Heteractis aurora (Quoy & Gaimard, 1883)

Titus, Benjamin M., Bennett-Smith, Morgan F., Chiodo, Tommaso & Rodríguez, Estefanía, 2024, The clownfish-hosting sea anemones (Anthozoa: Actiniaria): updated nomenclature, biogeography, and practical field guide., Zootaxa 5506 (1), pp. 1-34 : 15

Heteractis aurora (Quoy & Gaimard, 1883) ( Figure 4 ; Figure S2 )

Heteractis aurora , commonly referred to as the “beaded anemone”, is a highly distinctive clownfish-hosting species and sole member of the family Heteractidae ( Figure 4 , Figure S2 ). Tentacles (50-60 mm in length) often have characteristic swellings at regular intervals along the tentacle and take on a resulting “beaded” appearance that make this species impossible to misidentify in the field when present ( Figure 4A, B, D ). The base body and tentacle color of this species is often variable whites/browns/beiges but can take on purplish or greenish hues as well ( Figure 4 , Figure S2 ). This is a small to medium sized host anemone, with a broadly flared oral disc (up to 300 mm in diameter) that lays flat or undulating over sandy or rubbly substrate ( Figure 4 , Figure S2 ). Tentacles sparse, leaving oral disc and mouth highly visible. Oral disc can take on a “zebra” stripe pattern similar to that of Radianthus doreensis . Verrucae on the column of this species are lighter in color than the surrounding column and extend from the oral disc downward to mid-column ( Figure 4C ). Verrucae often hold debris such as sand, shell, or other loose rubble ( Figure 4C ). The lower column, typically obscured by sediment is often red or orange.

Although the beaded tentacle morphology is diagnostic and not shared by any other host anemone species, some individuals have partially or lightly beaded tentacles, making field identifications difficult in some cases. In some individuals, only the marginal (outer) tentacles are beaded while inner tentacles (those closer to the month) may only be striped with horizontal lines ( Figure 4E ). In other cases, the “beads” may only occur on one side of the tentacle, or may take on a more swollen bulging appearance rather than well-defined beads ( Figure 4E , Figure S2E ). These partially beaded individuals are particularly common in the Red Sea and other parts of the Indian Ocean, with the exception of the Maldives which harbor individuals with well-defined beads. Individuals with partially or lightly beaded tentacles can easily be misidentified as Radianthus crispa or Radianthus doreensis due to similar microhabitats. Radianthus crispa typically has longer tentacles than H. aurora and harbors verrucae that are similarly colored to the surrounding column, while R. doreensis also has longer tentacles but these form spiral patterns.

The geographic range of H. aurora is extensive, from the Northern Red Sea throughout the Indian Ocean, and into the Central Pacific to the Marshall Islands and Fiji ( Figure 5 ). This species is a sand/rubble dwelling anemone that occupies sand pockets in coral reef habitats, or occupies sand flats adjacent to reefs. It is only known to reproduce sexually and does not form large aggregations.

Figures

FIGURE 2. Representative images of the bubble-tip sea anemone Entacmaea quadricolor encompassing a broad range of geographic and phenotypic variation. A) Wide angle photograph of large solitary individual highlighting typical microhabitat requirements for the species. Note the tentacles are both bulbous and digitiform within this individual (Saudi Arabia, Red Sea). B) Dense aggregation of hundreds of small clonal sea anemones growing among a shallow branching stony coral serving as hosts to a colony of Amphiprion melanopus (Kwajalein Atoll, Marshall Islands). C) Macro photograph of characteristic bubble tips. Note the striated pattern of the tentacle (Fares-Maathodaa, Maldives). D) Individual anemone with all tentacles exhibiting characteristic bulbous tentacle morphology (Fares-Maathodaa, Maldives). E) Red solitary individual with long digitiform tentacles hosting (Saudi Arabia, Red Sea). Photographs by Morgan Bennett-Smith, Benjamin M. Titus, and Scott Johnson.

FIGURE 4. Representative images of the beaded sea anemone Heteractis aurora encompassing a broad range of geographic and phenotypic variation. A) Multi-colored, whole individual in typical rubble microhabitat with characteristic beaded tentacle morphology (Maldives) B) Macro photograph of stereotypical beaded tentacle morphology (Kwajalein Atoll, Marshall Islands). C) Partially retracted/folded oral disc revealing highly contrasting white verrucae on gray column (arrow). Also note zebrastriped oral disc pattern (Fares-Maathodaa, Maldives). D) White phenotype hosting Amphiprion clarki (Fares-Maathodaa, Maldives). E) Individual with partially beaded tentacles. White peripheral tentacles with lightly beaded morphology with inner brown tentacles without beads and horizontal stripes (Anilao, Philippines). Photographs by Morgan Bennett-Smith, Benjamin M. Titus, and Scott Johnson.

FIGURE 5. Confirmed geographic range of Heteractis aurora in the Indo-West Pacific. Red dots represent species observations from the Global Biodiversity Information Facility (GBIF). Blue shaded area represents shallow water habitat (60 m bathymetry).