Hydroids (Cnidaria, Hydrozoa) of the Danish expedition to

HYDROIDS OF THE DANISH EXPEDITION TO THE KEI ISLANDS
Lateral nematothecae tubular, distal half extending
beyond hydrotheca, bent at level of
hydrothecal margin, upper part upright, lower,
adnate part oblique, one circular terminal opening,
inner wall with either a deep, drop-shaped
emargination or a similarly shaped hole (Fig.
74E). Median inferior nematotheca below hydrotheca
and just reaching somewhat beyond its
bottom, tubular, straight, lower half adnate, free
part gutter-like.
Gonothecae borne on modified hydrocladia
(gonocladia) branching off from ordinary hydrocladia,
branching point near base of a hydrotheca.
Gonocladia unpaired, straight, closely resembling
ordinary hydrocladia, with a few segments
bearing a hydrotheca and nematothecae,
these segments thus identical to the ones of ordinary
hydrocladia, intercalated between them 2–3
internodes bearing a gonotheca, each internode
with 2–3 nematothecae, nematothecae these internodes
in one median row, thus not paired,
resembling median inferior nematothecae. Gonocladium
with regular internal ribs.
Observed gonothecae all at beginning of development
only, funnel-shaped, circular crosssection.
Etymology
The name keiensis refers to the type locality in the
channel between the two main islands of the Kei
Archipelago.
Remarks
Cladocarpus keiensis resembles Cladocarpus
sibogae, the type locality of which is only 8–9
nautical miles distant. They differ, however, in
a number of independent details. Cladocarpus
sibogae has median inferior and lateral nematothecae
with slit-like openings which are not
gutter-shaped or tubular (see Ramil & Vervoort
1992: fig. 27f), the hydrothecal margin is undulated,
it lacks the large intrathecal septum and
the looped ridge, the gonocladium has no interspersed
segments with hydrothecae, and the nematothecae
of the gonocladium are in two rows.
Further differences are found in the unbranched
stem and the generally larger dimensions of internode
length and hydrotheca size. Cladocarpus
multiseptata Bale, 1915, is also similar but this
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species has gonocladia with nematothecae in two
rows and without hydrothecae. There are more
such similar species and their differences are
discussed in Vervoort (1966), Rees & Vervoort
(1987), Ramil & Vervoort (1992), and Ansín
Agís et al. (2001). Cladocarpus keiensis differs
from all of them by its peculiar gonocladium and
the intrathecal septum continued as a looped
ridge.
The gonocladium (phylactocarp) of Cladocarpus
keiensis with its interspersed hydrothecate
elements immediately suggests its origin
from an ordinary hydrocladium and could represent
the least derived phylactocarp morphology
found in this genus. The gonothecae of the type
specimen were all juvenile, but clearly recognizable
as incipient gonothecae (Fig. 74F).
Distribution
Only known from the type locality: Kei Islands
Expedition station 24, 5.62°S, 132.93°E, 100 m.
Lytocarpia angulosa (Lamarck, 1816)
Fig. 75.
Plumularia angulosa Lamarck, 1816: 126.
Aglaophenia angulosa Lamouroux, 1816: 166.
Plumularia Huxleyi Busk, 1852: 395.
Acanthocladium Huxleyi. – Allman 1883: 33, pls 9 & 20:
figs 1–3.
Aglaophenia Huxleyi. – Bale 1884: 161, pl. 15: fig. 6, pl. 17:
fig. 8.
Thecocarpus angulosus. – Billard 1907: 326, fig. 2, revision.
– Billard 1913: 85, figs 70–74.
Acanthocladium studeri Weltner, 1900: 588, pl. 46: figs 4–
7.
Acanthocladium angulosum. – Stechow & Müller 1923:
478.
Lytocarpia angulosa. – Watson 2000: 64, fig. 51A–G.
Material examined:
Kei Islands Expedition stations: 15, with gonothecae. – 16. –
18. – 21. – 24. – 26. – 30, with gonothecae. – 37. – 53.
Description
Colonies forming single stems, rooted in sediment
by tangled mass of fibre-like stolons, stem
height reaching 60 cm and more, flexible, limp
when out of water, polysiphonic, furnished all
around with helically arranged pinnate sidebranches.
Stem only occasionally with hydrocladia
arising from a primary tube, hydrocladia