Acarnus innominatus Gray, 1867

Ugalde, Diana, Fernandez, Julio C. C., Gómez, Patricia, Lôbo-Hajdu, Gisele & Simões, Nuno, 2021, An update on the diversity of marine sponges in the southern Gulf of Mexico coral reefs, Zootaxa 5031 (1), pp. 1-112 : 52-53

Acarnus innominatus Gray, 1867

Tables 6, 7; Figs. 46A–I , 58A

Synonymy and references: Acarnus innominatus Gray (1867: 544) , and Muricy et al. (2011: 145); Fonteia anomala Gray (1867: 544) ; Acarnus carteri and Acarnus (Acarnus) innominatus : see references compiled in Muricy et al. (2011: 145).

Type locality. St. Vincent .

Material examined. CNPGG-2393, Hornos reef (19.19083°N, 96.11777°W), 2.7 m depth, coll. Diana Ugalde, 27 August 2018.

Description. Encrusting habit ( Fig. 58A ); overall size 4 × 1.5 × 0.6 cm. The surface is microhispid, with scattered pores and without visible oscules. Orange color in vivo, turning to beige when preserved in ethanol. The consistency is flexible.

Skeleton. Ectosome is formed by paratangential tylotes, with cladotylotes in tufts ( Fig. 46A ). The choanosomal skeleton consists of a reticulation of multispicular tracts of styles, echinated by cladotylotes ( Fig. 46C ). Microsclere; chelae and toxas; scattered throughout the choanosomal and ectosomal region ( Fig. 46B ).

Spicules. Megascleres: Styles stout, slightly curved and smooth ( Fig. 46D 1 ); 320– 364.3 (27.3)–410/20– 19.1 (3.8)–22.5 µm. Tylotes slender, straight and smooth, with microspined ends ( Figs. 46E–F ); 187– 223.5 (25.3)– 270/4.5– 5.3 (0.6)–6 µm. Large cladotylotes with a smooth shaft and smooth rounded basal tyle and apical clads ( Fig. 46G ); 180– 244.8 (20.4)–270/8– 10.8 (1.5)–14 µm, and cladome with 20– 36.4 (5.6)–40 µm in diameter. Small cladotylotes with a sparsely spined shaft, and smooth, rounded basal tyle and apical clads ( Fig. 46H ); n=5, 96– 100.8 (5.4)–110/2.2– 2.8 (0.3)–3 µm, and cladome with 10– 16 (4.7)–20 µm in diameter. Microscleres: Palmate isochelae ( Fig. 46D – 4 ); 10– 12.9 (1)–14 µm in length. Oxhorn-shaped toxas ( Fig. 46I ); 52– 66 (10.8)–80 µm in length. Wing-shaped toxas ( Fig. 46D – 2 ); 18– 34.3 (5.2)–40 µm in length. Accolada-shaped toxas ( Fig. 46D – 3 ); 170– 363 (153.7)– 600 in length.

Distribution. Mexico (current records), Bahamas, US (Florida), Cuba, other countries in the Caribbean Sea, and Brazil ( Zea 1987; Muricy et al. 2011).

Remarks. The present specimen conforms to A. innominatus well enough based on Hooper’s (2002) redescription of the type material. However, it differs in some aspects from Zea’s (1987) description of Colombian materials, where spicule measurements are often larger: styles 404–461 × 10–21 µm, tylotes 237–313 × 3.3–4.7 µm, large cladotylotes 233–299 × 8–10.9 µm, small cladotylotes 133–138 × 4.7 µm, and occurrence of five instead of four apical clads on cladotylotes. However, these traits are within the known variation of the species. Acarnus innominatus has a widespread occurrence in the Caribbean region, but this is its first record for the GoM.

Figures

FIGURE 1. Map of sampling localities explored in this study in the southern Gulf of Mexico. The localities include 16 coral reefs from Veracruz to Campeche Bank and one station in the Chelem lagoon in Yucatan Peninsula.

FIGURE 2. Agelas clathrodes (Schmidt, 1870) (CNPGG-2297), skeleton and spicules:A. transversal section of the skeleton; B. detail of the ectosomal region, upper side; C. verticillated acanthostyles. Scale bars: A = 500 µm; B = 100 µm; C = 50 µm.

FIGURE 3. Agelas conifera (Schmidt, 1870) (CNPGG-2364), skeleton and spicules: A. transversal section of the skeleton; B. detail of the ectosomal region; C. detail of the choanosomal region; D. verticillated acanthostyles. Scale bars: A = 1000 µm; B–C = 200 µm; D = 100 µm.

FIGURE 4. Agelas dispar Duchassaing & Michelotti, 1864 (CNPGG-1345), skeleton and spicules:A. transversal section of the skeleton; B. detail of the choanosomal region; C. verticillated acanthostyles. Scale bars: A = 500 µm; B = 100 µm; C = 50 µm.

FIGURE 46. Acarnus innominatus Gray, 1867 (CNPGG-2393), skeleton and spicules: A. transversal section of the skeleton, ectosomal region with scattered tylotes; B. transversal section of the skeleton, ectosomal region of the skeleton with cladotylotes; C. transversal section of the skeleton, choanosomal region; D. 1—style, 2—wing-shaped toxa, 3—acolada toxa and 4—isochelae; E. tylote; F. detail of the extremities of the tylote; G. large cladotylote; H. small cladotylote, the arrow pointing to the tip of a style; I. oxhorn-shaped toxa. Scale bars: A–B = 50 µm; C = 600 µm; D = 100 µm; E = 25 µm; F = 5 µm; G = 10 µm; H = 15 µm; I = 10 µm.

FIGURE 58. In situ photographs of species analyzed in the present study: A. Acarnus innominatus Gray, 1867 (CNPGG-2393); B. Monanchora arbuscula (Duchassaing & Michelotti, 1864) (CNPGG-2204); C. Strongylacidon bermuda (de Laubenfels, 1950) (CNPGG-2170); D. Desmapsamma anchorata (Carter, 1882) (CNPGG-2443); E. Iotrochota arenosa Rützler, Maldonado, Piantoni & Riesgo, 2007 (CNPGG-2422); F. Mycale (Mycale) laevis (Carter, 1882) (CNPGG-2273); F. Mycale (Arenochalina) laxissima (Duchassaing & Michelotti, 1864) (CNPGG-2267); H. Polymastia tenax Pulitzer-Finali, 1986 (CNPGG-22587); I. Scopalina ruetzleri (Wiedenmayer, 1977) (CNPGG-2183); J. Svenzea cristinae Alvarez, van Soest & Rützler, 2002 (CNPGG- 2474); K. Svenzea flava (Lehnert & van Soest, 1999) (CNPGG-2288); L. Svenzea tubulosa (Alcolado & Gotera, 1986) (CN- PGG-2272), surface detail zoomed in (arrow indicates white channels in the choanosomal region). Scale bars, A–L = 1 cm.