13. The oscules, quite visible, are located at the intersections of the largest tubes. Such inclusion has recently been chal­lenged by O. Tuzet, who after studying sponges for many years has again claimed that porifera has given rise to the true metazoans. Inner surface of the body is lined by spe­cialised cells, the choanocytes. A sponge’s skeletal type adapts well to its particular habitat, allowing it to live on hard, rocky surfaces or soft sediments such as sand and mud. (With Methods)| Industrial Microbiology, How is Cheese Made Step by Step: Principles, Production and Process, Enzyme Production and Purification: Extraction & Separation Methods | Industrial Microbiology, Fermentation of Olives: Process, Control, Problems, Abnormalities and Developments, The best answers are voted up and rise to the top. Sponges are thought to have evolved around 500 million years ago, and today there are more than 5,000 known species of sponge with another 5,000 species thought to have not yet been discovered. Most calcareous sponges in the fossil record were classified as either stromatoporoids, chaetetids, archaeocyaths, inozoans, pharetronids, or sphinctozoans. However, they … After a brief swimming period they become attached by their anterior ends and develop into flattend plate-like structure with an ir­regular outline. Habitat information for each species was taken from Fetzner ... Wörheide G (2006) Non-monophyly of most supraspecific taxa of calcareous sponges (Porifera, Calcarea) revealed by increased taxon sampling and partitioned Bayesian analysis of ribosomal DNA. They are common in the Paleozoic and Mesozoic, however, rare in the Cenozoic. The genus Clathrina (Gray, 1867) has an asconoid aquiferous system, one of the simplest organization among sponges, which means that all the cavities are lined by choanocytes (Klautau & Valentine 2003). The cells of sponges show a high degree of independence. Vital functions are performed by independent ac­tivities of the cells. Calcareous sponges (Class Calcarea) include about 675 accepted extant species (Van Soest et al., 2011), which are exclusively marine. The constituent cells exhibit less differ­entiation but are involved in several complicated organisations, i.e., forma­tion of gemmules. 5. 4. They have all in common certain structural features. They lack mouth and digestive cavity. Common along the Atlantic coast of Europe, from the Mediterranean to the coast of Norway. Molecular Phylogenetics and Evolution 40: 830–843 . This phenomenon is called de-differentiation (Fig. The amoebocytes with blunt pseudopods, conspicuous nu­clei with large nucleolus are referred to as the archeocytes. Most sponges live in a salt water environment, attached to objects on the sea floor. Give the general characteristics of the Phylum Porifera. Clathrina clathrus is a calcareous sponge of 10 cm in diameter forming a tangle of tubes which are between 0,5 and 3 mm in diameter and interconnected in a very dense network. The closure of the pore is effected by the advancement of a thin cytoplasmic sheet called the pore diaphragm from the margin to the centre at the outer end of canal. In tropical coral reefs, they dwell mainly in shaded and/or cryptic habitats and prefer calmer waters. Disclaimer Copyright, Share Your Knowledge 3. be fixed or preserved in formali n. All are aquatic; mostly marine (98%) but a few are freshwater … Although most of the species are found in tropical waters, there are approximately 10 species along the coast of Norway. Certain sponges, e.g., Tethya can contract its entire body, while in most cases the contractility is restricted around the osculum. There are about 5,000 to 10,000 species of sponges found mostly in marine environments with about 100 species of freshwater sponges. Of the 15,000 or so species of Porifera that exist, only 400 of those are Calcareans. There are 3 kinds of sponges, and they live in different habitats: Calcarea: * Water type: Marine * Depth: Less than 100 m … Demospongiae (at least 80%) if have Spicules usually four-rayed composed of silica, lack spicules and have spongin and some have both, all have Leuconoid canal. Sponges were included under coelenterates throughout much of the nineteenth century, though de Blainville (1816) proposed to separate sponges from coelenterates and cre­ated a group Spongiaria having relationship with protozoa. The Phylum Porifera includes nearly 8500 described species. 11.15). Stromatoporoids filled the same ecological niche as the stony corals of today, and thus, played the same role in reef construction. There are various types of sponges rang­ing from simple to complex. Our mission is to provide an online platform to help students to share notes in Biology. Gradually a cavity is developed and is lined by a layer of porocytes. Most are filter-feeders/suspension feeders, Most are marine, No true tissue or organs, Adults are sessile, Filled with holes. Spongillidae). Such dissociated cells, if kept un­der water, aggregate again and form the sponge body. The most widely known fossil genus is Archaeocyathus. Some of the flag­ellated cells loss their flagella pass into the central cavity and become amoeboid. The choanoflagellates bear some features which are compared with the choanoflagellates (collar cells) of sponges. Sucks water into extracts food in water then pushes water back out, Describe the two forms of asexual reproduction in the sponge, External budding: keeps growing on the outside of it then separates after getting so big. Many annelids and crustaceans live as symbionts with sponges. Linnaeus, Lamarck and Cuvier considered the sponges related to anthozoan polyps and included the sponges within zoophytes or polyps. Absence of definite germ layers which are the most diagnostic feature of metazoans. In some calcareous sponges (e.g., Clathrina, Leucosolenia), Hexactinellida and most Demospongiae the embryos release as free-swimming coeloblastula (hollow blastula) stage (Fig. 8. Phylogeny. Calcarea sponges are found throughout the oceans, but are mainly in temperate areas. On the contrary, there are certain features in sponges which may be considered as unique to them. So the claim of the ancestry of sponges from a protistan choanoflagellate is almost refuted by the appearance of collar cells in other groups of metazoans. The spongocoel corresponds to the coelenteron of the coelenterates but pores and network of choanocyte-lined canals are not seen in any metazoan group. The cleavage is holoblastic and may be equal or unequal. These features with monociliated flagella of sponges indicate that sponges have evolved directly from a protistan ancestor. Biology, Articles on Animals, Phylum Porifera, Sponges. The porocytes are also highly contractile. Regeneration 9. Sponges can regenerate their lost parts very rapidly. The amoebocytes are most important cellular entities in the life of sponges. The archeocytes are actually the generalised amoebocytes which play the domi­nant role in regeneration, reproduc­tion and differentiation of other cell- types. Calcareous sponges. The color is white, grey or light brown. Rapp et al., 2011). Briefly describe the main differences between the syncytial ciliate hypothesis, the colonial flagellate hypothesis and the polyphyletic origin. Which one is also called gemmules? Invertebrate … Calcareous sponges take a wide range of shapes, including irregular massive forms, vase-shaped bodies on a stalk or meshworks of thin tubes. Unlike other metazoans reversal of germ layer takes place in sponges. ... Calcareous sponges . Asconoid canal system: simplest filtration (ostia, porocyte (creates a canal), spongocuel (lined with choanocytes), osculum). They are the simplest colonial sponges look like little bunches of bananas and most can be found attached to hard substrates in tide pools (shallow water and rocky seashore). Their skeletal structure is made up of large spicules of calcium carbonate. 14. Calcareous sponge, any of a class (Calcarea) of sponges characterized by skeletons composed entirely of calcium carbonate spicules (needlelike structures). For this reason amoe­boid cells are regarded as totipotent cells. Gradually the peripheral cells of the newly formed aggregate form pinacocytes. The ability of amoeboid cells to be­come another cell-type speaks that in the group of sponges determination is not rigid like other metazoans. Calcareous sponges occur mainly on the rocky bottoms of the continental shelves in temperate, … The sponges represent a parazoan grade of body construction where true embryonic germ layers are wanting. Most of the inner amoeboid cells migrate to the outer surface and form the dermal epithelium and mesenchyme. The surface of the body or epidermis is lined by pinacocytes. Calcareous Estate wines are produced from grapes grown at one of our 3 vineyards. Content Guidelines 2. Furthermore, glass sponges are highly unusual in that their major tissue component is a giant "syncytium" (see below) that ramifies throughout the entire body, stretching like a cobweb over the … There are several views regarding the origin of sponges. What is the most characteristic feature of the Phylum Porifera? Which group of organisms usually forms gemmules and why? The tetra-radial symmetry exhibited by the larvae of calcareous sponges is com­parable with that of the larvae of polychaetes, sipunculids and gastropods. With the increase of the size of cavity it is bounded by porocytes and flagellated cells. 20. Within the aggregate, all the cells lose their identity and become homo­geneous. What are the general characters of bryophytes? Thus sponges are again proposed to be shifted in the high way of metazoan evolu­tion and have been placed in between pro­tozoa and cnidarians as phylum Porifera (Fig. Both the cell layers lack the base­ment membranes or basal lamina but occurs in other metazoan epithelia. This continues for 4-6 hours. Due to farming practices and the nature of the land, these vineyards produce tiny yields, resulting in fruit of profound depth and sense of place. The wall of sponges consists of an outer epithelium, called pinacoderm, compos­ing of flat, polygonal cells, the pinaco­cytes, and an inner single epithelial layer containing microvillous collard, flagel­lated choanocytes, called the choanoderm. They are sessile and sedentary animals. When the mesenchyme con­tains few cells—this is called collenchyma. The outer single layer wall of the central cavity contains elongated monoflagellated cells except the posterior side where a few rounded granular non-flagellated cells, called archaeocytes, are present. Adult sponges are sessile animals that live attached to hard rocky surfaces, shells, or submerged objects. This type of sponge comes in a variety of colors, including gray, green, purple or blue. The body surface is perforated by pores acting for ingress of water. The calcareous sponges of class Calcarea are members of the animal phylum Porifera, the cellular sponges. General Features 4. The largest sponge is Spheciospongia vesparum having a diameter of two metres. Calcareous Sponges-The calcareous sponges of class Calcarea are members of the animal phylum Porifera, the cellular sponges. Description. Sexual repro­duction by sperms and ova. Why were the sponges placed in the Kingdom Plantae for so many years? In what type of habitat do you find these sponges? The processes in gametogenesis, i.e., production of sperm and ovum, are same as in other metazoans. 11.16). A mesen­chyme containing skeletal spicules and sev­eral types of free amoeboid cells are present between the epithelia. The more complex? Sponges range in habitat from shallow intertidal areas and coral reefs to the deep sea. Most are small, seldom exceeding 15 cm (6 inches). Fossil sponges were discovered from beds of Europe, Asia and North America, which are more than 600 million years old. The mesohyl is poorly defined and contractility is restricted only to the region of the osculum. There must be distinct differentiation of somatic and germinal parts of the body. In Calcareous sponges, reproduction can be both sexual and asexual, by budding. However, studies have shown that the Homoscleromorpha, a group thought to belong to the Demospongiae, is actually phylogenetically well separated. Less than 200 sponge species inhabit freshwater habitats. Rarely are they found completely free-floating. It may form a syncytium in some cases. Calcarea sponges were important reef builders in the Permian and Triassic. During unfavourable condition most sponges shrink and form restitution bodies, which grow in favourable condition. Scientists have identified around 400 species of calcareous sponges. A true metazoa will develop from a unicellular zygote and will pass through stages like blastula and gastrula. These usually have three points, but some species have two or four pointed spicules. The sponges exhibit close protozoan affinities but the attempts to in­clude sponges under the Phylum Protozoa failed because of the development of germ layers in developing sponges. These include four main classes, glass sponges, calcareous sponges, demosponges, and homoscleromorpha. Briefly describe the process of sexual reproduction in the sponge (include the difference between parenchymula and amphiblastula.). Typically, the Calcarea are very small, measuring about 7-10 cm (3-4 inches) in height. A few fossil representatives are known from the Burgess Shale (a rock formation deposited about 505 million years ago) in British Columbia , Canada. Porifera are asymmetrical or superficially radially symmetrical metazoa with cellular grade of organization without tissues, organs, and with a porous body and a canal system lined by choanocytes. Porifera are a part of the kingdom Anamalia (which contains roughly 35 phyla), and the domain Eukarya.Porifera contain three main lower classes, Hexactinellida (glass sponges), Calcarea (calcareous sponges - having spicules), Demospongiae (demosponges), and Scleropongiae(coralline or tropical reef sponges). Calcareous sponges (class Calcarea) are represented by sponges with calcite spicules. 11.14B). Common names are listed, if known. Calcareous sponges occur mainly on the rocky bottoms of the continental shelves in temperate, shallow waters; they are usually dull in colour. Almost all sponges function first as one sex and then as the other. ... new RNA evidence suggest that Calcareous sponges are closer related to ther metazoans than to siliceous sponges. 16. (Wörheide, 2002) Biogeographic Regions; arctic ocean; indian ocean; atlantic ocean; pacific ocean; mediterranean sea; Habitat. Habitat: S. quadrangulatum seems to prefer shallow waters, where it can be found attached … What is the one unique feature of the freshwater sponges? Tuzet (1963) ex­pressed the view that though sponges pos­sess many primitive features (such as cellu­lar grade of body organization, gas exchange, and response to external stimuli represent the unicellular protozoan-like animals), yet there is no doubt that they are in direct line of metazoan evolution. 1. Unlike the other two main classes of sponges (Calcarea and Demospongiae), glass sponges lack either a calcareous or organic skeleton. The low level of cel­lular differentiation and presence of canal system, cellular totipotency and absence of tissues, basement membrane, body polarity, reproductive organs and functionally inde­pendent cells indicate a primitive stage of metazoan organization. Some sponges even attach themselves to floating debris! 5. Male gives sperm out during reproductive time for most sponges then goes to female egg. With lobose pseudopods and many food reserves. Body is strengthened by an internal skel­eton of calcareous or silicious spicules or a collagenous fibres called spongin. H. V. Wilson (1907) for the first time demonstrated that a bit of sponge when squeezed through a silken mesh dissociates completely. 3. The mesohyl corresponds to the connective tissue of other metazoans. Ellis (1775) established the animal nature of the sponges. 9. Goals of the study were to compare the prokaryotic communities of demosponges with the calcareous sponge and octocorals and to … No one questions the multicellular nature of sponges. In the present study, we assessed prokaryotic communities of demosponges, a calcareous sponge, octocorals, sediment and seawater in coral reef habitat of the central Red Sea, including endemic species and species new to science. It … 7. Which of the canal systems is the most common? Red Boring Sponge SPONGE SPECIES All of the following sponges are found within the coral cap region of the sanctuary (0-130 ft, 0-40m deep). In simple asconoid sponges the wall is composed of an outer dermal epithelium or epidermis and an inner epi­thelium consisting of Choanocytes. Which of these is considered to be the simplest? The evolutionary origin of sponges poses some interesting problems for their peculiar features. How do the characteristics of this class differ from the other classes? Sponge systematics are difficult mainly due to the simple bauplan as mentioned above; definitive (true) synapomorphies are yet to be established. Their habitat include the Caribbean, Florida, and the Gulf of Mexico. Calcareous sponges live in diverse habitats. Reproduction both asexual and sexual. Not applicable; calcareous sponges are … They can be found living on coral reefs in the shallow waters of tropical regions. 11. This is followed by the appearance of flagellate cells, forma­tion of spicules and establishment of canals within the aggregate. Origin of Sponges: There is a great controversy regarding the origin of Porifera. 5. Spicual made of glass, Trabecular net, Six-rayed spicules. They are pierced by a central canal which acts as an incurrent passage. What are the other general characteristics of this class? Once differentiated, the germinal layers are irreversible in nature. 2. Sponges (Porifera) are a group of animals that includes about 10,000 living species. These views were ignored till the mid­dle of twentieth century, where they were treated as a separate side branch “Parazoa”. What are the different sources of air pollution? What structures prevent the collapse of the canals found in sponges? A common feature is the supporting skeleton, made of calcareous, star shaped structures - or spicules. Glass Sponges Existence of wide regenerative power in sponges and in many lower metazoans. should not. Habitat and Distribution Sponges are found on the ocean floor or attached to substrates such as rocks, coral, shells, and marine organisms. The development of sponges like Oscarella shows similar processes as in metazoa. Besides these cell-types long slender cells, called the desmocytes, are present specially in Demo- spongiae. What is the importance of the more complex canal system? 15. 4. Most of them are marine excepting 150 freshwater sponges of the family Spongillidae. Why does plant cell possess large sized vacuole? The peculiar event in fertilisation that two synergids direct the sperm towards the egg is found to occur in chaetognatha. These habitats have in common coldwater (35–52°F, or 2–11°C), relatively high levels of dissolved silica, and low light intensity. Sponges of this type include the Yellow tube sponge, Blue tube sponge, and the Stove-pipe sponge. They perform various functions and are re­sponsible for producing other cell-types by the process of transformation excepting pos­sibly the choanocytes. 5. Gradually small aggregates meet other cells or other similar aggregates and grow in size. Artificial cavities constructed of a synthetic polymer, FHP-3000, were used as substitutes for calcareous sponges [Leucetta losangelensis (de Laubenfels)] normally used as reproductive habitat by Paracerceis sculpta (Holmes), a Gulf of California isopod … Huxley (1875) and Sollas (1884) wanted the sponges to be separated from higher Metazoa. Cliona bores on the molluscan shell and is known as boring sponge. Bowerbank and Norman (1882), Hyman (1940), Hartman and Goreau (1970, 75), Berquist (1978, 85), Barnes (1980), Meglitsch and Schram (1991), Anderson (1998) and Brusca and Brusca (2003) classified the porifera into 3 classes but a new class Sclerospongiae added to a few decades ago but was rejected few years later. Have many colors and didn't move very much, scientist didn't know they moved. Definition and Origin of Sponges 3. How many marine species exist? Of the 15,000 or so species of Porifera that exist, only 400 … The spicules support the body wall and hold the sponges erect. ), which is a growing concern given CO 2-driven changes in the pH of seawater . These colonial "hard corals" may form elaborate finger-shaped, branching, or mound-shaped structures, and can create masses of limestone that stretch for tens or even hundreds of miles. Sponges were traditionally distributed in three classes: calcareous sponges (Calcarea), glass sponges (Hexactinellida) and demosponges (Demospongiae). The outer layer of cells is primarily responsible for protection and in­ner layer of cells carries on the nutritive func­tions. Pinacocytes may also line the spongocoel and incurrent canals of syconoid sponges and also the spaces in leuconoid sponges. The vast majority of hexactinellids live at depths greater than 1,000 ft (304.8 m). Mono: Most sponges, Has both male and female gonads, Somatic: Body cells, small piece off itself and will grow another sponge. Yeast: Origin, Reproduction, Life Cycle and Growth Requirements | Industrial Microbiology, How is Bread Made Step by Step? Deep-water sponge trap prey, no chonanocytes (no filtration), carnivorous. In most of the sponges the development takes place within the body of the parent but in a few of demospongiae the development of the fertilized eggs takes place in sea water. The mesoglea consists of a transparent gelatinous matrix of protein nature in which different types of cells like archaeocytes, amoebocytes, scleroblasts and germ cells are present. What you’re actually asking for are sponges. Gradu­ally these amoeboid cells fill up the cavity, forming a stereoblastula (solid blastula) and differentiate into parenchymula (also called Parenchymella) larva (Fig. But amoeboid cells may be transformed into any other cell-type. Body is perforated by numerous, minute inhalent pores—the ostia for ingress of water, hence the name of the group is called Porifera. There is no organ or organ system. All are aquatic; mostly marine (98%) but a few are freshwater (Fam. The class of the calcareous sponges, Calcarea, includes 400, strictly marine species. Amoebocytes with slen­der and branching pseudopods. These sedentaric animals usually stay in low depths and use solid surface for fixation, but glass sponge reaches at greater depth and anchors on soft sediments. Generally small in size, tubular, with calcium carbonate spicules, shallow water, all three tyoes of canal systems. The fact that the sponges evolved from the Protozoa and occupy a position between the Protozoa and Cnidarians is evidenced by the following arguments: 1. The cleavage of zygote results into a blastula stage (coeloblastula) which by invagination becomes gastrula. Give some examples of sponges belonging to this class. Although many hexactinellids require a firm substratum, such as rocks, for attachment, o… In some freshwa­ter species, the parenchymula larvae possess spicules and choanocytes but in Hexactinellid species, the parenchymula larvae contain both spicules and chamber lined with choanocytes. In tropical coral reefs, they dwell mainly in shaded and/or cryptic habitats and prefer calmer waters. Demosponges can grow quite large, to over 2 meters in … They are found in oceans and freshwater lakes throughout the world. Choanocyte cells are seen in some echinoderms and therefore, are not the only characteristics of sponges. They adhere to the coral, where they live for their entire lives. In most Demospongiae, the parenchymula larva develops directly from stereoblastula, hav­ing an external layer of flagellated cells and an inner mass of amoeboid cells, each cell contains single flagellum. The metazoans affinity obtained greater support from the study of spongin which has chemical and physical resem­blance with the collagen. Common sponges have skeletons made of the protein spongin (class Demospongea). Trypanosoma Brucei and Trypanosoma Cruzi | Phylum Protozoa. This idea takes following facts into consideration: 1. Recent work have established that the sponges are metazoan of lower grade of organisation. The collar cells or choanocytes are specialised cells with a rounded or oval base resting on the mesen­chyme and a contractile transparent collar which encircles the base of a single long flagellum. Multicellular organisms having cellu­lar grade of organization without true tissues. The choanocytes are diagnostic to the anatomy of sponges. Sponges represent the oldest form of metazoa. They occur mostly in shallow waters; only a few species are known from the deep sea (for an overview see, e.g. These data were collected under a cooperative agreement with the Massachusetts Office of Coastal Zone Management (CZM) and the U.S. Geological Survey (USGS), Coastal and Marine Geology Program. Instead, Devonian Period reefs were dominated by a group of calcareous sponges known as stromatoporoids. Like all other sponges, they are sedentary filter feeders. All sponges in this class are strictly marine, and, while they are distributed worldwide, most are found in shallow tropical waters. Answer Now and help others. They live underwater in calm waters in coral reefs. Trilobites were common only in the sublittoral zone. The calcareous sponge Paraleucilla magna,originally observed along the Brazilian coast (Atlantic Ocean), is the only allochthonous invasive species of Porifera reported in the Mediterranean Sea. The pore cells or porocytes occur among the pinacocytes at frequent intervals. The sponges appeared during the Pre- Cambrian Period and a large number of fos­sils have been recorded from the Palaeozoic era up to recent. The osculum in sponge apparently re­sembles the mouth of coelenterates, but developmentally the osculum does not correspond with it. What is an example of a sponge belonging to this class? Privacy Policy3. The cytoplasm of these cells contains many round inclusions. Generally, they are not as large or brightly colored as demosponges. Amoebocytes are amoeboid in nature. What is so unique about the sponge Family Gladorhizid? Approximately 90% of all sponge species are in this class.They are often brightly colored, unlike the dull glass and calcareous sponges. 7. Within the phylum Porifera, there is a genus of calcareous (i.e., made of calcium carbonate), branched sponges called Luecosolenia. Habitat 5. The amoebocytes are of several varieties in dif­ferent sponges. Calcareous sponges live in diverse habitats. What are the two most distinguishing features of the Class Hexactinellida? 21. Spicules are formed by the deposition of the scleroblasts. At the dissociated stage, amoeboid cells (archaeocyte and amoebocyte) and flagellate cells (choanocytes) show movement (Fig. These organisms are characterized spicules made out of calcium carbonate in the form of calcite or aragonite. The Devonian Marine Habitat ... made up of the familiar corals we see today. It can reach a length of 9 cm after a life span usually no more than one year. Welcome to BiologyDiscussion! Typically, the Calcarea are very small, measuring about 7-10 cm (3-4 inches) in height. It is totipotent in na­ture. The well-known enemies of sponges are coral-reef fish, limpets and nudibranchs. The primary objective of this program, initiated in 2003, is to develop regional geologic framework information for the management of coastal and marine resources. The developmental dynamics of calcar­eous sponges show close parallelism with that of Volvox. In m any species both . Each pinacocyte is a large flat polygonal cell. Many fusiform contractile muscle cells or myocytes are present around the osculum. adequate documentation (locality, habitat, surface feat ures, colour notes etc.). How many freshwater species exist? The interior of sponges has a single hollow cavity called the spongocoel or paragastric cavity lining the microvil­lous collard choanocytes in some and in majority of cases by folding of the wall of spongocoel, innumerable water canals form a complex structure (canal system) that drives water through the canals and conveys food and oxygen. The flag­ellate cells in the inner lining of the cnidarians also bring a close resem­blance. Before sharing your knowledge on this site, please read the following pages: 1. Describe in detail the structure of a choanocyte. Not applicable; calcareous sponges are sessile filter feeders. These cells are much larger in size in Calcarea than in other sponges. General Features of Sponges: 1. Share Your Word File Porocytes are tubular cells extending from the epidermis to the spongocoel. Members of this group include glass sponges, demosponges, and calcareous sponges. Explain the differences between the following types of cells found in the mesohyl; Pinacocytes and Choanocytes. 4. Sponge: zooxanthella symbioses are especially important given that Symbiodinium are predominantly associated with the bioeroding sponges that dissolve calcareous structures (e.g. Certain amount of organisations like connective tissues, nervous tissues, are ex­pected to be present even at the simplest form. Development 7. Be able to distinguish the difference between the following structures; osculum, ostia, choanocytes and mesohyl.
2020 calcareous sponge habitat