Macrobiotus siamensis, Tumanov, Denis V., 2006

Tumanov, Denis V., 2006, Macrobiotus siamensis sp. n. (Eutardigrada, Macrobiotidae) from Thailand (Asia), Zootaxa 1202, pp. 53-59 : 54-58

Macrobiotus siamensis sp. n.

( Figs. 1–14 , Table 1 )

= Macrobiotus sp. gr. furciger ( Tumanov 2005)

Type material

Holotype: Slide number 201(49) (sex indet.). Collected by Dr. V. R. Alekseev (Zoological Institute of the Russian Academy of Sciences, St. Petersburg), 0 1.02.2003, Thailand. Paratypes: Slides number 201(37, 46, 50, 51) from the same locality. Holotype and paratypes are preserved at the Zoological Institute of the Russian Academy of Sciences, St.Petersburg, Russia.

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. Nine adult specimens and three eggs (one with developed embryo) were found.

Description

Body length of adult animals 292.6–412.3 m ( Figs. 1 , 8 ). Body white (colourless). Without eye spots. Cuticle smooth without pores and granulation. Bucco­pharyngeal apparatus of Macrobiotus type ( Figs. 2 , 9 ) (for all dimensions see Table 1 ). Buccal cavity with ten peribuccal lamellae, very poorly developed anterior band of teeth (scarcely visible even in the largest specimens), 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 is almost broken into several granules ( Figs. 3, 4 , 10, 11 ). Several separate rounded teeth situated ventrally between posterior crown of teeth and transverse ridges. Buccal tube with typical strengthening bar. Pharyngeal bulb with apophyses, three macroplacoids and a microplacoid. Third macroplacoid with a distinct preterminal constriction. Claws of hufelandi ­ type ( Figs. 5, 6 , 12 ) with minute stalk, distinct distal part of the basal portion and short common tract. Primary and secondary branches diverge below 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 with undulating margins on fourth pairs of legs. Bar­like cuticular thickenings are present below claw bases of first three pairs of legs ( Fig. 5 ).

Eggs spherical, white, ornamented and laid freely ( Figs. 7 , 13, 14 ). Chorion with conical processes (22 in the optical section at the light microscope), with bifurcated apices (sometimes one of the branches is also bifurcated). Place of bifurcation situated near the process apex, branches are short and with pointed apices. Surface of processes smooth, rarely with poorly developed light areas (pores?). Process bases surrounded with a ring of small dots. Egg surface between processes with irregularly distributed broken ridges, forming poorly developed reticulation. Egg diameter (without processes): 70.3– m; height of processes: 10.7–11.8 m, their basal diameter: 7.4–10.0 m.

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: 27.4 m, lunules on claws of the fourth pair of legs: 4.4 x 2.1 m

Remarks

Macrobiotus siamensis sp. n. belongs to the furciger group and is most similar to Macrobiotus sicheli Binda, Pilato and Lisi, 2005 in having short apical branches of egg processes. Macrobiotus siamensis sp. n. differs from M. sicheli in absence of eyes, smooth cuticle, stylet supports inserted on the buccal tube in a more cephalic position (pt values: 77.1–78.8 in M. siamensis sp. n. and 79.3–80.0 in M. sicheli ), thinner buccal tube (pt values: 13.3–16.2 in M. siamensis sp. n. and 16.4–18.3 in M. sicheli ), eggs with longer processes (10.7–11.8 m in M. siamensis sp. n. and 6.5–7.8 m in M. sicheli ) and less developed sculpture between them.

Macrobiotus siamensis sp. n. differs from Macrobiotus pilatoi Binda and Rebecci, 1992 in having thinner buccal tube (pt value 13.3–16.2 in M. siamensis sp. n. and 22.8–25.4 in M. pilatoi ), shorter claws (pt value for the claws of the III pair of legs 19.4–23.7 in M. siamensis sp. n. and 29.5–31.5 in M. pilatoi ) and egg chorion with smaller processes (10.7–11.8 m in M. siamensis sp. n. and 15 m in M. pilatoi ) and with different sculpture between them.

Macrobiotus siamensis sp. n. differs from Macrobiotus furciger in absence of eyes, slightly wider buccal tube (pt value 13.3–16.2 in M. siamensis sp. n. and 12.7–13.6 in M. furciger ), shorter claws and smaller eggs with short branches of processes and with different sculpture between them.

Macrobiotus siamensis sp. n. differs from Macrobiotus aradasi Binda, Pilato and Lisi, 2005 in absence of eyes, wider buccal tube (pt value 13.3–16.2 in M. siamensis sp. n. and 11.7–11.8 in M. aradasi ), stylet supports inserted on the buccal tube in a more caudal position (pt values: 77.1–78.8 in M. siamensis sp. n. and 72.0– 72.8 in M. aradasi ) and smaller eggs with shorter branches of processes and with different sculpture between them.

Macrobiotus siamensis sp. n. differs from Macrobiotus divergens Binda, Pilato and Lisi, 2005 in having stylet supports inserted on the buccal tube in a more caudal position (pt values: 77.1–78.8 in M. siamensis sp. n. and 75.5–76.2 in M. divergens ), eggs with more dense distribution of processes, short branches of processes and different sculpture between them.

Macrobiotus siamensis sp. n. differs from Macrobiotus orcadensis Murray, 1907 (population from Norway) in absence of eyes, the terminal points of the egg processes are acuminate while in M. orcadensis they are obtuse, egg processes with a ring of basal dots more evident (Pilato, pers. comm.).

Figures

FIGURES 1 – 7. Macrobiotus siamensis sp. n. 1. habitus, 2. bucco­pharyngeal apparatus, dorsal, 3. buccal armature, dorsal, 4. buccal armature, ventral, 5. claws of the I pair of legs, 6. claws of the IV pair of legs, 7. part of the egg surface (2 – 4. holotype, 1, 5, 6. paratype).

FIGURES 8 – 14. Macrobiotus siamensis sp. n. 8. habitus, 9. bucco­pharyngeal apparatus, 10. buccal armature, dorsal, 11. buccal armature, ventral, 12. claws of the I pair of legs, 13. general appearance of the egg, 14. part of the egg surface (phase contrast; 10. holotype, 8, 9, 11, 12. paratypes).

Tables

TABLE 1. Summary of morphometric data for Macrobiotus siamensis sp. n. (n = 9).

Character	Holotype	Smallest specimen	Largest specimen	Mean (Range)
body length (m)	412.3	292.6	412.3	351.6 (292.6–412.3)
buccal tube length (m)	44.4	41.8	44.4	42.4 (38.9–48.1)
Ss (m)	34.8	32.9	34.8	33 (30–37.4)
pt Ss (%)	78.3	78.8	78.3	77.9 (77.1–78.8)
outer buccal tube width (m)	6.4	6.7	6.4	6.4 (5.2–7.4)
pt of outer buccal tube width (%)	14.5	15.9	14.5	15.1 (13.3–16.2)
Placoid row length (m)	23.7	21.5	23.7	21.1 (18.1–25.9)
pt of placoid row length (%)	53.3	51.3	53.3	49.6 (44.9–53.8)
Macroplacoid row length (m)	18.5	16.3	18.5	16.2 (13.7–20)
pt of macroplacoid row length (%)	41.7	38.9	41.7	38.2 (34.9–41.7)
1st macroplacoid length (m)	4.8	4.4	4.8	4.6 (3.7–6.4)
pt of 1st macroplacoid length (%)	10.8	10.6	10.8	10.8 (8.5–13.2)
2nd macroplacoid length (m)	4.2	3.7	4.2	3.8 (3.2–4.4)
pt of 2nd macroplacoid length (%)	9.5	8.8	9.5	9 (7.6–9.6)
3rd macroplacoid length (m)	5.7	5.0	5.7	4.9 (3.8–6.7)
pt of 3rd macroplacoid length (%)	12.8	12.0	12.8	11.4 (9.5–13.8)
Microplacoid length (m)	4.4	4.1	4.4	4 (3.3–5)
pt of microplacoid length (%)	10.0	9.7	10.0	9.3 (7.7–11)
External claw length, leg I (m)	8.9	8.1	8.9	8.5 (7.8–9.6)
pt of external claw length, leg I (%)	20.0	19.5	20.0	20 (18.7–21.1)
External claw length, leg III (m)	9.6	8.9	9.6	9.3 (8.5–11.1)
pt of external claw length, leg III (%)	21.7	21.2	21.7	21.8 (19.4–23.7)
External claw length, leg IV (m)	11.8	11.1	11.8	11.1 (9.6–11.8)
pt of external claw length, leg IV (%)	26.7	26.5	26.7	26.4 (24.2–28.4)