root sponge Rossella racovitzae

Rossella racovitzae is found throughout Antarctica and the Antarctic Peninsula, South Shetland Islands, South Georgia Island, Falkland Islands, and Argentina from depths of 18 to 2,000 meters [1,5,7,9]. Here Dendrilla antarctica is in the foreground of R. racovitzae.

R. racovitzae is highly polymorphic and of several types [3,10]:

Large Type I: large upright barrel or vase shape; white, yellow or orange color; numerous small conules on surface with long spicule bundles protruding; no basal spicule tuft;

Large Type II: large upright barrel or vase shape; white to grey color; small conules on surface but fewer than Type I; few and weaker spicule bundles protruding from conules; very weak basal spicule tuft;

Budding Type: small upright vase or egg shape; up to sixteen centimeters high; white to grey color; covered with felt-like mass of short spicules; very small apical oscules; numerous buds.

The size of R. racovitzae is up to fifteen centimeters high for the Budding Type and up to forty-six centimeters for the Large Type [8,10]. One observer notes the Budding Type occurring on very soft bottoms and the Large Type occurring on spicule mats and soft bottoms as well [10]. The isopod fish parasite Caecognathia calva may spend its adult life in the suboscular space of the Budding Type R. racovitzae and is not found in the Large Type R. racovitzae [8].

Here is the Budding Type morph of Rossella racovitzae; light gray in color, it can be found buried in the sponge spicule mat anchored by long spines and with its osculum (openings) extending above the surface [2,4]. Budding from stem specimens may be evident [2]. It has been observed that the spicules on R. racovitzae buds increase flotation so that buds are carried away by currents [4]. Burial in the sponge spicule mat shields R. racovitzae from predation [4]. R. racovitzae is eaten by the seastars Odontaster meridionalis, Odontaster validus, Acodontaster conspicuus, and Acodontaster hodgsoni and the dorid nudibranch Doris kerguelenensis [2].

Here is the budding type of Rossella racovitzae with the hydroid Corymorpha microrhiza covering it.

R. racovitzae has been reported as the most abundant member of the Cape Armitage sponge community being 41.8 percent cover of the benthic surface and 70.9 percent of the sponge biomass [2]. Small R. racovitzae may increase their volumes almost 300% in three years [4]. In ten years time, specimens of R. racovitzae elongated as follows: five grew 11 centimeters, two grew 13 centimeters, one grew 14 centimeters, two grew 15 centimeters, and three grew 16 centimeters [4].

Many organisms can be found within R. racovitzae including polychaete worms, amphipods, isopods, pantopods, gastropods, nudibranchs (Doris kerguelenensis), and brittle stars [6]. R. racovitzae spicules act as natural optical fibers and shade-adapted diatoms adhere to its spicules, living inside the sponge, using the light channeled down the spicules for photosynthesis [12]. Many benthic diatoms live within the sponge spicule mat on the seafloor; the sponge spicules create a dimensional matrix in the sediment in which the diatoms live, as well as act as optical fibers channeling light a short distance (five centimeters) into the mat, thus enhancing benthic diatom photosynthesis [11,12].

Taxonomic Note: Barthel & Tendal suggest that the budding type of R. racovitzae may be an independent taxon [7].

1: Hooper, JNA & Wiedenmayer, F. Porifera. IN: Zoological Catalogue of Australia. Volume 12. Wells, A, ed. Melbourne : CSIRO Australia, 1994; 2: Ecological Monographs 44(1):105-128, 1974; 3: Antarctic Science 4(2):137-150, 1992; 4: Biologie des Spongiaires, Sponge Biology. C Levi and N Boury-Esnault, eds. Colloques Internationaux du Centre National de la Recherche Scientifique Number 291. Paris : Centre National de la Recherche Scientifique, 1979. pp.271-282; 5: B.A.N.Z. Antarctic Research Expedition, 1929-1931, under the command of Sir Douglas Mawson, Kt., O.B.E., B.E., D.Sc., F.R.S., Reports -- Series B (Zoology and Botany). Volume 9, part 4. Porifera -- Part 1: Antarctic Sponges. VM Koltun. Adelaide : Mawson Institute for Antarctic Research, University of Adelaide, 1976; 6: Associated Fauna of Selected Sponges (Hexactinellida and Demospongiae) from the Weddell Sea, Antarctica. Kunzmann, K. Berichte zur Polarforschung / Reports on Polar Research 210, 1996; 7: Antarctic Hexactinellida. Dagmar Barthel & Ole S. Tendal. Champaign, Ill. : Koeltz Scientific Books, 1994. Theses Zoologicae, Volume 23. Synopses of the Antarctic Benthos, Volume 6; 8: Verhandlungen Deutsche Zoologische Gesellschaft 85(2):271-276, 1992; 9: Issledovaniia Fauny Morei 19:49-55, 1972; 10: Ophelia 36(2):111-118, 1992; 11: Scientia Marina 63(Supplement 1):113- 121, 1999; 12: Nature 383(6599):397-398, 1996

ID of inv205a by Walentina de Weerdt and Rob van Soest (provided without specimens for checking microscopic details). Text ©Peter Brueggeman. Photographs ©Jim Mastro & Norbert Wu. Photographs may not be used in any form without the express written permission of Jim Mastro or Norbert Wu. Norbert Wu no longer grants permission for uncompensated use of his photos under any circumstances whatsoever; want more info?