Neelus fimbriatus

Labrum with 4,5,5,4 setae (Figs 1 A and 5 A). Anterior labral setae a 1 and a 2 thick, curved; a 2 longer than a 1 (16 and 12 µm, respectively). Seta a 1 apically with 3 small serrations and one big basal tooth, a 2 medially with 3 _ 4 strong serrations and some small externally. Medial setae (m-row) subequal (12 µm), smooth, slightly curved, the central one displaced in a small anterior lobe (Figs 1 A, 5 B). Posterior setae (p-row) smooth, subequal and slightly curved (12 µm). Maxillary palp simple, with 1 enlarged terminal seta (11 µm). Basomedian field of labium with 4 + 4 setae (Figs 1 E, 5 D), medial setae longer (16 µm) than others (10 – 11 µm); basolateral field with 1 setae and hyaline microsetae on a big alveolus, as illustrated for N. murinus by Schneider (2017). Ventral side of head with 3 + 3 postlabial setae (18 µm): 2 + 2 distal and 1 + 1 proximal thicker and barbulate (Figs 1 E, 5 C, 5 D). Mandible strong, with 5 apical teeth, and one external appendage, right mandible with an internal triangular tooth between incisive area and molar surface (Fig. 1 D). Maxilla with 6 fringed lamellae (Fig. 1 C). Thorax and abdomen (Fig. 2). Dorsal side of thorax and abdomen covered with ordinary setae, wax rods, swollen S-setae and tertiary rods. Dorso-lateral area of Th. II with: 13 + 13 ordinary setae. Precoxal area of Th. II with 2 + 2 ordinary setae, 1 + 1 τ-setae and 1 + 1 flame-shaped S-setae (s 1). Dorso-lateral area of Th. III-anterior abdomen, with 5 + 5 setae, 2 + 2 round-shaped S setae (s 3, s 3 ’), 7 + 7 wrc (wrc 1 – 7), 8 + 8 τ-setae and several tertiary rods arranged as in Fig. 2 A. Precoxal area of Th. III with 2 + 2 ordinary setae and 1 + 1 τ-setae. Abdomen with about 50 + 50 microsetae (3 – 5 µm), 1 + 1 T-shaped S-setae (s 2), 1 + 1 wrc arranged as in Fig. 2 A. Abd. V, with 4 + 4 setae (17 – 20 µm), VI with 5 + 5 setae (16 – 17 µm), 1 + 1 microsetae (µ. av) and 1 paired posterior mesoseta of anal valve (av, 4 µm) (Fig. 2 E). Male genital plate with 9 + 10 microsetae (6 – 8 µm) arranged in circle (Fig. 2 D). Female genital plate with 4 + 4 setae (9 – 10 µm) and microsetae absent (Fig. 2 E). Abd. IV sternum with 4 + 4 setae (9 – 10 µm), and 1 + 1 distal seta (9 – 10 µm). Ventrally on Abd. III and IV there are one pair of acetabular structures on each side (Fig. 6 C) similar to those of dens. Lateral part of Abd. IV sternum with 1 + 1 short, sharp and curved neosminthuroid setae (8 µm). Appendages. Ant. III and IV distinctly separated (Fig. 4 A). Length of antennae 117 µm, ratio of antenna / head = 0.6. Ratio of Ant. I: II; III; IV as 1: 2,7; 3,7; 4,3. Ant. I with 3 short dorsal setae (5 µm). Ant. II with 4 apical dorsal setae arranged in a whorl. Ant. III with 13 ordinary setae in five whorls (distribution from base to apex: 1, 1, 3, 2 and 6 setae). Antennal organ of Ant. III with 5 apical sensorial elements: Sgd, and Sgv sensilla, two microsensilla; and one ventral m’ spine-shaped (sgd: 15 µm, m: 6 µm, m’: 4 µm). Ant. IV with 10 ordinary setae; 7 sensilla (15 - 19 µm), Sx (10 µm) and Sy (15 µm); 3 long sensilla and 2 rod-like curved setae in apical (a) and subapical position (sa) and subapical organite “ Or ” with two filaments (7 µm). Setation of legs I – III (Figs. 3 A-C): scx I: 1, 1, 3; scx II: 1, 1, 1; coxae: 1, 1, 1; trochantera: 4, 3, 4; femora: 9, 10, 8 and tibiotarsi: 16, 18, 17. Some tibiotarsal setae (table 2) are on a tuberculate alveolus (Fig. 6 B). For details of shape of setae of legs see table 2. Unguis narrow and elongated, both unguis and unguiculus different long in leg I, II and III: unguis 36, 33 and 31 µm, respectively; unguiculus 16, 14 and 16 µm, respectively. Unguis bears one dorsal pseudonychia. Unguiculus untoothed without apical filament, with basal tubercule. Ventral tube with 2 + 2 distal setae and posterior lobe (Fig. 2 B). Retinaculum with 3 + 3 teeth, seta on corpus absent (Fig. 2 C). Furcula well developed (Fig. 4 B), length of manubrium, dens and mucro: 52, 105, and 66 µm, respectively. Manubrium posteriorly with 3 + 3 setae (Fig. 4 B), two distal (17 µm), one proximal (20 µm). Posterior surface of dens I with one long (20 µm) and thick seta, posterio-external part of dens II, with 3 conical spines, one central seta, and one triangular spur on each side, two internal triangular spines in the internal side, anterior surface of dens II with one apical very thin spine (setola). Mucro with both lamellae serrate, tip of mucro rounded. Sensory fields 6 + 6 s. f. placed in depressions each with secretory rod (13 – 15 µm), blunt, straight seta with basal part inserted in the cuticle and placed in upper margin of the field. The fields have following arrangement: (a) anterior and posterior field on head (s. f. I and II; 16 x 9 and 15 x 14 µm respectively) each with secretory rod and 1 internal seta (on anterior field 17 µm, on posterior one 15 µm, and 11 and 9 respectively); (b) large thoracic field (s. f. III; 35 x 20 µm) with secretory rod, 3 internal spines arranged in triangle, 2 marginal setae (13 - 15 µm); and 3 spine-like setae (26 µm); anteriorly with 3 lanceolate spines (axial shorter than lateral); (c) abdominal field VI (s. f. 6; 19 x 14 µm) with secretory rod, 1 curved internal spine, 2 marginal setae (1 internal, 1 external; 8 µm and 13 µm respectively) and T-shaped S-setae (s 2); (d) fields in the precoxal area of Th. II and III (s. f. IV, V; 18 x 14, and 20 x 19 µm, respectively) each with secretory rod, 2 curved spines. Both s. f. with 2 marginal external setae (9 - 16 µm). Both sexes known. Males are smaller than females, the only other difference between sexes is in shape and chaetotaxy of genital area, 18 microsetae in males (Fig. 6 D) vs. 10 in females.

Diagnosis. Anterior part of head with mesosetae, posterior with microsetae. Anterior part of abdomen with microsetae, posterior with some mesosetae and tertiary rods. Anterior labral setae a 1 and a 2 thick, a 1 with a big tooth and externally with 3 small serrations, a 2 medially with 3 – 4 strong external serrations. Sensory field on thorax furnished with 3 anterior lanceolate spines. Ant. I with 3 setae. Ant. II with 4 setae. Ant. III with 13 ordinary setae and five sensorial elements. Ventral side of head with one pair of proximal barbulate seta, smaller than two distal pairs. Sterna III and IV with a pair of acetabular formations each. Manubrium with 3 + 3 posterior setae. Dens proximal with only one posterior seta. Dens distal with 3 conical externo-posterior spines. Mucro with both lamellae strongly serrate and tip rounded.

Remarks. N. fimbriatus is very different to N. desantisi Najt, 1971, the only other species known in Southamerica. If differs by the absence of stouter and longer lanceolate spines around thoracic s. f. and macrosetae on posterior part of abdomen. Other differences are that N. desantisi has only 1 + 1 apical seta on ventral tube and only 2 conical spines on postero-external surface of distal dens. Being those characters unknown in other member of the genus, what makes a revision of type material needed. Photos of types were sent to us, by they are dried up and need to be remounted for proper study. N. fimbriatus clearly differs from other Neelus species by the absence lanceolate anterior spines around thoracal s. f. Moreover, it has small body size of all Neelus congeners. Original description of N. fimbriatus was based on 3 females and one juvenile (in alcohol), 2 females and one male under slides and 2 alcoholic specimens from other sample. They were from Otonga, Cotopaxi Province, Ecuador, at 1,900 m alt. July, 1998. Ours come from Guacarí, Valle del Cauca, Colombia. The only diagnostic characters mentioned by Bretfeld & Trinklein (2000) are: “ upper setae pair of ventral head-back ciliate (apomorphy), setae of labial row “ a ” thick and roughly serrate (apomorphy), posterior side of dentes with 1 + 1 basal setae (other 2 + 2) ”. In addition, they mention the “ Total length up to 0.5 mm, length of neosminthururoid setae 6 – 7 µm. Manubrium: dens: mucro = 1.7: 1.8: 1. In our specimens this ratio is 0.78: 1.6: 1. Original description the labrum is very accurate, but basoextenal field of labium was not illustrated. Fig. 9 of Bretfeld & Trinklein (2000) does not illustrate the dental spurs AJ 1 and AE 1. The ratio of antennal segments of our specimens is very similar to that found by Schneider (2017) but the number of setae Ant. II is 4 in ours (5 after Schneider) The total length of the antenna in Colombian specimens is 117 – 120 µm, shorter than those of type material (143 µm). Organite “ Or ” also with two apical filaments. Genital plate of male with only 9 + 9 setae and not 13 + 13 as in the type material. In the discussion, Schneider (2017) states that N. fimbriatus differs from Neelus murinus and Neelus koseli in antennal chaetotaxy, labral setae morphology and post-labial setae morphology. Neelus koseli and N. murinus have 6 setae on Ant. II, our specimens from Colombia have 4 setae and the redescription of Schneider illustrate 5 setae in Fig. 36 A. As the only real diagnostic character of N. fimbriatus is the barbulate seta of the post-labial area of the head, we must consider our specimens belonging to this species.

Description based on Colombian specimens (Figs 1 – 6). Body length 0.4 – 0.5 mm, habitus typical of the genus. Body color on alcohol mostly whitish, dorsally with few brown dots of pigmentation on head, thorax and abdomen. Integumentary channels observed ventrally on head (Fig. 6 A), thorax, and abdomen. Most of setae are microsetae, abdomen with about 50 pairs of tertiary rods. Measurement of most of characters are in micrometers and are presented on table 1. Those of males are average of two specimens and those of female of one specimen. Head (Fig. 1 A). Head length and width as 184 and 176 µm, respectively. Dorsal setae on head smooth and acuminate, frontal setae longer (12 – 16 µm) than those posterior (5 – 7 µm). Antero-dorsal area with 8 + 8 setae and with unpaired seta a 0. Antero-lateral area with 2 + 2 setae. Posterodorsal area with 12 setae. Postero-lateral area with 3 + 3 setae.

Material studied. Male and female mounted on slide, Colombia: Valle del Cauca, Guacarí, Santa Rosa de Tapias (coordinates N 3.81583 ° W 76.24166 °, alt. 1300 m.), 10. vi. 2017, E. P. Marín col., ex. soil. Material deposited at Facultad of Ciencias, UNAM under the numbers 22314 and 22315 (two females); 22316 and 22317 (two males), 22318 and 22319 (unknown sex).