Acarnus toxeata Boury-Esnault, 1973

Nascimento, Elielton & Pinheiro, Ulisses, 2023, A new species of Acarnus Gray, 1867 (Porifera, Demospongiae, Acarnidae) from NE Brazil, Zootaxa 5293 (3), pp. 521-540 : 529-534

Acarnus toxeata Boury-Esnault, 1973

( Figs 4–5 , Table 3 )

Acarnus toxeata Boury-Esnault, 1973: 285 , fig. 44. Van Soest et al. 1991: 62.

Material examined. UFBA 2454 —Ilha Grande de Camamu (13°55’08S 38°59’59W, Camamu, Bahia State, Brazil), August 2004, Col. Andrade, W., 16m depth . UFBA 2456 —(13°56’00.4”S 38°59’29.6”W, off Marau , Bahia State, Brazil), August 2004, Col. Andrade, W., intertidal . UFBA 2700 —(13°32’31.56”S 38°35’27.96”W, off Cairu , Bahia State, Brazil), 28 August 2004, Col. Lopes, U. UFBA 2703 —Baía de Camumu (13°54’33.4”S 38°59’40.4”W, off Maraú , Bahia State, Brazil), 06 August 2005, Col. Guerrazzi, M. C. UFBA 2704 — Rio Maraú /Baía de Camamu (13°53’42.6”S 39°00’28.1”W, off Maraú, Bahia State, Brazil), 13 September 2003, Col. Guerrazzi, M. C. UFBA 2705 — Rio Maraú /Baía de Camamu (13°53’42.6”S 39°00’28.1”W, off Maraú, Bahia State, Brazil), 30 October 2004, Col. Guerrazzi, M. C. UFBA 3170 —(13°32’29.5”S 38°59’29.7”W, Cairu , Bahia State, Brazil), 25 April 2004, Col. Guerrazzi, M. C., 7,6 m depth.

Description ( Fig. 4A ). Thinly to thickly encrusting sponge. Surface hispid with spicules protruding externally. Fragile consistency, easy to break. No color recorded from the living materials, but pale to ochre when stored in ethanol.

Skeleton ( Fig. 4B ). Reticulate anisotropic choanosomal skeleton formed by ascending multispicular tracts of styles, interconnected by secondary multispicular tracts of styles. Choanosome with echinating cladotylotes I and II, and scattered microscleres.

Spicules ( Fig. 5 ). Terminally microspined tylotes with barely swollen heads, 212– 250.4 –313/ 2– 3.4 –5 μm. Styles long, lightly curved, with microspined, but also occasionally smooth heads, 364– 467 –555/ 5– 9.7 –15 μm. Cladotylotes I, larger, with few, if any, spines on the shaft (maximum 4 spikes), cladomes with 4–6 clads, length 162– 220.1 –252 μm, shaft width 2– 5.5 –7 μm, cladome width 15– 21.7 –27 μm. Cladotylote II, smaller, heavily spined (8–13 spikes), with 4–6 clads, length 83– 96.8 –141 μm, shaft width 1– 2 –4 μm, cladome width 5– 7.6 –12 μm. Isochelae, 10– 10.7– 12 μm. Toxas I, accolada (222– 435.6 –656 μm); Toxas II, thin deeply curved (50– 128.9 –313 μm); Toxa III, oxhorn (35– 55.2 –81 μm).

Distribution. Bahia State, Brazil.

Ecology. The specimens occur encrusting bivalve shells and rhodolites.

Remarks. This species was described by Boury-Esnault (1973) based on a unique specimen (holotype: MNHN DNBe. 1037) from Bahia State (off Abrolhos). This author described the external morphology, provided drawings of the spicule set, but did not describe the skeletal architecture. Boury-Esnault (1973) distinguished this species from the other congeners by having larger styles, two categories of spined cladotylotes and three categories of toxas. Later, Van Soest et al. (1991) reexamined microscopic slides of the holotype and characterized in more detail the spicules, but did not provide information on the choanosomal structure, and also stated that A. toxeata is characterized by presenting choanosomal styles, the larger cladotylotes, and the accolada toxa greatly exceeded

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

the size when comparing the dimensions of these spicules among the other species of the “tortilis” group. So, here we provide, for the first time, SEMs of the spicule set and a characterization of the skeletal arrangement of other specimens of A. toxeata .

Acarnus toxeata has cladotylotes with base curved spines, which are similar to A. deweerdtae , A. topsenti , A. oaxaquensis , A. sabulum . However, these species differ from A. toxeata by having one category of cladotylotes of A. topsenti (two in A. toxeata ), two categories of toxas in Acarnus oaxaquensis (three categories in A. toxeata ), smaller sized cladotylotes and toxas (at least 50% smaller) in Acarnus sabulum when compared to A. toxeata spicules. Acarnus deweerdtae is the most similar species to A. toxeata in having lightly spined larger cladotylotes and the retention of normal accolada toxa. However, it presents three categories of cladotylote (versus two of A. toxeata ), in addition to the absence of oxhorn toxa (present in A. toxeata ). The very evident difference between A. toxeata and A. claudei is the base of the cladotylote, while the former possesses rounded spines, the second has tyles flattened and is provided with lobes and blunt protrusions ( Van Soest et al. 1991). Acarnus bergquist is similar to A. toxeata by the presence of two categories of cladotylotes, but differs in lacking accolada toxa (present in A. toxeata ) and having only two categories of toxas (three categories in A. toxeata ). Acarnus tortilis has larger cladotylotes heavily spined along the shaft, but A. toxeata has larger cladotylote with few spines or a smooth shaft. The specimens analyzed in this study present dimensions of cladotylotes II, isochelae, thin deeply-curved toxas and accolada toxas similar to the original description. However, cladotylotes I, tylotes, oxhorn toxas are slightly smaller, but considered within the size range for the species ( Table 3 ). After micrometric analysis of the spicules, we observed that the size range of styles among the specimens of A. toxeata is very similar to other species from the “tortilis” group ( Table 3 ). In this sense, it is not reliable to consider the size of the styles as a diagnostic character. Therefore, we suggest that the diagnosis of the species is the presence of three distinct categories of toxas, where the maximum size of the accolada toxas exceeds 500 micrometers. From the study of these specimens, we expanded the bathymetric range of occurrence of the species, previous originally known to 50 m depth and here was found at 7 m and 16 m depth.

Figures

FIGURE 4. Acarnus toxeata Boury-Esnault, 1973 (UFBA 2705).A, Preserved specimen; B, thick section showing the ectosome and choanosome. Scale, A, 1 cm; B, 390 µm.

FIGURE 5. Acarnus toxeata Boury-Esnault, 1973 (UFBA 2705). A, Style. B, Tylote. C, Detail of Style. D, Detail of tylote. E, Cladotylote I. F, Cladotylote II. G, Isochelae. H, Oxhorn toxa. I, Thin deeply curved toxa. J, Accolada toxa. Scale: A, C, E, F, 50 μm; B, D, 10; G, H, I, J, 20 μm.