Pinulasma bowiensis, Reiswig, 2018

Reiswig, Henry M., 2018, Four new species of Hexactinellida (Porifera) and a name replacement from the NE Pacific, Zootaxa 4466 (1), pp. 124-151 : 128-131

Pinulasma bowiensis n. sp.

( Figs 2 , 3 & 4 , Table 2)

Material examined. Type material: Holotype: RBCM 016-00230-001, FV Pacific Viking, Set 18 ,0 8 June 2016, Bowie Seamount, 180 km W of Haida Gwaii (Queen Charlotte Islands), British Columbia, Canada, 53°21.1’N, 135°35.6’W, 476– 988 m.

Species diagnosis. Pinulasma with fistulous outgrowths of the dermal body wall that branch and anastomose. Dermalia and atrialia are microspined pentactins. Other spicules include tyloscopules, uncinates, two types of discohexasters and oxyhexasters.

Description. Body form of the holotype is not precisely known since it was broken during collection and recovered as about 60 hard but fragile fragments ranging in size from 2 to 121 mm ( Fig. 2A ); it was most likely a large cone or plate. The atrial surface of the largest fragment is rather smooth with large evenly-spaced openings ( Fig. 2B ), 4.7– 6.9 –9.2 (n = 15) mm in diameter and 15– 20 –25 (n = 21) mm center-to-center spacing, extending vertically outwards into diverticula of the dermal surface. On the dermal surface, those atrial apertures extend into hollow dermal processes that extend vertically outwards 2–3 cm from the dermal surface and bend rather abruptly to extend parallel to the body wall and anteriorly as evidenced by orientation of dictyonal skeleton ( Figs 2A, C– D ).The dermal processes are somewhat flattened laterally and they often assume wall- or ridge-like form containing the round tubular component distally. The outer horizontal components of dermal processes commonly branch and anastomose; their distal walls often remain incompletely fused ( Fig. 2C ) or, if completely fused they bear small apertures as parietal oscula along their outer surfaces and at their terminal ends ( Figs 2D–F ), with diameters of 0.6– 2.7 –6.0 (n = 23) mm. The fragments preserved in alcohol are white.

The dictyonal framework of the fragments, and thus the entire specimen, is delicate and fragile; it consists of two components, the main wall of the specimen and walls of the dermal processes ( Figs 3A–B ). The dictyonal framework of the main wall consists of three layers, a primary unchannelized layer with elongate meshes and nodes and short beams lined up in-register to form transverse septa or ranks ( Figs 3C–E ). The thick dermal cortex layer of the main wall is channelized by cylindrical epirhyses ( Fig 3D ). The atrial layer is generally too thin to show channels but its channelization cannot be ruled out with the little information provided by this single specimen. In contrast to the main wall framework, that of the dermal processes shows a distinctive difference. About one cm outwards on the dermal processes the skeleton shifts from a 3 layered form with septate middle layer to a 1-layered framework without a distinct differentiated primary layer, without septa and with meshes of fairly equal sides ( Figs 3B, F ). Dictyonal spurs are rough and lanceolate ( Fig. 3G ) and the framework is inconsistently ornamented with small spines, some areas being smooth ( Fig. 3H ).

Megascleres (for measurements see Table 2) consist of a pentactine dermalia and atrialia, tyloscopules, small oxyhexactins and uncinates. Dermalia and atrialia ( Fig. 4A ) are regular pentactins that are similar in form and size, but those of the outer surfaces are slightly larger. They are entirely and evenly covered by fine spines. Tangential ray- ends are round, proximal ray ends are bluntly pointed. The tyloscopules ( Fig. 4B ) are likewise similar on both sides of the body wall; all encountered have 4 tines ending in spherical tips. Some have a smooth shaft, some are entirely covered by fine spines but all heads are covered by small reclined spines. Small oxyhexactins ( Fig. 4C ) which occur loose as single spicules or grouped by fusion as small groups; they are not found attached to the framework. They are uniformly covered by strong spines and ray tips are either finely tapered to sharp tips or bluntly pointed. Uncinates ( Fig. 4D ) are oriented obliquely throughout the wall; they are straight with welldeveloped brackets and barbs moderately inclined to the spicule surface.

Microscleres are two size classes of discohexasters, regular oxyhexasters, rare hemioxyhexasters and even rarer oxyhexactins. Oxy–tip microscleres are far more abundant (82% of 400) than disco-tip microscleres (18%). The small discohexasters 1 ( Fig. 4E upper, F left) are somewhat stellate and have 3–11 sigmoid terminal rays originating from the sides of a small swelling at the tip of the primary ray; occasionally single terminal rays originate below the end of the primary ray. All surfaces bear small reclined spines; terminal rays end in a disc with 4–6 marginal spines. The larger discohexasters 2 ( Figs 4E lower, F right) are more stellate with 2–4 sigmoid terminal rays originating obliquely from the tip, not sides, of each primary ray. Terminal rays are finely spined but primary rays are smooth. Oxyhexasters and rare hemioxyhexasters ( Figs 4G–H ) have the form of discohexaster 2 in shape (main curvature of terminal rays, if present, is outwards in middle) and in the origin of terminal rays (obliquely from the end of the distal rays). They are entirely rough. Oxyhexactins are similar to oxyhexasters but slightly larger.

Etymology. The species name, bowiensis , refers to the location of collection, Bowie Seamount Marine Protected Area.

Remarks. This specimen with its three-layer dictyonal framework of the main body wall with a primary layer of elongate prismatic meshes and dermal and atrial cortices is consistent with diagnoses of the genera Chonelasma Schulze, 1886 and Pinulasma . In its fistular body wall, however, it is very similar to P. fistulosum and unlike Chonelasma , all species of which are without fistular body walls. The dictyonal framework of the Bowie specimen is nearly identical to that of the Aleutian P. fistulosum and if the only material available were the frameworks, they would probably be considered conspecific. But we have the spicules and there are major differences between them. Pinulasma fistulosum has hexactine dermalia and atrialia (vs pentactin dermalia and atrialia in the Bowie specimen), both discoscopule and strongyloscopule (vs tyloscopule) and discohexactin as the main microsclere (vs oxyhexaster). Based upon these differences, the new specimen from Bowie Seamount is considered the first member of a new species described here and named Pinulasma bowiensis .

In forming the genus Pinulasma, Reiswig & Stone (2013) considered two points of difference from Chonelasma to be of prime importance, its fistular body wall and pinular dermalia. By assigning the Bowie specimen as only the second species of Pinulasma , it is not surprising that the genus diagnosis needs to be altered; importance of the form of dermalia is now decreased and the fistular body wall has become a stronger defining character of the genus.

Figures

FIGURE 2. Pinulasma bowiensis n. sp., holotype body. A. Dermal side of some larger fragments of the preserved holotype showing dermal processes projecting out and fused to form ridges. B. The largest fragment, atrial side, showing large apertures on the atrial surface that pass out into the dermal processes. C. Outer (dermal) view of a medium-size fragment, upper end left. D. lateral view of the same fragment, main wall at bottom from which dermal processes project upwards in this view. E. Outer ridge of dermal process with two parietal oscula. F. Parietal osculum with a few scopules projecting from its margin. G. Dermal lattice of loose pentactins covering the dark inhalant channels. H. Close view of dermal pentactin lattice showing variation in arrangement of spicule rays. I. Close view of atrial lattice showing a consistent uniform arrangement of spicule rays.

FIGURE 3. Pinulasma bowiensis n. sp., holotype framework. A. The cleaned dictyonal framework of fragment of Fig. 1C viewed from the outer (dermal) side. B. A 5 mm thick section of the same framework viewed from the side, main wall left; note the shift in skeletal arrangement from septate main framework to dermal process framework about 1 cm out from the main wall. C. Thick cross-section of the main wall, with long-meshed primary dictyonal wall between the thick dermal cortex (right) and thin atrial cortex (left). D. Frontal view of main framework with dermal cortex intact on right side and dermal cortex dissected away on left side to reveal the long-meshed primary layer. E. Primary dictyonal layer dissected from fragment in LM. F. Framework of dermal process showing approximately even spacing between longitudinal and transverse beam lengths (lacking elongate meshes and strong septa). G. Dermal spurs. H. View of heterogeneous ornamentation of beams—some areas with dense spines and other areas without spines.

FIGURE 4. Pinulasma bowiensis n. sp., holotype spicules. A. Dermal and atrial pentactins with enlarged tangential and proximal ray ends. B. Tyloscopules, whole, enlarged ends and greatly enlarged tine club. C. Choanosomal small oxyhexactins, separate (above) and fused network (below). D. Uncinate, whole and enlarged mid-segment. E. Discohexasters 1 (above) and discohexaster 2 (below). F. Terminal ray tufts of discohexaster 1 (left) and discohexaster 2 (right). G. Oxyhexaster whole. H. Terminal rays of oxyhexaster.