Calcarea

Diversity

There are about 400 described species of sponges in the Calcarea group.

Geographic Range

Calcarea sponges are found throughout the oceans, but are mainly in temperate areas.

• Biogeographic Regions
• arctic ocean arctic ocean
• indian ocean
• atlantic ocean atlantic ocean
• pacific ocean pacific ocean
• mediterranean sea

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.

• Habitat Regions
• temperate temperate
• tropical tropical
• saltwater or marine saltwater or marine

• Aquatic Biomes
• benthic benthic
• reef reef
• coastal coastal

• Other Habitat Features
• intertidal or littoral intertidal or littoral

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.

• Other Physical Features
• ectothermic ectothermic
• heterothermic heterothermic

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.

• Development - Life Cycle
• indeterminate growth indeterminate growth

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.

• Key Reproductive Features
• simultaneous hermaphrodite
• sequential hermaphrodite
• sexual sexual
• asexual asexual
• fertilization fertilization
  • external external
• viviparous viviparous

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.

• Key Behaviors
• sessile sessile

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.

• Perception Channels
• chemical chemical
• electric electric

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.

• Primary Diet
• planktivore planktivore
• detritivore detritivore

• Foraging Behavior
• filter-feeding filter-feeding

Predation

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

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.

• 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.

• 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.

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.

Additional Links

Encyclopedia of Life

Contributors

Renee Sherman Mulcrone (author).

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 .