Tethya melinka Hajdu, Desqueyroux-Faundez, Carvalho, Lobo-Hajdu and Willenz 2013, sp. nov.
Creators: name: Hajdu, Eduardo
name: Desqueyroux-Faúndez, Ruth
name: Carvalho, Mariana De Souza
name: Lôbo-Hajdu, Gisele
name: Willenz, Philippe
Publisher: name: Zenodo
Year: 2013
Subjects: Biodiversity
Taxonomy
Animalia
Porifera
Demospongiae
Tethyida
Tethyidae
Tethya
Tethya melinka

description: Tethya melinka Hajdu, Desqueyroux-Faúndez, Carvalho, Lôbo-Hajdu and Willenz sp. nov.
(Figs. 2B, 3F–P; Tab. 3)
Tethya melinka Hajdu et al. (2009, nomen nudum) in Willenz et al. (2009: 114)
Type material. Holotype. IZUA-POR 141, south of Melinka (43°53’56.70”S – 73°45’16.70”W, Ascension Island, Guaitecas Archipelago, Chilean Patagonia), 10–16 m depth, coll. E. Hajdu, Ph. Willenz and G. Lôbo-Hajdu, 06 March 2005 —fragments from the holotype: MHNG 61492, MNRJ 8900 and RBINSc-IG 32232-POR 8900.
Comparative material. Tethya deformis (Thiele, 1898) — MHNG 10012 (Easter Island, det. DesqueyrouxFaúndez, 1990), microscopical preparations of dissociated spicules and thick sections.
Tethya papillosa (Thiele, 1905) — MHNG 10055 (fragment from holotype ZMB 3269), microscopical preparations of dissociated spicules and thick sections. Six additional specimens split among the MNRJ, MHNG and RBINSc collections.
Tethya sarai (Desqueyroux-Faúndez & van Soest, 1997) — MHNG 21024 (fragment from holotype USNM 37915), microscopical preparations of dissociated spicules and thick sections.
Diagnosis. Tethya melinka sp. nov. is the only Tethya in the south-eastern Pacific to possess three clearly distinguishable categories of micrasters, among which large choanosomal strongylasters reaching over 25 µm in diameter.
Description (Fig. 2B). Spherical to semispherical sponge (15–30 mm in diameter), with slightly to markedly conulose surface. Oscula not seen. Compressible consistency. Sponge shrinks upon collection and handling. Livecolour is light brownish-yellow (ochre), becoming lighter in ethanol.
Skeleton (Figs. 3F–G). Cortex clearly recognisable, divided in three layers, with a rather irregular contour. Micrasters form a dense mass on the outermost layer (70–150 µm thick), supported by a dense pack of megasters (300–600 µm thick). The inner layer bears a less dense arrangement of intermingled sphaerasters and micrasters (100–200 µm thick). This whole structure is supported and considerably pierced at lobules (200–300 µm in diameter) by radial multispicular tracts of megascleres (up to 440 µm in diameter), that may diverge brush-like (350–500 µm across) in the lobules, which are then markedly pierced. A palisade of slightly smaller megascleres (ca. 1200 µm thick) is situated in between the radial tracts of megascleres, also aiding in cortex support. Small subdermal spaces can be seen here and there.
Spicules (Figs. 3H–P). Megascleres, variably fusiform styles, apparently in a single size category, 505– 879.4 – 1252 µm long and 2.5– 10.0 –19 µm thick (H, I). Microscleres, megasters and micrasters. Megasters are a single category of smooth (oxy)spherasters, 15– 47 –63 µm in diameter (R/C 0.4–1.0; J); with oxyaster-like precursors (K). Micrasters in three categories: (I) large acanthostrongylasters (L), 18–32 µm in diameter, rare, occurring deeper in the choanosome; (II) intermediate sized acanthostrongylasters (M–O), 8–14.5 µm in diameter; (III) smaller acanthostrongylasters (‘tylasters’, P), 8.5–9 µm in diameter, rare.
Distribution and ecology. So far known only from 44ºS (Melinka, in the Guaitecas Archipelago), on nearly vertical rocky substrate, between 10 and 16 m depth, in close association with many other organisms such as anemones and encrusting sponges.
Etymology. The name ‘melinka’ is a noun in apposition, derived from the species’ type locality.
Remarks. The only species which might be confused with Tethya melinka sp. nov. in the field is Tethya papillosa (Thiele, 1905), which bears practically the same live-colour and quite comparable anatomic features (as briefly redescribed in Willenz et al. 2009). Both species can be distinguished by a series of characters needing special attention to be detected. First of these is habit. T. papillosa was found to be smooth all the time, while T. melinka sp. nov. is markedly conulose (projections may look lobular). The first may bear common biphid-rayed megasters, where, in general, several rays are biphid. These biphid-rayed megasters can nevertheless be quite rare, and, on top of that, a few ones (with one or two biphid rays) have also been spotted in T. melinka sp. nov., which renders the character somewhat suspicious. A varied set of micrasters is also found in both species. However, in T. papillosa these apparently pertain to a single plastic category and never grow beyond 18–20 µm (Willenz et al. 2009). whereas T. melinka has three clearly distinguishable categories of micrasters (acanthostrongylasters I, II and III) some of which reach 25–30 µm (more readily found deeper in the choanosome). The type of T. papillosa has been examined (MHNG 10055, microscopic slides made from ZMB 2233) and it contains megasters which are only rarely biphid, as well as micrasters which are consistently under 20 µm in length, and apparently also variable in morphology.
Table 3 lists the 25 species to which the new Tethya has been compared. As in the case of Suberites above, the criteria for election was geographical proximity and likelihood of historical affinity. Some of the species inserted are possibly widespread, and thus of dubious identity. Such is the case of T. aurantium, T. deformis and T. robusta. Eleven species clearly differ from the new one by the ability to produce much larger (> 2000 µm long) megascleres: T. amplexa, T. aurantium (Mediterranean neotype), T. bullae, T. californiana, T. ensis, T. fastigiata, T. ingalli, T. mexicana, T. paroxeata, T. robusta and T. strongylata. A few of these also have megasters which are either much smaller than those found in the new species (T. amplexa), or the opposite, much larger (T. aurantium, T. bullae, T. ensis, T. mexicana). Much larger megasters are an easy trait to spot and are present in further species among those which cannot be set apart through their megascleres. These include T. ovum and T. socius.
Tethya aurantium has been cited for New Zealand by Bergquist (1968) and Bergquist and Kelly-Borges (1991), but doubt on the identity of these specimens was brought up by Sarà (2002) and Sarà and Sarà (2004). On biogeographical grounds alone, the occurrence of any European species in the south-western Pacific is already highly improbable. Part of the material described by Bergquist (1968) and Bergquist and Kelly-Borges (1991) has already been assigned to T. burtoni by Sarà and Sarà (2004). For this reason, the comparison essayed here has taken the neotype description as a basis (Table 3).
Tethya bergquistae has been described with two categories of megasters, the larger of which with rays that can be curved, reduced or even absent, thus rendering the spicule sphere-like. The smaller category bears smooth rays, albeit apically spined. These traits make this species conspicuously distinct from T. melinka sp. nov.
Among the remaining species, there is a further group of New Zealand taxa which are highly unlikely to be present anywhere in the eastern Pacific, but which could nevertheless show close historical links to the new species (Sluys 1994, Hajdu & Desqueyroux-Faúndez 2008). In general these can only be set apart through micromorphological aspects of the micraster complement. The species which belong here are T. australis, T. burtoni, T. compacta, T. mortoni and T. stolonifera. None of these has the larger choanosomal strongylasters seen in the new species. Indeed, their micrasters are always smaller than 15 µm in diameter. T. australis and T. compacta have only a single category of micrasters, while T. mortoni and T. stolonifera have two or three, among which a category of microoxyspherasters as small as 3–5 µm. In both cases, these patterns differ markedly from what is seen in the new species. Nevertheless, the recognition of such subtle differences requires detailed SEM observations. T. burtoni has two categories of micrasters of overlapping dimensions, quite comparable to the intermediary and smaller categories reported upon here for the new species. Sarà and Sarà’s (2004) species has nevertheless a series of smaller traits which appear to us to set it confidently apart from the Chilean species, viz. (1) megascleres can be as large as 1800 µm long and 40 µm thick, (2) spherasters reach up to 80 µm in diameter and have more acute rays, and (3) the larger strongylasters have a neat tendency to have spines concentrated at the tips of their rays.
There are further three taxa which the new species needs to be set apart from: T. deformis, T. sarai and T. taboga. The first of these has been considered an “umbrella” for many Pacific species, and the need for a neotype has been stressed by Sarà and Sarà (2004). We opted here for a comparison with the species’ alleged eastern-most record, Easter Island (Desqueyroux-Faúndez 1990, material reexamined). The spicule set of this specimen (Fig. 4C) comprises megascleres only up to 1000 µm in length, frequently fusiform and slightly subtylote, megasters up to 46 µm in diameter, and micrasters with a well marked centrum, mostly spherostrongylasters or spherotylasters up to 18 µm in diameter. The megasters are spherasters to spheres, due to the very irregular rays, which are mostly just slightly curved, but may also be considerably reduced. The specimen analysed here (MHNG 10012) appears somewhat distinct from the one figured by Desqueyroux-Faúndez (1990), but both are sufficiently distinct from T. melinka sp. nov. The nearly homogeneous presence of a well-marked centrum (MHNG 10012) or the consistently rather smaller micrasters reported by Desqueyroux-Faúndez (1990), supposedly from the second specimen analysed, differ clearly from the micraster assemblage found in the Chilean material. The frequent presence of reduced, sphere-like megasters in MHNG 10012 also finds no parallel in the new species.
Desqueyroux-Faúndez and van Soest (1997) did not highlight holotype micrometries for Tethya sarai. As they had access to 42 specimens, we deemed it appropriate to reexamine specimen MHNG 21024, assigned as holotype. Nevertheless, the provision of a full set of statistically significant micrometries is out of scope. Megascleres can be as large as 2200 µm in length and 40 µm thick, and are frequently larger than 1600 µm. Megasters, mostly smooth spherasters, are as large as 105 µm in diameter, being frequently larger than 70 µm. Micrasters comprise a large proportion of oxyasters to strongylasters, with negligible centri and up to 25 µm in diameter, which may bear biphurcated rays. A second category of micrasters is composed of conspicuously acanthose strongylasters to tylasters with well-marked centri, eventually reaching 22 µm in diameter, but mostly under 17–18 µm. The traits outlined above from reexamination of T. sarai ’s holotype (Fig. 4D) make the species only rather distantly related to T. melinka sp. nov., which has considerably smaller megascleres and megasters, as well as a completely distinct set of micrasters.
It is important to point out that a few irregular strongyles were seen in the holotype of T. sarai, which brings Sarà et al. ’s (2000) T. strongylata closer to the former species. Nevertheless, T. strongylata appears to be devoid of the conspicuous oxyasters to strongylasters reported here from T. sarai.
Van Soest et al. (2011) extended T. sarai ’s distribution to Clipperton Island, not without hesitation. In spite of another large series of specimens in hands, a single set of micrometries and SEM images were provided, wherefrom it is impossible to clearly figure intraspecific variability. Notwithstanding, megasclere and megaster dimensions fell within the range shown by the new species, thus, further remarks appear warranted. In this case, distinction has to resort solely to micrasters. The specimens from Clipperton have choanosomal oxyasters, which are barely differentiated from cortical micrasters in size and shape according to Van Soest et al. (2011). This is hardly what is apparent from observation of their Figures 6E and 6F. Anyhow, the reported presence of tylasters up to 15 µm in diameter in Clipperton Tethya is an important point of distinction when contrasted to the greatest diameter of 9 µm seen in the new species. A further relevant contrast stems from the choanosomal oxyasters that can be much smaller (down to 9 µm) and rather less acanthose in Clipperton Tethya than they are in the new species. We consider these differences to settle the distinction of both species convincingly.
Finally, T. taboga, a species this far known only from western Mexico and Panama, can be differentiated from our new species by a series of traits: (1) possession of megascleres which are frequently strongylote and reach over 1600 µm in length, (2) megasters which can be larger than 70 µm in diameter, and (3) micrasters comprising abundant small, stout tylasters (as inferred from Green & Gómez’s 1986 SEM plate), as T. aurantium, wrongly misspelled as T. aurantia), which are only a minority component among the micrasters of T. melinka sp. nov.
Tethya asbestella is clearly unrecognisable, as Lamarck (1815) did not provide minimum information wherefrom the species’ spicule content could be inferred, neither was the specimen found in the MNHN Lamarck collection in a recent inspection (I. Domart-Coulon, pers. comm.). No new material of Tethya has since been reported from Argentina (Lopez-Gappa & Landoni 2005) or southern Brazil (Hajdu et al. 2004, Mothes et al. 2004), so no further comparison to the new species proposed is mandatory.
The new species is thus considered confidently differentiated and worth its status.
description: Published as part of Hajdu, Eduardo, Desqueyroux-Faúndez, Ruth, Carvalho, Mariana De Souza, Lôbo-Hajdu, Gisele & Willenz, Philippe, 2013, Twelve new Demospongiae (Porifera) from Chilean fjords, with remarks upon sponge-derived biogeographic compartments in the SE Pacific, pp. 1-64 in Zootaxa 3744 (1) on pages 9-20, DOI: 10.11646/zootaxa.3744.1.1, http://zenodo.org/record/5271084