Macrobiotus ciprianoi, Guil & Guidetti & Machordom, 2007

Guil, Noemí, Guidetti, Roberto & Machordom, Annie, 2007, Observations on the ‘‘ tenuis group’ ’ (Eutardigrada, Macrobiotidae) and description of a new Macrobiotus species, Journal of Natural History 41 (41 - 44), pp. 2741-2755 : 2743-2750

Genus Macrobiotus Thulin, 1928

Macrobiotus ciprianoi new species

( Figures 1–3 , 4A )

Material examined Holotype. Holotype 535 mm long (see Table I), sex undetermined. Deposited in the non-

insect invertebrate collection of the Natural History Museum of Madrid, Spain (Consejo Superior de Investigaciones Científicas, CSIC) (catalogue no. 23.00/2) .

Locus typicus. Xerophilous shrub landscape close to the road from Redueña to Cabanillas at 880 m a.s.l. in Madrid ( Spain; UTM 30T0449010-4519466); samples contained a mixture of Provence broom ( Cytisus purgans (L.)), leaf litter and mosses ( Isothecium myosuroides Bridel, 1827 , and Hypnum cupressiforme Hedwig, 1801 ) and were collected by N. Guil (8 November 2001). Associated tardigrade fauna: Diphascon (Diphascon) recamieri (Richters, 1901) .

Paratypes. Three specimens (see Table I) deposited in the non-insect invertebrate collection of the Natural History Museum of Madrid, Spain ( Consejo Superior de Investigaciones Científicas , CSIC) .

Further material. Samples of rock mosses ( Tortella tortuosa (Hedwig) Limpricht, 1888 ) collected in the same area by N. Guil contained 13 specimens of the new species and four eggs. Seven specimens and three eggs were identified in samples collected in spring (12 May 2001) and six specimens and one egg in samples collected in autumn (8 November 2001). Associated fauna were: Macrobiotus richtersi Murray, 1991 (adults and eggs) in spring; and Echiniscus canadensis Murray, 1910 in autumn.

Diagnosis

Smooth cuticle lacking pearls (pores); colourless; dots present in the external base of all legs; two macroplacoids, the first with a deep middle constriction, and a microplacoid; claws with secondary branch inserted in main branch at a right angle; large lunules, those of the hind legs larger and with dentate or irregular margins; eggs with cone-shaped processes, the latter with a reticular network on their surface.

Description

Description of the holotype (see measurements in Table I): body colourless, length 535.0 mm. Cuticle smooth without pearls ( Figure 1 ), but with dots at the external base of each leg (more visible on hind legs). Ocular spots present. Buccal tube length 41.2 mm, internal diameter 3.9 mm ( Figures 2A , 3A ). Mouth terminal with peribuccal lamellae not well distinguishable on LM. Buccal armature comprises fine transverse ridge systems visible in the caudal region of the buccal cavity consisting of three dorsal and three ventral transverse ridges, very slender ( Figure 2B, C ). Dorsal central crest arched with its convexity turned backwards ( Figure 2B ). Stylet supports inserted in the buccal tube at a distance corresponding to 76.2% of its length (Table I).

Pharyngeal bulb contains apophyses, two macroplacoids, and a microplacoid ( Figures 2A , 3B ). First macroplacoid bears a deep middle constriction and the second macroplacoid a posterior globular expansion, microplacoid evident close to the second macroplacoid. Slanting cuticular bars (between the apophyses and the first macroplacoid; Figure 2A ) present. Placoid row length including microplacoid 22.5 mm. First macroplacoid length 10.8 mm ( Figures 2A , 3B ), second macroplacoid 4.9 mm, and microplacoid 2.9 mm. Stylet furcae as in other Macrobiotus species.

Claws with secondary branch inserted in main branch at a right angle ( Figures 2D, E , 3C , 4A ). Very short peduncle. Short common tract with basal septum delineating a very small basal portion ( Figure 2D, E ). Fine accessory points on main claw branches. Large lunules at the base of claws of all legs. Lunules on legs I–III are smooth, those of the hind legs larger and dentate with small teeth ( Figures 2D, E , 3D ). Cuticular bars on legs absent.

In paratypes (lateral view), a long ventral lamina with a wide ventral crest is visible.

Five eggs found were ascribed to Macrobiotus ciprianoi n. sp. on the basis that the other tardigrade species in the samples do not lay free, ornamented eggs ( D. recamieri and E. canadensis ) or show different egg ornamentation ( M. richtersi ).

Eggs laid free, spherical in shape and with processes on their surface ( Figure 3E–G ). Processes are long conical or funnel-shaped with a network on their surface ( Figure 3F, G ). Egg shell surface between processes is not visible on LM. Diameter of the eggs 99.8– 103.7 mm. Process heights 11.9–19.8 mm (mean 15.6 mm) and diameters of process bases 6.9–9.9 mm (mean 8.2 mm).

Variability

Ranges and means of the morphometric characters are reported in Table I. Only two paratypes have ocular spots (in the other types, ocular spots are not visible probably due to interference by the mounting medium). In smaller paratypes, probably juveniles, the constriction in the first macroplacoid is shallower.

In M. ciprianoi n. sp. specimens collected from rock mosses, ocular spots visible in eight of the 13 fixed specimens. In smaller specimens, most likely juveniles: first macroplacoid has a shallower constriction, and first macroplacoid is larger than the second (Table I). The second macroplacoid has a widening in its posterior zone, which is not visible in smaller specimens.

Etymology

The new species was named after the late Dr Cipriano López Almeida, grandfather of the first author (N. Guil).

Taxonomic remarks

Macrobiotus ciprianoi n. sp. can be easily distinguished from the other Macrobiotus species according to a set of morphological characters: claw shape, bucco-pharyngeal apparatus characteristics, and egg morphology. The new species shares several characters with species of the ‘‘ tenuis group’’ (first macroplacoid with a deep constriction, secondary branch inserted in main branch at a right angle, and large lunules on all legs), yet differs with respect to its claw shape, presence of more rounded macroplacoids, and eggs with coneshaped processes, whose surfaces are reticulate. Macrobiotus tenuis ( Figure 4H ) and M. kozharai are the most similar species to Macrobiotus ciprianoi n. sp. Nevertheless, M. ciprianoi n. sp. differs from M. tenuis in that it has larger lunules on the claws of the hind leg, a shorter common claw tract, and in the shape of the egg processes (the eggs of M. tenuis bear truncated cone-shaped processes), and from M. kozharai in that its claws and common claw tract are shorter, and it lacks a posterior band of teeth. Other tenuis species with two macroplacoids (first with a deep constriction) similar to M. ciprianoi n. sp. are M. danilovi , M. tenuiformis , and M. voronkovi ( Tumanov 2007) . These three species have a different buccal armature, slender and larger claws of the tenuis- type, and their macroplacoids are larger and thinner compared to those of M. ciprianoi n. sp. Macrobiotus danilovi has similar shaped egg processes to the new species, although the conical processes of M. ciprianoi n. sp. are longer and more slender. Macrobiotus tenuiformis and M. voronkovi have completely different shaped egg processes to M. ciprianoi n. sp. such that their distinction is unmistakable.

If the first, deeply constricted macroplacoid is interpreted as two macroplacoids (i.e. three macroplacoids in total), then M. ciprianoi n. sp. could be mistaken for M. wilardi ( Figure 4B ). This tenuis species has three macroplacoids and eggs bearing cone-shaped processes with elongated tips. Nevertheless, Macrobiotus willardi and Macrobiotus ciprianoi n. sp. can be clearly differentiated since the new species has a fine buccal armature with no visible band of teeth (both anteriorly and posteriorly), shorter macroplacoids, a smaller microplacoid closer to the third macroplacoid, and smaller accessory points. Moreover, the secondary branch of the claws of M. ciprianoi n. sp. is almost straight and forms a right angle with the main branch ( Figures 2D, E , 3C ), whereas in M. willardi , the secondary branch is curved and the angle made with the main branch is more acute ( Figure 4B ).

Figures

Figure 1. Macrobiotus ciprianoi n. sp. Habitus of the holotype. Scale bar: 60 mm.

Figure 2. Macrobiotus ciprianoi (holotype) structures. (A) Bucco-pharyngeal apparatus in latero-ventral view; (B) buccal armature in dorsal view; (C) buccal armature in ventral view; (D) claw of the third pair of legs; (E) claw of the fourth pair of legs. Scale bars: 5 mm.

Figure 3. Macrobiotus ciprianoi n. sp. holotype. (A) Buccal tube in lateral view; (B) pharyngeal bulb contents (M1, first macroplacoid; M2, second macroplacoid; m, microplacoid); (C) claws of the third pair of legs, with secondary branch inserted in main branch at right angles indicated by an arrow; (D) lunule of the hind legs, teeth indicated by arrow; (E) image of an entire egg; (F) image showing egg processes; (G) detailed image of an egg process. (A–G) Phase contrast microscopy. Scale bars: 10 mm.

Figure 4. Claws. (A) Macrobiotus ciprianoi (paratype; third claws); (B) M. willardi (paratype; first claws); (C) M. ariekammensis (second claws); (D) M. hyperonyx (paratype; second claws); (E) M. hystricogenitus (holotype; first claws); (F) M. caelicola (paratype; third claws); (G) M. higginsi (holotype; second claws). (H) M. tenuis (second claws); (I) M. mongolicus (holotype; second claws); (J) M. bondavallii (holotype; second claws). (A, B, D–J) Phase contrast microscopy; (C) differential interference contrast microscopy. Scale bars: 10 mm.