By Monica Weinheimer
Diversity
Pomacentrids, commonly known as damselfishes and anemonefishes, are one of the most abundant and widely-studied families of tropical reef fishes. Small and brightly colored, they are popular aquarium fish. The family Pomacentridae consists of approximately 28 genera and 335 species. They tend to be territorial and can be aggressive, although this is not the case for the non-territorial, free-swimming planktivores or the anemonefishes (Amphiprion and Premnas) that live commensally with anemone hosts. Damselfishes are largely herbivorous, sometimes tending “gardens” of filamentous algae, but may eat tiny invertebrates, or in the case of anemonefishes, anemones and other organisms living symbiotically with anemones. Damselfishes manifest a range of reproductive behaviors, with groups that are polygynous, promiscuous, polyandrous, and monogamous. Anemonefishes are able to change from male to female under certain conditions (see Reproduction: Mating Systems). (Allen, 1998; Böhlke and Chaplin, 1994; Helfman, Collete, and Facey, 1997; Nelson, 1994; Thresher, 1984)
Geographic Range
Pomacentrids are found throughout the world in tropical and warm temperate waters, with the majority of species occurring in the Indo-west and central Pacific region. (Allen, 1998; Helfman, Collete, and Facey, 1997; Nelson, 1994; Thresher, 1984)
Biogeographic Regions:
oriental 
(native ); ethiopian (native ); neotropical (native ); australian (native ); oceanic islands (native ); indian ocean (native ); atlantic ocean (native ); pacific ocean (native ).
Other Geographic Terms:
cosmopolitan .
Habitat
Pomacentridae primarily inhabit tropical reef habitats. Some live along steep edges of the reef, and others in sandy sheltered lagoons. In each ocean a few species occupy warm temperate waters, and three estuarine species can sometimes be found in fresh water. Some school in the water column, some live on rocky areas or sea-grass beds, and fishes of the subfamily Amphiprionina (anemonefishes) always dwell in association with sea anemones. A few deep-water species occur at the edge of the shelf at depths below 100 m, but most pomacentrids occupy shallow water between two and 15 meters deep. (Allen, 1998; Böhlke and Chaplin, 1994; Helfman, Collete, and Facey, 1997; Hoese and Moore, 1998; Thresher, 1984; Wheeler, 1985)
These animals are found in the following types of habitat:
temperate ; tropical ; saltwater or marine .
Aquatic Biomes:
benthic ; reef ; coastal ; brackish water .
Systematic and Taxonomic History
The family Pomacentridae contains four subfamilies: Amphiprioninae (anemonefishes, containing two genera, Amphiprion and Premnas), Chrominae, Lepidozyginae, and Pomacentrinae. It is divided into approximately 28 genera and 335 species, which have been difficult to classify due to complex variations in color and pattern within species. Morphology varies considerably within many of the genera. (Böhlke and Chaplin, 1994; Nelson, 1994)
Pomacentrids are one of several recently derived families (Acanthuridae, Monacanthidae, Siganidae, Scaridae, Blenniidae) capable of exploiting reef algae and small colonial invertebrates. Reef herbivory was primarily restricted to post-Cretaceous perciformes until these families underwent rapid evolution during the early Tertiary, 50 to 30 million years ago. (Harmelin-Vivien, 2002)
Physical Description
Damselfishes, which include the anemonefishes (Amphiprion and Premnas), range from five to 36 cm, with most specimens less than a foot long. Their bodies tend to be high, oval and laterally compressed, with the lateral line interrupted. The single, continuous dorsal fin has eight to 17 spines and 10 to 18 soft rays, the anal fin usually has two spines (occasionally three), and the caudal fin is typically forked. Adults of many species have filamentous extensions on all but the pectoral fins. Ctenoid scales are present on the body, head, and unpaired fin bases. Pomacentrids, with a few exceptions, have one rather than two nostrils on each side, and a small mouth. The palate is toothless, and the floor of the mouth contains a pharyngeal plate (a triangular fused tooth plate). Teeth may be arranged in one or two rows and may be incisorlike, especially in territorial forms that graze on algae, or conical, often seen in forms that live in the water column and catch small organisms (See an illustration of tooth morphology in fish). Coloration of adult damselfishes ranges from brilliant to drab and can vary with mood and time of day. Juveniles, especially in the territorial bottom-dwellers, often possess different, brighter colors than adults of the same species. (Click here to see a fish diagram).
In most pomacentrid groups males and females differ (sexual dimorphism) externally only in the form of the urogenital papilla, and (except for one species) lack permanent sexual dichromatism. The majority, however, do assume sex-specific colors during spawning. Usually the male, but sometimes the female (and sometimes neither), assumes courtship colors, the pattern and intensity of which vary according not only to species, but also to geographic and perhaps other factors. Adult males tend to be larger than adult females, but the opposite is true for anemonefishes (Amphiprion and Premnas), which are protandrous hermaphrodites: a male can change sex if the dominant female (the largest fish in the group) dies. In these fishes a single individual possesses ovarian as well as testicular tissue. (Allen, 1998; Böhlke and Chaplin, 1994; Helfman, Collete, and Facey, 1997; Moyle and Cech, 2000; Nelson, 1994; Thresher, 1984)
Some key physical features:
ectothermic ; bilateral symmetry .
Sexual dimorphism: sexes alike, female larger, male larger, sexes colored or patterned differently, male more colorful.
Development
Pomacentrid larvae hatch from a clutch of 50 to 2500 eggs, depending on the species. For some the planktonic stage may last only a day while others drift in the open ocean for a few weeks. Juveniles settle in reef areas and their coloration can be quite different from that of adults of the same species. In anemonefishes (Amphiprion and Premnas) one sexually active pair is dominant over a group of juveniles. The young grow slowly in this situation and do not reach sexual maturity until they can replace one of the dominant fish. (Allen, 1998; Hoese and Moore, 1998; Thresher, 1984)
Reproduction
The majority of damselfishes engage in a range of ritualized behavior to attract mates and prepare nest sites. The male, and sometimes the female, begin to groom and tend a rocky surface several days before spawning. He removes invertebrates and algae with his mouth, sometimes allowing certain elements to remain, as is the case with Hypsypops rubicundus, a species that weeds out all but red algae from the site. Courtship activities accompany cultivation of the potential nest. Males may give auditory signals; depending on the stage of courtship, species of Eupomacentrus emit three different types of chirps and grunts. They may also display visual signals, with most damselfish males assuming distinct colors for courtship, and many executing various movements to entice the female to the nest site. Such movements have been described as “leading,” which may include quick bursts of swimming and intermittent hovering in front of the female, “signal-jumping,” or rapid up and down movements, and “dipping,” which is similar to signal-jumping and includes an abrupt descent. (Allen, 1998; Helfman, Collete, and Facey, 1997; Moyle and Cech, 2000; Thresher, 1984)
One group of damselfishes, the anemonefishes (subfamily Amphiprioninae), enter into permanent monogamous pairings and as a rule display a simplified pattern of courtship. Fish in this subfamily are protandrous, a mating system in which male individuals can become female. Ambosexual (neither sperm- nor egg-producing tissues are active) juveniles live on an anemone with a sexually mature male and female pair. If the female dies, her male partner develops into a female to take her place. The largest juvenile grows rapidly and replaces him as the dominant male. (Helfman, Collete, and Facey, 1997; Moyle and Cech, 2000; Thresher, 1984)
Mating systems:
monogamous ; polyandrous ; polygynous ; polygynandrous (promiscuous) .
Damselfishes appear to spawn year-round, with many groups increasing spawning activity in early summer. In the subtropics spawning is usually limited to the warmer months of the year, but a few spawn in fall or winter. It is common for reef-dwelling damselfishes to spawn in accordance with lunar rhythms, with greatest activity occurring near the full and new moons. Spawning usually takes place in the morning. Synchronous spawning has been observed, and in some species, the higher the number of individuals in a group, the higher the degree of synchrony. Some damselfishes spawn within their permanent territory, while others (planktivorous damselfishes that live in the water column) must seek temporary territories for courtship and spawning. Location of a spawning site may involve solitary males or may be a communal activity in which schools of males, juveniles, and females travel until the males form a colony of territories on an acceptable site. Site choice varies according to species and may include rock ledges, cleaned coral branches, algal turf, empty shells, or the roofs of caves. Males typically prepare the site for spawning and then attract gravid (egg-bearing) females to the nest (see Reproduction: Mating Systems). The male guards the nest from predators and other males while the female lays her eggs in long rows, forming a solid, uniform mass of eggs in a single layer. The eggs are demersal (adhere to the substrate), and clutch size varies from 200 to 2500 eggs depending on the species. (Böhlke and Chaplin, 1994; Helfman, Collete, and Facey, 1997; Peterson and Warner, 2002; Thresher, 1984)
Polygyny is common: one male may guard the eggs of several females, and damselfish harems have also been observed. Some damselfish are promiscuous, and still others are monogamous. Polyandry has been reported only in an anemonefish, although monogamy is the general rule for anemonefishes (Amphiprion and Premnas). These fish stay paired for at least a year and sometimes for their entire lifetime. They spawn year-round, usually near the full moon. Hypotheses suggest that lunar spawning occurs because of the increased light for nest tending, the greater currents for larvae dispersal, and the relative abundance of spawning invertebrates as a food source. Anemonefish most frequently live in single pairs, along with a group of sexually immature individuals, in association with an anemone (see Reproduction: Mating Systems). Groups containing several males and females may occasionally occur if the fish population density is extremely high. Spawning occurs at the base of the anemone, on a rock surface, or, if the anemone lives on sand, on a surface the fish drag near the anemone. The male clears the nest site by biting at the tentacles of the anemone until they withdraw, and then leads the female there for spawning, during which both fish quiver and bite the nest surface. (Helfman, Collete, and Facey, 1997; Peterson and Warner, 2002; Thresher, 1984)
Key reproductive features:
iteroparous ; seasonal breeding ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sequential hermaphrodite (protandrous ); sexual ; fertilization (external ); oviparous .
Male damselfishes (and in very few cases, females) guard their eggs until they hatch. They remove detritus, sand, and fungus-afflicted eggs, fan the eggs, and guard against predators. Most become more aggressive when egg-tending, but this is not the case with anemonefishes (Amphiprion and Premnas). In general fry are left to care for themselves after hatching, but in one Indo-Pacific species, Acanthochromis polyacanthus, parents guard their school of young near the spawning cave for three to six weeks. (Allen, 1998; Böhlke and Chaplin, 1994; Froese, Pauly, and Woodland, 2003; Helfman, Collete, and Facey, 1997; Thresher, 1984)
Parental investment:
male parental care ; female parental care .
Lifespan/Longevity
Little is known about the lifespan of damselfish, but Eupomacentris spp. live an estimated six to eight years. Some species may live 10 to 12 years in the wild and perhaps 18 years in captivity. (Allen, 1998; Thresher, 1984)
Behavior
Most pomacentrids, or damselfishes, stake out territories on patches of reef in sheltered areas where they hide, feed and spawn. Males aggressively defend these territories, allowing thick algal growth that provides them a primary food source. Sometimes females have territories near the males. Relations between damselfishes and other fishes are not always agonistic, as juveniles of some species of damselfish clean other fishes. Certain groups of damselfish are not territorial; midwater plankton-feeders may have shelter for retreat or spawning but do not maintain permanent territories, and anemones provide a built-in defense for areas occupied by anemonefishes (Amphiprion and Premnas). Anemonefishes, however, may compete for position in the mating dominance hierarchy, and have been observed striking each other with the pectoral fins. In the anemonefish genus Amphiprion each group contains a male/female pair whose behavioral dominance suppresses the sexual maturation of the smaller males. If one of the dominant fishes dies, the next fish in the hierarchy takes its place (see Reproduction: Mating Systems). (Allen, 1998; Helfman, Collete, and Facey, 1997; Moyle and Cech, 2000; Peterson and Warner, 2002)
Anemonefishes, comprised by the genera Amphiprion and Premnas, have a highly evolved relationship with sea anemones. They remain undisturbed by contact with anemone tentacles that would be fatal to other small fish. A mucous secretion is thought to protect them from the stinging nematocysts. While anemonefishes receive protection living in close proximity with their hosts, the anemones benefit as well. The fish clean the anemone’s upper surface, remove parasites, drop food on the anemone, and chase away butterflyfishes that eat anemones. Waste excretions from the fish may also help symbiotic algae within the anemone to grow. Anemonefishes spend their entire adult lives with a single host. (Allen, 1998; Helfman, Collete, and Facey, 1997)
Key behaviors:
natatorial ; diurnal ; motile ; territorial ; social ; dominance hierarchies .
Communication and Perception
Damselfishes (Pomacentridae) use a variety of visual, olfactory, tactile, and auditory cues to communicate in different situations. During courtship damselfishes respond to the sight of spawning colors and ritualized movements performed by a potential mate (see Reproduction: Mating Systems). Such movements may also signal the location of territory to other males or encourage reproductive synchrony. Anemonefishes (Amphiprion and Premnas) appear to use perception of individual color differences to recognize their monogamous partner. In addition to visual cues, male damselfishes use sound to ward off other males and sometimes as part of courtship and spawning rituals. They may touch and nip females to guide them toward a nest. Chemical cues from some damselfishes may encourage conspecific (individuals of the same species) juveniles to establish nearby territories and may discourage other groups of damselfish from settling. Young anemonefishes use visual and chemical cues when choosing a preferred species of anemone as host. (Helfman, Collete, and Facey, 1997; Myrberg and Fuiman, 2002; Thresher, 1984)
Food Habits
Bottom-dwelling damselfishes feed, for the most part, on algae and small invertebrates. They may tend “gardens” of filamentous algae, or in the case of anemonefishes, feed on the anemone itself or other organisms that are commensal with the anemone. One species of damselfish, Cheiloprion labiatus, or largelipped puller, eats the polyps of live coral. Damselfishes that live in the water column tend to feed on plankton and zooplankton. (Allen, 1998; Böhlke and Chaplin, 1994; Froese, Pauly, and Woodland, 2003; Helfman, Collete, and Facey, 1997; Moyle and Cech, 2000)
Primary Diet:
carnivore (eats non-insect arthropods); herbivore ; omnivore ; planktivore .
Predation
Reef damselfishes gain protection from predators by hiding in coral shelters, anemonefishes by living in close contact with a host anemone, and the free-swimming damselfishes by schooling. Each group’s method of protecting itself applies to its eggs as well, except for midwater damselfishes, which must establish temporary shelter for spawning and egg laying. (Helfman, Collete, and Facey, 1997; Hixon and Webster, 2002)
Ecosystem Roles
Damselfishes are numerous and common on tropical reefs, and as such are an established element of those habitats. Many of them affect the growth of algae on the reef, encouraging algal growth in some areas while using the algae as a food source. The anemonefishes provide some protection and bring in sources of nourishment for their anemone hosts, and some groups of juvenile damselfishes clean other fishes. (Böhlke and Chaplin, 1994; Helfman, Collete, and Facey, 1997)
Economic Importance for Humans: Negative
No specific information was found concerning any negative impacts to humans.
Economic Importance for Humans: Positive
Many damselfishes are brilliantly colored and are popular aquarium fish. In aquarium settings they can be aggressive, but are extremely hardy. In some areas bordering the Indian Ocean people eat damselfishes that they catch in traps or with hooks, but in general pomacentrids are not used for food. (Allen, 1998; Böhlke and Chaplin, 1994; Froese, Pauly, and Woodland, 2003; Hoese and Moore, 1998; Wheeler, 1985)
Conservation
Three pomacentrid species, Chromis sanctaehelenae, Stegastes sanctaehelenae, and Stegastes sanctipauli, are listed as vulnerable. (The World Conservation Union, 2002)
Contributors
Monica Weinheimer (author), Animal Diversity Web.
