AY Honors/Marine Invertebrates/Answer Key

1. Be able to identify at least one example of fifteen of the following seashore animals:

a. Tunicate (Sea Squirt)

Tunicate

Sea Squirt (Tunicate)

Description: Tunicate, also known as urochordata, tunicata (and by the common names of urochordates, sea squirts, and sea pork) is the subphylum of a group of underwater saclike filter feeders with incurrent and excurrent siphons, that are members of the phylum Chordata. Most tunicates feed by filtering sea water through pharyngeal slits, but some are sub-marine predators such as the Megalodicopia hians. Like other chordates, tunicates have a notochord during their early development, but lack segmentation throughout the body and tail. Tunicates lack the kidney-like metanephridial organs, and the original coelom body-cavity has degenerated to a pericardial cavity and gonads. Except for the pharynx, heart and gonads, the organs are enclosed in a membrane called an epicardium, which is surrounded by the jelly-like mesenchyme. Tunicates begin life in a mobile larval stages that resembles a a tadpole, later developing into a barrel-like, sedentary adult form.

b. Anemone (Sea Flower)

Sea anemones are a group of water dwelling, predatory animals of the order Actiniaria; they are named after the anemone, a terrestrial flower. As cnidarians, sea anemones are closely related to corals, jellyfish, tube-dwelling anemones and Hydra.

d. Hermit Crab

Hermit crabs are decapod crustaceans of the superfamily Paguroidea. They are not closely related to true crabs.

Most species of hermit crabs have long soft abdomens which are protected from predators by the adaptation of carrying around a salvaged empty seashell, into which the whole crab's body can retract. Most frequently hermit crabs utilize the shells of sea snails, marine gastropod mollusks. The tip of the hermit crab's abdomen is adapted to clasp strongly onto the columella of the snail shell. As the hermit crab grows in size it has to find a larger shell and abandon the previous one.

This habit of living in a second hand shell is what gave rise to the popular name "hermit crab", which is a reference to the idea of a hermit living alone in a small cave.

There are about five hundred known species of hermit crabs in the world, most of which are aquatic and live in saltwater at depths ranging from shallow coral reefs and shorelines to deep sea bottoms. However in the tropics, a number of species are terrestrial, and some of these are quite large, for example, Coenobita clypeatus.

A number of other species, most notably king crabs, have abandoned seashells for a free-living life; these species have forms which are more similar to true crabs, and are known as carcinised hermit crabs.

Hermit crabs live in the wild in colonies of 100 or more, and do not thrive in smaller numbers

e. Brittle Star or Serpent Star

Brittle stars are echinoderms, closely related to starfish. They crawl across the sea-floor using their flexible arms as "legs" for locomotion. The ophiuroids generally have five long slender, whip-like arms which may reach up to 60 centimeters (2 feet) in length on the largest specimens.

Ophiuroidea contains two large clades, Ophiurida (brittle stars) and Euryalida (basket stars). Many of the ophiuroids are rarely encountered in the relatively shallow depths normally visited by humans, but they are a diverse group.

There are some 1,500 species of brittle stars living today, and they are largely found in deep waters more than 500 metres (1,650 feet) down.

f. Sea Urchin

Sea Urchins are small, spiny sea creatures of the class Echinoidea found in oceans all over the world. (The name urchin is an old name for the round spiny hedgehogs sea urchins resemble.) Their shell, which is also called the "test", is globular in shape and covered with spines. The size of an adult test is typically from 3 to 10 cm.

Typical sea urchins have spines that are 1 to 3 cm in length, 1 to 2 mm thick, and not terribly sharp. Diadema antillarum, familiar in the Caribbean, has thin spines that can be 10 to 20 cm long. Common colors include black and dull shades of green, olive, brown, purple, and

g. Sea Cucumber

The sea cucumber is an echinoderm of the class Holothuroidea, with an elongated body and leathery skin, which is found on the sea floor worldwide. It is so named because of its cucumber-like shape. Like all echinoderms, sea cucumbers have an endoskeleton just below the skin, but this can actually be absent in some species

h. Bryozoa colony (Moss animal)

Bryozoans are tiny colonial animals that generally build stony skeletons of calcium carbonate, superficially similar to coral. They are also known as moss animals (which is the literal Greek translation) or sea mats. They generally prefer warm, tropical waters but are known to occur worldwide. There are about 5,000 living species, with several times that number of fossil forms known.

i. Barnacle

A barnacle is a type of arthropod belonging to infraclass Cirripedia in the subphylum Crustacea, and is hence distantly related to crabs and lobsters. Some authorities regard Cirripedia as a full class or subclass, and the orders listed at right are sometimes treated as superorders. Around 1,220 barnacle species are currently known. The name "Cirripedia" is Latin, meaning "curl-footed".

Barnacles were first fully studied and classified by Charles Darwin who published a series of monographs in 1851 and 1854. Darwin undertook this study at the suggestion of his friend Joseph Dalton Hooker, in order to understand at least one species before making the generalizations needed for his theory of evolution by natural selection.

j. Sea Star

Starfish or sea stars are any echinoderms belonging to the class Asteroidea. The names sea star and starfish are also (incorrectly) used for the closely related brittle stars, which make up the class Ophiuroidea.

Starfish exhibit a superficially radial symmetry. They typically have five or more "arms" which radiate from an indistinct disk (pentaradial symmetry). However, the evolutionary ancestors of echinoderms are believed to have had bilateral symmetry. Starfish do exhibit some superficial remnant of this body structure, evident in their larval pluteus forms.

Starfish do not rely on a jointed, movable skeleton for support and locomotion (although they are protected by their skeleton), but instead possess a hydraulic water vascular system that aids in locomotion. The water vascular system has many projections called tube feet on the ventral face of the starfish's arms which function in locomotion and aid with feeding.

The star fish usually hunt for shelled animals such as oysters and clams. They have two stomachs. One stomach is used for digestion, and the other stomach can be extended outward to engulf and digest prey. This feature allows the starfish to hunt prey that is much larger than its mouth would otherwise allow. Starfish are able to regenerate lost arms. A new starfish may be regenerated from a single arm attached to a portion of the central disk.

k. Mussel or Clamworm

The Common clam worm (Nereis succinea) is a widely distributed polychaete worm. It is often referred to as a ragworm or sandworm, or simply as the "clam worm", but these terms can all refer to any one of a number of other species of the genus Nereis (or indeed to other polychaetes). The name "common clam worm" is less ambiguous, but is also sometimes used for other Neries species such as N. virens and N. limbata.

The common clam worm can reach up to 15 centimeters (6 inches) in length, but most specimens are smaller than this. It is brown coloured at the rear, and reddish-brown on the rest of its body. It has an identifiable head with four eyes, two sensory feelers or palps, and eight tentacles.

It is a freeswimming polychaete, scavenging on the bottom of shallow marine waters. It feeds on other worms and algae. To feed, it uses a proboscis, which has two hooks at the end, to grasp prey and draw it into its mouth. Clamworms are an important food source for bottom-feeding fish and crustaceans, though they can protect themselves by secreting a mucus substance that hardens to form a sheath around them.

During lunar phases in the spring and early summer, the clam worm undergoes "heteronenesis". Their parapodia enlarge so they can swim. The clamworms are then capable of releasing eggs and sperm. After they have released their egg or sperm, they die.

Planktonic larvae develop, grow into annelids and eventually sink to the bottom of the water.

The common name mussel is used for members of several different families of clams or bivalve molluscs, from both saltwater and freshwater habitats.

"Mussel" is historically applied to bivalves of the marine family Mytilidae, most of which live exposed in the intertidal zone, attached by means of strong byssal threads to a firm substrate. Bivalves referred to as "clams" generally live buried in a soft material, and communicate to the surface by means of a tube or siphon. In most marine mussels the shell is longer than it is wide, being wedge-shaped or asymmetrical. The external color of the shell is dark blue, blackish, or brown, while the interior is silvery and somewhat nacreous. "Mussel" is also used for larger freshwater bivalves, more exactly called "clams", given their mode of existence. Marine mussel species live in intertidal and subtidal areas along coastlines worldwide. A few species have colonized hydrothermal vents associated with deep ocean ridges. Freshwater mussel species inhabit lakes, ponds, rivers, creeks, canals, and similar habitats.

Freshwater mussels (several allied families, the largest being the Unionidae) and saltwater mussels (family Mytilidae) are not closely related. They are taxonomically grouped in different subclasses, despite some superficial similarities in appearance.

The freshwater Zebra mussels and their relatives in the family Dreissenidae are not related to either of the previously mentioned groups, even though they resemble many Mytilus species in shape, and live attached to rocks and other hard surfaces in a similar manner. They are classified with the Heterodonta, the taxonomic group which includes most of the bivalves commonly referred to as "clams".

l. Sea Jelly

Jellyfish are marine invertebrates belonging to the class Scyphozoa of the phylum Cnidaria. They can be found in every ocean in the world and in some fresh waters. The term "jellyfish" is a common name, and therefore does not imply any systematic relationship to vertebrate fish -- jellyfish are cnidarians. The term "jellyfish" is also applied to some close relatives of true scyphozoans, such as the Hydrozoa and the Cubozoa.

m. Limpet

Limpet is a common name used for many kinds of mostly saltwater but also freshwater snails, specifically those that have a simple shell which is more or less broadly conical in shape, and which is either not coiled, or appears not to be coiled, in the adult snail.

Thus the word "limpet" is an inexact name which is fairly often used as part of the common name of a wide variety of different marine and freshwater gastropod species, some of which have gills and some of which have a lung. The name is given on the basis of a limpet-like or "patelliform" shell, but the several groups of snails which have such a shell are not at all closely related to one another.

The phrase "true limpets" is used only for marine limpets in the ancient order Patellogastropoda, in the subclass Eogastropoda. In the latest taxonomy the Patellogastropoda have become an unranked taxon as a separate clade including :

n. Tube Worm

The name tube worm may refer to any of a number of unrelated tube-dwelling worm-like invertebrates.

These include chiefly various polychaetes, specifically the family Siboglinidae (beard worms), Serpulidae, and related families of the order Canalipalpata. Other groups also called tube worms include members of the phylum Phoronida (horseshoe worms).

It may also refer to the bright red worms found living at the bottom of the ocean near active sulfur vents. These worms live in huge colonies clumped together around the hydrothermal vents.

o. Oyster

The common name oyster is used for a number of different groups of bivalve mollusks, most of which live in marine habitats or brackish water. The shell consists of two usually highly calcified valves which surround a soft body. Gills filter plankton from the water, and strong adductor muscles are used to hold the shell closed.

Some of the groups known as oysters, also known as mullusks (true oysters), are highly prized as food, both raw and cooked (though the Bible categorizes them as unclean, and therefore unfit as human food). Some other groups also called oysters, such as pearl oysters, are not widely eaten, at least not since recent times.

True (edible) oysters are incapable of making gem-quality pearls, although the opposite idea is a commonly-encountered misapprehension, often seen in illustrations or photographs where an edible oyster shell is mistakenly paired with a gem-quality pearl.

The oyster is used as a metaphor in an idiomatic saying, "The world is your oyster", which means that the whole world is laid out before you like a wonderful living buffet.

p. Amphipod (Sand Flea)

Amphipoda (amphipods) is an order of animals that includes over 7,000 described species of small, shrimp-like crustaceans.

Most amphipods are marine; although a small number of species are limnic or terrestrial. Marine amphipods may be pelagic (living in the water column) or benthic (living on the ocean bottom). Pelagic amphipods are eaten by seabirds, fish, and marine mammals. Terrestrial amphipods such as sand fleas can often be seen amongst sand and pebbles or on beaches.

q. Sponge

The sponges or poriferans (from Latin porus "pore" and ferre "to bear") are animals of the phylum Porifera. Porifera translates to "Pore-bearer". They are primitive, sessile, mostly marine, water dwelling filter feeders that pump water through their bodies to filter out particles of food matter. Sponges represent the simplest of animals. With no true tissues (parazoa), they lack muscles, nerves, and internal organs. Their similarity to colonial choanoflagellates shows the probable evolutionary jump from unicellular to multicellular organisms. There are over 5,000 modern species of sponges known, and they can be found attached to surfaces anywhere from the intertidal zone to as deep as 8,500 m (29,000 feet) or further. Though the fossil record of sponges dates back to the Neoproterozoic Era, new species are still commonly discovered.

r. Sand Dollar

Sand dollars are in the Echinoid (Echinoderms) class of marine animals. When they are living, they are covered with a suit of moveable spines that encompass the entire shell. Like its close relative the sea urchin, the sand dollar has a set of five pores arranged in a petal pattern. The pores are used to move sea water into its internal water-vascular system, which allows the creature to move.

Sand dollars live beyond mean low water on top of or just beneath the surface of sandy or muddy areas. The spines on the somewhat flattened underside of the animal allow it to burrow or to slowly creep through the sand. Fine, hair-like cilia cover the tiny spines. Tubefeet or podia that line the food grooves, move food to the mouth opening which is in the center of the star shaped grooves on the underside of the animal called the oral surface. Its food consists of crustacean larvae, small copepods, detritus, diatoms, algae and organic particles that end up in the sandy bottom.

On the ocean bottom, sand dollars are frequently found together. This is due in part to their preference of soft bottom areas, which are convenient for their reproduction. The sexes are separate and, as with most echinoids, gametes are released into the water column. The free-swimming larvae metamorphose through several stages before the skeleton or test begins to form, and they become bottom dwellers.

The name "sand dollar" is a reference to their round flat shape, which is similar to a large coin.

The term "sand dollar" can also refer to the test left when a sand dollar dies. By the time the test washes up on the beach, it is usually missing its velvety covering of minute spines and has a somewhat bleached appearance due to its exposure to the sun.

In 2008, scientists showed that sand dollar larvae can clone themselves as a mechanism of self defense. Larvae exposed to mucus from predatory fish cloned themselves, effectively halving their size. The smaller larvae are believed to better escape detection from fish predators, but may increase the danger of predation from smaller animals, such as crustaceans.

s. Coral

Corals are skeletal remains of marine organisms from the class Anthozoa and exist as small sea anemone–like polyps, typically in colonies of many identical individuals. The group includes the important reef builders that are found in tropical oceans, which secrete calcium carbonate to form a hard skeleton.

A coral "head", commonly perceived to be a single organism, is actually formed of thousands of individual but genetically identical polyps, each polyp only a few millimeters in diameter. Over thousands of generations, the polyps lay down a skeleton that is characteristic of their species. A head of coral grows by asexual reproduction of the individual polyps. Corals also breed sexually by spawning, with corals of the same species releasing gametes simultaneously over a period of one to several nights around a full moon.

Although corals can catch plankton using stinging cells on their tentacles, these animals obtain most of their nutrients from symbiotic unicellular algae called zooxanthellae. Consequently, most corals depend on sunlight and grow in clear and shallow water, typically at depths shallower than 60 m (200 ft). These corals can be major contributors to the physical structure of the coral reefs that develop in tropical and subtropical waters, such as the enormous Great Barrier Reef off the coast of Queensland, Australia. Other corals do not have associated algae and can live in much deeper water, such as in the Atlantic, with the cold-water genus Lophelia surviving as deep as 3000 m. An example of these are the Darwin Mounds located north-west of Cape Wrath, Scotland. Corals have also been found off the coast of Washington State and the Aleutian Islands in Alaska.

t. Ghost Crab

Ghost crabs, also called sand crabs, are crabs of the genus Ocypode, common shore crabs in many countries. In the eastern United States, Ocypode quadrata is frequently seen scurrying along beaches between sunset and dawn.

These crabs are called ghosts because of their ability to disappear from sight almost instantly, scuttling at speeds up to 10 miles per hour, while making sharp directional changes. These creatures have two black eyes, with sharp 360° vision which they use to see flying insects and catch them in mid air. The ghost crab, however, cannot see directly up, so it must burrow into the ground to prevent birds from catching it.

The ghost crab tunnels down four feet into the ground at a 45° angle, creating 1-2 inch wide holes, which speckle the beach. At dusk, these crabs will sprint to the ocean in order to obtain oxygen from the water which washes over their gills, and in June, females will release their eggs into the ocean. Ghost crabs hibernate during the winter, holding their breath for six months, by storing oxygen in sacs near the gills. They can also have a natural filter system which gathers oxygen from the air humans breathe, enough to survive for one year without entering into water.

The common ghost crab or smooth-handed ghost crab (Ocypode cordimana) is found on the northern Australian coast from the Kimberley region of Western Australia to New South Wales, being particularly common in New South Wales. It is also found in the Indo-Pacific region.

Characteristics of the genus include one claw being larger than the other, but not as profoundly as for the male fiddler crab.

3. Describe the following processes:

a. The swimming action of a sea jelly

Most jellyfish are passive drifters and slow swimmers, as their shape is not hydrodynamic. Instead, they move so as to create a current forcing the prey within reach of their tentacles. They do this by rhythmically opening and closing their bell-like body.