University of the Philippines BaguioCollege of ScienceDepartment of Biology

Exercise No. 4

The Calcareous Sponges, Glass Sponges, and Demosponges of the Phylum Porifera

(Worming Dead S1) De Jesus, M.P.; Magaoay, A.C.L.; Pitoc, M.T.R.; San Pedro, S.M.S. & Tade, C.M.E.20 February 201520 February 2015

Introduction

A. Background of the Study

Porifera in Latin means pore bearing. This phylum’s defining characteristic is having microvillar collars which surround the flagella and it has units that arise from either single cells or syncytia (Pechenik, 2014).

Most sponge species are in marine environment but there are some on freshwater. They are mostly attached and sessile stationary animals. Sponges provide habitat for a number of animals and even bacteria and cyanobacteria (Pechenik, 2014).

They lack nerves and musculature. They eat the food particles that are floating in water. They don’t have organ systems like reproductive, digestive, and so on. There are 20 distinct cell types that are present in sponges (Pechenik, 2014).

Sponges are lined with flagellated cells in its inner surface. The empty space is the spongocoel. The cells lining the spongocoel are called choanocytes or collar cells. Adjacent to the choanocyte layer there is the nonliving layer called mesohyl layer. The amoeboid cells that move through the mesohyl are called archaeocytes. They are responsible for digestion and takes part in elimination of wastes. Eventually they would become specialized and secrete supporting elements found in the mesohyl layer. These supporting cells are either calcareous or siliceous spicules or they may be fibers that contain collagenous protein called spongin. The cells that secrete spicules are called sclerocytes and those that secrete sponging fibers are called spongocytes. These elements are for support and also for identification. For fresh water sponges they have dormant structures called gemmules. These are resistant to desiccation, freezing and anoxia. Gemmule formation is an effective means of asexual reproduction (Pechenik, 2014). Another means of reproducing is by budding. Most poriferans are hermaphrodites. They produce both eggs and sperms but at different times (UCMP, n.d.).

There are also flattened contractile cells on the outer surface of sponges called pinacocytes. They form a layer called pinacoderm. For most sponges, their pinacocytes don’t have a basal lamina. The contraction of pinacocytes results to minor and major shape changes. They also take part in regulating water flow. Some pinacocytes are ciliated (Pechenik, 2014).

Sponges rely on water flow for gas exchange, food, waste removal and the dissemination and collection of sperm. The water flows through narrow openings called ostia and they exit via large openings called oscula (Pechenik, 2014).

The sponges’ morphology advance in order to aid in maximizing the current flow through the spongocoel and to increase the amount of surface area for food collection. The three basic levels of sponge construction are asconoid, syconoid and leuconoid. Each reflects a higher degree of evagination of the choanocyte layer away from the spongocoel. This increases the surface area within the sponge (Pechenik, 2014).

Sponges are distributed into four classes based on chemical composition and morphology. These are Calcarea, Demospongiae, Hexactinellida and Homoscleromorpha (Pechenik, 2014).

B. Significance of the Study

Studying porifera or sponges provides “insight to key evolutionary transitions, such as emergence of multicellularity and the nervous system”. They could also synthesize compounds that have biotechnical applications (Thacker, et al., 2014).

C. Objectives of the Study

In this experiment, different slides were studied under the microscope. Stipules were seen and differentiated as well. Preserved poriferans were also observed. Characterization was also done to enhance knowledge regarding the Phylum Porifera.

Materials and Methods

Using the compound light microscope and some prepared slides, the students were able to determine and differentiate the specimens from the phylum Porifera, and this includes species under: class Calcarea, class Demospongiae and class Hexactinellida.

Upon preparing the compound light microscope, several prepared slides were given by the instructor and among those species given, the longitudinal and cross section of Grantia sp., Spongin skeleton, Leucosolenia spicules, Spongilla spicules, Grantia spicules and other kinds of spicules were then observed under the microscope. In addition, Euplectella aspergillum encased in a clear plastic and species such as the Spongia, Clathria prolifera and

Halidona porifera each contained in labeled jars were also observed. For the species under class Calcarea which includes Grantia sp., the ostium or prosopyle, incurrent canal, choanocyte chamber, apopyle, spongocoel, osculum, pinacoderm, choanoderm, mesophyll layer were examined if such of these parts can be seen in the longitudinal and cross sectional view of the specimen. Another species belonging to the said class is the Leucosolenia spicules as well as the Grantia spicules. The spicules of the phylum Porifera were primarily identified under the microscope due to their appearance and classification, namely: monaxons, triaxons, tetraxons and polyaxons. For the subsequent species, the Spongin skeleton, Spongilla spicules, Spongia, Clathria prolifera and Halidona porifera all belong under the class Demospongiae while the Euplectella aspergillum belongs to the class Hexactinellida.

Results

The Grantia sp. have a syconoid type of canal system, both the longitudinal section and cross sectional view exhibits the ostium or prosopyle which is the opening located at the peripheral region of the organism; the incurrent canal serves as a channel where water flows inside the system; the choanocyte chamber is the sac like cavity lined by choanocytes between the inhalant and exhalant systems; the cell lining of this cavity is then called the choanoderm; after water goes through the chamber, it exits into the apopyle, an opening pore before the spongocoel then exits through the osculum although these structures can be elaborately seen using the longitudinal section. This species has three dermal layers the outermost being the pinacoderm, the mesophyll layer in between and the innermost is the choanoderm.

Spongilla spicules, Leuscosolenia spicules and other spicules that were found and viewed under the microscope were the monaxons, triaxons, tetraxons, polyaxons and microscleres. Among the monaxons, monactines and diactines were observed. Under the monactines, several of them were classified as “style” which resembles a stake and the other is the “tylostyle” which looks like a phallus, for the diactines, “oxea” have tapering ends and “tylote” has knob-like ends. In triaxons, “triactine régulier” and “triactines en diapson” are frequently seen, also “calthrops”, “forceps” and “pectactine” were found which are types of tetraxons. “Sigmas” a microsclere was observed and also a fragment of a megasclere. But aside from the usual narrow structures, there was also a circular spiky structure found that may be either “sphaeractine” which is a polyaxon or a “polyactine”.

Several Spongin fibers were also viewed under the microscope, these are skeletal materials that are flexible and made from protein. The external features of the Euplectella aspergillum was similar to the structure of a vase which gained its name “Venus flower basket” and also because of fibers that makes up its body structure. The Spongia, Clathria prolifera and Halidona porifera were all contained in jars submerged in a solution and had undergone preservation processes which in turn lost its natural color and turned brown.

Discussion

Porifera is an animal phylum consisting organisms that is generally called as sponges. It is the only phylum of the animal subkingdom Parazoa and characterizes the least evolutionarily advanced group of the animal kingdom. Sponges are subdivided into three classes (Columbia Electronic Encyclopedia, 2012).

Class Calcarea (Calcareous Sponges)

Sponges in this class are identified by skeletal spicules that are composed of calcium carbonate. The spicules often protrude through the epipinecodermal covering of the body wall that gives the organism a rough texture. Although several species are brightly colored, calcareous sponges are generally dull in appearance. They are also small, usually only a few inches high. (Columbia Electronic Encyclopedia, 2012). Members of this class are among the simplest sponges, and include all three types of body construction—asconoid, syconoid, and leuconoid (Pechenik, 2014). When spicules are present, they are not fused and are usually monaxons and/or tetraxons (Invertebrate Paleontology, n.d.).

Class Hexactinellida (Glass Sponges)

These are deep-sea sponges that have skeletons that are composed of spicules of silica and they lack epidermal covering. Glass sponges are pale in color and are cup- or basket-shaped (Columbia Electronic Encyclopedia, 2012). Their canal systems may be either syconoid or leuconoid. The outer layer of Hexactinellida are syncytial (having many nuclei within a single plasma membrane) and there is no presence of a pinacoderm layer which makes them different from other sponges (Pechenick, 2014). Sponges with siliceous spicules that are usually triaxons and commonly fused to form a net or box-like pattern (Invetebrate Paleontology, n.d). The osculum is covered by a grillwork of fused spicules and the spongocoel is big. The cylindrical skeleton sometimes has the appearance of spun glass when the living tissue is removed. The glass sponge known as Venus's-flower-basket ( Euplectella ) serves as home for shrimps that is trapped by the lattice of spicules. (Columbia Electronic Encyclopedia, 2012).

Class Demospongiae (Demosponges)

Most sponges belong in this class. It includes sponges with a skeleton made up of silicon-containing spicules or spongin fibers or both. In the latter case, the spongin provides a matrix in which the spicules are surrounded. The Demospongiae vary in size from small, encrusting forms to very large, irregular masses. All are leuconoid; many are brightly colored. The freshwater sponges (family Spongillidae) belong to this class and they are frequently green because of symbiotic algae that live in the amoebocytes (Columbia Electronic Encyclopedia, 2012). When present, spicules are commonly monaxon, tetraxon, or polyaxon, but never triaxon (Invertebrate Paleontology, n.d.).

Class Homoscleromorpha

Class Homoscleromorpha is formerly considered as class Sclerospongiae. They are generally found in coral reefs that are in deep water or in caves. Although most of them lack spicules, when

spicules are present, they are completely siliceous like in hexactinellid, but they have distinct different morphology. In addition to these, they possess distinct basal membrane and their epithelial cells have cilia (Pechenik, 2014).

Spicules and Spongin Fibers

Spicules and spongin fibers are skeletal structures of sponges. Spicules are formed by carbonates of lime or silica in the form of needle like fragments. Spongin fibers are composed of a silk-like scleroprotein (Chandra, n.d.).

Major part of skeletal system of sponges is constituted by spicules. They are secreted by special mesenchymal cells called scleroblasts. They radiate from the center in the shape of spines or rays. Spicules have a core of organic material which is deposited either calcium carbonate or silica (Chandra, n.d.).

Secretion by specialized mesenchyme cells known as scleroblasts leads to formation of spicules. Calcoblast is a scleroblast secreting a calcareous spicule while a producing siliceous spicule is called silicoblast. Because of the incomplete division of scleroblast, cell giving rise to binucleate scleroblast monaxon spicules are formed. The two nuclei initiate to move away from each other. Calcium carbonate from sea water begins to deposit in between the space of two nuclei forming an axis. The cell divides into two, the founder cell and the thickener cell as the calcium carbonate needle between the nuclei begins to lengthen. When the spicule is completely formed, both the cells detach and goes off into the mesenchyme. Triradiate spicules are concealed by three scleroblast cell which lie in a triangular manner (Chandra, n.d.).

Spicules have two types base on the formation of materials: Calcareous which is made of calcium carbonate and is a characteristic of the class Calcarea and Siliceous which is made of silica and found in the class Hexactinellida (Chandra, n.d.).

According to the size, spicules are classified into two major types. Megascleres are in large size and constitute main supporting framework of sponge body. Microscleres are small-sized and appear in the mesenchyme (Chandra, n.d.).

There are three types based on the number of axis present in the rays of spicules. Monaxon are spicules that grow sideways in a single axis. These can be straight needle-like or rod-like. Their ends may be pointed, knobbed or hooked. If a spicule has only one pointed end it is called monoactinal. If there are two points it is called diactinal. But if it has a disc at both ends it is amphidisc. Triaxon spicule produces six-rays that has three axes and cross one another at right angles. These are found only in class Hexactinellida. Tetraxon spicules are made up of four rays radiating from a common point. Triradiate are also tetraxons in which one of the four rays is lost. All rays are equal in calthrops. Polyaxon is a type of spicule that radiates from a center point with numerous equal rays. They are usually common among the glass sponges (Chandra, n.d.).

Spongin is an organic elastic substance containing scleroprotein that is rich in sulfur and is chemically similar to collagen. It contains hydroxyproline and glycine in large amounts and also contains glucosamine, glucose, galactosamine and galactose

mannose, fucose, arabinose and uronic acid. Spongins are soluble in KOH but insoluble in water and acids. It cannot be digested by the digestive enzymes and it is chemically inert. Spongin also contains great amount of iodine (Chandra, n.d.).

Spongin fibers are made of an axial core that is surrounded by helically coiled fundamental fibrils which are secreted by the spongioblast cells derived from the mesenchyme. The spongioblast cells are arranged in rows and the collection of sponging materials leads to the development of a vacuole. Later, spongin secreted by each spongioblast cell joins with the next cells to form long fibers. To provide firmness to the sponge body, spongin fibres form a network (Chandra, n.d.).

Grantia sp.

Grantia is a genus of calcareous marine sponges. This group of sponges establishes the sycon body plan in which the wall of the group is folded into a sequence of internal and external canals wherein water circulates to bring in dissolved oxygen while eliminating waste products (Kelly, et al., 2003).

Water enters a Grantia sponge through several incurrent canals (ostia) and passes through internal pores or prosopyles that act like flood gates or valves. The incoming water that bears dissolved oxygen, dissolved solids, and suspended food like plankton and bacteria, enters the radial canals that are lined with choanocytes. These choanocytes are flagellated collar cells that keep the water moving throughout the sponge. By the use of flagella, the water is moved through. Suspended food particles are strained through the choanocytes and then digested through phagocytosis by amebocytes. The amoebocytes transport nutrition to other parts of the sponge colony and acts as the circulatory system of the organism. Water from the radial canals enters the central opening (spongocoel) through apopyles which are small pores. The exit for the sycon type sponges is a single and moderately larger opening that is referred as the osculum (Kelly, et al., 2003).

Sponges including Grantia exhibit only two germ layers, the endoderm and ectoderm. There is no mesoderm as with more advanced invertebrate and vertebrate animals. Another primitive characteristic of sponges is the option of sexual or asexual reproduction. Sexual reproduction allows genetic mixing while budding and fragmentation allows Grantia sponges to form same offspring. Environmental conditions including water temperature, tidal stage, and the phase of the moon are considered for these sponges to reproduce sexually (Kelly, et al., 2003).

Euplectella aspergillum

Euplectella aspergillum having a large central atrium, is a thin-walled, cylindrical, vase-shaped tube. The body is composed entirely of silica in the form of 6-pointed siliceous spicules. In the case of glass sponges like Euplectella aspergillum, the spicules are arranged together to form a very fine mesh that gives the sponge’s body a firmness that is not found in other sponge species. This also allows glass sponges to survive at great depths in the water column. There is more siliceous tissue called a syncytium which forms very fine fibers covering the framework of spicule, which look like a web over the framework. The syncytium shows that the sponge has a frame of tissue with no distinct cell boundaries but that have stacks of nuclei.

The top of the sponge has a sieve-like disc over the end and this helps for anchorage in to the substrate by the presence of fine, hair-like fibers. Recent study has proved that these fibers have the same arrangement as in optical cables like those used in present communications. They trap and convey light. One of the theories why sponges do this is to attract symbiotic algae or as an attractant for the shrimp which lives within the sponge’s body cavity (Encyclopedia of Life, n.d.).

References:

Book:Pechenik, J.A. 2014. Biology of Invertebrates, Seventh Edition. New York: McGraw-Hill Education.

Internet:

Columbia Electronic Encyclopedia. (2012). Porifera: Porifera: Class Demospongiae (Demosponges). Retrieved 25 February 2015 from http://www.infoplease.com/encyclopedia/science/porifera-class-demospongiae-demosponges.html#ixzz3SigvofuU

Columbia Electronic Encyclopedia. (2012). Porifera: Class Calcarea (Calcareous Sponges). Retrieved 25 February 2015 from http://www.infoplease.com/encyclopedia/science/porifera-class-calcarea-calcareous-sponges.html#ixzz3SigZl4z9

Columbia Electronic Encyclopedia. (2012). Porifera: Class Hexactinellida (Glass Sponges). Retrieved 25 February 2015 from http://www.infoplease.com/encyclopedia/science/porifera-class-hexactinellida-glass-sponges.html#ixzz3SighGryG

Columbia Electronic Encyclopedia. (2012). Porifera: Introduction. Retrieved 25 February 2015 from http://www.infoplease.com/encyclopedia/science/porifera.html#ixzz3Sih1me30.

(n.d.). Invertebrate Paleontology. PROTOCISTA, EUBACTERIA, & PORIFERA. Retrieved 25 February 2015 from http://paleo.cortland.edu/tutorial/Protista/porifera.htm

(n.d.). Encyclopedia of Life. Euplectella aspergillum. Retrieved 25 February 2015 from: http://eol.org/pages/1033413/overview

Kelly, C.D. et al. (2003) Grantia Sponge. Retrieved 25 February 2015 fromhttp://micro.magnet.fsu.edu/optics/olympusmicd/galleries/darkfield/grantia.html

(n.d.). Les Spongiaires. Retrieved 25 February 2015 from http://paleopedia.free.fr/spongiaires.html

(n.d.). Chandra, G. Skeletal Structures In Porifera. Retrieved 25 February 2015 from http://www.iaszoology.com/skeleton-in-sponges/

(n.d.). UCMP. Porifera: Life History and Ecology. Retrieved 25 February 2015 from http://www.ucmp.berkeley.edu/porifera/poriferalh.html

Journal:

Thacker, R.W., et. al. 2013. "The Porifera (PORO): Enhancing Plant Systematics with an Anatomy Ontology". Journal of Biomedical Semantics.

Answers to Questions

Class Calcispongiae

1. Are ova or embryos present in the prepared slide?

Yes. Embryos were present in the prepared slide of Grantia sp. The ova were most prominent in the cross section of the specimen.

2. What is the body type called?

Members of this class are among the simplest sponges, and include all three tpyes of body construction—asconoid, syconoid, and leuconoid (Pechenick, 2014).

3. What determines the complexity of the canal system?

Each form reflects an increased degree of evagination of the choanocytes layer away from the spongocoel that increases the the extent of the flagellated surface area in the sponge. The complexity of the canal system depends on the greater amount of surface area that is available for food collection (Pechenick, 2014).

Spicules and Spongin Fibers

1. What are the functions of the spicules and spongin skeleton?

Spicules and spongin fibers are skeletal structures found in sponges and they are main frame work that act as a support. They give rigidity and firmness to sponges (Chandra, n.d.).

2. How they are formed?

Secretion by specialized mesenchyme cells known as scleroblasts leads to formation of spicules. Calcoblast is a scleroblast secreting a calcareous spicule while a producing siliceous spicule is called silicoblast. Because of the incomplete division of scleroblast, cell giving rise to binucleate scleroblast monaxon spicules are formed. The two nuclei initiate to move away from each other. Calcium carbonate from sea water begins to deposit in between the space of two nuclei forming an axis. The cell divides into two, the founder cell and the thickener cell as the calcium carbonate needle between the nuclei begins to lengthen. When the spicule is completely formed, both the cells detach and goes off into the mesenchyme. Triradiate spicules are concealed by three scleroblast cell which lie in a triangular manner (Chandra, n.d.).

Spongin fibres are made of an axial core that is surrounded by helically coiled fundamental fibrils which are secreted by the spongioblast cells derived from the mesenchyme. The spongioblast cells are arranged in rows and the collection of sponging materials leads to the development of a vacuole. Later, spongin secreted by each spongioblast cell joins with the next cells to form long fibers. To

provide firmness to the sponge body, spongin fibres form a network (Chandra, n.d.).

Class Demospongiae

1. What type of canal system does it have?

It has a leuconoid construction and it is the most complex among the three constructions because of the increased degree of evagination of the choanocyte layer away from the spongocoel (Pechenik, 2014).

2. What features distinguish them from other classes?

The spicules of and fibers of this class maybe composed of spongin and/or silica but not calcium carbonate. Recent study shows that the skeletal fibers of this class also contain chitin (Pechenik, 2014). Spicules that are present in this class are commonly monaxon, tetraxon, or polyaxon, but never triaxon (Invertebrate Paleontology, n.d.).

Class Hexactinellida

1. What type of canal system does it have?

Hexactinellid canal systems may be either syconoid or leuconoid (Pechenik, 2014).

2. What features distinguish them from other classes?

Skeletons of this class are composed of spicules of silica and they lack epidermal covering. Glass sponges are pale in color and are cup- or basket-shaped (Columbia Electronic Encyclopedia, 2012). The outer layer of Hexactinellida are syncytial (having many nuclei within a single plasma membrane) and there is no presence of a pinacoderm layer which makes them different from other sponges (Pechenik, 2014). Sponges with siliceous spicules that are usually triaxons and commonly fused to form a net or box-like pattern (Invertebrate Paleontology, n.d.). The osculum is covered by a grillwork of fused spicules and the spongocoel is big (Columbia Electronic Encyclopedia, 2012).

Appendix

Figure 1. Types of SpiculesImage retrieved from http://oceanlink.info/LEYS/images/SPICULES.gif

Figure 2. Types of Canal SystemsImage retrieved from http://biophysics.sbg.ac.at/png/scans/spongasl.jpg

Figure 3. Euplectella

Figure 4. Clathria prolifera

Figure 5. Spongia

Figure 6. Halidona porifer

Figure 7. Monaxons Image retrieved from http://paleopedia.free.fr/spongiaires.html

Figure 8. Triaxons Image retrieved from http://paleopedia.free.fr/spongiaires.html

Figure 9. Tetraxons Image retrieved from http://paleopedia.free.fr/spongiaires.html

Figure 10. Polyaxons Image retrieved from http://paleopedia.free.fr/spongiaires.html

Figure 11. Microscleres Image retrieved from http://paleopedia.free.fr/spongiaires.html