Hydroids (Cnidaria, Hydrozoa) of the Danish expedition to

154
As indicated above, the genus Mitrocomium
(as defined in Brinckmann (1959) based on Haleciella
microtheca) presents considerable problems
not only at the species level, but also at the
family level. Its hydroids have a hydrotheca that
associates them with the genus Halecium, while
their medusae belong to the Lovenellidae (sensu
Russell). Where known, the hydroids of the family
Lovenellidae Russell, 1953 are quite disparate,
some like Eucheilota maculata being of a
campanulid type (Werner 1968), while others
are lovenellid with demarcated opercular valves
(e.g., Lovenella clausa, see Russell 1953 or
Cornelius 1995a). To account for this, Bouillon
(1984a, 1985a) placed the genera Eucheilota
and Lovenella in families of their own and dismissed
the life cycle of M. cirrata as insufficiently
known. By this, however, the problem is
not entirely solved and systems based on the
medusa stage and the hydroid stage are still incongruent
(see also Cornelius 1995a: 154, who
expresses a similar opinion). I consider that
Mitrocomium, and also the genus Hydranthea
(see Boero & Sarà 1987), do not belong to the
Haleciidae but are more closely related to the
genera Lovenella and Eucheilota, both belonging
to the family Lovenellidae Russell, 1953 (not
Bouillon). The positive characters of an intratentacular
web in the hydroid as well as the lateral
cirri of the medusa appear to me as more convincing
synapomorphies than the reduced, Haleciumlike
hydrotheca. If one considers that the hydrotheca
in Eucheilota species can be partially
lost, resulting in hydrothecae strongly resembling
the ones of Halecium (see fig. 14c in Werner
1968), then the usefulness of the shape of the
hydrotheca for delimiting families is severely
undermined. Such macrotaxonomic problems
can only be solved in the framework of a comprehensive
phylogenetic analysis and Mitrocomium
is presently not removed from the Haleciidae
as it would cause a major taxonomic instability
of this family.
Family Hebellidae
Remarks
As discussed in Schuchert (2001), the members
of the genus Hebella are here placed in the family
P. SCHUCHERT
Hebellidae Fraser, 1912 and not the Lafoeidae.
The species belonging to the Hebellidae have
recently been revised by Boero, Bouillon & Kubota
(1997). This revision clearly showed that the
characters of the hydrotheca alone are mostly
insufficient to distinguish species. Many members
of this family release immature medusae that
must be cultivated to maturity to be identified
properly, but this has been done for a few species
only. Migotto & de Andrade (2000) succeeded in
cultivating the adult medusa of Hebella furax.
It proved to be a Toxorchis sp. (family Laodiceidae).
Other Hebellidae release medusae with
mature gonads or medusoids with gonads on
the manubrium (genus Anthohebella, see Boero,
Bouillon & Kubota 1997). It is thus evident
that Hebellidae species can only be reliably identified
if the mature gonophores are known. We
have here a similar situation as for the various
Campanulina- and Cuspidella-like hydroids (see
also above under Mitrocomium simplex).
In the material examined for this study, hebellid
hydroids were often present on other hydroids,
sometimes even with gonothecae containing
immature medusae. For the reasons given
above, however, they were not identified to species
level.
Family Lafoeidae
Acryptolaria rectangularis (Jarvis, 1922)
Fig. 13.
Cryptolaria rectangularis Jarvis, 1922: 335, pl. 24: fig. 3.
Cryptolaria bulbosa Stechow, 1932: 87.
Acryptolaria rectangularis. – Millard 1975: 171, fig. 57A–
D. – Gravier-Bonnet 1979: 17, fig. 4A. – Millard 1980:
138, fig. 4A.
Acryptolaria angulata. – Vervoort 1966: 116, fig. 16. –
Hirohito 1995: 102, fig. 29a–b, pl. 6: fig. B.
Material examined:
Kei Islands Expedition station 3, at least two stems and
fragments.
Description
Colonies erect, up to 4 cm high, irregularly
branched, branching primarily in one plane.
Stem and branches polysiphonic through auxiliary
tubes covering the hydrotheca-bearing primary
tube, polysiphonic parts thinning distally,