Premnas biaculeatus
maroon clownfish
(Also: spinedcheek anemonefish; spinedcheeked anemonefish)

Spinecheek anemonefish, Premnas biaculeatus, are found in the Indo-West Pacific, including the coasts of India, Burma, Thailand, Malaysia, Indonesia, Philippines, New Guinea, New Britain, Solomon Islands, Vanuatu and northern Queensland. (Capuli and Santos, 2006)

The most important aspect of spinecheek anemonefish habitat is the host anemone. Entacmaea quadricolor, bulb-tentacle sea anemones, are the only host species for spinecheek anemonefish. This anemone species is characterized by polyps 50 to 400 mm in diameter, depending on depth. They have brown tentacles of about 100 mm long with a red tip and white bulb at the end of the tentacle. Spinecheek anemonefish tend to live mainly in solitary specimens of Entacmaea quadricolor on reef slopes. The typical water depth is less than 50 m, because anemones require sunlight to grow. The mutualistic zooxanthellae (living within the anemone) need this sunlight to photosynthesize and provide energy for themselves and the anemone. These anemone prefer tropical warm waters with the temperature ranging between 25 and 28°C (77-82°F). (Fautin and Allen, 1992)

Spinecheek anemonefish are among the easiest anemonefish to identify, even when young. They are bright red with 3 bars that are bright white in males and grey in females. Individuals may become bright white if they are provoked. The lines may also be bright yellow. (Fautin and Allen, 1992)

The developmental stages of spinecheek anemonefish are egg, larvae, young and adult. The transparent, elliptical eggs are 3-4 mm in size. Anemonefish hatch with advanced alimentary canals and feed on the yolk, which usually lasts for about 3 days. Five days after hatching they develop supranuclear inclusions around the hindgut, which suggests pinocytotic digestion of protein. Between 3 to 5 days after hatching is the period of highest mortality stage for anemonefish if they cannot find food. It is also the time when they transition from endogenous to exogenous feeding. Seven days after hatching they attain gastric glands and by the 9th day they have supranuclear vacuoles that indicate exogenous digestive capabilities. Spinecheek anemonefish hatch 6 to 7 days after fertilization, and then undergo a 7 to 14 day pelagic larval stage. After fertilization, they complete the development of the olfactory organ in 19 days, retinal differentiation in 20 days and skeletal ossification in about 22 days. Spinecheek anemonefish develop more rapidly than other anemonefish species. Their eyes develop especialy rapidly. Vision is directly correlated with the ability to attain food because most larval fish are visual feeders. Olfactory cues are used to detect host anemones. During the larval stage spinecheek anemonefish live on the water surface where they are transported by currents. (Coughlin, 1994; Gordon and Hecht, 2002; Job and Bellwood, 1996; Kavanagh and Alford, 2003)

Metamorphosis occurs when anemonefish leave surface waters and swim to the sea bottom. It then takes on the color pattern of a juvenile. This process usually takes about one day. This marks the beginning of the settlement period, in which individuals seek out an uninhabited anemone host. (Coughlin, 1994; Gordon and Hecht, 2002; Job and Bellwood, 1996; Kavanagh and Alford, 2003)

Spinecheek anemonefish, like other anemonefish species, are protandrous hermaphrodites, which means that they change from male to female. Females have gonads that function as ovaries with leftover male testicular tissue. In the case of spinecheek anemonefish, males may be half the size of females and their gonads have dormant ovarian cells as well as functioning testes. (Fautin and Allen, 1992)

The lifespan of spinecheek anemonefish has not been well researched. They live longer in the wild, ranging from 6 to 10 years, and about 3 to 5 years in captivity under good conditions. A related species, Amphiprion perideraion, was recorded living to 18 years. (Fautin and Allen, 1992; Kramer, 2005)

Spinecheek anemonefish have a social hierarchy in which fish that occupy the same patch of anemones are ordered in status by size. Generally there is a breeding pair and then 0 to 4 non-breeders. The largest is the female of the group (highest rank), followed by the largest male, who is part of the breeding pair. In the case of the death of the female, the second largest changes from male to female. Size difference is maintained in order to avoid subordinates becoming a threat to the highest ranking male. There is an average difference of 10 mm between ranks in the related anemonefish, Amphiprion percula. When a dominant anemonefish dies, the next subordinate moves up in the rank order and grows further. (Buston, 2003)

Spinecheek anemonefish are active during the day. Once they settle onto an anemone as a juvenile, and then adult, they remain in the same area throughout their life.

Home Range

Spinecheek anemonefish are territorial, defending the area around their host anemone. Usually one anemone hosts the breeding pair and 4 to 5 other non-breeding males. (Buston, 2003; Fautin and Allen, 1992)

Mates communicate in courtship through movement and touch. During spawning, females swim in a zig-zag pattern over the nest while the male fertilizes the eggs. Males also “shows off” their fins to females, a form of visual communication. (Fautin and Allen, 1992)

Spinecheek anemonefish have a diet rich in copepods and planktonic, larval tunicates. They also eat other kinds of plankton and algae. (Fautin and Allen, 1992)

The most vulnerable stage for spinecheek anemonefish is during the egg and larval stage, when they are not protected by a host anemone and float freely in the water column. As settled adults, Entacmaea quadricolor protects these symbiotic fish because of their ability to deliver a venomous sting. Wrasses are known to prey on eggs and other fish are likely predators of eggs, larvae, and unsettled juveniles. (Coughlin, 1994; Fautin and Allen, 1992)

Spinecheek anemonefish and their host anemones have a mutualist relationship. Entacmaea quadricolor benefits from having spinecheek anemonefish protect them from butterflyfish (Chaetodontidae), which would otherwise eat their tentacles. Spinecheek anemonefish also clean away debris and parasites from the anemone. Spinecheek anemonefish are protected from most predators through their association with venomous anemones.

There are no known adverse effects of the spinecheek anemonefish on humans.

Spinecheek anemonefish are important to the aquarium suppliers who sell them for profit. These anemonefish, and their relatives, are important ecotourist draws for diving operations. Their symbiotic relationship with Entacmaea quadricolor, helps to protect these anemones.

Although spinecheek anemonefish are not endangered, there are concerns for populations and their reef habitats due to the "Nemo craze". In the last generation 15 to 30% of the world's reefs have been lost. After release of Disney's "Finding Nemo" movie, which has an anemonefish as its main protagonist, anemonefish sales have increased. Collecting methods are often extremely destructive, permanently damaging reefs. (Osterhoudt, 2004)