UNIT 6 INVERTEBRATESPART 1

SPONGES; CNIDARIANS; CTENOPHORES; PLATYHELMINTHES; NEMERTEA; NEMATODA; ANNELIDA; SIPUNCLA; ECHIURANS; MOLLUCS;

The following is a website that I found of photographs, videos, and species identification of organisms around Australia.

http://www.julianrocks.net/index.htm

Animals classified into two main groups: Vertebrates: those having backbones Invertebrates: those that do not have a

backbone (97% of all animal species) Most marine or aquatic except for the insects

SPONGES (Phylum Porifera)

Most simple multicellular animal Organized on the cellular level- no true

tissues or organs; the cells are independent of each other

Almost all marine All are sessile (permanently attached to a

surface) video

Suspension feeder- eat food particles suspended in water

Filter feeder- filter food particles

The basic body form of all sponges is a sac-like structure consisting of three layers – an outer layer of epidermal cells an inner layer of cells, many of which are flagellated

cells called choanocytes a middle layer of amoeboid cells that form skeletal

structures of various sorts. These layers are perforated by a large number of small pores (thus the name Porifera). The cavity of this sac is called the spongocoel and has at least one opening to the outside, called an osculum

The skeletons of sponges can be composed of an organic substance called spongin (the stuff of an ordinary bath sponge), or they may have calcareous or siliceous skeletons composed of chambers, or more commonly rod-like branched elements called spicules. After death, spicules are scattered across the sea floor and may be found as disarticulated microfossils.

link

The poriferans (sponges) are characterized by cell groups that are independent of each other and have the ability to change their function during their life cycle.

The skeletons of sponges can be composed of an organic substance called spongin (the stuff of an ordinary bath sponge), or they may have calcareous or siliceous skeletons composed of chambers, or more commonly rod-like branched elements called spicules.

After death, spicules are scattered across the sea floor and may be found as disarticulated microfossils.

3 basic types of sponges

The Asconoid Spongesexample: Leucoselenia (Class Calcispongiae)

Asconoid sponges have the simplest organization. Choanocytes line the spongocoel, drawing water through small ostia and expelling it through the osculum.

The Syconoid Spongesexample: Scypha (Class Calcispongiae)

Syconoid sponges have a tubular design similar to the ascon sponge, but the body wall is folded. The "folds" form radial canals. Choanocytes line the radial canals rather than the spongocoel.

This shows the radial canals

The Leuconoid Spongesexample: the "bath sponge" (Class Demospongiae)

.

Leuconoid sponges represent the most complex body form.

The canal system is extensively branched. Small incurrent canals lead to flagellated chambers lined by choanocytes. Flagellated chambers discharge water into excurrent canals that eventually lead to an osculum.

Usually there are many oscula in each sponge. The skeleton of this sponge is made of a soft protein,

called spongin, rather than calcium carbonate or silica

Link to sponge photos

REPRODUCTION

ASEXUAL: branches or buds break off SEXUALLY: produce gametes in specialized

collar cells or amebocytes MOST HERMAPHRODITIC BROADCAST SPAWNING- release of sperm

into the water; eggs remain inside the body and fertilization is internal

Development inside sponge; a planktonic larva called a parenchymula larva

metamorphosis

CNIDARIANS

video

Basic characteristics

Tissues evolved to perform certain functions Also called coelenterates Ex: sea anemones, jellyfishes, coral Radial symmetry (similar body parts arranged

and repeated around a central axis) Looks the same from all sides; no head, front

or back Oral surface = where mouth is Aboral surface = side without mouth

Basic characteristics cont. Centrally located mouth surrounded by

tentacles that capture and handle food Mouth opens into a gut where food is

digested Have nematocysts (or cnidae) that are

specialized cells that discharge poison to help maintain food

Feeding and digestion: carnivores; initial phase of digestion is said to be extracellular because it takes place outside cells; intracellular digestion within cells lining the gut complete the food breakdown

http://undersea.com.au/corals/coral_structure.htm

Behavior- have specialized nerve cells which interconnect to form a nerve net that transmits impulses in all directions

Medusaes have a statocysts that give them a sense of balance Small calcareous bodies in fluid-filled

chambers with small hairs

2 basic forms

1. Polyp= sac-like life stage with mouth and tentacles

2. Medusa= bell-like; jellyfish; upside down polyp

Some animals exhibit both stages in their life; others exhibit only 1 kind throughout their life

Larvae = planula- a cylindrical ciliated stage made of two cell layers; planktonic until it settles on the bottom

Cell layers of Cnidaria

2 layers form the body wall Epidermis- external Gastrodermis- lines the gut

Mesoglea- narrow; gelatinous middle layer that contains no cells In a medusa, the layer is expanded to form a

gelatinous, domed bell

CLASSES OF CNIDARIANS

10,000 known species 1. Hydrozoans- wide range of forms

A. Siphonophores- form drifting colonies of polyps Ex: Portuguese man-of-war; some of the colony are

specialized as floats Some contain droplets of oil Some form long tentacles to capture prey Reproduction- varies; some have specific reproductive

polyps that release gametes and fertilization takes place and develops into swimming planulae that settles on the bottom and develops into a polyp which divides into interconnected polyps

Marrus orthocanna, a deep sea siphonophore. The combined digestive and circulatory system is red; all other parts are transparent.

www.siphonophores.org/images/2729_600.jpg

www.alienstingers.com/.../group_siphono_b.gif

Man-o-warPhysophora hydrostatica

image48.webshots.com/.../377734356ljKMfl_ph.jpg

Most Hydrozoans are feathery or bushy colonies of tiny polyps.

2. Scyphozoans- larger jellyfish Large medusa dominant life stage Reproduction: polyps are small; release

juvenile medusas Some bell’s may reach a diameter of 2 m; a

just discovered one that is 3 m Swim w/a rhythmic contraction of the bell;

easily carried by currents Can be very dangerous; fatal stings

Aurelia aurita (moon jelly)

3. Cubozoa- most toxic Ex: sea wasp- box jellyfish Death due to heart failure There is an antivenom

The box jellyfish,  or sea wasp (Chironex) that swims in tropical waters off the coast of Australia with a width of approximately 25 cm can kill a person within minutes! 

bioweb.uwlax.edu/.../Lab_3a-07a.jpg

Carybdea

4. Anthozoans- solitary or colonial polyps that lack a medusa Largest number of Cnidarian species More complex body

Gut has several thin partitions called septa that increase the surface area for digestion and provide support allowing the polyp to be larger

Ex: sea anemones; corals

www.anthozoa.com/Photos/Welcome/Anthozoans.jpg

CORALS-

HERMATYPIC- corals where the polyps produce calcium carbonate skeletons; form reefs

AHERMATYPIC- corals who do not help to build reefs

Scleractinian corals- most important reef builders; also known as stony or “true” corals

Contain symbiotic zooanthellae (dinoflagellates) that help the corals make their calcium carbonate skeletons

The coral polyp

Reefs are colony of polyps connected with a thin layer of tissue

Starts when a planktonic coral larva, called a planula, settles on a hard surface and metamorphoses into a polyp which divides over and over to produce the colony

Digestive systems remain connected and share a common nervous system

Only living tissue is a thin layer on the surface

Hard Coralslimestone skeletonsmultiple tentacles

Soft Coralssoft skeleton with spicules8 tentacleschemical repellents

Gorgonians- sea fans; colonial anthozoans Precious corals and black corals are made

into jewelry

carlsafina.files.wordpress.com/2009/01/a-shal...

CTENOPHORES

COMB JELLIES-video

All marine 100 species Radially symmetry and gelatinous body Swim with 8 rows of CILIARY COMBS, long

cilia fused at the base that beat in waves reflecting light

In warm and cold waters COLLOBLASTS- long tentacles armed with

sticky cells

www.mwra.state.ma.us/.../graphic/ctenophore.jpg

Comb jelly

BILATERALLY SYMMETRICAL WORMS

FLATWORMS, RIBBON WORMS, NEMATODES, SEGMENTED WORMS-

VIDEO

FLATWORMS

Phylum- Platyhelminthe Dorsoventrally flat Simplest animals with tissues organized into

real organs and organ systems Have a central nervous system

Simple brain- bundle of nerve cells Several nerve cords the length of the worm Only one opening for gut/anus

Embryos have a middle layer of tissue called the MESODERM (1st animal to have it)- which gives rise to muscles, the reproductive system, and other organs

20,000 species Most common marine ones are the

TURBELLARIANS- free living carnivores

www.daviddarling.info/images/flatworm_section.jpg

Polyclad flatworm, Pseudoceros sp, Egyptian Red Sea. Photo © Mike Keggen

http://www.julianrocks.net/flatworms/PseudobicerosBedfordi.html

FENCING

Flukes or TREMATODES- largest group of flatworms; 6000 species; all parasitic

Tapeworms or CESTODES- long body with repeating units; live in intestines of vertebrates; don’t have a gut or mouth but absorb nutrients

RIBBON WORMS

Or NEMERTEAN More complex organization Complete digestive tract with gut, mouth, and

anus Circulatory system Proboscis-long fleshy tube used to entangle

prey Predators that feed on worms and

crustaceans 900 species mostly marine

http://rydberg.biology.colostate.edu/Dissections/Nemertea/Nemerteawh.JPG

Nematodes

Roundworms Found mostly in sediment or intestinal tracts;

most parasitic; small, with slender body that is pointed at one end

Gut and anus Has a hydrostatic skeleton- a system that

uses water pressure against the body wall to maintain body shape and aid in locomotion

Anywhere between 10,000 to 25,000 species Larvae found in raw or poorly cooked fish

http://www.diplectanum.dsl.pipex.com/sim/anisak.jpg

SEGMENTED WORM OR ANNELIDS About 20,000 species More complex body systems Has segmentation- identical body segments Has a coelom-body cavity found in

structurally complex animals- completely surrounded by tissue developed from the mesoderm

Classes of Annelids

1)Polychaetes- most of the marine annelids;made of body segmetnns that have a pair of flattened extensions called parapodia that have setae (sharp bristles) Have a closed circulatory system that

transports nutrients, oxygen, and carbon dioxide

Have gills on the parapodia that contain capillaries to help with the absorption of oxygen

10,000 species almost all marine Live in temporary or permanent tubes made of

mucus, protein, seaweed bits, mud, etc. Mostly carnivores but some are suspension

feeders Proboscis ensnares prey

Life history of Polychaetes Have a trochophore- a planktonic larval stage

with cilia Some such as the Tomopteris are planktonic for

entire life

http://www.esu.edu/~milewski/intro_biol_two/lab__12_annel_arthro/images/nereis.jpg

Nereis

An assemblage of polychaetes (Photo by H. Torres)

2) Pogonophorans or beard worms- Lack a mouth and gut Has food absorbing tufts 135 species Deep water Another group called the vestimentiferans

are much longer Some found at hydrothermal vents

www.nematodes.org/.../pogonophora/pogo1.gif

3)Oligochaetes- found in mud and sand; eat detritus;marine relatives of earthworms; no parapodia

http://www.mpi-bremen.de/Binaries/Binary7687/Oalg_7_RGB_small.jpg

4.) Leeches- some marine species; parasitic; sucker at one end; no parapodia

Tracy Clark 8/11/2006

La Jolla ShoresHornyhead Tubot

Pleuronichthys verticalisLeech

UnidentifiedNikon D7060mm lens

PEANUT WORMS

Phylum: Sipuncula Unsegmented bodies Burrowers; shallow water; deposit feeders All marine Long, anterior portion has a mouth a a set of

small lobes of branching tentacles 320 species

http://www.livewild.org/CostaRica/Pics/a5751.jpg

ECHIURANS- phylum Echiura

135 species all marine Look like peanut worms but with a non-

retractable, spoon-like or forked proboscis Deposit feeders Some live in U-shaped tubes in the mud

http://farm4.static.flickr.com/3089/2922855838_a3df563b1e.jpg?v=1223412990

Molluscs: The Successful Soft Body

BASIC MOLLUSK CHARACTERISTICS Most have a soft body enclosed in a calcium

carbonate shell Body covered with a mantle- a thin layer of

tissue that secretes the shell Bilaterally symmetrical Ventral, muscular foot Head with sensory organs including eyes Have a radula- ribbon-like band of teeth

made of chitin used for feeding Have paired gills

3 major classes of Mollusks

Gastropods (class Gastropoda) Bivalves (class Bivalvia) Cephlapods (class Cephlapodia) 2 minor classes of Mollusks:

Chitons Tusk shells

Gastropods “stomach footed”

Largest and most common class Snails, limpets, abalones and nudibranches 75,000 species mostly marine Has a hard dorsal shell Use radula to scrape algae from rocks Some are deposit feeders; some are

carnivores Nudibranches or sea slugs have no shell

Nudibranch

http://birdhouse.org/blog/wp-content/uploads/2008/05/nudibranch.jpg

Limpet

www.barwonbluff.com.au/.../limpet%20smooth.jpg

limpet

www.theseashore.org.uk/theseashore

coneshell

http://www.scuba-equipment-usa.com/marine/JUN05/images/Conus_textile.jpg

Violet snails

http://www.floridastateparks.org/bahiahonda/images/BAH-violet-snail.jpg

BIVALVES

Clams,mussels,oysters etc. Body is laterally compressed and enclosed in

a shell with two parts No head, no radula Gills larger and used for obtaining oxygen

and to filter food particles Inner surface of shell lined by mantle;

therefore whole body is in the mantle cavity- a large space between the two halves of the mantle

Siphons-tube-like extension through which water flows in and out of the mantle cavity in bivalves, cephlapods, and tunicates

Mussels have byssal threads to attach to submerged surfaces such as rocks etc.

http://www.japan-hopper.com/wp-content/photos/pearl_oyster.jpg

Pearl oyster

Pearl diving video

www.waterworxbali.com/.../giant-clam-diver.jpg

Giant sea clam…largest bivalve can be up to 3ft in length

Some bivalves bore into coral, rock or wood Ex: shipworm– known as a fouling organism

because they settle on the bottom

CEPHLAPODA- “head-footed”

Predators Octopuses, squids, cuttlefishes Reduced or absent shell Foot modified into arms and tentacles with suckers Round bodies- octopus Elongated bodies- squid Bodies protected by thick, muscular mantle Mantle cavity behind head contains 2-4 gills Siphon = funnel- a muscular tube from the foot