Batillipes wyedeleinorum Bartels, Fontoura, Nelson & Kaczmarek, 2024

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 : 10-11

Batillipes wyedeleinorum Bartels, Fontoura, Nelson & Kaczmarek, 2024

N= 2 specimens: 1 female, 1 juvenile occurrence: ANDEEP I; 60°38.12′S, 53°57.67′W; 2,893 m bsl (female); ANDEEP 2; 65°20.09′S, 54°14.72′W; 1,088 m bsl (juvenile).

Both specimens are morphologically similar to the recently described species Batillipes wyedeleinorum Bartels et al., 2024 . However, we present our detailed description of an adult female since it adds important information to the original description of B. wyedeleinorum regarding character variation and ecological preferences (e.g. deep sea occurrence).

Description of female

Figs 4–5 , Supplementary Table 1.1

Body. Small Batillipes with total body length (from cephalic rim to the tip of caudal appendage) of 147 µm, and maximum body width of 46 µm between leg III and leg IV ( Figs 4 , 5 A-C). Distinct trapezoid head, separated from the body by a distinct neck constriction and with conical lateral projections I of 7 µm length ( Fig. 5C, G ). Lateral projections between leg I and leg II (2.5 µm) are blunt. Lateral projections between leg II and III (3 µm) are conical. The lateral projections between leg III and leg IV (4 µm) are elongated (up to 20 µm) and rather blunt ( Fig. 5C, G ). Body cuticle punctuated with internal pillars ( Fig. 5G–J ).

Cephalic region. Cephalic cirri with cirrophores. Cephalic cirri tips have tufts with additional filaments ( Fig. 5G, H ). Cirri A are 24 µm in length. Unpaired median cirrus is 16 µm long. Internal cirri are 14 µm long and attached dorsally. External cirri are 11 µm long and situated close to the primary clavae. Primary clavae of 9.0 µm length are tube-shaped. ( Fig. 5A ). Primary clavae, cirrus A and external cirri all originate from a common lateral bulge of the head ( Fig. 4 ). Secondary clavae are indistinct. Eyes not visible. Mouth cone is clearly visible ( Fig. 5G, H ). Ovoid pharyngeal bulb (15 × 10 µm) connected with the buccal tube with three placoids.

Legs. Sensory organs present on all telescopic legs ( Fig. 5B ). Sensory organs of legs I and II are about 7 µm long, of legs III to 10 µm. Sensory organs of legs IV with a cirrophore are 18 µm long and have frayed tips ( Figs 5D, D 2 ). Bases of legs I and legs II have a small (1.5–2.0 µm) dome-shaped projection. On legs I, digits 2 (4.0 µm) and 4 (5.5 µm) are the shortest (considering digit 1 the most cephalically), digits 3 (10.5 µm) and 5 (11.0 µm) are the longest and digits 1 (6.0 µm) and 6 (7.0 µm) are medium sized. The same pattern of digits on legs II and III ( Fig. 5A ). On legs IV, digits 3 (6.0 µm) and 4 (8.0 µm) are the shortest, and digits 1 (11.0 µm), 2 (14.5 µm), 5 (14.0 µm), 6 (11.0 µm) are the longest ( Fig. 5D ). Digits have disc-shaped suction discs ( Figs 4 , 5A, D, J ). The specimen has some folded discs on legs II–IV ( Fig. 4 , 5I, J ).

Caudal region. The caudal appendage is 8.5 µm long and looks like a single spine attached directly on the body. Rosette-shaped, six-lobed female gonopore and anus present ( Fig. 5E, J ). Putative smooth area between gonopore and anus is visible on light microscopy figures ( Fig. 5E ) but hidden by leg IV on SEM figures ( Fig. 5J ).

Remarks

There are only a few and slight morphological differences between B. wyedeleinorum and our specimen. We did not see the same medial groove in a smooth area between gonopore and anus. In addition, we were not able to observe the papillae on legs because of legs positioning after preparation for SEM (see Additional remarks in Bartels et al. 2024).

A possible ecological difference is evidenced by our new geographic and bathymetric record of this species.

Short description of juvenile

Fig. 5F ; Supplementary Table 1.1

Four-toed juvenile 123.5 µm long with punctuated cuticle. Cephalic cirri with lance-shaped tips. Each leg with a sensory organ. Lateral projections on the neck region, between leg II and leg III are conical; projections between leg I and leg II, as well as between leg III and leg IV are blunt. On each leg digit 2 is shorter than the other. Short single conical caudal appendage presented.

Remarks

We identified this specimen as Batillipes wyedeleinorum because of overall morphological similarity. This individual has comparably shorter cirri E, a sensory organ on the leg IV and more elongated suction disks on digits. This kind of minor dissimilarities between mature and juvenile stages are known for other species of Batillipes ( Kristensen & Mackness 2000) . Furthermore, both specimens occur in a similar habitat, the Antarctic deep sea bottom, which is a rather unusual and unique habitat for species of the genus Batillipes (but see discussion).

Figures

FIGURE 2. Absolute abundances of Tardigrada from all 130 analysed core samples of expeditions ANDEEP-1 to 3 and ANDEEP-SYSTCO to the Southern Ocean plotted against depth. Samples were taken at different working areas in the Cape Basin, in the Lazarev Sea, in the Weddell Sea, in the Ona Basin, and at different working stations in the Drake Passage

FIGURE 4. Batillipes wyedeleinorum, female, drawing (reconstruction) based on light microscopy (DIC) and SEM, ventral view. Abbreviations: an—anus, bt—buccal tube, cA—cirrus A, ca—caudal appendage, cE—cirrus E, d—digit, ec—external cirrus, fd—folded disc, go—gonopore, ic—internal cirrus, mc—median cirrus, mo—mouth opening, lp—leg projection, pb— pharyngeal bulb, pc—primary clava, pr—body projection, se—leg sensory organ.

FIGURE 5. Batillipes wyedeleinorum. A female, light microscopy (DIC), ventro-sagittal view, note leg III digit arrangement (arrowhead). B female, light microscopy (DIC), ventro-sagittal view. C female, light microscopy (DIC), ventro-sagittal view, note body projections (arrowheads). D female, light microscopy (DIC), caudal region, note leg IV digits arrangement. D2 female, light microscopy (DIC), leg IV sensory organ, note tuft of additional filaments (arrowhead). E female, light microscopy (DIC), caudal region, note smooth area (arrowhead). F Batillipes wyedeleinorum, juvenile, light microscopy (DIC), sagittal view, note body projections (arrowheads). G female, SEM, ventro-sagittal view, note cirrus A tip (arrowhead). H female, SEM, ventral view, cephalic region, note cephalic cirri tips (arrowheads). I female, SEM, ventral view, leg II region, note folded digits (arrowhead). J female, SEM, caudal region, ventral view, note cuticular pillars (arrowhead). Abbreviations: an—anus, ca—caudal appendage, cE—cirrus E, ec—external cirrus, go—gonopore, ic—internal cirrus, mo—mouth opening, lp—leg projection, pb—pharyngeal bulb, pc—primary clava, pr—body projection, se—leg sensory organ.