Hyalonema stet. CCZ_081

Bribiesca-Contreras, Guadalupe, Dahlgren, Thomas G., Amon, Diva J., Cairns, Stephen, Drennan, Regan, Durden, Jennifer M., Eleaume, Marc P., Hosie, Andrew M., Kremenetskaia, Antonina, McQuaid, Kirsty, O'Hara, Timothy D., Rabone, Muriel, Simon-Lledo, Erik, Smith, Craig R., Watling, Les, Wiklund, Helena & Glover, Adrian G., 2022, Benthic megafauna of the western Clarion-Clipperton Zone, Pacific Ocean, ZooKeys 1113, pp. 1-110 : 1

Hyalonema stet. CCZ_081

Fig. 56

Material.

Clarion-Clipperton Zone • 1 specimen; APEI 4; 7.036°N, 149.9395°W; 5031 m deep; 01 Jun. 2018; Smith & Durden leg.; GenBank: ON406610 (16S); NHMUK 2022.9; Voucher code: CCZ_081 .

Description.

Single specimen (Fig. 56 ). Lophophytous sponge; body white, somewhat bowl-shaped, longer than wide (L = 3.9 cm, W = 2.8 cm); with a wide osculum (d = 2.6 cm) surrounded by a thin margin. Attached to the sediment by a thin tuft of basalia that extends from the central lower body.

Remarks.

Morphological characters were found concordant with those of the genus Hyalonema . The 16S sequence is very similar (99.34%) to sequences from H. (Cyliconemaoida) ovuliferum Schulze, 1899, being the closest match on public databases. It is recovered in a well-supported clade along with other hyalonematids (Fig. 54 ), supporting its placement within the genus. It was not possible to assign it any subgenus, as the different subgenera have not been recovered as monophyletic ( Dohrmann 2018).

Ecology.

This specimen was collected anchored to the sediment on the abyssal plain of APEI 4 at 5031 m.

Comparison with image-based catalogue.

A very similar hyalonematid morphotype (i.e., Hyalonema sp indet., HEX_003) has been commonly encountered in seabed image surveys conducted across the eastern CCZ and in abyssal areas of the Kiribati EEZ. As observed in HEX_002, the aperture width of the central osculum in HEX_003 can vary owing to body contractions or expansions ( Kahn et al. 2020), and should hence not be used to guide identifications of these morphotypes based on seabed imagery.

Subclass Hexasterophora Schulze, 1886

Order Lyssacinosida Zittel, 1877

Family Euplectellidae Gray, 1867

Subfamily Euplectellinae Gray, 1867

Euplectellinae stet. CCZ_199

Fig. 57

Material. Clarion-Clipperton Zone • 1 specimen; APEI 1; 11.2518°N, 153.5853°W; 5202 m deep; 10 Jun. 2018; Smith & Durden leg.; GenBank: ON400729 (COI), ON406611 (16S); NHMUK; Voucher code: CCZ_199.

Description. Single specimen (Fig. 57A ). Lophophytous white sponge with tubular habitus (L = 5 cm). There is a large, central osculum (d = 2cm), and protruding fistules with terminal suboscula, each with one or two, mostly two, openings (Fig. 57B ). Long basalia (L = 6 cm) arranged as a tube, protruding from the lower end of the habitus and anchored to the sediment (Fig. 57C ).

Remarks. The 16S sequence is close to Corbitella discasterosa Tabachnick & Lévi, 2004 (2.3% K2P distance), and it is also similar to other species within the family Euplectellidae . The closest COI match is Docosaccus maculatus Kahn, Geller, Reiswig & Smith Jr., 2013 (91.5% similarity). Morphological characters are concordant with those of the family Euplectellidae , and in the phylogenetic analysis it is recovered within the Euplectellidae (Fig. 54 ), along with other species of Holascus Schulze, 1886, but poorly supported. Although the subfamilies were not recovered as monophylectic, it is very likely it belongs to the subfamily Euplectillinae based on its lophophytous form.

Ecology. This specimen was found anchored to the abyssal sediments of APEI 1 at 5202 m depth.

Comparison with image-based catalogue. A very similar Euplectellidae morphotype (i.e., Euplectellidae gen. indet., HEX_005) has been commonly encountered in seabed image surveys conducted across nodule fields areas of the eastern CCZ, but not in abyssal areas of the Kiribati EEZ. Kersken et al. (2019) collected a few specimens of HEX_005 at the APEI 3 (Northeastern CCZ), identified as Corbitella discasterosa based on morphological characters. Corbitella discasterosa is basiphytous, while our specimen is lophophytous, but this would hardly be distinguished from seabed images.

Figures

Figure 54. Phylogenetic tree of Hexactinellida. Concatenated (16 S, 18 S, 28 S, and COI) median consensus BEAST tree with posterior probability (PP) and bootstrap (BS) values indicated. Only values of PP> 0.70 and BS> 50 are shown, with values of PP> 0.95 and BS> 90 indicated with a circle. Nodes not recovered on the RAxML tree are indicated with a hyphen. Sequences generated in this study are highlighted in violet.

Figure 56. Hyalonema stet. CCZ _ 081 A in situ image, B. Scale bars: 1 cm (A); 5 mm (B). Image attribution: Durden and Smith (A); Wiklund, Durden, Drennan, and McQuaid (B).

Figure 57. Euplectellinae stet. CCZ _ 199 A in situ image B detail of body C whole specimen with protruding basalia. Scale bars: 1 cm (A); 5 mm (B). Image attribution: Durden and Smith (A); Wiklund, Durden, Drennan, and McQuaid (B, C).