Gastropods

Gastropod means "stomach foot" and includes all snails and anything else that makes one shell. Gastropods have one foot, one shell, and one siphon.

Some shells are spiral and have an operculum to act as a door for when they hide inside. The snail lives in the entire shell (all the way up into the top and retreats inside to hide when it feels threatened or exposed. The operculum blocks any would-be attackers and is made of a material similar to fingernails. These types of molluscs include whelks and moon snails.

Other shells are not spiral and the snail has good suction power so that predators have a difficult time pulling the snail off the rocks. These types of molluscs include slipper snails, abalones, and limpets.

Nudibranch (naked-gills) are sea slugs that have lost the ability to make a shell over evolutionary history. They are still classified as gastropods.

Even though they don't have a shell, they do however have some interesting adaptations to keep from getting eaten. Most nudibranch exhibit warning coloration because they are poisonous or have stingers - none that they make - they acquire them from the prey that they eat!

National Geographic did a great article a few years ago full of lovely photos. Both are linked here. Watch the video for a full-range spectrum of photos.

Freshwater molluscs?

Most people do not know that there are freshwater clams and mussels in Lake Anna and that they can get as big as the palm of your hand. Nathan, a former student, did his Governor's School project about some of the habitat in the lake and I has asked him to bring in some of these beauties so we could get a good look at them. With the help of his brother, Nathan brought in three little clams for us to enjoy in class.

I found that taking pictures of them in the cup was not easy, but using the document camera, I was able to project an up close view of them onto the wall so that everyone could see the clams and their siphons in detail. Students were able to watch the clams in action. Now that may seem like an oxymoron - clams in action... but there was stuff to see.

You could clearly see the siphons and at times see particles being sucked into the siphons. I put some fish food in the cup and the suction power of the clams was enough to create a current that caused the fish flakes to swirl around in the top of the cup. In first period we were able to watch one of the clams use its foot to dig into the sand to sit upright with its siphons up.

Mollusc Pearls

Pearls can be made by any mollusc that has a shell. I passed around my pearls and some shells that I have with pearls on the sides - not all pearls are free floating - they can be attached to the side of a shell.

A mollusc makes a pearl to cover an irritating spot like a piece of sand that gets inside the shell. Pearls can be "glued" to the side of the shell or free to move inside the mollsucs shell. We prefer the "free" kind.

Here is a great short video that explains the process!

Any mollusk that produces a shell can produce a pearl. Nevertheless, naturally occurring pearls are rare, found in perhaps one of every 10,000 animals. The cultured pearl industry, which has flourished since the early 20th century, has developed techniques to greatly improve these odds. Indeed, more pearls are produced now than at any time in human history.( SOURCE This is a good website for lots of information on pearls)

Mollusc Basics - Chitons and Bivalves

Students are in the midst of Unit 4 Molluscs busily learning about the different classes of Molluscs and trying to learn a variety of sea shells. Students have learned the basics about sea shells

• The shells found on the beach are from dead organisms.
• Any mollusc that has a shell, makes it shell.
• Sea shells are made of calcium carbonate.
• Shells are smooth on the inside because slimy molluscs don't want to rub their soft bodies on something rough. If they are smooth on the outside, then the mollusc also wears its body on the outside of its shell.

Today's cool mollusc was the chiton, an odd mollusc that has 8 overlapping plates held together by its soft squishy mantle, and the plates come apart when the animal dies. Chitons are built like armored cars and have great suction to stay on the rocky coast in waves and storms. They spend their days sliming around scraping algae. When pulled off a rock, it can roll into a ball to protect its squishy parts. More info can be found here

Students also learned the four major classes of bivalves - clams, mussels, oysters, and scallops. Bivalves have 2 shells and 2 siphons, as well as adductor muscles to help keep their shells from opening for hungry predators. Bivalves include some of the more well know shellfish like scallops, clams, oysters, and scallops as well as a few like jingles, ark shells, and cockles. Pictured to the right are a clam (tan), oyster (grey), and mussel (black).

Mussels make byssal threads for attaching (so do ark shells and jingle shells) and scallops have eyespots to see predators. Oysters make cement to stick together and clams have a powerful foot for digging down and hiding.

Coral Reef basics

We finished class by discussing coral reefs and passing around coral skeletons made of calcium carbonate that I have collected on my travels and inherited from my grandmother. Each hole in the coral houses a polyp... and all the polyps make up the coral colony. So the polyps make up a superorganism. We then watched some BluePlanet and learned about some of their predators like the crown of thorns sea star and saw how the corals that sometimes look like rocks are able to attack and eat each other.

Biomes II

Students have been learning all the different biomes that exist in the oceans. Most people have heard of coral reefs and think about the beach, but there are actually many different biomes in the ocean. Not all biomes are found at the bottom of the sea. Along coasts you can find rocky coasts, sandy beaches, salt marshes, mangroves, sea grass beds, kelp forests, and fouling communities.

Kelp forests are dominated by kelp that can grow to 300 feet tall. The kelp is held near the surface by lots of air bladders. Kelp forests are important because they provide a lot of substrate and habitat for organisms to live, hide and eat.

We also discussed sea grass beds. Sea grass is super-important for stabilizing the substrate and holding the sand down. This promotes water clarity and decreases turbidity. Nothing eats sea grass when it is alive except for manatees. Everything else eats it after the bacteria have decomposed it a bit.

Salt Marshes are one of the most productive ecosystems, but nothing eats the salt marsh grass when its alive... once the anaerobic bacteria break it down into black mush, then other organisms eat it.

Mangroves are trees that can grow in salt water. They have crazy prop roots or finger like roots called pneu- mato- phores that stick up out of the water so the tree can get oxygen during high tide. The roots provide a lot of substrate that a lot of fouling organisms will colonize and use as habitat. 

Photic vs Aphotic is an odd one involving the light and dark zones of the ocean. Some organisms hide in teh dark aphotic zone during the day and migrate up to the surface (the photic zone) at night to eat the phytoplankton. Predators also migrate to eat the things that are eating the phytoplankton. 

There is a lot of information to learn this unit. The Unit 3 Test is one of the hardest of the year.

Biomes in the Ocean

Students have been learning all the different biomes that exist in the oceans. Most people have heard of coral reefs and think about the beach, but there are actually many different biomes in the ocean.

One of the weirdest, but also most interesting is Whalefall. Whalefall is when a dead whale settles to the bottom of the ocean and organisms move in to feed on the carcass until even the bones are decomposed. Hagfish are a dominant scavenger as well as bacteria. It may not seem like a big deal, but this biome boasts over 160 species that are not found on the surrounding benthos. More info can be found at the link above, or here. Listen to a podcast here.

Deep sea benthos is another biome and it is pretty boring. Its a gooey squishy substrate populated by some dd scavengers, but there is not a high biodiversity and not a lot of food to eat.

Not all biomes are found at the bottom of the sea. Along coasts you can find rocky coasts, sandy beaches, salt marshes, mangroves, sea grass beds, kelp forests, and fouling communities.

I think fouling communities are really interesting... because all these organisms need is a hard substrate (surface) to stick on. This could be a dock, a pier, a boat, or anything that's in the water long enough. Most people have seen all the 'stuff' growing on the pole legs of piers and docks, but don't really think of the variety of organisms that grow there - or their importance. Most of these organisms are filter feeders and do a lot for water quality. They also break down the surfaces like scavengers... not something we want for our boats and docks we use, but important nonetheless.

There is a lot of information to learn this unit. Students will be given two review sheets - one general, one biome specific. The Unit 3 Test is one of the hardest of the year, and it will be soon.

Zonation... especially in Rocky Coasts

Today we discussed zonation in Marine Ecology. Zonation happens when organisms are adapted to a very specific set of conditions. Because some organisms are better adapted to these certain conditions, we see bands of organisms occupying zones. Today we talked about zonation and specifically how it affects the rocky coastline.

Students identified zones on rocky coast pictures and took notes on the material. Here is an example of a photo where the zones can clearly be seen by changes in dominant seaweeds. The yellow layer is the upper zone and the white pink is the middle zone. It is easy to see the high water mark or where the high tide will reach. You can also see the lichens in the spray zone.

The spray zone is one of the hardest areas to live in because of the huge changes in salinity and temperature.

We also talked about tide pools. Tide pools are depressions that trap water when the tide recedes. You can find all kinds of things in tide pools, but tide pools in the lower zone have a higher biodiversity than tidepools found in the upper zone. This is because they are more often "refreshed" with water that keeps salinity, dissolved oxygen, and the temperature stable, as well as add nutrients and more food! Here is a neat article from National Geographic about tidepools (and where this photo is from).

Types of Seaweed

Students learned about the three types of seaweed. Seaweed and algae are the same thing and they are classified by pigment type - red, brown, or green. 

Red seaweeds are the most common, but we don't see a lot of them because they like tropical waters and deep waters. 

Brown algae is the most common seaweed on our coast, whereas green algae is the most common in the freshwater of Virginia.

There is also cyanobacteria - or the blue green algae which we discussed during the plankton part of the unit. 

Some algae is calcareous - meaning it stores calcium carbonate in its tissues. This makes it crunchy and deters herbivores. The most common is a calcareous red algae that makes a pink crust on just about everything left in the ocean.

A lot of seaweed has air bladders to help it float towards the surface.  Air bladders ensure adequate sunlight for photosynthesis. Other important adaptations include flexibility and gels to stay hydrated when the tide goes out. Students observed samples of dried seaweed.

Plankton Introduction

Today students got new seats and started a new unit on Plants, Plankton, and Biomes. This is probably our longest and most difficult unit because of the large amount of information that needs to be learned and applied.

We started class with a discussion about phytoplankton (cyanobacteria pictured above) and its importance to the ocean and to the world. Phytoplankton are responsible for feeding most of the creatures that live away from the shore and they are important for adding oxygen both to the water and to the atmosphere.

We are learning about plankton! Plankton include organisms that drift through the seas that cannot swim and do not attach to the bottom. Plankton can be classified a variety of ways.

The first way is to classify them by size. Microplankton and nannoplankton require a microscope if you want to see them because they are so tiny. Macroplankton are small, but you can see them without a microscope. Megaplankton are big enough to pick up and include things like jellies.

Another easy way to classify plankton is into plants and animals. Phytoplankton are tiny plants that photosynthesize and make their own food. Zooplankton (belong in the the zoo) and are animal plankton.

Plankton can also be classified as holo- plankton and mero- plankton. Holo- plankton are plankton for their whole lives (forever) and meroplankton are only plankton for part of their lives. The meroplankton may be plankton when they are eggs, larvae, juveniles, all of those stages, or only some of those stages. Most of the invertebrates and fish in the ocean spend some time in their life as a plankton because it allows them to spread around the ocean and find new places to live. This photo is a meroplankton snail larvae that grows into a poisonous cone snail. Part of its body hardens in to the shell it carries for the rest of its life. This is my favorite website about plankton and it is where all my photos come from. Check out the other types of meroplankton.

Students have drawn their own plankton, tried to match meroplankton to the adult forms, and are currently designing plankton to compete in the Plankton Grand Prix - where the object is to sink slowly.

Parastism

A really gross human parasite is the botfly. You can listen to a podcast about a scientist who was infected with a botfly larvae. Botfly larvae are transferred to humans by mosquito bites and the larvae grow bigger and develop under the skin feeding on the host. This scientist was a bit strange and decided to allow the botfly larvae to develop on his head until it grew enough to leave on its own. A little gross. You can listen the podcast here. Of course then we had to see a video of one getting removed. Also gross. Here's a video from AnimalPlanet, although not the one I showed class.

You can watch a video about the candiru fish in the Amazon that swims into other fish's gills and sucks their blood - not so bad - except urine smells the same, so when people are in the water peeing, it is attracted to the people and swims up their urethras. Ouch.

Symbiosis - Mutualism, Commensalism, and Parasitism

Mutualism is the relationship that is best understood because both organisms benefit - although the advantages are not often clear to us. Pictured to the left are an alligator and plover, eel and cleaner shrimp, and zebra and finch - all of these are cleaning relationships. The smaller organism eats parasites and gets a meal and the larger organisms will not eat it as well as get the benefit of being cleaner (less infection and disease). The bottom right picture is a blind bulldozer shrimp and a goby fish. They share a dwelling that the shrimp builds, and the fish lets the shrimp know when trouble is coming.

Parasitism involves things that give us the heebie jeebies. These parasites take advantage of their host, usually feeding on the host, and benefit. The host gets no benefits and over the long term is harmed. Pets can get a lot of different kinds of parasites. Some are internal and some are external.

Commensalism is when one organism benefits and the other is unaffected. So one gets all these advantages from the other... but the other doesn't get a benefit from it and isn't harmed by it.These pilotfish are always with the shark using him as a predator deterrent, but the shark never eats them and doesn't benefit from them in anyway.

Sexual Dimorphism

Sexual Dimorphism is when males and females exhibit different characteristics. These usually involve, color, size, behavior, and other appendages. 

In the animal kingdom, males are typically brighter and more colorful. The males are trying to prove to the ladies that they have good genes, they are disease free, and they can escape predators. 

Larger males can win contests against other males also proving their good genes. Though the males show off, it is the female's choice when she ultimately makes a decision. It is possible for a female to reject all males and choose none. 

Differences in size and coloration indicate that there is female choice, the female will choose a male to fertilize her eggs and in most cases, his job is done, and she leaves to finish the baby-forming process. All she wanted was his genes. 

When a large group of organisms all spawn at the same time, the organisms rely on luck and statistical chance for genetic variation. Males and females will look similar because there is no choice involved.

When males and females work together and take an equal role in raising young or protecting eggs, the males and females tend to look more similar. They look similar because of their equal roles and because the choice is longer-lasting. She is looking for more than just a pretty face (and pretty faces in the animal world do not indicate good egg care or being able to provide nesting materials, food, etc).

Differences in size between males and females varies widely. There is no set rule for who will be bigger, but there is usually a clear reason as to why one of them is bigger. Males can be bigger because they fight other males, because they have to guard eggs, or other reasons. Females can be bigger because they have to carry and nourish a fetus, carry and develop eggs, protect babies, or other reasons. To know why a male is bigger or a female is bigger the biology and reproductive strategies have to be understood.

Keystone Species

We talked about keystone species. Keystone species are important members of the food web because they help maintain biodiversity and keep everything in balance. An example is a sea otter. Sea otters eat sea urchins and keep their population in check.

When the sea otters are removed (like when they used to be hunted for their fur), the sea urchin populations go crazy, eat all the kelp (as in many many 300 foot tall plants), and the loss of kelp leads to a drop in biodiversity because there is less food and habitat for the many other species that like to live in and on and among the kelp.

Expanding your Horizons: Squid Skin

As an introduction to cephalopods, we watched a video that showcased the awesome camouflaging abilities of cephalopods. Cephalopods include the well known octopus and squid, but also the cuttlefish and a creature called a chambered nautilus.

These molluscs are able to control their color by rapidly changing the chromatophores in their skin.

This week, students will need to watch two videos, answer some questions, and then think about what they would use this ability for.

Video1 - Deep Look - Squid Skin

Video2 - Richard Hammond - Can a Cuttlefish camouflage to a living room?

Optional Video2 - Science Friday  Where's the Cuttlefish?