious and rather dry explanation for the name fornicata is that when Linnaeus himself coined the name in 1758 he was referring to the shape of the shell.  Fornicata from the root fornicatus means vaulted or arched. 

Crepidula fornicata "fornicating"

BUT…. Could the name also be a lascivious reference to the animals’ sex lives?

A rude joke would be in character for Linnaeus.  Surprisingly, going against all of our stereotypes of dry old scientists, there are quite a few records of Carl’s sense of humor.  He famously named the blue whale Balaenoptera musculus, which means both “muscular” but also “little mouse".  He pointedly named a useless and obscure weed after one of his critics.  His salty language and focus on the sexual organs of flowers for identification (features that are still useful today), was considered at the time as "too smutty for British ears".  He also named a number of clams and mussels for their resemblance to female genitalia.  Smutty indeed.  And not something most of us would notice when facing a plate of clams with garlic and olive oil.

The original description gives us no clues:  “Oval shell, intact posterior, obliquely curved, concave rear lip.  Habitat to Elba Island.  Differs from the preceding base lateral, white concave shelf.”

I don’t know if the name fornicata reflected Linnaeus’ knowledge of the sex lives of these snails.  It seems unlikely.  At the time samples reaching Europe from the New World were almost exclusively shells.  Sex change in Crepidula was not to be discovered for another 150 years, but perhaps reports of aggregations of small and large animals reached Linnaeus.  Maybe that was all the suggestion he needed.  With his naughty interpretation of so much biology and his propensity to pun, it is quite possible that the name is a clever wordplay on fornicatus meaning arched, and fornicor meaning to fornicate or to prostitute.

Fun Facts About Scientific Names

Parking Lot Ecotourism

Look what we saw from my office window today!

It seems that the two-toed sloths like to forage in that particular tree. Someone told me that sloths especially like the white flowers on these trees, but from here I can’t see any flowers.   I most often see the sloths around 4pm, just after the students leave for the van that takes them back to the city.  Sloths aren’t social but there are usually two together, and I wonder why; are they mother and baby? They look too close in size for that.  Friends? Competitors, each one trying to get to the best leaves first?

For marine biologists it is fantastic and a little bit unusual to be so close to forest animals. Because the island is so small, wildlife from the seasonal dry forest on Naos and Culebra often venture down into the parking lot. And they come close to the office windows. So we can see some nice animals from the comfort of our office chairs. It makes a nice break.

We often see green iguanas sunning themselves on the roofs. It’s a treat to see a large male climbing up the papaya trees around the lab. They feast on the fruit as they ripen, leaving none for us.

Green iguana and papayas

In the early evening it’s common to see armadillos at the edge of the shrubbery. Bats come later to feed on the fruits of the sea almond trees planted around the parking lot. At night they are just a flurry of wings in the dark, but in the morning we find the chewed fruits lying under the trees.

Nine-banded Armadillo

We are also surrounded by numerous smaller animals: lizards, song birds, myriad insects, spiders, scorpions….  Even though we are biologists, few of us stop to observe these less obvious animals.  We keep our heads down as we hurry from the parking lot to our offices in the morning or head home at the end of the day.  But who doesn’t stop to watch a sloth?