Urobenus guianomeridionalis Bartz & Decaëns, n. sp.

(Fig. 15)

urn:lsid:zoobank.org:act: 5582A14C-A215-41DD-9F1B-10D090EEB1B9

TYPE MATERIAL. — Holotype. French Guiana • Adult; Tumuc-Humac, Mitaraka Massif, slope forest on DIADEMA project C trail, in decaying trunk; 2°14’5”N, 54°26’42”W; 377 m a.s.l.; III.2015; T. Decaëns, E. Lapied leg.; BOLD Sample ID: EW-MI15-0078; MNHN.

Paratypes. French Guiana • 2 adult specimens; Tumuc-Humac, Mitaraka Massif, hilltop forest on Borne 1 Inselberg; 2°12’35”N, 54°26’12”W; 600 m a.s.l.; III.2015; T. Decaëns, E. Lapied leg.; BOLD Sample ID: EW-MI15-0218, EW-MI15-0219; CEFE • 1 adult specimen; Tumuc-Humac, Mitaraka Massif, hilltop forest on Sommet en Cloche Inselberg; 2°13’42”N, 54°28’2”W; 638 m a.s.l.; III.2015; T. Decaëns, E. Lapied leg.; BOLD Sample ID: EW-MI15-0106; CEFE • 1 adult specimen; Tumuc-Humac, Mitaraka Massif, plateau forest on DIADEMA project A trail; 2°14’38”N, 54°27’32”W; 371 m a.s.l.; III.2015; T. Decaëns, E. Lapied leg.; BOLD Sample ID: EW-MI15-0084; MNHN • 1 adult specimen; Tumuc-Humac, Mitaraka Massif, plateau forest on DIADEMA project D trail; 2°12’57”N, 54°27’25”W; 381 m a.s.l.; III.2015; T. Decaëns, E. Lapied leg.; BOLD Sample ID: EW-MI15-0019; MNHN • 1 adult specimen; Tumuc-Humac, Mitaraka Massif, slope forest on DIADEMA project D trail; 2°13’40”N, 54°27’14”W; 339 m a.s.l.; III.2015; T. Decaëns, E. Lapied leg.; BOLD Sample ID: EW-MI15-0262; MNHN .

OTHER MATERIAL EXAMINED. — French Guiana • 1 juvenile specimen; Tumuc-Humac, Mitaraka Massif, hilltop forest on Sommet en Cloche Inselberg; 2°13’42”N, 54°28’2”W; 638 m a.s.l.; III.2015; T. Decaëns, E. Lapied leg.; BOLD Sample ID: EW-MI15-0107; MNHN • 1 juvenile specimen; Tumuc-Humac, Mitaraka Massif, plateau forest on DIADEMA project A trail; 2°14’38”N, 54°27’32”W; 371 m a.s.l.; III.2015; T. Decaëns, E. Lapied leg.; BOLD Sample ID: EW-MI15-0087; MNHN • 2 juvenile specimens; Tumuc-Humac, Mitaraka Massif, plateau forest on DIADEMA project C trail; 2°13’58”N, 54°26’38”W; 449 m a.s.l.; III.2015; T. Decaëns, E. Lapied leg.; BOLD Sample ID: EW-MI15-0301, EW-MI15-0302; MNHN • 2 juvenile specimens; Tumuc-Humac, Mitaraka Massif, transition forest # 1 Sommet en Cloche Inselberg; 2°13’54”N, 54°27’39”W; 401 m a.s.l.; III.2015; T. Decaëns, E. Lapied leg.; BOLD Sample ID: EW-MI15-0342, EW-MI15-0343; MNHN .

ETYMOLOGY. — This species is named in reference to the type locality situated in the south of French Guiana.

ECOLOGY. — Urobenus guianomeridionalis Bartz & Decaëns, n. sp. has been found in plateau forests (38.46% of specimens), in inselberg hilltop and transition forests (46.15% of specimens), and in slope forests (15.38% of specimens) (Fig. 15D). It is a specialist of epigeic microhabitats such as decaying trunks and litter accumulations on granite rocks (Fig. 15G).

DISTRIBUTION. — Urobenus guianomeridionalis Bartz & Decaëns, n. sp. is only known from the Mitaraka Massif.

DESCRIPTION

External morphology (Fig. 15A, B)

Body shape cylindrical. Body pigmentation dorsally dark grey, ventrally beige to yellow. Body length: 35 mm in the holotype, 35 to 41 mm in the paratypes (average: 37.1 mm; n = 3), after ethanol fixation. Body mass: 0.11 g after ethanol fixation in the holotype, 0.10 to 0.14 g in the paratypes (average: 0.11 g; n = 3). Diameter: 1.2 to 2.8 mm in the preclitellar region, 3.4 to 4 mm in the clitellum, 2.7 to 3 mm in the postclitellar region. Number of segments: 87 in the holotype, 96 to 113 in the paratypes (average: 98.7; n = 3). Prostomium proepilobic. One pair of longitudinal grooves through segments I-II in line of nephridial pores. Setae closely paired, ab beginning in II and cd in III. Setal arrangement aa:ab:bc:cd:dd = 3:1:4:1:13. Clitellum in XV-XXIV, saddle-shaped (Fig. 15A). Genital markings absent. Tubercula pubertatis linear in 1/4XIX (½XIX)-XXIII (Fig. 15B). Male pores not recognised externally, internally open in 19/20, and ovipores in XIV, almost in the border of 13/14, in diagonal to b. Spermathecal pores in 6/7, 7/8 and 8/9. Nephridial pores begining in II.

Internal anatomy (Fig. 15C)

Septa: membranous. Gizzard: muscular and well developed in VI, with an average size (width × length) of 1.87 × 2.07 mm. Calciferous glands: three pairs in VII-IX, of tubular paniculated structure and bean-shaped without appendix in VII-VIII, and sacs/trabecular and slightly curved oval shape in IX. Esophagus-intestine transition in XVII; intestine without caeca.Typhlosole abruptly begining in XXIII/XXV, laminar, long-folded lamella, occupying all the lumen. Hearts: two pairs of large intestinal hearts in X-XI, enclosed in the testes sacs. Excretory apparatus holoic. Testes sacs: in X and XI. Seminal vesicles: two pairs in XI-XII, small and lobulated, occupying only one segment; the pair in XI enclosed in septum and testes sac and the pair in XII free and slightly larger. Spermathecae: three pairs in VII to IX, small elongated without diverticula.

REMARKS

Urobenus guianomeridionalis Bartz & Decaëns, n. sp. is close to Urobenus brevis (Omodeo, 1955) and U. brasiliensis in the position of the clitellum in XV-XXIV (Benham 1886; Omodeo 1955). It differs mainly from the two species in its much smaller size (35 to 41 mm in length and 1.2 to 2.8 mm in anterior diameter, compared to 90 mm and 8 mm in U. brevis, respectively), the setal ratio (3:1:4:1:13, compared to 9:1:10:1: 38 in U. brevis) and spermathecae lacking seminal chambers in U. guianomeridionalis Bartz & Decaëns, n. sp. (Righi 1985). This species corresponds to OTU#052 in Maggia et al. (2021).