Borojevia pirella, Van & De, 2018

Van, Rob W. M. & De, Nicole J., 2018, Calcareous sponges of the Western Indian Ocean and Red Sea, Zootaxa 4426 (1), pp. 1-160 : 34-36

Borojevia pirella sp.nov.

Figures 12a–b , 13a–e

Material examined. Holotype, RMNH Por. 11622a, Mauritius, Rodrigues, Passe Baladirou , 19.6683°S 63.46307°E, depth 12 m, scuba, coll. N.J. de Voogd, field nr. ROG023, 16 October 2016.

Paratype, RMNH Por. 11622b, Mauritius, Rodrigues, Passe Baladirou , 19.6683°S 63.46307°E, depth 12 m, scuba, coll. N.J. de Voogd, field nr. ROG023, 16 October 2016.

Description. Small pear-shaped cormus ( Figs 12a–b ) consisting of a mass of moderately tightly anastomosed tubuli separated by rounded or polyangular spaces. Color white, semitransparent. Size approximately 1.5 cm high, 1 cm in diameter. Tubuli approximately 0.2 mm in diameter. The narrow end is provided with an oscule of about 2 mm diameter, leading into a short water-collecting tube and a pseudoatrium. Preserved material consists of two specimens ( Figs 12a 1 , holotype, and 12b1, paratype), which collapsed to form flattened objects with soft consistency.

Aquiferous system. Asconoid.

Skeleton. The pseudoatrium has no special skeleton, it is merely a space between the anastomosed tubuli ( Fig. 13a ). The wall of these is thin, having one or two spicules comprising a mixture of triactines and tetractines, the latter with the apical actines protruding into the lumen of the tubuli.

Spicules. ( Figs 13b–e ) Triactines and tetractines of approximately the same size, no differentiated larger and smaller triactines are present.

Triactines ( Fig. 13b–c ) equiangular and equiradiate ( Fig. 13b ), with a tendency to become slightly sagittal, with a longer unpaired actine; occasionally triactines are irregular with one of the actines wavy and distinctly sagittal ( Fig. 13c ). Actine dimensions 51– 81.3 – 93 x 5 – 6.7 –8 µm.

Tetractines ( Fig. 13d–e ), similar in size and shape to the triactines ( Figs 13d ), with apical actines provided with three prominent conical spines in one verticil the position of which is matching the basal triradiate system ( Figs 13e ). Actines of the basal triadiate system 72– 85.7 – 96 x 5.5– 7.1 –8 µm, apical actines 31– 58.4 – 76 x 5 – 5.9 –7 µm.

Distribution and ecology. Rodrigues, Mascarene Islands, on coral reefs at 12 m depth.

Etymology. Pirella (L.), a feminine noun, meaning a small pear, referring to the habitus of the sponge.

Remarks. Despite the presence of a pseudoatrium and spined apical actines of the tetractines, molecular sequence data indicate clearly ( Fig. 2B ) that this species is closely related to Borojevia aff. cerebrum and ‘ Ascaltis OV-2012’, both reassigned to Borojevia (cf. Klautau et al. 2016), and not to Ascaltis reticulum . Voigt et al. ’s (2012) Australian species ‘ Ascaltis OV 2012’ has a clear pseudoatrium illustrated in their Supporting Fig. S1 inset J, but its sequence is grouped unequivocally among the Borojevia ’s in our Fig. 2B phylogeny. This justifies assignment of the present species to the genus Borojevia . The triactine complement of B. pirella sp.nov. does not contain any clear tripods, as is one of the additional features described for the genus Borojevia . The presence of the pseudoatrium is shared with the above described B. tubulata sp.nov., but apparently is absent in B. voigti sp.nov. and other Borojevia spp. The relationship with Ascaltis remains unresolved. The three prominent spines on the apical actines of the tetractines are a special feature of the new species. It is shared with the recently described Brazilian Borojevia trispinata Azevedo et al., 2017 . This is generally similar in spicule sizes, but on average has slightly smaller actines. The habitus differs in lacking a central pseudoatrium and being more irregular in shape, not pear-shaped.

We obtained sequences for Borojevia tubulata sp.nov. (both holotype and non-type Seychelles specimen, cf. above) and Borojevia pirella sp.nov. (both holotype and paratype). We compared these with two sequences of Red Sea specimens of Borojevia aff. aspina provided by Oliver Voigt in a separate restricted phylogenetic analysis. The aligned and trimmed sequences (length 426 sites) revealed that both identical sequences of B. pirella sp.nov. showed 4–5 sites difference with B. aff. aspina sensu Voigt et al. 2017 , 12–22 sites difference with B. tubulata sp.nov. (the higher difference being with the Seychelles specimen, as the holotype and Voigt’s Borojevia sp. have identical sequences). It may be concluded that the new species and Borojevia aff. aspina are more closely related than each of them with B. tubulata sp.nov.

Molecular comparison of B. pirella sp.nov. with the similar Brazilian species B. trispinata is complicated by differences in the target genes (our 28S vs Azevedo et al. 2017 ’s ITS). In a special effort, we obtained additional ITS data for B. pirella sp.nov. and aligned two ITS sequences (holotype and paratype, which appeared to be identical, not submitted to GenBank) with two sequences of B. trispinata downloaded from GenBank (UFRJPOR6419 and 6487, showing several site differences). A trimmed 792 sites alignment of the four sequences shows considerable differences (25 non–conserved sites differed between the two species, not counting a gap of 27 sites). Nevertheless, the morphological resemblance of the two species from the Western Indian Ocean and the Western Atlantic Ocean region is striking.

Figures

FIGURE 1. Marine Ecoregions in the Western Indian Ocean with localities (numbered blue squares) from where the studied calcareous sponges were obtained. 1, Israelian Red Sea, Gulf of Aqaba, 2, Saudi Arabian Red Sea, off Jeddah, 3, Eritrean Red Sea, Dahlak Archipelago, 4, Oman, Gulf of Arabia, 5, Maldives, 6, India, Lakshadweep, 7, Seychelles, Mahé region, 8, Seychelles, Amirantes, 9, Mayotte, 10, Mozambique Channel, 11, Mauritius, 12, Rodrigues, 13, South Africa, Kwazulu Natal, 14. South Africa, Port Elizabeth, 15. Nosy Be, Madagascar.

FIGURE 2. Maximum-likelihood tree based on analysis of sequences of the partial 28S gene (C2–D2 region, comprising 442 sites) of Western Indian Ocean Calcinea newly generated by the Naturalis Biodiversity Center and sequences additionally obtained from GenBank, the Sponge Barcode Project and from Oliver Voigt (München) from the Red Sea, Indonesia, Australia, and a few sequences from other parts of the world, to demonstrate the affiliation of the compared species. Please note that Arturia sequences do not appear in the same clade, indicating Arturia is non-monophyletic. Numbers at the root of clades are bootstrap values of 1000 replicates. Since the high number of sequences were difficult to read in detail, we subdivided the present tree in three detailed sections 2A, 2B, and 2C.

FIGURE 12. Borojevia pirella sp.nov., a, habitus in situ of holotype RMNH Por. 11622, from Rodrigues, the easternmost of the Mascarene Islands (photo N.J. de Voogd), a1, preserved holotype (scale bar = 1 cm), b, habitus in situ of paratype RMNH Por. 11622b (photo N.J. de Voogd), b1, preserved paratype.

FIGURE 13. Borojevia pirella sp.nov., holotype RMNH Por. 11622, from Rodrigues, a, light microscopic cross section of oscular region showing pseudoatrium and surrounding tubuli, b–e, SEM images of the spicules, b, regular triactine, c, rare sagittal irregular triactine, d, tetractines, e, details of apical actines of the tetractines showing characteristic verticil of three conical spines.