Macrobiotus neuquensis, 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 : 24-28

Macrobiotus neuquensis sp. nov.

Figs. 1–2

Material examined: The holotype and the paratypes are from moss samples on soil and rock collected in Hua Hum, Junín de los Andes, at ca. 700 m asl (40°07’S 71°39’ W), and from mosses on soil and lichen on a tree near Rucachoroi Lake, Aluminé, at ca. 900 m asl (39°12’ S, 70°55’ W), collected in December, 2004.

Type repository: The holotype (slide N° Nq. 6.6) 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 an oral-cavity armature of the harmsworthi type, three macroplacoids, and one microplacoid; with eye spots, cuticle smooth, legs without granulation, claws of the hufelandi type, lunules smooth on all legs, the presence of a cuticular bar on the first three pairs of legs, and a refractile zone. These structures are less visible on the fourth pair of legs. The eggs have conical processes with reticular sculpture, all of them in contact with each other. The chorion is invisible.

Description of the holotype: The body length is 503.4 µm. The body ( Fig. 1 A) is transparent (white) with eyes in anterior position ( Fig. 2 A). The cuticle is smooth, without pores or pearls. The mouth is anterior and surrounded by a ring of 10 peribuccal lamellae. The oral-cavity armature is of the harmsworthi type. The teeth of the anterior band—or first band according to the Michalczyk and Kaczmarek (2003) terminology—are smaller, within the anterior border, and are in contact with the lamellae. The posterior band of teeth in the shape of a crown (second band) consists of conical teeth with granules in the posterior portion. The transverse ridges (third band) are small, while the laterals have a smooth margin. The buccal tube is 52 µm long and 10 µm wide (pt = 19.2) ( Figs. 1 B, 2A). Stylet supports are inserted on the buccal tube at 38 µm (pt = 73). The pharyngeal bulb is oval with distinct, triangular apophyses, three macroplacoids, and a microplacoid. The first macroplacoid is wider in the middle section, its length being 9.3 µm (pt = 17.8); the second, more pyramidal, is 8.2 µm long (pt = 15.7); the third is 10.2 µm long (pt = 19.6) and with a structurally different constriction in its terminal part. The microplacoid is 6 µm long (pt = 11.5) and separate from the third macroplacoid. The macroplacoid row is 28 µm long (pt = 53.8; Figs. 1 B, 2A). The claws are of the hufelandi type, having primary branches with distinct accessory points ( Fig. 2 B). The lunules are smooth on all legs ( Fig. 2 C). Between the lunules and the refractile zone of the first three pairs of legs there is a cuticular bar ( Fig. 2 B), only visible under phase contrast or by DIC and not detected on the fourth pair of legs. On the first pair of legs, the primary branch has a basal portion and measures 12 µm (pt = 23.0), while the secondary branch is 10.5 µm long (pt = 20.1). On the second pair of legs, the primary and secondary branches are 12 (pt = 23.0) and 10 µm (pt = 19.2), respectively. On the third and fourth pair of legs, these branches measure 11 (pt = 21.1) and 8 µm (pt = 15.3) and 11 (pt = 21.12) and 9 µm (pt = 17.3), respectively.

The eggs, laid freely, are spherical and contain conical processes having a truncated apex ( Fig. 2 D). The processes, 9–12 around the circumference, have a 10–25 µm diameter at their base ( Fig. 2 F). The surface of the processes contains dense and uniform reticular sculpture with isodiametric meshes ( Fig. 2 E). The bases of the processes are in contact, and the union with the shell is by either connecting cords or a continuation of the sculpture itself, for this reason the shell is not visible ( Fig. 2 F). The processes are 7–15 µm height. We found one egg with an embryo ( Table 2 ), thus allowing us to confirm that the eggs are without a doubt from M. neuquensis sp. nov. ( Fig. 2 D).

Etymology: The name neuquensis refers to the province that includes the locus typicus of this new species.

Differential diagnosis: Macrobiotus neuquensis sp. nov. belongs to the harmsworthi group, whose species exhibit the following characteristics in common: three macroplacoids in the form of an arch, a microplacoid in the pharyngeal bulb, plus a cuticle without pores. The presence of the cuticular bar and a refractile zone in the legs along with the eggs having conical processes in contact with one another are the principal characteristics differentiating M. neuquensis sp. nov. from the other species of the group.

This new species is similar to Macrobiotus chieregoi Maucci & Durante 1980 , but differs from the latter by having eyes and a wider buccal tube. In addition, the processes of the eggs of M. neuquensis sp. nov. are shorter than those of M. chieregoi . Macrobiotus neuquensis sp. nov. differs from Macrobiotus krynauwi Dastych & Harris 1995 in having a smooth cuticle without pearls, a longer and wider buccal tube, bigger macroplacoids, and smaller claws. Macrobiotus neuquensis sp. nov. also differs from Macrobiotus blocki Dastych 1984 and Macrobiotus ovostriatus Pilato & Patané 1998 with respect to the characteristics of the eggs ( Table 3 ). Macrobiotus neuquensis sp. nov. is furthermore unlike Macrobiotus reinhardti Michalczyk & Kaczmarek 2003 in having a shorter third macroplacoid, a wider buccal tube, and longer processes on the eggs, among other morphological features.

Remarks: Measurements and pt values of selected morphological structures for all specimens are presented in Table 2 .

Diameter 87–94 42–55 69–84 43–82 70–90 64–70 98–115 without

processes

Figures

FIGURE 1. Macrobiotus neuquensis sp. nov. A, habitus; B, buccopharyngeal apparatus.

FIGURE 2. Macrobiotus neuquensis sp. nov. A, buccopharyngeal apparatus; B, detail of claws showing cuticular bars; C, detail of claws showing lunules and accessory points; D, egg with embryo; E, detail of egg processes; F, detail of egg sculpture, showing the bases of the processes in contact.

Tables

TABLE 2. Measurements [in µm] and pt values of selected morphological structures of the holotype and mean values of other measured specimens (n = 23) of Macrobiotus neuquensis sp. nov. (minimum and maximum refers to the smallest and the largest structure found among all measured specimens; SD, standard deviation).

Body length	Holotype 503.4	Mean 437.5	S. D. 92.2	Minimum 285.0	Maximum 570.4	Embryonaded egg
Buccal tube length	52.0	50.2	10.6	37.1	69.4	32.0
Buccal tube width pt	10.0 19.2	9.5 19.3	1.7 3.2	7 15.1	12.4 26.7	4.8 15.5
Stylet supports insertion	38.0	38.5	8.0	28.7	52.0	25.0
pt Entire placoid row	73.0 34.0	76.8 32.2	2.1 8.2	73.1 22.3	79.5 44.8	78.1 15.5
pt	65.3	64.0	4.1	57.6	70.2	50.0
Macroplacoid row pt	28.0 53.8	25.1 49.7	6.8 3.8	16.8 44.7	34.7 56.0	12.2 39.4
Macroplacoid 1	9.3	8.0	1.9	4.9	10.4	3.3
pt Macroplacoid 2	17.8 8.2	15.9 6.5	2.0 1.6	13.2 4.9	19.1 9.1	10.6 3.0
pt	15.7	13.1	1.7	10.4	15.8	9.7
Macroplacoid 3 pt	10.2 19.6	8.5 17.2	1.8 1.8	5.9 15.0	11.1 20.4	3.3 10.6
Microplacoid	6.0	4.9	1.5	2.7	7.4	1.8
pt Claw 1 primary branch	11.5 12.0	9.8 13.	1.8 4.4	7.0 8.5	11.5 19.8	5.8
pt	23	27.8	3.2	21.2	29.8
Claw 1 secondary branch pt	10.5 20.1	10.9 20.0	3.5 3.1	6.0 16.2	17.3 24.9
Claw 2 primary branch	12.0	13.7	5.0	8.0	22.3
pt Claw 2 secondary branch	23.0 10.0	25.0 10.9	4.1 3.6	21.2 6.5	32.1 17.3
pt	19.2	20.1	2.8	17.3	24.9
Claw 3 primary branch pt	11.0 21.1	13.6 24.4	4.8 3.6	8.0 20.5	19.8 29.8
Claw 3 secondary branch	8.0	11.2	3.8	7.0	17.3
pt Claw 4 primary branch	15.3 11.0	20.6 15.1	3.1 5.0	15.4 9.0	24.9 24.8
pt	21.1	32.0	13.2	21.2	67.1
Claw 4 secondary branch pt	9.0 17.3	11.6 21.1	3.8 3.1	7.0 17.3	17.3 26.1
Pharyngeal bulb length	65.2	65.7	4.3	62.0	69.4
Pharyngeal bulb width	52.8	53.1	1.3	52.0	54.5