BBSR
Marine Invertebrates of Bermuda

Chicken Liver Sponge (Chondrilla nucula)

Alicia Shepard
and
James B. Wood (Ed)



Abstract


Chondrilla nucula is a common sponge found in the waters of Bermuda. C. nucula has a greenish to brown color and is thickly encrusting (Sterrer 1986). It can grow up to 15 cm in different morphologies of either thin encrusting on reefs, thick encrusting in sea grass beds, or lobate clumps around mangrove roots (Swearingen & Pawlik 1998). C. nucula can be found in dark caves as well as illuminated habitats which can affect their coloration from a green to a pale yellow respectively (Sterrer 1986). C. nucula can adapt to survive in very shallow regions as well as deeper reefs up to 5m in depth (Sterrer 1986). These sponges have toxins present in them that deter fish predation (Swearingen & Pawlik 1998) and allow them to compete for space on reefs (Vincente 1990). This paper reviews the literature about C. nucula and outlines the habitat, ecology, commercial importance, recent research and the Bermudian laws pertaining to it.

Taxonomy


Phylum:Porifera
  Class:Demospongiae
    Order:Chondrosida
      Family:Chondrillidae

The phylum Porifera is composed of organisms that are generally sedentary, aquatic, filter feeding Metazoans (Sterrer 1986). The sponges create unidirectional water flow throughout their body to remove planktonic, and particulate matter to feed on (Sterrer 1986). This water enters the sponge through ostia, which are like pores, and leaves through a larger opening called the oscula (Sterrer 1986). Demospongiae have silicious spicules or spongin fibers and many times encompass both types (Sterrer 1986). The family Chondrillidae are astrophorida that have reduced spicule content (Sterrer 1986).

Habitat


Chondrilla nucula lives in both tropical and temperate environments and on a wide variety of substrates including reefs and mangrove roots (Usher et al. 2004, Swearingen & Pawlik 1998). C. nucula is an encrusting species appearing as a thin sheet over the substrate, but can also be found in globular morphology as well (Swearingen & Pawlik 1998). C. nucula. is extremely common in shallow inshore waters (Vincente 1990, Sterrer 1986). C. nucula can survive in dark habitats such as caves, and illuminated habitats such as reefs at any depth between .5-5 m (Sterrer 1986). C. nucula is known to be an aggressive species and overgrows many other organisms, commonly sessile corals (Vincente 1990).

Ecology


Chondrilla nucula is important ecologically because it plays a large role in competing in reef ecosystems (Sterrer 1986, Vincente 1990, Swearingen & Pawlik 1998). C. nucula is capable of utilizing allelopathy, emitting chemical toxins, to overgrow numerous sessile organisms in reef environments (Vincent 1990). Vincent (1990), explains that in his study 9 out of 13 species of corals found to be interacting with C. nucula were partially or fully encrusted by the sponge. Vincente (1990) also states that 43%-51% of all coral overgrowths in his study were attributed to C. nucula. Suchanek et al. (1983), expresses that in their study 24%-34% of the substrate is overgrown by C. nucula. In an ecosystem the affect of one species being able to out-compete most other species is dramatic causing a large decrease in diversity.

Chondrilla nucula also uses allelopathy to protect itself against predation by reef fish (Swearingen & Pawlik 1998). In coral reef environments the dominant predators are fish (Swearingen & Pawlik 1998). C. nucula has been able to diminish the affect of predation by protecting itself with numerous varying secondary metabolites (Swearingen & Pawlik 1998). C. nucula excretes different types of chemicals depending on its colony and habitat (Swearingen & Pawlik 1998). C. nucula have different levels of toxins present temporally and globally (Swearingen & Pawlik 1998). The C. nucula that thrive in mangrove areas have significantly different levels of chemical extract than the C. nucula inhabiting reef areas. Swearingen & Pawlik (1998), examined the possibility that the C. nucula in the reef environments would contain a greater level of chemicals than the organisms at the mangroves because the reef inhibitors are more prone to spongivory. This expectation was false and actually in some cases the C. nucula living in the mangroves actually produce more toxins than their reef inhabiting counterparts. Therefore, the special difference in production of toxins is probably not related to fish predation. Another study examines predation of C. nucula by the green turtle Chelonia mydas (Bjorndal 1990). This study suggests that green turtles eat sponge because it plays a major role in their nutrition (Bjorndal 1990). It is likely that the spicule content and toxins present in C. nucula deter some predation and the green turtles consume very little of this organism in order to be able to digest it (Bjorndal 1990).

Chondrilla nucula is distributed throughout the Caribbean and Mediterranean (Usher et al. 2004, Swearington & Pawlik 1998). The reproduction of C. nucula has been examined showing that fertilization takes place internally (Sidri et al. 2005). Oogenesis by C. nucula causes the morphology of the sponge to alter so that approximately 1/3 of the sponge body becomes filled with oocytes and all of the choanocytes disappear in the reproductive area of the sponge (Sidri et al. 2005). Also regeneration rates in C. nucula are very fast so that they can recover easily when disturbances occur (Swearington and Pawlik 1998). C. nucula also utilizes a modular growth system as a reproductive method, where it produces clones of itself to form patches on the substrate (Milanese et al. 2003).

Sponges create unidirectional water flow throughout their body to remove planktonic, and particulate matter to feed on (Sterrer 1986). This water enters the sponge through ostia, which are like pores, and leaves through a larger opening called the oscula (Sterrer 1986). Chondrilla nucula is capable of retaining 80% of suspended particles in the surrounding water column within 24 hours (Milanese et al. 2003). C. nucula is considered an extremely efficient feeder because of its high retention rate of food particles (Milanese et al. 2003).

Another ecological aspect of Chondrilla nucula is that it plays host to a variety of endosymbiotic bacteria (Hill et al. 2006, Maldonado et al. 2005). C. nucula has been found within the mesohyl, in choanocytes, and in digestive vacuoles (Wilkinson 1978). These bacteria are distinct to the sponge and very different from the bacteria found in the surrounding water column (Wilkinson 1978, Hill et al. 2006). The presence of such a large amount of diversity and quantity of bacteria in marine sponges makes these populations significant to the microbial communities of the oceans (Hill et al. 2006).

Chondrilla nucula likely plays a very significant role in marine ecosystems. By overgrowing corals and other benthic organisms, utilizing allelopathy to defend itself, and playing host to a variety of symbiotic bacterium C. nucula influences the surrounding environment greatly. Chondrilla nucula’s large range of distribution and reproductive strategies will allow this sponge to continue to thrive in the worlds oceans.

Recent Research


The recent research being conducted on Chondrilla nucula is generally focused on the microbial communities living within them (Hill et al. 2006, Maldonado et al. 2005). One paper discusses the discovery of chitinous-walled fission yeast that has become symbiotic with C. nucula (Maldonado et al.2005). Previous studies had shown that there are symbiotic bacteria and cyanobacteria present in sponges, but never before have fungal symbionts been seen within sponges (Maldonado et al. 2005). This study was even more interesting upon the discovery that the yeast is actually present in the oocytes of the sponge (Maldonado et al. 2005). The sponge nurse cells actually select the bacteria, cyanobacteria, and fungal endosymbionts that will be vertically passed down to the further generations of sponge (Maldonado et al. 2005). This supports the idea that these endosymbionts are important to the sponge’s existence and it is likely that the endosymbionts provide nutrients, protection from UV light, and possibly predator deterrent chemicals (Maldonado et al. 2005). The discovery of fungal endosymbionts in C. nucula is important and will likely lead to many future studies to determine a more precise function of this symbiotic relationship.

Another recent publication discusses the microbial diversity in Chondrilla nucula (Hill et al. 2006). This study wanted to analyze the diversity in order to try to identify the different symbionts which could provide information on sponge growth and metabolism (Hill et al. 2006). At least two species were found that were sponge-specific, and also their data supported the idea that the sponge harbored endosymbionts are similar over great geological distances and likely show an ancient symbiosis (Hill et al. 2006). This study also found a previously unknown sponge-associated microbial lineage which was determined by genetic analysis (Hill et al. 2006). This study also proposes the idea that the reason that there is a great deal of temporal and geographical similarities of sponge associated microbial communities could be due to host control of the symbionts (Hill et al. 2006).

Commercial Importance


Chondrilla nucula is important in bioremediation of seawater in many aquaculture situations (Milanese et al. 2003). By utilizing C. nucula aquaculture can maintain seawater that is generally devoid of particulate matter which C. nucula absorbs as food (Milanese et al. 2003). C. nucula is also cultured in order to provide biomass for scientists to continue to look for novel chemicals that may be used in biomedical studies (Donati et al. undated). Many compounds found in C. nucula are considered to be bioactive, or have an effect on living tissue, and therefore could be important in many medical studies (Milanese et al. 2003).

Bermuda Laws


The Coral Reef Preserve Act protects Chondrilla nucula and other marine life on the Bermuda Platform. The Bermuda National Park Act of 1986 also protects mangroves which subsequently affects the protection of C. nucula.

Personal Interest


Chondrilla nucula plays host to a high diversity of microbial communities (Wilkinson 1978, Hill et al. 2006, Maldonado et al. 2005). I have been involved in previous research on microbial communities in the water column, specifically viral and bacterial interactions and the evolution of genetically diverse bacteria. Since C. nucula supports a highly diverse microbial community I thought it would be interesting to learn more about the information they have about the symbionts of C. nucula. Since many of the bacterial communities found in C. nucula are sponge-specific I think further study should be done to determine if there are viruses present in these bacterial communities, and how they might contribute to the high levels of diversity found there. I also thought that the allelopathy utilized by this sponge to compete for space was very interesting.

Links

Sponge-specific bacterial symbionts in the Caribbean sponge, Chondrilla nucula
First observations on egg release in the oviparous sponge Chondrilla nucula (Demospongiae, Chondrosida, Chondrillidae) in the Mediterranean Sea