UNIT 6 INVERTEBRATES PART 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 Sponges example: Leucoselenia (Class Calcispongiae)

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

The Syconoid Sponges example: 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 Sponges example: 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

Medusaes have a statocysts that give them a sense of balance 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 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

Physophora hydrostatica Man-o-war www.alienstingers.com/.../group_siphono_b.gif

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 Corals limestone skeletons multiple tentacles Soft Corals soft skeleton with spicules 8 tentacles chemical repellents

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