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Cnidarian Aggression

Zooplankton Prey

Zooxanthellae provide their coral hosts with a proportion of their required energy (Barnes & Hughes, 1999). As well as gaining energy from their symbiotic zooxanthellae, many corals feed at night by consuming zooplankton prey (Barnes 1987, Sebens et al. 1996, Ferrier-Pages et al. 2003). By extending their tentacles equipped with stinging nematocyst cells, corals are able to capture the zooplankton in the water column. The trapped prey is then transported to the centre of the polyps' oral disk and ingested through the gastrovascular cavity. In addition to capturing zooplankton, many corals also collect fine particles in mucus film or strands covering their surface. The mucus and trapped particles are then transported to the mouth by the cilia at the coral tissue surface (Barnes & Hughes, 1999). In this video, corals are using their nematocyst-laden tentacles to capture food particles from the water column, drawing them towards the mouth for ingestion. 

Credits 
Cinematography: Neilan Kuntz 
Edited by: Neilan Kuntz 
Written by: Neilan Kuntz 
Location: Bocas del Toro, Panama (2003) 

Barnes, R. (1987) Invertebrate Zoology. 5th Edition. Orlando, FL: Harcourt Brace Jovanovich, Inc. pp. 149-163. 

Barnes, R., R. Hughes (1999). An Introduction to Marine Ecology. 3rd Edition. Malden, MA: Blackwell Science, Inc. pp. 117-141. 

Ferrier-Pagés, J. Witting, E. Tambutté, K.P. Sebens (2003) Effect of natural zooplankton feeding on the tissue and skeletal growth of the scleractinian coral Stylophora pistillata. Coral Reefs 22(3): 229-240. 

Seben KP, K.S. Vandersall, L.A. Savina, K.R. Graham (1996) Zooplankton capture by two scleractinian corals, Madracis mirabilis and Montastrea cavernosa, in a field closure. Marine Biology 127(2): 303-317


Hydrocorals

Hydrocorals are not true corals, but are member of the class Hydrozoa. Like their close relatives, hydrocorals are also equipped with stinging nematocyst cells that release a virulent toxin when they come in contact with another organism (Wittle et al., 1974). Competitive, hydrocorals in the genus Millepora are often conspicuous and form spatially dominant colonies in reefs (Witman, 1988). The following footage demonstrate the competitive ability of a Millepora spp. colony that has pierced the tissues of an adjacent soft coral.







Credits
Cinematography: Neilan Kuntz
Edited by: Neilan Kuntz
Written by: Dr. Olga Pantos
Location: Bocas del Toro, Panama (2004)

Witman, J.D. (1992) Physical disturbances and community structure of exposed and protected reefs: a case study from St. John, US Virgin Islands. American Zoologist 32: 641-654.

Wittle, L.W., E.D. Tscura et al. (1974) Stinging coral (Millepora tenera) toxin: a comparison of crude extracts with isolated nematocyst extracts. Toxicon 12(5): 481-486. 



Colony Aggression

Corals fight for space on reefs. One type of aggressive behavior involves the use of their sweeper tentacles and extruded digestive filaments (Lang and Chornesky, 1990). Typically, upon contact an aggressive coral will attack its neighbor resulting in the mortality of the damaged tissue (Lang, 1973). The following sequence illustrates two adjacent corals of the same species (distinguished only by their pigmentation) that have a defined boundary at the interface of the colonies where the polyps have died. It appears that corals of the same species but of different colonies can be antagonistic to one another.






Credits
Cinematography: Dr. Forest Rohwer
Edited by: Neilan Kuntz
Written by: Neilan Kuntz
Location: Borneo, Malaysia (Sipadan) (2002)

Lang, J. and E.A. Chornesky (1990) Competition Between Scleractinian Reef Coralsâ€A review of mechanisms and effects, pp. 209-257. In:Z. Dibinsky (ed.), Coral Reefs’ Ecosystems of the World. V. 25. New York: Elsevier.

Lang, J. (1973) Interspecific Aggression by Scleractinian corals. 2: Why the Race is Not Always to the Swift. Bulletin of Marine Science 23: 260-279. 



Cnidarian Abrasion

Sea anemones, along with hydrozoans and jellyfish belong to the phylum Cnideria, which is characterized by specialized stinging cells called nematocysts. Nematocysts are used to hunt and defend against predators* (Kass-Simon and Scappaticci, 2002). In addition to the nematocysts found within the tentacles, some sea anemones have specialized fighting tentacles or acrorhagi. After making contact with another organism, these hollow structures expand and adhere to the other organism. The nematocysts continue to fire resulting in the process referred to as "peeling" where the tissues beneath the acrorhagi to become necrotic and peel off (Bigger 1988). In the following clip, a sea anemone has attached itself between two coral colonies and has killed all of the coral tissue within its reach. 
*Refer to Net Trapping for hunting

Credits
Cinematography: Neilan Kuntz
Edited by: Neilan Kuntz
Written by: Dr. Olga Pantos
Location: Bocas del Toro, Panama (2003)

Bigger, C.H. (1988) The role of nematocysts in anthozoan aggression. In: the biology of nematocysts. Edited by D.A. Hessinger and H.M. Lenhoff. Academic Press, Inc., San Diego. Pp. 295-308.

Kass-Simon, G. and Scappaticci, A.A. (2002) The behavioral and developmental physiology of nematocysts. Canadian Journal of Zoology 80: 1772-1794.