First record and range extension of the Antarctic coral Flabellum (Flabellum) impensum Squires, 1962 (Cnidaria: Scleractinia) in Argentinean coastal waters

The present paper reports the occurrence of the Antarctic coral Flabellum impensum in Tierra del Fuego Province, Argentina, and extends its distribution northwards in the south-west Atlantic Ocean. Nine individuals were found in Argentinean coastal waters in 2014, also representing one of the shallowest records of the species.


I N T R O D U C T I O N
Taxonomic and biogeographic research dealing with coldwater coral species from Antarctic and sub-Antarctic waters have been extensively reviewed by Cairns (1982).Later, Cairns (1990) diagnosed, keyed and illustrated the Antarctic species, including some that also occur off sub-Antarctic Argentina.General information on coral and other cnidarian species of the Magellanic Region (Argentina) has been compiled by Zamponi (2008), while more recently, Cairns & Polonio (2013) added new distribution ranges for some scleractinian corals, and also described new species from the Malvinas/Falkland Islands and off Argentina.
Flabellum (Flabellum) impensum is a very conspicuous species, typically from Antarctica, distinguished from the other Flabellum species of the region by its larger size and greater number of septa.It is an endemic species of the Antarctic region, distributed at circumpolar continental Antarctica, the Palmer Archipelago, South Shetland Islands, South Orkney Islands and South Sandwich Islands, with one disjunct record from the Antipodes Islands (Cairns, 1990(Cairns, , 1995)).It is commonly collected between 100 and 1000 m depth, although its bathymetric range is reported to be 46 -2260 m (Cairns, 1990).
We report the first record of the species outside Antarctic waters, in South America, specifically in shallow coastal waters of Tierra del Fuego Province, Argentina.The extension range of this typically Antarctic species is discussed.

M A T E R I A L S A N D M E T H O D S
The studied material was collected during a research cruise on the OV 'Puerto Deseado' (Argentina), using a bottom trawl.The research campaign aimed to collect biological and oceanographic data around Tierra del Fuego Province (Argentina), including the Beagle Channel, after the Antarctic phase.The corals were collected in the north of Tierra del Fuego, at 54817.64 ′ S 66815.37 ′ W, at 52 m depth (Figure 1).
Individuals were collected alive (some were slightly broken due to sampling procedure), photographed on board and kept frozen for transportation to the Laboratory.Thereafter, the individuals were cleaned, dried, measured and identified.General characterization of the benthic assemblage of the haul is also provided.Nine individuals of Flabellum (Flabellum) impensum were identified.They were deposited at the Museo Argentino de Ciencias Naturales 'Bernardino Rivadavia', under the collection number MACN-In 39802.They all presented the typical flabellate shape of the species, a Greater Calicular Length/Lesser Calicular Length ratio (GLC/LCL) between 1.76 and 2.8, pedicels ranging from 2 to 3 mm in diameter, and had from 170 to 238 septa in the bigger individuals having six cycles (Figure 2, see Cairns, 1990 for descriptive and general terminology).The corals ranged between 43 and 65 mm in height.A rudimentary columella deep within the fossa (conformed after the fusion of lower inner edges of the septa) was evident in some broken individuals (Figure 2C).
Bryozoa colonies were found on one or both sides of the corals (Figure 2D) on eight individuals, which could be interpreted as an indication of an upright living position, according to Cairns (1982).One of the broken individuals also presented bored holes in one side.
Faunistic assemblage at the sampling site based on the catch of the haul showed the presence of a great variety of organisms, comprising many large individuals of the tunicate Paramolgula gregaria (Lesson, 1830) and the cirriped Austromegabalanus sp., and also large colonies of bryozoans.Additionally, at least 12 sponge morphospecies were collected, mollusks (Polyplacophora, Gastropoda and Bivalvia), many echinoderm species comprising the basket star Gorgonocephalus chilensis (Philippi, 1858), the ophiuroid Ophiactis asperula (Philippi, 1858) and the sea urchins Austrocidaris canaliculata (A.Agassiz, 1853) and Pseudechinus magellanicus (Philippi, 1857), primnoid and other soft corals belonging to Alcyonacea, sea anemones, polychaetes, many peracarid crustaceans and a few fishes.
The present results extend the distributional range of Flabellum (F.) impensum to South America, in Argentinean coastal waters of the Tierra del Fuego Province.This is also one of the shallowest records of the species (52 m), commonly found at depths ranging from 100 to more than 2000 m.Additionally, there was one unpublished (and up to present, doubtful) record of Flabellum impensum off the Buenos Aires Province, at 40.78S 57.28W, collected at a depth of 85 m in the research vessel 'Edisto' in the year 1959 (Figure 1).This record corresponded to a specimen of conical shape, deposited at the Smithsonian National Museum of Natural History and identified by Cairns (Collection No. 47377) (S.Cairns, personal communication).The present finding corroborates the presence of this species in Argentinean waters, extends its distribution to Tierra del Fuego Province (54817.64′ S) and helps to corroborate the early finding at 40.78S in South America, updating the septentrional distribution range of Flabellum impensum.

A C K N O W L E D G E M E N T S
The authors would like to thank Dr Stephen Cairns who checked the species identification, provided the early (unpublished) record and made useful suggestions for this paper.This study was partially supported by PICT 2013-0629 (to L. Schejter).
Email: schejter@inidep.edu.ar 1 Marine Biodiversity Records, page 1 of 3. # Marine Biological Association of the United Kingdom, 2015 doi:10.1017/S1755267215000858;Vol.8; e104; 2015 Published online R E S U L T S A N D D I S C U S S I O N

Fig. 1 .
Fig. 1.Collection sites of Flabellum impensum in Argentina, and known distribution and records from the Antarctic Peninsula and sub-Antarctic waters (from Cairns, 1982).Solid square: present study; solid circles: Cairns' previous records; solid triangle: Cairns' unpublished record.