Acarnus innominatus Gray, 1867

Nascimento, Elielton & Pinheiro, Ulisses, 2023, A new species of Acarnus Gray, 1867 (Porifera, Demospongiae, Acarnidae) from NE Brazil, Zootaxa 5293 (3), pp. 521-540 : 534-538

Acarnus innominatus Gray, 1867

( Figures 6–7 , Table 4)

Acarnus innominatus Moraes, 2011: 121 . Ugalde et al. 2021: 52 . Fig. 46

Examined Material. UFPEPOR 4329— Recife da Sereia (09°33’56”S 035º38’42”W, Alagoas State, Brazil), 2 February 2010, Col. Correia, M. D. UFPEPOR 4330— Recife da Sereia (09°33’56’’S 035º38’42’’W, Alagoas State, Brazil), 2 February 2011, Col. Correia, M. D. UFPEPOR 4331— Recife de Guaxuma (09º35’26”S 035º39’55”W, Maceió, Alagoas State, Brazil) 27 March 2009; Col. Correia, M. D. UFPEPOR 4335— Recife de Jatiúca (9°39’16.8”S 35°41’51.6”W, Maceió, Alagoas State, Brazil), 18 January 2011. Col. Correia, M. D.

Description ( Fig. 6A ). Thickly encrusting sponge, largest specimen (UFPEPOR 4335) with dimensions 6 x 4.5 x 1 cm (length x width x thickness). The surface is microhispid with spicules protruding externally and with subdermal gaps. Fragile and easy to break consistency. Color is beige in alcohol.

Skeleton ( Fig. 6B ). Ectosome is formed by paratangential tylotes arranged tangentially to the surface, with cladotylotes in tufts. The choanosomal skeleton consists of a reticulation of multispicular tracts of styles, echinated by cladotylotes particularly at nodes, and, microscleres scattered in the choanosome.

Spicules ( Fig. 7 ). (UFPEPOR 4335) Tylotes, terminally microspined (225– 252.9 –275/ 3– 3.5 –6 μm). Style (387– 422.5 –475/ 6– 18.2 –26 μm). Cladotylotes I, larger, smooth and straight to lightly curved shaft, well-defined rounded tyle base and cladome with long spines, length (237– 275.4 –300 μm), shaft width (6– 10.7 –13 μm), cladome width (22– 41.6 –32 μm). Cladotylotes II, smaller, shaft with recurved spines, rounded basal tyle (flattened), length (112– 125.5 –145 μm), shaft width (3– 3.8 –6 μm), cladome width (10– 13.5 –20 μm). Palmate isochelae, 13– 15.1 –20 μm. Toxas I, accolada (225– 358.3 –575 μm); Toxas II, thin, deeply curved, (112– 148.5 –212 μm); Toxas III, oxhorn (26– 45.7 –68 μm).

Distribution. Brazil: Fernando de Noronha and Atol das Rocas Island ( MORAES et al, 2003; MORAES, 2011); Alagoas State (present study). Floridan ( LAUBENFELS, 1936). Floridian; Greater Antilles ( PULITZER-FINALI, 1986). Southern Caribbean ( VAN SOEST, 1984). Southern Gulf of Mexico ( UGALDE et al, 2021). Southwestern Caribbean ( ZEA, 1987).

References: (1) van Soest, Hooper & Hiemstra, 1991; (2) Aguilar-Camacho, Carballo & Cruz-Barraza, 2013; (3) Zea, 1987

Ecology. Specimen UFPEPOR 4279 was growing on Ircinia felix ( Duchassaing & Michelotti, 1864) . Ophiuroids found on specimens UFPEPOR 4275 and 4276.

Remarks. The dimensions of the styles are very similar to those reported by Zea (1987) and Ugalde (2021). However, the specimens studied here are more robust when compared to the micrometries reported in Moraes (2011), 6– 18.2 –26 vs 2– 10 –12 μm (respectively). The color in vivo usually varies between orange and reddishorange ( Zea 1987; Ugalde 2021), but Moraes (2011) also recorded yellow. Acarnus innominatus can be confused in the environment with A. microxeatus sp. nov. due to the similarity in their external morphology. However, they differ by the presence of acanthoxeas and smooth microxeas in A. microxeatus sp. nov. This is the first record of the species on the Brazilian continental shelf (Alagoas State). The species distribution in the South West Atlantic was previously limited to the oceanic islands off Brazil.

Figures

FIGURE 6. Acarnus innominatus Gray, 1867 (UFPE 4279). A, Preserved specimen; B, thick section showing the ectosome and choanosome. Scale, A, 1 cm; B, 400 µm.

FIGURE 7. Acarnus innominatus Gray, 1867 (UFPE 4279). A, Style. B, Tylote. C, Detail of Style. D, Detail of tylote. E, Cladotylote I. F,F’ and F” growth forms of Cladotylote I. G, Cladotylote II. H, detail of the spined shaft of cladotylote II. I, Oxhorn toxa. J, Thin deeply curved toxa. K, Accolada toxa. L, Isochelae. Scale: A, B, E, G, 50 μm; C, D, F, F’, F”, H, L, 10 μm G, I, J, K, 20 μm.