Macrobiotus alekseevi, Tumanov, Denis V., 2005

Tumanov, Denis V., 2005, Notes on the Tardigrada of Thailand, with a description of Macrobiotus alekseevi sp. nov. (Eutardigrada, Macrobiotidae), Zootaxa 999, pp. 1-16 : 2-7

Macrobiotus alekseevi sp. nov. ( Figs. 1–21 , Table 1 )

Type Material: Holotype: Sex indet., slide number 201(2). Collected by Dr. V. R. Alekseev (Zoological Institute of the Russian Academy of Sciences, St.­Petersburg) 0 1.02.2003, Thailand. Paratypes, slide’s numbers 201(1, 3–7, 10, 12–14, 17–20, 22–25) from the same locality. Holotype and paratypes are preserved at the Zoological Institute of the Russian Academy of Sciences, St. Petersburg, Russia. One paratype (slide number 201(27)) preserved in the collection of Binda and Pilato (Department of Animal Biology, University of Catania, Italy).

Type locality. Thailand, Nam­Nao National Park (Phetchabun province and Chaiyaphum province), near the park's headquarters, fallen bamboo leaves in a pit near a little stream. Ninety­eight adult and juveniles (8 in simplex stage) and 39 eggs (8 with developed embryos) were found.

Etymology. This species is dedicated to Dr. V. R. Alekseev, who kindly collected the material for me in Thailand.

Description. Body length of adult animals 365.8–551.9 m ( Fig. 1 ). Body normally white, only specimens in the simplex stage are pinkish. Without eye spots. Cuticle smooth without pores, with fine granulation on hind legs. Bucco­pharyngeal apparatus of Macrobiotus type ( Figs. 2 , 8 ) (for all dimensions see Table 1 ). Buccal cavity with ten peribuccal lamellae, wide anterior band of fine teeth, a posterior crown of triangular teeth and a system of three dorsal and three ventral transverse ridges; latero­ventral ridges usually with denticulate anterior margin, medio­ventral ridge always subdivided into 3–5 triangular or rounded teeth ( Figs. 3, 4 , 9, 10 ). Buccal tube wide with typical strengthening bar. Pharyngeal bulb with apophyses, three macroplacoids and a small microplacoid well separated from the third macroplacoid. A thin cuticular connection between the third macroplacoid and the microplacoid is present. Third macroplacoid with a distinct pre­terminal constriction. Claws of hufelandi ­ type ( Figs. 5, 6 , 11, 12 ) with minute stalk, poorly marked distal part of the basal portion and long common tract. Primary and secondary branches diverge above half of claw height, main branches with well developed accessory points. Claws of fourth pair of legs longer than claws of first three pairs of legs. All claws with lunules, which are slightly larger and provided with small teeth on the fourth pair of legs. Two small and indistinct cuticular thickenings are present below claw bases of first three pairs of legs. In the largest specimens hind legs with zone of thickened cuticle near their bases ( Figs. 1 , 21 ).

Character Holotype Smallest Largest Mean (Range) Standard

specimen specimen error

body length (m) 538.7 365.8 552.0 452.3 (365.8–552.0) 11.83 Ss = distance from cephalic end of buccal tube to insertion point of stylet supports.

Supplementary measurements for holotype: length of strengthening bar on buccal tube: above 31.1 m, lunulae on claws of the fourth pair of legs: 2.2 x 6.7 m

Eggs spherical, white, ornamented and laid freely ( Figs. 7 , 13–16 ). Chorion with trunco­conical processes and areolated surface. Chorion processes with cap­like vesicular structures on their apices and transverse annulation in their apical parts. Surface of processes with dense reticulation, the meshes are isodiametric near the process base and become longitudinally elongated in the central part of the process. Meshes with slightly sinuous margins. Ten–twelve areolae surround the base of each process. Ridges delimiting the areolae with indistinct reticulation, better developed near the process bases. Areolae with poorly developed reticulate sculpture. Proportions of the chorion processes are very variable, along with the typically looking eggs two kinds of abnormal eggs were found – with extremely shortened (2 eggs) and strongly elongated (3 eggs) processes ( Figs. 17– 20 ). Ridges delimiting the areolae on the egg surface are also very variable in width. Diameter of eggs (without processes): 59.2–82.8 m; height of processes (10–12 in the optical section): 11.8–21.8 m, their basal diameter: 13.3–22.9 m (including abnormal eggs).

Remarks. Macrobiotus alekseevi sp. nov. belongs to the richtersi group. It differs from all species of this group by having egg processes with vesicular cap­like structures. It also differs from other species of this group in following features:

From Macrobiotus corgatensis Pilato, Binda & Lisi, 2002 in absence of eyes, longer (related to the buccal tube length) claws of the hind legs (pt value 28.0– 34.3 in M. alekseevi and 25.7 in M. corgatensis holotype), smaller eggs, shorter egg processes, less sculptured areolae, less developed reticulation on ridges, delimiting the areolae ( Pilato et al. 2002).

From Macrobiotus danielae Pilato, Binda, Napolitano & Moncada, 2001 in absence of eyes, egg processes with smaller basal diameter, with transverse annulation on the process apices, sculptured areolae (Pilato et al. 2001).

From Macrobiotus gerlachae Pilato, Binda & Lisi, 2004 in egg processes of different shape with transverse annulation ( Pilato et al. 2004b).

From Macrobiotus lorenae Biserov, 1996 in shorter egg processes of different shape and sculptured areolae ( Biserov 1996).

From Macrobiotus peteri Pilato, Claxton & Binda, 1989 in longer (related to the buccal tube length) claws of the hind legs (pt value 28.0– 34.3 in M. alekseevi and 23.0–26.0 in M. peteri ), larger egg processes of different shape, sculptured areolae ( Pilato et al. 1989a).

From Macrobiotus . priviterae Binda, Pilato, Moncada & Napolitano, 2001 in absent eyes, relatively thinner buccal tube, smaller eggs, egg processes of different shape, lesser density of the egg processes reticulation, more numerous and less sculptured areolae (Binda et al. 2001).

From Macrobiotus . richtersi Murray, 1911 in egg processes of different shape with subapical annulation and sculptured areolae.

From Macrobiotus savai Binda & Pilato, 2001 in absence of eyes, slightly longer (related to the buccal tube length) claws of the hind legs (pt value 28.0– 34.3 in M. alekseevi and 24.7–27.9 in M. savai ), different reticulation pattern of egg processes, presence of subapical annulation on processes, sculptured areolae (Binda & Pilato 2001).

From Macrobiotus vanescens Pilato, Binda & Catanzaro, 1991 in stylet supports inserted on the buccal tube in a more caudal position (pt values: 78.1–81.0 in M. alekseevi and 77.3–79.4 in M. vanescens ), smaller eggs with lesser basal diameter of processes ( Pilato et al. 1991, 2001).

Figures

FIGURES 1 – 7. Macrobiotus alekseevi sp. nov. 1 — habitus (arrows points to the cuticular thickenings), 2 — bucco­pharyngeal apparatus, dorsal, 3 — buccal armature, dorsal, 4 — buccal armature, ventral, 5 — claws of the III pair of legs, 6 — claws of the IV pair of legs, 7 — part of the egg surface (5, 6 — holotype; 1 – 4 — paratypes).

FIGURES 8 – 16. Macrobiotus alekseevi sp. nov. 8 — bucco­pharyngeal apparatus, ventral, 9 — buccal armature, dorsal, 10 — buccal armature, ventral, 11 — claws of the III pair of legs, 12 — claw of the IV pair of legs, 13, 14 — general appearance of the typical egg, 15 — part of the egg surface, 16 — typical egg processes (phase contrast; 12 — holotype, 8 – 11 — paratypes).

FIGURES 17 – 23. Macrobiotus alekseevi sp. nov. 17, 18 — general appearance of abnormal eggs, 19, 20 — processes of abnormal eggs, 21 — ventral side of a paratype hind leg with zone of thickened cuticle (arrow). Minibiotus sp. 22 — cephalic part of the body, ventral, 23 — claws of the IV pair of legs (phase contrast).

Tables

TABLE 1. Summary of morphometric data for Macrobiotus alekseevi sp. nov. (n = 26).

buccal tube length (m)	53.3	41.4	54.8	47.1 (39.2–55.5)	0.90
Ss (m)	42.2	32.6	43.7	37.3 (31.1–44)	0.71
pt Ss (%)	79.2	78.6	79.7	79.3 (78.1–81)	0.13
outer buccal tube width (m)	10.4	6.9	11.1	8.4 (6.3–11.5)	0.28
pt of outer buccal tube width (%)	19.4	16.6	20.3	17.9 (15–20.7)	0.31
Placoid row length (m)	38.5	26.6	42.9	30.9 (22.9–42.9)	0.94
pt of placoid row length (%) Macroplacoid row length (m)	72.2 30.3	64.3 20.4	78.4 33.3	65.3 (58.5–78.4) 24.1 (18.5–33.3)	0.87 0.72
pt of macroplacoid row length (%)	56.9	49.1	60.8	51.1 (45.5–60.8)	0.68
1st macroplacoid length (m)	8.9	6.3	11.1	7.5 (5.2–11.1)	0.23
pt of 1st macroplacoid length (%)	16.7	15.2	20.3	16 (13.2–20.3)	0.26
2nd macroplacoid length (m)	6.7	4.4	7.0	5.5 (3.9–7.4)	0.19
pt of 2nd macroplacoid length (%)	12.5	10.7	12.8	11.7 (9.8–14.5)	0.24
3rd macroplacoid length (m)	10.4	7.4	11.1	8.2 (5.9–11.1)	0.26
pt of 3rd macroplacoid length (%)	19.4	17.9	20.3	17.4 (14.9–20.3)	0.30
Microplacoid length (m)	2.2	2.2	2.2	2.3 (1.9–3)	0.06
pt of microplacoid length (%)	4.2	5.4	4.1	4.8 (4–6.2)	0.11
External claw height, leg I (m)	13.3	9.6	13.3	11.7 (9.6–13.7)	0.22
pt of external claw height, leg I (%)	25.0	23.2	24.3	24.8 (22.7–28.7)	0.30
External claw height, leg III (m)	14.1	10.7	14.1	12.2 (10.7–14.1)	0.21
pt of external claw height, leg III (%)	26.4	25.9	25.7	26.1 (22.7–30.2)	0.34
External claw height, leg IV (m)	15.5	11.8	15.9	14.3 (11.8–16.3)	0.26
pt of external claw height, leg IV (%)	29.2	28.6	29.1	30.4 (28–34.3)	0.31