Euphylliidae

Lore & Background

Euphylliidae are known as a family of polyped stony corals under the order Scleractinia. As of the year 2000, the order Scleractinia was divided into 18 artificial families, including Euphyllidae, but by 2022 more than 30 families were determined. Various genera are listed by the World Register of Marine Species, including Euphyllia, Fimbriaphyllia, Galaxea, and others; Acrhelia and Acrohelia are considered synonyms of Galaxea, while Leptosmilia is considered a synonym of Euphyllia. These corals typically have a phaceloid growth form and are green, gray, bluish, or pale-brown in color. Their tentacles have greenish to cream tips that are round, kidney to bean-shaped. Corallites are very tall (up to 150 mm) and either single or in rows, rising separately from encrusting leaves. Septa are numerous and in cycles, with smooth or finely granulated margins. There is no columella. The most conspicuous genera are Plerogyra and Euphyllia, commonly referred to as 'bubble' or 'grape' corals due to their large fleshy tentacles expanded during the day. Euphylliidae are benthic and sessile organisms, found in shallow waters. They are photosymbiotic and known as suspension feeders, feeding through stinging structures called nematocysts. Their conservation status overall is unthreatened, but specific species are of higher concern due to environmental issues such as increased sea surface temperature, ocean acidification, and overfishing for the marine aquarium trade.

Reader's Guide

Euphylliidae are notable as a family of stony corals commonly kept in home-aquariums, where they are enjoyed for their beauty and the protection they provide to fish. The family includes genera such as Euphyllia and Plerogyra, which are among the most conspicuous and are often called 'bubble' or 'grape' corals because of their bubble-like appearance during the day. These corals are found in the Indo-Pacific, Australia, Southeast Asia, the Ryukyu Islands and East China Sea, the Solomon Islands, Fiji, and Palau, typically on fringing reef crests, mid-slope terraces, and lagoons at depths of 2 to 25 meters.

Their body structure is characterized by an endoskeleton of calcareous aragonite, and colonies are phaceloid, meandroid, or flabello-meandroid. While most hard corals are identified by their skeleton, members of Euphylliidae are more easily told apart by the structure of their tentacles, with some species having a distinctive U-shaped tip. The family reproduces both asexually and sexually; about three-quarters of stony corals produce gametes, and most are broadcast spawners. Planulae exhibit positive phototaxis and typically settle within two days, though some may swim for up to three weeks or even two months. The current conservation status of the family overall is unthreatened, but specific species face threats from environmental changes and the marine aquarium trade.

Did You Know?

• Members of this family are more easily identified by the structure of their tentacles than by their skeleton.
• Some species have tentacles with a distinctive U-shaped tip, while others lack this feature.
• Planulae of these corals swim upward toward light (positive phototaxis) and can settle within two days or swim for up to three weeks.