Moniligaster gatesi Ahmed & Narayanan 2025, sp. nov.
Creators: name: Narayanan, S. Prasanth
name: Ahmed, Shakoor
name: Thomas, A. P.
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Animalia
Annelida
Clitellata
Moniligastrida
Moniligastridae
Moniligaster
Moniligaster gatesi

description: Moniligaster gatesi Ahmed & Narayanan, sp. nov.
(Figures 1, 2)
Type material. Holotype: Clitellate (ZSI-GNC-An7976/2), Ooty (= Udhagamandalam or Udhagai) (11.4187°N; 76.7110°E), Nilgiris District, Tamil Nadu State, India, ca. 2350 m a.s.l., botanical garden, 29 th November 2004, collected by A. Mishra and party. Paratypes: 5 clitellates, 1 aclitellate (ZSI-GNC-An7977/2), same collection data as for holotype.
Diagnosis. Length 87–160 mm, width 5–7 mm at segment 9, segments 116–181. Setae present from segment 2. Dorsal pores absent. Clitellum annular, on segments ⅓9–14 (= 5⅓), setae visible. Spermathecal apertures paired, concealed in intersegmental furrow 7/8, between bc setal lines, nearer to c setal line. Secondary male apertures paired, in transverse slits, between bc setal lines, nearer to b setal line. Genital markings absent. Gizzards four to five, within segments 13–18. Vas deferens form a mass of hairpin loops, mass size about equal to testis sac, entering prostate directly without penetrating longitudinal musculature, a little below the ental end. Prostates glandular, flattened, strap-shaped, ectal portion narrowed, slender, tubular, wavy; prostate surface with shallow depressions and nodulations; extends in segments 11–13, 14; prostatic capsule tubular, smooth, low nodulated surface, margins nodulated; prostatic duct, short, slender entally, bulbous ectally. Spermathecal atria paired in segment 7 on both side, atrial glands moderate sized, long flattened human nail-like, about one fifth the length of common atrial duct.
Description. External: Colour light greyish brown in preservation. Body seems to be circular, bit compressed due to preservation. Dimensions: Holotype —length 125 mm, width 7 mm at segment 9, segments 158; paratypes — length 87–160 mm, width 5–7 mm at segment 9, segments 116–181. Setae lumbricine, very small, closely paired, present from segment 2; setal formula aa: ab: bc: cd: dd = 2.2–2.4:0.19–0.20:2–2.2:0.17–0.18:8.5–9 at segment 8 and aa: ab: bc: cd: dd = 1.6–2.8:0.18:1.6–2.9:0.18:8.8–9.2 at segment 20 (n = 2). Clitellum annular, reddish to maroon colour (in preservation) on segments ⅓9–14 (= 5⅓) (Fig. 1A–B), lightly demarcated on segment 14 (Fig. 1A), setae visible (in high magnification). Spermathecal apertures paired, concealed in intersegmental furrow 7/8, transverse orifices, puckered, aligned between bc setal lines, nearer to c. Secondary male apertures paired, on intersegmental furrow 10/11, aligned between bc setal lines, nearer to b line, demarcated by pale whitish colour (Fig. 1A–B). Female pores minute, paired, on intersegmental furrow 11/12, at b setal line. Nephridiopores minute, recognizable from intersegmental furrow 3/4, at cd setal lines in one rank. Genital markings absent.
Internal: Pigmentation light brownish in circular muscle layer. Septa 5/6 muscular, 6/7–8/9 strongly muscular, septum 9/10 delicate. Gizzards four to five, in segments 13–18, anterior one smallest; intestine origin in segment 26±1. Last hearts in segment 9. Commissures of extra-oesophageal vessels on posterior face of septum 8/9 and 9/10 not recognisable. Testis sacs paired, irregularly shaped, in segments 10–11; vas deferens long, mass of hairpin loops in segments 9–10, mass size about equal to testis sac, pass along inner face of prostate, entering the prostate directly, at median side, a little below ental end in glandular portion, without penetrating longitudinal musculature. Prostates paired, glandular (light reddish colour), with a few blood vessels, flattened, strap-shaped, about 10–12 mm long, widened entally, ectal portion narrowed, slender, tubular, wavy, prostate surface with shallow depressions and nodulations (Fig. 2A–B), extends in segments 11–13, 14, often bulging into segment 15 through septum 14/15; prostatic capsule tubular, smooth, low nodulated surface, margins nodulated (Fig. 2C–D); prostatic duct short, slender entally, bulbous ectally before entering parietes, duct with light muscular shimmer, about one eighth of the combined length of gland and duct. Spermathecal ampulla paired, pear-shaped in segment 8, each with long, coiled, whitish duct penetrating septum 7/8 and entering atrial glands from median side in segment 7 to join at junction of short bifid ducts of atrial gland, atrial glands moderate sized, paired on each side, human nail-like in appearance, directed antero-posteriorly or tilted dorso-ventrally, adherent together, each gland height from ventrum to dorsal side ca. 2 mm, anterio-posterior length at dorsal surface ca. 3–4 mm, width 2–4 mm, (Fig. 2E), bifid duct of atrial gland short (Fig. 2F), about one fifth the length of common atrial duct. Ovarian chamber complete, horseshoe shaped, in segment 12. Ovisacs paired in segment 12, extending between segments 13 and 16, narrower entally or slightly bent like a question mark (?). Nephridia avesiculate, present on segment 10.
Variations. Nephridiopores are dislocated towards dorsal side on segment 7, in one paratype. In one specimen, lateral side of the spermathecal atrial glands are slightly fused together, whereas in the median side separation is clearly visible, but it can easily separate into two by using needle without considerable efforts, however the opposite side the atrial glands division is complete.
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Data from: 1 Stephenson (1915); 2 Narayanan et al. (2023b); 3 Jamieson (1977); 4 Narayanan et al. (2021a); 5 Narayanan et al. (2022).
Etymology. Specific epithet ‘ gatesi’ is a masculine noun in genitive case, named after the most prominent and highly prolific American earthworm taxonomist Dr Gordon Enoch Gates (14 February 1897 – 11 June 1987), who described 5 new species of Moniligaster in the 20 th century. Gates is the most notable moniligastrid taxonomist, who described around 32% of all the known valid moniligastrid species (Narayanan et al. 2024a). Apart from taxonomy, he is remembered for his vastly significant contributions in the field of earthworm biology, morphology, distribution and classification (Narayanan et al. 2023a).
Ingesta. Fine colloids of soil.
Habitat. Higher altitude flower garden. Ooty is located within the Nilgiri Plateau, which is dominated by the shola-grassland complex.
Ecology. Appears to be an endogeic species, as indicated by large quantity of fine soil, in the intestine.
Distribution. Endemic to Western Ghats mountain ranges of India: Tamil Nadu State: Nilgiris District: Ooty (Fig. 3).
Remarks. M. gatesi sp. nov. belongs to gravelyi group of Moniligaster species. Species belonging to gravelyi group, can be differentiated by the following characters (i) vas deferens opening directly into the prostate, i.e. without penetrating the longitudinal muscle layer, (ii) spermathecal atria confined to segment 7, and (iii) leaflet-like glands absent on the vas deferens (Narayanan et al. 2021a, 2022, 2023b). Apart from M. gatesi sp. nov., the group consists of six species, viz., M. gravelyi Stephenson, 1915, M. troyi Jamieson, 1977, Moniligaster bahli Narayanan & Julka, 2021, M. blakemorei Narayanan & Julka, 2021, M. keralensis Narayanan & Julka, 2021 and M. julkai Narayanan & Paliwal, 2022. Among gravelyi group of species, M. gatesi sp. nov., shows close similarity with M. gravelyi and M. bahli. M. gatesi sp. nov., can easily be differentiated from the very similar looking M. gravelyi by the number of spermathecal atrial glands (paired atrial glands at each side vs single undivided atrial gland at each side) and character of the prostatic capsule (shallow nodulated surface and margins vs highly nodulated surface with incised margins). M. gatesi sp. nov., can be separated from M. bahli by character of the prostatic capsule (shallow nodulated surface and margins vs sinuous at ental end with a few nodulations, rest smooth) and extension of ovisacs (reach up to segments 13–16 vs up to segment 20). Both M. gravelyi and M. bahli are distributed south of the Palakkad Gap (Stephenson 1915, Narayanan et al. 2021a, 2023a, b, 2024c), whereas the M. gatesi sp. nov., is distributed north of the Palakkad Gap (Fig. 3). The altitude-wise distribution of these species also differs; according to Narayanan et al. (2021a, 2022, 2023b), M. gravelyi and M. bahli are known to live in areas between 237 and 399 m a.s.l. and 566 and 1153 m a.s.l., respectively. Whereas, M. gatesi sp. nov., is known to inhabit regions of the Western Ghats that are higher than 2000 m above sea level. Detailed comparison of ‘ gravelyi ’ species group members are provided in Table 1.
description: Published as part of Narayanan, S. Prasanth, Ahmed, Shakoor & Thomas, A. P., 2025, Description of a new species of the earthworm genus Moniligaster Perrier, 1872 (Clitellata, Moniligastridae) from the Nilgiri Biosphere Reserve of Tamil Nadu State, India, pp. 142-154 in Zootaxa 5589 (1) on pages 144-150, DOI: 10.11646/zootaxa.5589.1.12, http://zenodo.org/record/14896843