Macrobiotus martini, Bartels, Paul J., Pilato, Giovanni, Lisi, Oscar & Nelson, Diane R., 2009

Bartels, Paul J., Pilato, Giovanni, Lisi, Oscar & Nelson, Diane R., 2009, Macrobiotus (Eutardigrada, Macrobiotidae) from the Great Smoky Mountains National Park, Tennessee / North Carolina, USA (North America): two new species and six new records, Zootaxa 2022, pp. 45-57 : 47-49

Macrobiotus martini sp. nov.

Figs. 2–3

Type locality: Indian Gap ATBI plot (W 83o 26.6242’, N 35o 36.5423’, 1667 m asl), Great Smoky Mountains National Park, Swain County, North Carolina, USA. In lichen on a beech tree ( Fagus grandifolia ) in a beech gap forest community.

Material examined: Holotype: Indian Gap. Paratypes: Indian Gap, 22 adults and 25 eggs (2 with fully developed embryos); Tremont (54 adults and 6 eggs, 1 with fully developed embryo); Twin Creeks (34 adults, 0 eggs); Cataloochee (13 adults, 4 eggs); Snakeden Ridge (21 adults, 1 egg); Gregorys Cave (4 adults, 1 egg); Grotto Falls (5 adults, 0 eggs); Ramsey Cascade (0 adults, 1 egg); Laurel Falls (1 adult, 0 eggs); Parsons Branch Rd (1 adult, 0 eggs); Cades Cove (5 adults, 0 eggs).

Species diagnosis: Colorless; cuticle with pores, some of which are elliptical and very large; granules on the legs present; large eyes present; buccal armature in oral cavity very simple, without bands of teeth, and with only two dorsal and two ventral thin transverse ridges present (mediodorsal and medioventral ridges absent); buccal tube narrow; stylet supports inserted on the buccal tube at 73.4–74.9% of its length; two macroplacoids and small microplacoid present. Claws of the hufelandi - type; accessory points and lunules present. Eggs of the hufelandi - type with processes in the shape of inverted goblets with a terminal disc, which has a generally convex central portion, and the egg shell with a large-mesh reticulation.

Description of the holotype: Body length 450.0 µm; colorless, large eyes present; cuticle with many circular and elliptical pores, some of which are very large (up to 3.5 x 1.9 µm) and uniformly distributed ( Fig. 2 D). Some small granules are present on all legs, more evident in larger animals. Buccal-pharyngeal apparatus of the Macrobiotus - type ( Fig. 2 A). Mouth terminal with 10 small peribuccal lamellae. Buccal armature in oral cavity very simple ( Fig. 2 C); anterior and posterior bands of teeth not visible; posterior system of transverse ridges present but only two dorsal and two ventral ridges present (mediodorsal and medioventral ridges absent). Buccal tube 39.4 µm long and 5.1 µm wide (pt = 12.9). Stylet supports inserted on the buccal tube wall at 72.9% of its length (pt = 72.9). Pharyngeal bulb (43.4 µm x 34.8 µm) with apophyses, two short rod-shaped macroplacoids and a small microplacoid. First macroplacoid, with a central constriction, 8.9 µm long (pt = 22.6); second macroplacoid, 4.8 µm (pt = 12.2); microplacoid, 2.5 µm long (pt = 6.3). Entire placoid row, 19.3 µm long (pt = 49.0); macroplacoid row, 15.6 µm long (pt = 39.6).

Claws, of the hufelandi - type, well-developed ( Fig. 2 B) with accessory points on the main branches. Internal and external claws 10.4 µm long (pt = 26.4) and 10.9 µm long (pt = 27.7), respectively, on the second pair of legs; 10.7 µm (pt = 27.2) and 11.5 µm (pt = 29.2), respectively, on the third pair of legs. Anterior and posterior claws on the hind legs 12.1 µm long (pt = 30.7) and 13.1 µm long (pt = 33.2), respectively. Lunules smooth on the first three pairs of claws, but with small marginal teeth on the hind claws. Two faint cuticular bars present below the lunules on the first three pairs of legs.

The freely-laid eggs are spherical ( Fig. 3 ) with processes in the shape of inverted goblets with a terminal disc. There are 20–23 processes around the circumference and 64–70 in the hemisphere. Egg diameter 61.6–101.7 µm (mean = 81.7 µm, n = 8) excluding the processes, and 69.9–112.5 µm (mean = 89.1 µm, n = 8) including them. Processes 3.0–5.8 µm in height (mean = 4.2 µm, n = 8); basal diameter 4.7–6.8 µm (mean = 6.1 µm, n = 9); terminal disc diameter 2.5–5.0 µm (mean = 3.9 µm, n = 9). Egg shell, between processes, with regular reticulated ornamentation with large meshes; generally the meshes around base of processes distinctly larger ( Fig. 3 D).

Remarks: In some eggs we noted a slight variability in the height and basal diameter of the processes ( Fig. 3 C arrow, 3D) and the width of the terminal disc. The distal portion of the processes may appear slightly different in shape in different focus positions; the central portion of the terminal disc often appears as a convex area ( Fig. 3 A), but in another focus position, the margin of this disc is slightly indented with small teeth that often are difficult to see ( Fig. 3 B, arrows).

Other adults (paratypes) are similar to the holotype, but in some populations the elliptical cuticular pores may be larger than in the holotype. Measurements and pt values of selected morphological structures in the smallest and the largest specimens examined are given in Table 1 .

Etymology: The name ‘ martini ’ is in honor of Mr. Robert Martin, founder of Martin Microscope Company, in appreciation of his long-term support of tardigrade research through the loan of microscopes and in particular for his enthusiasm in displaying tardigrades in his microscopy exhibits at regional meetings, especially the Association of Southeastern Biologists.

Type depositories: The holotype ( USNM # 1120688) and 3 paratypes ( USNM # 1120689, 1120690, and 1120691 (egg)) are deposited in the National Museum of Natural History, Smithsonian Institution, Washington, DC, USA. The remaining paratypes are deposited in the GSMNP collection; the Nelson collection in the Department of Biological Sciences, East Tennessee State University, Johnson City, Tennessee, USA; and the Binda and Pilato collection in the Department of Animal Biology, University of Catania, Catania, Italy.

Differential diagnosis: Macrobiotus martini sp. nov. differs from all other species of the hufelandi group in having a very simple buccal armature without bands of teeth and with laterodorsal and lateroventral transverse ridges but without mediodorsal and medioventral transverse ridges. It also differs by having both small cuticular pores and some very large elliptical pores ( Fig. 2 D), and in having a low pt index for the stylet supports (73.4–74.9 in the measured specimens) and for the macroplacoid row (34.9–39.6 in the measured specimens). In addition the eggs are characterized by having the central portion of the terminal disc generally convex ( Fig. 3 A) and with marginal teeth visible only in some positions.

Comments: In addition to the holotype and paratypes used for the description of the species in this paper, additional specimens of Macrobiotus martini have been identified within the park. The total is now 546 specimens, although we expect to find many more as we sort through additional slides of the M. hufelandi group. So far, all M. martini specimens have been found in mosses and lichens on trees and rocks. None have been found in samples from soil/leaf litter or in aquatic habitats.

Figures

FIGURE 2. Macrobiotus martini sp. nov. A, buccal-pharyngeal apparatus of the holotype. B, claws of the third pair of legs (holotype). C, buccal-pharyngeal apparatus (paratype) where the absence of the mediodorsal ridge in the buccal armature is evident. D, cuticular pores and claws of the fourth pair of legs (paratype). (Scale bars = 10.0 µm)

FIGURE 3. Macrobiotus martini sp. nov. A – B, details of the same egg in two different focus positions; the arrow indicates the indentation of the terminal disc. C, detail of the egg where variation is evident in the size and the shape of the processes; the arrows indicate a large and a small process. D, reticular design of the egg shell; variation in the size and shape of the processes and the terminal discs is evident. (Scale bars = 10.0 µm)

Tables

TABLE 1. Macrobiotus martini sp. nov. metric characters (all values in µm, pt ratios in brackets).

	smallest specimen	largest specimen
Body length	283.0	450.0
Buccal tube length	32.7	39.4
Buccal tube width	4.1 [12.5]	5.1 [12.9]
Stylet supports	24.3 [74.3]	28.7 [72.9]
Placoid row	14.5 [44.3]	19.3 [49.0]
Macroplacoid row	11.4 [34.9]	15.6 [39.6]
First macroplacoid	6.8 [20.8]	8.9 [22.6]
Second macroplacoid	4.1 [12.5]	4.8 [12.2]
Microplacoid	2.1 [6.4]	2.5 [6.3]
Internal claw II	8.1 [24.8]	10.4 [26.4]
External claw II	8.2 [25.1]	10.9 [27.7]
Internal claw III	8.5 [26.0]	10.7 [27.2]
External claw III	8.5 [26.0]	11.5 [29.2]
Anterior claw IV	9.3 [28.4]	12.1 [30.7]
Posterior claw IV	9.7 [29.7]	13.1 [33.2]