Oncosclera navicella ( CARTER, 1881 )

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 : 114

Oncosclera navicella ( CARTER, 1881)

( Figures 2D ; 3D )

Spongilla navicella Carter (1881):87; Bonetto and Ezcurra de Drago, 1967:335.

Oncosclera navicella Volkmer-Ribeiro (1970):437 ; Tavares and Volkmer- Ribeiro (1997): 97; Volkmer-Ribeiro and Pauls (2000):19; Tavares et al. (2003):177.

Examined material: BRAZIL, Rio Grande do Sul: Alegrete, EPA of Ibirapuitã, Ibirapuitã River, Estância Sá Brito , 23.III.2011, M.C. Tavares-Frigo and M. Pairet Jr. leg., MCN-POR 8846 ; 07. VI.2011, MCN-POR 8895; 29.XI.2011, MCN- POR 8901 ; 27.III.2012, MCN- POR 8914 ; 05. VI.2012, MCN-POR 8930; 20.XI.2012, MCN-POR 8939; 22.I.2013, M. C. Tavares-Frigo,A. E.Z. Oliveira and M. Pairet Jr. leg., MCN- POR 8946 ; Ibirapuitã River , Estância Maronna, 07. VI.2011, MCN-POR 8920; 27.III.2012, MCN-POR 8910. Santa do Livramento , Ibirapuitã River, Passo do Ferrão, 25.III.2011, M.C. Tavares-Frigo and M. Pairet Jr. leg., MCN-POR 8842; 02.XII.2011, MCN-POR 8898; 03.II.2012, MCN- POR 8905 ; 30.III.2012, MCN-POR 8908; 08. VI.2012, MCN-POR 8926; 23.XI.2012, MCN-POR 8936.

The sponge encrusts the solid rocky bottom or loose stones in the river, forming permanent crusts varying in thickness from thin to thick, with occasional needle-like projections of up to 15mm in height ( Figure 2D ) with whitish, yellowish or greyish colouring ( Figure 2D ). Large, visible gemmules, orange-yellow colour, noticeable particularly in the peripheral region of the crusts, fixed to the substrate, or even forming isolated clusters, were evident and observable to the naked eye. The sponge occurred in three stations ( Table 1). The spicule set conformed to the redescription of the species (Tavares and Volkmer- Ribeiro, 1997) ( Figure 3D ).

Remarks: In Rio Grande do Sul State O. navicella was recorded in tributaries of the Lake Guaíba basin, particularly the Jacuí River, with isolated records of the species also in the Ibicuí-Mirim, a tributary of the Ibicuí (De Rosa-Barbosa, 1984). However, O. navicella commonly occurs on the rocky beds of large South American rivers, and is distributed continuously from Venezuela ( Volkmer-Ribeiro and Pauls, 2000), in the north to the south of Brazil ( Tavares and Volkmer-Ribeiro, 1997; Batista et al., 2003), and in the Paraná-Uruguay Basin, in Argentina (Bonetto and Ezcurra de Drago, 1967, 1970; Ezcurra de Drago and Bonetto, 1969).

Figures

Figure 2. Photographs of the living sponge species detected in the Environmental Protection Area (EPA) of Ibirapuitã, southern Brazil. A, Heteromeyenia insignis WELTNER (1895); B, Corvospongilla seckti BONETTO and EZCURRA DE DRAGO (1966); C, Corvoheteromeyenia australis (BONETTO and EZCURRA DE DRAGO, 1966); D, Oncosclera navicella (CARTER, 1881); E, Oncosclera schubarti (BONETTO and EZCURRA DE DRAGO, 1967); F, Oncosclera rosariae n.sp. Bar = 3 cm.

Figure 3. Camera lucida drawings of the spicular sets of sponge species sampled in the Environmental Protection Area (EPA) of Ibirapuitã, southern Brazil. A, Heteromeyenia insignis WELTNER (1895); B, Corvospongilla seckti BONETTO AND EZCURRA DE DRAGO (1966); C, Corvoheteromeyenia australis (BONETTO AND EZCURRA DE DRAGO, 1966); D, Oncosclera navicella (CARTER, 1881); E, Oncosclera schubarti (BONETTO AND EZCURRA DE DRAGO, 1967); F, Oncosclera rosariae n.sp. meg: megascleres; gem: gemmoscleres; gem-1: short gemmoscleres; gem-2: long gemmoscleres; mic: microscleres; mic-1: chaela microsclere; mic- 2: birotulated microsclere). Bar = 50 micrometers.