Americanura najtae, Arango & Villagomez & Palacios-Vargas, 2017

Arango, Ángela, Villagomez, Fernando & Palacios-Vargas, José G., 2017, On the genus Americanura Cassagnau, 1983 (Collembola: Neanuridae: Sensillanurini) with description of a new Mexican species and complement to the description of A. mexicana Cassagnau, 1983, Zoosystema 39 (1), pp. 49-54 : 52-54

Americanura najtae n. sp.

( Figs 1 , 2 ; Table 2)

TYPE MATERIAL. — Holotype adult ♀ (catalog number 22298) and five paratypes on slides; one skin from adult male prepared on slides after barcode extraction (voucher catalog number 22303), two ♂ preadults (catalog numbers 22301, 22302) and two juveniles (catalog numbers 22299, 22300) all with the same collecting data as the holotype, all of them deposited in the Collección de Collembola de México, belong- ing to the laboratory of Ecology and Systematics of Microarthropods ( LESM); UNAM. One paratype preadult ♂ (catalog number 22301) will be deposited at the Laboratory of Entomology of the MNHN.

TYPE LOCALITY. — México, Chiapas: Finca Santa Fe (La Esperanza) 15°18’33.21”N, 92°26’7.93”O, 843 m altitude. Former vegetation of this Chiapas mountains was oak forest, now there are coffee plantations. Ex leaf litter, 14. III.2004, J. G. Palacios-Vargas coll.

DIAGNOSIS. — Americanura najtae n. sp. is characterized by the total fusion of the tubercle antennofrontal and the highest setal reduction in such tubercle in the genus. This new species is similar to A. castillorum Palacios-Vargas & Najt, 1986 in having two setae in the dorsoexternal tubercule of Th. I, but differs by having only one seta in the cephalic dorsoexternal tubercle (two in A. castillorum); and two ocular setae (three in A. castillorum) and lacking any tooth on ungues; it has only one seta on the dorsointernal tubercle of abdominal segment V. A. najtae n. sp. is easily distinguished from all the species in the genus because it has only one setae A and one seta B in the middle of antennofrontal tubercle which is very reduced.

VARIATION. — Few variations were found in the chaetotaxy of this species. The cephalic De tubercle can have one additional microseta. The cephalic DL + L + Sc of one specimen has nine setae instead of 10 and the most frequent variation found was the shape of the setae. On Abd. IV there was observed a variation of the shape of the setae on the tubercle Dl + L.

ETYMOLOGY. — The new species is named after Dr Judith Najt for her contributions to the Neotropical Collembola.

DESCRIPTION

Body

Lenght (n = 4) 1.8 mm. Color white. Granulations strong, about the size of one eye. Tubercles well developed except antenno-frontal and cephalic dorsointernal, which are very slightly defined. Five kinds of body setae, barbulate macrosetae, barbulate microsetae, barbulate mesosetae, microsetae and macrosetae with few barbulations, besides the sensorial setae ( Fig. 1A, C ).

Antenna

Ant. I with seven setae, three dorsal barbulate macrosetae, Ant. II with 11 setae, 3-4 dorsal BM Ant. III sensorial organ with two rod-shaped sensilla separated in the lateral apical part of Ant. III by a small cuticular fold, and with two guard sensilla. S.g. v. almost straight, one microsensillum ventroexternal relatively long. Ventral chaetotaxy of Ant. III similar to that described for Endonora by Smolis (2008) except that basal setae of Vc group which are ¾ the length of those of distal part. Ant. IV as typical for the genus ( Fig. 1B ) with sensilla S7 hypertrofied, 12 setae, subapical organ and ordinary setae “I”; ventrally as that described by Smolis (2008), with three “file” setae at the “ca” group instead of two.

Head

Eyes 2 + 2 with dark pigment. Mandibles with three teeth ( Fig. 1A ), maxillae styliform ( Fig. 2B ) with apex hooked. Head with ocular tubercle isolate, Di, De and DL + L + So tubercles well developed. Head cheatotaxy as in Fig. 1A . Labrum with four prelabral setae and two pairs of setae ( Fig. 2C ). Labium with the normal setae for the tribe and three pairs of postlabial setae ( Fig. 2D ). Tibiotarsi I, II and III without tenent hairs, with 18, 18, and 17 setae respectively ( Fig. 2E ). Thoracic and abdominal chaetotaxy in Figure 1A and C . Total chaetotaxy as in Table 2.

Abdomen

Ventral tube with 4+4 setae, the two distal pairs of setae slightly longer than anterior pairs. Furcal vestige, with four setae, and group Ve with only four setae. Ventrally on Abd. V, Vei and Vec identical to Endonura , and Vel and VI similar but with one very long setae, about three times the length of other setae of the group. Genital plate of female with three pairs of pregenital setae, 17 circumgenital setae and two eugenital setae ( Fig. 1F ). Each lateral anal valve with 11 setae and two microsetae. Posterior anal valve with three microsetae.

Figures

FIG. 1. — Americanura najtae n. sp.: A, dorsal chaetotaxy of head and Th. I-III; B, dorso-lateral chaetotaxy Ant.I-IV;C, Abd.I-VI, dorsal chaetotaxy.Abbreviations: see Material and methods. Scale bars: A, C, 150 µm; B, 50 µm.

FIG. 2. — Americanura najtae n. sp.: A, mandible; B, maxilla;C, labrum;D, ventral view of the head and labium; E, tibiotarsus III; F, female genital plate.Abbreviations: see Material and methods. Scale bars: A-C, 20 µm; D-F, 50 µm.