Common Name:
Boring Sponges, Shell-burrowing Sponges

Synonymy:
Anthosigmella Topsent, 1918

Species Description:
Sponges in the genus Cliona are members of the family Clionaidae. They are efficient excavators of calcareous materials including corals and shells. Boring (burrowing) sponges create a canal system by chemically etching out coral or shell material for shelter and during the process simultaneously create sediment (Holmes 2000). Cliona spp. are not predators and do not derive any nutrients from their host, however they are competitors for space on appropriate substrata (Lopez-Victoria and Zea 2005). This is a highly adaptable genus of sponge that not only excavates, but is also capable of encrusting the surface and smothering the host. There is evidence of Cliona spp. in the fossil record as early as the Lower Cambrian (Ward and Risk 1977). Boring sponges range in color from yellow to dark-brown to black brown with a yellow oscula (Leidy 1889, Zea and Weil 2003, Vacelet et al. 2008). Many species are host to symbiotic zooxanthellae (Mariani et al. 2000, Vacelet et al. 2008).

II.  HABITAT AND DISTRIBUTION 

Regional Occurrence:
The genus Cliona has a global distribution (Leidy 1889) occurring in shallow water estuaries to 30 m (Wells 1961,Vacelet et al. 2008). Certain species may be limited in region.

IRL Distribution:
Boring sponges are found throughout the Indian River Lagoon.

III. LIFE HISTORY AND POPULATION BIOLOGY

Age, Size, Lifespan:
Cliona spp. can be very large extending up to several square meters (Vacelet et al. 2008). The size of the sponge is often limited by light availability (Lopez-Victoria and Zea 2005).

Abundance:
The abundance of the boring sponge increases as a function of eutrophication (higher concentrations of nutrients) and may result in the decline of coral reefs (Holmes 2000). Its abundance is also dependent upon the available carbonate substrata (corals and shellfish). In the waters of the Mediteranean Sea near Blanes, sponge cover was reported as 2 to 8% in the photophilic community, 5 to 30% in the sciaphilious community, and up to 7% in caves (Mariani et al. 2000).

Reproduction:
Cliona spp. can undergo asexual and sexual reproduction. Synchronys spawning is reported to occur at different times of the year depending upon the species and region. In the Adriadic and Meditteranean seas, fertilization and spawning takes place from May to June. Asexual reproduction occurs during the encrusting phase (i.e. overgrowth of adjacent substrata) of the sponge (Mariani et al. 2000).

Embryology:
The embryology of boring sponges is similar among different species. For Cliona viridis, the free larva is a parenchymella, measuring approximately 250 to 300 _m long and 100 _m wide. The parenchymella is a weak swimmer that moves by crawling and thus has a limited dispersal radius. Ten to 15 days after settlement, larvae undergo metamorphosis and develop into a juvenile sponge. One month old sponges have abundant zooxanthellae (Mariani et al. 2000). In a laboratory study of another boring sponge, Cliona celeata, larvae were observed to swim continuously for 20 to 30 hours. They entered a creeping phase that lasted the same amount of time and ultimately settled (attached and metamorphosed) on calcite or glass substrata (Warburton 1962).