Hydroids (Cnidaria, Hydrozoa) of the Danish expedition to

198
Hydrotheca campanulate, bilaterally symmetric,
straight abcauline side and convex adcauline
side, depth 0.5–0.6 mm, diameter at opening 0.33
mm, lateral wall with distinct transverse corrugation
(about 6 bulges), margin with 4 pointed
cusps and deep, round embayments between
them, operculum pyramidal with four flaps, diaphragm
an oblique perisarcal ring, more developed
on adcauline side. Pedicel of hydrotheca
annulated or not.
Gonothecae absent, according to Gibbons &
Ryland (1989) arising from hydrothecal apophyses,
pedicellate, annulated, usually directed horizontally
and down, not in the same plane as
the remainder hydrothecae; obovoid, truncated
distally; aperture with four cusps and operculum
of four flaps.
Remarks
The corrugated, small hydrothecae distinguish
this species from all other congeners in the Indonesian
region.
Distribution
Eastern Indonesia, Great Barrier Reef, Fiji. Type
locality: Timor.
Family Syntheciidae
Synthecium flabellum Hargitt, 1924
Fig. 52.
Synthecium flabellum Hargitt, 1924: 497, pl. 6: fig: 24. –
Gravier-Bonnet 1979: 41.
Synthecium samauense in part Billard, 1925a: 646, fig. 1A
(not others). – Billard 1925b: 132, fig. 7C–E, pl. 7: fig. 3
(not others).
Sertularia tubitheca. – Pictet 1893: 51–52, pl. 2: figs 44–45.
– von Campenhausen 1896b: 309. [Not Synthecium tubithecum
(Allman, 1877)]
?Synthecium megathecum Billard, 1925a: 648. – Billard
1925b: 130, fig. 6, pl. 7: fig. 2.
Type material examined:
Synthecium flabellum Hargitt, 1924, NMNH reg. number
USNM 42514, in formaldehyde, overgrown by Hebella
spec. – Synthecium samauense Billard, 1925, ZMA number
Coel 3835, Siboga station 60, tube labelled by Billard as
female type, only colonies with gonothecae belong to S.
flabellum, infertile ones are S. samauense.
Other material examined:
ZMA no. Coel 3833, Siboga station 274, identified as S.
P. SCHUCHERT
samauense by Billard, fertile female colonies. – Kei Islands
Expedition, Neira Island, Banda Islands, Indonesia, 10 m,
coll. 5 Jun 1922, few stems on black sponge and hydroids,
with female gonothecae, overgrown by Hebella sp. – MHNG
INVE 32194, as Sertularia tubitheca, Ambon, 16 Aug 1890,
material of Pictet (1893), overgrown by Hebella sp.
Description
Colonies pinnate, 2–4 cm in height. Stolons tubular,
thick. Stems flexible, with opposite pairs of
hydrocladia, 4–6 per side, stem without nodes,
hydrocladia without distinct apophysis, with 2 or
more pairs of opposite hydrothecae between successive
hydrocladia.
Hydrocladia straight, unbranched, some with
terminal tendrils, up to 2.5 cm long, nodes rare,
with two rows of opposite hydrothecae, the pairs
of hydrothecae not contiguous, successive hydrothecae
of one row not in contact and quite
distant, the median planes of the two rows form
an angle < 180°.
Hydrotheca tubular, recurved 60–75°, opening
inclined upwards, abcauline side adnate for 3/
5–2/3 of its length, opening diameter 0.25–0.30
mm (mean 0.27, S.D. 0.017, n = 6, 3 colonies),
length free part of adcauline side 0.25–0.40 mm,
length adnate part 0.57–0.67 mm. Margin of
opening planar or sinuous, slightly everted, often
renovated several times, without operculum.
Only female gonothecae seen, developing
from within stem hydrothecae, 0.9–1.1 mm
long, diameter 0.7–0.8 mm, egg-shaped, with
distal nipple-shaped process, not flattened, walls
smooth; terminal opening small; containing one
egg of 0.5–0.6 mm diameter.
Nematocysts: I, abundant tentacular capsule,
almond-shaped, 5.5 x 1.5 µm, probably a mastigophore.
II, large isorhiza, (40–43) x (10–11)
µm. III, smaller isorhiza 17 x 5 µm.
Remarks
Synthecium flabellum Hargitt, 1924 is a little
known species and Gravier-Bonnet (1979) suggested
that it could be conspecific with S. samauense
Billard, 1925. Re-examination of the
type material of Synthecium flabellum and S.
samauense showed that part of Billard’s type
material of S. samauense indeed belongs to S.
flabellum, while the remainder of the type mate-