The intertidal zone, that area of the coast that lies between the high tide and low tide marks, is a very difficult place for animals to live. Not only must they deal with crashing waves, any creature inhabiting this zone must be able to withstand being submerged for part of the day and exposed to air for the rest. Most, like mussels and barnacles, are able to seal their shells shut during low tide and simply wait for the water to return.

Unfortunately, they also have to deal with predators. Raccoons and sea gulls come to the intertidal zone at low tide searching for vulnerable prey, while crabs and fish move in with the incoming flow of water to do the same. And then there is the oyster drill.

Arthropods, including crustaceans, insects and arachnids, are by far the largest group of animals that exist on Earth, comprising over 80% of all known species of animals. And the single largest land-dwelling arthropod is the coconut crab (Birgus latro). Found on tropical islands in the Pacific and Indian oceans, these monsters may reach a leg span of well over six feet.

Generally the introduction of a non-native species of plant or animal into an ecosystem is a destructive event. Whether they be rabbits or poisonous cane toads introduced to the Australian outback or kudzu spreading through the American south, these organisms out-compete, consume or displace native fauna and flora. The introduction of these exotics, whether brought to foreign shores by accident or intentionally, is by definition due to human activity.

This is part III on hermit crabs. Hermit Crab Basics is here, and hermit crab reproduction is here.

Tonight I’d like to focus on hermit crab symbionts. Symbiosis is a relationship between unrelated species of animals. There are several different types, ranging from parasitism, where one species benefits and the other is harmed, to mutualism, where both species benefit from the relationship. With hermit crabs, symbiotic relationships tend to be mutualistic, meaning that although the relationship isn’t neccessary for the the survival of either species, it is nonetheless beneficial to both parties. I’d like to take a look at three symbiotic examples here.

As we saw yesterday in the diary Hermit Crab Basics, hermit crabs have abandoned a crustacean's typical total exoskeleton body coverage in exchange for the security of living inside an old univalve shell. The advantage of this strategy is that it can shed the portion of the exoskeleton covering the front part of its body without having to endure that dangerous "soft-shell" stage other crabs have to deal with. As I mentioned, one disadvantage is the crab must periodically find new, larger shells as it grows. As we shall see here, there are other obstacles this animals must contend with as well.

Hermit crabs are found all over the world in shallow waters and are one of the more familiar coastal animals. Although they have an exoskeleton, as all crustaceans do, this protective covering only surrounds the head, legs and claws. To protect the soft rear part of the body they must find a suitable shell to crawl into.

Ok, so after a couple of weeks off for the holidays, MLS is back to continue this series on filter feeding animals. If you need to get caught up, part I, which identified the organisms filter feeders actually feed on, is here.

In this edition we’ll be discussing siphons, which is the main method used by both bivalve mollusks and tunicates to extract these tiny creatures from the water column.

I’m going to break this topic up into multiple parts because this is a pretty big subject. But I should note that I will be dealing mainly with plankton-eating animals such as clams, sea cucumbers, anemones and other non- or slow-moving invertebrates, and not fish and whales.

It’s true that although some fish (mullets, basking sharks) and baleen whales (blues and humpbacks) do "filter" their food from the surrounding water, the animals they feed on, such as krill, menhaden and sand lance are not plankton. These are free-swimming animals so they do not qualify as "drifters". And as far as I’m concerned it makes these larger fish and mammals predators and not filter feeders. This diary will start not with specific examples of these, but with a short study of what, exactly, plankton is.

In vertebrates albinism is usually caused by inheritance of two recessive genes which prevents the body from producing melanin, resulting in white skin and hair, feathers or scales covering the body. These genes come from parents who may not necessarily be albinos themselves, but are carriers of this trait. The chances of an albino being born to two carrier parents is one in four.

In Greek mythology, Cassiopeia was the beautiful and vain wife of Cepheus, an Ethiopian king. Cepheus and Cassiopeia had a daughter, Andromeda, who was to be wed to the hero Perseus. Cassiopeia, at the last minute, decided to promise Andromeda to Agenor, a son of Poseidon.

Agenor arrived at the nuptials with an army, intending to kill Perseus and take Andromeda for himself. If you remember, Perseus is the guy who slayed the Gorgon. As Agenor’s army approached, Perseus retrieved the Medusa’s head and turned the army, including Cassiopeia, into stone. Poseidon decided to place Cassiopeia, along with Cepheus, in the heavens as constellations. However, as punishment for her vanity he placed her in the night sky sitting in a chair that revolved around the North Star so that she would spend half of all eternity upside down.

Most people know the sand dollar as the dried, white "shell" found in craft stores and gift shops. What you are seeing is simply the test, or skeleton, of a once living animal. Sand dollars are related to sea stars and sea urchins, and share many of those other animals’ characteristics, including a ventral mouth, tube feet and spines.