Tethya irisae, Sorokin, Ekins, Yang, Cárdenas & Cárdenas, 2019

Sorokin, Shirley J., Ekins, Merrick G., Yang, Qi & Cárdenas, Paco, 2019, A new deep-water Tethya (Porifera, Tethyida, Tethyidae) from the Great Australian Bight and an updated Tethyida phylogeny, European Journal of Taxonomy 529, pp. 1-26 : 6-10

Tethya irisae sp. nov.

urn:lsid:zoobank.org:act:26151082-02AC-41F5-9E22-15EF212DBDC3

figs 1–3, 4A

Etymology

Named after the golden-winged Greek goddess Iris, grandchild of Tethys, who could reach all parts of the cosmos including the deep sea; and in memory of marine naturalist Iris Sorokin.

Material examined

Holotype

AUSTRALIA • Size 16.6 mm total height (body 11.9 mm (h) × 11.7 mm (w), stalk 4.7 mm (l) × 1.77 mm diam., raised apical osculum); Great Australian Bight ( GAB ) ; 34.822° S, 132.69° E; 1006 m depth; Great Australian Bight Research Project ( GABRP) leg.; epibenthic sled; SAMA S3387 .

Paratypes

AUSTRALIA • 4 specs; same collection data as for holotype; SAMA S2913 , SAMA S3388 , QM G305000 , QM G305001 • 1 spec.; Great Australian Bight ; 33.928° S, 131.06° E; 1027 m depth; GABRP leg.; epibenthic sled; UPSZTY 178608 .

Additional material at South Australian Museum (sighted only)

AUSTRALIA • 1 spec.; Great Australian Bight; 33.928° S, 131.06° E; 1027 m depth; GABRP leg.; epibenthic sled; SAMA S2039 • 1 spec.; Great Australian Bight; 35.152° S, 134.109° E; 1021 m depth; GABRP leg.; epibenthic sled; SAMA S2371 • 1 spec.; Great Australian Bight; 33.718° S, 130.66° E; 1005 m depth; GABRP leg.; epibenthic sled; SAMA S2482 • 1 spec.; Great Australian Bight; 34.629° S, 132.35° E; 1021 m depth; Great Australian Bight Deepwater Marine Program (GABDMP) leg.; epibenthic sled; SAMA S2095 • 1 spec.; Great Australian Bight; 34.705° S, 132.53° E; 987 m depth; GABDMP leg.; epibenthic sled; SAMA S2096 • 1 spec.; Great Australian Bight; 33.802° S, 130.70° E; 1000 m depth; D. Currie leg.; epibenthic sled; SAMA S1461 .

Comparative material

INDIA • 1 section in slide, holotype of Burtonitethya gemmiformis Sarà, 1994 ; Andaman Islands; depth unknown; BMNH 1957.7.15.1.

AUSTRALIA – New South Wales • 1 spec., syntype and slides of Tethya fissurata Lendenfeld, 1888 ; Port Jackson; “ 33°51′ S, 151°16′ E [33.85° S, 151.27° E]; depth unknown; AM G.9069 (syntype), Z6053, Z6893 (slides).

NEW ZEALAND • 1 spec., holotype (specimen and slides) of Tethya bullae Bergquist & Kelly-Borges, 1991 ; Alderman Island; “ 36°58´S, 176°05´E [36.97° S, 176.08° E]; 100 m depth; AM Z5074.

DNA barcoding

COI ( MH518072 ), 28S (D3–D5) ( MH511148 ), ITS1-5.8S-ITS2 ( MH511149 ). All sequences came from the same individual from lot SAMA S2913, although this is a different individual than the type specimens. A tissue sample from this voucher is deposited at the Australian Biological Tissue Collection at the South Australian Museum, Adelaide (ABTC145318).

Description

A small, spherical to oval, stalked, sponge ( Fig. 2 ). The sponge body is 11–14 mm diam., with the stalk approximately the same length as the diameter of the sponge. The surface is covered in polygonal platelike tubercules (2–3 mm diam.) separated by grooves (0.5 mm wide, 0.25–0.5 mm deep). The sponge is firm to hard and spiculose. Grey/white in life and in ethanol. There is a single raised apical osculum. No sign of any budding.

SKELETON. A stalk of dense megascleres supports the sponge. There is a ‘nucleus’ where the stalk meets the centre of the sponge body, and although the stalk may divide and/or flatten and thicken externally it emanates from the same point at the base of the sponge. From the nucleus dense bundles (0.3–0.7 mm in diameter) of megascleres radiate through the choanosome to the surface tubercles; the bundles slightly fan out in the tubercles. The cortex is a dense layer of micrasters and oxyspherasters interspersed with megascleres emerging through the tubercules, making the surface microscopically hispid ( Fig. 2 D– E). The cortex is well developed and follows the contours of the tubercules, 1–1.7 mm thick. Large cortical canals are visible between tubercles ( Fig. 2E ). A thin fibrous layer is below the cortex, it has micrasters in a much lower density. Large oxyspherasters are especially found at the base of the cortex. The megascleres of the stalk are covered in a layer of micrasters and regularly interspersed with shortrayed oxyspherasters. The choanosome is rich in sediment-like particles; there are some micrasters and rare oxyspherasters. Foraminifera ( Globigerina d'Orbigny, 1826 ) and Radiolaria are common in the cortical canals and the choanosome.

SPICULES. Megascleres are straight style/strongyloxeas (size range 900–3060 × 17–52 µm) ( Table 1 , Fig. 3 A–B) the proximal end is smooth and rounded, the distal end is tapered (not stepped) and either rounded or pointed. There are auxiliary thinner styles to subtylostyles in the medulla between the main styles (260–900 × 7–22 µm) ( Fig. 3C ). Megaster microscleres are two types of oxyspherasters: longrayed oxyspherasters (120–185 µm) ( Fig. 3D ) have ~15 rays that can be bent towards the oxeote tips (ray profile is conical); short-rayed oxyspherasters (53–154 µm) ( Fig. 3E ) have a larger centrum ~17 rays with a conical profile and oxeote tips. Micraster microscleres are acanthooxyspherasters (12–20 µm) ( Fig. 3F ), with a centrum and spined tips, and lightly spined on the rays.

Ecology and distribution

Found on the continental slope in the Great Australian Bight at a depth of 1000 m, in soft sediment (clay/ silt).

Remarks

The morphology as well as molecular markers confirm that our new sponge is a Tethya . Table 2 shows morphological comparisons between other species of Tethya from Australia and New Zealand. The external appearance of Tethya irisae sp. nov. is similar to T. fissurata from Port Jackson, New South Wales, Australia, which is spherical with polygonal tubercules and has a stalk. However, T. fissurata differs from T. irisae sp. nov. in body size (~ 4 cm diam.), tubercule shape, and number of oscula (2–4). Tethya fissurata has megascleres with stepped ends unlike T. irisae sp. nov., which are smooth and T. fissurata lacks the short-rayed oxyspherasters seen in T. irisae sp. nov. Although we do not know the exact depth at which T. fissurata was collected, Port Jackson (viz. Sydney Harbour) is not deeper than 45 m ( Johnston et al. 2015), so this is presumably a shallow species. Tethya bullae is a deep-water (100 m) sponge that is of comparable size to T. irisae sp. nov., although it has prominent raised tubercules rather than the flat plate-like tubercules of T. irisae sp. nov. ( Fig. 4 ). The holotype from the Australian Museum does not include a stalk but the description and photograph in Bergquist & Kelly-Borges (1991) shows “basal flattened branched rooting processes”. The long-rayed oxyspherasters of T. irisae sp. nov. are similar to those of T. bullae . The short-rayed oxyspherasters in T. irisae sp. nov. do not fork as those of T. bullae . Tethya irisae sp. nov. has lightly spined acanthooxyspherasters compared to the completely spined acanthooxyspherasters of T. bullae . In addition to T. fissurata and T. bullae , other Tethya with rooting processes/stolons are shown in Table 2 (descriptions in bold text). It is difficult to tell how similar the rooting processes are to each other but these species differ in spicule forms and dimensions from T. irisae sp. nov. For example: species with megascleres <2000 µm ( T. acuta Sarà & Sarà, 2004 , T. bergquistae Hooper in Hooper & Wiedenmayer, 1994 , T. burtoni Sarà & Sarà, 2004 , T. dendyi Sarà & Sarà, 2004 , T. robusta (Bowerbank, 1873) , T. seychellensis (Wright, 1881) , T. stolonifera Bergquist & Kelly-Borges, 1991 ); species with megasters not of a ‘spheraster’ form ( T. amplexa Bergquist & Kelly-Borges, 1991 , and T. fastigata Bergquist & Kelly-Borges, 1991 ); species with very different micrasters ( T. ingalli Bowerbank, 1858 , T. flexuosa Sarà & Sarà, 2004 and T. monstrosa ( Burton, 1924)) . In addition, T. irisae sp. nov. is collected at the start of the bathyal zone (~ 1000 m). The deepest of the Tethya is T. compactus Bergquist, 1961 (402 m), which has very different external morphology.

It occurred to us that when using the key to genera of Tethyidae ( Sarà 2002) , Tethya irisae sp. nov. appears closest to the monospecific genus Burtonitethya , a tethyid with a stalk of equal length to the diameter of the sponge. The type of Burtonitethya ( B. gemmiformis ), was collected from the Andaman Sea at an unknown depth (Sarà 1994). Burtonitethya gemmiformis was originally assigned to Tethya (labelled as Tethya gemmiformis Burton & Rao, 1957 on the NHM microscope slide) but was re-assigned to a new genus Burtonitethya by Sarà (1994) on account of the stalk, the conspicuous nucleus with strongyles, the reduced lacunar cortex, the specialised surface tubercules and the giant oxyaster megasters. Our new species clearly differs from this species in having different microscleres and does not have the giant megasters present in B. gemmiformis . As there is no specimen of the type species of Burtonitethya and thus no potential to sequence the sponge, we cannot test if Burtonitethya is a junior synonym of Tethya .

As seen above, the genus Tethya shows many different modes of attachment including basal stolons, basal roots, curved peduncles, flattened rooting processes as well as attachment discs and narrow skirts of tissue. Our results suggest that the stalk may not be a good genus-defining character within the family. Heim et al. (2007) in their analysis of Tethya species, for which they used morphological characters and molecular markers, suggest that characters pertaining to ecological influences may have developed several times. Similarly, we suggest that some of the external morphological characters used to separate genera of Tethyidae are homoplasious, probably appearing several times in different clades of Tethya and we question whether they should be grouped as definitive characters in morphological identifications. In the same way the genus Amphitethya Lendenfeld, 1907 (Family Tetillidae Sollas, 1886 ) was created based on its stalk, but phylogenies show it is a Cinachyrella Wilson, 1925 ( Szitenberg et al. 2013; Schuster et al. 2017).

Figures

Fig. 2. A. Freshly collected specimens (lot SAMA S2096) of Tethya irisae sp. nov. B. Paratype (QM G305000) showing single apical oscule (arrow), and tessellated plate-like polygonal tubercules. C–D. Holotype (SAMA S3387), entire specimen and SEM showing surface tubercules with emerging megascleres. E. Section of UPSZTY 178608, showing the well-developed cortex and cortical canals around the tubercules.

Fig. 3. Tethya irisae sp. nov. spicules. A–B. Straight style/strongyloxeas. C. Subtylostyle. D. Long-rayed oxyspheraster. E. Short-rayed oxyspheraster with small acanthooxyspheraster. F. Acanthooxyspheraster.

Fig. 4. Comparative sizes and external morphology of species of Tethya Lamarck, 1815. A. Tethya irisae sp. nov., holotype (SAMA S3387). B. Tethya bullae Bergquist & Kelly-Borges, 1991, part of the holotype (AM Z5074). C. Tethya fissurata Lendenfeld, 1888, syntype (AM G.9069) Note: the original photo of T. bullae (Bergquist & Kelly-Borges 1991) shows rooting processes.