A new species of shallow-water sea pen (Octocorallia: Pennatulacea: Kophobelemnidae) from Antarctica

Abstract

The pennatulacean genus Malacobelemnon has previously been considered to be distributed in the Western Indian and western Pacific Oceans, with one described species
and another possible undescribed species from South Africa. An undescribed shallow-water species attributable to this Kophobelemnidae
genus has been collected from the Antarctic region (King George, South Shetland Islands). The present paper reports this discovery,
providing the description and illustrations of the new species, Malacobelemnon daytoni n. sp. Some of the characters previously considered in the genus Malacobelemnon should be slightly modified to include the new Antarctic species. The general colony shape, the distribution of siphonozooids,
number of longitudinal autozooids rows, and the length and shape of the section of axis are the main characters used to distinguish
the new species from the other in the genus M. stephensoni Tixier-Durivault 1965. From a bathymetric point of view, Malacobelemnon daytoni n. sp. is one of the shallowest pennatulacean species recorded, being an important contribution to the shallow-water Antarctic
fauna.

Full text

Polar Biol (2009) 32:907–914
DOI 10.1007/s00300-009-0591-8
123
ORIGINAL PAPER
A new species of shallow-water sea pen
(Octocorallia: Pennatulacea: Kophobelemnidae)
from Antarctica
Pablo J. López-González · Josep-Maria Gili ·
Verónica Fuentes
Received: 19 November 2008 / Revised: 19 January 2009 / Accepted: 3 February 2009 / Published online: 27 February 2009
© Springer-Verlag 2009
Abstract The pennatulacean genus Malacobelemnon has
previously been considered to be distributed in the Western
Indian and western PaciWc Oceans, with one described spe-
cies and another possible undescribed species from South
Africa. An undescribed shallow-water species attributable
to this Kophobelemnidae genus has been collected from the
Antarctic region (King George, South Shetland Islands).
The present paper reports this discovery, providing the
description and illustrations of the new species, Malacobe-
lemnon daytoni n. sp. Some of the characters previously
considered in the genus Malacobelemnon should be slightly
modiWed to include the new Antarctic species. The general
colony shape, the distribution of siphonozooids, number of
longitudinal autozooids rows, and the length and shape of
the section of axis are the main characters used to distin-
guish the new species from the other in the genus M. ste-
phensoni Tixier-Durivault 1965. From a bathymetric point
of view, Malacobelemnon daytoni n. sp. is one of the shal-
lowest pennatulacean species recorded, being an important
contribution to the shallow-water Antarctic fauna.
Keywords Antarctica · Sea pen · Pennatulacea ·
Octocorallia · Malacobelemnon · New species
Introduction
For many years, during regular diving surveys at Potter
Cove (King George, South Shetland Islands, Antarctica)
carried out by researchers from the Argentinean Polar Base
of Jubany, a delicate shallow-water sea pen has been
recorded and inventoried (Sahade et al. 1998, 2008). Fur-
thermore, a dense population of this pennatulacean species
was also illustrated in naturalist guides oriented to the gen-
eral public interested in the biodiversity of Antarctic under-
water environments (e.g., de la Vega 2000: 47). Thanks to
the friendly collaboration between Argentinean and Spanish
research groups in Antarctic matters, a set of colonies of
this pennatulacean species, collected between 10 and 15 m
depth during the austral summer of 2000, was placed in our
hands for its taxonomic study in April 2002. The Wrst
examination of these colonies identiWed the species as pre-
viously unreported from Antarctic waters. A second set of
colonies collected in February 2005 was available in March
2005. The goal of the present contribution is the description
of these colonies. The material is considered an unde-
scribed species of the kophobelemnid genus Malacobelem-
non Tixier-Durivault 1965.
Materials and methods
The material studied here was collected by SCUBA diving
in Potter Cove, just in front of the Argentinean Polar Base
Jubany, on King George Island (South Shetland Islands),
oV the Antarctic Peninsula (Fig. 1). Potter Cove (62°14⬘S,
P. J. López-González (&)
Biodiversidad y Ecología de Invertebrados Marinos,
Departamento de Fisiología y Zoología, Facultad de Biología,
Universidad de Sevilla, Reina Mercedes 6, 41012 Sevilla, Spain
e-mail: pjlopez@us.es
J.-M. Gili · V. Fuentes
Departamento de Biología Marina y Oceanografía,
Instituto de Ciencias del Mar, CMIMA (CSIC),
Paseo Marítimo de la Barceloneta, 37-49, 08003 Barcelona, Spain
e-mail: gili@cmima.csic.es
V. Fuentes
e-mail: vfuentes@cmima.csic.es

908 Polar Biol (2009) 32:907–914
123
58°38⬘W) is a tributary inlet close to the entrance of
Maxwell Bay, one of the two big fjords of King George
Island. The cove is divided into a mouth and an inner part.
The inner part, where the pennatulids studied here are much
more abundant, has an area of 1.5 km
2
.
The Wrst set of colonies was Wxed in buVered formalde-
hyde (4% in seawater) and then transferred to 70% ethanol.
A second set of colonies was maintained alive in aquaria
provided with an open circuit of seawater for 3 weeks (pre-
sumably colonies feed on suspended particles in the water),
and Wnally Wxed in 96% ethanol. Colony terminology
mainly follows Bayer et al. (1983). The material studied
has been deposited in the Natural History Museum (British
Museum) in London (NHM), in the California Academy of
Sciencies (Invertebrate Zoology collection) in San Fran-
cisco (CASIZ), and in the Anthozoan reference collection
of the research group “Biodiversidad y Ecología de Inverte-
brados Marinos” of the University of Seville (BEIM).
Results
Kophobelemnidae Gray, 1860
Malacobelemnon Tixier-Durivault 1965
Diagnosis (modiWed from Tixier-Durivault 1965:712
and Williams 1995:111)
The colonies are stout and cylindrical to elongated.
Rachis symmetry is bilateral throughout. The axis is short
and present throughout the length of the colony, Xattened,
quadrangular or round and somewhat oval in transverse
section. Polyp leaves are absent. Autozooids are elongated,
free from one another, arranged in longitudinal series and
irregularly disorganized distally. Anthocodia are retractile
into the rachis or into the bulbous Xeshy proximal portions
of polyps. Siphonozooids are sparsely distributed in short
longitudinal or oblique rows on the rachis between auto-
zooids, or grouped on two lateral areas below the lowermost
autozooids. Sclerites are absent except for minute oval bod-
ies in the interior of the peduncle.
Type species
Malacobelemnon stephensoni Tixier-Durivault 1965.
Distribution and depth
Western Indian and western PaciWc Oceans, South Shetland
Islands (Antarctica), 10–60 m in depth.
Malacobelemnon daytoni n. sp
Figs. 2, 3, 4, 5, 6
Material examined
Holotype: NHM (CNEA 2009.1), one complete colony,
Potter Cove, King George Island, South Shetland Islands,
Antarctica, 62°14.08⬘S–58°39.58⬘W, 12 m depth, 26 Feb
2005. Paratypes: NHM (CNEA 2009.2), 1 complete colony;
CASIZ (078428), one complete colony with end bulb
partially dissected, both lots with the same sampling data as
the holotype. Other material: BEIM (CRA-0015), one col-
ony partially dissected, with the same sampling data as the
type material. BEIM (CRA-0016), four colonies, one of
them partially dissected, Potter Cove, King George Island,
South Shetland Islands, Antarctica, 62°14⬘S–58°39⬘W,
10–15 m depth, 20 Jan 1998; NHM (CNEA 2009.3-5),
three colonies, Potter Cove, King George Island, South
Shetland Islands, Antarctica, 62°14⬘S–58°39⬘W, 10–15 m
depth, 20 Jan 1998; CASIZ (078429), three colonies, Potter
Cove, King George Island, South Shetland Islands, Antarctica,
62°14⬘S–58°39⬘W, 10–15 m depth, 20 Jan 1998.
Fig. 1 Map of Antarctica showing the type locality of Malacobelem-
non daytoni sp. nov. in South Shetland Islands area

Polar Biol (2009) 32:907–914 909
123
Description of the holotype
The colony was elongated, slightly clavate, appearing
almost cylindrical, and 86 mm in length. The rachis was
66 mm long (76.7% of colony length) and 4 mm wide at the
widest point. The peduncle was 20 mm long (23.3% of col-
ony length) and 2 mm wide at the widest point (5 mm at the
conspicuous end bulb). Separation between the rachis and
peduncle is considered as the lower limit of the siphonozo-
oid lateral areas. Symmetry of the rachis was bilateral
throughout, with distinct naked dorsal and ventral tracts;
the dorsal was wider, while the ventral one was narrow and
somewhat sinuous distally. Polyps gradually increased in
size along the proximal length of the rachis, making it diY-
cult to delimit young autozooids from developed siphon-
ozooids. Autozooids were numerous, partially retracted,
about 2 mm in length and about 1.5 mm wide. Distally,
they were bilaterally arranged in Wve (six) disorganized
longitudinal rows, much more numerous proximally, with-
out clear diVerences in size from the ventral to the dorsal
side. The anthocodiae were capable of total retraction into
the Xeshy basal part of the polyps (permanent calyces are
not present). The walls of the autozooids were longitudi-
nally grooved with eight intertentacular lines, clearly visi-
ble in the retracted state on the Xeshy basal part of the
retracted polyps distally. Tentacles were not observed in the
holotype by the retraction of the autozooids. In young auto-
zooids, the Xeshy basal parts of the polyps are widely sepa-
rated. With the increase in size of these polyps, these basal
parts come into contact with each other, giving a false
impression of irregular ridges of polyps close to other
polyps, which are completely independent. Siphonozooids
were about 0.15–0.18 mm in diameter, numerous, slightly
elevated from the rachis surface, densely distributed on the
proximal part of the rachis, restricted to two well-delimited
longitudinal lateral areas, and absent among autozooids.
CalciWed axis was present along the entire length of the col-
ony, rounded to oval in cross-section, and 0.55 mm in max-
imum diameter. Sclerites were absent in the entire colony.
Minute ovals (similar to those observed in other pennatula-
cean species) were present in the interior of the peduncle.
Fig. 2 Underwater photograph of a colony of Malacobelemnon day-
toni sp. nov. taken in situ at Potter Cove (King George, South Shetland
Islands, Antarctica). Photo: Guillermo Mercuri
Fig. 3 Malacobelemnon daytoni sp. nov. a General morphology of
four preserved colonies, a holotype NHM (CNEA 2009.1), b paratype
NHM (CNEA 2009.2), c paratype CASIZ (078428), note that end bulb
is partially dissected, d BEIM (CRA-0015). White arrows indicate the
lower limit of siphonozooids patch. b Details of the peduncle–rachis
limit and proximal part of the rachis in one of the colonies photo-
graphed in (a) [BEIM (CRA-0015)], showing the densely placed
siphonozooids area below the autozooids on one of the lateral sides of
the colony

910 Polar Biol (2009) 32:907–914
123
Variations
Preserved colonies ranged from 80 to 125 mm in length.
The rachis was 87 mm long (81% of colony length, based on
six colonies) and 4 mm wide at the widest point. The pedun-
cle was 20.3 mm long (19% of colony length, based on six
colonies) and 2.5 mm wide at the widest point (6 mm at the
conspicuous end bulb). The symmetry of rachis, arrangement
Fig. 4 Malacobelemnon
daytoni sp. nov. SEM photo-
graphs of four sector of a colony.
a Lateral view of peduncle–
rachis limit, with the siphonozo-
oids densely packed. b Lateral
view of the proximal part of the
rachis, just above the area
observed in (a), with increasing
space between polyps (siphon-
ozooids and probably develop-
ing autozooids). c Lateral view
of the proximal part of the
rachis, just above the area
observed in (b), where young
autozooids are presents and
small tentacles can be observed;
see arrowed area. d Lateral
view of the mid-part of the
rachis, where autozooids are
completely developed, some of
them with tentacles partially
extended (see arrowed areas).
Determined areas are labelled
with the number and letter of
Wgures in this paper, where these
sections are shown magniWed
(for example, 5b. This area can
be observed enlarged in Fig. 5b
of this paper)
Fi
g.
5
Ma
l
aco
b
e
l
emnon
d
ay-
toni sp. nov. SEM photographs,
details from sections indicated in
Fig. 4. a Proximal part of the
rachis showing siphonozooids
densely packed (see also
Fig. 4a). b Proximal part of the
rachis where the limit between
siphonozooids and young auto-
zooids are not clear (see also
Fig. 4b). c Proximal part of the
rachis where young autozooids,
one of them with a tentacle
(black arrow), is partially
extended (see also Fig. 4c).
Scale in (a) is valid for all
photographs in this Wgure

Polar Biol (2009) 32:907–914 911
123
of autozooids and siphonozooids, and shape and size of
autozooids and siphonozooids are as described for the holo-
type. Partially retracted polyps show tentacles of 1.7 mm
length in the preserved state, with one row of about 18–20
pinnules on each side, and 0.2 mm in length. The calciWed
axis can reach up to 0.63 mm in maximum diameter.
Colour
Living specimens (Fig. 2) are light brown in the rachis,
with whitish long polyps. Preserved specimens are dirty
white to cream in colour.
Etymology
The name daytoni is chosen in honour of Dr. Paul K. Dayton
(Scripps Institution of Oceanography, La Jolla, USA), in
recognition of his valuable contributions to the knowledge
of Antarctic ecosystems.
Geographic and depth distribution
At present, Malacobelemnon daytoni n. sp. is known only
from Potter Cove (King George Island, South Shetland
Island, oV Antarctic Peninsula; Fig. 1), between 10 and
Fi
g.
6
Ma
l
aco
b
e
l
emnon
d
ay-
toni sp. nov. SEM photographs,
stereo pairs of details from
sections indicated in Fig. 4.
a, b Autozooids from the
distal part of the rachis,
showing partially expanded
crown of tentacles

912 Polar Biol (2009) 32:907–914
123
30 m in depth. This last depth range was observed by
Sahade et al. (1998)(and personal communication).
Ecological remarks
Malacobelemnon daytoni n. sp. is, together with the bivalve
Laternulla elliptica and some ascidian species, one of the
dominant benthic species in the inner area of Potter Cove
(Sahade et al. 1998). The bottom of the inner Potter Cove is
covered by muddy and sandy sediments and is no deeper
than 50 m. This area is actually strongly aVected by sedi-
ment runoV due to glacier retraction (Schloss et al. 2008).
The benthic communities of the inner Potter Cove have
exhibited unexpected shifts in their composition in recent
years. The ascidians have almost disappeared at 20 m and,
together with sponges, are now much more scarce. While
some ascidian species such as Molgula pedunculata (domi-
nant in the sampling period 1994/1995) have almost disap-
peared, the pennatulid Malacobelemnon daytoni n. sp. and
the bivalve Laternula elliptica have extended their domi-
nance to deeper waters. During the sampling carried out in
1994/1995, these two species dominated at 15 m, while in
1998/999 they also dominated at 20 m (Sahade et al. 2008).
No explanation of the increase of abundance of these spe-
cies in the study area have been formulated yet, but the bet-
ter adaptation against other species and other groups to
environments with high sedimentation rates is suspected to
be one of the possible reasons of their high abundance in
the study site. Sessile ascidians cannot escape from the
great amount of sediments that collapse their Wlter systems,
while many bivalves can Wnd refuge under the sediment.
This behaviour has been also documented for some penna-
tulaceans (Soong 2005 for Virgularia juncea (Pallas); per-
sonal observation for Veretillum cynomorium (Pallas);
among others) that can withdraw below the sediment in a
short time on disturbance.
Discussion
The new pennatulacean species described in this paper is
placed in the family Kophobelemnidae by the following set
of characters: (1) colony symmetrically bilateral, with ven-
tral and dorsal naked tracks; (2) autozooids free, not fused
forming ridges, pads or polyp-leaves; and (3) autozooids
arranged biserally in longitudinal series along the entire
length of the rachis, and somewhat irregular distally.
In spite of the gross morphological similarities with col-
onies of the family Virgulariidae, the absence of polyp
leaves makes this assignation erroneous. In virgularids, this
character is clearly detectable even in the youngest
proximal autozooid leaves (see Kükenthal and Broch 1911;
Williams 1995).
According to Williams (1995), three genera are recog-
nized in the family Kophobelemnidae, namely Kophobe-
lemnon Asbjørnsen, 1856, Sclerobelemnon Kölliker, 1872,
and Malacobelemnon Tixier-Durivault 1965.
Kophobelemnon is characterized by its non-retractile
polyps, siphonozooids clearly diVerentiated from autozo-
oids in size, distributed among the autozooids’ bases, and
often with spiculated calyces, and in general by the densely
spiculated colonies (see Kükenthal 1915; Hickson 1916;
Williams 1995).
Sclerobelemnon
is easily distinguishable by its plate-like
sclerites, often irregularly shaped or biscuit-shaped, and
by its siphonozooids distributed between or below the
autozooids; often arranged in short longitudinal rows (see
Kükenthal 1915; Hickson 1916; Williams 1995).
The monotypic genus Malacobelemnon was described
from South Queensland (Australia) (Tixier-Durivault 1965)
and has been reported from the West Indian Ocean
(Williams 1995: 111 in text). Currently, a single species is
included in this genus, Malacobelemnon stephensoni
Tixier-Durivault 1965, with the possibility of another
species from southeastern Africa (see Williams 1995: 111).
The two species now considered in the genus Malacobe-
lemnon are easily distinguishable by the general colony
shape (proportionally much more elongated in M. daytoni
n. sp.), distribution and density of siphonozooids on the
rachis (restricted in two dense patches to the lower part of
the rachis below the autozooids in M. daytoni n. sp., but
present in scattered lines along the rachis in M. stephen-
soni), number of longitudinal series of autozooids along the
rachis length (much more numerous in M. daytoni n. sp.
than in M. stephensoni), and length and shape of the section
of the axis (round to oval and extending along the entire
length (even extending naked distally) of the rachis distally
in M. daytoni n. sp., but short and Xattened in M. stephen-
soni).
Some of the characters previously considered in the
genus Malacobelemnon should be slightly modiWed to
include the new Antarctic species (distribution of siphon-
ozooids, shape and length of axis). However, this range of
variability, if other additional sets of characters are not
involved, has previously been considered as a speciWc char-
acter in other pennatulid genera.
For instance, the distribution of siphonozooids is in
some cases used as speciWc characters in virgulariid genera
Stylatula Verrill, 1864 and Virgularia Lamarck, 1816 (see
Kükenthal 1915; Bayer 1961; López-González and
Williams 2002). The variations in the relative length of axis
in Malacobelemnon was already considered by Williams
(1995: 111), and is, for example, also used as a speciWc
character in the veretillid genus Cavernularia Valenciennes
in Milne Edwards and Haime, 1850 (see Williams 1989,
1990, 1995
; López-González et al. 2000). The variability of

Polar Biol (2009) 32:907–914 913
123
the shape in the transversal section of the axis is also used
as a speciWc character in the well-recognizable genus
Umbellula Cuvier, 1797 (see Kölliker 1880; Kükenthal
1915; Hickson 1916; Williams 1990, 1995; among others).
In the case of the colonies described in this paper, we prefer
to avoid the erection of another new monotypic genus for
the present Antarctic material, including it as another spe-
cies in a genus already described with few modiWcations to
its generic diagnosis.
From a bathymetric point of view, Malacobelemnon
daytoni n. sp. is one of the shallowest pennatulacean spe-
cies recorded. Other examples of shallow-water sea pens
occur in some veretillid genera such as Veretillum Cuvier,
1798 and Cavernularia (see López-González et al. 2000).
Williams (1995: 111) indicated a relatively shallow-water
vertical distribution (between 42 and 60 m in depth) for the
species in this genus, the only one previously described,
Malacobelemnon stephensoni (see Tixier-Durivault 1965),
and other possible records of an undescribed species from
South Africa.
Biogeographically, taking into account a possible spe-
cies in South Africa, the species of this genus are distrib-
uted from southeastern Africa to eastern Australia, now
including Antarctica (South Shetland Islands, close the
northern part of Antarctic Peninsula). This distribution is
more than probably aVected by the lack of knowledge with
new records of the species belonging to this genus, and for
this reason we prefer not to speculate here about the possi-
ble causes that originated the presence of the new taxon in
shallow Antarctic waters, until more information is avail-
able.
It has been hypothesized that sea pens (Order Penna-
tulacea) arose from alcyonacean ancestors in the shal-
low-water tropics, and subsequently diversiWed and
spread to temperate and polar latitudes as well as deeper
water (Hickson 1916; Williams 1993, 1995; López-
González and Williams 2002). The pennatulacean fossil
record is considered to be restricted to the Cretaceous
and Tertiary, with questionable or controversial records
from earlier geological periods (Williams 1995, 1997).
The origin of the Antarctic and Subantarctic pennatula-
cean fauna has been proposed to be diverse including
(López-González and Williams 2002): (1) deep-sea
immigrants from surrounding oceans; (2) immigrants
throughout the last continental shelf bridges; and (3)
those that evolved independently from a Cretaceous fau-
nal stock. On other occasions, as occurs in the present
contribution, biogeographic relationships are more diY-
cult to establish, sometimes due to a lack of previous
records to conWgure a deWned distributional area, or
because of our scarce knowledge concerning the true
phylogenetic relationships of the diVerent taxonomic
groups involved.
Acknowledgments We thank the members of the Jubany Polar sta-
tion, especially the divers who assisted with the collection of the mate-
rial examined here. Special thanks are addressed to Ricardo Sahade
and Marcos Tatián for their continuous support with material, informa-
tion and direct observations of the benthic fauna at Potter Cove (King
George Island). Guillermo Mercuri (Instituto Antártico Argentino)
provided the underwater photograph of a living specimen in Fig. 2. The
authors are also thankful for comments and suggestions given by the
Editor, Dr. Gary Williams and the two anonymous referees. Mr. Tony
Krupa is thanked for reviewing the English version.
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