Grantessa tumida, Cóndor-Luján & Louzada & Hajdu & Klautau, 2018

GRANTESSA TUMIDA View in CoL SP. NOV.

( FIGS 24 View Figure 24 , 25 View Figure 25 ; TABLE 16)

Etymology: From the latin tumidus (=swollen), for the presence of subatrial and atrial spicules with distally swollen unpaired actines.

Type locality: Daai Booi , St. Willibrordus, Curaçao .

Material examined: Holotype. UFRJPOR 6701, Daai Booi , St. Willibrordus, Curaçao (12°12′43.12″N, 69°05′8.42″W), 3–5 m depth, coll. B. Cóndor-Luján, 18 August 2011 GoogleMaps . Paratypes. UFRJPOR 6695, Hook’s Hut , Willemstadt, Curaçao (12°07′18.94″N, 68°58′11.46″W), 6.3 m depth, coll. B. Cóndor-Luján and G. Lôbo-Hajdu, 17 August 2011 GoogleMaps . UFRJPOR 6766, Sunset Waters , Soto, Curaçao (12°16′01.58″N, 69°07′44.85″W), 13.1 m depth, coll. B. Cóndor-Luján, 23 August 2011 GoogleMaps .

Diagnosis: Grantessa with a solitary cylindrical body and a hispid surface. Distal cones decorated by tufts of diactines are evident. The tubar skeleton is exclusively composed of triactines. The atrial skeleton is composed of one category of triactines and two categories of tetractines (I and II). The unpaired actines of the atrial triactines and of atrial tetractines I are distally swollen. The apical actine of tetractines I is curved and of tetractines II is straight.

Colour: Beige in life and beige to white in ethanol ( Fig. 24A, B View Figure 24 ).

Morphology and anatomy: This species has a tubular to sac-shaped body with an apical osculum surrounded by a crown of trichoxeas. The holotype (UFRJPOR 6701) is the largest specimen and measures 0.5 × 0.2 × 0.1 cm ( Fig. 24A View Figure 24 ). The surface is smooth to the touch although diactines protrude through the surface. The consistency is compressible. The aquiferous system is syconoid with elongated choanocyte chambers ranging from 75.0/13.0 to 87.0/20.0 µm.

Skeleton: The osculum is surrounded by a crown of trichoxeas supported by T-shaped triactines and rare tetractines ( Fig. 24C View Figure 24 ). The skeleton is typical of the genus. The cortical skeleton is composed of diactines and triactines ( Fig. 24D View Figure 24 ). The diactines are arranged in tufts, to which trichoxeas can be added. Rare diactines penetrate obliquely the choanosome but do not reach the atrium. The triactines are tangentially positioned with the paired actines laying tangentially to the subcortical region ( Fig. 24D View Figure 24 , black arrow). The subcortical skeleton is composed of pseudosagittal triactines ( Fig. 24D View Figure 24 , white arrow) with the longest paired actine (actine 1) penetrating the choanosome. The tubar skeleton is articulated, composed of several rows of triactines ( Fig. 24E View Figure 24 , arrow) with the unpaired actine pointing to the cortex. The subatrial skeleton is composed of triactines ( Fig. 24F View Figure 24 , white arrow). The atrial skeleton is composed of one category of triactines and two categories of tetractines (I and II, black arrow and arrowhead, respectively, in Fig. 24F View Figure 24 ). Atrial triactines and tetractines I have the unpaired actine tangential to the atrium, supporting it. Tetractines I and II have their apical actine penetrating the atrial cavity ( Fig. 24F View Figure 24 , arrow and arrowhead, respectively).

Spicules: Diactines. Fusiform with tips usually sharp ( Fig. 25A View Figure 25 ). Size: 108.0–637.2/5.4–16.2 µm. Cortical triactines. Sagittal. Actines are conical with sharp tips. The paired actines are less straight than the unpaired one ( Fig. 25B View Figure 25 ). Size: 48.6–102.6/4.1–8.1 µm (paired actine), 51.3–175.5/4.1–8.1 µm (unpaired actine). Subcortical triactines. Pseudosagittal. Actines are conical with sharp tips. One of the paired actines is shorter and more curved than the other. The unpaired actine is straight ( Fig. 25C View Figure 25 ). Size: 67.5–145.8/4.1–5.4 µm (paired actine 1), 51.3–113.4/2.7–5.4 µm (paired actine 2), 54.0–129.6/4.1–8.1 µm (unpaired actine). Tubar triactines. Sagittal. Actines are conical, slightly curved with sharp tips. The paired actines have almost the same size or one of them is shorter than the other one. The unpaired actine is straight and usually longer than the paired ones ( Fig. 25D View Figure 25 ). Size: 48.6–121.5/5.4–8.1 µm (paired actine), 72.9–205.5/5.4–8.1 µm (unpaired actine). Subatrial triactines. Sagittal. Actines are slightly conical with sharp tips. The unpaired actine is straight and longer than the paired ones. The paired actines are inwardly curved ( Fig. 25E View Figure 25 ). Some paired actines with different lengths in the same spicule were also found. Size: 40.5–108.8/4.1–6.8 µm (paired actine), 35.1–243.0/4.1–8.1 µm (unpaired actine). Atrial triactines. Sagittal. Actines are conical with sharp tips. The unpaired actine is elongated and swollen at the distal part ( Fig. 25F, G View Figure 25 ). Size: 89.1–162.0/4.1–8.1 µm (paired actine), 159.3–283.5/5.4–8.1 µm (unpaired actine). Atrial tetractine I. Sagittal. Actines are conical with sharp tips. The unpaired actine is elongated and it is swollen at the distal part ( Fig. 25H, I View Figure 25 ). The apical actine is curved, with the base being much thicker than the tip, which is blunt. Size: 94.5–151.2/4.1–8.1 µm (paired actine), 162.0–283.5/5.1–8.1 µm (unpaired actine), 13.5–43.2/4.1–5.4 µm (apical actine). Atrial tetractines II: Sagittal. Actines are conical with sharp tips. The unpaired actine is longer than the paired ones ( Fig. 25J, K View Figure 25 ). The apical actine is straight. Size: 78.3– 148.5/4.1–5.4 µm (paired actine), 108.0–280.8/5.4–8.1 µm (unpaired actine), 21.6–97.2/4.1–6.8 µm (apical actine).

Ecology: The specimens were found underneath coral boulders at depths varying from 5 to 13 m.The paratype UFRJPOR 6695 was covered with sediment when collected. No associated organisms were observed.

Geographical distribution: Southern Caribbean (provisionally endemic to Curaçao, present study).

Molecular analysis: The sequences of the holotype (UFRJPOR 6701) and of the paratype UFRJPOR 6695 of Grantessa tumida sp. nov. formed a monophyletic clade with high support (pp = 1, b = 100, Fig. 15 View Figure 15 ) and 100% of genetic similarity (0% of p distance).

Grantessa tumida sp. nov. did not group with the other Grantessa species included in the phylogenetic tree, G. aff. intusarticulata (Carter, 1886) , which may indicate the non-monophyly of this genus. On the other hand, G. tumida sp. nov. evidenced a closer affinity to Sycon ciliatum as they clustered together (pp = 1, b = 71). The p distance between these two species was 5.5%.

Taxonomic remarks: Among the 28 valid species of the genus Grantessa , only G. ramosa ( Haeckel, 1872) from South Africa and G. tenhoveni Van Soest & de Voogd, 2015 from Indonesia have atrial spicules with swollen unpaired actine as also observed in G. tumida sp. nov. Nonetheless, the skeleton of our new species differs from G. tenhoveni , as it bears neither subatrial tetractines nor atrial tetractines with long apical actines (660.0–960.0 µm) as described for the Indonesian species. Therefore, G. ramosa is the most similar species to G. tumida sp. nov.

Grantessa ramosa View in CoL was originally described by Haeckel (1872) and redescribed by Borojevic (1967). Although the specimens described in both studies are very similar, it is possible that they belong to different species as they differ mainly in the composition of the cortical skeleton and spicule dimensions ( Tables 16 and 17). Consequently, we compared the specimens from Curaçao with each description separately, i.e. G. ramosa sensu Haeckel (1872) View in CoL and G. ramosa sensu Borojevic (1967) View in CoL .

Grantessa ramosa sensu Haeckel (1872) View in CoL is a ramified sponge with a smooth surface, whereas G. tumida View in CoL sp. nov. forms a single tube with hispid surface. According to Haeckel’s description, the cortical diactines of G. ramosa View in CoL are distally swollen (see Plate 54, fig. 1s), located perpendicularly to the surface (close to each other) and are not supported by cortical triactines. In contrast, in G. tumida View in CoL sp. nov. cortical diactines are fusiform, arranged in tufts and supported by cortical triactines. Moreover, Haeckel (1872) mentioned that the apical actines of the atrial tetractines were ‘ Nagethier-Schneidezahns ’ (thick and sharp-pointed as shown in Plate 54, fig. 1a), whereas in G. tumida View in CoL sp. nov., the apical actine of the atrial tetractines can be curved (tetractines II) or straight (tetractines I). Regarding spicule dimensions, although almost all the spicule categories of G. ramosa sensu Haeckel (1872) View in CoL match those of G. tumida View in CoL sp. nov. ( Tables 16 and 17), diactines are shorter in the former (60.0–80.0 µm) than in the latter (108.0–637.2 µm).

Differing from G. tumida View in CoL sp. nov., G. ramosa sensu Borojevic (1967) View in CoL is a sponge with variable external morphology, being ramified or solitary. Although very similar in skeletal composition, the spicules of these two species are not identical. Borojevic (1967) described one category of atrial tetractines; however, in figure 14 (p. 206) it is possible to distinguish two categories of atrial tetractines: one with very long unpaired actine (left, fig. 14g) and another with short unpaired actine (right, fig. 14g). In G. tumida View in CoL sp. nov., both categories of atrial tetractines (I and II) have long unpaired actine (see Spicules section). Furthermore, compared to G. ramosa sensu Borojevic (1967) View in CoL , almost all the spicule categories have thinner actines in G. tumida View in CoL sp. nov.: cortical triactines (8.0–12.0 µm vs. 4.1–8.1 µm), subcortical triactines (14.0–18.0 µm vs. 2.7–8.1 µm), tubar triactines (14.0–18.0 µm vs. 5.4–8.1 µm), subatrial triactines (9–14 µm vs. 4.1–8.1 µm), atrial triactines (8.0–10.0 µm vs. 4.1–8.1 µm) and atrial tetractines (4.1–8.1 µm vs. 25.0 µm).

In both descriptions of G. ramosa, Haeckel and Borojevic agreed that the distal cones are not visible macroscopically, whereas, in G. tumida sp. nov., short distal cones are evident probably due to the longer diactines of the new species.

Although the analysed specimens from Curaçao did not cluster with the other Grantessa species in the C-LSU phylogeny ( Grantessa aff. intusarticulata ), we identified these specimens as Grantessa following the morphological classification of Systema Porifera ( Borojevic et al., 2002). Grantessa aff. intusarticulata and G. tumida sp. nov. have many similarities (syconoid aquiferous system, articulated choanoskeleton and pseudosagittal subcortical triactines); however, only G. tumida sp. nov. has radial tubes decorated with tufts of diactines resembling distal cones. Whether this difference has phylogenetic signal in Grantessa or not should be tested in further molecular studies. The addition of the sequence from the type species of the genus, G. sacca , in future phylogenetic analyses would help to understand the phylogenetic affinities within Grantessa .