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).
HABITAT AND DISTRIBUTION
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.
Boring sponges are found throughout the Indian River Lagoon.
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).
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).
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).
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).
There are no specific studies addressing the effects of temperate on boring sponges.
The distribution of species in the genus Cliona correlates with salinity of coastal seawaters (Wells 1961). Species such as C. truitti and C. vastifica are reported to do well in brackish waters while C. celata, an abundant species, is usually encountered at salinities greater than 15ppt (Wells 1961, Hopkins 1962).
Boring sponges are filter-feeders but also derive nutrients from symbiotic zooxanthellae.
Cliona spp. live in oyster hosts, including Crassostrea virginica, C. gigas, Ostrea edulis, Pinctada maxima, as well as scallops, mussels and dead and live coral.
Shell-burrowing sponges that are introduced to fields of commercially exploited shellfish can cause mortality if the sponge tunnels weaken the oyster and interfere with the abductor mussel attachment. In addition, other invertebrates that inhabit the tunnels made by the sponge can reduce the market value of the shell. Cliona spp. have been particularly destructive to pearl oysters in Australia (Fromont et al. 2005).
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