Holascus stet. CCZ_078

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

Holascus stet. CCZ_078

Fig. 59

Material.

Clarion-Clipperton Zone • 1 specimen; APEI 7; 5.0443°N, 141.8162°W; 48745 m deep; 28 May. 2018; Smith & Durden leg.; GenBank: ON400700 (COI), ON406636 (18S), ON406613 (16S), ON406599 (28S), ON411256 (ALG11); NHMUK 2022.7; CCZ_078 .

Description.

Single specimen; lophophytous white sponge (Fig. 59A ). Band-like body, collar formed from thin wall with two large openings, with lower opening being larger than upper opening (Fig. 59B, C ). Body height of 4.8 cm, lower body diameter of 15.1 cm, and upper body diameter of 11.8 cm. basalia almost as long as the body height, protruding from the lower margin and anchoring it to the sediment (Fig. 59A ).

Remarks.

Morphological external characters are concordant with the description of Holascus spinosus Kersken, Janussen & Martínez Arbizu, 2019, which was described from the IOM area in the CCZ. The closest genetic matches on GenBank for the 16S correspond to species within the genus Holascus (2.1-3.5% genetic divergence), with the holotype of Holascus spinosus being the closest match (2.1% genetic divergence). There are no 18S sequences available for H. spinosus , but it is 0.23% divergent from another species within the genus, H. euonyx (Lendenfeld, 1915), from which it differs morphologically. In the phylogenetic tree it was recovered, with low support, as sister to H. spinosus (Fig. 54 ), but 16S genetic divergence suggested these to be separate species.

Ecology.

This specimen was found anchored to abyssal sediments of APEI 7 at 4874 m depth.

Comparison with image-based catalogue.

A very similar Holascus sp. morphotype (i.e., Holascus sp. indet., HEX_014) has been commonly encountered in seabed image surveys conducted across nodule fields areas of the eastern CCZ and in abyssal areas of the Kiribati EEZ.

Subfamily Bolosominae Tabachnick, 2002

Bolosominae stet. CCZ_198

Fig. 60

Material. Clarion-Clipperton Zone • 1 specimen; APEI 1; 11.2518°N, 153.6053°W; 5205 m deep; 10 Jun. 2018; Smith & Durden leg.; GenBank: ON400728 (COI), ON406637 (18S), ON406614 (16S), ON406600 (28S); NHMUK 2022.10; Voucher code: CCZ_198.

Description. Single specimen; lophophytous white sponge (Fig. 60A, B ). Body is cup- to bell-shaped, slightly wider than long (L = 10 cm, W = 11 cm), with a long, slender stalk (L = 70 cm) anchored to soft sediment. Central osculum with thick body walls.

Remarks. The closest match with the 18S sequence is the holotype of Hyalostylus microfloricomus Kersken, Janussen & Martínez Arbizu, 2019 (99.8%), described from the Heip Mountains in the GSR contract area in the CCZ at 3788 m depth ( Kersken et al. 2019). However, in the phylogenetic tree (Fig. 54 ) it was recovered in a well-supported clade representing the subfamily Bolosominae , but subclades were not well supported and hence the specimen is not attributed to any genera.

Ecology. This specimen was collected on abyssal sediments of APEI 1 at 5205 m depth, and was anchored to the sediment.

Comparison with image-based catalogue. A very similar stalked sponge morphotype (i.e., Hexactinellidae ord. indet., HEX_026) has been encountered in seabed image surveys conducted at the eastern CCZ, but not in abyssal areas of Kiribati’s EEZ. In seabed images, HEX_026 highly resembles Hyalonema (Cyliconemaoida) campanula Lendenfeld, 1915, as identified by Kersken et al. (2019) based on morphological traits observed in specimens encountered in the eastern CCZ.

Order Sceptrulophora Mehl, 1992

Family Euretidae Zittel, 1877

Subfamily Chonelasmatinae Schrammen, 1912

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 59. Holascus stet. CCZ _ 078 A in situ image B lateral view of specimen before preservation C top view. Scale bars: 2 cm (A); 1 cm (B). Image attribution: Durden and Smith (A); Wiklund, Durden, Drennan, and McQuaid (B, C).

Figure 60. Bolosominae stet. CCZ _ 198 A, C in situ images B specimen before preservation. Scale bars: 5 cm (A, C). Image attribution: Durden and Smith (A, C); Wiklund, Durden, Drennan, and McQuaid (B).