Bathydorus poculum Reiswig, Dohrmann & Kelly, 2021

Reiswig, Henry M., Dohrmann, Martin, Kelly, Michelle, Mills, Sadie, Schupp, Peter J. & Woerheide, Gert, 2021, Rossellid glass sponges (Porifera, Hexactinellida) from New Zealand waters, with description of one new genus and six new species, ZooKeys 1060, pp. 33-84 : 33

Bathydorus poculum Reiswig, Dohrmann & Kelly sp. nov.

Figs 2 , 3

Material examined.

Holotype NIWA 126338, RV Sonne Stn SO 254/85ROV19_BIOBOX17, Southern Kermadec Ridge , 35.612°S, 178.852°E, 1150 m, 24 Feb 2017.

Distribution.

Known only from the type locality, the Southern Kermadec Ridge, north of New Zealand (Fig. 2A ).

Habitat.

Attached to hard substratum at 1149 m (Fig. 2B ).

Description.

Morphology of the holotype is a thick-walled funnel attached to rock substratum by a wide basal disc (Fig. 2B ). Both dermal and atrial surfaces have a very dense, bushy, cover of prostal diactins (Fig. 2C, E, F ). The single terminal osculum is the widest body part and the margin is abruptly sharpened; it has no marginalia (Fig. 2D ). Dimensions of the holotype are ~ 17.2 cm high and 12.8 cm wide; the measurements are only approximate as only one of the two laser points could be certainly found on the in-situ images. Wall thickness is 10.7 cm, excluding the 1-2.5 cm thick prostal cover layers on each side. Texture is soft, compressible, and resilient, neither hard nor fragile. Surfaces of both the inner and outer walls are hairy to the naked eye, and when inspected at low magnification of a dissecting microscope, both are covered with a bushy layer of prostal diactins. Colour in life is pale beige, and pale brown when preserved in ethanol.

Skeleton. Choanosomal skeleton consists of a loose network of thin choanosomal diactins amongst the thicker proximal ends of prostal diactins, and proximal rays of hypodermal pentactins. No choanosomal hexactins are present. There is no evidence of fusion between any spicules. Microscleres are scattered evenly throughout the choanosome. Ectosomal skeleton of the dermal side consists of abundant prostal diactins passing through the distal tangential parts of hypodermal pentactins and dermalia, which are mostly stauractins (62% of 126 assessed), pentactins (29%) and hexactins (10%). The atrial ectosome lacks hypoatrial pentactins but has atrialia in the form of hexactins (89% of 126 assessed), pentactins (8%), stauractins, and triactins (1.5% each). Microscleres are present as in the choanosome.

Spicules. Megascleres (Fig. 3 ; Table 1 ) are prostal diactins, hypodermal pentactins, choanosomal diactins, dermalia mostly as stauractins, and atrialia mostly as hexactins. Prostal diactins (Fig. 3A ) are long bow-shaped spicules, smooth except for patches of subterminal spines; the smooth tips are rounded or parabolic; the spicule centre is not swollen. Hypodermal pentactins (Fig. 3B ) are regular and crucial in form with very long proximal rays, averaging 3.4 × tangential ray length, and fine spines evenly scattered over the entire surface. All five rays have subterminal patches of larger spines and smooth round tips. Choanosomal diactins (Fig. 3C ) are straight, bent or more commonly sinuous in shape. Most are broken so few intact spicules are measurable for length. They are smooth except for subterminal inflated rough patches; the tip is smooth and abruptly tapered to a point. The spicule centre is moderately swollen. Dermalia (Fig. 3D ) are mainly crucial stauractins completely covered with short, rounded knobs or spines; rays are tapered to a round tip. Atrialia (Fig. 3E ) are mostly hexactins ca. half of which are pinular with one ray longer than the others. Like dermalia, these are entirely covered with short, rounded knobs or spines but longer than those of the dermalia; ray tips are rounded.

Microscleres (Fig. 3 ; Table 1 ) are all oxyhexasters and their variants with hemioxyhexasters being the most common. Oxyhexasters (Fig. 3F, G ) have short smooth primary rays and long straight secondary rays; the secondary rays are entirely ornamented with reclined spines that increase in size from the ray tip to its proximal end. Secondary rays on each primary ray vary from 2-5. Hemioxyhexasters (Fig. 3H ) are similar to oxyhexasters but at least one of the six primary rays bear only a single secondary ray. Other rare variants include oxyhexactins, oxypentasters, and oxystaurasters (Fig. 3I ).

Etymology.

Named for the beaker-shaped morphology of this species ( Bathydorus poculum , beaker; Latin).

Remarks.

This New Zealand specimen, NIWA 126338, is entirely consistent with the diagnosis of Bathydorus and is assigned there. Each of the known species of the genus differ from this specimen in the following characters: Bathydorus echinus Koltun, 1967 has prostal pentactins in addition to diactins, and dermalia as mainly pentactins; B. fimbriatus Schulze, 1886 has prostalia including pentactins as marginalia only, and no pinular atrialia; B. laevis laevis Schulze, 1886 has no prostalia lateralia and no pinular atrialia; B. laevis pseudospinosus Tabachnick & Menshenina, 2013 has some large choanosomal or prostal hexactins and smaller oxyhexasters to only 100 µm diameter; B. laninger Kahn, Geller, Reiswig & Smith Jr., 2013 has a flat body form and no prostalia on the atrial (upper) surface; B. servatus Topsent, 1927 has no prostal diactins, and dermalia as stauractins and diactins; B. spinosissimus Lendenfeld, 1915 has choanosomal hexactins, and oxyhexasters with longer primary rays (4-12 µm); in the original description of B. spinosus Schulze, 1886, there is no mention of hypodermal pentactins; although Tabachnick and Menshenina (2013) include these, they fail to certify that they are present in the holotype; this species also has wavy secondary rays on the oxyhexasters; B. uncifer Schulze, 1899 has smooth dermal and atrial surfaces, and dermalia as mainly pentactins and stauractins. These differences are sufficient to conclude that the new form is a new species, here designated as Bathydorus poculum sp. nov.

Figures

Figure 2. Bathydorus poculum sp. nov., holotype NIWA 126338, distribution, skeleton, and morphology A distribution in New Zealand waters B holotype in situ (scale bar approximate) C dermal (upper) and atrial (lower) sides of the preserved main part of the collected fragment D magnified area of the oscular margin, showing the atrial surface curving out over the dermal surface E dermal surface with dense prostal diactins F atrial surface with similarly dense prostal diactins. Image B captured by ROV Team GEOMAR, ROV Kiel 6000 onboard RV Sonne (voyage SO 254), courtesy of Project PoribacNewZ, GEOMAR, and ICBM.

Figure 3. Bathydorus poculum sp. nov., holotype NIWA 126338 spicules A prostal diactin, whole and enlarged end B hypodermal pentactin, whole and enlarged spicule centre, tangential and proximal ray ends C choanosomal diactin, whole and enlarged end D stauractine dermalium, whole and enlarged ray end E pinular hexactine atrialium, whole and enlarged ray end F oxyhexaster G enlarged whole primary and secondary ray (left) and centre of spicule showing smooth primary and ornamentation of spines on secondary rays (right) H hemioxyhexaster I hemioxystauraster.