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