Calcarea

Diversity

There are about 400 described species of sponges in the Calcarea group. (Wörheide, 2002)

Geographic Range

Calcarea sponges are found throughout the oceans, but are mainly in temperate areas. (Wörheide, 2002)

Habitat

Exclusively marine and mainly in temperate regions, Calcarea sponges are usually found in shallower, sheltered waters less than 1000 m. In tropical regions they are associated with coral reefs. (Wörheide, 2002)

Physical Description

Calcarea is the only class with asconoid and syconoid construction. All others have leuconoid construction. The calcium carbonate spicules are only megascleres, or large structural spicules. Other groups of sponges have microscleres, which are smaller reinforcing spicules. Most Calcarea are 10 cm less in height, and are dull in color, although some colorful species are known. (Barnes, 1987; Brusca and Brusca, 2003; Wörheide, 2002)

Development

Reproduction occurs asexually by budding and sexually. Development of fertilized eggs takes place within the sponge. The larval stage has outer flagellated cells, often with spicules. The young break out of the parent's mesohyl, and become free swimming larvae, but not for more than two days.

Sponges have different amoeboid cells in the mesohyl. Acheocytes are large cells with large nuclei. These cells are totipotent, meaning they can develop into any cell type. Sclerocytes, also in the mesohyl, accumulate calcium to produce spicules. Three sclerocytes will fuse to form spicules in intercellular spaces. (Barnes, 1987; Brusca and Brusca, 2003)

Reproduction

Most all sponges can reproduce asexually, by regenerating tissues. Sponges also reproduce sexually. Being hermaphroditic, sperm and eggs can be reproduced, sequentially or at the same time. Choanocytes give rise to egg and sperm cells, and archaeocyte cells also give rise to egg cells. Sperm and eggs are released in the water, and most species cross fertilize. Fertilized eggs will develop into free-swimming larvae. (Brusca and Brusca, 2003; Wörheide, 2002)

There is no parental investment beyond release of gametes.

Behavior

Members of Porifera are sessile since they are attached to the substrate. However, some sponges may move as amoeboid cells at the base move. (Brusca and Brusca, 2003)

Communication and Perception

Sponges will react by closing ostia or oscula, either because of direct physical stimulation or when suspended particles within the sponge are too large or highly concentrated. However, there are no known nerve structures. However, some sponges may respond to electrical impulses. (Bamfield Marine Sciences Centre, 2004)

Food Habits

Because of the simple cells that make up sponges, cell types and water currents used by the sponges to obtain food have been extensively studied. Sponges in general use flagellated cells called choanocyte cells to create a current. Choanocytes are located in the interior part of the sponge. In the asconoid structure, the water is drawn in through the ostium (outer pores), goes through the spongocoel or atrium, and out the osculum (the opening in the top of the sponge). Outer pores are 50 micrometers or less, so larger particles and animals are not ingested.

As food or particles are moved through the sponges, amoemoid cells surround and engulf it (pinocytosis and phagocytosis). Particles are caught in the collar part of the choanocyte cells. (Brusca and Brusca, 2003)

Predation

Sponges are preyed on by many animals. Spicules, and other compounds, including potential biotoxins, probably discourage most predators. (Brusca and Brusca, 2003)

Ecosystem Roles

Sponges in general may make up a significant portion of the benthic biomass. For example, in Antarctica, at depths of 100-200 m, 75 per cent of the benthic biomass are sponges. (Brusca and Brusca, 2003)

  • Ecosystem Impact
  • creates habitat

Economic Importance for Humans: Positive

Sponges have been harvested for centuries by many civilizations. Compounds produced by sponges are being explored for pharmaceuticals. (Brusca and Brusca, 2003)

  • Positive Impacts
  • body parts are source of valuable material

Conservation Status

Sediments effect sponges although they are resistant to hydrocarbons (including detergents) and heavy metals. Particular species have been overharvested. (Brusca and Brusca, 2003)

  • IUCN Red List [Link]
    Not Evaluated

Other Comments

Although Calcarea is considered the primitive group, and are the only sponges with asconoid and synconoid construction, the asconoid and synconoid forms are not necessarily considered primitive conditions. (Brusca and Brusca, 2003; Wörheide, 2002)

Contributors

Renee Sherman Mulcrone (author).

Glossary

Arctic Ocean

the body of water between Europe, Asia, and North America which occurs mostly north of the Arctic circle.

Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

asexual

reproduction that is not sexual; that is, reproduction that does not include recombining the genotypes of two parents

benthic

Referring to an animal that lives on or near the bottom of a body of water. Also an aquatic biome consisting of the ocean bottom below the pelagic and coastal zones. Bottom habitats in the very deepest oceans (below 9000 m) are sometimes referred to as the abyssal zone. see also oceanic vent.

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

detritivore

an animal that mainly eats decomposed plants and/or animals

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

electric

uses electric signals to communicate

external fertilization

fertilization takes place outside the female's body

fertilization

union of egg and spermatozoan

filter-feeding

a method of feeding where small food particles are filtered from the surrounding water by various mechanisms. Used mainly by aquatic invertebrates, especially plankton, but also by baleen whales.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

indeterminate growth

Animals with indeterminate growth continue to grow throughout their lives.

intertidal or littoral

the area of shoreline influenced mainly by the tides, between the highest and lowest reaches of the tide. An aquatic habitat.

planktivore

an animal that mainly eats plankton

reef

structure produced by the calcium carbonate skeletons of coral polyps (Class Anthozoa). Coral reefs are found in warm, shallow oceans with low nutrient availability. They form the basis for rich communities of other invertebrates, plants, fish, and protists. The polyps live only on the reef surface. Because they depend on symbiotic photosynthetic algae, zooxanthellae, they cannot live where light does not penetrate.

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

sessile

non-motile; permanently attached at the base.

Attached to substratum and moving little or not at all. Synapomorphy of the Anthozoa

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

Bamfield Marine Sciences Centre, 2004. "Porifera" (On-line). Ocean Link. Accessed January 13, 2005 at http://oceanlink.island.net/ask/porifera.html#anchor22429.

Barnes, R. 1987. Invertebrate Zoology. Orlando, Florida: Dryden Press.

Brusca, R., G. Brusca. 2003. Invertebrates. Sunderland, Massachusetts: Sinauer Associates, Inc..

Wörheide, G. 2002. "Calcarea Introduction" (On-line). Gert Wörheide's homepage about geobiology. Accessed January 13, 2005 at http://wwwuser.gwdg.de/~gwoerhe/calcarea_introduction.html.