Common Name: Pulse corals, Pumping Xenia, Pump-end Xenia, Waving hand Polyps
Colour: White, gray, brown. Rarely green or blue.
Distinguishing Characteristics: Encrusting or stalked, the monomorphic polyps are non-retractile. Colonies are usually quite soft, but larger, stalked varieties may be tougher. In some species, the colonies are very slimy (e.g. X. cf. mucosa) and can produce lots of m u c us (G o s 1 i ner et a1, 1996)! Xen ia u m belta ta is an uncommon and very welcome guest to aquariums, with large, pulsing polyps. The color and form of Xenia species is highly dependent on environmental conditions, making visual ID difficult. Sclerites are minute platelets (Bayer, 1973).
Similar Species: The closely related genus Heteroxenia is distinguished by having dimorphic polyps (two types: siphonozooids between the autozooids, as in Sarcophyton and Lobopbytum), compared to Xen ids monomorphic polyps. Also similar to Anthelia, but Xenia generally forms stalks while Anthelia forms creeping mats. However there are Anthelia species in which the mats divide into distinct clumps of polyps (i.e. see photo of Anthelia cf philippinensis) and there are encrusting Xenia spp. that don't have an obvious stalk (see photo). Anthelia polyps generally open flat in still water, whereas Xenia polyps have tentacles that curve inward toward the center of the polyp, and generally finer pinnules.
Natural Habitat: Xenia and Heteroxenia spp. can be found in a variety of reef habitats, from brightly illuminated reef flats where they may be exposed at low7 tide to reef slopes where the light is bright but more indirect. There are also species that live in lagoon environments. Where they occur they generally are exposed to strong tidal currents for a portion of the day.
Aquarium Care: Xenia species like bright light and intermittent strong currents, with periods of little current. They also adapt to mild constant flow. They prefer high pH, and some species show rapid growth with the additions of kalkwasser and trace elements.
A colony of Xenia sp. with Anthelia cf. glauca behind it. J. C. Delbeek
This encrusting Xenia sp. has a stalk so low and broad it resembles a creeping mat. J. C. Delbeek
This encrusting Anthelia cf glauca has very fluid polyps that "blow" in the currents. Compare its appearance to the adjacent Xenia sp. and similar Clavularia spp. J. C. Delbeek
This "Pom-Pom" Xenia sp. has polyps quite similar to Anthelia, but the stalk clearly shows it is not Anthelia. It may be a juvenile Heteroxenia sp. that has not yet developed siphonozooids. J. C. Delbeek
A common and hardy Xenia species from Indonesia. It grows very quickly and exhibits very nice rhythmic pumping when healthy. S. W. Michael
particularly iodide and iron. Sometimes colonies will "crash" after many months of vigorous growth and asexual division. It is believed that depletion of trace elements may play a role in such crashes, as is common in marine algae. Sexual reproduction in some species, evidenced by the release of gametes, may be followed by colony death. Protozoans also may attack colonies and rapidly consume them. Beware that fish and crabs may also
This extremely large Xenia sp. is one of the most lovely but, unlike the other species, it is most difficult to keep, see comments in the text. J. C. Delbeek
eat Xenia. Xenia colonies become flaccid and unhealthy looking when the pH falls below 8.1 for extended periods of time. They are most vigorous at a pH of 8.3 or higher. The pumping becomes
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