Moniligaster gravelyi Stephenson, 1915

Narayanan, S. Prasanth, Paliwal, R., Ahmed, Shakoor, Thomas, A. P. & Julka, J. M., 2023, Redescription of the earthworm Moniligaster gravelyi Stephenson, 1915 (Clitellata Moniligastridae) based on recent collections from Kerala state, India, Zootaxa 5383 (3), pp. 365-374 : 366-371

Moniligaster gravelyi Stephenson, 1915

Moniligaster deshayesi var. gravelyi Stephenson, 1915: 59 .

Moniligaster deshayesi var. gravelyi Stephenson : Stephenson 1923: 123.

Moniligaster gravelyi Stephenson : Gates 1940: 504 (part, excluding Kavalai specimen = M. bahli Narayanan & Julka, 2021 ).

Type locality. Trichur (Thrissur) (10.5276°N, 76.2144°E), Kerala state, India .

Type material. Holotype ZSI ZEV6913/7, Typus perditus.

Material examined. Altogether 40 specimens (11 clitellates, 29 aclitellates). 11 clitellates (2 lightly demarcated), 4 aclitellates (ACESSD/EW/565), evergreen forest patch within deciduous forest, Karineelipacha in Peechi-Vazhani Wildlife Sanctuary (10°39'1.1"N, 76°18'48.4"E), Thrissur District , Kerala State, India, 10 September 2015, 237 m a.s.l., S. Sathrumithra, J. Joseph ; 8 aclitellates (ACESSD/EW/566), deciduous forest, Methanampara in Peechi-Vazhani Wildlife Sanctuary (10°30'0.9"N, 76°30'16"E), Thrissur District , Kerala State, India, 12 October 2013, 399 m a.s.l., D. Kuriakose, S.P. Narayanan, S. Sathrumithra, S.A. Sasi ; 11 aclitellates (ACESSD/EW/567), moist deciduous forest, Karineelipacha in Peechi-Vazhani Wildlife Sanctuary (10°39'14.1"N, 76°18'48.4"E), Thrissur District , Kerala State, India, 13 October 2013, 237 m a.s.l., S.P. Narayanan, D. Kuriakose, S. Sathrumithra, M.A. Shukkur and S.A. Sasi ; 5 aclitellates (ACESSD/EW/568), evergreen forest patch within deciduous forest, Karineelipacha in Peechi-Vazhani Wildlife Sanctuary (10°39'1.1"N, 76°18'48.4"E), Thrissur District , Kerala State, India, 30 October 2014, 237 m a.s.l., S.P. Narayanan, S. Sathrumithra ; 1 aclitellate (ACESSD/EW/570), decaying wood from moist deciduous forest, Nellippara in Chimmini Wildlife Sanctuary (10°28'15"N, 76°28'57.2"E), Thrissur District, Kerala State, India, 13 October 2013, 237 m a.s.l., S.P. Narayanan, D. Kuriakose, S. Sathrumithra, S.A. Sasi, M.A. Shukkur .

Diagnosis. Colour: dorsum bluish grey, ventrum pale. Length 130–174 mm, diameter 5–7 mm, segments 139– 189. Male pores paired, in transverse slits, between bc setal lines, nearer to b setal line. Spermathecal pores paired, in transverse invaginations, between bc setal lines, median to setae c. Genital markings absent. Gizzards 4–5 in segments 12–18. Vas deferens a mass of hairpin loops, mass is equal in size or smaller than testis sac, entering prostate directly without penetrating longitudinal musculature, a little below the ental end in glandular portion. Prostates glandular, flattened, strap-shaped, twisted ectally, widened gradually, surface with shallow depressions and nodulations; prostatic capsule tubular, smooth, highly nodulated surface, margins incised; prostatic duct, short, slightly slender entally, bulbous ectally. Spermathecal atria paired in segment 7, with a single gland of moderate size at each side, long flattened ovoid or with a slight bend at the centre, with bifid duct, about one seventh the length of common atrial duct.

Redescription based on recently collected specimens. External: Colour—dorsum bluish gray, ventrum pale, lateral area marked off by intermediate colour. Body circular in cross section, laterally thickened. Dimensions: 144– 174 mm, width 5–7 mm at segment 9, segments 179–189. Setae lumbricine, minute, visible from segment 3, closely paired; setal formula aa = 9.5–12.67 ab = 0.79–0.90 bc = 12.67–19 cd = 0.26–0.33 dd at segment 8 and aa = 13.33– 16.67 ab = 0.67–1 bc = 20–25 cd = 0.27–0.32 dd at segment 20 (n = 2). Clitellum annular, dark brick red colour on segments ¼9–½14 (= ¾4), lightly demarcated on segment 14 ( Fig. 1A ), setae not visible (indication present). Spermathecal pores paired, in transverse invaginations, hidden in intersegmental furrow 7/8, aligned between bc setal lines, median to c. Secondary male apertures paired, on intersegmental furrow 10/11, aligned between bc, nearer to b setal line, apertures whitish, puckered orifices with tumid lips, pale white patch present on anterior and posterior portions of male apertures in segment 10 and 11. Female pores paired, on intersegmental furrow 11/12, at b setal line, bordered by whitish patch in front and behind ( Fig. 1A ). Nephridiopores minute, recognizable from segment 3, at cd setal lines in one rank. Genital markings absent.

Internal: Septa 5/6–8/9 muscular, septum 9/10 delicate. Gizzards 4–5 in segments 12–18; intestinal origin in segment 25±1. Last hearts in segment 9. Commissures of extra-esophageal vessel present on posterior face of septum 8/9 and 9/10. Testis sacs paired, irregularly ovoid, in segments 10–11, 12; vas deferens long, mass of hairpin loops in segments 9–10, 11, mass is equal in size or smaller than testis sac, touches prostate at sub-ectally, 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, flattened, strap-shaped, extending from segment 11 to segments 13–14, bulging into segment 15 through septum 14/15, twisted ectally, widened entally, glandular (light pinkish colour) with low, slender networks of blood vessels, surface with shallow depressions and nodulations ( Fig. 1B ); prostatic capsule tubular, smooth, highly nodulated surface, margins incised ( Fig. 1C ); prostatic duct, short, slightly slender entally and bulging before entering parietes, duct with light muscular shimmer, just over one fourth of the combined length of gland and duct. Spermathecae paired in segment 8, ampulla ovoid, each with coiled whitish duct penetrating septum 7/8 and entering upper central portion of the single atrial gland in segment 7 to join at junction of short bifid ducts of atrial gland, atrial gland single on each side, moderate size, long flattened ovoid or with a slight bent at the centre ( Fig. 1D ), directed antero-posteriorly or tilted dorso-ventrally, bifid duct of atrial gland ( Fig. 1E ), about one seventh the length of common atrial duct. Ovarian chamber complete, horseshoeshaped. Ovisacs paired in segment 12, extending to segments 13–14, narrower entally or slightly bent. Nephridia avesiculate, present on segment 10.

Variation. Intestinal origin seems to be in segment 29 in a specimen from Nellippara in Chimmini Wildlife Sanctuary (ACESSD/EW/570). Specimens from the Peechi-Vazhani Wildlife Sanctuary had 4 gizzards in segments 12–15 or 14–17 while the sole specimen from the Chimmini Wildlife Sanctuary (ACESSD/EW/570) had 5 gizzards in segments 14–18. In the original description by Stephenson (1915), mentioned that the mass of hairpin loops of vas deferens is larger than testis sac, but in the present study only one specimen from Karineelipacha had this feature. In certain individuals, one of the prostate may not directed posteriorly, instead it is erect, twisted and confined to segment 11. In one specimen from the Methanampara in Peechi-Vazhani Wildlife Sanctuary (ACESSD/EW/566), prostate of RHS turned towards the midventral line and placed beneath the gizzards.

Ingesta. Mainly colloids of fine soil, also rarely small pebbles, sand, barks and strands of plant material.

Habitat. Forests (deciduous, moist deciduous and evergreen forest patch) in the midlands of Thrissur district.

Biology. One specimen from the Methanampara in Peechi-Vazhani Wildlife Sanctuary (ACESSD/EW/566) had 26 regenerated segments at posterior end.

Distribution. Endemic to the midlands of Thrissur district, Kerala State, India. Karineelipacha in Peechi-Vazhani Wildlife Sanctuary*, Methanampara in Peechi-Vazhani Wildlife Sanctuary*, Nellippara in Chimmini Wildlife Sanctuary* and Trichur (Thrissur) (*present records; Stephenson 1915; Gates 1940) ( Fig. 2 ).

Remarks. Apart from M. gravelyi , the group consists of five species, viz., 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 . Species belong to M. gravelyi group, can be characterized by (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. Among these M. gravelyi is very similar to M. bahli , from which it can easily be differentiated by the number of spermathecal atrial glands (single atrial gland in M. gravelyi vs paired in M. bahli ) and character of the prostatic capsule (highly nodulated surface with deeply incised margins in M. gravelyi vs smooth margins and a few nodulations at ental end in M. bahli ). Detailed comparison of ‘ gravelyi ’ species group members are provided in table 1.

Due to the existence of a bifid atrial gland duct beneath the single atrial gland, it is presumed that M. gravelyi originated from Moniligaster species having bifid atrial glands at each common atrial duct. Most likely, it evolved from M. bahli , which is found in the adjacent forested areas of the Parambikulam region.

Gates (1940) examined Stephenson’s (1925) M. deshayesi Perrier, 1872 specimen from Kavalai and he stated that ‘ The internal organs of the Kavalai worm were brittle, and what remained of the spermathecal atrium crumbled into fragments while attempting to discover if the usual two glands were bound together in a common investment of connective tissue, Discrete glands are unrecognizable in both specimens ’. Hence Gates (1940) was not be able to conclude the character of the atrial glands. However, he included it under M. gravelyi . Recently Narayanan et al. (2021) described a new species of the genus viz., M. bahli Narayanan & Julka, 2021 from the three locations of Parambikulam Tiger Reserve of Palakkad district, Kerala. The location of the spermathecal pores, male pores, female pores, prostate, prostatic capsule, ovisacs, atrial gland structure etc. of Kavalai specimen ( Table 2 ) provided by Stephenson (1925) and Gates (1940) agree more closely with M. bahli than M. gravelyi . Moreover, Kavalai is close to the Parambikulam Tiger Reserve.

Thakur et al.’s (2021) report this species from Shendurney Wildlife Sanctuary of Kollam District of Kerala state needs further corroboration. In M. gravelyi vas deferens enters the prostate entally ( Gates, 1940), but as per the figure provided by Thakur et al. (2021), it joins the prostate ectally. Thakur et al. mentioned that atrial glands are single or indistinctly bifid and demarcated by a transverse furrow. But the figure provided shows the opposite, where two distinct spermathecal atrial glands are shown. Owing to the above-discussed anomalies the specimen described under the name M. gravelyi by Thakur et al. seems to be of a different species ( Narayanan et al. 2023).

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Data from: 1 Stephenson (1915); 2 Present study; 3 Jamieson (1977); 4 Narayanan et al. (2021); 5 Narayanan et al. (2022).

Figures

FIGURE 1. Key characters of the Moniligaster gravelyi Stephenson, 1915 (based on the present study). A. Ventral view of anterior region. B. Prostate of right hand side, dorsal view. C. Prostatic capsule of right hand side, slightly stretched, dorsal view. D. Spermatheca of right hand side, slightly stretched, dorsal view. Cl.—Clitellum; C.A.D.—Common atrial duct; F.P.—Female pore; M.H.L.—Mass of hairpin loops; P.C.—Prostatic capsule; P.—Prostate; P.D.—Prostatic duct; S.A.—Spermathecal ampulla; S.A.G.—Spermathecal atrial gland; S.A.G.D.—Spermathecal atrial gland duct; S.D.—Spermathecal duct; S.M.A.—Secondary male aperture; Sp.P.—Spermathecal pore; T.S.—Testis sac; Vd.—Vas deferens.

FIGURE 2. Current known range of Moniligaster gravelyi.