Clathrina mutabilis, Klautau, 2017

Klautau, Michelle, 2017, Taxonomy and phylogeny of calcareous sponges (Porifera: Calcarea: Calcinea) from Brazilian mid-shelf and oceanic islands, Zootaxa 4311 (3), pp. 301-344 : 320-321

Clathrina mutabilis sp. nov.

( Figs 8 A–E; Table 9)

Diagnosis. Clathrina with a yellow cormus formed by large and loosely anastomosed tubes. Skeleton with two categories of triactines, one with cylindrical actines and blunt tips and the other, which is very rare, with conical actines and sharp or blunt tips.

Material examined (Two specimens, both from Fernando de Noronha Archipelago , Pernambuco State). Holotype: UFRJPOR 6526, Cagarras, 15 m depth, coll. F. Azevedo and G. Rodríguez, 27 June 2011 . Paratype: UFRJPOR 6528, Ressurreta, 7 m depth, coll. F. Azevedo and G. Rodríguez, 26 June 2011.

Etymology. From the Latin mutabilis (= changeable), for the inconstant presence of trichoxeas.

Colour. Yellow in life and white in ethanol.

Morphology. The sponge is delicate, fragile. The cormus is formed by large and loosely anastomosed tubes ( Fig 8 A). It was not possible to observe if water-collecting tubes are present because the holotype is very small and the paratype is fragmented.

Anatomy. Cells with granules were absent. The skeleton has no special organization and it is composed of two categories of triactines ( Fig 8 B). The most abundant has cylindrical actines, while the other, with strongly conical actines, is very rare. Most spicules are regular, but subregular spicules are also present. The holotype is full of trichoxeas that protrude through the surface, while the paratype does not have these spicules.

Spicules ( Figure 8 ; Table 9). Triactines I: Equiangular and equiradiate. These spicules are very rare. They have conical actines with sharp (in larger spicules) or blunt tips (in the smaller ones) ( Fig 8 C).

Specimen Spicule Length (µm) Width (µm) n

min mean sd max min mean sd max

UFRJPOR 6526 (H) Triactine I 56.7 69.8 7.9 91.8 8.1 8.4 0.6 9.5 20 Triactine II 94.5 121.7 13.1 148.5 6.8 8.1 0.4 9.5 30 UFRJPOR 6528 (P) Triactine I 54.0 74.0 15.2 108.0 8.1 9.5 0.9 10.8 19 Triactine II 94.5 121.5 15.1 151.2 8.1 9.1 0.8 10.8 30 Triactines II: Usually equiangular and equiradiate, but subregular spicules (those with one or even all three actines with different lengths) are also common. Actines are cylindrical, undulated, with blunt tips ( Figs 8 D, E)

Trichoxeas: Very thin, straight and long (figure not shown).

Ecology. Both specimens were found in shaded habitats (crevices) in depths varying from 7 to 15 m.

Distribution. Provisionally endemic to Fernando de Noronha Archipelago, off NE Brazil.

Remarks. Clathrina mutabilis sp. nov. can be characterized by its yellow colour associated with the presence of two categories of triactines, one with cylindrical actines and blunt tips and the other, which is very rare, with conical actines and sharp tips. The only other species of Clathrina with yellow cormus and two categories of triactines is C. insularis sp. nov. Both species are morphologically very similar, but they can be differentiated by the thickness of the actines of triactines I (conical actines), which are larger in C. mutabilis sp. nov. (Triactine I: 8.1 to 10.8 µm) than in C. insularis sp. nov. (Triactine I: 3.8 to 8.8 µm) ( Tables 7 and 9). Besides, in C. mutabilis sp. nov. the triactines I are very rare, while in C. insularis sp. nov. they are common, and the former became white in ethanol, while the latter turned brown. The molecular analysis also separated them as two species (see the molecular results).

In C. mutabilis sp. nov., trichoxeas may be present, but they are not a good taxonomic character for this species, as they are absent in some specimens. The value of trichoxeas as a taxonomic character was already discussed by Thacker (1908), Row (1909), and Klautau & Valentine (2003). Thacker (1908) mentioned the presence of trichoxeas in Ascandra atlantica ( Thacker, 1908) and suggested that this spicule category had no taxonomic value. He also proposed that A. tenuipilosa should be considered only a variety of A. canariensis based on the different amounts of trichoxeas ("hair-like oxea") in specimens from the Cape Verde Islands. Row (1909) and Klautau & Valentine (2003) considered that trichoxeas should be used as taxonomic characters. In our molecular tree the two specimens of C. mutabilis sp. nov., with and without trichoxeas, grouped as the same species with 0% of p distance (see below). Therefore, at least in the present species the presence or absence of trichoxeas should not be used as a taxonomic character. we suggest these spicules to be considered more carefully in the future as possibly non-diagnostic characters in Clathrina .

Figures

FIGURE 8. Clathrina mutabilis sp. nov. A—Holotype after fixation. B—Section. C—Triactines I. D, E—Triactine II.