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Clathrina spp.

Ronan Hill 2021


Sponges (phylum Porifera) are marine invertebrates found globally in a variety of marine and freshwater ecosystems such as coral reefs, shallow waters, deep ocean benthos and intertidal habitats (Hickman et al. 2017; Rupert et al. 2004). They are critical to ecosystems in water quality control, filtration, erosion and re-circulating nutrients in marine ecosystems. Sponges all utilise the same feeding techniques but vary in complexity depending on the body plan of the sponge species. The body structures being Asconoid, Synconoid and Leuconoid in order of complexity. Diversity among sponge species is extremely varied, with body plans not following any given symmetry, colour, size or level of complexity as it varies between genera. Even if sponges share the same level of feeding complexity, they are able to differ in shape and morphological structure. All sponges are sessile organisms that utilise a bi-phasic life cycle for dispersal of larvae in the pelagic water column, with species being able to asexually reproduce as well (Hickman et al. 2017; Rupert et al. 2004).

The Clathrina spp. found is a from the family Clathrinidae and is a type of calcareous sponge in the phylum of Porifera. Clathrina sponges are composed of numerous anatomised tubes and have colours ranging from pale white, yellow, red or brown, depending on the species phylogenetic background and spicule composition, which the Clathrina spp. shown follows in structure and colour. Clathrina sponges are characterised for their simplicity in structural organisation with their Asconoid aquiferous system (Klautau & Valentine 2008). The Clathrina species found were pale white in colour and is unique in its structure and was not able to be identified to a species level as the specimens were lost during the production of this webpage.

Figure 1

Physical Description

Size and Colouration

The Clathrina found is pale white in colouration, varying from some other Clathrina sponges that can be yellow, red or brown in their colouration (Rossi et al. 2011). It draws attention through its defined refractions of light from the calcareous skeleton, with spicules contrasted to its pale white colour (Fig. 1). It is a small species typical to the genus of Clathrina, only observed to grow anywhere between 20mm-1cm in size (Klautau & Valentine 2008). The colour is uniformly white throughout the whole structure. Larger samples then this were not obtained from ARMS plates, with no variations in colour from pale white observed. It is therefore unknown whether the sponge at larger sizes differs in colour, however that is unlikely due to the need to develop differing spicule types. Smaller samples observed were assumed to be juvenile adult forms due to the relative age of the settlement plates (4-6 months).  

External Morphology

As with other Clathrina spp. the sponge found displayed an anatomised tubular structure that were loosely aggregated, however the structure reforms joining at the apex of the sponge in order to form a singular central osculum (Fig. 2 & Fig. 3). The sponge is stemmed with a peduncle that is attached to the hard benthic substrate by the peduncle (Imeśek et al. 2014). The sponge was observed to grow on barnacle shells, bi-valve shells and other hard substrates, with tubules originating from the stem of the sponge (Fig. 1 & 3). The external tubules of the sponge range from 0.5 to 5mm in diameter and are pored for the intake of water that feed it towards the central osculum of the sponge (Fig. 4). Clathrina sponges possess two different types of osculum, one which receives water from a single tube and the other which is connected to multiple tubes of the sponge which is the case in this Clathrina spp. (Klautau & Valentine 2008). The Clathrina found is a more advanced structure of Clathrina, displaying fewer anatomised tubes with a defined osculum which differs from the simpler Clathrina species (Fig. 5) that display many osculum and loosely aggregated tubes (Klautau & Valentine 2008). Sponge skeleton consists of spicules and is plated with calcium carbonate (Fig. 2, Fig. 4). The osculum displays a crown of spikes around the hole (Fig. 6).  

Figure 2
Figure 3
Figure 4
Figure 5
Figure 6


Feeding and Defence

            Sponges are suspension filtration feeders that intake water through designated pores around their body (oscula), passing the water through flagellated canals in the body by generating unidirectional currents with choanocytes that also strip nutrients from the water, and then expelling waste and filtered water through an osculum at high pressures away from the sponge (Voigt et al. 2012). Food consists of organic food particles that float in the benthic water column and other useful nutrients that can be extracted from the filtered water (Hickman et al. 2017; Bond 2013). The Clathrina found is Asconoid in structure and utilises the same mechanisms but possess a few differences in its feeding anatomy. Clathrina are characterised by having a continuous choanoderm that lines all the internal cavities of the sponge used for feeding as they create the unidirectional current towards the osculum to expel waste away from the sponge (Klautau & Valentine 2008). Clathrina species have also been observed to use contractions in feeding. When the sponge contracts it serves multiple purposes such as the expelling the built-up detritus, removal of pest invertebrates and used in predation of the pest invertebrates (Bond 2013). This feeding mechanism can be due to a need to supplement the less effective suspension feeding mechanism (Leys & Hills 2012).

            Clathrina sponges utilise highly plastic morphology in order to defend against intraspecific competition and environmental change in their surrounding environment (Bond 2013). The high plasticity of Clathrina sponges allows them to structurally rearrange their body plan, such as contractions and dilations of body segments, including the tubular arrangements, where the sponge is able to modify its choanocytes and reposition porocytes (Bond 2013). This is done in order to contract and expand in size to better function under the effects of competition, and this is due to calcareous sponges being known as weak space competitors (Bond 2013). The key predators to Clathrina spp. are nudibranchs, echinoderms, fish species and other small invertebrates, which can break down the skeletal structure of calcareous sponges (Wulff 2020). Little is known about the specific defence mechanisms of this Clathrina species to avoid predation.

            Sponges can also induce anti-bacterial defences against disease, however the exact processes behind sponge microbial defence have not been investigated, especially in Clathrina species (Webster 2007). The applied chemotaxic procedures of this sponge regarding its competitive interactions were not observed, however trends of species avoidance were shown in its settlement locations.


           The majority of locomotion and dispersal in sponges is found in the lecithotrophic larvae, with little locomotion in the developed sessile sponge stage. Sponge larvae utilise lines of cilia that act independently from each other to move through the water column. Since the sponge lacks a nervous system, a combination of chemical, light and position is used to direct the sponge larvae to an ideal settlement location. Sponge larvae are weak swimmers and typically utilise ciliated movement in order to position themselves, instead utilising currents to act as passive particles moving along horizontal scales (Mariani et al. 2006).

            Post settlement locomotion has been observed in Clathrina sponges and can explain the variabilities in tubular size of the observed Clathrina species. Clathrina species can move through a combination of contraction, dilations and structural rearrangements that allow for the sponge to crawl (Bond 2013). It is suggested that calcareous sponges utilise their spicules as cleats and anchors in order to propel themselves for full body movement (Bond 2013). This done through spicule rearrangements in the sponge and is distinct from other forms of sponge locomotion, such as those seen in Demospongiae (Bond 2013). Another form of sponge locomotion that is utilised is contractile waves and has been directly observed in Clathrina spp. (Bond 2013). The contractions of the sponge propagate through the tube mass of the sponge and is done in order to alter the internal flow of the sponge (Bond 2013). The contractions have also been associated with outward growth and movement of the sponge (Bond 2013).

Life History and Behaviour


            Settlement behaviour of the Clathrina species suggested a preference to settling on the underside of a hard benthic substrate, as observed by the sponge’s settlement locations in the lab (ARMS plate surface, barnacle surface or bi-valve shell). Its settlement locations suggest that the sponge uses phototaxis in order to avoid heavy light and lie on the underside of settlement areas. It did not display strong competitive behaviour, such as overgrowth tendencies and competition with nearby organisms as it was found isolated from other benthic organisms (Demospongiae, ascidians and hydroids). This is supported by the fact that little to interspecific competition has been observed in Clathrina species (Gaino et al. 1991). This suggests that the sponge is sensitive to chemical influence in its larval stage and avoids competition which is supported in its highly plastic nature to avoid and endure competition (Bond 2013; Marini et al. 2006; Gaino et al. 1991).

            Feeding behaviour is that of a typical Asconoid sponge with few variations that the Clathrina is able to perform. The Clathrina is able to perform antipredator behaviours such as if stimulated by parasitic invertebrates the Clathrina is able to perform a contractile wave in order to dislodge parasites and potentially consume it (Bond 2013). The highly plastic nature of Clathrina also allows it to react to potential intraspecific competition, with movement utilising its contractions and structural rearrangements depending on the situation (Bond 2013; Gaino et al. 1991).

Life History and Settlement

            The life history of the Clathrina sponge matches that of other sponges. The Clathrina species goes through a bi-phasal pelago-benthic life cycle with a dispersal phase utilising lecithotrophic larvae for their pelagic dispersal phase and then settling into the recognised sponge. It can then be assumed that the unknown speciation of this Clathrina sponge would follow the same life cycle progression as other similar sponge species. The life cycle then follows as 1) a zygotic stage inside the parental sponge 2) the lecithotrophic (Parenchymula) larvae phase which characterises the dispersal of sponge species and settlement and then 3) the adult sponge phase. Calcispongiae undergo a different developmental pattern in the formulation of a stomoblastula that is inverted to turn the choanoflagellate cells outwards (Hickman et al. 2017). Clathrina species also develop a unique canal design that is completely different from Demospongiae, which is continuously lined with choanoflagellates that maximises their feeding ability (Borchiellini et al. 2001, Klautau & Valentine 2008).

Class Calcarea are always viviparous in reproduction (Klautau & Valentine 2008). Clathrina sponges are also known to incubate coeloblastula larvae (Hickman et al. 2017). The exact reproductive nature of the sponge seen in figure 1 are unknown due to unknown speciation, however an example of sponge larvae and sponge vivparity can be seen in figures 7 and 8. It should be known that the observed sponges found on the plates would have been at most 4 months of age, giving a potential insight to the initial juvenile adult stages such as seen in figure 3. It can be seen through the smaller observed Clathrina sponges, that growth begins with the peduncle. The tubular structure is minimalistic during initial growth stages with little anatomisation of tubes. The specimen can be seen to have a cormus with its peduncle, and as tubes form, they are quite tight in aggregation, irregular in structure and causes the sponge to become more bulbous as growth proceeds meeting at the central fringed osculum (Fig. 3). The spicule type of this sponge is unknown due to losing the specimen while this page was in development but can have a range of possibilities found in the Clathrina species such Diactine, Triactine and Tetractine spicule types (Klautau et al. 2008).

The settlement location of the juvenile sponge larvae is determined by three variables, phototaxis, chemotaxis and geotaxis. The Clathrina species found was only present on the underside of the ARMS settlement plates suggesting that larvae were sensitive to light and geotaxis. This correlates with the majority of Clathrina and other sponge species that are typically found to have a negative response to light and settle as an encrusting organism on the underside of rocks, ceilings or roofs of caves in the benthic substrate (Padau et al. 2016; Maldonado et al. 2003).

Prior to settlement annual variations in growth have been observed in Clathrina species depending on the relevant depth at which it was observed, which has been related to differences in water temperature or harsh winters that become unfavourable to the sponge (Gaino et al. 1991).

Figure 7
Figure 8

Anatomy and Physiology


            The exact physiology of this Clathrina species cannot be inferred but assumptions can be made using studies done on similar species within the genus. In Clathrina species such as Clathrina Clathrus physiological seasonal variations have been observed regarding oxygen consumption and the biochemical relations of the sponge (Burlando et al. 1992; Gaino et al. 1991). It has been displayed that oxygen consumption of Clathrina sponges’ peaks in the summer, and a period of hypo-activity in the winter, with other biochemical variations and seasonality in feeding being caused by cyclic climatic events (Burlando et al. 1992, Gaino et al. 1991). This peak in POM intake can be inferred to be the sponge preparing to undergo spermatogenesis, as the process typically requires higher temperatures (Burlando et al. 1992). However, it has been shown that the seasonal variability of Clathrina sponges is low and they typically can maintain a biochemical homeostasis (Burlando et al. 1992).

            Observations into Clathrina species regulating their pumping rate due to ostial temporal closure, exopinacoderm contraction and choanoderm folding from seasonality has also been observed (Gaino et al. 1991).

Spicule Types

            The spicule type of the observed Clathrina is unknown due to losing the specimen during the making of this webpage. However, inferences can be made due to the importance of spicules in Clathrina sponges, showing this observed Clathrina spp. to possibly lack tetractines and be a more derived type of Clathrina (Fig. 11). The Clathrina species of sponge are typically similar in general morphology, physiology and function but most speciation differences are seen in the spicule composition. The spicule composition of Clathrina sponges affects the general morphology, colour and skeleton type (Rossi et al. 2011). It has been suggested that the presence of tetractines or lack off can separate the lineages in the Clathrina genus (Rossie et al. 2011).

Figure 9


            Sponge species are known to be host to a huge diversity of bacterial symbionts comprising up to 40-60% of sponge tissue value in species (Webster 2007). It has been observed in Clathrina species that they have a symbiotic relationship with bacteria, and in Clathrina sponges, specific types of Spirochaetes have been observed (Neulinger et al. 2010). The exact nature of these sponge derived bacteria have not been found but it can be inferred through the close relatives of the found spirochaetes which belong to marine bivalves and aid in extracellular digestion, which suggests that Clathrina species utilise the extracellular benefits given by the bacteria (Neulinger et al. 2010). Other specific-sponge microbe relationships have thought to benefit the sponge through assisted provisioned nutrition, transportation of waste and active metabolites, chemical defence or a contribution to the mechanical structure of the sponge (Webster 2007).

            Marine fungi have also been observed in Clathrina species as a symbiont, with the functions associated being largely unknown (Ding et al. 2011).

Biogeographic Distribution

Local Distribution Observed

            The Clathrina species observed on the ARMS plates was found in the Moreton Bay and Stradebrook area of South East Queensland Australia (Fig. 10). This sponge has not been observed in previous years of observations in the same areas and a higher level of rainfall was seen this year (2021) that would have led to higher levels of sediment and lower salinity in the bay regions that they were observed in. This suggests that it is distributed reef habitats of South East Queensland that typically receive high levels of sediment, possibly around bays, deltas and shallow reefs. The Clathrina was only found on the underside of settlement plates suggesting a preference towards sheltered / shadowed rocks and reefs. Due to the exact species of the observed Clathrina being unknown it is impossible to know the full distribution.

Figure 10

Global Distribution

            Clathrina sponges are observed globally in a broad range of marine habitats (Klautau & Valentine 2008). The sponge observed matches morphological traits displayed by Clathrina Lacunosa, which is found around the coast of Norway and the English Isles, typically in cooler temperate waters with higher levels of nutrients available (Rapp 2006). This would match the traits that excessive rainfall would have on the waters around the Moreton bay region, making waters cooler and heightening nutrients and sediment which could suggest that the observed sponge is an invasive species that was carried through human activity in shipping hulls or bilge water.

Evolution and Systematics


            The genus of Clathrina lies under the Calcareous sponges and is mostly defined by negative characters (Borojevic & Boury-Esnault 1987). The Clathrina sponge is known for having the simplest of organisation features among the sponges, with an Asconoid structure, simple skeleton, and few spicule types, limited to three 1) diactine 2) triactine and 3) tetractine (Kalutau & Valentine 2008). Due to absence of morphological factors and limited skeletal composition the Clathrina sponge produces the difficulty of systematics of the genus (Borojevic & Boury-Esnault 1987). The only way to reliably identify a Clathrina to a species level is through the use of external morphological traits and the spicule composition. (Klautau & Valentine 2008). The first recognised Clathrina sponge was the Clathrina clathrus recognised in 1864.

            The broader genus of Clathrina sponge can be split into two distinct lineages, those with tetractines, and those without (Rossi et al. 2011). It can then be further derived through a series of characters such as the organisation of the cormus, spicule types and organisation of the skeleton (Klautau & Valentine 2008). It has been thoroughlly discussed that the phylum of Porifera is paraphyletic, and even suggested that the class of Calacerea sits outside of the Porifera phylum due to its negative characteristics and differences from other sponge classes (Borchiellini et al. 2001). It can be inferred through the observed morphological traits discussed that the observed sponge is one of the more derived species in the paraphyletic tree (Fig. 11).

Figure 11


Phylum: Porifera

Class: Calcarea (Bowerbank, 1864)

Subclass: Calcniea (Bidder, 1898)

Order: Clathrinida (Hartman, 1958)

Family: Clathrinidae (Minchin, 1900)

Genus: Clathrina (Gray, 1867)

Species: Unknown

Conservation and Threats

            Sponges are one of the most important animals in the ocean ecosystem and are essential for reef habitats to survive due to their numerous biological and ecological properties that make them an influential component to the reef life. The main issue towards all marine species is that of climate change and the effects of temperature stress on marine invertebrate species that facillitates lower competition towards invasive species, reduced immune defences and shifting habitats (Webster 2007).
   The rising threat towards sponges is that of disease, similar to that of coral species (Webster 2007). The threat of disease is thought to originate from the relationship with symbiotic microbial activity in sponges. This threat is further amplified by climate change and the interactions that temperature has on microbes. As climate change continues, and water temperatures rise the prevalence of disease for sponge species increases as it is facilitated by warmer waters, high temperatures, anthropogenic pollution, nutrient enrichment and introduced species (Webster 2007). It has been demonstrated that sponge disease targets the skeletal structure of the sponge causing it do crumble and mortally wound the sponge.


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