Crepidula Fornicata

We've got two new Ocean Inspired Donors Choose projects that have been funded in the Oceans in the Classroom Challenge! The first one that was funded on Thursday was the awesome Invertebrates in my Tank project that will provide lots of kids with the opportunity to explore one of our favorite subjects: marine inverts!

The Inverts in my Tank card is the 6 of Spades — The Slipper Snail, Crepidula fornicata.

Classification for the Atlantic Slippersnail

Kingdom

Animalia

Phylum

Mollusca

Class

Gastropoda

Order

Littorinimorpha

Family

Calyptraeidae

Genus

Crepidula

Species

C. fornicata

I pulled this card for several reasons. First it has the cutest little veliger larvae. Second, it is all over the place here in Long Island Sound. And lastly, it is a prime example of a reproduction strategy that is comparatively rare in the animal world in general, but much less so in molluscs: protandrous sequential hermaphroditism. You may recall Dr. M's recent post, "Who likes protandric hermaphrodites?", in which he described the strategy, while reporting new findings about Idas washingtonia, a deep-sea clam.

Like I. washingtonia, the Atlantic Slippersnail (Crepidula fornicata), is a protandric sequential hermaphrodite. While they strongly resemble limpets externally, and are often called slipper limpets, they are indeed gastropods that are common inhabitants of the sub– to intertidal area of New England rocky coasts where they are often found in stacks, like the one pictured, from 3 to 20 individuals. Unfortunately, they are also an invasive species becoming all too common in areas outside its native range, where their filter feeding capabilities may negatively affect native and aquacultured filter feeding molluscs.

As Dr. M described in his post, many protandrous sequential hermaphrodites change sex based on size. A prevailing theory (the size-advantage hypothesis) predicts that a species will change its sex at a particular size that allows the individual higher reproductive success. Generally, this means smaller Atlantic Slippersnails are males and larger ones are females. It is energetically expensive for females to produce large, energy–rich eggs. It is very common in the marine realm that older, larger females produce more eggs of larger size and higher quality with resultant higher success rates. For guys to produce sperm is a comparatively inexpensive expenditure of energy. Even a wee lad can produce enough sperm of suitable quality to reproduce successfully. (Whether or not a female will have him, of if his sperm can out compete a larger male's sperm, is a different issue.)

C. fornicata follows this trait — for the most part. When the planktonic veliger larvae metamorphose and settle to the bottom, they are attracted to chemical cues produced by the adults. This guides most settling juveniles to land on, or very near, existing individuals or stacks. They then make their way (ever slowly) to the top of the stack and mature into young males. In paternity studies the oldest, largest males (sometimes the same size as females) are responsible for the majority of the viable larvae from females in the stack (upwards of 83% of larvae coming from one father). Younger males further up the stack do have some successes, though, and the more males (and more larger males) in a stack the more sperm competition appears to play a significant role in each individual's success and the less dominant the dominant male becomes. At a certain point these large dominant males may be better off as females sharing the reproductive success among a few females instead of many highly competitive males.

If a settling juvenile misses the chemical cues or for some other reason does not stack onto an existing individual or group, it will mature through a very brief male phase then become female, hopefully attracting juveniles from the next batch to settle on to it. Given that there are solitary (small) post settlement females and that some older males in a stack are as big as their female stackmates, size is clearly not the sole cue for sex change in C. fornicata. There is some plasticity in the change and social interaction appears to play a strong role on the size of the individual undergoing sex change.

You can probably see why sequential hermaphroditism is such an interesting area of study. There are several general hypotheses, but there are also so many individual variations on those general themes, that it seems we will never run out of study material!

And now a word for our Challenge this month

If you have contributed to the Oceans in the Classroom Challenge - Thank you so much!! These posts and previews are for you! You have helped the Ocean Bloggers make a difference in at least 300 kids' lives. (More considering many projects have reusable multi-year assets!)

If you have not yet given to the Donors Choose Oceans in the Classroom Challenge, please consider giving today. I know times are tough. I am a grad student with a family to feed. Believe me, I get how tough it is. Still every amount is welcome and appreciated. For my family's donation it means I have to brown bag it for two weeks. But you know, that's a small price to pay in exchange for knowing that we are exposing hundreds of kids to the science of the ocean. There is even a kindergarten class project in there - Commotion in the Ocean. Talk about a great time to open a kid's mind to the ocean and science!! If 25 readers give just $10 each, we'll help a dedicated young teacher expose 18 high poverty area kindergarten kids to science and the ocean.

There is a chance, still, to get an additional $2,000 dollars of matching funds donated by HP, but it will only happen if we can get to $2,000 donated from the Ocean Bloggers readers today. It won't be easy, but it's a great chance to really increase our impact! Please give to the Challenge!

References

Proestou DA, Goldsmith MR, & Twombly S (2008). Patterns of male reproductive success in Crepidula fornicata provide new insight for sex allocation and optimal sex change. The Biological bulletin, 214 (2), 194-202 PMID: 18401001

Richard, J., Huet, M., Thouzeau, G., & Paulet, Y. (2006). Reproduction of the invasive slipper limpet, Crepidula fornicata, in the Bay of Brest, France Marine Biology, 149 (4), 789-801 DOI: 10.1007/s00227-005-0157-4

Nautilus Night - Cephalopod of Diamonds

Ok. I said for each of the Ocean in the Classroom projects fully funded I would put up a post about one invert from the deck of cards I have been working on, along with a sneak peak at a card. So, since the Making Waves, Oceans and Landforms got fully funded, and in honor of Nautilus Night I bring you the Cephalopod of Diamonds - The Chambered Nautilus.

Classification for the Chambered Nautilus

Kingdom

Animalia

Phylum

Mollusca

Class

Cephalopoda

Order

Nautilida

Family

Nautilidae

Genus

Nautilus

Species

N. belauensis

Some interesting facts about the chambered nautilus (and other extant nautiloids):

The 6-7 (there is still debate on the status of one species) extant species of nautilus come from two genera, the 4-5 smooth nautilus'(genus Nautilus) and the 2 species of hairy nautilus (genus Allonautilus - literally "other nautilus").

They are the only remaining cephalopods that retain an external shell, which they use for defense and as a buoyancy control system. The shell, with buoyancy control, was a significant weapon evolutionarily, as it afforded the early cephalopods the protection of a thick shell yet the advanced buoyancy control unchained them from the sea floor as most of the periods marine arthropods were.

Modern nautilus are generally found on steep coral reef slopes at a depth of 200-400m during the day. They rise at night to feed near or at the surface, using the adjustable buoyancy of their gas filled shells to good effect during the vertical migration.

Unlike other cephalopods, the nautilus do not have a lensed eye. The nautilus eye is more like a pinhole camera, leading to the hypothesis that it uses olfaction to find it's prey (mostly shrimp and other crustaceans along with some small fish.)

Nautiloids also have upwards of 90 tentacles (compare with 8 arms of octopods and 8 arms an two tentacles of squid and cuttlefish.)

Last bit for this post is their lifespan and reproduction. Most cephalopods are short lived with overall lifespans of even the Giant Pacific Octopus being around 2-3 years. For most studied cephalopods natural death from old age occurs after mating, (and for females egg guarding), which is only done once (called semelparity). Nautilus can live in 15-20 years and mate year after year (iteroparity).

The nautilus are the ancient lineage of the cephalopods, descendants of and most like the orthocerids and other nautiloids that were a major predator of the seas in the Ordovician period. Modern nautiloids are the only cephalopods that retain their external shell and are often considered to be "living fossils" as they are very similar in appearance to the ammonites and nautiloids that emerged half a billion years ago in the Cambrian. However recent molecular studies are casting some doubt on the appropriateness of the "living fossil" moniker. Studies published in the past couple years have revealed that the 6-7 extant species of nautilus evolved much more recently, around 2 million years ago, in the seas around New Guinea. They then


Sinclair, B., Briskey, L., Aspden, W., & Pegg, G. (2006). Genetic diversity of isolated populations of Nautilus pompilius (Mollusca, Cephalopoda) in the Great Barrier Reef and Coral Sea Reviews in Fish Biology and Fisheries, 17 (2-3), 223-235 DOI: 10.1007/s11160-006-9030-x

Ocean in the Classroom Challenge

Today's a big outreach day!

First up, an outreach project I that has been part of my life for the past year is finally coming to be. This afternoon I will finally see the professionally printed version of my deck of cards that will be used to help teach molluscan diversity. They are still prototypes so I can't show them here just yet. Hopefully soon I can highlight a few of the cards along with some discussion about the animals on them and the process of making them. I am looking forward to hearing from the COSEE particpants at Avery Point who will be getting a sneak peak at them today through Saturday.

On a much larger scale Dr. M and Kevin have gathered together many of the top ocean bloggers to support some serious K-12 education outreach: Ocean in the Classroom Challenge. I just looked through the challenge and there are seven great projects in there, including several that are aquatic invertebrate centered. Personally I love the Invertebrates in my Tank, Waders and Coral Flip Book projects because they touch close to home, so to speak.

I would take the website hostage like the DSN boys are doing, but that won't work so well here where it has been so quiet lately. However, maybe the opposite will work, for each project that gets fully funded I'll put up a post on recent research about one of animals featured in the card decks.

Channeled Whelk with Egg Cases

Channeled Whelk with Egg Cases, originally uploaded by eclectic echoes.

Family friends bought us passes for Project Oceanology's Enviro Lab cruises at an auction this summer, and finally, as the summer draws to a close, we were able to take advantage of them. Project O is an outreach center that focuses on marine science and environmental awareness especially of the Long Island Sound ecosystem. Their Enviro Lab boats are equipped with a small sample trawl, water quality samplers and sediment samplers. I had been on the Enviro Lab boats with classes from the Marine Science undergraduate program at Avery Point (Project O is located on the Avery Point Campus).

For Johann and Tammy it was a new and exciting adventure. Johann's favorite part was examining the results of the benthic sample trawl. After seeing the Mystic Whaler (Which chanteyman extraordinaire Geoff Kaufman often sails aboard) he was inspired to sing a round of "Donkey Riding" as he reeled in the line from the trawl. The fun really started when he got to get really hands on with the samples helping quickly sort the haul and get all the animals into the large wet tanks. In the haul were a dozen Scup (Stenotomus chrysops), several Sea Robin (Prionotus carolinus), some Atlantic Moonfish juveniles (Selene setapinnis), what looked like a small striped bass (I didn't get to see it but that was the description), a feisty female little skate (Leucoraja erinacea) and a spotted hake (Urophycis regia).

While there was quite a number of vertebrates in the haul, there were far more inverts brought up. Among the inverts there were in excess of a hundred spider crabs (Libinia emarginata), two lobster (Homarus americanus,)(both female), two European Green Crabs (Carcinus maenas), one Jonah Crab (Cancer borealis), several broad-clawed hermit crabs (Pagurus pollicaris) and one male Horseshoe crab (Limulus polyphemus). Molluscs were well represented as well with many mud snails (Nassarius obsoletus) and slipper shells (Crepidula fornicata)as well as a half dozen loligo squid.

The real prize though was this female channeled whelk (Busycotypus canaliculatus formerly Busycon canaliculatus). Johann spotted her and pointed out the fact she was currently "laying" and egg case string. Soon after the animals were sorted into the tanks, the guide showed the whelk and explained the egg case string to the guests, then she carefully (more or less) dropped the whelk back into the sound.

The main reproductive time for the channeled whelks is the fall. Egg strings like the one this lady is laying will consist of 40-160 or more egg cases all joined by a tough leathery string. Each case may have as many as 100 eggs inside, though the average number of eggs per case is closer to 40. Not all the eggs in each case are fertilized though and the unfertilized eggs serve as food for the young whelks which emerge from the cases as miniature adults.

There is a small fishery for whelks here in the Long Island Sound, mostly sold in Italian markets as scungili. Unfortunately the most common bait used is chopped up horseshoe crab.

Life Photo Meme