Corvoheteromeyenia australis (BONETTO AND EZCURRA DE DRAGO, 1966)

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

Corvoheteromeyenia australis (BONETTO AND EZCURRA DE DRAGO, 1966)

( Figures 2C ; 3C )

Corvomeyenia australis Bonetto and Ezcurra De Drago (1966):137 ; Ezcurra de Drago (1979):110; Tavares et al. (2003):177.

Examined material: BRAZIL, Rio Grande do Sul: Santa do Livramento, EPA of Ibirapuitã, Ibirapuitã River, Passo do Ferrão , 25.III.2011, M.C. Tavares-Frigo and M. Pairet Jr. leg., MCN-POR 8844 ; 02.XII.2011, MCN-POR 8899; 03.II.2012, MCN- POR 8906 ; 30.III.2012, MCN-POR 8907; 08. VI.2012, MCN-POR 8925; 23.XI.2012, MCN-POR 8934; Ibirapuitã River , Passo do Cerrito, 03.II.2012, M.C. Tavares-Frigo and M. Pairet Jr. leg., MCN-POR 8904.

The sponge only occurred in two stations ( Table 1), which correspond to

sites with shallow water. In Passo do Cerrito the surface water was frozen in June 2012. The sponge formed crusts on substrates exposed to sunlight, encrusting both the continuous rocky bottom and adjacent loose stones, or in the region along the exposed edge, next to the sandy bank of the Ibirapuitã River, in the latter case, sometimes adhering to submerged vegetation. The specimens varied in form from thin crusts to arborescent showing up to 5.0cm in height, with intense green colouring ( Figure 2C ) and whitish gemmules, both dispersed on the skeleton and attached to the substrate. The sponge did not present specimens throughout the sampling periods, indicating seasonal development ( Table 1). The spicule set conformed to the original description of the species (Bonetto and Ezcurra de Drago, 1966) ( Figure 3C ).

Remarks: To date, the records of C. australis are restricted to occurrences in the Pampa Biome, both in Argentina and in Rio Grande do Sul State, as well as in Lake Guaíba (Tavares et al., 2003) and downstream of it, in coastal lagoons surroundings the Laguna dos Patos (Volkmer-Ribeiro et al., 2007a, 2007b). However, sponge spicules from this species have recently been identified in lake sediments from the Pleistocene age in the State of Goiás, acting as an environmental indicator that the climate was previously colder in that region of the country (Machado et al., 2014). The species is included in the official list of Rio Grande do Sul State’s threatened fauna (Rio Grande do Sul, 2014).

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.