Discorhabdella hispida, Ise & Vacelet & Izumi & Woo & Tan, 2021

Ise, Yuji, Vacelet, Jean, Izumi, Takato, Woo, Sau Pinn & Tan, Shau Hwai, 2021, First record of the genus Discorhabdella (Porifera, Demospongiae, Poecilosclerida, Crambeidae) from Sagami Bay, Japan with description of two new species, ZooKeys 1076, pp. 67-81 : 67

Discorhabdella hispida sp. nov.

Figs 2A-C , 3 , 4

Material examined.

Holotype. NSMT-Po-2489. Off Misaki , eastern part of Sagami Bay (Fig. 1 ), Japan (35°7.484'N, 139°33.212'E to 35°7.504'N, 139°33.625'E), 223- 113 m depth, dredge, 13 January 2012.

Description of holotype.

External morphology. Thinly encrusting, surface hispid due to protruding choanosomal large subtylostyles. Color greenish ochre in life, grayish white in ethanol. Size, 22 × 17 mm, about 0.3 mm thick (Fig. 2A-C ). Oscules not observed in the living specimen; probably contracted in preserved state. Ostia observed only in preserved specimen, rounded, evenly distributed, 150-300 µm in diameter.

Skeleton. Hymedesmioid skeleton made by large choanosomal subtylostyles making the sponge surface hispid and by perpendicular acanthostyles with their bases attached on substrate. Ectosomal subtylostyles arranged perpendicular to surface with tips outward. Anchorate unguiferous isochelae and sigmoid microscleres roughly dispersed throughout the sponge.

Spicules. Choanosomal subtylotyles (Fig. 3A, B ), long slightly curved near the base, maximum diameter at the base gradually tapering to sharp point (Fig. 3A ). Base smooth and slightly lumpy (Fig. 3B ). Size, 814-1500 µm in length, 42.0-56.5 (50.3) µm in shaft width, 52.4-70.8 (61.7) µm in base width.

Ectosomal subtylostyles (Fig. 3C-F ), fusiform, smooth and straight; with smooth and slightly swollen base (Fig. 3D ). Maximum diameter at middle region, then gradually tapering to a sharp point (Fig. 3E ). Microspined sparsely around the shaft and densely around the tip (Fig. 3F ). Size, 292.2-392.5 (335.4) µm in length, 13.4-16.7 (15.2) µm in shaft width, 10.7-14.0 (12.9) in tyle width.

Acanthostyles (Fig. 4A ), club-shaped head with conical spines having blunt ends. Shaft straight, fusiform, and densely covered with prominent spines with tips sharply pointed, devoid of spines on the last 10-20 µm towards extremity. Terminal holes or orifices of spines especially around head could be detected. Size, 84.0-127.5 (103.6) µm in length, 41.1-57.7 (48.0) µm in head width including spines, 26.3-42.4 (31.1) µm in head width without spines, 24-35.9 (27.8) µm in width of shaft including spine, 16.2-27.5 (21.3) µm in width of shaft without spine.

Anchorate unguiferous isochelae (Fig. 4B, C ), strongly curved C-shaped shaft with lateral expansion that forming a pair of fimbriae along its entire length. Both extremities bearing 3-7 short and unequal shaped alae. The alae closest to the lateral fimbriae sometimes reduced or nearly absent, and connected to the fimbriae. Size, 27.3-38.0 (31.7) µm in length, 2.9-4.0 (3.5) µm in shaft width.

Sigmoid microscleres (Fig. 4D ), strongly curved shaft and irregular in shape. Size, 20.7-31.2 (26.3) µm in length, 0.7-1.0 (0.8) µm in shaft width.

Distribution.

Known only from type locality, Misaki, eastern part of Sagami Bay, Japan.

Etymology.

Specific epithet refers to its hispid surface appearance.

Remarks.

The present species appears well characterized by its spicule complement, especially its microscleres. The isochelae have a unique shape, with a strongly curved shaft compared to all other species of Discorhabdella , which have a straight or feebly curved shaft. However, the isochelae of D. hispida sp. nov. are similar to the anchorate isochelae of Monanchora unguiculata (Dendy, 1922) (see also Lévi 1961, Vacelet et al. 1976). The presence of a sigmoid microsclere that is different from the true sigma, is also distinctive. Sigmas are present in four other Discorhabdella species: D. hindei ; D. littoralis ; D. ruetzleri and D. urizae ; however, in these species, there are several differences in the other spicule characters (see Table 1 ).

Discorhabdella hispida sp. nov. differs from D. hindei by having acanthostyle (length: 84.0-127.5 µm) instead of pseudoastrose acanthostyles (length: 43-57 µm) in D. hindei , a less tuberculated base of the choanosomal styles and a less developed tyle of the ectosomal subtylostyles. It differs from D. littoralis by larger choanosomal subtylostyles (814-ca 1500 µm vs 117-300 µm), by having acanthostyles instead of pseudoastrose acanthostyles, and a more tuberculated base of choanosomal subtylostyles. It differs from D. ruetzleri by larger choanosomal subtylostyles (814-1500 µm vs 470-810 µm), larger acanthostyles (84.0-127.5 µm vs 17-40 µm), larger isochelae (27.3-38.0 µm vs 20-25 µm), absence of spined microxea. It differs from D. urizae by larger choanosomal subtylostyles (814-1500 µm vs 220-750 µm in length), absence of spined microxeas and a less tuberculated base of the choanosomal styles. Acanthostyles that are more than 90 µm long have been observed only in D. tuberosocapitata and in D. misakiensis sp. nov. described in this study. But both species lack sigmoid microscleres and have choanosomal subtylostyles with a well-developed lumpy base. Tubercles around the base of choanosomal subtylostyles are not well developed in D. hispida sp. nov. and can be comparable with those recently found in D. pseudaster and D. ruetzleri . However, D. hispida sp. nov. totally lacks peculiar pseudoaster of D. pseudaster and also lacks spined microxea of D. ruetzleri .

Figures

Figure 1. Location of sampling site. Open star indicates Sagami Bay.

Figure 2. A-C External view of Discorhabdella hispida sp. nov., holotype (NSMT-Po- 2489). A Alive B in ethanol preserved C magnified view of surface of preserved specimen. Note a number of choanosomal subtylostyles vertically protruding with their tips outward D external view of Discorhabdella misakiensis sp. nov., holotype (NSMT-Po- 2490) in ethanol preserved state. Note most part of the sponge was already used for spicule preparation. Scale bars: 5 mm (A, B); 500 µm (C); 3 mm (D).

Figure 3. Spicules of Discorhabdella hispida sp. nov., holotype (NSMT-Po- 2489). A Choanosomal subtylostyle B magnified view of base of subtylostyle C-E ectosomal subtylostyle D tyle E tip F magnified view of tip. Note the surface is microspined. Scale bars: 300 µm (A); 50 µm (B); 10 µm (D, E); 5 µm (F).

Figure 4. Spicules of Discorhabdella hispida sp. nov., holotype (NSMT-Po- 2489). A Acanthostyles B isochelae C magnified view of one extremity of isochelae. a, alae D sigmoid microscleres. Scale bars: 20 µm (A); 10 µm (B, D); 2 µm (C).