Rhizophyta yapensis, Shen & Dohrmann & Zhang & Lu & Wang, 2019

Shen, Chengcheng, Dohrmann, Martin, Zhang, Dongsheng, Lu, Bo & Wang, Chunsheng, 2019, A new glass sponge genus (Hexactinellida: Euplectellidae) from abyssal depth of the Yap Trench, northwestern Pacific Ocean, Zootaxa 4567 (2), pp. 367-378 : 370-377

publication ID	https://doi.org/ 10.11646/zootaxa.4567.2.9
publication LSID	lsid:zoobank.org:pub:7A20F557-E4AD-4638-9861-7BBDF3256B87
DOI	https://doi.org/10.5281/zenodo.5935761
persistent identifier	https://treatment.plazi.org/id/03AB026D-FFFB-2709-8EF0-FE5FFBCB23DB
treatment provided by	Plazi
scientific name	Rhizophyta yapensis
status	gen. et sp. nov.

Treatment

Rhizophyta yapensis View in CoL gen. et sp. nov.

( Figs. 1–4 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 , Table 2)

urn:lsid:zoobank.org:act:2211A05A-53D7-4563-82DE-86BBBB1BB33B

Material examined. Holotype: SIO-POR-083, SRSIO, Jiaolong HOV DY 38III, dive JL148, collected by Bo Lu, June 4, 2017, Yap Trench in the northwestern Pacific Ocean (8.0582°N, 137.5233°E), depth 4160 m, preserved in 95% ethanol GoogleMaps . Paratype A: SIO-POR-075, SRSIO, Jiaolong HOV DY 37I, dive JL109, collected by Bo Lu, May 15, 2016, Yap Trench (9.90045°N, 138.3995°E), 4779 m, 95% ethanol GoogleMaps . Paratype B: SIO-POR-084, SRSIO, Jiaolong HOV DY 38III, dive JL148, collected by Bo Lu, June 4, 2017, Yap Trench (8.0579°N, 137.5227°E), 4159 m, frozen at -20 GoogleMaps ?. Paratype C: SIO-POR-085, SRSIO, Jiaolong HOV DY 38III, dive JL148, collected by Bo Lu, June 4, 2017, Yap Trench (8.0582°N, 137.5224°E), 4159 m, 95% ethanol GoogleMaps .

Description. The new species is presented by four fungus-like specimens with everted, laterally directed atrial cavity. The holotype ( Fig. 1A1–A View FIGURE 1 3 View FIGURE 3 ) has a disc-like main body borne on a long, thin, slightly curved peduncle. The basal part of the peduncle is solid and features root-like outgrowths (rhizophytous method of fixation). The specimen was collected intact, but the peduncle was intentionally broken for storage and shipping. Total length of this specimen is 284 mm, of which the main body is 29 mm high, the peduncle is 233 mm long, and the root-like structure is up to 22 mm long. The main body is hanging from the upper part of the peduncle to one side; it is 60× 37 mm in diameter and up to 30 mm thick. The peduncle is solid, not hollow. It varies in diameter from 4.0 mm just below the main body to 1.0 mm at its narrowest point in the upper third and enlarges to 5.0 mm near the base. The exhalant or atrial surface of the main body ( Fig. 2A View FIGURE 2 ) is relatively smooth, with very fine lattices ( Fig. 2B View FIGURE 2 ) of loose megascleres ( Fig. 2C View FIGURE 2 ) covering the subatrial exhalant canal openings, which are up to 2 mm in diameter. The inhalant or dermal surface ( Fig. 2D View FIGURE 2 ) is more transparent, with a conspicuous network of white strands of radiating choanosomal diactins surrounding large inhalant canals, which are easily visible through the overlying thin and quite regular lattices ( Fig. 2E View FIGURE 2 ) of loose megascleres ( Fig. 2F View FIGURE 2 ). A marginal fringe is not evident at the junction of dermal and atrial surfaces. Spicules of the body are entirely unfused. The entire length of the peduncle and the main roots at the base are covered by a veil of loose pentactins with proximal rays directed inside ( Fig. 2 View FIGURE 2 G–I). The thin lateral roots branching off from the main roots are smooth ( Fig. 2G View FIGURE 2 ). The roots are solid and consist of diactins fused by short synapticulars ( Fig. 2J View FIGURE 2 ). Color of the specimen in ethanol is white.

Paratype A ( Fig. 1B1–B View FIGURE 1 2 View FIGURE 2 ) was collected broken with a tattered main body borne on a thin peduncle split into two pieces. It is 587 mm long, of which the main body is 46 mm high, the peduncle is 502 mm long, and the rootlike structure is up to 39 mm long. The peduncle varies in diameter from 2.8 mm just below the main body to 1.6 mm at its narrowest point and enlarges to 5.6 mm near the base. Color of the specimen is white in situ while yellowish brown after sampling due to mixing with sediment. A sea anemone (Relicanthus sp.) was attached to the peduncle in situ. Paratype B ( Fig. 1C1–C View FIGURE 1 3 View FIGURE 3 ) was sampled with its main body and a section of peduncle 119 mm long. The main body is 25 mm high and 44× 26 mm in diameter. The diameter of the peduncle is 1.9 mm just below the main body and 1.0 mm at its narrowest point. The specimen is colored light yellow by mixing with sediment. Paratype C ( Fig. 1D1–D View FIGURE 1 3 View FIGURE 3 ) was collected with its main body and a section of peduncle 161 mm long. The main body is 28 mm high, 54× 46 mm in diameter, and up to 21 mm thick; it was sampled intact but later cut in half. The diameter of the peduncle is 3.2 mm just below the main body and 1.5 mm at its narrowest point. Color of the specimen in ethanol is white.

Spicules. Dermalia and atrialia are pinular hexactins ( Fig. 3 View FIGURE 3 A–C) and rare pentactins ( Fig. 3 View FIGURE 3 D–F). Choanosomal megascleres are hexactins and diactins ( Fig. 3 View FIGURE 3 H–I). Peduncle and root internal spicules are diactins fused by short synapticulars ( Fig. 2J View FIGURE 2 ). Dermal spicules of the peduncle are pentactins ( Fig. 2 View FIGURE 2 H–I, Fig. 3J View FIGURE 3 ). Microscleres are toothed stellate discohexasters with flower-shaped (perianthic) tufts of secondary rays ( Fig. 3G View FIGURE 3 ). Spicule dimensions are given in Table 2.

Pinular dermal hexactins ( Fig. 3A View FIGURE 3 ) have thorny pinular rays and entirely rough tangential and proximal rays, which are various in shape and size. The pinular ray is quite variable in shape with spindle-like or ovoid ends. It is 63.8–232.3 (131.7) µm long, the tangential rays are 147.5–220.0 (181.8) µm long, and the proximal ray is 72.4– 370.0 (158.8) µm long. The ratio of proximal ray length to tangential rays length ranges from 0.3 to 2.1 with an average of 0.9. There are 38% pinular hexactins with a relatively shorter proximal ray (<60% of the tangential rays length), while 14% have it with>1.4 times the length of tangential rays. Most dermal hexactins are regular with tangential rays of equal length. However, some (1%) have only one pair of tangential rays equal and one of the unequal tangential rays is similar to a pinular ray. Atrial hexactins ( Fig. 3B View FIGURE 3 ) are similar to the dermal ones but have longer proximal rays. The pinular ray of atrial hexactins is 31.3–173.0 (128.0) µm long, the tangential rays are 133.3–230.0 (179.7) µm long, and the proximal ray is 106.0–571.0 (309.8) µm long. The ratio of proximal ray length to tangential rays length ranges from 0.6 to 2.7 with an average of 1.7. There are 12% hexactins with a relatively shorter proximal ray (~60% of tangential rays length), while 76% have it> 1.4 times the length of tangential rays. The hexactins in the transition of main body and peduncle ( Fig. 3C View FIGURE 3 ) are smaller in size, but thicker in ray width relative to ray length. They have a longer proximal ray of which 68% is more than 1.4 times longer than the tangential ray. Their pinular rays are 45.5–97.5 (70.8) µm long, the tangential rays are 82.8–173.7 (118.9) µm long, and the proximal ray is 102.9–371.7 (182.0) µm long. Dermal and atrial pentactins are rare and have spined tangential and proximal rays and smooth axial crosses ( Fig. 3 View FIGURE 3 D–F). There are two kinds of pentactins differing in size both as dermalia and atrialia, of which the smaller one is quite rare ( Fig. 3D View FIGURE 3 ). Moreover, among atrial pentactins there is another type with relatively longer proximal ray ( Fig. 3E View FIGURE 3 ). The tangential rays of dermal pentactins in the main body are 45.9–287.3 (145.4) µm long and the proximal ray is 38.7–201.3 (97.2) µm long. Atrial pentactins are bigger than dermal pentactins with the tangential rays 90.0–207.5 (159.3) µm long and the proximal ray 66.7–181.6 (120.8) µm long. Dermal pentactins in the transition of main body and peduncle ( Fig. 3F View FIGURE 3 ) have thicker and rougher rays, longer proximal rays with a length of 89.2–266.8 (159.2) µm, while relatively shorter tangential rays with a length of 60.0–139.1 (108.4) µm. A few dermal pentactins have missing or undeveloped rays and are irregular tetractins, stauractins or tauactins (not shown).

Forty-two percent of choanosomal hexactins ( Fig. 3H View FIGURE 3 ) have equal rays. Others have rays of unequal length: 44% have one ray relatively shorter than others and 14% have one pair of rays evidently longer than the other two equal pairs. The rays of choanosomal hexactins are on average 86.8–182.0 (137.1) µm long and 10.5–23.8 (19.5) µm wide. They all bear spines; ray tips are rough and abruptly pointed. Choanosomal diactins ( Fig. 3I View FIGURE 3 ) are slightly curved, with a generally inconspicuous central swelling, and can be roughly classified into two types according to the shape of terminal ends: One type has rounded, occasionally inflated, and rough terminal ends with less rough or even smooth caps, and smooth center; the other has conically pointed terminal ends and spines scattered across the whole spicule. Choanosomal diactins are 536.98–5200.0 (1766.8) µm long and 3.71–13.5 (8.7) µm wide.

Diactins of the peduncle and roots ( Fig. 2J View FIGURE 2 ) are fused by short synapticulars to form a rigid framework; they are larger than the main body diactins and smooth or somewhat verrucous. Dermal spicules of the peduncle are pentactins forming a veil ( Fig. 2 View FIGURE 2 H–I, Fig. 3J View FIGURE 3 ). They have spines in the axial cross, spined tangential and proximal rays, less rough and tapered or rounded ends of tangential rays, and short proximal rays. The tangential rays are 268.3–670.0 (456.2) µm long and the proximal ray is 30.2–99.4 (60.9) µm long.

Microscleres ( Fig. 3G View FIGURE 3 ) are toothed, stellate, perianthic discohexasters. They have short primary rays bearing 6–9 secondary rays ending in small discs with 6–8 marginal teeth. The primary rays are thick and mainly smooth while the secondary rays are thin and rough. The discohexasters are 56.7–108.6 (82.6) µm in diameter, primary rays are 6.0–11.1 (7.7) µm long, secondary rays are 19.6–43.0 (31.9) µm long.

The general spiculation of the holotype and paratypes is the same. However, some spicules differ in specific shapes. Choanosomal diactins of paratype A have rounded or conically pointed terminal ends with relatively smooth caps, and the shape of their centers varies with inconspicuous, one or two swellings ( Fig. 4A View FIGURE 4 ). The discohexasters of paratype C have 9–14 terminal rays per primary ray with 9–13 marginal teeth per disc ( Fig. 4 View FIGURE 4 B– C).

Etymology. The species name, yapensis , refers to the location of collection, the Yap Trench.

Remarks. The slight differences in spiculation between the four specimens could indicate ongoing speciation within the new genus. However, we consider these differences, combined with the geographical proximity of the specimens, to be too minor to provide evidence of full formation of separate species or subspecies (see also molecular results below). Instead, we interpret them as regular intraspecific variation.