'' since August 2007 }}
For the porous cleaning tool, see Sponge (tool). Sponge (disambiguation)
Sponge}} Fossil range: Ediacaran - Recent
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Scientific classification
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Domain:
| Eukaryota
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Kingdom:
| Animalia
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Phylum:
| "Porifera
" (Paraphyletic) Grant in Todd, 1836
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The sponges
or poriferans
(from Latin porus
"pore" and ferre
"to bear") are animals of the phylum Porifera
(). Porifera
translates to "Pore-bearer". They are primitive, sessile, mostly marine, water dwelling filter feeders that pump water through their bodies to filter out particles of food matter. Sponges represent the simplest of animals. With no true tissues (parazoa), they lack muscles, nerves, and internal organs. Their similarity to colonial choanoflagellates shows the probable evolutionary jump from unicellular to multicellular organisms. However, recent genomic studies suggest they are not the most ancient lineage of animals, but may instead be secondarily simplified. [1]
There are over 5,000 modern species of sponges known, and they can be found attached to surfaces anywhere from the intertidal zone to as deep as 8,500 m (29,000 feet) or further. Though the fossil record of sponges dates back to the Neoproterozoic Era, new species are still commonly discovered.
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SPONGE TICKETS
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Anatomy and morphology
Sponge in Tide pool
Aphrocallistes vastus
(Cloud sponge) is a type of glass sponge. They are very fragile, as they are made out of tiny glass crystals (hydrated silica dioxide). [2]
Sponges have several cell types:
- Archaeocytes (or amoebocytes) have many functions; they are totipotent cells which can transform into sclerocytes, spongocytes, or collencytes. They also have a role in nutrient transport and sexual reproduction.
- Cells are arranged in a gelatinous non-cellular matrix called mesophyll
Sponges have three body types:
asconoid,
syconoid, and
leuconoid.
- Choanocytes (also known as "collar cells") function as the sponge's digestive system, and are remarkably similar to the protistan choanoflagellates. The collars are composed of many microvilli and are used to filter particles out of the water. The beating of the choanocytes’ flagella creates the sponge’s water current.
- Collencytes secrete collagen.
- Myocytes are modified pinacocytes which control the size of the osculum and pore openings and thus the water flow.
- Pinacocytes which form the pinacoderm, the outer epidermal layer of cells. This is the closest approach to true tissue in sponges
- Porocytes are tubular cells that make up the pores into the sponge body through the mesohyl.
- Sclerocytes secrete calcareous siliceous spicules which reside in the mesohyl.
- Spongocytes secrete spongin, collagen-like fibers which make up the mesohyl.
- Spicules are stiffened rods or spikes made of calcium carbonate or silica which are used for structure and defense.
Asconoid
sponges are tubular with a central shaft called the
spongocoel. The beating of flagella forces water into the spongocoel through pores in the body wall. Choanocytes line the spongocoel and filter nutrients out of the water.
Leuconoid
sponges lack a sperm and instead have flagellated chambers, containing choanocytes, which are led to and out of via canals.
Syconoid
sponges are similar to asconoids. They have a tubular body with a single osculum, but the body wall is thicker and more complex than that of asconoids and contains choanocyte-lined radial canals that empty into the spongocoel. Water enters through a large number of dermal ostia into incurrent canals and then filters through tiny openings called
prosopyles into the radial canals. Their food is ingested by the choanocytes. Syconoids do not usually form highly branched colonies as asconoids do. During their development, syconoid sponges pass through an asconoid stage.
It should be noted that these 3 body grades are useful only in describing
morphology, and not in classifying sponge species, althought the asconoid and syconoid construction is present in Calcarea only
[3].
Physiology
Sponges have no true
circulatory system; instead, they create a water current which is used for circulation. Dissolved gases are brought to cells and enter the cells via simple
diffusion.
Metabolic wastes are also transferred to the water through diffusion. Sponges pump remarkable amounts of water.
Leuconia
, for example, is a small leuconoid sponge about 10 cm tall and 1 cm in diameter. It is estimated that water enters through more than 80,000 incurrent canals at a speed of 6cm per minute. However, because
Leuconia
has more than 2 million flagellated chambers whose combined diameter is much greater than that of the canals, water flow through chambers slows to 3.6cm per hour.
[4] Such a flow rate allows easy food capture by the collar cells. All water is expelled through a single
osculum at a velocity of about 8.5 cm/second: a jet force capable of carrying waste products some distance away from the sponge.
Sponges of the family Cladorhizidae (order Poecilosclerida, class Demospongiae) are species usually found in deep water, but also in
littoral caves in the
Mediterranean (Asbestopluma hypogea), that have become
carnivorous, using a strategy that has much in common with what is found in carnivorous plants such as
sundew. When small crustaceans comes in contact with their surface, they get captured by a sticky substance, or in the case of the Mediterranean species by spicules modified into raised hook-shaped spines, and then digested by migrating cells which soon covers the prey
[5]. This lifestyle has caused the loss of their aquiferous system and the choanocytes, resulting in forms like the ping-pong tree sponge (Chondrocladia lampadiglobus), which don't look like typical sponges
[6].
Taxonomy
thumb
Sponges are traditionally divided into classes based on the type of
spicules in their skeleton. The three classes of sponges are bony (
Calcarea), glass (
Hexactenellida), and spongin (
Demospongiae). Some taxonomists have suggested a fourth class,
Sclerospongiae, of coralline sponges, but the modern consensus is that coralline sponges have arisen several times and are not closely related.
[7] In addition to these four, a fifth, extinct class has been proposed:
Archaeocyatha. While these ancient animals have been phylogenetically vague for years, the current general consensus is that they were a type of sponge. Although 90% of modern sponges are
demosponges, fossilized remains of this type are less common than those of other types because their skeletons are composed of relatively soft spongin that does not fossilize well.
Sponge taxonomy is an area of active research, with molecular studies improving our understanding of their relationship with other animals.
Basal lineage?
Sponges are among the simplest
animals. They lack
gastrulated embryos,
extracellular digestive cavities,
nerves,
muscles,
tissues, and obvious sensory structures, features possessed by all other animals. In addition, sponge
choanocytes (feeding cells) appear to be a homologous to
choanoflagellates, a group of unicellular and colonial protists that are believed to be the immediate precursors of animals. The traditional conclusion is that sponges are the basal lineage of the animals, and that features such as tissues developed after sponges and other animals diverged. Sponges were first assigned their own subkingdom, the
Parazoa, but more recent molecular studies suggested that the sponges were
paraphyletic to other animals, with the eumetazoa as a sister group to the most derived:
[8]
{{clade
Either way, sponges have long been considered useful models of the earliest multicellular ancestors of animals.
...or secondarily simplified?
However, a phylogenomic study in 2008 of 150 genes in 21 genera
[1] suggests that the
ctenophora are the most basal lineage of the 21 taxa sampled, and that sponges—or at least those lines of sponges investigated so far—are not primitive, but secondarily simplified, having lost tissues and other eumetazoan characteristics from their common ancestor.
Geological history
Fossil sponge Raphidonema faringdonense
from the Cretaceous of England
Sponge borings and encrusters on a modern bivalve shell, North Carolina.
The
fossil record of sponges is not abundant. Some fossil sponges have worldwide distribution, while others are restricted to certain areas. Sponge fossils such as
Hydnoceras
and
Prismodictya
are found in the
Devonian rocks of
New York state. In
Europe the
Jurassic limestone of the
Swabian Alb are composed largely of sponge remains, some of which are well preserved. Many sponges are found in the
Cretaceous Lower Greensand and
Chalk Formations of
England, and in rocks from the upper part of the Cretaceous period in
France. A famous locality for fossil sponges is the Cretaceous Faringdon Sponge Gravels in
Faringdon,
Oxfordshire in
England. An older sponge is the
Cambrian Vauxia
. Sponges have long been important agents of
bioerosion in shells and carbonate rocks. Their borings extend back to the
Ordovician in the fossil record.
Fossil sponges differ in size from 1 cm (0.4 inches) to more than 1 meter (3.3 feet). They vary greatly in shape, being commonly vase-shapes (such as
Ventriculites
), spherical (such as
Porosphaera
), saucer-shaped (such as
Astraeospongia
), pear-shaped (such as
Siphonia
), leaf-shaped (such as
Elasmostoma
), branching (such as
Doryderma
), irregular or encrusting.
Detailed identification of many fossil sponges relies on the study of thin sections.
Ecology
Modern sponges are predominantly marine, with some 150 species adapted to freshwater environments. Their habitats range from the inter-tidal zone to depths of 6,000 metres (19,680 feet). Certain types of sponges are limited in the range of depths at which they are found. Sponges are worldwide in their distribution, and range from waters of the polar regions to the tropical regions. Sponges are most abundant in both numbers of individuals and species in warmer waters.
Adult sponges are largely sessile, and live in an attached position. However, it has been noted that certain sponges can move slowly by directing their water current in a certain direction with myocytes. The greatest numbers of sponges are usually to be found where a firm means of fastening is provided, such as on a rocky ocean bottom. Some kinds of sponges are able to attach themselves to soft sediment by means of a root-like base. Sponges also live in quiet clear waters, because if the sediment is agitated by wave action or by currents, it tends to block the pores of the animal, lessening its ability to feed and survive.
Recent evidence suggests that a new disease called
Aplysina red band syndrome (ARBS) is threatening sponges in the Caribbean. Aplysina red band syndrome causes Aplysina to develop one or more rust-coloured leading edges to their structure, sometimes with a surrounding area of necrotic tissue so that the lesion causes a contiguous band around some or all of the sponge's branch.
Reproduction
Sponges can reproduce
sexually or
asexually.
Asexual reproduction is through internal and external
budding. External budding occurs when the parent sponge grows a bud on the outside of its body. This will either break away or stay connected. Internal budding occurs when archaeocytes collect in the mesohyl and become surrounded by
spongin. The internal bud is called a
gemmule, and this is seen only in the freshwater sponge family, the Spongillidae. An asexually reproduced sponge has exactly the same genetic material as the parent.
In sexual reproduction,
sperm are dispersed by water currents and enter neighboring sponges. All sponges of a particular species release their sperm at approximately the same time. Fertilization occurs internally, in the mesohyl. Fertilized oocytes develop within the mesohyl. Cleavage stages are highly varied within and between groups, sometimes even within a single species. Larval development usually involves an odd type of morphogenetic movement termed an inversion of layers. When this occurs in some species (for example, in
Sycon coactum
), the larva flips into the choanocyte chamber, and then can emerge via the water canal system and out through the osculum.
Although sponges are
hermaphroditic (both male and female), they are not self-fertile. Most sponges are sequential hermaphrodites, capable of producing eggs or sperm, but not both at the same time.
Use
By dolphins
In 1997, use of sponges as a
tool was described in
Bottlenose Dolphins in
Shark Bay. A dolphin will attach a marine sponge to its
rostrum, which is presumably then used to protect it when searching for food in the sandy
sea bottom.
[10] The behaviour, known as
sponging
, has only been observed in this bay, and is almost exclusively shown by females. This is the only known case of tool use in
marine mammals outside of
Sea Otters. An elaborate study in 2005 showed that mothers most likely teach the behaviour to their daughters.
[11]
By humans
Natural Sponges in Tarpon Springs, Florida
Skeleton as absorbent
In common usage, the term
sponge
is applied to the skeleton of the animal, from which the tissue has been removed by
maceration and washing, leaving just the
spongin scaffolding.
Calcareous and
siliceous sponges are too harsh for similar use. Commercial sponges are derived from various species and come in many grades, from fine soft "lamb's wool" sponges to the coarse grades used for washing cars.
The manufacture of
rubber-,
plastic- and
cellulose-based synthetic sponges has significantly reduced the commercial sponge
fishing industry in recent years.
The
luffa "sponge", also spelled
loofah
, commonly sold for use in the kitchen or the shower, is not derived from an animal sponge, but from the
locules of a gourd (
Cucurbitaceae).
Antibiotic compounds
Sponges have
medicinal potential due to the presence of
antimicrobial compounds in either the sponge itself or their microbial
symbionts.
[12]
Bibliography
References
- Broad phylogenomic sampling improves resolution of the animal tree of life
- Department of Biological Sciences - Studies in Life Sciences, University of Alberta: Glass Sponge Ecology, accessed March 16, 2008
- Animal Diversity Web - Class Calcarea
- See Hickman and Roberts (2001) Integrated principles of zoology — 11th ed., p.247
- Predation on copepods by an Alaskan cladorhizid sponge
- Carnivorous sponges
- Invertebrates. Second Edition
- Poriferan paraphyly and its implications for Precambrian paleobiology
- Broad phylogenomic sampling improves resolution of the animal tree of life
- Sponge-carrying by Indian Ocean bottlenose dolphins: Possible tool-use by a delphinid }
- Cultural transmission of tool use in bottlenose dolphins
- See e.g. Teeyapant R, Woerdenbag HJ, Kreis P, Hacker J, Wray V, Witte L, Proksch P. (1993) Antibiotic and cytotoxic activity of brominated compounds from the marine sponge Verongia aerophoba. ''Zeitschrift für Naturforschung. C, Journal of biosciences'' '''48''':939–45.