Stelodoryx strongyloxeata, Lehnert & Stone, 2020

Lehnert, Helmut & Stone, Robert P., 2020, Three new species of Poecilosclerida (Porifera, Demospongiae, Heteroscleromorpha) from the Aleutian Islands, Alaska, Zootaxa 4851 (1), pp. 137-150 : 146-148

Stelodoryx strongyloxeata n. sp.

( Figs. 6 & 7 )

Material examined. Holotype ZSM20200329 , intact specimen, stored in ethanol, collected by R. Clark with a research survey bottom trawl from the FV Vesteraalen; 31 May 2002, 83 m depth, haul station 1033, Unimak Pass , eastern Aleutian Islands (54° 24.61’ N, 165° 31.26’ W) . Paratype ZSM20200330 , intact specimen, stored in ethanol then dried (sample retained in ethanol), collected by R. Clark with a research survey bottom trawl from the FV Sea Storm; 27 July 2002, 150 m depth, haul station 162, southern Seguam Pass , central Aleutian Islands (52° 0.07’ N, 172° 33.30’ W). Water temperature = 4.2 °C .

Description. The holotype ( Figs. 6A & B ) is a thickly flabellate sponge, probably on a short stalk. The fan is somewhat folded ( Fig. 6A ), and so presenting a larger and a smaller fan. The two (“inner”) surfaces facing each other differ from the “outer” surfaces: outer surfaces have numerous oscules that are mostly on short elevations but sometimes flush with the surface. Inner surfaces with much fewer oscules. The larger part of the fan is 20 x 16 cm with a somewhat variable thickness of 0.8–1.4 cm. The smaller part of the fan measures 11 x 11 cm. The distal parts of both fans end in fingerlike projections, 1.5–3.5 cm in length. The holotype was likely growing on a short stalk ( Fig. 6B ), 1.9 cm in height and 1.8 cm in diameter. There is no other sign of attachment. The paratype ( Fig. 6C ) is smaller and consists of finger-like projections that possibly also merge into a fan when growing larger. The surface is velvety, the color is light to dark brown. The consistency is elastic, compressible, difficult to tear. Oscules have diameters of 1–3 mm and their elevations are up to 8 mm in height.

Skeletal architecture. The choanosome consists of a reticulation of polyspicular tracts forming almost quadratic meshes in the interior ( Fig. 6D ). Closer to the surface approximately 1 mm below the surface, the ascending polyspicular tracts branch off side-tracts that are connected by poly- to paucispicular tracts. Thus towards the surface the mesh becomes narrower ( Figs. 6D & E ). Deeper inside the sponge fibers form quadrats in the choanosome with side-lengths of 450–550 µm, at a distance of approximately 1 mm from the surface and less, quadrats have sides of 150–250 µm ( Figs. 6 D-E). Tracts of choanosomal strongyloxeas reach the surface with pointed ends of the strongyloxeas facing out and are mostly not or, only slightly, protruding above the surface ( Fig. 6F ). Bundles of style-like tornotes, again with points facing out, reinforce the choanosomal tracts at the surface ( Fig. 6F ). Ectosomal spicule bundles do not form a closed palisade but leave open spaces in between tracts and tornote bundles are filled in with numerous isochelae.

Spicules. Choanosomal strongyloxeas ( Fig. 7A ) measure 245–290–318 x 15–27– 35 µm, ectosomal style-like tornotes ( Fig. 7B ), sometimes with slightly microspined heads ( Fig. 7C ), 142–170–205 x 4 –9– 10 µm, large isochelae ( Fig. 7D ), 67–88– 96 µm, and small isochelae ( Fig. 7E ), 23–29– 40 µm.

Discussion. This species has a reticulate skeleton consisting of a reticulation of tracts which is typical for the genus. Choanosomal styles are the common spicule category of the genus. Stelodoryx strongyloxeata n. sp. differs from all congeners in its peculiar fusiform strongyloxeas that additionally differ in size from the choanosomal styles of all other Stelodoryx of the region. The strongyloxeas are rather short, only the longest strongyloxeas have some overlap with the shortest styles of other congeners ( S. siphofuscus Lehnert & Stone, 2015 , S. flabellata Koltun, 1959 , S. lissostyla Koltun, 1959 and S. pluridentata Lundbeck, 1905 ) and they are the thickest choanosomal spicules known in the genus Stelodoryx . The ectosomal tornotes of S. strongyloxeata are style-shaped, a character only shared with S. siphofucus which has longer style-shaped tornotes and from which it differs in several other characters listed below. Dimensions of the two categories of isochelae additionally separate the new species from other congeners.

Differences with other congeners are: Stelodoryx flabellata Koltun, 1959 has longer ectosomal tornotes, choanosomal microspined styles and strongyles that are longer but thinner than the strongyloxeas of S. strongyloxeata , and only one category of isochelae. Stelodoryx lissostyla Koltun, 1959 has longer ectosomal tornotes, choanosomal styles that are longer but thinner than the strongyloxeas of S. strongyloxeata , and the two size categories are both of different sizes. Stelodoryx oxeata Lehnert et al., 2006 has longer ectosomal tornotes, choanosomal oxeas that are longer than the strongyloxeas of S. strongyloxeata , three categories of isochelae of different sizes, and centrotylote sigmas. Stelodoryx pectinata Topsent, 1904 has longer ectosomal tornotes, choanosomal acanthostyles that are longer, and two size categories of isochelae of different sizes. Stelodoryx pluridentata ( Lundbeck, 1905) has longer ectosomal tornotes, longer choanosomal spicules that are styles, and only one category of isochelae. Stelodoryx procera Topsent, 1904 has longer ectosomal tornotes, two categories of choanosomal spicules that are styles (both longer than the strongyloxeas in S. strongyloxeata ), and only one category of isochelae. Stelodoryx toporoki Koltun, 1958 has longer ectosomal tornotes, longer choanosomal spicules that are styles, two categories of anchorate isochelae, the larger category longer. Stelodoryx vitiazi Koltun, 1955 has longer ectosomal tornotes, choanosomal acanthostyles that are longer than the strongyloxeas of S. strongyloxeata , and only one category of isochelae.

Stelodoryx mucosa Lehnert & Stone, 2015 has larger ectosomal tornotes, choanosomal acanthostyles that are longer, and only one category of isochelae. Stelodoryx siphofuscus Lehnert & Stone, 2015 is tube-shaped versus a thickly flabellate sponge in S. strongyloxeata , shares the style-shaped ectosomal tornotes but these are longer in S. siphofuscus , shares choanosomal strongyloxeas that are longer but only half the thickness of the strongyloxeas in S. strongyloxeata . Stelodoryx jamesorri n. sp. has ectosomal tylotes that are longer and thicker, choanosomal strongyloxeas that are longer and thicker and less fusiform, and two categories of isochelae with different size ranges.

Etymology. The species is named for its peculiar strongyloxeas.

Figures

FIGURE 6. Stelodoryx strongyloxeata n. sp. A, Holotype. “Folded” fan, inner surface, between the two parts with fewer oscules, outer surface (on the left) with numerous oscules. B, Backside of holotype showing only larger part of the fan with many elevated oscules on the outer surface. Remaining part of broken stalk at lower left. C, Paratype. D, Choanosomal skeleton consists of a reticulation of polyspicular tracts forming quadratic meshes. The meshes become smaller and more dense closer to the surface. The polyspicular tracts end in brushes of style-shaped tornotes at the surface, visible as a darker band on upper end. E, Close-up view of polyspicular, quadratic meshes near the surface, visible at the right. F, Ectosomal tornotes and points of strongyloxeas protruding above surface. Ascending polyspicular tracts are sometimes connected by single spicules.

FIGURE 7. Stelodoryx strongyloxeata n. sp. A, Choanosomal strongyloxeas. B, Ectosomal style-shaped tornotes. C, Microspined head of ectosomal tornote. D, Large isochelae. E, Small isochelae.