Macrobiotus tehuelchensis, Rossi, Gustavo, Claps, Maria & Ardohain, Diego, 2009

Rossi, Gustavo, Claps, Maria & Ardohain, Diego, 2009, Tardigrades from northwestern Patagonia (Neuquén Province, Argentina) with the description of three new species, Zootaxa 2095, pp. 21-36 : 28-32

Macrobiotus tehuelchensis sp. nov.

Figs. 3 and 4

Material examined: The holotype and paratypes are from moss and lichen samples from soil collected near Ñorquinco Pond, Aluminé, ca. 1000 m asl, in January, 2005.

Type repository: The holotype (slide N° Nq. 10.6) is preserved at the Museum of La Plata (La Plata University). The paratypes are preserved in the collection of G. Rossi and M.C. Claps.

Specific diagnosis: Macrobiotus with oral-cavity armature of the echinogenitus type and claws of the hufelandi type, three macroplacoids, and a microplacoid; without eye spots; and with small smooth lunules on all legs. The eggs have conical processes with a slender, translucent, and flexible distal portion. The egg shell is not visible.

Description of the holotype: The colorless body has a length of 494 µm, eye spots are absent, and the cuticle is smooth ( Fig. 3 A). The mouth is terminal and the buccal tube rigid with ventral lamina ( Fig. 4 A). The buccal armature corresponds to the echinogenitus type ( Pilato, 1972), resembling the mouth of Macrobiotus pallari Maucci 1954 with 10 large peribucal lamellae, an anterior band of numerous small, fine teeth all around the wall. The posterior band of teeth is formed by 3–4 rows of larger teeth than those present in the anterior band but smaller than those of the posterior band. The median ventral ridge is rectangular in shape and nearly the same size as the dorsal ridge. The ventrolateral and dorsal ridges always have smooth margins ( Fig. 3 B). The buccal tube is 67 µm long and 12.4 µm wide (pt = 18.5); the pharyngeal bulb has apophyses, three macroplacoids, and a well developed microplacoid ( Figs. 3 C, 4A). The insertion of the stylets is at 47.1 µm (pt = 70.4). The lengths of the macroplacoids are 9.9 µm (pt = 14.8), 8.7 µm (pt = 13.0), 8.7 µm (pt = 13.0); that of the microplacoid, which is separate from the third macroplacoid, is 5.0 µm (pt = 7.4). The lengths of the entire placoid and macroplacoid rows are 37.2 µm (pt = 55.6) and 32.2 µm (pt = 48.1), respectively. The claws are of the hufelandi type with thin accessory points on the main branches, and small lunules with smooth margins are also present in the fourth pair of legs ( Figs. 4 B, 4C).

The eggs, laid freely, are a translucent white-gray and are spherical with conical processes (nine on each egg circumference). The mean diameters excluding and including processes are 77 and 150 µm, respectively. The processes have a slender, translucent and flexible distal portion with parallel linear markings ( Fig. 4 D).

The maximum length of each complete process is nearly 50 µm, the cone 10–15 um, and the translucent distal portion 30–40 µm. The bases are reticulated, irregular, and with a diameter of 24–26 µm. The shell is apparently the continuation of the striation of the processes ( Figs. 4 D, E).

We found one egg with an embryo, thus allowing us to confirm that the eggs are definitely from M. tehuelchensis ( Fig. 4 F).

Etymology: The species is named after the extinct aboriginal inhabitants of the Patagonia (the Tehuelches).

Differential diagnosis: Depending on the measurements of the macroplacoids, this species may be identified as a different species with respect to Macrobiotus richtersi Murray, 1911 or to Macrobiotus liviae Ramazzotti, 1962 . The differences from these species are the points of insertion of the stylets, the pt of the buccal tube width, and the size of the micoplacoid. The main difference resides in the structure of egg processes, which are more numerous and truncate in M. richtersi and without the distal portion in M. liviae . The new species is similar to Macrobiotus mauccii Pilato, 1974 , but differs from that species by having a wider buccal tube, longer macroplacoids, and a smaller microplacoid. Moreover, M. tehuelchensis sp. nov. has much longer claws than those mentioned for M. mauccii , and the eggs also show clear differences from those described for that species. Macrobiotus tehuelchensis sp. nov. differs from Macrobiotus snaresensis Horning Schuster & Grigarick, 1978 by the length and width of the buccal tube, the size of the macroplacoids, the separate microplacoid, and the claws, as well as the morphologic characteristics of the eggs.

Remarks: The paratypes of this species have the same qualitative characteristics as the holotype. The dimensions of some structures of the specimens are indicated in Table 4 .

Figures

FIGURE 3. Macrobiotus tehuelchensis sp. nov. A, habitus; B, buccopharyngeal apparatus in lateral view; C, buccopharyngeal apparatus in ventral view.

FIGURE 4. Macrobiotus tehuelchensis sp. nov. A, buccopharyngeal apparatus. B, claws of the fourth pair of legs; C, detail of a claw, showing the lunule; D, detail of the egg processes; E, egg; F, egg with embryo.

Tables

TABLE 4. Measurements [in µm] and pt values of selected morphological structures of the holotype and mean values of other measured specimens (n = 7) of Macrobiotus tehuelchensis sp. nov. (minimum and maximum refers to the smallest and the largest structure found among all measured specimens; SD, standard deviation).

Body length	Holotype 494.0	Mean 484.7	S. D. 111.8	Minimum 316.0	Maximum 666.0
Buccal tube length	67.0	66.3	7.9	57.0	79.4
Buccal tube width pt	12.4 18.5	11.7 17.5	2.1 1.4	9.9 14.8	14.9 18.8
Stylet supports insertion	47.1	47.8	4.7	42.2	54.6
pt Entire placoid row	70.4 37.2	72.4 34.1	2.1 6.8	68.8 27.3	74.1 42.2
pt	55.6	53.5	4.6	47.8	58.6
Macroplacoid row pt	32.2 48.1	33.9 46.7	1.4 2.6	32.2 43.8	34.7 48.3
Macroplacoid 1	9.9	9.7	2.0	7.4	12.4
pt Macroplacoid 2	14.8 8.7	14.6 8.1	1.6 1.0	13.0 7.4	17.2 9.9
pt	13.0	12.3	0.8	11.1	13.0
Macroplacoid 3 pt	8.7 13.0	8.6 12.9	1.5 0.9	7.4 11.5	11.2 14.1
Microplacoid	5.0	5.8	1.3	5.0	7.4
pt	7.4	8.5	1.2	7.4	10.3
Claw 1 primary branch	14.9	16.1	1.8	14.9	17.4
pt	22.2	23.2	1.4	22.2	24.1
Claw 1 secondary branch pt	12.4 18.5	12.4 17.9	0.0 0.9	12.4 17.2	12.4 18.5
Claw 2 primary branch	14.9	16.1	1.8	14.9	17.4
pt Claw 2 secondary branch	22.2 12.4	23.2 13.6	1.4 1.8	22.2 12.4	24.1 14.9
pt	18.5	19.6	1.5	18.5	20.7
Claw 3 primary branch pt	17.4 25.9	17.4 25.0	0.0 1.3	17.4 24.1	17.4 25.9
Claw 3 secondary branch	14.9	14.9	0.0	14.9	14.9
pt Claw 4 primary branch	22.2 17.4	21.5 16.9	1.1 2.9	20.7 12.4	22.2 19.8
pt	25.9	26.3	2.9	21.7	30.8
Claw 4 secondary branch pt	14.9 22.2	13.6 21.2	2.6 2.4	9.9 17.4	17.4 24.1