Calyptorete falkorae Tabachnick & Fromont, 2019

Tabachnick, Konstantin, Fromont, Jane, Ehrlich, Hermann & Menshenina, Larisa, 2019, Hexactinellida from the Perth Canyon, Eastern Indian Ocean, with descriptions of five new species, Zootaxa 4664 (1), pp. 47-82 : 53-57

Calyptorete falkorae Tabachnick & Fromont sp. nov.

urn:lsid:zoobank.org:act:DA055F7A-0DA6-43BE-801D-BEC93A91B739

Material examined. Holotype ( WAM Z92540). Australia: Western Australia: 1 specimen, Perth Canyon, Site A, (31 o 54’45.252’’S, 115 o 4’51.270’’E, Figure 1 ), 695 m, A. Hosie, ROV, 10/03/2015, RV Falkor station FPC15_D08_S004.

Description. Body, Figure 4 . The body is cup-shaped and comprises branching and radiating tubes supported on a basal stalk. The tubes are arranged radially around a central atrial or pseudoatrial cavity. They have lateral oscula opening on the external surfaces of the cup. These oscula are covered by sieve plates. The internal wall of the cup has longitudinal skeletal struts with fine mesh between, identical in size to the external mesh overlying the sieve plates. Overall height is 110 mm, width of the cup 85 mm, height of stalk 40 mm, width of stalk 25 mm. Wall thickness apically at widest point is 10 mm. The texture is rigid and the colour is creamy white.

Framework, Figure 4 , 5 . The tubes which form the wall of the cup have a typical euretoid skeleton constructed from two layers of framework with rectangular 0.7–0.8 x 0.4–0.5 mm meshes, and some irregular (triangular) constructions common in the euretoid skeleton. The beams are slightly roughened. Dictyonal strands are 0.03–0.06 mm in diameter, the beams between dictyonal layers have the same diameter. The free rays which protrude distally and proximally are 0.3–0.04/ 0.017 –0.023 mm, they have conically pointed or rough and clavate outer ends.

The lateral oscula are rounded, oval or slit-like (some may not have completely divided during the dichotomous branching). They are covered by sieve plates constructed of a layer of dermal hexactins or similar spicules which are connected to adjacent spicules by secondary silica deposition between the tangential rays, and form mostly square meshes 0.08–1.2 mm with beams 0.05–0.08 mm in diameter. The short free ray (distal) is 0.06–0.15/ 0.03 mm, the proximal ray is 0.5–0.6/ 0.07 mm.

Spicules. Megascleres, Figure 6 . Uncinates of a single type are about 3.6/ 0.015 mm ( Figure 6 J ). Discoscopules with short spines over the surface are 0.395 –0.730 mm long (n=21, avg: 0.643 mm, std: 0.080 mm), they have 2–5 tines 0.091 –0.122 mm long (n=21, avg: 0.106 mm, std: 0.008 mm) ( Figure 6 D–E). Some young scopules have a smooth surface, and are 0.426 –0.532 mm long (n=2, avg: 0.472 mm, std: 0.075 mm), they have 3–4 tines 0.084 – 0.091 mm long (n=2, avg: 0.087 mm, std: 0.005 mm) ( Figure 6 F ). Dermal hexactines have distal ray reduced to short rudiment ( Figure 6 A–C). These spicules have a rough surface and rays with conically pointed outer ends. The distal ray of the dermal hexactin is 0.038 –0.114 mm long (n=13, avg: 0.071 mm, std: 0.023 mm), tangential rays are 0.517 –0.927 mm long (n=24, avg: 0.734 mm, std: 0.117 mm), the proximal ray is 0.258 –1.140 mm long (n=10, avg: 0.578 mm, std: 0.274 mm), usually they are shorter than the tangential rays, the diameter of these rays is 0.01–0.05 mm.

Microscleres, Figure 6 . Only a few discohexasters and hemidiscohexasters with 1–3 rough or short, spiny, curved secondary rays, were found in the remnants of the dermal membrane( Figure 6 K ). They are 0.058 –0.096 mm in diameter (n=8, avg: 0.078 mm, std: 0.013 mm), their primary rosette is 0.005 –0.013 mm in diameter (n=8, avg: 0.010 mm, std: 0.003 mm).

Remarks. This genus was previously only known from Sagami Bay, off Japan, the locality of the type specimen of Calyptorete ijimai Okada, 1925 . Until now it was a monospecific genus.

There has been some confusion about the morphology of the genus, and with fresh material this has been reviewed and a revised generic diagnosis provided. The sponge is cup-shaped, “composed from branching and radiating tubes supported on a tubular stalk” and “opened to exterior and to interior” ( Reiswig & Wheeler, 2002). One issue was the atrial cavity of the sponge. The true atrial cavity should be considered to be the branching cavity inside the “branching and radiating tubes”, while the central cavity inside the cup could have a secondary origin and be regarded as pseudoatrial. In addition, the spicules were described as atrial (gastral) in the original description by Okada (1925) (that is, those situated on the inner atrial surface of the tubes), or dermal from the “pseudoatrial” surface. One problem was the interpretation of the single layer of sieve-like structures found both on the inner (mostly dermal) and pseudoatrial surfaces. If the body shape interpretation of branching tubular construction ( Okada,1925; Reiswig & Wheeler, 2002) is followed these structures (which cover the numerous lateral oscula) should be termed sieve plates. If this interpretation is not followed then the branching cavity, which would be considered atrial, should be regarded as a canal. However, this would change the systematic position of the genus to the family Tretodictyidae as such canals should be considered as schizorhyses. This is not followed here. In summary, we provide an amended generic diagnosis due to the new specimen allowing both a revision of the interpretation of the body shape, and to update details on the spicule complement of the genus.

The new species is identical in external morphology to Calyptorete ijimai but differs in the size of the scopules (the largest scopules in the latter are 0.37 mm in length while in C. falkorae sp.nov. they are much larger (0.395 – 0.730 mm long) and the lack of small uncinates in the new species, with those present being a single size category of 3.6/ 0.015 mm, while in C. ijimai there are four classes. The new species also lacks tyloscopules and discohexactins.

Etymology. The species is named for the RV Falkor owned and operated by the Schmidt Ocean Institute in appreciation of providing the ship time and equipment that enabled this specimen to be collected.

Distribution. Currently found only in the Perth Canyon at 695 meters depth.

Figures

FIGURE 1. Map of Perth Canyon. Triangles are RV Falkor stations and circles are RV Southern Surveyor stations.

FIGURE 4. Calyptorete falkorae sp. nov., holotype, WAM Z92540, external morphology (scale 50 mm).

FIGURE 5. Calyptorete falkorae sp. nov., holotype, WAM Z92540, SEM images. A, B, euretoid framework of the wall. C, sieve plate constructed from a layer of dermal hexactins.

FIGURE 6. Spicules of Calyptorete falkorae sp. nov., holotype, WAM Z92540. A–C, dermal hexactins. D–E, strongyloscopules. F, oxyscopule. J, uncinate. K, microdiscohexaster.