Serpent Coral

Overview

The Serpent Coral (Pachyseris speciosa) is a widespread hard coral known for its distinctive, plate-like colonies that often resemble stacked layers or a "castle" of plates. It is a common species across the Indo-Pacific, frequently found on reef slopes where it can form extensive, impressive structures.

Distribution & habitat

This species is found throughout the tropical Indo-Pacific, ranging from the Red Sea and East Africa to French Polynesia and as far north as Japan. While it inhabits a variety of reef environments, it is most commonly encountered on lower reef slopes. It thrives in both shallow waters and deeper, mesophotic zones, sometimes forming vast, continuous fields in darker, deeper areas.

Appearance

Pachyseris speciosa typically forms unifacial, laminar colonies, meaning polyps are present on only one side of the plate. The surface is characterized by unmistakable, prominent concentric ridges that run parallel to the colony's edge. These ridges are separated by narrow valleys where the polyps reside, though the polyps themselves are rarely seen extended. Colonies are generally shades of pale brown, grey, or yellow, often featuring lighter-colored margins.

Biology & behavior

The height of the coral's characteristic ridges can vary based on local water flow; in more exposed, high-flow environments, these ridges tend to be more developed. The species maintains a symbiotic relationship with photosynthetic algae (Symbiodiniaceae), which provide essential nutrients. Research indicates that colonies living in deeper, mesophotic waters may exhibit higher heat tolerance than their shallow-water counterparts, potentially due to differences in their symbiotic algal communities.