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The soft coral genus Dendronephthya Kükenthal 1905
(Octocorallia): Inventory and investigations of type material in
German museum collections
Lars Jürgens & Götz B. Reinicke
German Oceanographic Museum, Stralsund
Introduction
Historical remarks
The species of the azooxanthellate soft coral genus Dendronephthya
are distributed throughout tropical coastal waters of the Indopazific
Ocean. The genus was described by Kükenthal (1905) and 248
described species are known today. The colonies are branched and
grow up to sizes over 1 m in height. On the end of the branches the
polyps are united in bundles. The colourful species of Dendronephthya
are well-known from underwater photography because the colonies
usually develop yellow or red coloured sclerites, which shimmer
through the tissues. 112 type specimens were exanimated in German
scientific museum collections in Jena (PMJ), Frankfurt (SMF), Berlin
(ZMB), Hamburg (ZMH) and Munich (ZSM) during in subproject “GBIFD Cnidaria” and data were provided for the GBIF internet platform.
Kükenthal (1905) divided the genus Spongodes Lesson 1834 into two new genera Dendronephthya (87
species, including 28 new) and Stereonephthya (8 species, including two new). To Dendronephthya he
referred all former Spongodes species with polyps arranged in bundles. Shortly after, many authors described
new Dendronephthya species. Henderson (1909) published 53 new species. His study was based on material
from the Royal Indian Marine Survey Ship “Investigator”, collected from various Indian Ocean locations.
Today this material is located in the Indian Museum in Calcutta. Sherriffs (1922) defined a formula to
characterise the anthocodial armature, that has since been used by taxonomist until today (Fig. 4). In the
latest revision Tixier-Durivault & Prevorsek (1959, 1960 and 1962) divided the genus Dendronephthya into the
genera Spongodes, Roxasia and Morchellana. However, their system was not adopted by other colleagues
(e.g. Utinomi 1962, Verseveldt 1966) because of the large similarity of the “genera” and wide variability of
species. Today the categories are used as subgenera. The first and only systematic study based on
molecular methods so far was published by Song & Lee (2000) covering 7 species from the Northern Pacific.
Fig. 1: type specimen of Dendronephthya mucronata (Pütter 1900) with
glomerate growth form (left); drawing a glomerate colony (Bayer et al.
1983) (right).
Fig. 2: type specimen of Dendronephthya speciosa Kükenthal 1905 with
divaricate growth form (left); drawing a divaricate colony (Bayer et al. 1983)
(right).
Fig. 3: type specimen of Dendronephthya florida (Esper 1791) with umbellate growth
form; drawing a umbellate colony (Bayer et al. 1983) (right).
Systematic remarks
Results of type investigations (GBIF)
Kükenthal classified the Dendronephthya species into three groups on the
basis of the colony morphology: Glomeratae, Divaricatae and Umbellatae
(Fig. 1-3). Today this classification is reflected by the subgenera
Dendronephthya, Roxasia and Morchellana. Some species of the genus
Dendronephthya colony forms showing characters transitions between typical
forms of the subgenera (Kükenthal 1905, Sherriffs 1921, Song & Lee 2000).
Because of these transitions some authors discussed possible hybridizations
(Thomson & Dean 1931, Lee & Song 2000). MacFadden & Hutchinson (2004)
demonstrated hybridization for other soft corals (Alcyoniidae), based on
molecular data. Another possible explanation of the transitions between
some described “species” could be that specimens belong to polymorphic
species. A study of population structures of the Dendronephthya species and
their phylogenetic relationships does not exist until today.
Within the scope of the GBIF-D subproject Cnidaria the type material of 58 Dendronephthya species
was included. Often the described specimens had been dissipated by the author and fragments were
dispatched to colleagues in charge of other collections. On the one hand this practice reduced losses,
but on the other hand it complicates the identification and investigation of the type material today. In
some collections only fragments of colonies exist. Therefore it is more difficult to review and describe
the variability of the characters. For some taxa the variability of the important characters was prove,
like the specification of anthocodial armatures or bundles of polyps. For example, regarding the type of
Dendronephthya savignyi (Ehrenberg 1834) some characters resemble those of the genus
Stereonephthya (Fig. 5, 6). In the type colony, some polyps are standing isolated, not being united in
bundles. The tubercles of the supporting bundles sclerites of this colony are formed with an orientation
towards the distal end. But the general colony morphology of the type is more similar to the habitus of
Dendronephthya species. Because of the variability of the characters , it seems necessary to search
for new characteristics, e.g. molecular data.
Fig. 4: Diagram of anthocodial armature of
Dendronephthya flammea Sherriffs, after
Tixier-Durivault & Prevorsek (1960); with
different sclerite types.
Fig. 5: Holotype of Dendronephthya savignyi (Ehrenberg 1834);
left the colony, right a Polyp detail showing anthocodial armature.
Fig. 6: anthodial armature of Dendronephthya savignyi after Tixier-Durivault &
Prevorsek (1959).
Outlook
Acknowledgement
To resolve the problems in taxonomy and classification of the various
Dendronephthya species, investigations of the population structures are needed.
For such studies it is necessary to use a combination of traditional morphological
with modern methods, to facilitate the comparison to the older studies and
descriptions. Due to the large distribution area of Dendronephthya and the high
number of species a review project covering the entire taxon is unrealistic.
An investigation of Dendronephthya species distributed in the Red Sea would be
a suitable starting point. 29 species are scientifically proven in the Red Sea
(Benayahu 1985), of which 10 species are commonly distributed and some settle
in deeper water. It is planned to collect samples on different locations along the
Sinai coast by a diver crew. Mitochondrion and nuclear sequences will be
analysed of the sampled colonies in combination of morphological characters. A
small field study for preliminary investigations was carried out in the Dahab
region, Sinai peninsula (Egypt), in autumn 2005.
The authors gratefully acknowledge the
support of the project cooperating
colleagues C. Lüter (ZMB, Berlin), D. von
Knorre (PMJ, Jena), B. Ruthensteiner
(ZSM, Munich), H. Ruhberg (ZMH,
Hamburg) hosting our work. BMBF (FKZ
01LI0206) facilitated the study through the
mediation of M. Türkay, coordinating the
Marine Invertebrates III–node at the
Senckenberg Museum (Frankfurt) and
providing the SESAM database platform
(Fig. 7). We wish to thank also L. van
Ofwegen (NMNH, Leiden) for extended
discussions.
Fig. 7: screen shot of Dendronephthya speciosa data set in SESAM.
References
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