Hydnophora sp.
Horn coral, Velvet coral
- Kingdom: Animalia
- Phylum: Cnidaria
- Class: Anthozoa
- Order: Scleractinia
- Family: Merulinidae
Hydnophora is a genus of hard (stony) corals commonly found in the Indo-Pacific region. These corals are well known for their rough, spiky surface formed by cone-shaped projections called hydnophores.
General Description
Hydnophora spp., commonly known as horn corals, belong to the family Merulinidae. They are widely distributed in the Indo-Pacific region, typically inhabiting reef slopes, lagoonal areas, and sheltered reef flats. Colonies are massive to sub-massive, sometimes forming irregular mounds, and are characterized by the presence of numerous conical or knob-like projections (tubercles) on the colony surface, giving the coral a rough and spiny appearance.
The corallites of Hydnophora are small, tubular, and closely spaced, often integrated into the tubercle structures. Septa are well-developed, and the coenosteum between corallites is thick and porous. Colony coloration varies, commonly presenting in shades of brown, green, or cream, sometimes with fluorescent highlights depending on light exposure and symbiont density.
Species-level identification within Hydnophora is challenging due to morphological plasticity influenced by water flow, light, and depth. Accurate identification often requires detailed skeletal examination, including tubercle structure and septal arrangement. Ecologically, Hydnophora corals contribute to reef complexity, providing microhabitats for small reef organisms, and are considered important reef-building corals in the Indo-Pacific.
Key Characteristics
- Forms massive, encrusting, or branching colonies
- Surface covered with sharp bumps or ridges
- Usually green, brown, or cream in color
- Has small polyps that extend mostly at night
Habitat & Distribution
- Found in shallow reef environments
- Common in lagoons and reef slopes
- Distributed across the Indo-Pacific, including Sri Lanka
Nutrition
Like other reef-building corals, Hydnophora:
- Contains symbiotic algae (zooxanthellae) that perform Photosynthesis
- Gains energy from sunlight
- Also captures tiny plankton using tentacles
Special Feature
Hydnophora is considered an aggressive coral:
- It can extend sweeper tentacles
- Capable of stinging and damaging nearby corals
Ecological Importance
- Contributes to reef structure formation
- Provides habitat for small marine organisms
- Plays a role in maintaining coral reef biodiversity
