The association that exists between burrowing shrimp and gobiid fish found on many tropical reefs is mutually beneficial (for review see Karplus 1987). Shrimp of the genus, Alpheus, construct burrows for both themselves and the fish to reside. In return, the gobies provide protection and early warning signals against predators for the shrimp. The warning signals consist mostly of a rapid tail flick that is detected by the shrimp through its long antennae, which remain in constant contact with the goby. Karplus (1979) showed that the relationship is obligate for several shrimp-associated gobies with goby mortality being higher when the gobies are excluded from the burrows. Without the protection of gobies the shrimp do not emerge from their burrows and burrow less frequently resulting in slower growth rates, as digging activity for their benthic prey is reduced. The distribution of burrowing shrimp and gobiid fish is based on habitat selection of the burrowing shrimp (Thompson 2004). Thomas (2004) found a significant non-linear correlation between the maximum density of goby-shrimp associations at approximately 70% sand to 30% rubble substrate. The following footage shows the mutualistic behavior and habitat selection of the shrimp-goby association.

Credits
Cinematography: Dr. Forest Rohwer
Edited by: Neilan Kuntz
Written by: Neilan Kuntz
Location: Borneo, Malaysia (Sipadan) (2003)

Karplus I. (1979) The tactile communication between Cryptocentrus steinitzi (Pisces, Gobiidae) and Alpheus purpurilenticularis (Crustacea, Alpheidae). Zeitschrift fur Tierpsychologie. 49, pp 173-196.

Karplus I. (1987) The association between gobiid fishes and burrowing alpheid shrimps. Oceanography and Marine Biology 25: 507-562.

Thompson A. R. (2004) Habitat and mutualism affect the distribution and abundance of a shrimp-associated goby. Marine and Freshwater Research 55: 105-113.

Cleaning symbioses are a ubiquitous behavior found in reef fish dynamics. Numerous species of fish and shrimp remove ectoparasites from other organisms. Some cleaners are obligate, such as the wrasses of the genus, Labroides, or facultative, such as some fish during the juvenile stage (Moosleitner 1980). Ectoparasites are common throughout reef fishes. For example, 44% of the 200 observed fishes on the Great Barrier Reef had the parasitic worm, Bucephalid metacercariae (Jones et al. 2004). The parasite is consumed by the cleaner as a dietary source (Jones et al. 2004). Removal of cleaner fish has been shown to indirectly decrease the diversity and abundance of fish that move between reefs, as these fish appear to choose reefs based on the presence of cleaner fish (Grutter et al. 2003). The following footage shows the interaction between the cleaner and client.

Credits
Cinematography: Dr. Forest Rohwer
Edited by: Neilan Kuntz
Written by: Neilan Kuntz
Location: Borneo, Malaysia (Sipadan) (2003)

Grutter A.S., J.M. Murphy, J.H. Choat (2003) Cleaner fish drives local fish diversity on coral reefs. Current Biology 13: 64-67.

Jones C.M., A.S., Grutter, T.H. Cribb (2004) Cleaner fish become hosts: a novel form of parasite transmission. Coral Reefs 23: 521-529.

Moosleitner V.H. (1980) Cleaner fish and cleaner shrimps in the Mediterranean. Zool. Anz. Jena 205: 219-240.

Anemonefish of the genera Premnas and Amphiprion maintain a symbiotic relationship with sea anemones. The sea anemones produces toxins, which are transmitted via the nematocyst cells in their tentacles for defense and prey capture *. The fish have a resistance to these toxins allowing them to live amongst the tentacles of the sea anemone. The anemonefish forms an obligate association with their host which provides a safe location for oviposition (laying of eggs) and protection from predators (Allen 1972). In return anemonefish have been observed to defend its host from its main predator, the chaetodontid butterflyfish. Sea anemone toxins can be divided two types: those that damage membranes by forming pores (cytolysins); and, those that affect nervous structures (neurotoxins that disrupt ion channels; Kem 1988). Resistance to these toxins has evolved in some species of Amphiprion but is not a major attribute allowing them to live amongst the stinging tentacles (Mebs 1994). The main factor attributing to resistance is the skin's mucus layer of the fish (Mebs 1994). Group size living within an anemone commonly increases linearly with the host's size and residents set an upper limit by evicting low-rank subordinates and preventing recruitment of additional subordinates (Buston 2003). The following footage shows several anemonefish and their association with a sea anemone. Note that one segment of the film shows an anemonefish defending against an intruding fish.
* See video section on Cnidarian Aggression

Credits
Cinematography: Dr. Forest Rohwer
Edited by: Neilan Kuntz
Written by: Neilan Kuntz
Location: Borneo, Malaysia (Sipadan) (2003)

Allen G. R. (1972) The anemonefish: their classification and biology. 2nd ed. Neptune City, New Jersey: T.F.H. Publications

Buston P. (2003) Forcible eviction and prevention of recruitment in the clown anemonefish. Behavioral Ecology 14, pp 576-582.

Kem W. R. (1988) Sea anemone toxins: structure and action. In: The Biology of Nematocysts, pp. 375-405 (Hessinger, D. A. and Lenhoff, M. H., Eds.) San Diego: Academic Press.

Mebs D. (1994). Anemonefish symbiosis: Vulnerability and resistance of fish to the toxin of the sea anemone. Toxicon 32: 1059-1068.