Clathrina soluta Fonseca, Cóndor-Luján & Cavalcanti, 2023

Clathrina soluta Fonseca, Cóndor-Luján & Cavalcanti, 2023 View in CoL

( Fig 13 View FIGURE 13 ; Table 9 View TABLE 9 )

Synonyms: Clathrina soluta, Fonseca et al. 2023: 13 .

Material examined: UFRJPOR 8806 , Escalvada Island , 7.9 m depth, 06.iv.2017, colls. A. Padua and C. Leal .

Diagnosis: “ Clathrina white to light beige, with slightly anastomosed tubes. Two types of triactines with sharp tips, one mostly cylindrical and the other, conical. Trichoxeas may be present” ( Fonseca et al. 2023).

Description: Cormus globular, formed by thin, irregular and loosely anastomosed tubes. Water-collecting tubes present. Colour beige alive and white after fixation ( Figs 13A, B View FIGURE 13 ). Consistency soft and compressible to the touch. Surface of the tubes smooth, although some trichoxeas protrude through the surface. Aquiferous system asconoid. Skeleton composed of two categories of triactines ( Figs 13C, D View FIGURE 13 ). Trichoxeas also present ( Fig 13E View FIGURE 13 ).

Spicules ( Figs 13E, F View FIGURE 13 ; Table 9 View TABLE 9 ).

Triactines I: Regular. Actines cylindrical to slightly conical, distally undulated, with sharp tips ( Fig 13F View FIGURE 13 ). Size: 85.1 (± 7.1)/ 6.8 (± 1.0) µm (N = 20).

Triactines II: Regular. Actines conical, straight, with sharp tips ( Fig 13F View FIGURE 13 ). Size: 68.3 (± 11.9) µm/ 7.6 (± 2.0) µm (N = 20).

Ecology: The Espírito Santo specimen was found in a crevice protected from sunlight. It is a shallow water species, found between depths of 1 and 7.9 m. It can be associated with calcareous algae ( Fonseca et al. 2023).

Distribution: Eastern Brazil ecoregion— Salvador, Bahia State (type locality; Fonseca et al. 2023); Guarapari, Espírito Santo State (present study).

Taxonomic remarks: The only divergences we could observe between C. soluta from Bahia and our specimen from Espírito Santo were slight differences on the size of the triactines I and II ( Table 9 View TABLE 9 ). Nevertheless, considering the standard deviation, those measurements overlap. Considering that our specimen matches greatly with the original description of C. soluta and it was recovered in the same clade with the types, we consider this difference a variation of the species. For that reason, the occurrence of C. soluta is expanded to the central part of the Eastern Brazil ecoregion.

Interestingly, C. soluta , based on the phylogenetic analyses, is closely related to Clathrina luteoculcitella Wörheide & Hooper, 1999 , from the Indo-Pacific. The C-LSU phylogeny could not distinguish both species and they were recovered in a polytomic branch ( Fig 2 View FIGURE 2 ). On the other hand, in the ITS analysis, C. luteoculcitella formed a single clade with Australian and Indonesian sequences. This clade was sister to sequences of C. soluta , where the sequence from Espírito Santo grouped with one paratype, and the other was at the base of the branch, not forming a clade with the other two sequences ( Fig 3 View FIGURE 3 ). It is possible that both markers do not have enough variability to properly recover two different clades of C. soluta and C. luteoculcitella , especially the C-LSU. Perhaps, including more sequences of C. soluta in the future will resolve this clade, forming a monophyletic group.

Morphologically, both species are very similar but have differences. Clathrina soluta presents loosely anastomosed tubes, while in C. luteoculcitella the anastomosis is dense. The skeleton composition is also different: C. luteoculcitella has a single category of conical triactines and C. soluta has two categories of triactines, one mostly cylindrical and more abundant, and the other conical. Hence, there is enough evidence to consider C. soluta and C. luteoculcitella as different species.