Racekiela Bass & Volkmer-Ribeiro, 1998

Hernández, Victor M. Q. & Barreat, José G. N., 2017, Racekiela andina sp. nov. (Spongillida: Spongillidae): first report of a freshwater sponge from the Venezuelan Andes, Zootaxa 4341 (2), pp. 275-278 : 275-276

Genus Racekiela Bass & Volkmer-Ribeiro, 1998

Diagnosis sensu Manconi & Pronzato (2002)

Racekiela andina sp. nov.

Type specimens and localities. Specimens were deposited in the Collection of the Laboratory for Insect Ecology, Aquatic Section, Universidad de Los Andes ( CLEI-ULA). Holotype: CLEI-ULA 11 /1-2, Laguna Negra (08°47’19’’ N, 70°48’23’’ W), Rangel Municipality, Sierra Nevada National Park (N.P.), Mérida State, Venezuela, col. V.M.Q. Hernández and J.G.N. Barreat (28.V.2016) . Paratypes: CLEI-ULA 11 /3-4, Laguna de Mucubají (08°47’46’’ N, 70°49’36’’ W), Rangel Municipality, Sierra Nevada N.P., Mérida State, Venezuela, col. V.M.Q. Hernández and J.G.N. Barreat (28.V.2016) ; CLEI-ULA 11 /5-6, Laguna Los Anteojos (08°32’24’’ N, 71°04’26’’ W), Libertador Municipality, Sierra Nevada N.P., Mérida State, Venezuela, col. V.M.Q. Hernández (21.XII.2016) .

Geographic distribution. Known from four lakes in the páramo of Sierra Nevada N.P., located on the Cordillera de Mérida branch of the Northern Andes. Laguna Negra and Laguna de Mucubají, are both to the northwestern margin of the park, at 3460 and 3550 m elevation respectively. Laguna Los Anteojos consists of two adjacent lakes in the southwestern area of Sierra Nevada N.P. at 3924 m elevation.

Description. Small to medium sized sponge living attached to plants, rocks or on top of silt in shallow waters. Color in vivo varies from whitish to yellowish or green. Consistency is soft (fragile when dry) with a marked hispidation; growth is massive, encrusting or lobate. Large encrusting individuals present a marked reticulation. Oscules and ostioles are evenly dispersed over the ectosome ( Fig. 1A ). Skeleton is isodictyal with scanty spongin. Megascleres are straight to slightly curved acanthoxeas, spines pointing distally, in which a central knob may be present ( Fig. 2A ). Microscleres absent. Gemmules among largest in genus. These are conoidal with an inconspicuous foraminal tubule, fairly numerous at the basal side, golden ( Fig. 1B ), and possess the characteristic tri-layered arrangement; the pneumatic layer formed by irregular cameras ( Fig. 2B ). Gemmoscleres are of two types, both embedded radially and sometimes protruding outwards of the cortical layer. The shorter ones, most abundant, are birotules with spiny or smooth shafts; rotules are flat, deeply serrate and rays have tiny spines. They occasionally show stout, spined and sharp processes extending the shaft beyond the rotules ( Fig. 2C ). The longer ones, far less common, are slender pseudobirotules bearing small, straight to variously curved spines around the center; proximally-hooked spines appear at each end as in canonical pseudobirotules or when absent, these spicules resemble acanthoxeas instead ( Fig. 2D ). Measurements were made on 150 megascleres, 60 birotules, 20 pseudobirotules and 6 gemmules ( Table 1).

Species Megascleres Birotules Pseudobirotules Gemmules References: 1 Lindenschmidt (1950); 2 Volkmer-Ribeiro et al. (2010); 3Carballo et al. (2017); 4 Potts (1885); 5 Penney & Racek (1968); 6 Volkmer-Ribeiro & Machado (2007).

Ecology. Observed surrounding the stem of the aquatic macrophytes Isoetes sp. and Crassula venezuelensis . It also grows on rocks, decomposing tree trunks ( Polylepis sericea ), directly on top of the bottom silt or on submerged mosses, reaching a height of 10 cm above the substrate. Collected specimens occurred at depths comprised between 10 and 100 cm. A considerable number of diatoms were found inside the canal system of green specimens.

Etymology. andina sg. fem. nom. of the Latin andinus; in allusion to the Andes.

Discussion. The most prominent character of Racekiela andina sp. nov. is the possession of birotules which may show a long ornamented axis extended beyond the rotules. This is akin to the birotules of R. biceps ; however, Racekiela andina sp. nov. can be distinguished from the latter by the long slender pseudobirotules, in contrast to the robust dumbbell-shaped ones of R. biceps (viz. Lindenschmidt 1950). These slender pseudobirotules resemble instead those described for R. ryderii ( Manconi & Pronzato 2002) , R. pictouensis ( Ricciardi & Reiswig 1993) , R. sheilae (Volkmer- Ribeiro, De Rosa-Barbosa & Tavares 1988), R. montemflumina (Carballo et al. 2017) , and to a lesser degree R. cavernicola ( Volkmer-Ribeiro et al. 2010) ; but these species all have invariably unprojected birotule axes. Although some malformations were detected in the spicule set, as has been previously reported for Racekiela (e.g. Volkmer- Ribeiro et al. 2010, Carballo et al. 2017), they did not hinder a clear-cut assignment of spicules to the aforementioned categories. Most records of the genus are restricted to low altitude freshwaters, except for R. montemflumina , which was found at 2400–2700 m elevation (Carballo et al. 2017). R. andina specimens collected at 3924 m represent the highest record for any freshwater sponge so far (cf. Balliviaspongia wirrmanni Boury-Esnault & Volkmer-Ribeiro, 1991). Thus, the unique spicule set, especially regarding gemmosclere morphs and spicule micrometries, as well as the sponge’s particular geographic distribution, agree with it representing a new species.

Figures

FIGURE 1. Racekiela andina sp. nov. in vivo et in situ, and dry gemmules. (A) Holotype (CLEI – ULA 11 / 1 - 2) attached to a rock, growing in an encrusting and lobate fashion (Photograph by Karla Aguilar). (B) Dry gemmules showing the foramen (lower image) and covered in megascleres.

FIGURE 2. SEM micrographs of spicules and a gemmule cross section. (A) Acanthoxeas. (B) Tri-layered gemmular theca. Radially embedded gemmoscleres can be seen. (C) Shorter gemmoscleres: birotules. Note the processes extending the axis in the third and fourth birotules to the right. (D) Longer gemmoscleres: pseudobirotules. The left-most spicule is a light micrograph. Both (C) and (D) show spicules deviating from the common types (far-right).