Acanthotylotra xingu, Pinheiro & Calheira & Martins & Janson & Taylor & Samaai, 2020

Pinheiro, Ulisses, Calheira, Ludimila, Martins, Celina, Janson, Liesl, Taylor, Ricky & Samaai, Toufiek, 2020, Two new species of freshwater sponges from Neotropical and Afrotropical Regions, Zootaxa 4728 (3), pp. 363-371 : 368-369

Acanthotylotra xingu sp. nov. Pinheiro, Calheira & Samaai

( Fig. 3 ; Table 2 )

Material examined. Holotype UFPEPOR 2046. Gorgulho da Rita Beach , Xingu River, Altamira, Pará State, Brazil, (3.560917°S; 52.28524°W), coll. Martins, C. S. 29/09/2014, depth 1 m. Paratypes UFPEPOR 2338, coll. Martins, C. S. 29/09/2014; and UFPEPOR 2339, coll. Martins, C. S. 29/09/2014 (collected together with the holotype).

Etymology. The specific epithet refers to the type locality, Xingu River, and the indigenous people living near the Xingu River.

Type locality. Xingu River , Altamira, Pará State, Amazon Basin, Brazil .

Type locality description. The Xingu river is classified as a river of clear water with very little organic material input. This river has many variations in the volume of water drained between full and dry periods. The collection site is known as Gorgulho da Rita Beach, located near the Altamira city. This region, before the construction of Belo Monte hydroelectric power plant, had an extensive area of exposed sand (sand bank) with shallow water (1 m deep), ranging to slow to strong flow water and substrate formed by stones and sand.

Diagnosis. Potamolepidae encrusting with smooth surface. Megascleres strongyles microgranulated with inflated tips, and slender oxeas. Microscleres absent. Gemmules absent.

Description. Encrusting, 3 mm in length x 3 mm in thickness x 5 mm in width. Surface smooth with inconspicuous oscules. Consistency spongy, soft and fragile. Colour in situ unknown; white when preserved in ethanol ( Fig. 3.A ).

Skeleton. Ectosomal skeleton not observed. Choanosomal skeleton anisotropic with paucispicular tracts of megascleres forming regular to irregular reticulate meshes. Spongin scarce ( Fig. 3.B ).

Spicules. Megascleres. Strongyles slightly curved, microgranulated with inflated tips, 135.2–158.1–177.1 / 11.3–14.9–19.3 μm ( Fig. 3.C ). The center of the spicule is slightly inflated, and microgranulations concentrated at the tips. Microscleres. Unknown or absent. Gemmules and gemmuloscleres. Unknown or absent ( Table 2 ).

Substratum, ecology and depth range. Epibiont on a specimen of Drulia brownii ( Bowerbank, 1863) , which grows on consolidated substrata. Collected from shallow waters with a slight current at a depth of 1 m.

Remarks. Acanthotylotra xingu sp. nov. has strongyles with microgranulations and inflated tips and lack microscleres and gemmules. These morphological features are similar to species in the genera Echinospongilla and Potamolepis . Echinospongilla brichardi and Acanthotylotra xingu sp. nov. both have strongyles with inflated tips as megascleres and differ in that the strongyles of the former are smooth oppose to being microgranulated in the latter.

Potamolepis species have smooth strongyles and oxeas as megascleres compared to only strongyles with microgranulations and inflated tips found in Acanthotylotra xingu sp. nov. Echinospongilla sp. and Potamolepis sp. are endemic to the Afrotropical Region, which could be because of the absence of gemmules that restrict widespread dispersal and geographic ranges on a large-scale ( Manconi & Pronzato 2007). However, most of species of this Region was recorded only once, and further investigation is necessary ( Manconi & Pronzato 2009).

In the Neotropical Region the genera Oncosclera and Uruguaya share a similar spicular set with Acanthotylotra xingu sp. nov. Oncosclera has an irregular skeleton architecture with paucispicular tracts and lacks microscleres similar to that in Acanthotylotra xingu sp. nov. Oncosclera differs in having stout oxeas as megascleres, gemmules and gemmuloscleres strongyles, spicular characters absent in Acanthotylotra xingu sp. nov. However, in Uruguaya corallioides ( Bowerbank, 1863) megascleres are strongyles microgranulated without at the inflated tips, and possess gemmules with gemmuloscleres smooth strongyles ( Pinheiro et al. 2003). Acanthotylotra xingu sp. nov. has a single category of megascleres, whereas A. alvarengai has more than one category of the megascleres. In Acanthotylotra xingu sp. nov. the microgranulations is concentrated at the inflated tips, while in A. alvarengai the spines form small grouped on the convex section of the spicule, the tylote tips entirely covered with minute spines.

Acanthotylotra xingu sp. nov. is tiny, cryptic and epibiont on other sponges, which makes it difficult to find - similar to that found in Acanthotylotra . Volkmer-Ribeiro et al. (2009) described all the specimens of Acanthotylotra alvarengai from one specimen of D. uruguayensis . The studied specimens of Acanthotylotra xingu sp. nov. were a distinct white crust stuck to the fibers of a specimen of D. brownii (UFPEPOR 2016).

Figures

FIGURE 3. Holotype (UFPEPOR 2046) of Acanthotylotra xingu sp. nov. A, sponge. B, Skeletal network of megascleres. C, SEM of spicules megascleres. Scale bars: A = 1 mm; B = 125 μm; C = 50 μm.