Polar Biol (2009) 32:907–914 DOI 10.1007/s00300-009-0591-8
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 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 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 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.
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:
[email protected] 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:
[email protected] V. Fuentes e-mail:
[email protected]
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). Furthermore, a dense population of this pennatulacean species was also illustrated in naturalist guides oriented to the general public interested in the biodiversity of Antarctic underwater 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 previously 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 undescribed species of the kophobelemnid genus Malacobelemnon 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,
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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 autozooids, or grouped on two lateral areas below the lowermost autozooids. Sclerites are absent except for minute oval bodies 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.
Fig. 1 Map of Antarctica showing the type locality of Malacobelemnon daytoni sp. nov. in South Shetland Islands area
Malacobelemnon daytoni n. sp Figs. 2, 3, 4, 5, 6 Material examined
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 km2. The Wrst set of colonies was Wxed in buVered formaldehyde (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 (presumably 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 Francisco (CASIZ), and in the Anthozoan reference collection of the research group “Biodiversidad y Ecología de Invertebrados Marinos” of the University of Seville (BEIM).
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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 colony 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.
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Fig. 2 Underwater photograph of a colony of Malacobelemnon daytoni sp. nov. taken in situ at Potter Cove (King George, South Shetland Islands, Antarctica). Photo: Guillermo Mercuri
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 colony 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 siphonozooid 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 diYcult to delimit young autozooids from developed siphonozooids. 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, without 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 longitudinally grooved with eight intertentacular lines, clearly visible in the retracted state on the Xeshy basal part of the retracted polyps distally. Tentacles were not observed in the
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 photographed in (a) [BEIM (CRA-0015)], showing the densely placed siphonozooids area below the autozooids on one of the lateral sides of the colony
holotype by the retraction of the autozooids. In young autozooids, the Xeshy basal parts of the polyps are widely separated. 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 colony, rounded to oval in cross-section, and 0.55 mm in maximum diameter. Sclerites were absent in the entire colony. Minute ovals (similar to those observed in other pennatulacean species) were present in the interior of the peduncle.
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Fig. 4 Malacobelemnon daytoni sp. nov. SEM photographs of four sector of a colony. a Lateral view of peduncle– rachis limit, with the siphonozooids densely packed. b Lateral view of the proximal part of the rachis, just above the area observed in (a), with increasing space between polyps (siphonozooids and probably developing 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)
Fig. 5 Malacobelemnon daytoni 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 autozooids 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
Variations Preserved colonies ranged from 80 to 125 mm in length. The rachis was 87 mm long (81% of colony length, based on
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six colonies) and 4 mm wide at the widest point. The peduncle 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
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Fig. 6 Malacobelemnon daytoni 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
of autozooids and siphonozooids, and shape and size of autozooids and siphonozooids are as described for the holotype. 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.
Etymology
Colour
Geographic and depth distribution
Living specimens (Fig. 2) are light brown in the rachis, with whitish long polyps. Preserved specimens are dirty white to cream in colour.
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
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.
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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 sediment 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 (dominant in the sampling period 1994/1995) have almost disappeared, the pennatulid Malacobelemnon daytoni n. sp. and the bivalve Laternula elliptica have extended their dominance 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 species in the study area have been formulated yet, but the better 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 pennatulaceans (Soong 2005 for Virgularia juncea (Pallas); personal 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 ventral 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 colonies 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).
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According to Williams (1995), three genera are recognized in the family Kophobelemnidae, namely Kophobelemnon Asbjørnsen, 1856, Sclerobelemnon Kölliker, 1872, and Malacobelemnon Tixier-Durivault 1965. Kophobelemnon is characterized by its non-retractile polyps, siphonozooids clearly diVerentiated from autozooids 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 Malacobelemnon 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. stephensoni), 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. stephensoni). Some of the characters previously considered in the genus Malacobelemnon should be slightly modiWed to include the new Antarctic species (distribution of siphonozooids, 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 character 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
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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 species 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 species 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 species in South Africa, the species of this genus are distributed 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 possible causes that originated the presence of the new taxon in shallow Antarctic waters, until more information is available. It has been hypothesized that sea pens (Order Pennatulacea) arose from alcyonacean ancestors in the shallow-water tropics, and subsequently diversiWed and spread to temperate and polar latitudes as well as deeper water (Hickson 1916; Williams 1993, 1995; LópezGonzález 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 pennatulacean 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 faunal stock. On other occasions, as occurs in the present contribution, biogeographic relationships are more diYcult 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.
913 Acknowledgments We thank the members of the Jubany Polar station, especially the divers who assisted with the collection of the material examined here. Special thanks are addressed to Ricardo Sahade and Marcos Tatián for their continuous support with material, information 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.
References Bayer FM (1961) The shallow-water Octocorallia of the West Indian region: a manual for marine biologists. Stud fauna Curaçao Caribbean Islands 12:1–373 Bayer FM, GrasshoV M, Verseveldt J (1983) Illustrated trilingual glossary of morphological and anatomical terms applied to Octocorallia. E.J. Brill/Dr Backhuys, Leiden de la Vega SG (2000) Antártida. Las leyes entre las costas y el mar. Serie–Explorando Nuestra Naturaleza. Contacto Silvestre Ediciones, Buenos Aires Hickson SJ (1916) The Pennatulacea of the Siboga Expedition, with a general survey of the order. Siboga Exped Monogr 77(14):1–265 Kükenthal W (1915) Pennatularia. Das Tierreich. Verlag von R. Friedländer und Sohn, Berlin Kükenthal W, Broch H (1911) Pennatulacea. Wiss Ergebn Deutschen Tiefsee-Expedition “Valdivia” 13(1)2:113–576 López-González PJ, Williams GC (2002) A new genus and species of sea pen (Octocorallia: Pennatulacea: Stachytilidae) from the Antarctic Peninsula. Invertebr Syst 16:919–929. doi:10.1071/IT01027 López-González PJ, Gili JM, Williams GC (2001) New records of Pennatulacea (Anthozoa: Octocorallia) from the African Atlantic coast, with description of a new species and a zoogeographic analysis. Sci Mar 65(1):59–74. doi:10.3989/scimar.2001.65n159 López-González PJ, Gili JM, Williams GC (2000) On some veretillid pennatulaceans from the eastern Atlantic and western PaciWc Oceans (Anthozoa: Octocorallia), with a review of the genus Cavernularia Valenciennes and descriptions of the new taxa. J Zool (Lond) 250:201–216 Sahade R, Tatián M, Kowalke J, Kühne S, Esnal GB (1998) Benthic faunal association on soft substrates at Potter Cove, King George Island, Antarctica. Polar Biol 19:85–91. doi:10.1007/ s003000050218 Sahade R, Tarantelli S, Tatían M, Mercuri G (2008) Benthic community shifts: a possible linkage to climate change? Ber Polarforsch 571:331–337 Schloss IR, Ferreyra GA, Atencio A, González O, Fuentes V, Tosonotto G, Sahade R, Tatián M, Abele D (2008) Long-term hydrographic conditions and climate trends in Potter Cove. Ber Polarforsch 571:382–389 Soong K (2005) Reproduction and colony integration of the sea pen Virgularia juncea. Mar Biol (Berl) (146):1103–1109. doi:10. 1007/s00227-004-1509-1 Tixier-Durivault A (1965) Quelques octocoralliaires australiens. Bull Mus natn Hist Nat Paris (2) 37(4):705–716 von Kölliker RA (1880) Report on the Pennatulida dredged by H.M.S. Challenger during the years 1873–1876. Rep Scient Res Voyage of HMS. Challenger 1873–76. Zoology 1(2):1–41 Williams GC (1989) The pennatulacean genus Cavernularia Valenciennes (Octocorallia: Veretillidae). Zool J Linn Soc Lond 95(4):285–310. doi:10.1111/j.1096-3642.1989.tb02313.x Williams GC (1990) The Pennatulacea of southern Africa (Coelenterata, Anthozoa). Ann S Afr Mus 99(4):31–119
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914 Williams GC (1993) Biotic diversity, biogeography, and phylogeny of pennatulacean octocorals associated with coral reefs in the IndoPaciWc. Proceedings of the 7th international coral reef symposium, vol 2, pp 729–735 Williams GC (1995) Living genera of sea pens (Coelenterata: Octocorallia: Pennatulacea): illustrated key and synopses. Zool J Linn Soc Lond 113:93–140. doi:10.1111/j.1096-3642.1995.tb00929.x
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Polar Biol (2009) 32:907–914 Williams GC (1997) Preliminary assessment of the phylogeny of Pennatulacea (Anthozoa: Octocorallia), with a reevaluation of Ediacaran frond-like fossils, and a synopsis of the history of evolutionary thought regarding the sea pens. Proceedings of the 6th international conference on coelenterate biology, pp 497–509
