Neogaster tumuchumac Decaens & Bartz 2024, n. sp.

Neogaster tumuchumac Decaëns & Bartz, n. sp.

(Fig. 18)

urn:lsid:zoobank.org:act: F77F9096-722E-473A-AC3F-7706BD642410

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-MI15-0081; MNHN.

Paratypes. French Guiana • 2 adult specimens; Tumuc-Humac, Mitaraka Massif, plateau forest at base camp; 2°14’2”N, 54°27’1”W; 331 m a.s.l.; III.2015; T. Decaëns, E. Lapied leg.; BOLD Sample ID: EW-MI15-0280, EW-MI15-0281; CEFE • 2 adult specimens; 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-MI15-0085, EW-MI15-0086; MNHN • 3 adult specimens; Tumuc-Humac, Mitaraka Massif, slope forest on DIADEMA project A trail; 2°14’16”N, 54°27’7”W; 344 m a.s.l.; III.2015; T. Decaëns, E. Lapied leg.; BOLD Sample ID: EW-MI15-0206, EW-MI15-0207, EW-MI15-0208; MNHN • 1 adult specimen; Tumuc-Humac, Mitaraka Massif, slope forest on DIADEMA project C trail; 2°14’5”N, 54°26’42”W; 377 m a.s.l.; III.2015; T. Decaëns, E. Lapied leg. (1 specimens); BOLD Sample ID: EW-MI15-0080; MNHN.

OTHER MATERIAL EXAMINED. — French Guiana • 1 juvenile specimen; 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-MI15-0300; MNHN • 1 juvenile specimen; Tumuc-Humac, Mitaraka Massif, slope forest on DIADEMA project A trail; 2°14’16”N, 54°27’7”W; 344 m a.s.l.; III.2015; T. Decaëns, E. Lapied leg.; BOLD Sample ID: EW-MI15-0213; MNHN.

ETYMOLOGY. — This species is named in reference to the Tumuc Humac mountains to which the Mitaraka Massif belongs to.

ECOLOGY. — Neogaster tumuchumac Decaëns & Bartz, n. sp. has been found in decaying trunks in both slope (54.55% of specimens) and plateau forests (45.45% of specimens) (Fig. 18C, D).

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

DESCRIPTION

External morphology (Fig. 18A, B)

Body shape cylindrical, slightly flattened posteriously. Body pigmentation dorsally light yellow-brown, ventrally lighter. Body length: 12 mm in the holotype, 12 to 17 mm in the paratypes (average: 14.7 mm; n = 3), after ethanol fixation. Body mass: 0.002 g after ethanol fixation in the holotype, 0.002 to 0.008 g in the paratypes (average: 0.006 g; n = 3). Diameter: 1.0 to 1.3 mm in the preclitellar region, 1.0 to 1.1 mm in the clitellum, 0.9 to 1.3 mm in the postclitellar region. Number of segments: 76 in the holotype, 81 to 91 in the paratypes (average: 86; n = 3). Prostomium tanylobic. Dorsal pores begining in 5/6. Setae closely paired, beginning in II, ab ventral and cd sub-ventral. Setal arrangement aa:ab:bc:cd = 4:1:4:1, dd> ½ Ø. Clitellum in XIII-XX, annular. Genital markings in in some specimens in IV to VI (bc position) and VII to X (ab position); acanthodriline male field in XVII-XIX, delimited posteriously by a transversal lip in XIX. One pair of ventral male pores in XVIII, and ovipores not visible. Spermathecal pores not visible. Nephridial pores not visible.

Internal anatomy

Septa: membranous. Gizzard: absent. Calciferous glands: two pairs in XIV and XV, with lamellar structure, kidney-shaped and attached through the middle inside. Esophagus-intestine transition in XVII. Typhlosole absent. Hearts: five pairs, last three intestinal bigger and last pair in XII. Excretory apparatus: not easy to observe due to the minute size of the species, probably meronephridial. Prostatic glands: two pairs in XVII and XIX, elongated spatula or folded tube-shaped. Ovaries: one pair in XIII.Testes: two pairs of testes sacs in X and XI, the one in X less developed. Seminal vesicles: one or two pairs in XI (in some specimens) and XII. Spermathecae: two pairs in VIII and IX, sometimes an additional smaller pair or a single one in VII, all bowling pin-shaped, sometimes crossing the septa with the ental ampulla displaced to next segment.

REMARKS

As previously stated, N. tumuchumac Decaëns & Bartz, n. sp. is closely related to N. csuzdii Bartz & Decaëns, n. sp. due to the absence of gizzard and the membranous anterior septa (Table 5). It is the smallest known species within the genus, with body size not exceeding 17 mm in the material examined. It differs from other Neogaster by the presence of two pairs of spermathecae in VIII-IX, whereas other species have one (in N. csuzdii Bartz & Decaëns, n. sp.), three (in N. angeloi and N. americanus), four (in N. gavrilovi) or five (in N. aidae) (Cernosvitov 1934; Righi & Caballero 1970; Righi 1975, 1988). Neogaster tumuchuma c, Decaëns & Bartz, n. sp. is clearly separated from N. csuzdii Bartz & Decaëns, n. sp. from its COI barcode (Table 3). This species corresponds to OTU#077 in Maggia et al. (2021).