Drawida paliwali Narayanan, 2024

Narayanan, S. Prasanth, Jose, Divya, Kurien, Vijo Thomas & Thomas, A. P., 2024, On three new species of the earthworm genus Drawida Michaelsen, 1900 (Clitellata: Moniligastridae) from south-western India, Zootaxa 5541 (4), pp. 563-581 : 568-569

Drawida paliwali Narayanan , sp. nov.

( Figure 2A–H )

Type material. Holotype: Clitellate ( ZSIK Reg. No. ZSI/WGRC/I.R.INV.26789 ), Karimala Gopuram Hill in Parambikulam Tiger Reserve (10.36333333°N, 76.75258333°E), around 4 km south of Parambikulam round, Palakkad District, Kerala State, India, 1153 m asl, evergreen forest, 2 August 2016, collected by S. Prasanth Narayanan, T. Augustine and S. Sathrumithra . Paratypes: 4 clitellates ( ZSIK Reg. No. ZSI/WGRC/I.R.INV.26790 ), same collection data as for holotype .

Other material. 5 clitellates ( ACESSD/EW/1728 ), same collection data as for holotype .

Diagnosis. Length 54–83 mm, width 3.5–4.5 mm at segment 9, segments 122–141. Setae present from segment 2. Dorsal pores absent. Clitellum annular on segments ¼9– ½14 (= 4¾), portion on ½14 visible only at high magnification. Spermathecal apertures paired, in intersegmental furrow 7/8, aligned at C. Secondary male apertures paired in transverse slits, in intersegmental furrow 10/11, at mid BC. Genital markings absent. Gizzards three to four within segments 13–16. Vas deferens forming a large mass of hairpin loops, mass smaller than testis sac or somewhat equal in size, entering prostate directly, at sub-ental portion of glandular prostate at median side. Prostates paired, glandular, somewhat spheroidal or pear-shaped, erect or bend on itself; prostatic capsule smooth, club-shaped; prostatic duct shorter than glandular portion, vas enters at ental end of capsule. Atrium large, erect, distinctly bilobed, sac-like, surface wrinkled, one lobe each in segments 7 and 8, anterior lobe slightly shorter; duct entering at centre of junction of two atrial lobes.

Description. External: Colour, dorsum brownish grey, ventrum pale in preservation. Body circular in cross section. Dimensions: Holotype: length 83 mm, width 4.5 mm at segment 9, segments 141; paratypes: length 60–73 mm, width 3.5–4 mm at segment 9, segments 122–137; other materials: length 54–71 mm, width 4 mm at segment 9, segments 124–139. Setae lumbricine, small, closely paired, present from segment 2; setal formula AA = 5.5–6 AB = 0.88–1.09 BC = 7.33–8 CD = 0.22–0.27 DD at segment 8 and AA = 14–14.5 AB = 0.933–1.07 BC = 14–19.33 CD = 0.36–0.38 DD at segment 20 (n = 2). Prostomium prolobous. Dorsal pores absent. Clitellum, annular on ¼9– ½14 (= 4¾) ( Fig. 2A, B ), well demarcated by slight swelling in segments 10–13, portion on ½14 visible only at high magnification, reddish colour in preservation, intersegmental furrows distinct, setae visible. Spermathecal apertures paired, in intersegmental furrow 7/8, aligned at C, nearly concealed in furrow, with puckered lips in segments 7 and 8 ( Fig. 2A, B ). Secondary male apertures paired, in transverse slits, in intersegmental furrow 10/11, at mid BC; male genital region is demarcated by a pair of small asymmetrical pale whitish patches, present anterior and posterior of intersegmental furrow 10/11 ( Fig. 2A, B ). Female pores minute in intersegmental furrow 11/12 at mid AB; pale whitish patch present behind female pores on segment 12, reach up to setal arc ( Fig. 2A, B ). Nephridiopores visible from intersegmental furrow 5/6, in single line at CD, throughout. Genital markings absent.

Internal: Pale brownish pigmentation in circular muscle layer. Septum 5/6 weak, septa 6/7/8/9 lightly muscular. Gizzards three to four, within segments 13–16, constantly present on segments 14, 15, anterior one smaller; intestine origin in segment 25±1. Last pair of hearts, commissures of extra oesophageal vessel on posterior face of septum 8/9 and 9/10 not recognizable. Testis sacs paired, large, asymmetrical, dislocated to posterior segments, generally extends in segments 10–15 in left side, and 11–14 in right side, not constricted by septum; vas deferens very long, thick, coiled to form a large mass of hairpin loops, aggregated mass smaller than testis sac or somewhat equal in size, entering prostate directly, at sub-ental portion of glandular prostate at median side. Prostates paired, glandular, somewhat spheroidal or pear-shaped, erect or bend on itself, posteriorly or laterally directed ( Fig. 2C, D ); prostatic capsule smooth, club-shaped ( Fig. 2E, F ); prostatic duct shorter than gland, vas deferens entering at ental end of the capsule. Spermathecal ampulla paired in segment 8, ampulla ovoid or flattish ovoid; atrium large, erect, distinctly bilobed, sac-like, surface of each lobe wrinkled ( Fig. 2G, H ), one lobe each in segments 7 and 8, occupying the cavity of respected segments, anterior lobe slightly shorter; duct long, thick, coiled on the posterior face of septum 7/8, penetrates septum 7/8 close to body wall, entering at centre of junction of two atrial lobes. Ovarian chamber present; ovisacs paired, long, irregular-shaped, extends in segments 12–14, 15, tapering end, occasionally hooked entally. Nephridia holoic, avesiculate.

Variations. In one specimen, the tip of the penis-like organ is slightly everted from the secondary male aperture. Testis sac position: in one specimen it extends in segments 9–10 on right side, 10–13 on left side, another specimen it is in segments 12–15 on right side and in segments 12–14 on left side.

Etymology. The specific epithet ‘ paliwali’ is a masculine eponym in the genitive case. Species is dedicated to Dr. Rahul Paliwal (retired scientist, Zoological Survey of India), as a recognition of his significant contributions to the taxonomic studies on the earthworms in India. He supported the first author’s works on the studies on earthworms by providing materials and expertise.

Ingesta. Chiefly colloids of fine soil with sparse bark-like organic materials.

Habitat. Higher altitude evergreen forest with dark forest-loam soil. Due to the topographical peculiarity, altitudinal variations and the plant species combination in the Karimalagopuram and surrounding areas are unique, and often the forest of this region is referred to as shola forest ( Sasidharan 2002). Common vegetation of this area is dominated by trees, shrubs, and other plants such as Mesua ferrea L., Cullenia exarillata A. Robyns , Palaquium ellipticum (Dalzell) Baill. , Litsea wightiana (Nees) Benth. & Hook. fil., Calophyllum polyanthum Wall. Ex Choisy , Strobilanthes spp. , Christisonia tubulosa (Wight) Benth. Ex Hook. fil, Arisaema murrayi (J. Graham) Hook. etc. ( Sasidharan 2002).

Ecology. Appears to be an endogeic species, as indicated by the pale colour and large quantity of fine soil and a few small particles of organic matter in the intestine. D. paliwali sp. nov. was found to share the type locality with other earthworm species such as Moniligaster bahli Narayanan & Julka, 2021 , M. horsti Gates, 1940 , Megascolex cochinensis phaseolus Stephenson, 1915 , and Notoscolex hastatus (Stephenson, 1915) .

Distribution. Endemic to India: Kerala State: Palakkad District: Karimala Gopuram hill in Parambikulam Tiger Reserve.

Remarks. Drawida paliwali sp. nov. belongs to the robusta species group. Species of this group have glandular prostates and bilobed spermathecal atria. The group consists of eight species, including two of them described in this work: D. robusta robusta ( Bourne, 1886) , D. robusta ophidioides ( Bourne, 1894) , D. ghatensis Michaelsen, 1910 , D. somavarpatana Rao, 1921 , D. robusta cochinensis Stephenson, 1925 , Drawida thomasi Narayanan & Julka, 2017 , D. paliwali sp. nov., and D. proboscidea sp. nov. Characters of the group members are compared in detail in Table 2 . Within this group, two subgroups are recognized: 1) with a distinctly bilobed atrium, and 2) with a slightly bilobed atrium (lobes are like light protuberances). Differences of D. paliwali sp. nov., to other species of the group are as follows:

D. paliwali sp. nov. belongs to the first subgroup with distinctly bilobed atrium. Due to the presence of the large distinct bilobed atrium, it can be readily differentiated from D. ghatensis , D. robusta cochinensis , and D. proboscidea sp. nov., described herein. D. paliwali sp. nov. can be easily distinguished from D. robusta robusta by the shape of the spermathecal atrium (saccular, wrinkled, anterior lobe shorter vs tubular, anterior lobe larger). It can be differentiated from D. robusta ophidioides by small body size (length 54–83 mm vs 310 mm, width 3.5–4.5 mm vs 7 mm), and shape of the spermathecal atrium (saccular vs teat like). Based on the type of prostate, D. paliwali sp. nov. can be ascertained from the D. somavarpatana (single vs bifid). Shape of the atrium differentiates the D. paliwali sp. nov. from the D. thomasi (large saccular vs tubular, each lobe very long, coiled into a compact mass). A detailed comparison of the robusta species group members is provided in Table 2 .

Figures

FIGURE 2. Drawida paliwali Narayanan sp. nov. A, B. Anterior region, ventral view; C. Prostate, slightly stretched, right side, dorsal view; D. Prostate, right side, dorsal view; E, F. Prostatic capsule, right side, dorsal view; G. Spermathecal atrium, slightly stretched, right side, dorsal view; H. Spermathecal apparatus, right side, dorsal view. At—Atrium, Cl—Clitellum, Hl—Hairpin loops, Pc—Prostatic capsule, Pd—Prostatic duct, Pr—Prostate, Sa—Spermathecal ampulla, Sd—Spermathecal duct, Se—Septum, Sm—Secondary male aperture, Sp—Spermathecal aperture, Ts—Testis sac, Vd—Vas deferens.