Guianodrilus corticolous Bartz & Decaëns, 2024

Decaëns, Thibaud, Bartz, Marie Luise Carolina, Bartz, arolina, Feijoo-Martínez, Alexander, Goulpeau, Arnaud, Lapied, Emmanuel, Marchán, Daniel F., Maggia, Marie-Eugénie, Papuga, Guillaume & James, Samuel W., 2024, Earthworms (Oligochaeta, Clitellata) of the Mitaraka range (French Guiana): commented checklist with description of one genus and eighteen species new to science, Zoosystema 46 (9), pp. 196-244 : 235-237

Guianodrilus corticolous Bartz & Decaëns , n. sp.

( Fig. 22 )

urn:lsid:zoobank.org:act:8F945CA5-277B-42BD-9502-5CA745DAF6D3

TYPE MATERIAL. — Holotype. French Guiana • Adult; Tumuc-Humac, Mitaraka Massif , lowland forest on DIADEMA project D trail, in decaying trunk; 2°13’58”N, 54°27’7”W; 318 m a.s.l.; III.2015; T. Decaëns, E. Lapied leg.; BOLD Sample ID: EW-MI15-0307 ; MNHN.

Paratypes. French Guiana • 1 adult specimen; Tumuc-Humac, Mitaraka Massif , lowland forest on DIADEMA project A trail; 2°14’34”N, 54°27’54”W; 327 m a.s.l.; III.2015; T. Decaëns, E. Lapied leg. (1 specimen); BOLD Sample ID: EW-MI15-0251 ; CEFE

ETYMOLOGY. — The name of the species refers to the microhabitat where the type specimens have been collected.

ECOLOGY. — The two known specimens of G. corticolous Bartz & Decaëns , n. sp. have been found in decaying trunks in a lowland forest ( Fig. 23 ).

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

DESCRIPTION

External morphology ( Fig. 22 )

Body shape cylindrical, slightly flattened posteriously. Body pigmentation absent. Body length: 19 mm in the holotype, 21 mm in the paratype, after ethanol fixation. Body mass: 0.01 g after ethanol fixation in the holotype, same in the paratype. Diameter: 1.0 mm in the preclitellar region, 1.0 mm in the clitellum, 1.0 to 1.2 mm in the postclitellar region. Number of segments: 87 in the holotype, 81 in the paratype. Prostomium proepolobic. Dorsal pores: absent. Setae closely paired. Setal arrangement aa:ab:bc:cd = 5:1:5:1, dd> ½ Ø. Clitellum in XIV-2/3XVIII, saddle-shaped. Genital markings absent. Male pores one pair in XVII, like papillae and with ejected material, and ovipores in XIV, almost in the border of 13/14, in diagonal to b. Spermathecal pores not visible. Nephridial pores in line of C.

Internal anatomy ( Fig. 22 )

Septa: 6/7 to 8/9 membranous but thicker than the others. Gizzard: absent. Calciferous glands: one pair in IX, peanutshaped, attached by the bottom and projected laterally with internal united lamella. Esophagus-intestine transition in XIV. Typhlosole absent. Single dorsal blood vessel. Hearts: three last pair in X-XII (latero-esophageal) and VIII and IX (lateral). Excretory apparatus holoic. Prostatic glands: one pair in XVII, short duct forming long elongated tubes (tubular) folded and tangled with irregular directions for each tube in the ventral part, about 1.5 to 2.0 mm long. Ovaries: one pair in XIII. Testes and funnels: two pairs of brushy testes and iridescent male funnels, free, in X and XI. Seminal vesicles: two pairs in XI and XII, occupying a single segment with lobular-globular shape. Spermathecae: one pair in IX, big folded sac with very short duct and two iridescent diverticula baseball-bat-shaped (bidiverticulate), one projected ventral side and other dorsal side, ental to the duct.

REMARKS

This species corresponds to OTU#089 in Maggia et al. (2021). It is the first species described from its genus. We determined it to be new based on the summary of genus characters implicit in the keys of Hernández-García et al. (2018b) and Fragoso & Rojas (2009). Guianodrilus Bartz & Decaëns , n. gen. is similar to Pygmaeodrilus Michaelsen, 1890 by the absence of the gizzard, calciferous glands paired in IX, male and female reproductive system holandric and metagynous, respectively, diverticulate spermathecae, and dorsal pores absent ( Michaelsen 1890). The principal difference between the new genus and Pygmaeodrilus are the last hearts in XII in Guianodrilus Bartz & Decaëns , n. gen. instead of XI in Pygmaeodrilus ; and intestinal origin in XIV ( Guianodrilus Bartz & Decaëns , n. gen.) instead of XII ( Pygmaeodrilus ). The seminal vesicles of Guianodrilus Bartz & Decaëns , n. gen. are in XI and XII, but in IX and XII in Pygmaeodrilus . The prostates of Guinanodrilus Bartz & Decaëns , n. gen. have a relatively thick glandular parts and short ducts, compared to the thinner glands and relatively long ducts of Pygmaeodrilus . Both genera have more than one diverticulum on the spermathecae. The Brazilian species Pygmaeodrilus amapaensis Righi, 1988 differs from its African congeners in having a more posterior intestinal origin (XIII) but has last hearts in XI. It has a longer clitellum (XIII-XX) than G. corticolus Bartz & Decaëns, n. sp., and has genital markings near the combined male and prostatic pores, which are on elevated papillae. However, the two share the elevated papillae of the male pores. One could consider transferring P. amapaensis to Guianodrilus Bartz & Decaëns , n. gen. but that would remove all but one distinction, the posterior intestinal origin. It might be better to await the discovery of further members of both genera in South America.

Figures

FIG. 22. — Guianodrilus corticolous Bartz & Decaëns n. sp.: A, external and lateral view of the anterior body (arrows indicate the end of clitellum and male and prostatic pore position); B, external and dorsal view of the anterior body (segment number indicate the end of clitellum); C, external and ventral view of the anterior body (arrows indicate the clitellum and male field);D, Internal view indicating the pair of prostates and male and prostatic pore;E, internal view indicating male and female strutures; F, detail of a calciferous gland after being extracted from the dissection. All images from the holotype; CG, calciferous gland; CL, clitellum; MP, male pore; PP, prostate pore; PG, prostatic gland; SP, spermathecae; TS, testes; OV, ovaries; CG, calciferous gland. Scale bars: A, 2 mm; B, D, 1 mm; e, 0.5 mm; F, 200 μm.

FIG. 23. — Guianodrilus corticolous Bartz & Decaëns n. sp.: A, habitat preferences; B, microhabitat preferences. N, total number of specimens in the dataset.