Sea Slugs, Snails, and Sea Hares, Oh My!

I love slugs! They are one of my favorite animals, particularly if limiting the scope of the question to invertebrates. In my opinion, they are one of the most beautiful and fascinating organisms.

You’re likely thinking I have lost my mind. “You really think this guy is beautiful?” 

Sea Slugs, Snails, and Sea Hares

Pictured here is the banana slug

Yes, I do. Well, actually, in my mind I was picturing his close relative the sea slug or nudibranch. This summer, I have been volunteering at the new Marine Life Center at the Oregon Institute of Marine Biology and I’ve thereby had the opportunity to learn so much about these fascinating animals. Let me introduce you to the gastropods.

Class Gastropoda 

The Gastropoda or gastropods class, more commonly known as snails and slugs, are a large taxonomic class within the phylum Mollusca. A very diverse group with 60,000 to 80,000 living species (second only to insects in number of species) that includes snails and slugs of all kinds and all sizes from microscopic to large. There are many thousands of species of sea snails and sea slugs, as well as freshwater snails, freshwater limpets, land snails and land slugs.

Sea Slugs, Snails, and Sea Hares @EvaVarga.net

How many sea slugs can you find in this picture?

The anatomy, behavior, feeding, and reproductive adaptations of gastropods vary significantly from one group to another. The class also inhabits an extraordinary diverse habitats including gardens, woodland, deserts, mountains, rivers and lakes, estuaries, mudflats, the rocky intertidal, the sandy sub-tidal, the abyssal depths of the oceans including the hydrothermal vents, and numerous other ecological niches, including parasitic ones.

Sea Slugs, Snails, and Sea Hares @EvaVarga.net

Gastropoda means the belly-foot animals

Snails & Other Shelled Gastropods

Commonly, snails are those species with a single external shell large enough that the soft parts can withdraw completely into it. Those with a shell into which they cannot withdraw are termed limpets.

The marine shelled species of gastropod include species such as abalone, conches, cowries, periwinkles, whelks, and numerous other sea snails. Each produce seashells that are coiled in the adult stage. In a number of families of species, such as all the various limpets, the shell is coiled only in the larval stage, and is a simple conical structure after that.

Sea Slugs, Snails, and Sea Hares @EvaVarga.net

Pictured here is Hermissenda crassicornis

Slugs or Gastropods Without External Shells

Those gastropods without a shell, and those with only a very reduced or internal shell, are usually known as slugs. The various families of slugs are not closely related, however, despite a superficial similarity in the overall body form.

Sea Slugs

The phrase “sea slug” is perhaps most often applied to nudibranchs and they come in an outstanding variety of shapes, colors, and sizes. With translucent bodies, they appear in just about every color on the rainbow. Of course, these bright colors are cause for warning to potential predators that they are poisonous with stinging cells. It is their colors that so fascinate me.

Like all gastropods, they have razor-sharp teeth, called radulas. Most have two pairs of tentacles on their head used primarily for sense of smell, with a small eye at the base of each tentacle. Many have feathery structures (ceratia) on the back, often in a contrasting color. These act as gills.

All species of sea slugs have a selected prey, that is specifically fitted for them to hunt. Amongst the diverse prey are jellyfish, bryozoans, sea anemones, sponges, and other various organisms including other sea slugs.

Sea Slugs, Snails, and Sea Hares @EvaVarga.net

Pictured here is Phyllaplysia taylori

Sea Hares

The sea hares, clade Aplysiomorpha, are often quite large and sometimes described as large sea slugs. They have a small, flat, internal shell composed of proteins. The name derives from their rounded shape and from the two long rhinophores that project upwards from their heads and that somewhat resemble the ears of a hare.

The greatly modified shape of the sea hare and the fact that it orients its body lengthwise along the leaves makes it almost invisible on the sea grass Zostera. An herbivore, it feeds by grazing the film of organisms, mainly diatoms, off sea grass leaves, leaving a characteristic feeding scar on the leaves.

Take it Further

Learn more about Phyla Mollusca in my earlier post, Echinoderms and Molluscs.  You might also be interested in my in-depth zoology curriculum specifically designed for middle school students.

zoology

Discovering China: Yangshou – Caves, Cormorants, and Snails

discovering china

Nihao!  I’m delighted you are joining me for the seventh of ten posts whereby I introduce you to the culture of China through our eyes.  Today, I bring you to Yangshou – where you will discover caves, cormorants, and snails. Of all the cities we had the chance to see during our three-week family holiday in China, Yangshou remains the most special to me. The scenery was stunning.  The people were so welcoming.  It reminded me a little of my beloved Oregon.

yangshouIn Chinese paintings there are scenes of fantastically shaped misty mountains – these aren’t merely in the eye of the artist – you can see this landscape around Guilin. The Guangxi Zhuang Autonomous Region is famous for its scenery dominated by the karst peaks that create some of the most famous landscape images of China. You’ve likely even seen them featured prominently in an episode of Star Wars.

Caves

What you don’t see in those photos are the hundreds of caves that go right along with the landscape (where there’s a limestone mountain, there is a cave). The area around Yangshuo – where we stayed – has many caves for spelunking, some you wander through, some in which you can even enjoy a mud bath.

We had to make changes to our original itinerary and we didn’t have as much time here as we’d hoped. For this reason, we sadly didn’t make it to these caves.  Even so, we had a wonderful time and Yangshou remains one of our highlights.  With the help of our hotel, a driver met us at the airport in Guilin and escorted us to our resort in Yangshou. We arrived just in time for lunch – a local favorite of braised beer fish – and thereafter enjoyed a delightful motor boat cruise on the Li River.

Li River

The motor boat was loud and in the humidity, it was not the most comfortable ride (our driver went up river very slowly – I think every other boat must have passed us).   After about 45 minutes, he stopped at a small island where he directed us off the boat and we were immediately encouraged by the vendors to sample their offerings as well as have our photo taken with the captive cormorants.  This made me uncomfortable but I obliged.

After our river cruise, we visited Xingping, an ancient village in existence for over 1500 years. In the village, we could see stone streets and crumbly brick buildings with tiled roofs, surrounded by the mountains.   We then returned to the Yangshou Mountain Resort where we were staying to change and go down to dinner. Can you believe we ordered burgers?  The freshly in  house-baked buns and local vegetables (particularly the tomatoes) made it one of the best burgers I’ve ever eaten.

Cormorants

Later that evening, we went into town again for the cormorant fishing show. Cormorant fishing is a traditional fishing method in which fishermen use trained cormorants to fish in rivers. Historically, cormorant fishing has taken place in Japan and China since about 960 AD. The types of cormorants used differ based on the location; Chinese fishermen often employ Great Cormorants (P. carbo).

To control the birds, the fishermen tie a snare near the base of the bird’s throat. This prevents the birds from swallowing larger fish, which are held in their throat, but the birds can swallow smaller fish – we observed this on a few occasions.  When a cormorant has caught a fish in its throat, the fisherman brings the bird back to the boat and has the bird spit the fish up. Though cormorant fishing once was a successful industry, its primary use today is to serve the tourism industry.

yangshou cormorant fishingThe following day, we stayed close to the resort as we were to depart in the early afternoon for the train station.  We enjoyed a lazy float on inner tubes reminiscent of my childhood on the Yulong River amid a beautiful backdrop of karst mountains.  We played a little Pīngpāng qiú (乒乓球) – a sport in which China dominates.  We slowly, reluctantly packed our things.

While in Yangshou, travelers can also enjoy a relaxing ride on a bamboo raft on the river. The skillful crewman uses a long pole to navigate the raft.  As our time in Yangshou was limited, we didn’t have the chance to take a bamboo raft down this section of the river – but we did enjoy watching others.

Snails

The kids would have liked to captain their own raft but had to console themselves with the one that was anchored near the resort.  Here they found numerous snails who they quickly befriended. We’d watched the movie Turbo just prior to departing for China, so they both had a fond affection for snails.  You can read more about our impromptu snail study in my earlier post, Nature Study in China: Phylum Mollusca.

Had we had more time in this province, we would have enjoyed a trek in the Longji Rice Terraces. This famous area is north of Guilin and famous for its minority villages and incredible scenery. The mountains here are terraced from top to bottom and create a stunning landscape.

I will be wrapping up the Discovering China series tomorrow with Hong Kong where during our final days in China, we celebrated Sweeetie’s birthday.

Autumn-Hopscotch-2013

This post is part of the iHomeschool Network’s Autumn Hopscotch, a 10 day series of posts by over 40 different homeschool bloggers. You can visit the hopscotch home page at iHN for ideas and inspiration. Have you taken a peak at some of the other posts?  If not, I encourage you to do so. You’ll surely find something to inspire you!

All 10 days of Discovering China will be linked to one landing page.  Bookmark it for reference!

Nature Study in China: Phylum Mollusca

Prior to our departure for holiday in China, we had enjoyed the new DreamWorks movie, Turbo. Snails were thereby on our mind and to the delight of the kiddos, we happened upon a few small garden variety in the ancient gardens of China and at the Panda Breeding Center in Chengdu.  In Yangshuo, we discovered what the locals called Duck Snails, a large freshwater snail belonging to the family Ampullariidae.  The more accepted common name is the Apple Snail, an aquatic gastropod mollusks with gills and an operculum.

apple snails

Field Studies

We first noted the presence of these snails because of the bright pink egg masses that we observed all over the shoreline of the Yu Long (Dragon) River. These egg masses are laid on solid surfaces up to about 20 inches above the water surface. An average clutch contains 200 to 600 eggs, with each egg measuring 0.9 to 1.4 mm in diameter. Soon thereafter, as the kids began to play in the river, we found adult snails in a variety of hues, ranging from creamy yellow to a light pink.

As amateur naturalists, we are not sure exactly what species we observed (Pomacea canaliculata or Pomacea insularum) – perhaps even multiple species.  Based upon our research, we are leaning towards P. canaliculata.  Even so, the kids enjoyed playing with them and watching them glide across the surface of the bamboo boat structure that was anchored near shore.

Sweetie expressed wanting to take them home and of course, I explained that this was not only illegal (customs would certainly not allow us to transport live animals back to the states) but it would also be negligent on our part and potentially environmentally catastrophic.

applesnails

Phylum Mollusca

When we returned home, I took advantage of their interest in the snails, to engage them in a little nature journaling.  I pulled out a few text books and had the photographs we had taken in Yangshuo available on the iPad.  Sweetie ran to her room and brought back one of the shells she had collected during our stay.  We then got about sketching and noting our observations in our journals.

As they worked, I read aloud a book that I had purchased years ago in Hawai’i, Beyond ‘Ohi’a Valley: Adventures in a Hawaiian Rainforest by Lisa Matsumoto.   The illustrations are very beautiful and the characters are very comical; the storyline tells about the native animals of Hawai’i and the impact of invasive, non-native species.  While discuss how similar problems could occur with the introduction of the apple snail – in fact, it is happening …

Pomacea canaliculata is native to temperate Argentina and northwards to the Amazon basin. Through human introduction, this applesnail has rapidly spread to Indonesia, Thailand, Cambodia, Hong Kong, southern China, Japan, Philippines, and Hawai’i. There are indications that they are invading Australia. In the 1980’s, channeled applesnails were introduced in Taiwan to start an escargot industry. This snail was originally imported under the name “golden snail” or “golden applesnail” for human consumption. However, the Asian escargot market never materialized and applesnails, that escaped or were released, ultimately came to cause extensive damage to rice fields. 

I’ve posted more pictures and information about Pomacea canaliculata onto Project Noah.  I encourage you to hop over if you are interested in learning more about Apple Snails.

Submitted to the Outdoor Hour Challenge Blog Carnival at Handbook of Nature Study.