Macrobiotus ocotensis, Pilato, Giovanni, 2006

Pilato, Giovanni, 2006, Remarks on the Macrobiotus polyopus group, with the description of two new species (Eutardigrada, Macrobiotidae), Zootaxa 1298, pp. 37-47 : 43-46

Macrobiotus ocotensis sp. n. ( Fig. 3 A–D)

Type locality. Southern Mexico, Chiapas, Selva El Ocote.

Material examined. Holotype (slide no. 5095), 2 paratypes and 1 egg.

Species diagnosis. Cuticle smooth with many circular and elliptical pores, eye spots present; ventral lamina twice as long as the stylet sheaths; buccal armature with three dorsal and three ventral thin and short transversal ridges; pharyngeal bulb with apophyses, two macroplacoids and a small, faint, sometimes invisible, microplacoid; claws of hufelandi type, short, with a common tract slightly shorter than the secondary branch; accessory points present; smooth lunules present; eggs freely laid; egg processes (25 around the circumference, about 100 in the hemisphere) smooth, with a basal portion in shape of a hexagonal prism and a breast­shaped distal portion with an apical, sharpened, point. Egg shell with a reticular design with hexagonal meshes.

Description of the holotype. Body length 246 µm, colourless, eye spot present, cuticle smooth with many circular and elliptical pores present on both dorsal and ventral body surface and on the legs; circular pores diameter up 1 µm, elliptical pores dimensions up to 1.8 µm x 1.2 µm; small dots present on the legs. Mouth terminal with ten small peribuccal lamellae ( Fig. 3 A), buccal armature very simple and difficult to see due to the small dimensions of the buccal cavity; a system of three dorsal and three ventral very thin transversal ridges is visible (the medio­ventral ridge is very short); perhaps a band of very small teeth is also present, but this statement needs to be confirmed. Buccal tube 28.2 µm long and 2.8 µm wide (pt = 9.9); ventral lamina twice as long as the stylet sheaths, its length (15.8 µm) is 56.2 % of the buccal tube length. Stylet supports inserted on the buccal tube wall at 69.8 % of its length (pt = 69.8).

Pharyngeal bulb ( Fig. 3 A) with apophyses, two rod­shaped macroplacoids and a very small or almost invisible microplacoid. Entire placoid row 11.2 µm long (pt = 39.7), macroplacoid row 9.7 µm (pt = 34.4). First macroplacoid, with a central narrowing, 5.8 µm long (pt = 20.6), second 3.7 µm (pt = 13.1), microplacoid 1.2 µm (pt = 4.3); the microplacoid is faint, i.e. it tends to become less visible in the mounted material.

Claws, of hufelandi type, short but not weak ( Fig. 3 B) with a common tract slightly shorter than the secondary branch ( Fig. 3 A); internal and external claws of the second and third pairs of legs 8.1 µm (pt = 28.7) and 8.4 µm (pt = 29.8) long respectively; anterior and posterior claws of the hind legs 8.9 µm (pt = 31.6) and 9.2 µm (pt = 32.6) long respectively. Main branches with accessory point well developed; small, complete, smooth lunules present. Cuticular thickenings near the lunules on the first three pairs of legs seem to be absent, but this character needs to be confirmed.

The paratypes are similar to the holotype in both qualitative and metric characters ( Table 3 ).

Eggs, freely laid, spherical, with small processes ( Fig. 3 C, D); the diameter is 63 µm excluding the processes, 79.9 µm including these structures; the processes (25 around the circumference, about 100 in the hemisphere) are smooth and have a basal portion in the shape of a hexagonal prism and a breast­shaped distal portion with an apical, sharpened, point ( Fig. 3 D); they are 4.7–6.0 µm high, the basal diameter is 4.9–6.0 µm. The base of the processes are joined to one another by thin stripes forming a reticular design with hexagonal meshes ( Fig. 3 D). This design excluded, the egg shell is smooth.

Etymology. The name ocotensis refers to the type locality.

Remarks. M. ocotensis sp. n. differs from M. polyopus in the following features: longer ventral lamina; microplacoid faint but present; claws not particularly weak; accessory points well developed; eggs larger ( Table 2) with more numerous and smaller processes (25 around the circumference and about 100 in the hemisphere in M. ocotensis sp. n., 18 and 39 respectively in M. polyopus ).

M. ocotensis sp n. differs from M. insularis sp. n. in the following features: dots on legs present; shorter and narrower buccal tube ( Table 1 ) (due to the different length of the buccal tube, some structures, e.g., the placoids and the claws, shorter or almost of the same length as in M. insularis , have similar (the placoids) or higher (the claws) values of the pt index); claws with a common tract slightly shorter than the secondary branch ( Figs 3 A, 2A, B); and in some characters of the eggs ( Figs 3 C, D; 2C–D; Table 2): smaller dimensions; processes different in shape; smaller and more numerous egg processes (25 around the circumference and about 100 in the hemisphere in M. ocotensis sp. n., 13–14 and 35 respectively in M. insularis sp. n.); egg shell without dots.

M. ocotensis sp. n. differs from M. mandalaae in the following characters: claws with a common tract slightly shorter than the secondary branch ( Figs 3 A, 1B, C); and in some characters of the eggs ( Figs 3 C, D and 1D–F; Table 2): larger dimensions; processes more numerous (about 100 in the hemisphere in M. ocotensis sp. n., 70–75 in M. mandalaae ) and different in shape (they have a distal breast­shaped portion without annulations, while in M. mandalaae the distal portion is conical, sometimes forked, and with evident annulations).

Figures

FIGURE 3. Macrobiotus ocotensis sp. n. A, bucco­pharyngeal apparatus on lateral view (paratype). B, claws of the second and third pairs of legs (holotype). C, egg. D, detail of the egg. Scale bar = 10 µm.

Tables

TABLE 3. Dimensions (in μm) and pt (in %) of some structures of the smallest and of the largest measured specimens of M. ocotensis sp. n.

	Smallest specimen	Largest specimen
	dimensions pt	dimensions pt
Body length	203	261
Buccal tube length	25.5	29.3
Buccal tube width	2.1 8.2	3.1 10.6
Stylet supports	72.8	72.4
Ventral lamina	15.4 60.4	17.7 60.4
Placoid row	10.1 39.6	11.5 39.2
Macroplacoid row	9.0 35.3	10.7 36.5
First macroplacoid	5.2 20.4	5.5 18.8
Second macroplacoid	3.6 14.1	4.4 15.0
Microplacoid	1.4 5.5	1.2 4.1
External claws II, III	6.4 25.1	7.7 26.3
Internal claws II,III	??	7.4 25.3
Anterior claws IV	??	7.9 27.0
Posterior claws IV	??	8.5 29.0