Porphyrocrinus sp. CCZ_165

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

cf. Porphyrocrinus sp. CCZ_165

Fig. 29

Material.

Clarion-Clipperton Zone • 1 specimen; APEI 4; 6.9879°N, 149.9327°W; 5002 m deep; 06 Jun. 2018; Smith & Durden leg.; GenBank: ON400718 (COI), ON406616 (16S); NHMUK 2022.76; Voucher code: CCZ_165 .

Description.

Single specimen, attached to a nodule by a xenomorphic stalk (Fig. 29A ). Crown (Fig. 29C ) detached from stalk (Fig, 29B); L = 32 mm, composed of a crown and short proximal part of stalk. Proximal stalk composed of 5 very thin discoidal columnals up to 0.54 mm in diameter. Basal circlet truncated conical with distal diameter 0.54 mm and adoral diameter 0.78 mm; basals five, pentagonal in shape, with sunken lateral edges. Marked angle (~ 120°) between basals and radials. Radials five, pentagonal in shape; distal diameter 1.48 mm. Crown has five undivided arms. IBr1 are in close apposition with thin lateral flanges. Brachial formula 1+2 3+4 5+6 7+8 8+9 etc. First pinnule at IBr6; following pinnules every second ossicle; P1 has eight segments 4.04 mm in length; P2 is similar with eight pinnulars and 4.9 mm in length; P1 and P2 display lateral discoidal plates along ambulacral groove.

Remarks.

Morphological characters are concordant with those of the family Phrynocrinidae and the genus Porphyrocrinus as understood by Messing (2016). This is the first record of the genus in the Eastern Pacific. Only two specimens have been previously recorded from similar depths but collected from the Eastern Atlantic and attributed to Porphyrocrinus cf. incrassatus ( Eléaume et al. 2012). In the phylogenetic tree the specimen is recovered in a monophyletic clade with other sequences from members of the family (Fig. 28 ) and represents a new species. Based on genetic divergence of the COI gene (0.5% K2P), the specimen found in the eastern CCZ ( Crinoidea sp. NHM_055; Glover et al. 2016b) belongs to the same species. However, the specimen in Glover et al. (2016b) was not identified to family level or lower taxonomic level due to its early developmental stage, lacking key diagnostic morphological features.

Ecology.

The specimen was found attached to a nodule in the abyssal sediments of APEI 4 at 5001 m depth.

Comparison with image-based catalogue.

No similar Comatulida morphotypes have been catalogued so far from seabed imagery in the eastern CCZ or in abyssal areas of the Kiribati EEZ. Consequently, the in situ image of CCZ_065 was catalogued as a new morphotype (i.e., Porphyrocrinus sp. indet., CRI_008). Note however, that the in situ image of CCZ_065 was collected from an oblique angle and zoomed-in camera, generating a detailed view of a specimen that, owing to its small size, would be otherwise difficult to identify in quantitative assessments, e.g., where images are usually collected vertically-facing, fully zoomed out, and at a higher altitude above the seabed.

Superfamily Antedonoidea Norman, 1865

Family Antedonidae Norman, 1865

Subfamily Bathymetrinae AH Clark, 1909

Bathymetrinae inc. CCZ_176

Fig. 30

Material. Clarion-Clipperton Zone • 1 adult specimen; APEI 4; 6.9879°N, 149.9326°W; 5009 m deep; 06 Jun. 2018; Smith & Durden leg.; GenBank: ON400719 (COI), ON406617 (16S); NHMUK 2022.77; Voucher code: CCZ_176. • 1 specimen pentacrinoid stage; APEI 1; 11.2751°N, 153.7444°W; 5241 m deep; 09 Jun. 2018; Smith & Durden leg.; GenBank: ON400723 (COI), ON406618 (16S); NHMUK 2022.60; Voucher code: CCZ_186.

Description. Two specimens, one adult (CCZ_176; Fig. 30A, B ) and one pentacrinoid stage (CCZ_186; Fig. 30C, D ), both whitish when alive and attached to a glass sponge stalk. Adult with 10 arms; centrodorsal low conical. Cirri ~ 17, length 7.5 mm; c1 W> L; c2 W = L; c3 longest L = 0.95 mm, W at centre of ossicle = 0,25, W distal = 0,45; following cirrals decreasing in length to c8 or c9; c3 to c17 with everted distal edge; c8 to c14 with a spine on distal edge; c17 slightly longer than wide; claw same length as c17; opposing spine small. No basal visible. Radial 5, visible, extending beyond the rim of centrodorsal. First brachitaxis of two ossicles well separated laterally. Ibr1 rectangular slightly incised by Ibr2; Ibr2 axillery, losangic. Subsequent brachials very long; syzygies at 3+4, 9+10. First pinnule P1 on br2, 14 segments very thin and slender, composed of very long segments starting at p3 with L <6 × W. In pentacrinoid stage, five arms are visible, with orals, and stalk.

Remarks. Morphological characters are concordant with those of the subfamily Bathymetrinae in the family Antedonidae . The closest match (2.7% K2P) to the COI sequences is a sequence of Psathyrometra fragilis (AH Clark, 1907) from Rodriguez Seamount (1887 m; SIO-BIC E4433), within the family Zenometridae . However, in the phylogenetic analysis the specimens were recovered in a different clade from Psathyrometra spp. (Fig. 28 ), but in a well-supported clade with two species ( Crinoidea sp. NHM_056, Crinoidea sp. NHM_300) from the eastern CCZ ( Glover et al. 2016b). The two species previously recorded in the eastern CCZ were delimited only from genetic sequences, as they seem to be early pentacrinoid stages and thus lack morphological characters for identification. However, based on the genetic divergence values with the species Bathymetrinae inc. CCZ_176 (~ 10% K2P), the two eastern CCZ species are most likely members of the subfamily Bathymetrinae .

Ecology. The adult specimen was found attached to a glass sponge stalk (Fig. 11A ), along with an anemone, in abyssal sediments of APEI 4 at 5001 m depth. After careful examination of the material in the laboratory, a pentacrinoid stage was found attached to a sponge stalk (Figs 6A , 30B ), along with the cirriped Catherinum cf. novaezelandiae (specimen CCZ_185) and the anemone Metridioidea stet. CCZ_164, in abyssal sediments of APEI 1 at 5241 m depth.

Comparison with image-based catalogue. A very similar Comatulida morphotype (i.e., Bathymetrinae gen. indet., CRI_001) has been commonly encountered in seabed image surveys conducted across the eastern CCZ, both in nodule fields and in seamount areas ( Amon et al. 2017b). In contrast, CRI_001 was not encountered in image surveys conducted within abyssal areas of the Kiribati EEZ, where the presence of Crinoids was substantially lower than at the eastern CCZ (e.g., only nine specimens representing three morphotypes encountered in ~ 15,000 m2 of seabed surveyed; Simon-Lledó et al. 2019d).

Class Echinoidea

To date, there are 1455 records of echinoids occurring deeper than 3000 m in the CCZ, 11 of these representing preserved specimens ( OBIS 2022). Two specimens belonging to different species were collected. Sequences for the barcoding gene COI were successfully amplified for both specimens and included in a COI-only phylogenetic tree.

Subclass Euechinoidea Bronn, 1860

Infraclass Audolonta Jackson, 1912

Superoder Echinothuriacea Jensen, 1982

Order Aspidodiadematoida Kroh & Smith, 2010

Family Aspidodiadematidae Duncan, 1889

Figures

Figure 6. Catherinum cf. albatrossianum (Pilsbry, 1907). Specimen CCZ _ 073: A left B right lateral views. Scale bars: 2 mm. Image attribution: Hosie (A, B).

Figure 11. Metridioidea stet. CCZ _ 164 A in situ image of specimen CCZ _ 164 B detail of oral disc C lateral view of specimen. Scale bars: 2 cm (A); 2 mm (B); 5 mm (C). Image attribution: Durden and Smith (A), Wiklund, Durden, Drennan, and McQuaid (B, C).

Figure 28. Rooted Bayesian phylogeny of Crinoidea. Concatenated (16 S, 18 S, 28 S, COI, and CytB) 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 29. cf. Porphyrocrinus sp. CCZ _ 165 A in situ image B xenomorph stalk attached to a polymetallic nodule C detached crown before preservation. Scale bars: 1 cm (A). Image attribution: Durden and Smith (A); Wiklund, Durden, Drennan, and McQuaid (B, C).

Figure 30. Bathymetrinae inc. CCZ _ 176 A side view of adult specimen. Specimen CCZ _ 186 B pentacrinoid stage attached to a glass sponge stalk C pentacrinoid stage. Scale bars: 5 mm (A); 1 mm (B); 0.5 mm (C). Image attribution: Wiklund, Durden, Drennan, and McQuaid (A, B); Bribiesca-Contreras 2019 (C).