Moebjergarctus clarionclippertonensis, Bai, X. Wang, Zhou, Lin, Meng & Fontoura, 2020

Trokhymchuk, Roman, Schmidt-Rhaesa, Andreas, Utevsky, Serge, Kristensen, Reinhardt Møbjerg & Kieneke, Alexander, 2024, Towards a better understanding of deep-sea tardigrade biogeography: numerous new records from the Southern Ocean, Zootaxa 5543 (1), pp. 1-39 : 17

Moebjergarctus clarionclippertonensis Bai, Wang, Zhou, Lin, Meng & Fontoura, 2020

N= 4 specimens: 2 females, 2 with undetermined sex occurrence: ANDEEP 1, ANDEEP-SYSTCO; 3,551–3,650 m bsl.

Fig. 7 ; Supplementary Table 1.4

Short description

Large and robust tardigrade 148–283 µm long and 52.3–99.7 µm width (n=2). Buccal apparatus with stylets ( Fig. 7B ). Cephalic cirri with annulated base, smooth portion of the scapus and short flagellum ( Fig. 7E, F ). Each leg with a sensory organ ( Fig. 7E ). Internal and external digits are of the same size and wrinkled ( Fig. 7C, G ). Caudal region is covered with a thick cuticular layer shown as a bulge ( Fig. 7A, E ). All the females have a patched seminal receptacle opening ( Fig. 7D, H ).

Remarks

The identification of this species is certain because of the morphology of cephalic cirri (annulated base, smooth scapus and short flagellum). The internal and external digits of all limbs are the same size that distinguishes this species from M. okhotensis ( Bai et al. 2020, Saulenko et al. 2022). This species was previously reported from Pacific deep-sea plains with a high abundance of manganese or polymetallic nodules ( Bai et al. 2020). At least the sampling stations of expedition ANDEEP 1 that contained M. clarionclippertonensis (Shackleton Fracture Zone, 59°52.30′S, 59°57.63′W) at the deep sea bottom of the Drake Passage are also close to areas with polymetallic sulfide deposits and hydrothermal vent activity (see discussion for details).

Figures

FIGURE 7. Moebjergarctus clarionclippertonensis. A Moebjergarctus clarionclippertonensis, female, light microscopy (DIC), dorsal view, note caudal bulge (arrowhead). B Moebjergarctus clarionclippertonensis, female, light microscopy (DIC), dorsal view, note buccal apparatus’ stylet (arrowhead). C Moebjergarctus clarionclippertonensis, female, light microscopy (DIC), ventral view, note leg II digits (arrowhead). D Moebjergarctus clarionclippertonensis, female, light microscopy (DIC), caudal region, note patched seminal receptacle opening (arrowhead). E Moebjergarctus clarionclippertonensis, female, SEM, sagittal view. F Moebjergarctus clarionclippertonensis, female, SEM, head, dorsal view, note smooth portion of internal cirrus (arrowhead). G Moebjergarctus clarionclippertonensis, female, SEM, leg III digits. H Moebjergarctus clarionclippertonensis, female, SEM, posterior ventro-sagittal view, note seminal receptacle opening patch borders (arrowheads). Abbreviations: an—anus, bu—caudal bulge, cE—cirrus E, ec—external cirrus, go—gonopore, ic—internal cirrus, mc—median cirrus, pb— pharyngeal bulb, pc—primary clava, sc—secondary clava, se—leg sensory organ, sro—seminal receptacle opening.