Thesea nivea Deichmann,
Thesea nivea Deichmann,
1936:122, Plate 7 fig. 7; Plate 11 figs. 16-18.
Remarks. This species branches
more or less in one plane with slender branches that bend upward,
sometimes at an abrupt 90-degree angle. In life, the colony is reddish
violet, with dark red to purple polyps that often have white centers.
Under magnification, the tissue of the polyps and coenenchyme is
violet, but colorless sclerites are visible on the surface of the
stems and at the base and neck of the expanded polyps. When preserved
in alcohol the coenenchyme color is a gray, creamy white or light
brown. The conical calyces are scattered around the branches and
have a visible eight-lobed star. The branches are 3-4 mm in diameter
and tips on some branches are slightly inflated. This species may
be fouled with epibionts such as ascidians and barnacles, and often
has multiple galls per colony that are occupied by invertebrates
such as the spionid worm Polydora sp. and the crab Pilumnus
floridanus (pers. obs.).
Sclerites are colorless and consist of large, warty, acute spindles
and small double heads, and some spiny or warty curved rods. Curved
or arched rods extend into the lower neck of the anthocodia, and
are present as distinct points in the crown, but rarely extend into
the tentacles. The spindles range from 0.3 – 0.5 mm; double
heads, 0.1- 0.2 mm; and the curved rods, 0.3 – 0.6 mm.
Some colonies have a bushy appearance that departs from the typical
one-plane flat growth form, with slightly shorter and more crooked
branchlets. These colonies also have thicker branches up to 5 mm
in diameter, but the sclerite assemblage remains consistent with
the more slender colonies.
Atlantic distribution: North Carolina
to South Carolina, 24-49 m; Dry Tortugas, 71 m; St. Lucia, 371 m;
Guadalupe, 358 m (type) (Deichmann, 1936; NMNH collections; SERTC
Figure 4. Thesea nivea sclerites (USNM 16836):
a) curved rod from anthocodia; b-e) coenenchymal sclerites; b) double
head; e, c) double cones; d-f) spindles. Scale bar = 50 µm.
Note: In addition
to the identified specimens examined, one Thesea specimen
was collected and examined but unidentified. The specimen is approximately
63 cm in height with a lateral branching growth form. All stems
appear to be 1-2 mm in width and gently curving upward from the
main stem. The calices are moderately protruding and domelike with
retractile polyps. The most obvious character about this specimen
is the sclerites, which range from 0.1 mm to over 1 mm in length.
The largest of the sclerites are bluntly elongate to globular deposits
with two distinct sides. The outer side displays undulating, irregular
humps which are quite smooth with the exception of the clusters
of low, fine spines at the apex of each hump. The opposing side,
which tends to face the axis, displays a very coarse texture and
crowded, fine tubercules. The smaller sclerites tend to be concentrated
toward the calices and are warty, elongate spindles with acute tips.
All sclerites are coral red with the exception of the yellow opercular
rods. Although several of the Thesea species in Deichmann
(1936) are described as having large, ridged or undulating outer
sclerites, no mention is made of sclerites with such a contrasting
Figure 1. Colony of Thesea nivea with expanded
polyps, approximately 15 cm length (live specimen, S2695).
Figure 2. Contractile (left) and expanded (right) polyps of Thesea
nivea (live specimen, S2695).
Figure 3. Calyces of Thesea nivea (live