Bathyxiphus sp. CCZ_151

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

Bathyxiphus sp. CCZ_151

Figure 61

Material.

Clarion-Clipperton Zone • 1 specimen; APEI 4; 6.9881°N, 149.9321°W; 5001 m deep; 06 Jun. 2018; Smith & Durden leg.; GenBank: ON400713 (COI), ON406638 (18S), ON406615 (16S), ON406601 (28S); NHMUK 2022.11; Voucher code: CCZ_151 .

Description.

Single specimen; basiphytous sponge (Fig. 61A, E ). Body white, elongated (L> 60 cm, W = 10 cm), thin (W = 11 mm), upright-blade shaped habitus (Fig. 61B, C, E ), attached to, possibly, a beaked-whale rostrum covered in manganese crust (Fig. 61A ).

Remarks.

Morphological characters are concordant with those of the genus, being very similar to Bathyxiphus subtilis Schulze, 1899, the only known species in the genus. However, a midrib has been suggested as a key morphological feature absent in the specimen presented here. The species was described from Isla Guadalupe at 1251 m depth, and was recently recorded in APEI 3 at 4914 m ( Kersken et al. 2019). However, 16S sequences between the APEI 3 specimen and the western CCZ specimen are 3% divergent (K2P distance). Additionally, they were not recovered as monophyletic in the phylogenetic tree (Fig. 54 ) and hence considered different species. Measurements of total length were estimated from in situ images as only approx. half the specimen was recovered.

Ecology.

The specimen was found attached to a beaked-whale rostrum covered in polymetallic crust, on abyssal sediments of APEI 4 at 5001 m depth.

Comparison with image-based catalogue.

A similar Bathyxiphus sp. morphotype (i.e., Bathyxiphus sp. indet., HEX_025), though usually much smaller-sized, 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.

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 61. Bathyxiphus sp. CCZ _ 151. Specimen CCZ _ 151 A, E in situ images B, C, D specimen before preservation. Scale bars: 2 cm (B, C). Image attribution: Durden and Smith (A, E); Wiklund, Durden, Drennan, and McQuaid (B-D).