Peniagone leander Pawson & Foell, 1986

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

Peniagone leander Pawson & Foell, 1986

Fig. 46

Material.

Clarion-Clipperton Zone • 1 specimen; APEI 7; 5.1042°N, 141.8861°W; 4860 m deep; 25 May. 2018; Smith & Durden leg.; GenBank: ON400681 (COI), ON406621 (16S); NHMUK 2022.61; Voucher code: CCZ_018 .

Description.

Single specimen observed swimming (Fig. 46A ). Specimen was severely damaged during collection, with only a few tentacles recovered, and hence description of morphological characters is based on in situ images. Body ovoid, slightly> 2 × as long as it is wide. Velum composed of two pairs of fully fused papillae. Tube feet four pairs; three posteriormost pairs fused together forming a posterior swimming lobe; tube feet from the anteriormost pair very short.

Remarks.

The specimen collected during the DeepCCZ expedition was recovered in bits, so no morphological features can be distinguished. Only four reddish orange tentacles were recovered, which are embedded in a transparent skin where ossicles are evident. However, P. leander is one of the few species that can be identified from images. The external morphological characters evident in in situ images from the CCZ specimen are in accordance with the species description. The species was originally described from in situ images and video footage collected across the eastern CCZ ( Pawson and Foell 1986) and subsequently observed in the area (e.g., Amon et al. 2017b).

In the phylogenetic tree, the CCZ specimen was recovered in a well-supported clade with other species of Peniagone (Fig. 34 ). It was recovered together with a sequence of P. leander , which was recently rediscovered and collected for the first time in the Mariana Trench ( Gong et al. 2020), both close to P. diaphana as reported by Gong et al. (2020). The 16S sequence of the CCZ specimen is similar (K2P distance = 2%) to the only available sequence from P. leander , but no COI sequence was made available. Our COI sequence is> 12% divergent (K2P distance) from other species within the genus. The COI gene seems to be highly divergent between species in this genus. Using the data provided in Kremenetskaia et al. (2021) and including the CCZ sequence of P. leander , COI mean interspecific divergence in the genus is 15.9% (min = 2.5% and max = 22.7%), with our sequence of P. leander being 14.5%-21.2% divergent from other species within the genus. Intraspecific divergence for species in the genus was estimated between 0.9%-3.0%.

Ecology.

The specimen was found swimming near the sediment surface on an abyssal plain in APEI 7 at 4860 m depth.

Comparison with image-based catalogue.

Peniagone leander (HOL_028) has been commonly encountered in seabed image surveys conducted across the eastern CCZ (e.g., Amon et al. 2017b) and in abyssal areas of the Kiribati EEZ, usually swimming above the seabed but sometimes creeping on it. Body colour appears to be variable; bright red, semi-transparent, purplish, and whitish HOL_028 specimens have been encountered in seabed image surveys across the CCZ.

Figures

Figure 34. Phylogenetic tree of the class Holothuroidea. Concatenated (12 S, 16 S, 18 S, 28 S, COI, and H 3) 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 46. Peniagone leander Pawson & Foell, 1986. Specimen CCZ _ 018: A, B in situ images C tentacle ossicles. Scale bars: 100 µm (C). Image attribution: Durden and Smith (A, B); Bribiesca-Contreras (C).