Macrobiotus rigidus, Pilato, Giovanni & Lisi, Oscar, 2006

Pilato, Giovanni & Lisi, Oscar, 2006, Macrobiotus rigidus sp. nov., new species of eutardigrade from New Zealand, Zootaxa 1109, pp. 49-55: 50-54

publication ID

http://doi.org/ 10.5281/zenodo.273346

publication LSID

lsid:zoobank.org:pub:28169FC7-8220-4A55-BF9F-C378BDA88B1F

persistent identifier

http://treatment.plazi.org/id/0399D06F-A109-FF84-DF69-FB15A0F9F965

treatment provided by

Plazi

scientific name

Macrobiotus rigidus
status

sp. nov.

Macrobiotus rigidus   sp. nov. ( Fig. 1 View FIGURE 1 )

Type locality. North Island: Mt. Egmont National Park, the Plateau, one specimen from a sample of Sticta   sp. (lichen) on Coprosoma.

Material examined. Holotype, North Island, type locality. North Island, Porewa: one specimen from a sample of Camptochaete angustata   (moss) on a dead tree. South Island: Seaward Bush Scenic Reserve, near Invercargill, one egg from a sample of mixed cryptogams on live trees.

Species diagnosis. Cuticle smooth without pores; very small dots present on the hind legs; eye spots absent; buccal armature and placoids of harmsworthi   type; many ventral supplementary teeth present; stylet supports inserted on the buccal tube at 76.0– 77.7 % of its length; claws of hufelandi type with accessory points and lunules; eggs with conical processes, each with a not flexible nor subdivided tapering terminal portion, and a basal ring of digitations that appear as a ring of basal dots; processes’ surface with a reticular sculpture; egg shell with dots that seem to continue the basal digitations.

Description of the holotype. Body length 530 m (but the specimen is in moulting), colourless; cuticle smooth without pores; very small dots present on the hind legs; eye spots absent (according to Horning et al., 1978). Buccopharyngeal apparatus ( Fig. 1 View FIGURE 1 A) of Macrobiotus   type (buccal tube rigid with ventral lamina, ten peribuccal lamellae present). An anterior band of fine teeth, a posterior ring of triangular teeth (and many ventral supplementary teeth) and a system of three dorsal and three ventral transverse ridges are present in the buccal cavity wall. Buccal tube 46.4 m long and 8.2 m wide (pt = 17.7). Stylet supports inserted on the buccal tube wall at 76.0% of its length (pt = 76.0). Pharyngeal bulb with well­developed apophyses, three rod­shaped macroplacoids (the third of which has a subterminal narrowing) and a microplacoid. Placoid disposition of harmsworthi   type. Placoid row 28.0 m long (pt = 60.3) including the microplacoid, 22.8 m (pt = 49.1) excluding it; first macroplacoid 7.3 m long (pt = 15.7), second 5.3 m (pt = 11.4), third 6.0 m (pt = 12.9), microplacoid 4.2 long m (pt = 9.0).

Claws, of the hufelandi type, short, stout, and with well­developed accessory points on the main branches ( Fig. 1 View FIGURE 1 B, C). External and internal claws on the third pair of legs 10.9 m (pt = 23.5) and 10.3 m (pt = 22.2) long respectively; anterior and posterior claws on the hind legs 13.4 m (pt = 28.9) and 14.2 m (pt = 30.6) long respectively. Smooth lunules present. A cuticular bar present near the lunules on the first three pairs of legs. The paratype is similar in shape to the holotype. Table 1 shows the dimensions of some structures of the two measured specimens.

Eggs, freely laid, spherical ( Fig. 1 View FIGURE 1 D, E), with conical processes (12 around the circumference, 27 in the hemisphere in the egg we examined). Diameter excluding processes 64 m, 91 m including them. Processes conical with an abruptly thinning distal portion, not flexible, never subdivided. Processes 15.2–16.2 m long, basal diameter 14.5–15.2 m. Surface of each process with reticular sculpture made up of small, almost isodiametric, meshes. Base of each process with some short digitations that appear as a ring of dots. Egg shell dotted with many dots that seem to continue the basal digitations ( Fig. 1 View FIGURE 1 E).

Etymology. The name rigidus   (= rigid) refers to the fact that the egg processes are not flexible.

Remarks. Macrobiotus rigidus   sp. nov. belongs to the harmsworthi   group and in particular to a group of species having, like M. coronatus   , the egg processes with basal digitations that form a ring of well evident dots.

It differs from M. coronatus   ( Fig. 2 View FIGURE 2 A –D) by lacking eye spots, by having almost invisible cuticular dots only on the hind legs; by having a slightly smaller microplacoid ( Table 1), stouter claws, accessory points more developed, and in some characters of the eggs (larger diameter, terminal portion of egg processes not flexible, not subdivided and never broken; basal ring of dots and ornamentation of egg shell slightly less evident).

The new species differs from M. simulans   in the following features: eye spots absent, small cuticular dots (almost invisible) only on the hind legs; ventral supplementary teeth present caudal to the ring of triangular teeth; smaller microplacoid ( Table 1) and some characters of the eggs (terminal portion of egg processes longer, not flexible and never broken; ring of basal digitations of egg processes more evident; the dots of egg shell, more evident, seem to continue the basal digitations).

M. rigidus   sp. nov. differs from M. patiens   in the following features: small cuticular dots (almost invisible) only on the hind legs; ventral supplementary teeth present caudal to the ring of triangular teeth; shorter microplacoid ( Table 1); stouter claws and some characters of the eggs (terminal portion of the egg processes longer, not flexible and never broken, basal digitations of egg processes more evident, the dots of the eggs shell, more evident, seem to continue the basal digitations).

The new species differs from M. harmsworthi   by lacking eye spots, by having more numerous ventral supplementary teeth, slender buccal tube, first macroplacoid slightly shorter ( Table 1), and in some characters of the eggs (processes with longer and not flexible terminal portion, basal digitations more developed, the dots of egg shell seem to continue the basal digitations).

M. rigidus   sp. nov. is also similar to M. pseudocoronatus   but it differs from it in the following features: cuticle smooth, eye spots absent, small dots (almost invisible) only on the hind legs; ventral supplementary teeth present caudal to the ring of triangular teeth; smaller microplacoid (pt = 8.7 –9.0 in M. rigidus   sp. nov., 10.8–11.5 in M. pseudocoronatus   ) and some characters of the eggs (processes larger, each with a terminal portion not flexible, not subdivided in filaments and never broken, basal digitations more developed, the dots of the egg shell seem to continue the digitations).

The new species differs from M. radiatus   by having a slightly narrower buccal tube ( Table 1); buccal armature with more numerous ventral supplementary teeth; second and third macroplacoids and microplacoid slightly shorter ( Table 1), and in some characters of the egg (they are smaller, with conical processes with a tapering and not indented terminal portion).

The presence of M. coronatus   in New Zealand needs to be confirmed. The results of this research seem to confirm the opinion of Pilato et al. (2000) who wrote: “ Macrobiotus coronatus   is surely present in South America; its presence in other geographical areas, in our opinion needs to be confirmed”.

TABLE 1. Minimum and maximum dimensions of some structures of M. rigidus sp. nov. (n = 2), M. coronatus (12), M. simulans (11), M. patiens (8), M. radiatus (6) and M. harmsworthi (8).

  rigidus   sp.nov.         harmsworthi
    11.5–15.8 17.6–21.1 17.8–21.1 17.5–20.1  
    13.9–22.5 19.8–23.5 18.1–28.5 18.3–30.3  
    49.1–59.7 52.4–59.2 55.1–62.5 58.5–64.1  
    10.7–19.2 15.1–18.9 14.1–21.9 14.7–24.3  
    39.8–50.9 40.1–46.9 42.7–48.9 46.1–51.4  
    10.6–13.8     13.5–14.2  
    11.1–15.4   12.5–14.6 13.8–17.6  
        10.4–12.9    
    27.3–30.5 21.6–24.9 26.5–31.3 26.8–31.9  
        10.1–14.6