Ernstia variabilis, Klautau & Lopes & Guarabyra & Folcher & Ekins & Debitus, 2020

Klautau, Michelle, Lopes, Matheus Vieira, Guarabyra, Bruna, Folcher, Eric, Ekins, Merrick & Debitus, Cécile, 2020, Calcareous sponges from the French Polynesia (Porifera: Calcarea), Zootaxa 4748 (2), pp. 261-295 : 273-275

Ernstia variabilis sp. nov.

( Fig 5 , Table 5 )

Etymology. From the Latin “variabilis” (varied, changeable), due to its variable spicule shape.

Type locality. Rairoa , Tuamotu Islands, French Polynesia

Material examined. Holotype: UFRJPOR 8963 = MNHN-IP- 2018-56 — Raroia , Tuamotu Islands, Station trar08 (16°02.831’ S 142°25.701’ W), depth: 17 m, coll. M. Dumas, 05/XI/2018, P455- TRAR08 . Paratype: UFR- JPOR 8918 = MNHN-IP- 2018-59 — Raivavae , Australes Islands, Station ARAI07 (23°53.282’ S– 147°40.902’ W), depth: 6 m, coll. C. Debitus, 23/III/2013 , P455. Other material. UFRJPOR 8962 = MNHN-IP- 2018-71 — Raroia , Tuamotu Islands, Station TRAR02 (16°01.99’ S 142°25.565’ W), depth: 20 m, coll. CS. Petek , 04/XI/2018, P455- TRAR02 . UFRJPOR 8964 = MNHN-IP- 2018-42 — Raroia , Tuamotu Islands, Station trar09 (16°02.074’ S 142°25.701’ W), depth: 15 m, coll. V. Bouvot , 05/XI/2018, P455- TRAR09 . UFRJPOR 8965 = MNHN-IP- 2018- 52 — Raroia , Tuamotu Islands, Station trar12 (16°00.896’ S 142°25.323’ W), depth: 20 m, coll. M. Dumas , 06/ XI/2018, P455- TRAR12 .

Diagnosis. Yellow Ernstia with spherical cormus and thin, regular and tightly anastomosed tubes. A single long osculum atop of and atrial cavity. Skeleton composed of two categories of triactines and tetractines, mainly differentiated by shape and size. Aquiferous system solenoid.

Colour. Yellow alive and light brown in ethanol ( Fig 5A ).

Morphology and anatomy. Cormus spherical to subspherical formed by thin, regular and tightly anastomosed tubes ( Figs 5A, B ). There is usually one long apical osculum ( Fig 5C ), with a continuous endopinacoderm lining the atrial cavity. Aquiferous system solenoid. The skeleton is composed of two categories of triactines, two of tetractines, and trichoxeas ( Fig 5D ). The apical actines of the tetractines project into the tubes lumen and atrial cavity. The size of triactines II and tetractines II is different depending on the regions of the sponge: the spicules in the oscular region are noticeably larger than the spicules in the other parts of the body. Due to its transitional changes from osculum to choanosome, we consider it the same variable category. Tetractines occur in higher frequencies than triactines.

Spicules ( Table 5 )

Triactines I. Regular (equiangular and equiradiate) and smaller than triactines II. This category ressembles a young spicule on formation, but due to its relatively abundance, we considered it as a category apart. Actines are conical with sharp tips ( Fig 5E ). Size: 41.4/ 5.3 µm.

Triactines II. Regular (equiangular and equiradiate) and very abundant. Actines vary highly in shape and size. Spicules from the oscular region are usually cylindrical, ondulated and larger, with blunt tips. Spicules from choanosome are slightly conical to conical and straight, with blunt to slightly sharp tips ( Fig 5E ). Size: 94.3/ 6.9 µm.

Tetractines I. Regular (equiangular and equiradiate) and smaller than tetractines II. This category ressembles a young spicule on formation, but due to its relatively abundance, we considered it as a category apart. Actines are conical with sharp tips. The apical actine is cylindrical, the same size of basal actines, sharp, smooth, and frequently curved ( Fig 5G ). Size: 43.0/ 5.1 µm (basal actine); 39.1/ 4.1 µm (apical actine).

Tetractines II. Regular (equiangular and equiradiate) and very abundant. Actines vary highly in shape and size. Spicules from the oscular region are usually cylindrical, ondulated and larger, with blunt tips. Spicules from choanosome are slightly conical to conical and straight, with blunt to slightly sharp tips ( Fig 5F ). The apical actine is cylindrical, very long, sharp, smooth, and frequently curved ( Fig 5G ). Size: 90.6 / 7.0 µm (basal actine); 51.9/ 4.7 µm (apical actine).

Geographical distribution. Raroia, Tuamotu Islands and Raivavae, Australes Islands (present work).

Remarks. Ernstia variabilis sp. nov. formed a very well supported clade (100% bootstrap) with E. pyrum Sanamyan et al., 2019 and E. citrea Azevedo et al., 2017 . The three species are morphologically almost identical, all of them having a spherical yellow cormus formed by tight and regularly anastomosed tubes, long apical osculum and solenoid aquiferous system. Although in the original description of E. citrea it was said that this species has asconoid aquiferous system, we re-analised it and found the membrane of pinacocytes surrounding the atrium, proving that its aquiferous system is solenoid, as Sanamyan et al. (2019) had observed for E. pyrum .

We are describing E. variabilis sp. nov. as possessing two categories of triactine and two of tetractines. Re-analysing E. citrea , we think it has also these categories, though in the original description it was considered as having only one category of tri- and one of tetractines. The same can be considered for E. pyrum , if we take into account the size variation of the spicules and look at the original pictures (Sanamyan et al. 2019). Therefore, these three species can be distinguished only by slight differences in the size of their spicules.

Ernstia variabilis sp. nov. has spicules thicker than those of E. citrea [Holotype—Triactine: 81.3 (4.3)/ 10.4 (0.7), Tetractine: 82.4 (6.2)/ 10.4 (1.1)] (to compare with Table 5 ). Ernstia pyrum has a little thicker spicules [Ho-lotype—Triactine—surface and choanosome: 74.8 (14.4)/ 6.9, Triactine—atrial membrane: 83.7 (22.1)/ 7.9, Tri- actine—osculum: 103.9 (30.5)/ 6.9 (1.0), Tetractine—surface and choanosome: 73.6 (13.7)/ 6.6, Tetractine—atrial membrane: 94.1 (24.5)/ 7.4)] (to compare with Table 5 ). Hence, the three species are almost cryptic, however, we decided to distinguish them based on the molecular tree ( Fig 13 ). In the tree, although the three species form a very well supported clade (100% bootstrap), E. citrea and E. variabilis sp. nov. form two well supported clades (99% and 100% bootstrap, respectively).

As E. variabilis sp. nov. is the third species of the genus with solenoid aquiferous system, we proposed an emendation to the current diagnosis:

Calcinea in which the cormus comprises a typical clathroid body. A stalk may be present. The skeleton contains regular (equiangular and equiradiate) and/or sagittal triactines and tetractines. Tetractines are the most abundant spicules or occur at least in the same proportion as the triactines. Tetractines frequently have very thin (needle-like) apical actines. Diactines may be added. Asconoid or solenoid aquiferous system ( Klautau et al. 2013).

Figures

FIGURE 5. Ernstia variabilis sp. nov. (UFRJPOR 8963). A—Specimen in situ (UFRJPOR 8918). B—Fragment fixed in ethanol (arrow pointing to the osculum). C—Skeleton of the osculum. D—Skeleton of the anastomosed tubes. E—Triactine I. F—Triactine II. G—Tetractine I. H—Tetractine II. I—Apical actine of a tetractine.

FIGURE 13. ML phylogenetic tree of the ITS from Calcinea. Species sequences found in the present work are highlighted. Support values are shown at the nodes (Posterior Probability and Bootstrap values; <means value below 50%,—means node not present in the Bayesian phylogeny). Midpoint rooted tree.