Bryodelphax aaseae, Kristensen, Reinhardt M., Michalczyk, Łukasz & Kaczmarek, Łukasz, 2010

Kristensen, Reinhardt M., Michalczyk, Łukasz & Kaczmarek, Łukasz, 2010, The first record of the genus Bryodelphax (Tardigrada: Heterotardigrada: Echiniscidae) from Easter Island, Rapa Nui (Pacific Ocean, Chile) with the description of a new species, Bryodelphax aaseae, Zootaxa 2343, pp. 45-56 : 46-53

Bryodelphax aaseae sp. nov.

Figs. 3–23

Description (measurements of the holotype, adult female, Figs 5–6 , 11–12 ): Total body length without the hind legs 117.0 ( Figs 3–15 ). Body transparent to slightly rose coloured, eyes absent or not visible after the preparation. Apart from the head appendages, only lateral appendages A present. Internal cirrus 9.0 long, cephalic papilla 3.5 long ( Fig. 21 ), external cirrus 14.0 long. Cirrus A 32.0 long (27% of body length). Ventral plates smooth and arranged in 8 rows ( Figs 4 , 9–10 , 15 , 19 ). The first row (subcephalic) with 2 plates, the second row (in line with legs I) with only one triangular plate, the third and the fourth rows (on the body between legs I and II) with 4 plates each, the fifth row (in line with legs II) with 2 plates, the sixth row (on the body between legs II and III) with 4 plates, the seventh row (in line with legs III) with 2 plates and the eighth row, around the gonopore (between legs III and IV) with 4 plates. Dorsal plates covered with granulation, distinctly larger on the scapular and terminal plate ( Figs 16–18 ). Besides granulation, slightly larger and irregularly distributed pores are visible mainly on the margins of all the dorsal plates. The scapular plate facetted with a median longitudinal fold and a few smaller transverse folds ( Figs 16, 18 ). Paired plates divided into two unequal anterior and posterior parts by a transverse stripe without granulation. The terminal plate facetted with two longitudinal folds ( Fig. 17 ). Median plates 1 and 2 divided into two unequal parts. Median plate 3 undivided, and triangular in shape. Granules on median plates distinctly smaller than those on other plates.

The mouth opening surrounded by a ring of 10 papulae (clearly visible in SEM) ( Fig. 20 ). Spine on legs I absent. Buccal apparatus with a short rigid buccal tube and thin stylets. Rigid stylet supports encrusted with CaCO3.

Papilla on legs IV round and very small (sometimes difficult to see in LM) ( Fig. 22 ). Dentate collar on legs IV absent ( Fig. 22 ). Claws on legs IV are 9.0 long ( Fig. 23 ). External claws of all legs smooth, internal claws with very small spurs (1.0 long).

CHARACTER N MIN MAX MEAN SD Remarks. No males were found; however, 5 exuvia with either one or two eggs each and 7 two-clawed larvae indicate that the population in the Rano Kau Crater may reproduce by obligatory parthenogenesis. Results of a simple statistical analysis of measurements of selected morphological structures for the holotype and 11 randomly chosen specimens are given in Table 1 .

Etymology. The name ‘ aaseae ’ is given after Àse Jespersen who collected the moss sample in which the new species was found.

Type locality. Moss sample on volcanic rock ( Fig. 2 ) from the bottom of the Rano Kau Crater (27°10.996’S and 109°26.311’W), Rapa Nui/Easter Island, Pacific Ocean, Chile, 0 5 January 1989, coll. Àse Jespersen ( Figs 1–2 ).

Type depositories. Holotype (adult female and eight paratypes, slide TAR 804 ZMUC), 186 paratypes (slides TAR 805–830 ZMUC) and eight paratypes on SEM-stubs are deposited at the Zoological Museum, Natural History Museum of Denmark, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen Ø, Denmark; 18 paratypes are deposited at the Natural History Collections, Faculty of Biology, A. Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland.

Differential diagnosis. The genus Bryodelphax can be divided into two species groups with regard to the presence or absence of the ventral plates: the parvulus group (no ventral plates) and the weglarskae group (with ventral plates). Given that Bryodelphax aaseae sp. nov. has ventral plates, and therefore belongs to the weglarskae group, we differentiate it only from other species of this group.

The new species differs from all other weglarskae group species by the presence of four plates around the gonophore. Moreover, B. aaseae sp. nov. differs specifically from:

1. B. weglarskae by: having non-bifurcated external and internal buccal cirri and cirri A, the absence of a dentate collar on legs IV, the presence of four ventral plates in rows 3, 4 and 6, two ventral plates in row 5; and the presence of the mid-dorsal and some transverse folds on the scapular plate.

2. B. sinensis by: having slightly longer cirri A (up to 27.0 in B. sinensis and up to 30.0 in the new species), the presence of 8 rows of ventral plates instead of 6 and a different number of plates in each row.

3. B. iohannis by: having a smaller body size (113.9–179.5 in B. iohannis and 82.0–109.0 in the new species), longer cirri A (27.0 in B. iohannis , specimen 133.4 long and 30.0 in the new species, specimen 104.0 long); the presence of 8 rows of ventral plates instead of 9; a different number of plates in each row, and the presence of the mid-dorsal and some transversal folds on the scapular plate.

Other tardigrades in the moss sample. The very small moss sample, in which more than 200 specimens of B. aaseae sp. nov. were found, also contained three other tardigrade species belonging to three different genera: Macrobiotus cf. hufelandi , Milnesium cf. tardigradum and Pseudechiniscus cf. novazeelandiae.

Figures

FIGURES 3 – 6. Bryodelphax aaseae sp. nov. Habitus: 3, dorsal view; 4, ventral view; 5, ventro-lateral view; 6, lateral view. (3 – 4, paratypes; 5 – 6, holotype). Drawings made by using camera lucida.

FIGURES 7 – 8. Bryodelphax aaseae sp. nov. Habitus: 7, dorso-lateral view; 8, dorsal view. (DIC, paratypes).

FIGURES 9 – 10. Bryodelphax aaseae sp. nov. Ventral plates. (DIC, paratypes).

FIGURES 11 – 12. Bryodelphax aaseae sp. nov. Holotype, habitus: 11, dorso-lateral view; 12, lateral view. (PCM).

FIGURES 13 – 15. Bryodelphax aaseae sp. nov. Habitus: 13, dorsal view; 14, lateral view; 15, ventral view. (SEM, paratypes).

FIGURES 16 – 19. Bryodelphax aaseae sp. nov. 16, scapular plate; 17, terminal plate; 18, a fragment of the scapular plate; 19, a pair of ventral plates between legs II and III. (SEM, paratypes).

FIGURES 20 – 23. Bryodelphax aaseae sp. nov. 20, mouth opening with a ring of ten papulae; 21, cephalic papilla (secondary clava); 22, papilla on legs IV; 23, claws IV. (SEM, paratypes).

FIGURES 1 – 2. Type locality: Rano Kau Crater, Easter Island / Rapa Nui, 5 January 1989 with the collector Åse Jespersen.

Tables

TABLE 1. Measurements [in µm] of selected morphological structures of specimens of Bryodelphax aaseae sp. nov. mounted in Hoyer’s medium (min and max refer to the smallest and the largest structure found among all measured specimens).

Body	13	82.0	–	117.0	97.9	10.0
Cirrus internus Cephalic papilla (secondary)	12 6	6.5 2.0	– –	10.0 3.5	8.0 2.8	1.1 0.5
Cirrus externus	13	10.0	–	14.0	12.3	1.3
Cirrus A Clava (primary)	13 8	24.0 2.0	– –	32.0 3.0	28.1 2.9	2.9 0.4
Claw	11	6.0	–	9.0	6.7	0.9
Spur Cirrus A/Body	11 13	0.8 0.24	– –	1.1 0.34	1.0 0.29	0.1 0.03
Cirrus int/ext	12	0.54	–	0.80	0.64	0.09
Cirrus int/A Cirrus ext/A	12 13	0.22 0.37	– –	0.38 0.50	0.28 0.44	0.04 0.04
Spur/Claw	11	0.11	–	0.17	0.15	0.02