Sycetta papillata, Mattedi & Cavalcanti, 2024

Mattedi, Alice & Cavalcanti, Fernanda F., 2024, Sycetta papillata sp. nov. (Porifera, Calcarea): the first record of Sycetta to the Southwestern Atlantic Ocean, Zootaxa 5481 (3), pp. 353-362 : 354-360

publication ID	https://doi.org/ 10.11646/zootaxa.5481.3.4
publication LSID	lsid:zoobank.org:pub:2400DCEF-B04F-480A-B248-038A27C8601E
DOI	https://doi.org/10.5281/zenodo.12758851
persistent identifier	https://treatment.plazi.org/id/CE6E879D-E12C-FF94-FF6C-FA81FB8CA045
treatment provided by	Plazi
scientific name	Sycetta papillata
status	sp. nov.

Treatment

Sycetta papillata sp. nov.

( Figs 1–3 View FIGURE 1 View FIGURE 2 View FIGURE 3 ; Tables 1 View TABLE 1 , 2 View TABLE 2 )

Diagnosis: Sycetta with only one category of diactines and atrial region formed exclusively by tetractines.

Etymology: The name is related to the body formed by papillae (i.e., the radial tubes separated from each other).

Type material: UFBAPOR 1917 [Holotype. Camaçari , Bahia, Brazil (12°46'40" S, 38°07'50" W); collected by W.Andrade; 28/XI/1995; 25 m depth]. GoogleMaps UFBAPOR 1922 [Paratype. Camaçari , Bahia, Brazil (12°45'19" S, 38°06'07" W); collected by W. Andrade; 28/XI/1995; 25 m depth] GoogleMaps .

Additional material: UFBAPOR 1645 [ Stella Maris , Salvador, Bahia, Brazil (12°59'00" S, 38°12'00" W); collected by E. Hajdu; 21/I/1997; 0.5 to 1.0 m depth]. GoogleMaps UFBAPOR 1918 [ Camaçari , Bahia, Brazil (12°46'40" S, 38°07'50" W); collected by W. Andrade; 28/XI/1995; 25 m depth]. GoogleMaps UFBAPOR 1948 [ Camaçari , Bahia, Brazil (12°46'40" S, 38°07'50" W); collected by W. Andrade; 28/XI/1995; 25 m depth]. GoogleMaps UFBAPOR 1919 [ Camaçari , Bahia, Brazil (12°46'16" S, 38°07'01" W); collected by W. Andrade; 28/XI/1995; 25 m depth]. GoogleMaps UFBAPOR 1921 [ Camaçari , Bahia, Brazil (12°46'16" S, 38°07'01" W); collected by W.Andrade; 28/XI/1995; 25 m depth]. GoogleMaps UFBAPOR 1924 [ Camaçari , Bahia, Brazil (12°46'16" S, 38°07'01" W); collected by W. Andrade; 28/XI/1995; 25 m depth]. GoogleMaps UFBAPOR 1923 [ Camaçari , Bahia, Brazil (12°46'06" S, 38°07'15" W), collected by W. Andrade; 28/XI/1995, 25 m depth]. GoogleMaps UFBAPOR 1947 [ Camaçari , Bahia, Brazil (12°43'17" S, 38°02'19.92" W); collected by W. Andrade; 28/XI/1995; 25 m depth]. GoogleMaps UFBAPOR 5022 [ Camaçari , Bahia, Brazil (12°45'19" S, 38°06'07" W); collected by W. Andrade; 28/XI/1995; 25 m depth] GoogleMaps .

Type locality: Camaçari , Bahia, Brazil [Marine ecoregion: Northeastern Brazil ( Spalding et al. 2007)] .

TABLE 1 View TABLE 1 . (Continued)

Description: Colour in alcohol is beige. The holotype (UFBAPOR 1917) measures 0.8 x 0.2 cm (height x width), while the other specimens vary from 0.5 to 1.3 cm in height x 0.2 to 0.3 cm in width ( Figs 1A, B, C View FIGURE 1 ). It has a cylindrical shape with terminal osculum surrounded by an incipient membrane ( Figs 2A, B View FIGURE 2 ). There is no fringe of trichoxeas, and this membrane is the only ornamentation of the osculum ( Figs 1 View FIGURE 1 , 2A, B View FIGURE 2 ). The external surface has numerous radial tubes separated from each other, which has been called conical diverticula ( Dendy 1893) or papillae—nomenclature adopted here ( Haeckel 1872; Van Soest & De Voogd 2015) ( Figs 1 View FIGURE 1 , 2A View FIGURE 2 ). In some cases, small diactines can be observed protruding from the surface ( Figs 1E View FIGURE 1 , 2B View FIGURE 2 ), and these spicules are more easily visualized in tangential sections of the body surface. Some specimens (UFBAPOR 1917, UFBAPOR 1922, and UFBAPOR 1923) have small extensions at the base, resembling a very incipient stalk or stolon ( Figs 1F View FIGURE 1 , 2A View FIGURE 2 ). The aquiferous system is syconoid ( Fig 2C View FIGURE 2 ).

The skeleton is articulated, and in most sections, the radial tubes are separated from the proximal region ( Fig 2C View FIGURE 2 ). As typical of Syconidae , there is no cortex. The diactines are not organized in tufts, they occur individually. In UFBAPOR 1947, these diactines extend from the distal cone to the tubar region and, in the holotype, they can be visualized tangentially ( Fig 2B View FIGURE 2 ). In other specimens, they were observed only in dissociated spicules’ slides. In addition to diactines, the distal cone contains triactines and tetractines, which in some cases have the unpaired actine perforating the surface ( Fig 2D View FIGURE 2 ). The tubar skeleton is formed by triactines and tetractines ( Figs 2D, E, F View FIGURE 2 ), and these spicules are larger and have different shapes from those present in the distal cones (see below for spicules’ description). They point the unpaired actine towards the distal region ( Figs 2D, E, F View FIGURE 2 ). At the wall of the radial tubes, tetractines point their apical actines into the lumen ( Figs 2D, E View FIGURE 2 ). Some of these apical actines have an abrupt fold at the tip ( Fig 2D View FIGURE 2 ). Both in the distal cones and the tubar skeleton, tetractines were observed with the apical actine displaced from the center of the basal actines ( Figs 2E, F View FIGURE 2 ). More internally, in the subatrium, there are triactines and tetractines arranged with the unpaired actine facing the distal region ( Figs 2G, H View FIGURE 2 ). These spicules can be recognized by their obtuse unpaired angle and by their curved paired actines (see below). Tetractines are frequent in the holotype but were rarely observed in the paratype. The atrial region is the only one that does not have triactines, being formed exclusively by tetractines. Their apical actines face the interior of the atrium, giving the atrial surface a hispid appearance ( Figs 2G, H View FIGURE 2 ).

Spicules ( Figure 3 View FIGURE 3 , Table 1 View TABLE 1 )—The measurements presented here are an average of the measurements of the holotype and paratype.

Diactines: Straight or slightly curved, with sharp tips [130—304.1 (±126.2)—525.8/ 4.3—6.3 (±1.5)—9.8 μm].

Triactines of the distal cones: Sagittal.Actines are slightly conical with sharp tips. Paired actines curve downward in a "U" shape. Unpaired actine is straight and larger than the paired ones [paired: 41.1—75.2 (±16.1)—105.6/ 2.9—5.7 (±1.3)—8.3 μm; unpaired: 47.8—103.3 (±32.8)—168.4/ 3.5—5.9 (±0.8)—7.7 μm].

Tetractines of the distal cones: Sagittal. Actines are slightly conical, with sharp tips. Paired actines curve downward. Unpaired actine is straight and slightly larger or the same size as the paired ones. The apical is short, and it may be displaced from the center of the basal actines [paired: 47.3—80.3 (±14.3)—103.6/ 4.4—6.0 (±0.9)—8.2 μm; unpaired: 60.1—98.1 (±26.2)—188.9/ 4.3—6.1 (±0.8)—7.6 μm; apical: 11.0—17.2 (±4.2)—27.9/ 2.4—4.4 (±1.1)—7.0 μm].

Triactines of the tubes: Sagittal. Actines are slightly conical, with sharp tips. The paired actines are long and straight, sometimes slightly curved downward in direction to the atrial region. In some cases, one of the paired actines may be shorter than the other. The unpaired angle increases as it approaches the atrial region. The unpaired actine is long and straight [paired: 55.3—83.9 (±12.3)—110.0/ 3.2—6.1 (±1.3)—9.1 μm; unpaired: 73.6—128.6 (±21.6)—170.7/ 4.3—6.2 (±0.8)—7.9 μm].

Tetractines of the tubes: Sagittal. Actines are slightly conical with sharp tips. The paired actines are long and straight, and the unpaired is larger. Apical actines are long and curved, and in some spicules, an abrupt fold at the tip of the apical can be observed [paired: 58.6—97.1 (±21.5)—150.5/ 3.6—5.4 (±1.0)—7.4 μm; unpaired: 77.7—131.9 (±28.6)—208.6/ 3.9—6.0 (±0.8)—7.6 μm; apical 12.2—29.8 (±11.4)—49.1/3.4—5.2 (±1.0)—7.3 μm].

Subatrial triactines: Sagittal. Actines are cylindrical with sharp tips. The paired ones are curved toward the distal region, but in some cases, they are straight and short. The unpaired angle is wide. The unpaired actine is long and straight, directed toward the distal cone [paired: 29.3—46.7 (±9.4)—66.9/ 2.8—5.0 (±1.1)—7.1 μm; paired: 48.9—99.9 (±28.2)—162.3/ 3.7—5.5 (±0.8)—7.6 μm].

Subatrial tetractines: Sagittal. Actines are cylindrical with sharp tips. The paired actines are slightly curved. The unpaired actine is straight and long. The apical actines are short and straight [paired: 33.5—57.1 (±16.8)— 93.0/2.9—5.1 (±1.3)—7.5 μm; paired: 51.8—104.5 (±27.4)—168.1/ 3.4—5.8 (±1.0)—7.4 μm; apical: 11.0—14.4 (±4.7)—22.5/4.0—4.9 (±1.5)—7.5 μm].

Atrial tetractines: Sagittal. Actines are slightly conical with sharp tips. The paired actines are long and slightly curved. Unpaired actine is long and straight, while apical actine is long and curved [paired: 53.9—112.0 (±28.5)— 174.5/ 3.1—6.0 (±1.3)—7.9 μm; unpaired: 87.2—136.9 (±27.1)—194.3/ 4.6—6.3 (±0.9)—8.1 μm; apical: 12.7— 29.3 (±12.2)—58.2/ 3.6—5.0 (± 0.9)—6.6 μm].

Remarks: To date, Sycetta consists of nine species. Comparing Sycetta papillata sp. nov. with these species reveals that the composition of its skeleton is unique for the genus: unlike any other Sycetta species, S. papillata sp. nov. has diactines, triactines and tetractines in the distal cones, triactines and tetractines in the tubar and subatrial regions, and an atrial skeleton composed only of tetractines ( Table 2 View TABLE 2 ). This composition also differs from Sycon tuba Lendenfeld 1891 and Sycon conulosum Cóndor-Luján, Louzada, Hajdu & Klautau, 2018 , which have apparent separate distal cones, as tetractines are absent from their tubar and subatrial skeletons. Moreover, in these species the atrium is surrounded by both triactines and tetractines.

The main differences between the new species and others species of Sycetta lie in the presence of a single category of diactines and the composition of the atrial skeleton ( Table 2 View TABLE 2 ). Sycetta antarctica Brøndsted, 1931 may be considered the most similar to the new species, but it has two diactines’ categories and the atrial skeleton is made from triactines and tetractines ( Table 2 View TABLE 2 ).

Among the species previously described within the genus, only two are found in the Atlantic Ocean— Sycetta perforata ( Haeckel, 1872) in the Tropical Atlantic and S. conifera ( Haeckel, 1870) in the Temperate Northern Atlantic. Two species are reported for the Arctic— S. asconoides Breitfuss, 1896 , and S. sagitta de Laubenfels, 1942 , and one for the Southern Ocean— S. antarctica . The remaining species are distributed across various realms as follows ( Spalding et al. 2007): Central Indo-Pacific ( S. vinitincta Van Soest & De Voogd 2015 ), Temperate Northern Pacific ( S. quadriradiata Hôzawa, 1929 ), Western Indo-Pacific ( S. sagittifera Haeckel, 1872 ), and Temperate Australasia ( S. primitiva Haeckel, 1872 ). More details on the distribution of these species are provided in Table 2 View TABLE 2 .

Another noteworthy factor is the depth in which these species are found. While complete sampling data are lacking for some of them, there are records of S. conifera occurring between 60 and 100 meters ( Haeckel 1870; Burton 1963), and S. sagitta at a depth of 100 meters ( Burton 1963). Sycetta asconoides has been observed at greater depths ranging from 100 to 256 meters ( de Laubenfels 1942; Burton 1963), whereas S. antarctica is, so far, the species recorded at the greatest depths within the genus, found between 350 and 385 meters ( Brøndsted 1931; Burton 1963). Apart from Sycetta papillata sp. nov., which inhabits depths ranging from 0.5 to 25 meters, only S. vinitincta has been documented in shallow waters, specifically at a depth of 2 meters ( Van Soest & De Voogd 2015).