Pinulasma fistulosum, Reiswig & Stone, 2013

Reiswig, Henry M. & Stone, Robert P., 2013, <strong> New glass sponges (Porifera: Hexactinellida) from deep waters of the central Aleutian Islands, Alaska </ strong>, Zootaxa 3628 (1), pp. 1-64 : 16-20

Pinulasma fistulosum n. sp.

( Figs. 7–9 , Table 4)

Synonymy. "Family Euretidae ; Genus nov., sp. nov." Stone et al., 2011: 19.

Material examined. Holotype: USNM# 1196550 , ROV 'Jason II' from RV ' Roger Revelle' , dive J2103, 04 August 2004, Amchixtam Chaxsxii , 21.7 km SE of Pochnoi Point, Semisopochnoi Island, Aleutian Islands, 51º47.872'N, 179º57.106'E, 1254 m, dry & ethanol ; Paratype: USNM# 1196551 , same dive and location, 1265 m, dry & ethanol .

Description. The overall body form of both specimens is a symmetrical high-aspect funnel; the holotype collected nearly intact, is 29.2 cm tall by 13.7 cm in diameter at the upper end (h/d = 2.14); the paratype, damaged in collection, was in situ, 20.3 cm tall and 13.1 cm in diameter (h/d = 1.55). Both were attached to exposed bedrock by moderate size basal discs at their narrow ends, the holotype on vertical surface and the paratype on horizontal surface; they extend vertically upward, expanding to a round terminal osculum ( Figs. 7A–D ). The body wall proper is fairly thin, 2.6–3.1– 4.2 mm (n = 9), and bears small, evenly-distributed hollow fistules projecting perpendicularly from the outer surface. The lumina of the fistules are open to the atrium ( Fig. 7G ), and when alive the distal ends of the fistules are closed by dense loose spicule pads ( Fig. 7E ) and are thus digitate in form. When loose spicules are lost through death or artificial removal, the remaining skeletal frameworks of fistules are distally open, suggesting to those viewing only dead skeletons that they could be parietal oscula; clearly they do not play that role when alive. In the holotype, the fistules are 7–16 – 24 mm tall (n = 18), 6–8– 12 mm in external diameter (n = 33), with the lumen diameter as 3.3–4.4– 6.3 mm (n = 14) at the atrial aperture and 2.5–3.2– 5.1 mm (n = 15) at the distal end (artificially opened). They tend to be distributed in horizontal rows and are spaced more closely horizontally (0.98 mm center to center) than longitudinally (1.4 mm). Many fistules remain as single digitate structures, but about half of them branch distally once or very rarely twice; the plane of branching is not oriented. Where adjacent branches come into contact, fusion of tissues and frameworks occur ( Fig. 7E ).

The external dermal surface is covered by a fine quadrangular lattice formed by loose pinular hexactins which spans across the underlying inhalant canals ( Fig. 7F ). The atrial surface of the main atrium and fistular lumina has similar pinular hexactins but here restricted to the ridges between exhalant canals and not forming a regular quadrangular lattice; the canal apertures are uncovered ( Fig. 7H ). The parenchymal skeletal framework of the main funnel wall is typically chonelasmatid in form, consisting mainly of a primary framework of elongate rectangular prismatic meshes, the long sides made by longitudinal strands (beam data given at the top of Table 4). End beams of the meshes are short and tend to be radially ranked, forming vertical septa ( Figs. 8A–E ), but not otherwise aligned. Thin cortical layers only one or two meshes in thickness, are appended to both surfaces of the primary framework; these lack longitudinal strands and instead have randomly oriented beams forming triangular meshes. Very shallow round epirhyses are formed in the dermal cortex ( Fig. 8F ) but aporhyses are not present in the thin atrial cortex ( Fig. 8G ). Longitudinal strands of the main body wall curve smoothly up and out into the framework of the fistules, retaining prismatic mesh form and ranking of the radial end beams ( Fig. 8B ). The thin cortical layers also extend smoothly out onto the surface frameworks of the fistules, but epirhyses are not formed in those surfaces. Most beams of the skeletal framework are smooth but some areas are sparsely ornamented by low rounded tubercles ( Fig. 8H ). Nodes are not swollen; spurs are long, rough and sharply pointed.

Megascleres are pinular hexactins, pentactins, regular hexactins, discoscopules, tyloscopules, tauactins, diactins and uncinates (dimensions given in Table 4). Pinular hexactins ( Fig. 9A ) cover both dermal and atrial surfaces of the main body funnel and fistules. They vary greatly in size and shape but all have a relatively long pinulus covered on its distal half by strong sharp obliquely-projecting thorns; the tangential and proximal rays are generally shorter than the pinular ray, straight, smooth, and cylindrical, bearing small sharp proclined denticles at the abruptly rounded or sharp pointed distal ends. Some hexactins have extremely long proximal rays. Pentactins ( Fig. 9B ) occur only in subatrial positions in the walls of both the main funnel and fistules, below the covering pinular hexactins. Tangential and proximal rays are straight, cylindrical and mostly smooth, bearing perpendicular and proclined spines at the distal abruptly rounded or pointed ends. A small knob occurs as a rudiment of the sixth distal ray. Regular hexactins ( Fig. 9C ) occur in subdermal and subatrial positions on both the main funnel and fistules; their rays are similar to those of the pentactins. Discoscopules ( Fig. 9D ) occur almost globally, echinating both dermal and atrial surfaces, as canalaria and as parenchymal spicules without association with surfaces. The neck is generally abruptly inflated from the shaft, often with four swellings, and carries 1–8, mostly 4–5, thin, straight or slightly out-curved tines ending in very small marginally toothed discs. The shaft tapers smoothly to a very sharp tip. All surfaces are finely spined but in a few the main part of the shaft appears smooth in SEM. Tyloscopules ( Fig. 9E ), over twice as large as the discoscopules, occur only echinating the highly restricted atrial surface of the fistules. The neck tapers smoothly from the shaft, without abrupt inflation; the 3–4–6 tines are straight, robust, and each ends in a swollen marginally-toothed cap that is not distinctly wider than the upper end of the tine shaft. They are also entirely rough and have a shaft tapering to a very finely pointed tip. Tauactins ( Fig. 9F ) occur only in the felt cover of spicules occluding the outer tips of the fistules. Their centrum bears three small knobs as rudiments of undeveloped rays. The three developed rays are straight, finely and sparsely spined, gradually tapering to more roughened distal parts ending in abruptly rounded or sharp tips. Diactins ( Fig. 9G ) occur only in a subatrial position of main funnel and fistule walls where they lie tangential to the surface. Their centrum bears four knobs as rudiments of undeveloped rays; the two developed rays are similar to those of the tauactins. Uncinates ( Fig. 9H ) echinate all surfaces of both the main funnel and fistules where they project vertically and obliquely beyond the pinular hexactins. They have well developed brackets and barbs, the latter of which extend parallel to the spicule surface, projecting very slightly at their tips. The tight feltwork of loose spicules covering the outer ends of the fistules consists of pinular hexactins with long proximal rays, hexactins, discoscopules, tauactins, diactins and uncinates; pentactins, tyloscopules and microscleres are absent from these structures.

Microscleres consist of discohexactins (75%), hemidiscohexasters (4%), oxyhexactins (20%) and hemioxyhexasters (<1%) (dimensions given in Table 4). All of these occur throughout the walls of the main funnel and fistules without restricted locations. Discohexactins ( Fig. 9I ) have straight rays covered in robust reclined thorns and end in discs with 5–8 marginal teeth. Hemidiscohexasters ( Fig. 9J ) are similar but have branching of only one or two rays resulting in two or very rarely three secondary rays; the very short primary rays are smooth. Oxyhexactins and hemioxyhexasters ( Fig. 9K ) are entirely smooth within the resolution limits of the SEM available. Rare branching of one or two rays results in hemioxyhexasters with short primary rays.

Etymology. The species name, fistulosum , refers to the fistules covering the outer surface of the specimens.

Remarks. The new species (and monospecific genus) shares the typical chonelasmoid primary layer of elongate prismatic meshes and aligned radial beams (septa) with the genera Chonelasma , Periphragella , Tretochone and Verrucocoeloidea . The main conflicts with placement of the new form within the genus Chonelasma are that all present members are plate- or frond-like in body form, completely lacking tubular projections of the body wall. While most Chonelasma species have surface pentactins, pinular hexactins occur in three species: C. doederleini Schulze, 1886 , C. hamatum Schulze 1886 , and C. chathamense Reiswig and Kelly, 2011 . It remains uncertain if C. doederleini is correctly placed since its body form is poorly known; it may eventually be moved to Pinulasma when better specimens are available. Periphragella has no members with pinular hexactins and the radial tubules are distally open by small parietal oscula, closed during life in the new form. The monospecific genus Tretochone has pinular hexactins in uncertain location but lacks external fistules and has a unique skeletal channel system of amarrarhyses, lacking in the new species. The likewise monospecific genus Verrucocoeloidea agrees with the new species in funnel form and presence of radial tubules, but those tubules are distally open when alive in V. burtoni and it lacks pinular hexactins. These basic differences prevent assignment of the new form to any of the presently known Chonelasmatinae . It is here designated as the only known member of a new genus Pinulasma , and named P. fistulosum .

Review of all video footage collected with the ROV 'Jason II' indicates that this is a common species, locally abundant in some areas and occurring singly or in small patches on bedrock, mudstone, boulders, and cobbles at depths between 773 and 2084 m. Juvenile Verrill’s Paralomis crabs ( Paralomis verrilli ) use the atrium as refuge habitat.

Figures

FIGURE 7. Pinulasma fistulosum n. gen., n. sp., specimens and surfaces. A. Frame grab from video footage of the holotype in situ before collection. B. Frame grab from video tape of the paratype in situ before collection. C-D. Both sides of the main parts of the dried holotype (C) and wet paratype (D) after collection. E. Closer view of the external fistules showing branching and fusion. F. Wet dermal surface of the holotype with transparent spicule lattice supported above inhalant canals. G. Closer view of atrial surface showing entrances to lumena of fistules. H. Atrial surface of wet holotype fragment showing uncovered apertures of exhalant canals.

FIGURE 8. Pinulasma fistulosum n. gen., n. sp., cleaned skeletal framework. A. Longitudinal section of body wall framework (LM). B. Longitudinal section through body wall and fistule; arrowhead shows location of Figure A (LM). C. Longitudinal section of body wall showing septa (SEM). D. Surface view of body wall and fistules (LM). E. Closer view of part of D showing septa (LM). F. Dermal surface of body wall, with slight dermal cortex and one shallow epirhysis; growth direction upward (SEM). G. Similar view of atrial surface (SEM). H. Close view of framework spurs and beams showing ornamentation (SEM).

FIGURE 9. Pinulasma fistulosum n. gen., n. sp., spicules (SEM). A. Dermal and atrial pinular hexactins, three whole variations and enlarged distal and tangential ray ends. B. Pentactin. C. Hexactin. D. Discoscopule, whole and enlarged head, shaft tip and tine end. E. Strongyloscopule, whole and enlarged head, shaft tip and tine end. F. Tauactin, whole and enlarged centrum and ray end. G. Two whole diactins with enlarged centrum and ray end. H. Uncinate, whole and enlarged central segment. I. Discohexactin, whole and enlarged ray tip and end disc. J. Hemidiscohexaster. K. Oxyhexactin and hemioxyhexaster. (All from holotype)