21 – Octocorals
235
Family Xeniidae. Members of this family often
dominate offshore octocoral communities. Xeniid genera are mostly small and soft, and often quite slippery
to touch. Colony growth forms are lobate, or thin and
membranous with small retractile or tall polyps, or
short, cylindrical stalks terminating with a domed
polyp-bearing region. All species are zooxanthellate,
often with opalescent pastel colours (white, pink, light
iridescent blues and greens); some inshore species are
dark brown. Some species have pulsating polyps,
where the autozooids continually open and close
the tentacle basket. Members of one genus have
siphonozooids at least during some periods of their
lives. Not all of the species in this family have sclerites.
Figure 21.12 Dendronephthya sp. (family Nephtheidae). A, colony; B, some sclerites representative of this genus. (Photo:
K. Fabricius; illustration: P. Alderslade.)
(A)
(B)
0.1 mm
0.2 mm
0.1 mm
0.2 mm
1 mm
1 mm
1 mm
Polyp supporting bundle
Polyp head
Stalk interior
Stalk surface
Branch surface
Tentacle
(A)
(B)
0.1 mm
0.1 mm
0.2 mm
0.2 mm
0.2 mm
Polyp head
Stalk surface
Stalk interior
Branch surface
and interior
Tentacle
Figure 21.13 Lemnalia sp. (family Nephtheidae). A, colony; B, some sclerites representative of this genus. (Photo: K.
Fabricius; illustration: P. Alderslade.)