Wm. Goldberg et Gt. Taylor, ULTRASTRUCTURE OF THE SPIROCYST TUBULE IN BLACK CORALS (COELENTERATA,ANTIPATHARIA) AND ITS TAXONOMIC IMPLICATIONS, Marine Biology, 125(4), 1996, pp. 655-662
Spirocyst tubules in five shallow-water antipatharian species Antipath
es pennacea, Antipathes sp. cf. salix, A. fiordensis, A. galapagensis,
and Cirrhipathes luetkeni) contain an electron-opaque, helically arra
nged structure, composed of four distinct and separate bundles of micr
ofibril-like material. Each bundle appears to be solid, rather than ho
llow, and is enveloped by a sheath of lesser electron-opacity that is
continuous with the pleats. Tubules from a more distantly related, dee
p-water antipatharian, are similarly configured but are composed of on
ly three distinct bundles, separated from one another by electron-opaq
ue sheath material. The bundles are electron-lucent; their substructur
e was not preserved because this specimen was prepared for microscopy
after preservation in alcohol for 27 yr, apparently without initial fi
xation. Most other details of the spirocyst tubule and capsule can be
determined from this museum specimen. The arrangement within the tubul
e of multiple bundles, clearly defined by sheaths, is structurally dis
tinct from other zoantharian spirocysts, and appears to be unique to t
he Antipatharia. The tubule structure of the anemone Aiptasia sp., exa
mined for comparison, is consistent with that of spirocysts from other
actiniarians and zoantharians generally, including the appearance of
electron-opaque rodlets within the tubule lumen. No substructural info
rmation was obtained from Aiptasia sp. rodlets. It is unclear whether
the microfibrillar bundles of antipatharian spirocysts differ from tho
se of other zoantharians by being more amenable to resolution, or if t
heir tubule substructure is fundamentally distinct from those of more
typical zoantharians. In terms of overall structure, Aiptasia sp. spir
ocyst tubules contain a single bundle of rodlets without a clearly def
ined sheath, in contrast to antipatharians which have three or four bu
ndles, each clearly defined. These structural differences may be usefu
l in determining relationships both within the Antipatharia, and betwe
en antipatharians and allied orders.