THE STEINHART AQUARIUM - Gulf of Guinea Science ...

greenish, or yellowish. Conical protuberances
over the entire colony’s surface. Tentacles
often partially extended during the day.
Diet: Nutrition mostly provided by symbiotic
zooxanthellae, but also take other food
sources, such as plankton
Reproduction: Hermaphroditic, probably
broadcast spawners.
Remarks: Hydnophora rigida is by far the most
common species of the genus.
Hydnophora aka Horn Coral
Hydnophora rigida (Merulinidae)
Distribution: Widely distributed in the Indo-
Pacific.
Habitat: Common in variety of reef habitats.
Often found in lagoons or on protected reef
slopes.
Appearance: Colonies may be massive,
encrusting, or branched; usually cream
or green. Conical protuberances, called
hydnophores, cover the entire colony’s
surface, and are formed where adjacent
corallite walls meet and fuse. Hydnophora
rigida is by far the most common species of
the genus. Though usually branched and
often found in brown and bright to fluorescent
green, the species in captivity may form large,
encrusting colonies of more neutral shades.
Diet: Nutrition mostly provided by symbiotic
zooxanthellae, but also capture plankton and
absorb dissolved matter. In captivity, feeding
tentacles are often partially extended during
the day.
R e p r o d u c t i o n a n d D e v e l o p m e n t :
Hermaphroditic broadcast spawner.
Remarks: Hydnophora species are aggressive,
extending stinging sweeper tentacles and
mesentarial filaments, and usually winning
encounters with other corals.
Trumpet Coral
Caulastrea sp. (Faviidae)
Distribution: Indo-Pacific.
Habitat: Prefer sandy substrate at shallow
to mid depths in areas protected from heavy
wave action.
Appearance: Plump, circular polyps cluster on
branched stalks. Septa of skeleton are distinct
and usually visible through the polyp tissue.
Diet: Rely on products of photosynthetic
California Academy of Sciences
41
zooxanthellae as well as microplankton.
R e p r o d u c t i o n a n d D e v e l o p m e n t :
Hermaphroditic broadcast spawners in the
wild; also propagate asexually in the wild and
in captivity by fragmentation and budding.
Remarks: One of many corals that extend
long sweeper tentacles as a defense against
encroachment by other coral colonies. The
tentacles nematocysts can damage tissue of
corals that venture too close.
Caulastrea species are a favorite of aquarists
for their success in captivity and ease of
propagation.
The branches below the polyps offer refuge
to commensal sponges, mollusks, and other
invertebrates, including other small coral
species.
Diploastrea Coral
Diploastrea heliopora (Faviidae)
Distribution: Red Sea and east Africa; Indo-
West Pacific.
Habitat: Occasional on most reefs, especially
upper slopes or in areas exposed to swell or
currents.
Appearance: Colonies are dome-shaped and
may grow very large, up to 2 m high and 5 m
across. Individual polyp skeletons (corallites) are
mound-like and densely situated on the colony’s
surface. Usually cream or grey, sometimes
greenish. Color morphs, such a bright green
corallites with purple center, are common.
Diet: Nutrition from zooxanthellae; feeding
tentacles extended at night.
Remarks: Very dense skeleton discourages
boring organisms.
Their skeletal density, slow growth, long
lifespan (up to 700 years, perhaps longer),
and wide distribution have made Diploastrea
useful for climate change studies. Oxygen
isotopic profiles from skeletons have tracked
variations in sea surface temperature to the
fineness of seasons and decades, providing
useful information about paleoclimate in the
tropical Indo-Pacific.
D. heliopora is the single species in the genus.
Brain Coral
Diploria sp. (Faviidae)
Distribution: Endemic to the tropical Atlantic-
Caribbean.