Lab 2 Lophotrochozoa (10 Phyla)

The Lophotrochozoa are bilateral animals. Several phyla within the Lophotrochozoa have trochophore larvae (Nemertea, Mollusca, Sipuncula, Echiura, Pogonophora, Annelida), and several have a lophophore, a ring of tentacles encircling the mouth (Bryozoa, Entoprocta, Phoronida, Brachiopoda).

1. Phylum Sipuncula The Sipuncula (which means little siphon) are known as the "peanut worms." Sipunculans occur in shallow water marine habitats where they either burrow into sand, mud, or rock, or live in crevices between rocks or in empty shells. This phylum has 144 described species.

Features of a Sipunculan worm

Pictures courtesy of BIODIDAC

Classification: The Phylum Sipuncula is divided into two classes: the Class Sipunculidea and the Class Phascolosomatide.

Morphology: Sipuncula are un-segmented and worm-like in appearance

Fossil Record: The fossil record of Sipuncula is sparse, but they maybe Paleozoic (543 my bp) in origin.

Read more about Sipuncula on the UCMP website

Sipuncula on the Tree of Life Web site

2. Phylum Mollusca The Mollusca is a large Phylum with over 50,000 described species. The Mollusca is primarily marine, but also occur in freshwater and in terrestrial habitats. The Mollusca includes clams, snails, squid, octopus, tusk shells, and chitons, among others. The majority of Mollusca have some sort of calcareous shell, although some groups have greatly reduced or lost their shells (squid, nudibranchs). The Mollusca have a planktonic larval stage.

Bivalvia

Cephalopoda

Gastropoda

Polyplacophora

Scaphopoda

Pictures courtesy of BIODIDAC

Classification: The Mollusca is divided in seven classes: the Cephalopoda (squid, octopus 600 species), the Gastropoda (Snails, whelks, nudibranchs - 30,000 species), the Bivalvia (clams, oysters - 10,000 species), the Scaphopoda (tusk shells - 350 species), the Monoplacophora, the Polyplacophora (chitons - 800 species), and the Aplacophora.

Morphology: Molluscs are bilaterally symmetrical and most species have some sort of calcareous exoskeleton or shell. Molluscs have a well developed head region with a muscular foot adjacent to the head. All groups except the Bivalvia and the Aplacophora have a radula, a feeding organ that may be used for rasping, stabbing, tearing, cutting, or drilling. The form of the molluscan shell is quite diverse and its shape can be described by a simple mathematical model that can generate any of these shell forms (click here - to try out this model and see what kind of molluscan shell you can build).

Fossil Record: Cambrian (543 - 490 my bp).

Read more about Mollusca on the Animal Diversity Web

More on the Mollusca and the Raup model of Molluscan growth

More Mollusca with pictures on the Washington State Natural History Museum

More on Mollusca at the University of Texas at Austin

Link to the Biosis list of web resources on Mollusca (dozens of link)

Read more about Scaphopoda on the UMCP website

3. Phylum Nemertea The Nemertea are known as the ribbon worms because they are long and thin, some species reaching 30m in length! Most Nemertea occur in marine habitats, but there are a few freshwater and terrestrial species. There are approximately 900 described species of Nemertea.

Nemertea with proboscis everted

Pictures courtesy of BIODIDAC

Classification: The Nemertea are divided into two classes: Class Anopla and Class Enopla.

Morphology: Nemertea are long thin worms with an eversible proboscis used in prey capture. The proboscis is everted and toxins are secreted to capture and subdue prey.

Fossil Record: The fossil record for Nemertea is very sparse. However, they are thought to date from the Cambrian (543- 490 my bp)

Read more about Nemertea on the UCMP web site (good pictures)

Enter the Nemertea web portal

Nemertea at the California Academy of Sciences web site

Nemertea on the Tree of Life web site

4. Phylum Bryozoa The Bryozoa are also called moss animals or Ectoprocts. Bryozoa occur in marine and freshwater habitats. Most Bryozoans are hermaphroditic. Approximately 5,000 described species of Bryozoa are extant.


	Lophophore and body	Plumatella - Zooarium of a
Colony of Bugula sp.	of a freshwater Bryozoan	freshwater Bryozoan

Pictures courtesy of BIODIDAC

Classification: The Bryozoa is divided into three classes: Class Stenolaemata, Class Gymnolaemata, and Class Phylactolaemata.

Morphology: Bryozoans are colonial organisms composed of multiple zooids. Zooids are usually no more than a millimeter in length, but Bryozoa colonies range from a few millimeters to meters in size. Each zooid has lophophore or a ring of tentacles on the head that serve in feeding. Zooids are enclosed in a tunic composed either of chitin or calcium carbonate.

Fossil Record: Extensive fossil record, Ordovician (490 my bp)

Bryozoa at the UMCP web site

The Bryozoa homepage

Bryozoa at the Smithsonian Fort Pierce, Florida lab

The International Bryozoolgy Association web site

Bryozoa on the Tree of Life web site

More on Brach net

8. Annelida - The Annelida are segmented worms that include the earthworms, polychaete worms, and leeches. The Annelida have setae sometimes located on paddle like appendages called parapodia. There are approximately 9,000 described species of Annelida. Annelida are marine, freshwater, and terrestrial in distribution and may also be either internal or external parasites of other animals.

Hirudinea - External features of a leech Oligochaeta - Lumbricus terrestris

Suspension feeding by a Suspension feeding by a

Sabellid polychaete Sabellid polychaete

Pictures courtesy of BIODIDAC

Classification: The Annelida is divided into five classes: Class Archiannellida (microscopic annelid that have loss annelid traits such as chaetae and segmentation), Class Hirudinea (the leeches), Class Oligochaeta (the earthworms), Class Polychaeta (lugworms, polychaetes, sandworms, and rugworms), and Class Myzostomaria (parasites of Echinoderms).

Morphology: The Annelida are segmented worms that may have setae on paddle like extensions of the body called parapodia. The number of setae is reduced in the earthworms and leeches compared to the Polychaeta.

Fossil Record: There are definite Cambrian fossils (543-490 my bp), but the Annelida probably originated in the Pre-Cambrian.

Read more on Annelida on the UMCP web site

Read more on Annelida on the Animal Diversity Web

Annelida on the Tree of Life web site

9. Echiura The Echiura are also known as the "spoon worms." There are 150 described species of Echiura that occur in marine habitats. Echiura occupy burrows in mudflats where they filter water and capture planktonic organisms with a mucous net created by their proboscis.

Pictures courtesy of BIODIDAC

Classification: The Echiura is sometimes classified within the Annelida. They are divided into three classes: Class Echiuroidea, Class Heteromyota, and Class Xenopneusta.

Morphology: The Echiura are unsegmented worms with an extensible proboscis and small hooks on the posterior end.

Fossil Record: Trace fossils of u-shaped burrows date from the Cambrian, but the earliest actual fossils of Echiura are from the Upper Carboniferous.

Read more on Echiura on the UMCP web site

Echiura on the Animal Diversity Web

10. Pogonophora The Pogonophora are deeps sea dwelling tube-worms that can reach 2 meters in length. They include the vent worms that are sometimes classified into a separate phylum the Vestimentifera. There are approximately 80 described species of this exclusively marine group.

External features of a Pogonophora - anterior end with

Pogonophoran worm tentacles and cephalic lobe

Pictures courtesy of BIODIDAC

Classification: ?

Morphology: The body of Pogonophorans is divided into a segmented posterior end (opisthosoma) that resembles an annelid and a non-segmented anterior end (prosoma). The Pogonophora have no gut or digestive track. They receive the bulk of their nutrition from symbiotic bacteria that live in a specialize organ called the trophosome. The bacteria oxidize sulfur-containing compounds, which are absorbed from the water through the surface of the tentacles. The bacteria obtain their energy from the oxidation of sulfur and fix carbon into organic molecules, which provide the nutrition for their Pogonophoran host.

Fossil Record: Tubes that appear to be from Pogonophora occur in the Precambrian (650-543 my bp).

Read more on Pogonophora on the UMCP web site

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Lab 2 Exercise

Task #1 - Choose 6 of the phyla of lophotrochozoans and construct a dichotomous key.

Task #2 - When we go to the Pigeon Point tidepools we are likely to see members of the phylum Mollusca and other lophotrochozoan phyla. Use a field guide, California natural history book, or the internet (key words: California, intertidal and the phylum or class name) to answer the following questions. Indicate where you got the information using the Name-Year method with a list of references described in Lab 1. A single source is adequate.

- List three species in three different classes of Mollusca plus one species of another of the above phyla that we might find there. Use the binomial names (two words - the genus, which begins with a capital letter, and the specific epithet, which is not capitalized; both words italicized).

- For each species indicate what class of the phylum Mollusca it is in.

- For each species indicate what and how it eats.

Task #3 - Field journal exercise. Find a lophotrochozoan (hint: mollusc and annelid species can easily be found in your yard or on campus) and fully describe the individual. Size (you will need a ruler), color, shape, texture, appendages, and behavior are necessary for a complete description. Begin your description with a heading that includes the date, time and location of the observation, the weather, and a description of the habitat in which it was found. In addition, make two drawings of different scales (the entire animal and a closeup) of your organism. You will not be graded on your skills as an artist, only your skills as an observer.

Turn in exercise by February 27.