Leucosolenia sebastianensis, Pereira & Azevedo & Hajdu & Cavalcanti & Klautau, 2025
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publication ID |
https://doi.org/10.11646/zootaxa.5688.1.1 |
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publication LSID |
lsid:zoobank.org:pub:05E2F9E1-3171-45F3-B0D1-1329D57EFCE6 |
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DOI |
https://doi.org/10.5281/zenodo.17017759 |
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persistent identifier |
https://treatment.plazi.org/id/03F4630B-FF9C-885E-3EAF-57F335166610 |
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treatment provided by |
Plazi |
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scientific name |
Leucosolenia sebastianensis |
| status |
sp. nov. |
Leucosolenia sebastianensis sp. nov.
urn:lsid:zoobank.org:act:
( Figs. 42–44 View FIGURE 42 View FIGURE 43 View FIGURE 44 ; Table 17)
Etymology: Named after its type locality, São Sebastião.
Type locality: Between Ponta do Baleeiro and Saco Grande , São Sebastião Channel, São Sebastião, São Paulo State, Brazil .
Type material: Holotype — MNRJ2975 View Materials , between Ponta do Baleeiro and Saco Grande, São Sebastião Channel, São Sebastião, São Paulo State, Brazil, depth 4 m, coll. E. Hajdu, 09/I/2000 . Paratypes —UFRJPOR9090, Parcel da Pedra Lisa , Búzios Island, Ilhabela, São Paulo State, Brazil, depth 7 m, coll. F. F. Cavalcanti, 01/XII/2008 . UFRJPOR9103, Serraria Islet , São Sebastião Island, Ilhabela, São Paulo State, Brazil, depth 9 m, coll. F. F. Cavalcanti, 04/XII/2008 .
Diagnosis: Leucosolenia with a basal reticulation of tubes bearing lateral diverticula, and some erect oscular tubes. The skeleton predominantly consists of triactines, along with tetractines, trichoxeas, and two size categories of curved, lanceolate diactines—one large and smooth, the other small and spined. The unpaired actine of the triactines and tetractines is usually longer than the paired ones.
Colour: White in life and in ethanol ( Fig. 42A, B View FIGURE 42 ).
Morphology and anatomy: Sponge with creeping basal tubes giving rise to erect tubes with simple apical oscula. The large basal tubes branch into numerous thinner, elongated tubes that terminate in dead ends, forming lateral diverticula ( Fig. 42A, B View FIGURE 42 ). The external surface of the tubes is slightly hispid due to trichoxeas and two types of diactines that protrude obliquely. The inner surface is also hispid, as the apical actines of the tetractines project into the lumen of the tubes. Aquiferous system asconoid.
The skeleton is composed of trichoxeas, two size categories of diactines, triactines and tetractines. The oscular skeleton consists of triactines and tetractines, in addition to a few small diactines ( Fig. 43A View FIGURE 43 ). Two categories of diactines and trichoxeas are scattered on the outer surface of the tubes, projecting obliquely and oriented in various directions. Small diactines are more abundant near the osculum and along the oscular tubes ( Figs. 43B View FIGURE 43 ; 44A, B View FIGURE 44 ), whereas larger ones are rarer, mostly found in the basal tubes ( Fig. 43C, D View FIGURE 43 ). The body wall skeleton is formed by triactines and tetractines arranged in parallel near the oscular region, with the unpaired actines pointing to the base of the sponge ( Fig. 43E View FIGURE 43 ). These spicules gradually become disorganised and slightly less sagittal towards the basal portion of the body ( Fig. 43F View FIGURE 43 ). They vary in thickness, with the most robust forms predominantly occurring on the outer surface of the tubes. Triactines are, in general, more abundant than tetractines, especially in the basal tubes ( Fig. 43F View FIGURE 43 ). The apical actines of the tetractines penetrate the lumen of the tubes and are curved towards the osculum.
The abundance of trichoxeas and diactines (of both categories) varies among the specimens. In UFRJPOR9103, which is more hispid than the other specimens, trichoxeas and large diactines are more abundant. Additionally, the robust forms of triactines and tetractines are more common in UFRJPOR9090, indicating variability also in their abundance across specimens.
Spicules ( Table 17):
Trichoxeas: Long and thin, cylindrical, sharp, usually broken.
Large diactines: Nearly straight for most of their length, but curved near the proximal tip. They gradually taper from half their length, which is the thickest part, towards the distal tip, which is lanceolate, smooth and sharp. Often the lance shape is less evident than in the small diactines ( Fig. 44C View FIGURE 44 ). Size: 241.7 (±17.5)/6.1 (±0.9) µm.
Small diactines: Slightly curved, with the proximal half usually thicker than the distal one. Spines are often present from half their length to the distal tip, which is lanceolate ( Fig. 44D View FIGURE 44 ). Size: 112.0 (±31.5)/4.3 (±1.1) µm.
Triactines and tetractines: Sagittal. Basal actines are conical to slightly conical, with sharp tips. The paired actines are slightly curved towards the unpaired one, which is straight. The unpaired actine is usually similar in length to or a little longer than the paired ones ( Fig. 44E, F View FIGURE 44 ). Near the osculum, they are strongly sagittal, with thinner actines. The apical actine of the tetractines is short, curved, conical, sharp, and thinner than the basal ones. Triactines size: paired—84.2 (±16.3)/8.6 (±1.9) µm; unpaired—88.5 (±15.7)/8.6 (±2.0) µm. Tetractines size: paired—83.3 (±13.3)/9.4 (±2.0) µm; unpaired—91.3 (±14.7)/8.9 (±1.9) µm; apical—34.4 (±5.0)/6.5 (±1.3) µm.
Ecology: The specimen MNRJ2975 was found growing among the branches of a brownish bryozoan colony, likely Bugula neritina ( Linnaeus, 1758) , covered by sediment particles. Associated organisms included bivalve molluscs and polychaete tubes. The specimen UFRJPOR9103 was collected in a burrow, sheltered from sunlight.
Geographic distribution: Southeastern Brazil ecoregion—São Sebastião Channel (São Sebastião), São Sebastião and Búzios Islands (Ilhabela), São Paulo State (provisionally endemic), Brazil.
Remarks: Among the 43 species of Leucosolenia ( De Voogd et al. 2025) , only two species share with our specimens a skeleton composed of triactines, tetractines, and two size categories of diactines, both lanceolate: L. botryoides ( Ellis & Solander, 1786) from the United Kingdom, and L. microspinata Longo, 2009 , from Italy. The former species is characterised by short, oval tubes and predominantly robust, “T-shaped” triactines and tetractines in the skeleton. According to Minchin (1904), L. botryoides also has two size categories of lanceolate diactines, but the smaller ones are straight. Therefore, L. sebastianensis sp. nov. differs from L. botryoides in both body shape and spicule morphology. Regarding L. microspinata , it can be easily distinguished from L. sebastianensis sp. nov. by its spherical body, composed of a dense reticulation of tubes, and by the presence of spines in the large diactines and in the apical actines of the tetractines.
It is worth comparing our specimens also with L. arachnoides ( Haeckel, 1872) , originally described from the Eastern Atlantic (unspecified locality), because it is the only species of the genus recorded on the Brazilian coast ( Borojević & Peixinho 1976; Muricy et al. 2011) and its taxonomic status is still doubtful ( Lavrov et al. 2024). Leucosolenia arachnoides ( Haeckel, 1872) was a variety of L. variabilis Haeckel, 1870 (published in 1872 as Ascandra variabilis var. arachnoides ) with the skeleton formed predominantly by small fusiform diactines, arranged in various directions, creating a spider-web-like layer on the surface of the tubes. It also bears large lanceolate diactines, triactines and tetractines, but in lesser abundance. Latter, Dendy & Row (1913) elevated this and other varieties of L. variabilis to the species level.
The Brazilian specimens identified as L. arachnoides by Borojević & Peixinho (1976) possess two categories of diactines, with the smaller ones forming a dense web that fills the spaces between the triactines and tetractines ( Borojević & Peixinho 1976), consistent with Haeckel’s (1872) original description. However, in these specimens, the unpaired actine of the triactines and tetractines appears either similar in length to or longer than the paired ones ( Table 17), differing from the original description and suggesting they may represent a distinct species. Nonetheless, our specimens differ from L. arachnoides sensu Borojević & Peixinho (1976) , as the small diactines in the latter are fusiform (see Borojević & Peixinho 1976, p. 1006, fig. 10). These differences further support the identification of the specimens from São Sebastião as a new species.
We agree with Lavrov et al. (2024) that scanning electron microscopy (SEM) is a crucial tool in Leucosolenia taxonomy, as the presence of spines in the spicules, which are not visible under light microscopy, appears to be more common than previously thought. In L. sebastianensis sp. nov., the spines on the small diactines were only observed after detailed inspection in SEM.
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