Clathria (Axosuberites) retamalesi, Fernandez & Bravo-Gómez & Cárdenas & Hajdu, 2020

Fernandez, Julio C. C., Bravo-Gómez, Diego, Cárdenas, César A. & Hajdu, Eduardo, 2020, Sponges from Doumer Island, Antarctic Peninsula, with description of new species of Clathria (Axosuberites) Topsent, 1893 and Hymeniacidon Bowerbank, 1858, and a re-description of H. torquata Topsent, 1916, Zootaxa 4728 (1), pp. 77-109 : 94-101

Clathria (Axosuberites) retamalesi sp. nov.

( Table 4 ; Figures 8–10 )

Type locality. Doumer Island , WAP .

Material examined. Holotype—MNRJ 20638, South Bay, Doumer Island ( WAP), (P1, 64°52’27.0’’ S, 63°34’34.5’’ W), 20 m depth, 13 Jan 2016, coll. C. A. Cárdenas.

Diagnosis. Clathria (Axosuberites) from Antarctica (shallow waters), with massive to slightly subspherical habit, bright orange color in vivo, large choanosomal styles (up to ca. 1500 × 47 µm), auxiliary subectosomal styles, in two categories (total range 350–990 × 10–25 µm), auxiliary ectosomal styles (up to ca. 370 × 7 µm) and toxas of common shape in four size categories (total range 28–520 µm).

Description. Habit, massive and slightly subspherical, bushy, comprising a large number of adjacent cylindrical projections (ca. 1.5 mm diameter) aligned longitudinally frequently connected to each other by thin tissue strings (contracted in preservative). A translucent thin membrane covers whole body (in life). Consistency, firm, barely compressible and slightly brittle. Surface, with numerous branches, covered by a strongly adhered thin membrane. Oscules, simple apertures. Color in vivo, bright orange, turning beige in ethanol ( Figs. 8 A–F).

Skeleton. Extra-axial plumoreticulate skeleton ( Fig. 9A ) with bouquets of small ectosomal auxiliary styles piercing the surface in a perpendicular or oblique way, supported by bundles of subectosomal auxiliary styles (smaller category) and tracts of choanosomal main styles reinforced by subectosomal auxiliary styles (larger category) ( Figs. 9 B–C). Choanosome with axially-compressed ascending tracts of choanosomal principal styles, reinforced by subectosomal auxiliary styles (larger category); styles protrude through tracts ( Figs. 9 D–E). Different sizes of toxas scattered throughout the skeleton.

Spicules. Megascleres ( Table 4 ): Choanosomal principal styles ( Figs. 10 A–B), stout, slightly fusiform, slightly curved, and completely smooth. Base, slightly swollen and narrow, acerate tip: 1015– 1176.6 (109.2)–1458.5 × 25– 35.4 (6.6)– 47 µm (n= 30). Larger subectosomal auxiliary styles ( Figs. 10 C–D), thinner and smaller than the previous category, curved to slightly sinuous, completely smooth, with a base slightly swollen and an acerate tip: 715– 843.2 (74.6)–990 × 20– 22.2 (1.8)– 25 µm (n= 30). Smaller subectosomal auxiliary styles ( Figs. 10 E–F), similar to the previous subectosomal auxiliary styles but with smaller size: 350– 504.7 (78.7)–628 × 10– 13 (1.9)– 16 µm (n= 30). Ectosomal auxiliary styles ( Figs. 10 G–H), smaller than all previous categories, thin, straight, smooth, with very small spines at the base: 216– 270 (45.1)–370 × 5– 5.9 (0.6)– 7 µm (n= 30). Microscleres ( Table 4 ): Toxas I ( Fig. 10I ), completely smooth, slender, tapering gradually to sharp points: 249– 351.3 (75.9)– 520 µm (n= 30). Toxas II ( Figs. 10J, 10M ), much smaller than toxas I, but with similar shape: 98– 138.2 (22.5)– 168 µm (n= 30). Toxas III ( Figs. 10K, 10N ), much smaller than toxas II, with similar shape, but with tips slightly raised (tricurved): 67– 73.4 (6.8)– 88.7 µm (n= 30). Toxas IV ( Figs. 10L, 10O ), much smaller than toxas III, completely smooth, shape more similar to toxas I and II: 28– 33.8 (5.2)– 42 µm (n= 30).

Ecology, bathymetry and distribution. The specimen was collected from hard substrates, over encrusting calcareous algae, growing close to red and brown algae and other sponge species; viz., Mycale acerata and Sphaerotylus antarcticus . Isopods were present in its choanosomal region. It occurs in shallow waters (20 m depth).

Etymology. The name of this species honors Dr José Retamales, former director of the Chilean Antarctic Institute (INACH), for his enormous contribution to the development, improvement and increase of research activities carried out by the Chilean Antarctic Program, and other Antarctic programs in the WAP.

Remarks. Most species of Clathria (Axosuberites) have been recorded from the Southern Hemisphere (14 of 19 species) ( van Soest et al. 2019), but only five of them are known from Antarctica and the sub-Antarctic region; viz., C. (A.) flabellata ( Topsent, 1916) , C. (A.) georgiaensis Hooper, 1996 , C. (A.) nidificata ( Kirkpatrick, 1907) , C. (A.) ramea ( Koltun, 1964) and C. (A.) rosita Goodwin, Brewin & Brickle, 2012 . All known species of C. (A.) have their data tabulated here ( Table 4 ).

The combination of absence of chelae and presence of toxas sets C. (A.) retamalesi sp. nov. apart from most species of C. (A.), aside C. (A.) flabellata , C. (A.) nidificata , C. (A.) ramea and C. (A.) rosita . These species are contrasted to the new one in greater detail below. In addition to the combined lack of chelae and presence of toxas, the new species can be easily distinguished from all known C. (A.) by a combination of subspherical habit, bright orange color, choanosomal principal styles approaching 1500 × 50 µm, auxiliary subectosomal styles up to ca. 1000 × 25 µm, auxiliary ectosomal styles reaching over 370 × 7 µm, and toxas 28–520 µm long.

The Antarctic C. (A.) flabellata is flabelliform, possesses quite smaller choanosomal styles (ca. 500–1000 × 20 µm), a single category of auxiliary styles, and toxas which seem never to reach over 300 µm in length. All these characters set it confidently apart from the new species proposed.

Despite the fact that C. (A.) nidificata and C. (A.) ramea possess choanosomal styles with dimensions (viz., 595–1140 × 21–61 µm and 700–1500 × 21–42 µm, respectively) near to those of the new species (viz., 1015–1458 × 23–47 µm), the former has a claviform-flabellate habit and totally lacks auxiliary subectosomal styles, while C. (A.) ramea has a digitiform habit and larger auxiliary ectosomal styles (up to 870 × 10 µm). The new species has thicker auxiliary subectosomal styles (in two categories; total range 350–990 × 10–25 µm). Thus, all three species are easily distinguished from each other.

Clathria (A.) rosita from South Georgia, sub-Antarctic region, has relatively similar habit and color to C. (A.) retamalesi sp. nov., viz., massive with numerous short branches and an orange color in life ( Goodwin et al. 2012: 13, Fig. 7A ). However, the new species is set apart from C. (A.) rosita by its larger choanosomal principal styles (1015–1458 × 23–47 µm vs. 272–385 × 11–19 µm), smaller auxiliary subectosomal styles (in two categories, larger 715–990 × 20–25 µm and smaller 350–628 × 10–16 µm, vs. one category, 357– 597 –1012 × 15– 20 – 31 µm) and toxas with relatively uniform appearance (all categories are slender vs. smaller category is a stout oxhorntoxas). Furthermore, C. (A.) retamalesi sp. nov. has larger toxas than C. (A.) rosita (28–520 µm long vs. 7–328 µm long).

Given the rationale above, we consider C. (A.) retamalesi sp. nov. to be clearly distinct from every known species of C. (A.) ( Table 4 ). More importantly, there are neat differences in many characters of habit and spiculation setting it apart from Antarctic and sub-Antarctic species, which might otherwise be confused. The new species is now the sixth species of C. (A.) known from Antarctica and the twentieth worldwide.

Unfortunately two morphotypes of Microcionidae from Doumer Island (viz., Microcionidae sp. 1 and Microcionidae sp. 2) were not identified (Supplementary table 1), but they are different from C. (A.) retamalesi sp. nov. due to spicultion (pers. obs.).

Hooper (1996) has mentioned Clathria as being possibly a polyphyletic group due to presence of several subgenus, which are defined by homoplasious morphological characters. Molecular phylogenetic studies have confirmed that the genus Clathria is polyphyletic ( Redmond et al. 2013; Thacker et al. 2013) as well as some of its subgenera ( Redmond et al. 2013). Unfortunately, no Axosuberites subgenera was included in previous molecular phylogenetic studies ( Morrow & Cárdenas 2015). A molecular phylogenetic analysis for the specimen examined in the present study is suggested in order to solve its systematic positioning since it has all diagnostic characters of Axosuberites ; viz., i) compressed axial skeleton, ii) a well-differentiated plumoreticulated extra-axial skeleton, and iii) an ectosomal skeleton with smaller auxiliary styles ( Hooper 1996; Hooper & van Soest 2002). In addition, it is advice evaluate the possibility of C. (A.) retamalesi sp. nov. being closely related to C. (A.) rosita since it displays several morphological features present in the later.

Figures

FIGURE 7. Hymeniacidon hentscheli sp. nov., holotype (ZMH S 2343): A, styles in several size and some of them bearing an annular swell close to the base; B, detail of the extremities of styles (some smaller forms of them). Scale bars: A = 100 µm; B = 10 µm.

FIGURE 8. Clathria (Axosuberites) retamalesi sp. nov. A–D, holotype (MNRJ 20638). A, preserved specimen, with visible contracted surface membrane, and oscula; B, lateral view showing compressed longitudinal columns and overall cavernous architecture C, specimen in situ, arrow points to an oscule; D, freshly collected specimen; E, specimen in situ not collected; F, another specimen in situ not collected, arrow points to an oscule. Scale bars: A–C = 1 cm; D–F = 2 cm.

FIGURE 9. Clathria (Axosuberites) retamalesi sp. nov., holotype MNRJ 20638. A, extra-axial skeleton in transverse view; B, extra-axial skeleton in detail, with small ectosomal auxiliary styles (ect. aux.), smaller subectosomal auxiliary styles III (subect. aux.), and tracts of principal choanosomal styles reinforced by larger subectosomal auxiliary styles II, (cho. princ.); C, extraaxial skeleton in detail, showing bundles of ectosomal auxiliary styles; D, transverse section showing compressed choanosomal bundles of subectosomal principal styles and subectosomal auxiliary styles; E, detail of the compressed skeleton. Scale bars: A, D = 500 µm; B–C, E = 200 µm.

FIGURE 10. Clathria (Axosuberites) retamalesi sp. nov., holotype MNRJ 20638 (SEM of spicules). A, large styles (styles I); B, extremities of the large styles; C, larger intermediary styles (styles II); D, extremities of the styles II; E, smaller intermediary styles (styles III); F, extremities of the styles III; G, smaller styles (styles IV); H, extremities of the styles IV; I, large toxas (toxas I); J, intermediary category of toxas (toxas II); K, intermediary category of toxas (toxas III); L, small category of toxas (toxas IV); M, toxa II; N, toxa III; O, toxa IV. Scale bars: A, C, E, G = 100 µm; B, I–J = 50 µm; D, F, K–O = 25 µm; H = 5 µm.