Macrobiotus creber Pilato & Lisi, 2009, sp. n.

Macrobiotus creber sp. n.

Fig. 1

Material examined: Praslin Island, south of Mount Cabris, holotype (slide No. 5270), 18 paratypes and 5 eggs (with fully developed embryo) in a sample of mosses on soil; Silhouette, primary coastal forest (1 egg) in a leaf-litter sample; Grande Soeur, 1 egg in a leaf-litter sample; Petite Soeur, 2 eggs with fully developed embryo in a leaf-litter sample; Bird Island, 1 egg in a leaf-litter sample; Round Island (Praslin), 15 specimen and 10 eggs in a leaf-litter sample.

Type repository: Holotype and paratypes are deposited in the Collection of Binda and Pilato (Museum of the Department of Animal Biology, University of Catania).

Species diagnosis: Cuticle smooth with neither pores nor fine granulation; eye spots absent; buccopharyngeal apparatus of Macrobiotus type; buccal armature with ten peribuccal lamellae, an anterior band of rounded teeth, a posterior ring of triangular teeth and a system of three dorsal and three ventral transversal ridges; stylet supports inserted on the buccal tube at 80–81 % of its length. Pharyngeal bulb with apophyses, three rod-shaped macroplacoids and a large microplacoid. Claws, of hufelandi type, slender; smooth lunules present. Eggs laid freely; egg processes with a trunco-conical basal portion and distal portion once or twice divided (the subdivision may be dichotomic or multiple) with small terminal branches; egg shell with a delicate reticular design with tiny, rounded meshes.

Description of the holotype: Body length about 260 µm, colorless, eye spots absent, cuticle smooth without pores. Fine dots on the legs absent.

Mouth opening terminal with 10 small peribuccal lamellae, an anterior band of rounded teeth, a posterior ring of teeth and a system of three dorsal and three ventral transversal ridges; the medio-ventral ridge is subdivided into two teeth, after which a few small supplementary teeth are also present; buccal tube 36.3 µm long and 6.5 µm wide (pt = 17.9) (Fig. 1 A); stylet supports inserted on the buccal tube at 80.0 % of its length (pt = 80).

Pharyngeal bulb (29.4 µm x 22.7 µm) with apophyses, three rod-shaped macroplacoids and a large microplacoid (Fig. 1 A). First macroplacoid, with a central constriction, 5.4 µm long (pt = 14.9); second one, slightly shorter, 4.2 µm long (pt = 11.6); third macroplacoid 5.3 µm long (pt = 14.6). Microplacoid very large, 4.3 µm long (pt = 11.9). Entire placoid row 19.3 µm long (pt = 53.2), macroplacoid row 15.5 µm long (pt = 42.7).

Claws of hufelandi type, long and slender (with short common basal portion) (Fig. 1 B); internal and external claws of the second and third pairs of legs 8.8 µm (pt = 24.2) and 10.2 µm (pt = 28.1) long respectively; anterior claws on the fourth pair of legs 10.1 µm (pt = 27.8), posterior claws of the same pair of legs 11.3 µm long (pt = 31.1). Main branches of claws with well developed accessory points. Small, smooth lunules present on all legs. A cuticular thickening is present below the lunules on the first three pairs of legs.

Eggs laid freely, spherical, with a large number of small processes slightly variable in shape and dimensions (Fig. 1 C–F). Diameter of the eggs 52–60 µm excluding processes, 59–66 including these structures; 27–30 processes are present around the circumference (about 130 in the hemisphere of the largest eggs); they have a trunco-conical basal portion and a distal portion once or twice divided (the subdivision may be dichotomic or multiple) with small terminal branches. They are 5.8–6.6 µm high with a basal diameter 4.5–6.6 µm long in the largest eggs. The base of the processes has very small digitations to the egg shell appearing as a ring of dots (Fig. 1 F). Egg shell with a delicate reticular design with tiny, rounded meshes (Fig. 1 F).

Remarks: The paratypes are similar to the holotype in both qualitative and metric characters; the dimensions of some structures of the smallest and of the largest measured specimens are given in Table 2. In the holotype and the examined paratypes the medioventral ridge of the buccal armature is subdivided into two teeth but, considering the individual variability of this structure in other species, we cannot exclude that in other specimens there may be an undivided ridge. The egg processes show a degree of individual variability in the shape (Fig. 1 C–F).

Macrobiotus creber sp. n.

Etymology: The name creber (= frequent) refers to the fact that the species is present in many islands of the archipelago.

Differential diagnosis: Macrobiotus creber sp. n. differs from M. furciger in lacking eye spots, in having wider buccal tube, stylet supports inserted on the buccal tube in a more caudal position, longer microplacoid (Table 3) and in some characters of the eggs: they are smaller, have more numerous and smaller processes (Table 4) with shorter terminal branches, without refracting areas (Figs. 1 C–F and 2A).

creber sp. n. furciger aradasi divergens sicheli orcadensis The new species differs from M. aradasi in lacking eye spots, in having wider buccal tube, stylet supports inserted on the buccal tube in a more caudal position, longer microplacoid (Table 3) and in some characters of the eggs: they are smaller, have more numerous and smaller processes (Table 4), with shorter terminal branches, and reticular design of the egg shell with more evident meshes (Figs. 1 C–F and 2B).

It differs from M. divergens in having stylet sheaths not diverging, stylet supports inserted on the buccal tube in a more caudal position, longer microplacoid, longer claws (Table 3) and in some characters of the eggs: in M. creber sp. n. they have more numerous processes (Table 4) with shorter terminal branches, and reticular design of the egg shell with smaller meshes (Figs. 1 C–F and 2C).

The new species differs from M. sicheli in lacking eye spots, in having longer claws (Table 3) and in some characters of the eggs: in M. creber sp. n. they are smaller, with more numerous and smaller processes with shorter basal diameter (Table 4) and with a less evident basal ring of dots; egg shell with a more regular reticular design (Figs. 1 C–F and 2D).

The type material of Macrobiotus orcadensis is lost (Van der Land, 1966), and for comparison, we have taken into consideration the original description, and examined one specimen and one egg from Norway attributed to this species by Durante Pasa & Maucci (1979). Macrobiotus creber sp. n. differs from Macrobiotus orcadensis in lacking eye spots, in having wider buccal tube (Table 3), buccal armature with well visible anterior band of small teeth (not visible in the examined specimen of M. orcadensis) and a posterior ring of triangular teeth more visible than that of the examined specimen of M. orcadensis; stylet supports inserted on the buccal tube in a more caudal position (pt = 80–80.9 in M. creber sp. n., 76.5 in M. orcadensis), claws longer and more slender (Table 3); and for some characters of the eggs: those of M. creber sp. n. are slightly smaller and with smaller processes (Table 4), each one with a ring of more visible basal dots (Fig. 1 C–F and 2E).

TABLE 4. Measurements (in µm) of selected morphological structures, and number of processes, of the largest measured eggs of Macrobiotus creber sp. n., M. furciger, M. aradasi, M. divergens, M. sicheli and M. orcadensis.

creber sp. n. furciger aradasi divergens sicheli orcadensis Material examined: Petite Soeur, holotype (slide No. 5245), 1 paratype and 19 eggs (one of which with fully developed embryo) in a leaf-litter sample; Mahé, Beau Vallon, 1 specimen and 1 egg, in a moss sample; Praslin, 3 specimens and 2 eggs in a moss sample.

Type repository: The type material is deposited in the collection of Binda and Pilato (Department of Animal Biology, University of Catania).

Species diagnosis: Cuticle without pores but with many very small tubercles difficult to see; eye spots present; bucco-pharyngeal apparatus of Macrobiotus type; buccal armature with ten peribuccal lamellae; an anterior band of teeth is not visible; a posterior ring of small triangular teeth and three dorsal and three ventral transversal ridges are present. Stylet supports inserted on the buccal tube at about 76% of its length. Pharyngeal bulb with apophyses, three rod-shaped macroplacoids and microplacoid. Claws of hufelandi type; accessory points, and lunules present; a faint cuticular bar below the lunules present on the first three pairs of legs. Eggs, similar to those of Macrobiotus pseudocoronatus, have conical processes with a thin, flexible, terminal portion, a basal ring of digitations forming a ring of clearly visible stripes and a reticular design with small almost isodiametric meshes; egg shell, between the processes, dotted.

Description of the holotype: Body length 350 µm; colorless; cuticle without pores but with many very small difficult to see tubercles (Fig. 3 A), and with fine dots on fourth pair of legs; small eye spots present. Bucco-pharyngeal apparatus of Macrobiotus type (Fig. 3 B); terminal mouth with ten peribuccal lamellae, a slightly evident posterior ring of small triangular teeth and a system of three dorsal and three ventral transversal ridges present in the buccal cavity; an anterior band of teeth is not visible. Buccal tube 37.6 µm long and 6.1 µm wide externally (pt = 16.2). Stylet supports inserted on the buccal tube at 75.9% of its length (pt = 75.9). Pharyngeal bulb (Fig. 3 B) (32.7 µm x 30.1 µm) with apophyses, three rod-shaped macroplacoids and microplacoid. First macroplacoid 5.0 µm long (pt = 13.3); second one 3.6 µm long (pt = 9.6); third macroplacoid 4.7 µm long (pt = 12.5); microplacoid 4.2 µm long (pt = 11.2). Entire placoid row 19.0 µm long (pt = 50.5), macroplacoid row 14.7 µm long (pt = 39.1).

Claws of hufelandi type (Fig. 3 C, D); internal and external claws of the first pair of legs 10.1 µm (pt = 26.9) and 10.2 µm (pt = 27.1) long respectively; 11.0 µm (pt = 29.3) and 11.6 µm (pt = 30.9) respectively on the third pair of legs; anterior and posterior claws of the hind legs 12.0 µm (pt = 31.9) and 12.2 µm (pt = 32.5) long respectively. Main branches of claws with well developed accessory points. Smooth lunules present on all legs. A faint cuticular thickening is present below the lunules on the first three pairs of legs.

The paratypes are similar to the holotype in both qualitative and metric characters. In Table 5 the dimensions of the smallest and of the largest measured specimens are indicated.

The eggs, laid freely, spherical, with conical processes (Fig. 3 E, F) (11–13 around the circumference, 23–29 on the hemisphere) with a large conical basal portion and a long, thin, flexible, distal portion. The base of the processes has many digitations forming a ring of clearly visible stripes (Fig. 3 E, F); the egg shell, between the processes has clearly evident dots. The surface of the processes has a reticular design with meshes of different dimensions, some of which almost isodiametric, others slightly elongated.

Etymology: The name perfidus (= perfidious, deceiving) refers to the difficulty to distinguish it from some similar species.

Macrobiotus perfidus sp.n.

Differential diagnosis: Macrobiotus perfidus sp. n. is similar to some species of the harmsworthi group but, M. pseudocoronatus excluded, it differs from them in having small cuticular tubercles. Considering that tubercles may be almost invisible, we think it opportune to stress here other differences from the species that may appear more similar to the new species. We take here into consideration only the species of the group that are colorless, with eye spots, with a ring of triangular teeth into the posterior portion of the buccal cavity, with claws not particularly long (pt up to 35), and that have non-areolated eggs with large conical processes with a reticular design, with a ring of basal dots, and with dotted egg shell. These characters considered, the species of the harmsworthi group more similar to Macrobiotus perfidus sp. n. are M. coronatus, M. simulans, M. patiens, M. rigidus and particularly M. pseudocoronatus.

Macrobiotus perfidus sp. n. differs from M. harmsworthi in having a cuticle with very small tubercles; slightly longer microplacoid (Table 6); and in some characters of the eggs: the processes have a longer and thinner terminal portion and a more visible basal ring of dots; also the egg shell granulation is more visible (Figs. 3 E, F and 4A).

perfidus sp. n. harmsworthi coronatus simulans patiens rigidus pseudocoronatus

Body length 350 320–555 203–406 222–370 240–350 225–530 342–520 Buccal tube length 37.6 35.9–57.1 26.3–37.7 29.6–40.2 33.0–47.1 33.3–46.4 41.2–53.8 Buccal tube ext. 6.1 6.5–11.3 3.1–5.6 5.5–7.3 5.9–9.9 4.8–8.2 7.6–9.4 width

pt 16.2 16.7–20.7 11.5–15.8 17.5–29.1 17.9–21.1 14.3–17.7 18.4–17.5 Stylet supp. pt 75.9 75.1–77.9 74.6–75.9 77.6–79.4 77.4–79.1 76.0–77.7 75.6–76.0 Placoid row 19.0 19.3–35.7 13.9–22.5 17.1–23.1 18.1–28.5 16.0–28.0 24.7–35.0 pt 50.5 53.3–65.4 49.1–59.7 55.1–62.8 55.1–62.5 48.1–60.3 60.0–65.1 Macroplac. row 14.5 15.9–30.0 10.7–19.2 13.2–18.6 14.1–21.9 13.1–22.8 19.5–28.2 pt 38.6 42.1–54.9 39.8–50.9 43.2–50.0 42.7–48.9 39.3–49.1 47.3–52.4 1st plac. 4.9 5.2–11.1 3.5–6.1 4.4–6.6 4.5–7.3 4.2–7.3 6.2–8.5 pt 13.0 14.3–20.3 13.0–16.2 13.8–17.2 13.8–16.5 12.6–15.7 15.0–15.8 2nd plac. 3.9 4.2–7.9 2.9–5.2 3.7–5.1 3.9–6.3 3.6–5.3 4.8–7.3 pt 10.4 10.3–14.5 10.6–13.8 11.2–13.4 11.9–13.8 10.8–11.4 11.7–13.6 3rd plac. 4.4 5.1–9.6 3.3–5.8 4.0–6.2 4.2–6.8 3.8–6.0 6.2–9.9 pt 11 13.4–17.6 11.1–15.4 13.1–16.1 12.5–14.6 11.4–12.9 15.0–18.4 Microplac. 4.7 3.4–4.7 2.7–3.9 3.1–4.4 3.7–6.1 2.9–4.2 4.7–6.2 pt 10.9 8.0–9.7 9.4–10.6 9.8–12.0 10.4–12.9 8.7–9.0 11.4–11.5 Int. claws II, III 11.0 7.3–12.7 10.5 7.8 7.5–11.0 10.3 9.8–13.2 pt 29.3 20.3–22.2 27.8 20.8 22.7–23.4 22.2 23.8–24.5 Ext. claws II, III 11.6 7.5–14.0 10.9 8.4 7.4–11.2 10.9 10.2–13.6 pt 30.9 20.9–24.5 28.9 22.4 22.4–24.3 23.5 24.8–25.3 Ant. claw IV 12.0 10.1–17.4 7.8–11.5 7.9–10.4 9.8–13.2 7.3–13.4 10.9–14.2 pt 31.9 28.1–30.5 27.3–30.5 21.6–24.9 26.5–31.3 21.9–28.9 26.5–26.4 Post. claw IV 12.2 10.9–18.1 8.2–12.3 8.6–11.5 10.1–14.6 7.6–14.2 11.4–16.0 pt 32.5 29.0–33.2 30.6–32.6 23.5–27.6 27.0–33.0 22.8–30.6 27.7–29.7 It differs from M. coronatus in having a cuticle with very small tubercles; in lacking an anterior band of teeth and in having a posterior ring of triangular teeth in the buccal cavity less developed and without supplementary teeth; slightly wider buccal tube (Table 6); slightly longer microplacoid (Table 6) and in some characters of the eggs: they are slightly larger with larger processes (Figs. 3 E, F and 4B and Table 7).

Macrobiotus perfidus sp. n. differs from M. simulans in having a cuticle with small tubercles; in lacking an anterior band of teeth and in having a posterior ring of triangular teeth in the buccal cavity less developed; narrower buccal tube, slightly shorter macroplacoids (Table 6), claws slightly longer and more slender in shape (Figs. 3 C, D and 4C, D), and in some characters of the egg: the processes are slightly longer (Table 7), the ring of basal projections and the shell granulation more visible (Figs. 3 E, F and 4E).

It differs from M. patiens in having a cuticle with very small tubercles; in having eyes; in lacking an anterior band of teeth and in having a posterior ring of triangular teeth in the buccal cavity less developed; slightly shorter and narrower buccal tube (Table 6), stylet supports inserted on the buccal tube in a slightly more cephalic position (Table 6), shorter macroplacoids, and in some characters of the eggs: thin, terminal portion of the processes longer; shell granulation more visible (Figs. 3 E, F and 5A).

Macrobiotus perfidus differs from M. arguei in having a different cuticular ornamentation: the new species has many very small cuticular tubercles over all the body, while M. arguei has only some scattered, larger, caudal tubercles; in addition the eggs of M. perfidus have a clear visible ring of dots around the basis of the processes absent in the eggs of M. arguei.

The new species differs from M. rigidus in having a cuticle with very small tubercles, in having eye spots, in lacking an anterior band of teeth and in having a posterior ring of triangular teeth in the buccal cavity less developed and without supplementary teeth, longer microplacoid (Table 6) and in some characters of the eggs: the thin, terminal portions of the processes are flexible, the basal projections and the shell granulations more visible (Figs. 3 E, F and 5B).

Macrobiotus perfidus sp. n. differs from M. pseudocoronatus in lacking an anterior band of teeth and in having a posterior ring of triangular teeth in the buccal cavity less developed; slightly shorter macroplacoids (Table 6); slightly longer and more slender claws (Table 6; Figs. 3 C, D and 5C, D), and in characters of the egg: the processes have a thin, flexible, undivided, terminal portion almost as long as the conical basal portion while in M. pseudocoronatus the distal portion is shorter than the conical basal portion and often subdivided into two or more terminal filaments (Figs. 3 E, F and 5E).