Macroxenodes navassaensis, Duy-Jacquemin, 2009

Duy-Jacquemin, Monique Nguyen, 2009, Revision of the genera of Polyxenidae bearing pseudoarticulated gnathochilarial sensilla (Diplopoda, Polyxenida, Polyxenidae), with the description of two new species, Zoosystema 31 (4), pp. 829-848 : 839-841

Macroxenodes navassaensis n. sp.

( Fig. 7 )

TYPE MATERIAL. — Greater Antilles. Navassa Island, Clench coll., I.1930., holotype ad. ♀ and paratype ad. ♀ very near to moulting, both mounted on slides ( MNHN).

ETYMOLOGY. — The name refers to the island where the type specimens were collected.

DESCRIPTION OF FEMALE ADULTS

Measurements: body length (without caudal penicillus): 3.10 mm (holotype) and 3.50 mm (paratype). Tarsus II length of 13th leg: 143 µm (holotype) and 146 µm (paratype).

Head: Eight ocelli on each side. Vertex with one pair of posterior tufts, consisting of two rows: anterior row with 13-18, posterior row with 8 or 9 trichomes, the last in front of internal trichobothrium ( Fig. 7E ); the insertions of two last trichomes of posterior row are oriented perpendicularly to others ( Fig. 7E ). The distance between tufts is small.

Proportions of antennal articles as shown in Figure 7A ; length of article VI about twice its diameter. Antennal article VI with two groups of dorsal and postero-ventral sensilla: dorsal group composed of three thick sensilla basiconica: anterior a, intermediate i and posterior p (i being shorter than a and p), one posterior sensillum coeloconicum c and one trifid setiform sensillum s between a and i ( Fig. 7C, D ); postero-ventral group composed of two similar, thick sensilla basiconica, shorter than a and p. Antennal article VII with two subequal, thick, dorsal sensilla basiconica, one posterior sensillum coeloconicum and one trifid setiform sensillum between the two sensilla basiconica ( Fig. 7B ). Three trichobothria of equal size, with cylindrical funiculi ( Fig. 7E ).

Labrum clothed with numerous small cuspidate papillae in addition to three rows (four towards lateral side) of spherical papillae ( Fig. 7F ). 6+6 (holotype) and 8+8 ( Fig. 7F ) lamellar teeth on anterior margin. Clypeo-labrum with 13 and 14 setae along posterior margin. In holotype, lateral expansions of gnathochilarium with 14 and 15 sensilla pseudoarticulated at apex ( Fig. 7G ) and middle palpus with 21 sensilla, comprising 12 long, pseudoarticulated sensilla and 9 short sensilla not articulated at apex; gnathochilarial sensilla cannot be counted in paratype.

Trunk: trichomes are lacking; however, their orientation can be estimed thanks to their insertion. Except on collum and tergites IX and X, trichomes arranged in two lateral tufts with 16-33 trichomes connected by three trichomic rows: anterior row with 19-40 trichomes directed towards head; middle row with 7-21 trichomes and a sinuous posterior row with 42-74 trichomes directed towards telson; anterior and posterior rows uninterrupted. On some tergites the anterior and middle rows are slightly sinuous. Total number of tergal trichomes as follows: I (collum), 103 (holotype) or 123; II to VIII, 109 or 178; IX and X, 85 or 76. Lateral protuberance of tergite I with 5 (holotype) or 6 trichomes in a row.

Legs: all articles of legs bearing sensory setae, first tarsus excepted. Setae on coxa, trochanter and prefemur with an oval base, provided with an apical process ( Fig. 7J ). Chaetotaxy as follows: coxae II to XII with 2 setae (1 seta in six cases, 3 setae in one case); trochanters with 1 seta; prefemora leg I to XIII with 1 seta and 1 or 2 small, trifid setae ( Fig. 7H, I ); almost all femora and tibiae with same small seta as prefemur. Second tarsus with a small seta as shown in Figure 7K . Telotarsus bearing an anterior process with a spinous projection longer than claw, two subequal latero-anterior and posterior spiniform processes; posterior lamellar process thickened and basally pleated ( Fig. 7L ).

Four setae above the anal valve in paratype.

Telson: dorsal face of telson with 13-16 barbate trichomes a; one trichome b inner to group of 19 trichomes c observed in paratype. Ventral face with a subrectilinear row of 14+14 barbate trichomes v in holotype and 13+ 15 in paratype ( Fig. 6E ), located on the edge of the insertions of fallen hooked trichomes.

AFFINITIES

This species is close to Macroxenodes amazonicus Ishii, Nguyen Duy-Jacquemin & Condé, 1999 . However, there are significant differences between them. The postero-ventral group of antennal sensilla of article VI has only two sensilla, as opposed to 4-7 in M. amazonicus . Th ere are three anterior rows of spherical papillae on the labrum, whereas in M. amazonicus there are only two. The new species has 15 sensilla at most on the lateral palp expansion, compared to 21-23 in M. amazonicus . The median interruption of the anterior trichomic row of the tergites of M. amazonicus is not present in the new species.

Figures

FIG. 7. — Macroxenodes navassaensis n. sp.: A, right antenna of paratype; B, C, sensilla on right antennal articles VII and VI of holotype; D, sensilla on left antennal article VI of paratype, the new sensilla shown with dotted lines will appear after exuviation; E, left part of head of holotype with insertions of dorsal trichomes; F, labrum of paratype, only part of cuticular setae shown; G, right palpus of gnathochilarium of holotype; H-L, holotype; H, I, small setae of prefemora of right legs III and VII; J, coxal seta of right leg I; K, seta of tarsus II of right leg VI; L, telotarsus of right leg III. Abbreviations: a, anterior sensillum basiconicum; c, sensillum coeloconicum; i, intermediate sensillum basiconicum; p, posterior sensillum basiconicum; s, setiform sensillum. Scale bars: A, E, 50 μm; B-D, F-L, 25 μm.

FIG. 6. — A-D, Macroxenodes meinerti (Silvestri, 1898); A, B, distal parts of barbate and hooked trichomes of caudal penicillus of male; C, ventral face of telson of male, dorsal trichomes shown with dotted lines; D, dorsal face of telson of male; E, M. navassaensis n. sp., caudal view of female paratype. All the biggest insertions belonging to barbate trichomes are shown; only part of insertions of hooked trichomes shown; dorsal trichomes a with dotted lines. Abbreviations: a1-a10, insertions of barbate trichomes a; b, insertion of trichome b; c, group of trichomes c; v1-vX, insertions of ventral barbate trichomes on edge of penicillus. Scale bars: A, B, D, 25μm; C, E, 50 μm.