Haliclona (Halichoclona) plakophila, Vicente, Jan, Zea, Sven & Hill, Russell T., 2016

Vicente, Jan, Zea, Sven & Hill, Russell T., 2016, Sponge epizoism in the Caribbean and the discovery of new Plakortis and Haliclona species, and polymorphism of Xestospongia deweerdtae (Porifera), Zootaxa 4178 (2), pp. 209-233 : 219-220

Haliclona (Halichoclona) plakophila sp. nov.

( Fig. 4 ; Table 3 )

Xestospongia sp.; Vicente et al. 2014 (ecology and symbiosis).

Diagnosis. Haliclona (Halichoclona) bluish-white to translucent in color, thinly encrusting with occasional papillate morphology, so far exclusively found in epibiotic association with P. symbiotica sp. nov. Ectosome and choanosome consist of a subisotropic skeleton of oxeas.

Holotype and type locality: USNM 1254650 , Old Buoy, La Parguera, Puerto Rico (17.9552° N, - 67.0532° W), 32 m depth, coll. Jaaziel García Hernandez, October 15, 2015 . Paratype: PRAS 12 , and PRAS 22 , Old Buoy, La Parguera, Puerto Rico, (17.9552° N, - 67.0532° W), 32 m depth, coll. Jan Vicente, August 13, 2012 . Paratypes.

Description. Shape small, thinly (1–2 mm thick) encrusting veneer of tissue growing in separate patches on the surface of P. symbiotica sp. nov. ( Fig. 4 A). Some individuals developed papillated projections from the encrusting body ( Fig. 4 B). Irregular patches of H. plakophila sp. nov. occasionally form channels that burrow into P. symbiotica . Consistency compressible, slightly brittle, delicate, fragile and inelastic. Individuals are bluishwhite in vivo, becoming white or translucent after fixation. Ectosome and choanosome are of the same color. Surface is smooth and very thin. Oscules were not visible.

Skeleton. Ectosomal skeleton with an isotropic, paucispicular, tangential reticulation of oxeas, where 7–10 spicules meet at the nodes, forming 200 µm meshes. Subectosomal lacunae are present ( Fig. 4 C–D). The choanosomal skeleton is formed by a slightly disorganized isotropic reticulation of unispicular oxeas, where 7 spicules meet at each node, forming 100–200 µm meshes ( Fig. 4 D–E). The amount of spongin is very low throughout the ectosomal skeleton but more abundant in the choanosome ( Fig. 4 C–E). Spicules are not bound by spongin at the nodes.

Spicules. Oxeas, smooth, slightly curved at the center, fusiform, with hastate ends: 199– 229.5 (±11.5)–277 µm long by 3.5– 5.9 (±1.1)–8.7 µm in width ( Table 2 , Fig. 4 F).

Habitat and ecology. More than a dozen individuals were found always associated with P. symbiotica sp. nov. Free-living individuals of H. plakophila sp. nov. have not been found after extensive surveys throughout cryptic habitats of the Caribbean (see survey data in Vicente et al., 2014). Sponge pairs are found below 30 m in cryptic habitats growing on vertical walls, on the roof of overhangs and on the bottom of reef cave habitats. We are investigating multiple factors to determine why these sponges are always found associated with each other.

Distribution. Only observed at Old buoy, La Parguera, Puerto Rico. Possibly occur in other locations below 30 m along the southern continental shelf of Puerto Rico that offer similar cryptic habitats.

Etymology. The name plakophila describes the associated lifestyle with Plakortis symbiotica sp. nov., from phila meaning “living or growing by preference”.

Taxonomic remarks. Because of its relatively large oxea spicules (most above 200 µm), and like Xestospongia deweerdtae being epibiotic on Plakortis , this species was initially and preliminarily considered to belong to the genus Xestospongia ( Vicente et al. 2014) . But after molecular analyses (see below) and detailed examination of skeleton, we concluded that this species belongs to the genus Haliclona . Species within Haliclona can have a very simple as well as a more complex variety of morphological characteristics, making the classification of species in this genus very challenging. The genus encompasses over 420 species from which approximately 200 have been assigned to six subgenera [( Gellius Gray, 1867 , Halichoclona , Haliclona Grant, 1836 , Reniera , Rhizoniera Griessinger, 1971 , and Soestella De Weerdt, 2000 )] ( De Weerdt 2002; Van Soest et al. 2016). In addition, sequences of ribosomal internal transcribed spacer regions of marine haplosclerids show no diversity across species ( Redmond & McCormack 2009) and phylogenetic studies using several barcoding genes (cytochrome c oxidase subunit I, 18S and 28S rRNA) indicate that all subgenera of Haliclona are polyphyletic ( McCormack et al. 2002; Redmond et al. 2013; Redmond et al. 2011).

Despite the taxonomic challenges, a number of morphological characters from our new species are in agreement with the subgenus Halichoclona . The new species has a disorganized choanosomal skeleton without clearly distinguishable primary or paucispicular secondary lines. These skeletal properties distinguish it from the subgenera Gellius , Haliclona, Rhizoneria , which have ascending primary lines and a unispicular skeleton connecting secondary lines ( De Weerdt 2000, 2002). The absence of ascending primary lines conforms more to the subgenera Reniera and Soestella . However, the ectosomal skeleton of the new species does not form rounded meshes as observed in Soestella . The ectosomal properties of the new species also do not fit within Reniera , since it is irregular, not unispicular with isotropic reticulation and does not have spongin at the nodes. The ectosomal skeleton of the new species is subisotropic and paucispicular which conforms more to Halichoclona . It also has subectosomal spaces that allow it to be easily detachable from the choanosome. However, the low abundance of spongin in the new species makes it difficult to unquestionably classify it as Halichoclona , as most members of this subgenus only have spongin present at the nodes where spicules meet.

There are 35 species of Haliclona sponges throughout the TWA of which seven belong to the subgenus Halichoclona (Bispo et al. 2014; Muricy et al. 2015). There are two species described from mangrove habitats in La Parguera, Puerto Rico: H. (H.) magnifica ( De Weerdt et al., 1991) and H. (H.) perforata ( Pulitzer-Finali 1986) . H. (H.) magnifica is a massive sponge with thick walled tubes, a dense subisotropic reticulation of the ectosome that loosely overlays the choanosome composed of a subisotropic reticulation of oxeas ( De Weerdt et al. 1991). H. (H.) perforata is also massive but with friable consistency; the choanosomal and ectosomal skeletons are networks of single spicules connected by spongin at the nodes. The new species is not massive, has a subisotropic reticulation of spicules, but also a paucispicular reticulation at the ectosome without spongin at the nodes; these characters are not found in either of the two halichoclonids from Puerto Rico.

The other five H. ( Halichoclona ) species from the TWA are H. (H.) albifragilis ( Hechtel 1965) , H. (H.) dura ( Sandes et al., 2014) , H. (H.) lernerae ( Campos et al., 2005) , H. (H.) stoneae ( De Weerdt, 2000) , and H. (H.) vansoesti ( De Weerdt 2000) . H. (H.) vansoesti is also blue but forms thick cushions with large elliptical oscules, and has an easily detachable subisotropic ectosomal skeleton (De Weerdt et al. 1999). H. (H.) stoneae also forms thick cushions with large oscules and large oxeas ( De Weerdt 2000). H. (H.) lernerae is found in deep habitats off the coast of northern Brazil and exhibits a massive tube-like morphology ( Campos et al. 2005). H. (H.) dura is a thickly encrusting sponge with hard incompressible consistency ( Sandes et al. 2014). The massive, large oscule morphology of these sponges does not fit our new species. However, H. (H.) albifragilis shares the closest morphological characteristics to our new species. This sponge is small, thinly encrusting, without visible oscula and grows under coral rubble below 74 m in depth, with a subisotropic choanosomal and ectosomal skeleton ( De Weerdt 2000). This sponge however, lacks large subectosomal spaces and the new species exhibits large spaces underlying the ectosome. The new species also forms a thin veneer of tissue that exceeds 1 cm patches along the P. symbiotica sp. nov. body. There are also inconsistencies in the description of its color and there is no mention of H. (H.) albifragilis with papillated morphology. Phylogenetic analysis of partial sequences for 18S rRNA and cox genes from Haliclona spp. in GenBank supported that H. plakophila sp. nov. is a new species (results described below).

Figures

FIGURE 4 Maximum likelihood topology generated from partial sequences of cytochrome b oxidase (cob) (A) and cytochrome c oxidase subunit I (cox 1) (B) of the Homoscleromorpha of this study and from sequences downloaded from GenBank. Topology for both trees is rooted on the sponge Ectyoplasia ferox (Duchassaing & Michelloti, 1864) EU 23748.1 (Class Demospongiae, Order Axinellida). Bootstrap values less than 50 % were omitted from the trees. Coding following the species names refers to the museum catalogue number or collection location (PA-Panama, PR- Puerto Rico, BH-Bahamas) followed by lifestyle (AS-associated, FL-free-living). Species highlighted in bold represented sequences provided by this study.

Tables

TABLE 2. Spicule measurements of oxeas (length and width) of Haliclona plakophila holotype (h) and paratypes (p). Measurements are expressed as minimum – mean (± 1 standard deviation) – maximum. N = 50.

Specimen	Length (µm)	Width (µm)
Haliclona plakophila USNM1254650 (h)	199– 229.4 (±11.6)–256	3.6– 5.5 (±1.1)–8.7
Haliclona plakophila PRAS12 (p)	207– 230.0 (±10.1)–256	3.5– 6.4 (±1.1)–8.7
Haliclona plakophila PRAS22 (p)	207– 229.2 (±12.9)–277	3.6–6.4 (±1.0)–7.6