3.4 Choanocyte function—Feeding

The action of the choanocyte flagellum in generating a low push to attract water with the collar is well defined by Simpson (1984) from van Tright (1919) and Kilian (1952). Despite the basics are quite clear, precisely how the water moves with the collar and chamber is no actually known. For example, while the is understood that water complies with a press gradient generated by the choanocyte, as noted above, it is suggested that there must be one-way valves to protect against water from flushing the other means under changes in external pressure (Vogel, 1978). Though potential one-way valves (apopylar cells and also a glycocalyx mesh between the collars) have actually been determined by Langenbruch and Weissenfels (1987), it would certainly be an overwhelming to test just how they work. Also, whether all water have to pass through the collar filter or whether there room bypass canals is likewise not known. Some authors suggest that bypass structures exist, for example, to compensate for pressure changes that occur throughout rhythmic contractions (Nickel et al., 2006), and other authors, utilizing corrosion casts to research the aquiferous system, likewise find links between incurrent and excurrent canals (Bavestrello et al., 1988). However, since using corrosion casts may cause tearing or rupture that the canal system, doubt remains regarding whether such bypasses exist, particularly when the is considered that these would certainly generate leakage in the pressure mechanism that the choanocyte filter relies upon. Feeding research studies which display greater 보다 95% retention the bacteria heap et al., 1996; Yahel et al., 2003, 2007).

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Food record occurs in ~ choanocytes, prosopyles, and also incurrent canal epithelia (Kilian, 1952; Weissenfels, 1976; Imsiecke, 1993; Leys and also Eerkes-Medrano, 2006); also exopinacocytes have actually been shown capable of uptake of latex beads (Willenz and also Van de Vyver, 1982), for this reason epithelial cell in general must be qualified of phagocytosis. Normally however, bacteria and also other picoplankton are caught by pseudopodia in ~ the choanocyte, and also once in that cell, are transferred come amoebocytes for digestion and transfer of food to other cells in the sponge. The deliver of food in between choanocyte and also amoebocyte has been displayed by video clip microscopy by Imsiecke (1993), and between amoebocyte and other cell in a suite of research studies by Willenz and also colleagues (Willenz and also Van de Vyver, 1984, 1986; Willenz et al., 1986).


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4.3.1.1 Dendroceratida

All dendroceratid sponges own eurypylous choanocyte chambers. Eurypylous choanocyte chambers connect directly with inhalant and also exhalant canals, vice versa, diplodal choanocyte chambers attach only via a so-called prosodus or aphodus. Morphologically, Dendrocertida are separated into two families, Darwinellidae, which own a mostly dendritic skeleton (i.e. The skeletal aspects branch, yet do not rejoin) and also Dictyodendrillidae, which own a largely anastomose skeleton (i.e. The skeletal facets branch and also rejoin and might kind a network ) (Bergquist and Cook, 2002b). Published molecular data on dendroceratids room scarce (see, e.g. Borchiellini et al., 2004), however recent results based upon nuclear (28S rDNA) and mitochondrial (cox1) sequences support the monophyly that Dendroceratida if rejecting the monophyly of the two traditionally recognized households (Erpenbeck et al., unpublished data).


The an essential component the the suite of cell in a sponge body is the choanocyte. Choanocytes are dedicated cells that have actually a single flagellum surrounded by a net-like collar of microvilli (Figure 3). Choanocytes join together creating the choanoderm, whereby they carry out two major functions. The first is to develop a circulation of water and the second is to catch food items together they pass by these cells. The flow of water is initiated through the coordinated beating that flagella. Once water enters the sponge v ostia (Figure 1), the passes v a canal device of lesser or greater complexity, relying on the species, until it reaches the choanocytes. As soon as at the choanocyte, bacteria are caught in the microvillar net and also passed to archaeocytes within the mesohyl. Water exit the sponge through the osculum (Figure 1).


*

Figure 3. Choanocyte chamber from a leuconoid sponge the the genus Dysidea. Water movement would be initiated by beating that flagella in choanocytes (C) and in the figure moves from left to best (see arrow). Water would get in the choancyte chamber with a prosopyle (p) and also bacteria would certainly be gotten rid of via microvilli (m) bordering the flagellum. Water would then exit through the apopyle (A) (SEM, X1620). Native De Vos L, Rützler K, Boury-Esnault N, Donadey C, and Vacelet J (1991) Atlas that Sponge Morphology. Washington, DC: Smithsonian school Press, through permission indigenous K Rützler.


For plenty of demosponges, choanocytes are clustered together to form chambers in ~ a complex canal mechanism (Figure 3). Because that these species, the cross sectional area the the choanocyte chambers is much greater than any kind of other components of the aquiferous mechanism so slow velocities permit an ext efficient removed of food items. The pumping capabilities of this organisms are rather impressive. Approximates indicate that one kilogram the a typical sponge have the right to pump approximately 50 000 l the water v its human body in a single day. One carnivorous genus, Asbestopluma, lacks one aquiferous canal system and also captures small crustaceans with dedicated spicules raised above the surface ar of the sponge, however this sponge is extremely derived and also atypical for the phylum.

Although they deserve to remove dissolved organic issue from the water column, together a basic rule, sponges room grazers of the ultraplankton (i.e., cells 95% the the ultraplankton that passes with its body. However, extr research is essential to elucidate the dietary requirements of most species. Freshwater sponges possess reliable contractile secret that eliminate water by isotonic water separation and also at the rate of ≈25 μm3 cell−1 min−1, a characteristic that distinguishes freshwater and also marine sponges. Offered the capacity to procedure a huge volume the water and highly efficient feeding behavior, the is straightforward to know why sponges pat such an important role in benthic–pelagic coupling. This characteristic likewise makes sponges a most likely candidate as a biomarker for ecological contaminants.

The manner in which choanocytes are organized is dictated in part by the general structure that the sponge body. There room three basic categories because that the framework of a sponge's aquiferous system and also each defines a steady increase in the intricacy of the level of folding uncovered in the choanoderm. The simplest form, asconoid, is identified by choanocytes that line an inner cavity, or atrium, and can be assumed of together an upside-down thimble v a little aperture. Water beginning the asconoid sponge v ostia top top the exterior of the sponge and also is directed into the atrium whereby bacteria room removed prior to exiting the sponge. These sponges never achieve big sizes, generally growing to much less than one centimeter in height, and are typical of the Calcarea.

Syconoid sponges create an infolding of the choanocytic lining but these C-shaped choanocyte pockets still straight empty into, and also abut, the atrium. The resulting infolding in syconoid sponges increases the surface area committed to pumping family member to the volume the the sponge. With a syconoid design, sponges can develop slightly larger bodies, however this body plan requires the manufacturing of an additional structure, the prosopyle, that connects ostia and incurrent canals come choanocytic chambers.

Leuconoid expansion forms are the most complex and show off the creation of countless choanocytic chambers in ~ the sponge body (Figure 3). V the leuconoid design, incurrent canals and prosopyles lug water to the choanocyte chambers as in the syconoid design, however apopyles are required to affix the chamber to exhalent canals and also ultimately the osculum. The perceived increase in intricacy has been construed to represent an evolutionary succession from the simplest plan (asconoid) come the most facility (leuconoid). However, over there is small support because that this hypothesis and some data indicate that the asconoid and syconoid creates are secondarily derived.


Alexander V. Ereskovsky, in Encyclopedia of Reproduction (Second Edition), 2018

Male Reproduction

Spermatogenesis occurs in the spermatic cysts (spermatocysts) in every sponges, other than Calcarea. Spermatocystes are temporary spherical structures, which build by the revolution of choanocytes of an entire choanocyte room (except that the carnivorous demosponges together they have no aquiferous system and choanocyte chambers). The spermatic cysts are surrounded by the follicle cell deriving through the transformation of pinacocytes (pseudo-epithelial cells) or archaeocytes. In demosponges cabinet junctions in between the follicle cells are simple (apposition) v no detectable membrane specialization. The follicular cell in the spermatic cysts of Homoscleromorpha possess the specialized cell junctions and also basement membrane.

According to species, the synchrony that spermatogenesis wake up at 3 levels: (1) population, as in Neofibularia nolitangere; (2) individual, together in Aplysilla rosea, Myxilla incrustans, Iophon piceum, in which all the choanocytes of the choanocyte chambers at the same time transform right into spermatogonia; (3) spermatic cyst, as in Suberites massa, Spongia officinalis.

Except for species that reproduce all year ring spermatogenesis shows up to occur in a shorter period than oogenesis.


Studies in which complete ingestion (DOC and also POC), growth, and also respiration have been measure up synchronously in situ or under equivalent conditions in sponges space scarce. The carbon line of seven different sponge types for i m sorry at the very least three variables the the equation I = P + R + E were comparatively quantified is summarized in Table 3.3. None of the studies carry out sufficient data to inspect whether fluxes measured with each other really accomplish the balance over a certain time period. Always an unknown flux remained, which was subsequently estimated on communication of the measure up fluxes. Because that the tropical sponges studied by Reiswig (1981), the shortage of carbon ranged indigenous 0.34 μmol C h −1 cm −3 sponge in M. Laxissima come 2.9 in A. Fistularis. In the balance, no account is bring away of exuded material that is no longer available for re-filtration. Therefore, the full amount actually required may also be much greater for every sponges, other than H. Caerulea. because that this sponge, choanocyte shedding (De Goeij et al., 2009) is assumed together a reputable estimate of fragment excretion.


SpongeHost typeI − EpartialPRIshortageErestNGE%R/(I − Epartial)DOC%Source
Tropical varieties (μmol C h− 1 cm− 3)
Tectitethya cryptaLMA0.930.030.460.440.0660.490.0Reiswig (1971b, 1973)
Mycale laxissimaLMA1.450.111.670.340.0661.1618.8Reiswig (1971b, 1973)
Verongula reiswigiHMA0.630.022.481.870.0113.9474.7Reiswig (1971b, 1973)
Aplysina fistularisHMA0.480.163.222.900.0556.7785.9Reiswig (1981)
Halisarca caeruleaL/HMA18.502.002.7013.8a0.43430.1592.4De Goeij et al. (2008a, 2009)
Temperate varieties (μmol C h− 1 g DW− 1)
Haliclona oculataLMA231.507.6095.54128.360.0770.410.0Koopmans et al. (2010)
Halichondria paniceaLMA51.6413.8137.930.100.27270.730.2Thomassen and also Riisgård (1995)

I − Epartial, net ingestion of necessary carbon; P, net growth in biomass; R, respiration (RQ = 1); Erest, detrital product not easily accessible for recirculation; NGE, net growth performance (= P/(P + R)); shortage, imbalances between Ingestion and assimilation; R/(I − Epartial), table of contents estimating the lot of the organic issue ingested which was shed in respiration; DOC%, DOC contribution values to total. Grey cells contain calculation values.

aRate of cabinet shedding.

Comparing net growth rates measured over lengthy time scales through oxygen usage measurements yields NGEs that 0.6–6% (derived indigenous data in Reiswig, 1973; 1974; Table 3.3). The growth performance of H. Oculata based on volume boost in time is 7%, presume an RQ that 1 or 10% for an RQ the 0.75 (Koopmans and Wijffels, 2008; Koopmans et al., 2010). Greater efficiencies the 20–30% have been discovered at growth rates that 1–4% day− 1 in laboratory and also field experiment (Thomassen and Riisgård, 1995). The NGE that H. Caerulea is high (43%) when compared to other sponges. It is tempting come assume that the high NGE in H. Caerulea is due to the efficient and also rapid growth rate that choanocytes. De Goeij et al. (2009) report high choanocyte proliferation prices coupled to shedding that old cell in H. Caerulea. Rapid cell renewal may be a maintenance strategy similar to the in greater animals. Therefore, cell proliferation rate is noted under excretion in Table 3.3, implementing the still undemonstrated presumption that proliferation rate have to equal cell shedding rate. Whenever the cell proliferation above shedding, sponge net growth may take place. Whenever sponges invest energy in cabinet renewal, their net expansion may it is in low. This process probably takes the bulk of the energy yielded to H. Caerulea, not leaving much energy for net expansion in dimension (De Goeij et al., 2008a). Median production the H. Caerulea calculated at 2 μmol C cm− 3 sponge h− 1 ~ above the C balance equation is more than likely an overestimate. Further research is necessary to establish the function of choanocyte rebirth in sponge metabolism and growth process.



Figure 1.3. Compare ultrastructural schematics that a choanoflagellate and a sponge choanocyte, modified indigenous Maldonado, M., 2004. Choanoflagellates, choanocytes, and animal multicellularity. Invertebr. Biol. 123, 1–22, following (Woollacott and Pinto, 1995) because that the microtubule cytoskeleton and (Karpov and also Coupe, 1998) because that the actin cytoskeleton. mt, mitochondria; fl, flagellum; fv, food vacuole.

From Brunet, T., King, N., 2017. The beginning of pet multicellularity and cell differentiation. Dev. Cabinet 43, 124–140.

Choanoflagellates room not derived from metazoans; as a separate lineage, lock evolved before the appearance of metazoans (King et al., 2008).


Choanoflagellates kind colonies of numerous cells. The breakthrough of nests in this group results from reproduction of comparable cells (Figs. 1.4 and 1.5) fairly than native aggregation of comparable cells together demonstrated by the experimental evidence that the usage of the cell cycle inhibitor aphidicolin stays clear of formation of choanocyte colonies. There is no evidence that choanoflagellates may form colonies via aggregation of comparable cells (Fairclough et al., 2010).



Figure 1.4. Salpingoeca rosetta can transition through in ~ least five morphologically and also behaviorally differentiated cell varieties (Fairclough et al., 2013). Solitary “thecate” cell attached to a substrate (Th) can produce solitary swim (Sw) cells or solitary rapid swimming (FS) cells, either through cell department or theca abandonment. Solitary swim cells have the right to divide completely to develop solitary daughter cell or continue to be attached after undergoing incomplete cytokinesis to produce either chain colonies (CC) or rosette nests (RC) in the visibility of the bacter Algoriphagus machipongonensis (asterisk). Fil, Filasterea; Cho, Choanoflagellates.

From Fairclough, S.R., Chen, Z., Kramer, E., Zeng, Q., Young, S., Robertson, H.M., Begovic, E., et al., 2013. Premetazoan genome evolution and the regulation of cabinet differentiation in the choanoflagellate Salpingoeca rosetta. Genome Biol. 14 (2013), R15.

Figure 1.5. Calcareous sponge embryos and also Volvocale embryos.

(A) Morphogenesis throughout rosette formation in the choanoflagellate Salpingoeca rosetta, adhering to Fairclough et al. (2010). (B) early embryonic advance of the calcareous sponge Sycon ciliatum, consisting of amphiblastula inversion (from Franzen, W., 1988. Oogenesis and larval breakthrough of Scypha ciliata (Porifera, Calcarea). Zoomorphology. 107, 349–357).

From Brunet, T., King, N., 2017. The origin of animal multicellularity and also cell differentiation. Dev. Cabinet 43, 124–140.

A properties of all multicellular organisms, beginning from the simplest ones, is the presence of epithelium, a one-cell thick tissue that separates and protects underlying tissues from the harmful environmental agents. It additionally lines the inner caries and free surfaces that tubular organs. Development of epithelia required appearance of a stable device of cabinet adhesion that appears to have independently progressed in several teams of life forms and also connect epithelial cells with each other and also with the intercellular matrix. The last common ancestor the metazoans is inferred to have been in possession of assorted intercell adhesion junctions (Abedin and King, 2010) (Fig. 1.6).



Figure 1.6. Evolutionary background of epithelial cell junctions.

The four main functions of pet epithelia room adhesion, barrier, signaling, and anchoring. Facets of adherens, septate, pannexin-based gap, and anchoring junctions (hemidesmosomes , focal distance adhesion , and also basal lamina) to be likely current in the last usual ancestor the animals, when desmosomes, tight, and also connexin-based space junctions emerged later in pet evolution. Because that a series of ancestors representing step in animal evolution, the visibility (filled box) or lack (open box) of evidence for (1) genes diagnostic of every junction form (“Gene”), (2) junction morphology detected by electron microscopy (“Morph”), and also (3) experimental support (e.g., steady cell adhesion, barrier function, or protein localization; “Expt”) in extant lineages is shown (Tyler, 2003; Boury-Esnault et al., 2003; Sakarya et al., 2007; Abedin and also King, 2008; Spiegel and Peles, 2002; Bing-Yu et al., 1997; Banerjee et al., 2006; Nichols et al., 2006; Ledger, 1975; Leys et al., 2009; Shestopalov and Panchin, 2008; Chapman et al., 2010; Litvin et al., 2006; Boute et al., 1996; Ereskovsky et al., 2009; Aouacheria et al., 2006; Muller and also Muller, 2003; Brower et al., 1997; Magie and Martindale, 2008; Sabella et al., 2007).

From Abedin, M., King, N., 2010. Diverse evolutionary paths to cell adhesion. Trends in cell biology 20, 734–742.

Unlike choanoflagellates, whereby every cell can feed on their own, most of choanocytes in sponges lost capacity to feed (Cavalier-Smith, 2017). In Cavalier-Smith's view, the choanocyte swim ball swarm could evolve via somatic cell differentiation into a basal pinacocyte that secretes collagen and also mucopolysaccharide-rich extracellular matrix and form a mesohyl layer through spicules and also rare cells in between the external pinacocytes and also internal choanocytes. This brand-new layer can serve as mesohyl skeleton in between two layers and support a bigger presponge structure that might anchor itself on a rock. The same genetic tool provided for differentiating pinacocytes might be offered for gamete (sperm cells and larger oocytes) differentiation (Cavalier-Smith, 2017).

It is not resolved yet, i beg your pardon of the nonbilaterian phyla is the sister group of the remainder of metazoans yet here will certainly be preferred to consider placozoans, in heat with various other authors (Srivastava et al., 2008; Schierwater et al., 2009; Schleicherová et al., 2017; Eitel et al., 2018).


Ilya Borisenko, ... Alexander V. Ereskovsky, in developments in Protein Chemistry and also Structural Biology, 2019

2 Embryonic development

Three model species of sponges were thought about in the review: Halisarca dujardini, Sycon ciliatum and also Amphimedon queenslandica. Developmental mode is remarkably different in each of these species.

H. Dujardini is a viviparous species. Embryos build inside momentary embryonic capsules developed from dedifferentiated choanocytes (Korotkova & Apalkova, 1975) (Fig. 1B and C). Cleavage is complete, equal and also polyaxial (Fig. 1C(b–c)) (Ereskovsky, 2010). A single-layered coeloblastula with a small cavity is formed, and outer cells become columnar in shape and also ciliated.

The larvae start to move a few days before leaving the parent sponge. The wall surfaces of the embryonic capsule soon fuse through those the the aquiferous canal, and larvae escape v the osculum. Released larvae continue to swim openly by moving forward and rotating clockwise around the anterio-posterior axis. The larva the H. Dujardini is rounded and measures about 120–130 μm in diameter. That is evenly ciliated, other than at the posterior pole, i m sorry is ciliated much less densely (Fig. 3B). Its exterior cells are connected with belt desmosome-like junctions (zonula adhaerens) in their apical parts (Gonobobleva, 2007; Gonobobleva & Ereskovsky, 2004a, 2004b).

The larvae that S. Ciliatum develop in the mesohyl between the choanocyte and the pinacocyte great (Fig. 1C(e–h); Franzen, 1988; Leys & Eerkes-Medrano, 2005). Beforehand cleavage is equal and also highly stereotypic. The very first four blastomeres kind a rhomboid i ordered it in the aircraft defined through the choanocyte and also the pinacocyte layers. Due to the fact that the 3rd cleavage the mitotic spindle transforms to divide daughter cell laterally and also in the direction of choanoderm (Fig. 1C(f–g)). This outcomes in the development of a cup-shaped stomoblastula embryo through an opened directed come the choanoderm. Through the end of cleavage and differentiation, the embryo is written of three cell types: large, granular, non-ciliated macromeres nearby to the choanocytes; smaller and more numerous micromeres, which have actually cilia pointing right into the embryonic cavity; and also four cruciform cells. The embryo then undergoes excurvation (inversion) v stomoblastula opening (Fig. 1C(h)). Together a an outcome of this process, throughout which the embryo is turned inside out, the cilia are positioned ~ above the external larval surface and the larva is relocated to the choanocyte chamber. Throughout metamorphosis, the larva handle on the anterior pole; in ~ minutes the ciliated cells of the anterior fifty percent undergo epithelial–mesenchymal shift (EMT) and kind the inner cabinet mass. In contrast, the macromeres keep their epithelial organization, totally enclose the micromeres, and also become the pinacocytes the the creating juvenile.

The embryos that A. Queenslandica likewise develop in brooding chambers in follicular capsules (Fig. 1C(j); Adamska et al., 2007; Leys & Degnan, 2002). In ~ the early on stages the cleavage, chaotically i ordered it micromeres and also macromeres of different size are created (Fig. 1C(k)). Through the finish of cleavage, the morula (solid blastula) currently contains micro- and macromeres, amoeboid cells, sclerocytes, ciliated cells and pigment cell (Fig. 1C(l)). Every these cells are mixed until positional signals guide them to their definitive location in the larvae. Cleavage is adhered to by the development of cabinet layers as result of differential cell motions in the embryo. The main results that these activities are the formation of an outer ciliated cell layer by ciliated cells and an buildup of colors cells and spicules, referred to as the colours spot, at the posterior pole of the embryo (Fig. 1C(m)). The outer ciliated cells will administer locomotion the the larva, when the colors spot will certainly transform into a colors ring, a circular setup of pigmented cells through a photosensory function. Through this stage the embryo elongates follow me the anterio-posterior axis, the colours ring marking the posterior pole. Countless of the developmental genes expressed in the embryo are closely related to the colors ring.


Basal pet taxa such together sponges present great system to investigate an easy regulation the symbiont localization and also transmission, together they lack true tissues, and simply consists multiple cell varieties (Cavalier-Smith, 2017). As shown in Fig. 3A, sponge body consist the choanocyte (feeding cell) chambers suspended in mesohyl, lined with a class of pinacocytes to serve as an exterior barrier. The mesohyl makes up many of the sponge through volume, and also is one extracellular procession consisting of connective tissue, sponge cells, and bacterial symbionts (Hentschel, Piel, Degnan, & Taylor, 2012). Oocytes are situated in the mesohyl (Usher, Kuo, Fromont, & Sutton, 2001), and in cases of interior fertilization and viviparity, embryos are likewise brooded in the mesohyl, occasionally in dedicated chambers (Kaye, 1991; Schmitt, Weisz, Lindquist, & Hentschel, 2007; Sharp, Eam, Faulkner, & Haygood, 2007; Vacelet, Fiala-Médioni, Fisher, & Boury-Esnault, 1996).


Fig. 3. Instances of soma-to-germline upright transmission techniques that usage extracellular routes. (A) Illustration that a demosponge human body plan and also route the symbiont deliver to oocytes/embryos native extracellular populations in the mesohyl. (B) In whiteflies, bacteriocytes containing bacter symbionts migrate from the gut bacteriome to the ovary and become linked with the perivitelline room between the oocyte plasma membrane and also the follicle cells prior to vitelline envelope formation (Szklarzewicz & Moskal, 2001). This outcomes in the bacteriocyte being located under the shell, yet outside the oocyte, at the posterior of mature egg (Costa, Toscano, & Henneberry, 1996), together illustrated. (C) The two gammaproteobacterial symbionts of range insects move extracellularly from dissociated bacteriocytes in the gut bacteriome to the ovary, whereby they cross between or through follicle cells to become connected with the perivitelline an are between oocyte and also follicle cell plasma membranes. As illustrated, this arsenal of extracellular symbionts i do not care enclosed in the perivitelline room in the maturation oocyte (Michalik et al., 2018). (D) Similarly, the vertically sent symbionts the deep-sea chemosynthetic clams localize come the perivitelline space of transfer spawned eggs (Ikuta et al., 2016), as illustrated.


During sexual reproduction in sponges, 4 main tactics for vertical symbiont transmission have actually been observed (Ereskovsky, Gonobobleva, & Vishnyakov, 2005): (1) symbionts room phagocytosed right into oocytes from their extracellular locations in the adult mesohyl (Maldonado, 2007), (2) bacteriocytes transfer symbionts come brooded embryos (Maldonado, 2007; Schmitt, Angermeier, Schiller, Lindquist, & Hentschel, 2008), (3) symbionts space transferred extracellularly via rubber (Kaye, 1991), and also (4) symbionts space sequestered in the extracellular room between the egg and also the follicle cells during oogenesis, with the symbionts start the embryo during cleavage (Ereskovsky & Bouryesnault, 2002). Even in the simplest of multicellular body plans, there room a vast diversity of mechanisms and also strategies because that accomplishing proper localization fads in the soma and also germline. Sponges are likewise capable the asexual reproduction through fragmentation (Hentschel et al., 2002), additional increasing the strategies obtainable to them because that symbiont transmission.


P. Cárdenas, ... N. Boury-Esnault, in breakthroughs in maritime Biology, 2012

4.1.3 Cytology and choanosome anatomy

The usage of cytological characters in sponge taxonomy has actually been neglected by most of the sponge systematicians. They have never been introduced systematically in sponge descriptions since cytological approaches are considered daunting to apply in routine analysis and due to the fact that histological slides and also electron micrographs could be difficult to analyze (Erpenbeck, 2004). However the use of cytological features of the aquiferous mechanism for sponge taxonomy to be proposed by number of authors who concentrated on the different facets of choanocytes chambers, choanocytes and apopylar cells (Minchin, 1896; Bidder, 1898; Dendy and Row, 1913; Lévi, 1979; Bergquist, 1980, 1995; Vacelet et al., 1989; Boury-Esnault et al., 1990; De Vos et al., 1990; Bergquist et al., 1998; Bergquist and Cook, 2002a).

Cytological studies have actually been an especially developed because that taxonomy of varieties without mineral skeleton or there is no skeleton at all, and the usefulness of these data has been hence demonstrated (Muricy, 1999; Ereskovsky et al., 2011; Pérez et al., 2011). These characters appeared particularly useful to define demosponges there is no skeleton such as Halisarca (Vacelet and also Donadey, 1987; Ereskovsky, 2007; Ereskovsky et al., 2011), ThymosiopsisVacelet and also Pérez, 1998 and also MyceliospongiaVacelet and also Pérez, 1998 (Vacelet et al., 2000), and Homoscleromorphap (see ar 7).


The advance of cytological and also anatomical studies seems specifically important in spiculate assignment or family members for which we are confronted with severe taxonomic problems such as the Haplosclerida whereby a human body of expertise remains unused in the recent phylogenetic theory (Table 2.5). The use of the choanosome anatomy in taxonomy because that Haplosclerida has been already suggested (Langenbruch, 1988, 1991; Langenbruch and also Scalera-Liaci, 1990; Boury-Esnault, 2006) (Fig. 2.15A–F). Choanocyte chambers straight “hanging” in the inhalant an are and spanned by a pinacocyte layer into which the prosopyles open have been explained in several types belonging come the households Chalinidae Gray, 1867, Callyspongiidae de Laubenfels, 1936 and Petrosiidae van Soest, 1980 (Fig. 2.13 and Table 2.5). This form of choanocyte chambers is absent in Spongillidae Gray, 1867 (Haplosclerida Topsent, 1928) (Langenbruch and also Weissenfels, 1987), in Amphimedon compressa Duchassaing and Michelotti, 1864, Haliclona sarai Pulitzer-Finali, 1969 and Dendroxea lenis Topsent, 1892 (Langenbruch, 1988, p. 20).


List of speciesCCReferences
Haplosclerina Topsent, 1928
Chalinidae Gray, 1867Chalinula limbataMontagu, 1818HLangenbruch (1991) (as H. limbata) and also Langenbruch and Scalera-Liaci (1990)
Chalinula saudiensisVacelet, Al Sofyani, Al Lihaibi and also Kornprobst, 2001HVacelet et al. (2001; Fig. 2.12A)
Haliclona (Reniera) cinerea Grant, 1826HLangenbruch and also Scalera-Liaci (1986, 1990) and also Langenbruch (1991) (as H. elegans)
Haliclona (Reniera) mediterranea Griessinger, 1971HLangenbruch (1988, 1991), De Vos et al. (1991) and Boury-Esnault (2006)
Haliclona (Rhizoniera) roseaBowerbank, 1866HLangenbruch (1991) and Langenbruch and Scalera-Liaci (1990)
Haliclona (R.) indistincta Bowerbank, 1886ELangenbruch (1991) and Langenbruch and Scalera-Liaci (1990)
Haliclona (R.) sarai Pulitzer-Finali, 1969ELangenbruch (1988, 1991)
Haliclona (Haliclona) simulansJohnston, 1842HLangenbruch (1991) (as A. simulans) and also Langenbruch and Scalera-Liaci (1990)
Haliclona (Haliclona) oculataPallas, 1766HLangenbruch (1991), and also Langenbruch and Scalera-Liaci (1990)
Haliclona (Halichoclona) fulva Topsent, 1893HLangenbruch (1988, 1991) (as R. Fulva)
Haliclona (Halichoclona) fistulosaBowerbank, 1866HLangenbruch (1991) and also Langenbruch and also Scalera-Liaci (1990)
Haliclona (Soestella) mucosa Griessinger, 1971HLangenbruch (1988, 1991) (as R. mucosa) (Fig. 2.12B)
Haliclona (Gellius) rava Stephens, 1912HLangenbruch (1991) and also Langenbruch and also Scalera-Liaci (1990)
Dendroxea lenis Topsent, 1892ELangenbruch (1988, 1991; Fig. 2.12D)
Callyspongiidae de Laubenfels, 1936Callyspongia (Cladochalina) diffusa Ridley, 1884HJohnston and Hildemann (1982) and also Smith and also Hildemann (1986, 1990)
Callyspongia (C.) vaginalis Lamarck, 1814HDe Vos et al. (1991; Fig. 2.12C)
Niphatidae van Soest, 1980Niphates digitalis Lamarck, 1814HLangenbruch (1988, 1991)
Amphimedon compressa Duchassaing and Michelotti, 1864ELangenbruch (1988, 1991; Fig. 2.12E)
Petrosina Boury-Esnault and van Beveren, 1982
Petrosiidae van Soest, 1980Petrosia (Petrosia) ficiformisPoiret, 1789HLangenbruch (1983, 1991), Langenbruch et al. (1985) and Langenbruch and Scalera-Liaci (1990)
Calcifibrospongiidae Hartman, 1979Calcifibrospongia actinostromarioides Hartman, 1979HHartman and Willenz (1990)
SpongillinaManconi and Pronzato, 2002
Spongillidae Gray, 1867Ephydatia fluviatilisLinnaeus, 1759ELangenbruch and also Weissenfels (1987), Langenbruch (1991) and also De Vos et al. (1991; Fig. 2.12F)
Ephydatia muelleri Lieberkühn, 1856ELangenbruch (1991)
Eunapius fragilis Leidy, 1851ELangenbruch (1991)
Spongilla lacustrisLinnaeus, 1759ELangenbruch and Weissenfels (1987) and Langenbruch (1991)

Classification adheres to the world Porifera Database. Type species are in bold. In the tower choanocyte chambers, H way hanging choanocyte chamber within incurrent canals, E means choanocyte chambers embedded in the mesohyl.


Figure 2.15. (A–C) SEM micrograph that hanging choanocyte chambers within an incurrent canal. (D–F) SEM micrograph the choanocyte chambers installed in the mesohyl. (A) Chalinula saudiensis; range bar = 52 μm. (B) Haliclona mucosa; range bar = 17 μm. (C) Callyspongia vaginalis; 5.4 μm. (D) Dendroxea lenis; range bar = 9.6 μm. (E) Amphimedon compressa; 8.4 μm. (F) Ephydatia fluviatilis; scale bar = 19 μm. A (photo courtesy J. Vacelet); B–F

(photos courtesy L. De Vos; http://www.ulb.ac.be/sciences/biodic/homepage.html).

Among the various categories the cells current in the mesohyl (Simpson, 1984; Boury-Esnault, 2006), some are current in all varieties and because of this do no bring any phylogenetic signal. Other cells such together the cells with inclusions (spherulous cells, granular cells, glycocytes, etc.) can be helpful for taxonomy (Topsent, 1900). Such cells contain huge spherical or ovoid inclusions that occupy the main part of the cytoplasmic volume. Lock are connected in the elimination of metabolic wastes (Vacelet, 1967) and in the warehouse of bioactive molecules (Thompson et al., 1983). Depending on the sponge species, the spherules space either homogeneous or heterogeneous, often microgranular in size and often have a taxonomic value. For example, Verongida species have a very characteristic spherulous cell kind (Vacelet, 1967). This form of cell has actually been found also in the aspiculate genus Hexadella Topsent, 1905, i beg your pardon led Bergquist and also Cook (2002a) come reassign Hexadella varieties to the family Ianthellidae Hyatt, 1875 (Verongida Bergquist, 1978; Fig. 2.16). This result was evidenced later by molecular data (Borchiellini et al., 2004a).


These personalities were additionally used to discriminate between spiculate varieties of PolymastiaBowerbank, 1864 (Boury-Esnault et al., 1994) and SpirastrellaSchmidt, 1868 (Boury-Esnault et al., 1999b). Muricy (1999) supplied morphological, anatomical, skeletal and also cytological data to adjust in a cladistic evaluation of 10 types of Homoscleromorphap, and he verified that the topology of the tree acquired from the linked data sets offered a an excellent resolution.

Among the ingredient of the mesohyl, plenty of sponge varieties display abundant communities of prokaryotes or/and eukaryotic microsymbionts. They are fairly diverse and can be certain to various sponge ranks, native order come species. These specific symbionts have the right to be sent vertically indigenous one generation to another and may be even diagnostic to discriminate close species (Vacelet et al., 1994; Ereskovsky et al., 2005; Enticknap et al., 2006; Vishnyakov and Ereskovsky, 2009; Schmitt et al., 2012; Thacker and also Freeman, 2012).

Fundamental cytological characters of such importance as the synapomorphy the the Poriferap, the presence of choanocytes and also of one aquiferous system, can also be secondarily lost: it has actually been fully lost in many carnivorous sponges that the household Cladorhizidae Dendy, 1922 (Vacelet and Boury-Esnault, 1995; Vacelet, 1999a, 2007).


The advancement of Leucosolenia variabilis was explained by Okada (1968). This description can likewise be used to L. Complicata (Fig. 4.15A), Grantia compressa, Sycon raphanus, and Scypha ciliata (Fell, 1997). Spermatogenic cells of L. Complicata (Ereskovsky, 2010) were uncovered to it is in diffusively dispersed in the mesohyl. Solitary spermatocytes or tiny bunches were not surrounded by any dedicated cells, did not form special spermatocyte, choose in various other sponges, and remained free under the choanoderm. Mature spermatozoa the L. Complicata look choose orbicular cells. Flagellum and also acrosome are absent and the cell nucleus is formed by incomplete condensed chromatin. The latter is surrounding by a slim layer that cytoplasm (Fig. 4.15C). ~ above the other hand, oogenesis in calcaronea, in general, is uniform and also follows the normal pattern. However, the oocytes lack a vitelline envelope and also possess amoeboid motility. In ~ first, the oocyte take away its place beneath the choanoderm layer, and then it migrates through amoeboid motility through the mesohyl to the peripheral or basal parts of the sponge. There, it forms long pseudopodia and also shows phagocytic task to rise to its specific size (Fig. 4.15B). In L. Complicata and during vitellogenesis, a complex of accessory cell is formed over each oocyte, acquired from choanocytes that shed their flagellum and also collar. The variety of accessory cells does no exceed 6 because that each that Grantia or Sycon, yet may reach 30–40 because that each of L. Complicata. Ereskovsky (2010) reported that a unique condition is it was observed in Petrobiona massiliana (the only Cacaronea v a enormous calcareous skeleton, in enhancement to the spicules). In this sponge, all the choanocytes in the choanocyte chamber, nearby to a vitellogenic oocyte transform into cells the the feeding complex (Fig. 4.15E).


Fig. 4.15. (A) Leucosolenia complicata (Montagu 1818); (B–D) that embryonic stages (B) oogenesis in Calcaronea sponge, (a) oocyte in ~ initial stage, (b and c) oocyte in ~ primary expansion (cytoplasmic growth), (d) oocyte at vitellogenesis, ac = accessory cells, ch = choanocyte, mc = mesohyl cells, oo = oocyte, pc = pinacocyte, tr = trophocyte; (C) Spermatozoon the L. Complicata, m = mitochondria, n = nucleus; (D) illustrations showing procedure of fertilization in L. Complicata, (a) development of carrier cell, (b) penetration the the sperm nucleus from the carrier cell right into egg cytoplasm, c = cytoplasm that the oocyte, cc = carrier cell, n = nucleus the oocyte, nc = nurse cell, pb = peptide body, sn = nucleus that spermium, spc = spermiocyst. (E) Oogenesis and also vitellogenesis in Petrobiona massiliana, (a) oocyte (oo) situated next come choanocyte room II (C II), (b) oocyte phagocytoses nurse cell (nc); (c) full grown oocyte through degenerated nurse cells, CCI = choanocyte chamber I, m = mesohyl.

(From Ereskovsky (2010).)

The cleavage of the fertilized egg (zygote) that sponges is peculiar, together the normal continuous cleavage is somewhat modified. In Leucosolenia types (Fig. 4.16), during the an initial cleavage, the zygote divides follow me a meridional aircraft into two equal blastomeres. The second cleavage is along a meridional plane, perpendicular come the first, giving rise to four equal blastomeres. Each of this blastomeres modifies and develops a pointed end while the other finish becomes vast (the pointed end will give rise come the ciliated cell of the future larva, and also the vast ends to the granular cells). The third cleavage in sponges differs from the normal manner. It occurs in 2 vertical planes, intermediate in position in between the an initial two airplane of cleavage. The product is eight same blastomeres, in one tier, each of i m sorry is choose a pyramid. Every one of them are arranged regarding give the whole growing embryo the kind of a flat cone. The apex that the cone is formed by the pointed ends and the apices the the embryo execute not meet, producing a main space. This an are is an yes, really perforation through the axis the the cultivation embryo, open up at both ends. The fourth cleavage is latitudinal (equatorial); it divides the embryo, offering rise come the 16-cell stage. This stage consists of two layers, eight upper blastomeres (apices) and eight lower, vast ones. Climate the cultivation embryo assumes the form of a biconvex lens, in the axis of i m sorry is the central perforation (future blastocoel).


Fig. 4.16. (A) Schematic illustrations showing embryological stages of Calcaronea (mostly the Leucosolenia), (b–e) and (e′) are original, rather are collected from miscellaneous sources, (a) zygote, (b–e) cleavage, (c′–e′) surface views because that the top lateral views, (f) blastula, (g) stomoblastula; (h–k) reverse of the blastula; (l) newly hatched larva the Leucosolenia (or pseudo-gastrula); (m) totally formed amphiblastula larva; (n and o) negotiation of larva, arrows suggest direction the movement, (o) Olynthus stage; (B) Cleavage in the (asconoid) calcaronean sponge Leucosolenia complicata: (a) Anaphase the the an initial cleavage division; (b) two-cell stage; (c) 2nd cleavage division; (d) four-cell stage; (e) third cleavage division; (f) sixteen-cell stage. Scale bars: 2 μm.

(After Anakina (1997), from Leys and Ereskovsky (2006).)

Probably, this 16-cell phase finishes cleavage that the zygote. The farming embryo has eight basal granulated cells and eight smaller sized upper cells, the main cavity i do not care large, when its terminal apertures narrow and also finally, in ~ the end, they room closed. So, the axial perforation repurchase the personality of a closed blastocoele cavity. The growing embryo itself becomes a blastosphere. That granulated eight cell abutting the wall of the radial canal, space the prospective granular cells, and also the remainder are the prospective choanocytes (Fig. 4.17g).

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The smaller cells division rapidly and each acquires an interior flagella, when the granular cells execute not division for sometime, and kind a distinctive group of eight large, rounded cell termed macromeres. In the center of this team an opening shows up that functions as a mouth and ingests the surrounding choanocytes of the mother (Fig. 4.16A (g)). This is the stomoblastula phase as designated by Duboscq and also Tuzet (1937) (cited in Okada, 1968). The granulated cells climate multiply, the mouth closes and also the embryo is known as a blastula at this stage, with internally command flagellae.