Oncosclera rosariae, Tavares-Frigo & Volkmer-Ribeiro & Oliveira & Machado, 2015

Tavares-Frigo, Maria da Conceição, Volkmer-Ribeiro, Cecília, Oliveira, Ana Elenice Zanini de & Machado, Vanessa de Souza, 2015, Freshwater sponges from the Pampa Biome, Brazil, with description of a new species of Oncosclera, Neotropical Biology and Conservation 10 (3), pp. 110-122 : 116-117

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https://doi.org/ 10.4013/nbc.2015.103.01

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Oncosclera rosariae


Oncosclera rosariae n.sp.

( Figures 2F View Figure 2 ; 3F View Figure 3 , 4-6 View Figure 4 View Figure 5 View Figure 6 )

Type material. Holotype, Brazil, Rio Grande do Sul: Alegrete, EPA of Ibirapuitã, Ibirapuitã River , Estância Marona , 30°06’10”S– 55°42’37”W, 27.III.2012, M.C. Tavares-Frigo and M. Pairet Jr. leg., MCN-POR 8928 . GoogleMaps

Paratypes: BRAZIL, Rio Grande do Sul: Alegrete, EPA of Ibirapuitã, Ibirapuitã River , Estância Sá Brito , 07.VI.2011, M. C. Tavares-Frigo and M. Pairet Jr. leg., MCN-POR 8916 ; 29.XI.2011, M.C. Tavares-Frigo and M. Pairet Jr. leg., MCN-POR 8918; Ibirapuitã River, Estância Marona , 27.III.2012, M. C. Tavares-Frigo and M. Pairet Jr. leg., MCN-POR 8919; 05. VI.2012, M.C. Tavares-Frigo and M. Pairet Jr. leg., MCN-POR 8928; 20.XI.2012, M.C. Tavares-Frigo and M. Pairet Jr. leg., MCN-POR 8937. Santana do Livramento, Ibirapuitã River, Passo do Ferrão , 02.XII.2011, M. C. Tavares-Frigo and M. Pairet Jr. leg., MCN-POR 8917; 08. VI.2012, MCN-POR 8924; 23.XI.2012, MCN- POR 8935 .

Diagnosis. Sponges thin, soft, greenish brown, spongin scarce, surface undulated, reflecting the structure of the canal system, pinacoderm thick. Skel- etal reticulum with axial and lateral fibers. Microscleres absent. Megascleres in one category of straight, abruptly pointed, smooth oxea. Gemmoscleres spiny short amphistrongyla resembling peanut shells and forming a basal thick continuous layer where the nude gemmules are merged. Gemmules abundant, foraminal tube short, straight, turned upside, an incipient pneumatic layer may form around some of the gemmoscleres. Isolated packages of gemmules merged in the gemmoscleres crust may be seen cov-

ered by the pinacoderm.

Description. Living sponge forming jelly, thin, irregular, greenish brown crusts with whitish thinner rim on the upper face of stones ( Figure 2F View Figure 2 ). Surface smooth, however irregular, undulated and sort of conforming the conspicuous canal system ( Figures 4A, 4B View Figure 4 ). Dry sponge evidencing a thick pinacoderm with conspicuous oscules and protrusion of the main fibers ( Figure 4C View Figure 4 ). Skeleton anisotropic with main and secondary multispicular fibers. Microscleres absent. Megascleres

short, smooth, straight slightly curved, abruptly pointed anfioxea ( Figures 3F View Figure 3 , 4D View Figure 4 ). Gemmoscleres, spiny, short to longer amphistrongyla resembling peanut shells ( Figures 3F View Figure 3 , 5A View Figure 5 ). Spines more abundant at the sclere extremities ( Figures 3F View Figure 3 , 5B View Figure 5 ). A bumped middle region is present in the gemmoscleres so that quite cylindrical ones are rare ( Figures 3F View Figure 3 , 5A View Figure 5 ). Spherical forms rare ( Figure 3F View Figure 3 ). The gemmoscleres compose a basal thick continuous layer where the nude gemmules are side by side merged ( Figures 6 View Figure 6 A-C). Dimensions of spicules in Table 2. Gemmules large ( Figure 6D View Figure 6 ), extremely abundant, ovoid, contained inside the thick, basal, common strata of gemmoscleres, inner gemmular coat thick ( Figure 6D View Figure 6 ), pneumatic coat incipient or absent ( Figures 6A, 6D View Figure 6 ), gemmoscleres disorderly packed in the basal layer and over the gemmules ( Figures 6B, 6D View Figure 6 ). Foraminal tube is single, turned upside, provided with short collar projecting at the surface of the gemmosclere covering ( Figures 6D, 6E View Figure 6 ).

Type locality: Ibirapuitã River, EPA of Ibirapuitã River, Rio Grande do Sul State, Brazil (29°21’48.25”S - 55°57’27.58”W).

Distribution: Presently known only from the type locality.

Habitat: The sponge occurred in three stations ( Table 1) under heavy river current and in areas not exposed to the sun along the margins. The specimens incrusted stones in the middle, margins and craters of the river, as well as the very river bedrock. The species was found throughout the sampling period and so seems to be a permanent component of the sponge fauna at such places ( Table 1).

Etymology: The species name is dedicated to the memory of M. Sc. Rosaria De Rosa Barbosa, for the many years of friendly collaboration on the research of the Brazilian freshwater sponge fauna, not to forget the always stimulating companionship along many field campaigns in the state of Rio Grande do Sul.

Remarks: Oncosclera rosariae n. sp. is closer to Oncosclera jewelli ( Volkmer-Ribeiro, 1970) but stands apart for its longer cylindrical gemmoscleres with reduced middle inflation and their conspicuous arrangement into a continuous common basal layer, where large nude gemmules with incipient to absent pneumatic coats are merged. On the other hand, the brittle rough green crusts of O. jewelli , however never stony hard as stated by Manconi et al. (2012), and its single gemmules invested with short amphistrongilous gemmoscleres and not restricted to the basal portion of the sponge grant the species its own indisputable position.

Oncosclera rosariae n. sp. stands also close to O. asiatica Manconi et al. (2012) , which has, however, spiny megascleres and longer, stout, straight to slightly curved cylindrical amphistrongyla gemmoscleres, with a rare occurrence of the middle enlarging and a more extensive distribution of small spines. Also to take into consideration is the disjunct distribution of genus Oncosclera which shows its larger specific richness in the Neotropical Region with now O. rosariae n.sp. representing the tenth species in this Region and the 17 th in terms of present and past global distribution (Manconi et al., 2012). Bonetto and Ezcurra de Drago (1967) advanced a gonduanic distribution for genus Stratospongilla ANNADALE (l909) and not Oncosclera VOLKMER- RIBEIRO (1970) as referred by Manconi et al. (2012), once at the time Oncosclera had not yet been described. As a matter of fact, genus Stratospongilla ANNANDALE (1909), restricted to species with microscleres ( Volkmer-Ribeiro, 1970), has not yet been detected in the Neotropical Region. However, a gonduanic distribution was formally proposed for genus Oncosclera , together with all other genera for the first time grouped in the Family Potamolepidae by Volkmer- Ribeiro and De Rosa-Barbosa (1979).


Mykotektet, National Veterinary Institute