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There are a lot of selections in photos, but you can take a bit as stated by your temper and seducion.
The asconoid sponge body consists of two layers of cells with a layer of gelatinous material (called mesogloea) sandwiched in-between. Individuality in spongesMany sponges are colonial - many tubes, each bearing an osculum vent may be fused together at their bases to form a single mass. Above: three tubular demosponges, one of which is ejecting sperm in the excurrent jetting from its osculum (a 'smoking sponge'). The shapes of spongesSponges appear in a huge variety of forms: spherical, conical, club-shaped, vase-like, tubular, goblet or cup-like, encrusting sheets, upright sheets, plate-like, fans and treelike forms, etc. Left: a model of a goblet sponge - several species adopt a cup-like form, complete with stalk and attachment disc. The sponge spicule skeleton is a truly remarkable structure that ought to be the envy of engineers.
Here are some interim picture updates just to show you the progress but I’ve still got a couple of days left. You could incorporate some storm-water culverts (for increased details) and show 2 or 3 dry runoff contours. I was trying to workout if Barries Figure 8 layout is for 2 trains going in opposite directions, or for just 1 train that has the old 3 rail configuration.
Barry, you’re not just a nice guy, an engineer, a good friend, wonderful husband and father, but also a creative genius! Third rail is nice, insulate one outside rail and every wheelset closes the circuit – a switch, to operate signals, crossing gates, etc.
For all my two rail fans, how do you make a reverse loop without using several DPST switches to manipulate the polarity of the tracks? Barry, I really like the layout you decided to go for, excpesially since you will be selling on E Bay. Sponges belong to the phylum Porifera, which literally many 'many pores' since the surface of a sponge is covered in minute pores that suck in water and nutrients, which the sponge filters before expelling the water from a large opening or osculum. This sponge has many minute pores opening directly into a single central cavity, or atrium (spongocoel), and one or more large oscula (singular: osculum).
These microscopic creatures beat their flagellum, driving a current of water away from them and sucking in water from behind which passes between the collar of microvilli to fill the void left by the water pumped away. These sponges vary considerably in form between species and many undoubtedly remain unknown to science. It may be that each unit, comprising a single osculum and surrounding tissue is one individual and that one sponge produced new individuals that failed to separate completely. Any piece can regenerate into a whole sponge, but the process is slow, requiring months or years for the new sponge to reach full size.
Sometimes individuals of the same species, but growing in different locations, may show very different shapes, although each species tends to adopt a particular range of shapes. This is one example of an open sponge architecture, in which the outflowing water enters a common spongocoel chamber before being expelled through the osculum. It is interesting to look at sections of sponges and see how the various spicules fit together like mechano into diverse large-scale meshworks designed to take the weight of the animal, give its tissues hardness and protect it against predators, and all with minimum material costs and light-weight construction. Items ace XX of 103 Ideal for train layouts battle mats architectural models school day projects arts and. ModelTrainStuff posture Trains and Model Train Acessories Noch 00260 Grass matt Spring Noch 00270 pot Mat Flowered pasturage Noch 00280 stag 100x50cm model train grass mat Green Nylon Artificial expose Model Layout model train grass mat. Put signals at the rail crossings, then a simple circuit relay to control the signal lights. So I’m asking for your asistence and advice in advissing me as to whitch of my understandings is infact right or are they both wrong, so would you tell me what Barry uses his figure 8 layout for please! The Lionel operators dont have that problem because the center rail is always the power rail.
You just need to feed power from the transformer to one outer rail and the other wire goes to the center rail. Sponges are usually brightly coloured - red, orange, purple, green and yellow are common sponge colours, though deep sea forms are often dark brown and drab or glassy.
The sponge sucks water into the atrium through the many tiny incurrent or inhalent pores and pumps it out through the excurrent or exhalent osculum as a forceful jet of water that may travel 10 feet or more from a large sponge. These cells fit together tightly to form the outer surface or pinacoderm (a type of covering tissue or epidermis).
Siphons emerge above the sediment which buries the bulb-like body and root-like appendages extend into the substrate. On the other hand, it is known that some sponges if placed next to one another will fuse together to form a single individual, whilst others may fuse temporarily before rejecting one another, in which case a space (zone of non-coalescence) appears between them. If a sponge is broken into cells and cell-clumps, then the amoebocytes aggregate to form a reunition mass. Sponges that live rooted in soft sediment benefit from being tall as this prevents them being easily buried by shifting sediments. Other sponges have a solid architecture, in which canals permeate the whole body and coalesce to open directly into one or more oscula. The whole inner surface of the asconoid is lined by choanocytes (the choanoderm) as indicated in red. Has anyone ever used WS vinyl grass mat for their layout before advantages or disadvantages I’m going to add ground foam in certain areas.
For these couplers to work well, they need to be mounted to the car body and NOT the truck (wheel set).
I have done a few layouts myself, and just wanted to say even when it looks so basic and small, they can still be a pain in the bottom. The sponge above is definitely an individual - it has a single large opening, or osculum, which carries a jet of water out of the sponge's body, but many sponges form colonies of many individuals fused together with many oscula, in which case it is not very sensible to talk about an individual sponge (although the tissue surrounding each osculum may define an individual). They typically have wavy contours to strengthen the connections between them (by increasing the surface area along which the cells can be fastened together). The flagellum has wings or flanges which help it push against the water more effectively (it must be remembered that on this microscopic scale water behaves as quite a thick sticky liquid).
Right: the sponge as seen in its natural habitat - with only the porous tips of the siphons visible above the sediment.
The spicules may be principally calcium carbonate in calcareous sponges and are made of silica in siliceous sponges; spongin is a protein. It turns out that usually only sponges of the same species and the same strain will fuse together.
Some reunition masses contain collar cells without collars and various types of amoebocyte.
The syconoid type represents an array of asconoid types arranged around the cylinder of the sponge (the incurrent pores are not shown, but the red layer is porous in all these sponge types). Lionel train run on alternating current and reversing the trains is accomplished by a relay type switch mounted on each engine.
The track with all the ties rather than Lionel sparse looking ties with only three ties in almost every ten inches is made by Cargraves company. So far I Love It, But I Would Love Some Ideas On Any Layout Designs You Might Have For Me, As I Just Moved, & Am Starting A New, N Scale Layout.
Sponge bodies may be ball, vase, basket, cup or club-shaped like the one above, or they may be flat and encrusting or branching and tree-like. These particles include mostly bacteria and other microscopic organisms and organic debris. Inside is a layer of so-called collar cells or choanocytes, each with one flagellum pointing toward the atrial cavity and surrounded by a ring of short appendages called cilia.
As water passes between the collar, potential food items, like bacteria, are sieved out and ingested by the cell. The spicules (sclerites) are tiny (mostly microscopic) crystalline bodies and each is a spine or a number of spines radiating from a point. A sponge will fuse with pieces of itself - if a piece of tissue is removed and then placed near to the source sponge, or inside a hole cut into the sponge (an autograft), then the fragment will fuse with its parent body.
Just as an oak tree has to maximise the light it intercepts and the carbon dioxide it removes from the atmosphere, so a sponge has to maximise the efficiency with it extracts food from water by filtration. In type 2 syconoid sponges an additional layer of dermal tissue, perforated by large pores, covers the structure. Triaenes are tetraxons with one long ray, called a rhsbdome and 3 smaller clads that form the cap-like cladome. Are your little ones natural state about Are you looking at for axerophthol cool dally endue operating theater planning on decking out their room indium high style with a few Thomas accessories or train. This eatage mat railway mold school layout manakin is highly Nylon material grass with kraft newspaper backing this grass mat is self-colored and arse be used BizRate Customer Certified Au internet. This occurs mostly when pulling longer trains or trying to back up a train through a turnout (switch) or on a curve. Indeed, the shape of a sponge is an adaptation to its environment - in rough waters, such as along a rocky coastline, sponges will be flat and encrusting, clinging tightly to any nook and cranny they can find in the rock surface, whilst in calm waters they tend to be more upright and present a larger surface to the water to enhance the rate at which they can sieve food from the water. The flagellum undulates or beats, expelling water out into the atrium and sucking it in through the pores that penetrate both cell layers.
This is essentially similar to how a choanocyte in a sponge works (except that choanocytes lack the flanges on their flagella). Each spicule consists of an organic axis surrounded by calcium carbonate or hydrated silica. If a graft (say a cube of tissue) from another sponge is placed inside a hole cut into the recipient sponge, then only if the graft was from another sponge of the same strain will it fuse with the recipient.
If two branches of an oak tree are too close together, then their leaves may overlap and the shaded leaves may receive insufficient light for photosynthesis and they are a waste to the plant. The leuconoid type is the most advanced and consists of an array of syconoid units arranged around a cylinder.
Sponges may be tiny forms, which are easily overlooked, or they may be large enough for a man to stand inside! Each of these incurrent pores is a channel travelling through a cylindrical cell called a porocyte. Thus, a sponge's body contains thousands of microscopic pumps that also filter food from the water.
If the graft is from a different strain, even one of the same species, then rejection will occur - the graft will not fuse and may become black and necrotic and shrink away as tissue from the recipient grows into the wound to replace the rejected graft.


Additionally, the leaves of one branch absorb carbon dioxide from the atmosphere and create a zone of air around the branch depleted in carbon dioxide which is only slowly replaced by diffusion in slow air, but is replaced more quickly in windy conditions. Only the layers shown in red, the choanocyte chambers, bear choanocytes, which line the inside only of each chamber. Sponges are very unusual animals, representing an off-shoot of the animal kingdom that evolved along its own lines, separate from the vast majority of animal types. Collectively, many thousands or millions of choanocytes can produce a powerful jet of water that leaves the atrium from the large excurrent osculum (or oscula if more than one is present). It is thought that choanoflagellates are related to sponges, and that perhaps sponges evolved from colonies of these cells.Another general cell type is typical of sponges - the amoebocyte. This will grow into a sponge when and if favourable conditions return.Infaunal SpongesA peculiar type of sponge that is little known and little studies is the infaunal sponge that lives mostly buried in soft sediment at the bottom of the sea or below reef slopes on the continental margin. With two branches too close together the branches will compete for carbon dioxide and most likely there will not be enough to go around. Syconoid and leuconoid sponges necessarily have a more complex system of pores and channels to convey water through the sponge. Amoebocytes are amoeboid cells that are free to crawl around (in and on) the body of the sponge in much the same way as do amoebae. Biochemicals, called sponge factors, are known to be secreted by sponge tissues when a graft is introduced, if the strains are incompatible, then these factors will reduce the adhesiveness of the cells to one another and the graft will be unable to stick and fuse to the recipient. For example, the model sponge shown below (click thumbnails to enlarge) is similar to species of Oceanapia consists of a dark brown spheroidal central bulb, some 6 cm by 4 cm, buried beneath 5-10 cm of sediment.
This would be the case if the crown was a solid ball with no branches - all parts of the crown would be competing for insufficient resources and this would be wasteful. The arrangement is such that water only flows through one choanocyte chamber on its passage through the sponge, otherwise energy would be wasted in filtering water that has already been filtered.
Choanoflagellates may live as single cells or in multicellular colonies and are rather like protosponges - sponges lacking the pinacocytes and mesogloea and other packaging cells that make up the sponge body. Whether we define an individual sponge as a physically separate sponge (even if one grew from a fragment of the other) or whether we define the compatible strain as the individual is a matter of opinion. From this bulb extend 4-9 tubes or siphons, 6-28 cm in length and about 1 cm in diameter and whose white tips extend 3-8 cm above the sediment surface. To overcome this problem, tress branch according to one of several optimum branching patterns (the exact solution used depends upon species, which is one reason why different species have different branching patterns) which spreads the branches apart so that they do not compete too much with one another and the tree can maximise its exploitation of light and carbon dioxide without wasting resources (like wood).It is possible to use a computer to solve the mathematical problem of supply and predict the optimum branching patterns.
The more complex syconoid and leuconoid architectures are more efficient and so are able to achieve greater size - an asconoid becomes increasingly less efficient at larger size. Amoebocytes have a variety of functions, including maintaining the mesogloea (mesenchyme) and removing foreign organisms and debris from the sponge body. In Oceanapia peltata, found off the Colombian coast, these siphons may bear a number of stacked horizontal discs partially enclosing them (not shown). This has been done for sponges (using the diffusion equation to model the diffusion of food particles into the volume of water around the sponge that the sponge can exploit by sucking this water through its body). Asconoid sponges are small, and rarely exceed 10 cm in height, but the more complex and efficient leuconoid sponges may reach two metres in height.
One of the main functions of the wandering amoebocytes is secretion of the sponge skeleton.The mesenchyme is a transparent gelatinous matrix (mesogloea) containing free amoebocytes.
They may be lance-like, C-shaped, bow-shaped, thorny or knobbly, rod-shaped, twisted spirals or spiny.
Also from the bulb extend a number of tubular 'roots' which penetrate more or less vertically into the sediment to a distance of several cm. The assumption is that sponge tissue will not grow into regions of water where it finds insufficient food (such as too close to other sponge tissue which have already removed the food from the water).
The architectures shown above are all open architectures, in which water exits through a large central spongocoel cavity.
The mesenchyme may be a collenchyma (meaning it has few cells and a lot of material between the cells), or a parenchyma (with a high cell density and little material between the cells as they are tightly packed together). Some have a pointed end projecting to the exterior of the sponge, making its surface rough and spiny, presumably for protection.2.
The description given is intended to assist your imagination, but infaunal sponges come in a diverse variety of shapes and forms.
These models correctly predict many sponge-like shapes, including the branching tree-like forms. Many sponges have solid architectures, in which a series of channels coalesce to expel water through one or more oscula and the large central spongocoel is essentially absent.
The amoebocytes are free to wander about the sponge and fall into two main classes, lobopodous amoebocytes and collencytes. Experiments with Oceanapia have shown that the tips of the siphons are porous and draw water in to a series of channels that permeate the non-porous bulb. One also has to consider whether or not the sponge lives in the open where there are strong currents to bring in fresh food rapidly, or whether it lives in a sheltered region of more stagnant water.Another factor which effects sponge shape is the diameter of supply. Leuconoid sponges are the most common and their architecture may be complicated, such that the sponge's tissue becomes permeated by a complex maze of water channels. Lobopodous amoebocytes include pigmented chromocytes, thesocytes that store food reserves and scleroblasts that secrete the skeleton. These rays are not in the same planes and may resemble jacks, though some of the rays may be reduced, absent or modified into discs.3. Food particles are filtered from the water and then the water is expelled into the sediment by the root-like excurrent tubes (which bear pores of an uncertain nature as it is hard to collect the specimens without damaging the roots). This diameter is the furthest that a sponge can eject water from itself before some of that water recirculates and gets taken up again by the sponge, assuming stagnant conditions. Scleroblasts are further divided into calcoblasts, silicoblasts and spongioblasts, depending on the nature of the skeletal material secreted (calcium carbonate, silicon or spongin protein).
Triaxons (hexactinal spicules) have three axes crossing at right-angles to give six rays, some of which may be lost or reduced or branched or curved and may have spines or knobs, etc. Ideally, the sponge would take up fresh water without mixing in any of the water it has already filtered - filtered water has had the food and much of the oxygen removed from it by the sponge and is now of little use and hence the further the sponge can eject it, the better, as then it is less likely to return or is thoroughly mixed and diluted with fresh water.
Lobopodous amoebocytes have lobopods - locomotory appendages or psedudopods that are blunt, rounded and finger-like - the so-called lobopod type of pseudopod. The secret nature of these sponges and the technical difficulties involved in collecting intact specimens has hampered the study of these sponges. In strong currents, this is not a problem, the currents carry away the waste water and bring in fresh water. Collencytes have slender branching pseudopods (called filopods) and may form a syncytial network (a syncitium is a group of neighbouring cells whose cell membranes are fused together to form a continuous mass of cytoplasm. Polyaxons have several equal rays that radiate from a central point and may be star-shaped or resemble spiny spheres.5. Remember, that despite their appearance, texture and limited movements, sponges are animals! Such a sponge may be an encrusting film that coats the surface of a rock and puts up very short chimneys, each with an osculum on top.
However, distinguishing between a syncitium and a collection of distinctly 'separate' cells with junctions linking them together is not easy!).Archaeocytes are lobopodous amoebocytes.
In more stagnant water, however, the sponge may have taller chimneys through which to eject its waste, which may help the ejected water reach the currents higher above the surface (a boundary layer of stationary or slow-moving fluid always covers the surface of objects, and the depth of this boundary layer increases in more stagnant conditions and reduces in strong currents; above the boundary layer is the turbulent layer where currents mix the water). Archaeocytes are possibly undifferentiated cells and produce the sex cells (as may choanocytes in some sponges?) i.e. The desma is a megasclere formed from a minute monaxon, triradiate or tetraxon spicule, forming a central structure upon which layers of silica are deposited. Factories use the same principle - taller chimneys carry the waste higher into the winds where they carried further away.A third factor determining sponge shape is mechanical.
A tall fan-shaped sponge may be swept away in strong currents, whereas a slender conical sponge or a low-lying encrusting sponge stuck to the rocks over a large surface, are more likely to survive. Indeed, one of the striking characteristics of sponges is their ability to regenerate from a few cells - mince a sponge and each piece can grow back into a new sponge!More complex sponge designsSyconoid sponges have a more complicated body plan than asconoid sponges. Desmas are usually united into a network to form a net-like skeleton (lithistid).Spongin is a protein that forms a branching network. On the other hand, in milder currents, the flat encrusting form may be trapped inside the boundary layer, away from the currents higher up that bring in fresh water, oxygen and food.Different species are best adapted to different conditions, however, the fact that sponges can alter their shape to some degree proves that sponges are sensitive creatures - able to respond to their environment and grow to a shape that best suites the environment.
For example, the sponge Hymeniacidon perleve grows as a thin film that encrusts the surface and puts up a number of very short chimneys, but sometimes it can grow tall chimneys, which may branch or fuse into a single large cluster of chimneys (for greater strength allowing them to grow taller).
They have many finger-like out-pushings which form radial canals continuous with the central atrium (spongocoel).
In the keratosan sponges the skeleton consists entirely of spongin (and embedded foreign particles).Spicules are secreted by scleroblasts, which are a sub-class of amoebocyte. These external projections pack the surface and may be free and surrounded by sea-water or they may be covered by an outer epidermal covering which contains dermal pores, which open into the channels between the projections, called incurrent canals, which pass through pores called prosopyles into the radial canals which are lined by choanocytes. Silicoblasts are a type of scleroblast that secrete siliceous spicules in the siliceous sponges. Other sponges may grow on elongated stalks, enabling them to reach the currents in the turbulent zone and perhaps to avoid sucking up silt from the sediment, which may clog their pores. The radial canals then open into the spongocoel through internal ostia and the water flows through the osculum to the outside.Leuconoid sponges have the most complex structure. There is usually no central spongocoel, instead the sponge cavity is highly branched and divided into clusters of small round or oval chambers lined by choanoflagellates. The various spicule types (of which there are many sub-types I have not mentioned here) have different skeletal roles within the sponge body and the types present also depends upon species. The spicules make the tissue of many sponges very hard, prickly or stony and quite difficult to cut with a knife.
Nevertheless, a given unit of water only flows through one choanocyte chamber as the chambers operate in parallel rather than in series (there is little point trying to filter food from water that has already been filtered!). Traditional bath sponges (not the artificial type!) have spongin skeletons and no mineral spicules, which gives them a springy and spongy texture.Glass Sponges (Hexactinellids)Glass sponges have a skeleton consisting of a lattice of glass-like siliceous fibres.
Most sponges are of the leuconoid type, as this permits the sponge to develop the most efficient water current and to attain a larger size (as it filters food from water more efficiently). They are pale in colour and may have projecting spicules (which may be up to 30 cm long) which may give them a 'glass wool' like covering. Note how the choanocytes are restricted to numerous small chambers formed by the two-fold evagination of the spongocoel.
In at least one form it would appear that the projecting glass fibres (the spicules) act as fibre-optic wires, transmitting light from a bioluminescent crustacean resident that lives inside the spongocoel, which must create a spectacular light display.


It has also been suggested that the glass spicules may be part of a light-sensing system, whether for releasing or receiving light, they are very good at transmitting light.
These mysterious sponges are not very well studies and many glass-sponge wonders surely await discovery. One well known example is the Venus's flower basket - the beautiful glassy skeletons of the sponge Euplectella.The internal structure of glass sponge tissues is very different from that of other sponges. They are covered by a dermal membrane, comprising a syncytium with underlying membrane of spongin (a type of collagen) and have a very open body plan with large open spaces, rather like a honeycomb. The 'archaeocytes' are generally connected to one another by slender cytoplasmic bridges, forming a meshlike or trabecular syncytium that constitutes the bulk of the sponge body.
Each choanoblast gives off one or more stalk-like stolons that connect to collar bearing units, resembling choanocytes but lacking nuclei (there cytoplasm is continuous with that of the choanoblasts). This arrangement is reminiscent of certain colonial choanoflagellates, in which the cells are connected by stalk-like or root-like stolons. The only cells that are routinely seen separated from the syncytium are the scleroblasts, which secrete many of the spicules. All the other cells appear to be connected to one another by cytoplasmic bridges, though they may have rounded bodies, making them resemble distinct cells.
It has been argued that glass sponges are so different to all other sponges that they should be in a separate phylum. However, their strange internal architecture stems from the tendency of their cells not to separate fully at cell division, but to remain in contact with one another by cytoplasmic bridges (which may be occluded by pore plates that allow certain materials to pass from 'cell' to 'cell' directly as the cytoplasm is continuous across the pores) with a single continuous cytoplasmic membrane surrounding the whole structure. Considering that some choanoflagellates are solitary, whilst others form colonies of connected individuals, I don't personally think that this difference is great enough to warrant placing glass sponges in a separate phylum.DemospongesDemosponges either have no spicules at all or they have the siliceous type.
There are at least three types, including the horny sponges (keratosans) which possess spongin skeletons but have no spicules (unless these are made of spongin), though they may incorporate rock grains and other materials into their bodies. The spongin forms a lattice or tree-like branching network throughout the keratosan sponge body.
They live attached to hard materials, glued in place by spongin secretion.Calcareous spongesThese have calcareous spicules and include all the asconoid types, some syconoids and some leuconoids. The calcium carbonate spicules are usually separate but are sometimes fused into a network or are enclosed in calcareous cement. Projecting spicules often give these sponges a bristly texture.Development of tissues in spongesSponges possess tissues (aggregates of cells) but few or no obvious organs. Contractile muscle cells called myocytes, along with the epidermal cells which may be contractile, permit limited movement and muscle cells may form a sphincter around the osculum which may close or open the osculum. In general they are said to be at the tissue-grade level of organisation and lack the complex organ systems that make up most animals.
They do form definite structures, however, for example, long spicules may project to form an oscular fringe surrounding the osculum and a sieve membrane or sieve plate may cover the osculum. The alien-ness of sponges compared to other animals will become clear after studying aspects of their physiology below. Some biologists argue that sponges do not possess tissues and are at the 'cellular stage' of organisation. Though the central mesenchyme contains wandering cells, rather than cell aggregates as such, this is very similar to the connective tissue of vertebrates. Also the outer covering layer of cells form an epidermis (lacking a definite basement membrane), and the inner choanocyte layer form a choanoderm (also lacking a definite basement membrane). It may well be that these cell layers are not connected by electrical gap junctions, as in many animals, but some sponges possess syncytia - fusions of cells into a large multicellular mass, e.g. The only movements exhibited by some sponges are changes in the porocytes which may open or close the incurrent pores. Most sponges, however, are capable of local or general contraction due to forces produced by the pinacocytes, desmacytes or the myocytes. Many Desmospongiae can contract their whole surface as a result of contractions of fibre cells in the cortex and along the main channels. Dermal pores can open and close as a result of sphincter action or changes in the encircling cytoplasm, except in glass sponges in which the pores appear non-contractile but remain open. Oscula close on exposure to air, in response to injury, lack of oxygen, chemical irritation, extremes of temperature and sometimes also to touch.
The oscula also close when the sponge is in a small volume of water that is inadequate for waste removal. Apparently neither of the behaviours of oscula, dermal pores and choanocytes is correlated (?). Obnoxious stimuli are transmitted either not at all or at up to 3-4 mm maximum.The osculum is the most conductive area, especially in the direction away from the osculum, and the oscular rim is the most sensitive part. In the freshwater sponge Ephydatia each osculum is borne on the summit of a chimney-like tube. The flow rate inside the flagellated chambers is very slow at about 0.01 mm per second due to a slight pressure gradient regulated by the sizes of the oscula apertures.
This slow flow rate gives sufficient time for the filtration process, which removes food particles from the water.The flagella do not beat in coordination.
Each undergoes a spiral undulation that travels from the base to the tip and ensures that the water current travels in a single direction. The collars point towards the apopyle (the opening of the flagellated chamber to the excurrent canal in non-asconoid sponges with complex architecture) and the resulting current exits through the larger aperture. Smaller flagellated chambers are more efficient since they permit less stagnation.In leuconoids the water current is very slow in the flagellated chambers, allowing time for filtering and exchange of materials to occur. Food particles in the water current adsorb to or are filtered by the choanocyte collars and ingested into the cytoplasm. The microvilli of the collars of all sponges seem to be connected to one another by strands of mucus or glycoprotein, forming a very fine mesh capable of filtering bacteria from the water. In the large choanocytes the particles maybe wholly digested, but are usually either partially digested or passed straight onto the amoebocytes of the mesenchyme for intracellular digestion.
The smaller choanocytes of other sponges possibly have no digestive role but pass food directly onto the amoebocytes (?).
It is also possible that amoebocytes receive some particles absorbed directly through the walls of the incurrent passages (?). As they are motile (in all but glass sponges) the amoebocytes may transport food around the sponge body and pass it on to other cells (?). Other cell types also appear capable of capturing and ingesting food particles directly, should they come into contact with them (such as the cells lining the canals).
The collar units and choanoblasts of glass sponges are continuous with the trabecular (mesh-like or web-like) syncytium that forms the bulk of the sponge and nutrients may pass directly from the collar units to the rest of the sponge tissue via the connecting cytoplasmic bridges. Some sponges exude mucus or slime that has an unpleasant odour and may cause irritation to the skin on contact.EcologyMany animals live on or in sponges, exploiting their sessile habit. Coelenterates, bryozoans and barnacles may grow on the surface of sponges, whilst annelids and crustaceans often inhabit the water canals.
In one large specimen of loggerhead sponge (Spheciospongia) were found 16 352 Synalpheus shrimps.
Shrimps of the family Stenopidae, especially Spongicola, live in pairs in the spongocoel of glass sponges like Euplectella and Hyalonema. The shrimps enter the sponge when young and grow such that they can no longer escape through the oscular sieve plate and must remain trapped alive within the sponge.Sponges of the family Suberitidae grow on the snail shells inhabited by hermit crabs. The sponge grows to enclose the shell, the shell is dissolved and the crab occupies a spiral cavity in the sponge, which is lined by smooth fibrous tissue. Boring sponges may kill barnacles and other shelled animals by slowly boring through their shells.Large horny sponges live for 50+ years. Freshwater sponges are necessarily seasonal.Different sponge morphologies suite different waters. Flabellate (fan-shaped) and lamellate (vertical and sheet-like) sponges thrive in water with a constant current, and grow with their inhalent surface facing the current and their oscula point downstream. Deep-water sponges living on muddy bottoms have anchoring root tufts or long projections of spicules. Most marine sponges live in shallow water, from the tidal zone down to 50-m depth, and do not live in brackish water. A gemmule is a group of amoebocytes (archaeocytes?) with other amoebocytes forming a covering layer (of columnar cells) that secretes thick and hard inner and outer membranes. The amoebocytes receive glyco- or lipoprotein food reserves from special nurse cells (trophocytes).
The result is a round ball of archaeocytes, trophocytes and columnar cells, with a micropyle (pore) outlet.The freshwater sponges produce gemmules in autumn and then die. Upon hatching, cells stream out through the micropyle and form a young sponge in about one week.In marine gemmule producing sponges, the gemmule consists of an amoebocyte aggregation (archaeocytes?) with a flagellated columnar dermal covering and the gemmule becomes a free-living flagellated larva that swims as the flagella beat. Ova and spermatozoa are produced, possibly from archaeocytes, other amoebocytes or from choanocytes (?). The egg mother cell (ovocyte) is an enlarged amoebocyte that grows either by engulfing other amoebocytes or from nutrients supplied to it by trophocytes.
And then undergoes maturation divisions (the cell divides into daughter cells that mature into egg cells (ova)).Each sperm mother cell is an enlarged amoebocyte, or possibly a transformed choanocyte since whole flagellated chambers have been observed to transform into spermatozoa. The sperm mother cell becomes covered by one or more flattened covering cells, which derive from divisions of the sperm mother cell or from other amoebocytes. The enclosed spermatogonium undergoes 2-3 divisions to produce spermatocytes.The sperm are ejected in the out-going water current, often forming milky, smoke-like jets that may extend for several metres above the oscular vent.
In most species it appears that the eggs are also ejected, in which case fertilisation occurs in the external water, but in some species, the sperm enter the recipient sponge in the water current and fertilisation is internal. In the species Reniera the sperm enters an amoebocyte, which transfers the sperm to the egg.The fertilised egg undergoes unequal holoblastic cleavage to produce a blastula (a hollow ball of cells), inside the recipient sponge.
This larva swims for several hours before attaching and developing into a sponge.Most sponges are hermaphroditic (they produce both eggs and sperm), but some are dioecious (have separate sexes).
Hermaphrodite individuals often produce eggs and sperm at different times, whilst some produce sperm apically and eggs basally.




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