Szivacsok, korallok

Porifera - szivacsokArchaeocythaCnidaria - csalánozók

pp. 208-218

Phylum Porifera - Sponges

• Mostly marine, but include some freshwater inhabitants; usually found attached to the substratum in shallow or deep water.• They are sessile; permanently attached to the substrate• Obtain their food by filter feeding

General Morphology • The internal cavity is called the atrium or spongocoel• Water is drawn into it through a series of incurrent pores or dermal ostia present in the body wall into a central cavity and then flows out of the sponge through a large opening at the top called the osculum

Body layers

1. The pinacoderm - an outer layer of flattened cells called pinacocytes2. An inner lining containing flagellated cells (choanocytes) - draw water in through the pores and move out through the osculum; also trap food particles that are suspended in the water.• The water current is also used for gas exchange, removal of wastes, and release of the gametes3. Between the pinacodern and the choanocytes is a gelatinous material called mesohyl; contains several different kinds of wandering cells called amoeboid cellsArchaeocytes are amoeboid cells that phagocytize food particles; they can also undergo differentiation to form other cells, including cells that produce spicules and gametes

The Skeleton

In the mesohyl is the skeleton composed of tiny pointed structures made of silica or calcium carbonate called spicules.These structures act as an internal scaffolding, but also function in protectionAmong some sponges the skeleton consist of spongin fibers made of collagenous material; found in many of the commercial sponges

Types of Sponges (Canal Systems)

A. Asconoid Sponges

• Simple vaselike structure• This stucture puts limitations on size; (increase in volume without a corresponding increase in the surface area of the choanocytes)

Types of Sponges (Canal Systems) cont.

B. Synconoid Sponges

• The flagellated choanocyte layer has undergone folding forming finger like projections• There is a single osculum but the body wall is more complex, with water being received through incurrent canals, which pass it along to radial canals through to the spongocoel• Results in an increase in the surface area which allowed sponges to increase in the size

Types of Sponges (Canal Systems) cont.

C. Leuconoid Sponges

• No atrium; several small chambers in which choanocytes are located • There is a whole series of incurrent canals leading to the choanocyte chambers; water is discharges through excurrent canals• The leuconoid sponges exhibit a significant increase in surface area and are, therefore, among the largest sponges

Szivacsok test-típusai

ascon sycon leucon

Sponge Reproduction

• Most are hermaphroditic or monoecious.• Sperm leaves a sponge via the osculum, and enters a sponge by the currents generated from the choanocytes.Fertilized eggs develop into ciliated free-swimming larvae called parenchymula larvae• Sponges can reproduce asexually by fragmentation

• Many of the freshwater sponges can produce asexual bodies called gemmules, aggregations of cells that are enclosed in hard outer covering containing spicules

Sponge Taxonomy

Class Calcarea (Calcispongidae)

• Only sponges that possess spicules composed of calcium carbonate. • Spicules are straight or have 3-4 rays, and do not have hollow axial canals. • Today, their diversity is greatest in the tropics, predominantly in shallow waters

Taxonomy cont.

Class Hexactinellida (Hyalospongiae)

• Glass sponges; characterized by siliceous spicules consisting of six rays intersecting at right angles• Widely viewed as an early branch within the Porifera

Taxonomy cont.

Class Demospongiae

• Greater than 90 percent of the 5,000 known living sponge species are demosponges.• Demosponge skeletons are composed of spongin fibers and/or siliceous spicules• Siliceous spicules with one to four rays not at right angles, All members express the leuconoid body form

Yellow sponge growing on a wall on a Caribbean reef.

Fosszilis szivacsok - írókréta

Devon, perm, triász, jura

Archaeocyatha

Korallok

What is a coral?

-A “coral” is actually a “coral colony”

-Rocky limestone base

-Surface is covered by thousands of tiny coral animals, called “polyps”

-Polyps are filled with microscopic algae

Anatomy of a coral polyp

-Each polyp looks like a tiny sea anemone

-Ring of stinging tentacles around a central mouth

-Rests in a “cup” on the surface of the colony

Cnidarian Body Plans

Polyp form• Tubular body, with the mouth directed upward.• Around the mouth are a whorl of feeding tentacles.• Only have a small amount of mesoglea• Sessile Medusa form• Bell-shaped or umbrella shaped body, with the mouth is directed downward.

• Small tentacles, directed downward.• Possess a large amount of mesoglea

• Motile, move by weak contractions of body

Class Anthozoa• Exclusively marine; there is no medusa stage• At one or both ends of the mouth is a ciliated groove called the siphonoglyph; generates a water current and brings food to the gastrovascular cavity• Possess a well developed pharynx • The gastrovascular cavity is large and petitioned by septa or mesenteries; increase surface area for digestion or support• Edges of the septa usually have threadlike acontia threads, equipped with nematocysts and gland cells

Class Anthozoa cont.

• Solitary anthozoans include sea anemones• Most anthozoans are colonial (e.g. corals) and secrete external skeletons composed of calcium carbonate.• Corals obtain much of their energy from microscopic photosynthetic green algae (zooxanthellae) or dinoflagellates that live symbiotically inside the cells of the coral

What do corals eat?

-Like a sea anemone, the polyp can capture small prey (mostly zooplankton) with its tentacles

-Also get nutrition from a symbiotic relationship with zooxanthellae….

What do corals eat?

Algae Fish Shrimp

What are zooxanthellae?

-Algae that live in the coral polyp’s surface layer

-Algae get nutrients and a safe place to grow

-Corals get oxygen and help with waste removal

-Corals also get most of their food from the algae

Photo: Michael ten Lohuis

What is coral bleaching?

Coral bleaching is caused by stressPoll question: what might be stressful for a coral? We’ll get back to the answer later….

Healthycoral

Bleached coral

What turns the coral white?

- As a stress response, corals expel the symbiotic zooxanthellae from their tissues- The coral tissue is clear, so you see the white limestone skeleton underneath

Healthy coral with algae

Bleached coral with no algae

What can stress a coral?

-High light or UV levels-Cold temperatures-Low salinity and high turbidity from coastal runoff events or heavy rain-Exposure to air during very low tides-Major: high water temperatures

Photos: AIMS and GBRMPA

Coral reef distribution andthermal stress

-Corals live close to their thermal maximum limit

-If water gets 1 or 2°C higher than the summer average, corals get stressed and bleach

-NOAA satellites measure global ocean temperature and thermal stress

Can corals recover?

-Yes, if the stress doesn’t last too long

-Some corals can eat more zooplankton to help survive the lack of zooxanthellae

-Some species are more resistant to bleaching, and more able to recover

Photos: AIMS and GBRMPA

The fore reef consists of coarse, angular fragments of reef. Coralline algae are the major contributors of carbonate sand and mudin the back-reef environment. Beaches and dunes = bioclastic sand.The sediments in each area can lithify to form highly varied limestones.

A living coral-algal reef sheds bioclastic sedimentinto the fore-reef and back-reef environments.

Tengerhőmérséklet és korallzátonyok

Rugosa

Calceola

Scleractinia - magános korallok

Cyclolites

Scleractinia – telepes korallok

Időbeosztás 2

• IX. 15. bevezetés, tafonómia, algák• IX. 22. magasabbrendű növények• IX. 29. egysejtűek• X. 6. szivacsok, korallok• X. 13. puhatestűek 1 + 1. zh• X. 20. puhatestűek 2• X. 27.puhatestűek 3• XI. 3. őszi szünet

Időbeosztás 3

• XI. 10. ízeltlábúak

• XI. 17. mohaállatok, pörgekarúak + 2. zh

• XI. 24. tüskésbőrűek

• XII. 1. gerincesek 1

• XII. 8. gerincesek 2

• XII. 15. 3. zh.