Marine

Invertebrates

Phylum Porifera: Sponges

1. Non-moving (sessile) animals

2. No nerves or muscles (no tissue differentiation)

3. Mostly marine

4. Filter feeders: Collect food particles from water

5. Most sponges are hermaphrodites. Hermaphrodites

function as both male and female in sexual reproduction by

producing eggs and sperm.

**All other animals have true tissues

Animals probably

evolved from

colonial,

flagellated

protists, like this

choanoflagellate

colony.

Cnidarians

•Polyp and medusa forms of cnidarians.

•Radial symmetry with central digestive (gastrovascular)

cavity.

•One opening in the gastrovascular cavity serves as both

mouth and anus.

•Carnivores.

•Phylum name comes from specialized cells called

cnidocytes.

•Cnidocytes are stinging cells used for defense and to

capture prey.

Purple striped jelly, Pelagia panopyra

Polyps: Sea anemones

Phylum Ctenophora

•The Comb jellies

•Resemble cnidarian

medusas.

•Use cilia for

locomotion.

Phylum Platyhelminthes: Flatworms

•Sizes range from microscopic up to 20 meters long

(tapeworms).

•Many are parasites.

Class Turbellaria (flatworms)

• Mostly free-living (non-parasitic)

• Feed on small animals, dead animals

•Very flat for O2 exchange. They have no gas exchange

organs.

Classes Trematoda

Live as parasites

Trematodes parasitize vertebrates.

(For example, humans but often with intermediate hosts)

The life history

of a blood fluke

(Schistosoma

mansoni).

Class Cestoidea – Tapeworms

•Live as parasites

•Head contains suckers and hooks that lock onto the intestinal

lining of the host.

•The rest of the body is mostly units called proglottids that are

sex organs.

• Eggs transferred to new hosts by consuming fecal

contaminated water.

Anatomy

of a

tapeworm

Phylum Rotifera: Rotifers

•Aquatic

•Sizes range from 0.5 to 2 mm

•Complete digestive tract

A rotifer

Lophophorate Phyla: Bryozoans, Phoronids, & Brachiopods

All of these groups have a lophophore.

The lophophore is a horseshoe shaped fold near the mouth

that is surrounded by ciliated tentacles.

Bryozoans resemble mosses.

- They have a hard exoskeleton.

- They are important as reef builders.

Phoronids are marine worms.

Brachiopods resemble clams.

A bryozoan

A brachiopod

Phylum Nemertea: Proboscis (ribbon) worms

Up to 30 meters in length

These worms have a hydraulically-operated proboscis that is

used to capture prey.

Closed circulatory system.

Nemertea – Proboscis worms

Phylum Mollusca: Mollusks

Snails, clams, octopi, squids, oysters

There are at least 150,000 known species

All mollusks have similar body plans:

a. Muscular foot

b. Visceral mass with organs

c. Mantle that secretes the shell

Bivalvia

Shells divided into

two parts.

Gills are used for

feeding and gas

exchange.

Example:

Clams, oysters

Dreissena polymorpha

Zebra mussel

Cephalopoda

Rapid movement; well-developed nervous systems.

Example: Octopus, squid, nautilus

Phylum Annelida: Segmented worms

Sizes range from 1 mm to 3 meters in length.

Each segment contains a pair of excretory tubes called

metanephridia.

Annelids are hermaphrodites that cross-fertilize.

Three classes:

a. Oligochaeta – earthworms

b. Polychaeta – mostly marine

c. Hirudinea – leeches

Protostomia: Ecdysozoa

Phylum Nematoda: Roundworms

Non-segmented

Some are important parasites of animals.

Pinworms and hookworms, e.g., Trichinella, obtained by

eating undercooked pork; juveniles infect all body organs

and tissues.

Nematodes

Phylum Arthropoda: Arthropods (crustaceans, spiders, insects)

Hard exoskeleton, segmented bodies, jointed appendages

Arthropods are the most successful of all animal phyla based on diversity,

distribution, and numbers.

Nearly one million species identified so far, mostly insects.

The exoskeleton, or cuticle, is composed of protein and chitin.

Molting of the cuticle is called ecdysis.

Extensive cephalization.

Open circulatory systems in which a heart pumps hemolymph through short

arteries and into open spaces (sinuses).

Aquatic members- gills for gas exchange; terrestrial members- tracheal

system of branched tubes leading from surface throughout body.

Four evolutionary arthropod lineages

a. Trilobites – extinct

b. Chelicerates – horseshoe crabs, spiders

c. Uniramians – centipedes, millipedes, insects

d. Crustaceans – crabs, lobsters, barnacles

From these lineages arose five major classes of

arthropods.

Insecta (insects)

Outnumber all other forms of animals.

Evolved flight during Carboniferous period. Flight was

followed by an explosion of diversity.

Coevolution of flowering plants and insects.

Wings are extensions of the cuticle.

Waste is removed from hemolymph by excretory organs

called malpighian tubes.

Nervous system has a pair of ventral nerve chords that join in

the head to form a cerebral ganglion (brain) that is close to

the sensory organs in the head (cephalization).

Note: Many insects undergo metamorphosis during their

development.

Incomplete metamorphosis is a process whereby the young

look like the adults, but have different body proportions.

Complete metamorphosis is a process where the larval

stages (larva, maggot or grub) are specialized for eating.

•The adult stage is specialized for reproduction and

dispersal (e.g. flight).

•The process of metamorphosis occurs during a pupal

stage.

Class Crustacea

E.g., crabs, lobsters

Almost all are aquatic.

Ca. 40,000 species.

Includes krill eaten by

whales, and daphnia,

copepods, & amphipods in

Lake Erie, pill bugs, etc.

Deuterostomia: Phylum Echinodermata (Echinoderms)

Water vascular systems – network of hydraulic canals used

for locomotion, feeding, and gas exchange. It extends into

tube feet that are used for locomotion and feeding.

Echinoderms appear to be radial, but are bilateral in larval

stages.