Drawida proboscidea 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 : 571-573

Drawida proboscidea Narayanan , sp. nov.

( Figures 3A–D , 4A–F )

Type material. Holotype: Clitellate ( ZSIK Reg. No. ZSI/WGRC/I.R.INV.26791 ), Peringuzha (9.956126°N, 76.607257°E), around 7 km south of Muvattupuzha town, Ernakulam District, Kerala State, India, 95 m asl, riverbank of Thodupuzhayar, 29 October 2023, collected by Divya Jose. Paratypes: 4 clitellates ( ZSIK Reg. No. ZSI/WGRC/I.R.INV.26792 ), same collection data as for holotype .

Other materials. Altogether 53 (38 clitellates, 13 aclitellates and 2 juveniles) specimens. 9 clitellates, 6 aclitellates, 2 juveniles ( ACESSD /EW/1718), same collection data as for holotype; 10 clitellates (clitellum is indicated by light colouration) ( ACESSD /EW/1717), Peringuzha (9.956126°N, 76.607257°E), Ernakulam District, Kerala State, India, 95 m asl, riverbank of Thodupuzhayar, 29 September 2023, collected by D. Jose; 9 clitellates, 3 aclitellates ( ACESSD /EW/1719), Peringuzha (9.956126°N, 76.607257°E), Ernakulam District, Kerala State, India, 95 m asl, riverbank of Thodupuzhayar, 27 November 2023, collected by D. Jose; 3 clitellates (clitellum is indicated by light colouration), 3 aclitellates ( ACESSD /EW/1720), Peringuzha (9.956126°N, 76.607257°E), Ernakulam District, Kerala State, India, 95 m asl, riverbank of Thodupuzhayar, 28 December 2023, collected by D. Jose; 7 clitellate (clitellum is well indicated in one specimen, other by light colouration), 1 aclitellate ( ACESSD / EW/1721), Muvattupuzha (9.956126°N, 76.607257°E), Ernakulam District, Kerala State, India, 95 m asl, riverbank of Thodupuzhayar, 27 January 2024, collected by D. Jose.

Diagnosis. Colour bluish purple. Length 43–84 mm, width 3–6 mm at segment 9, segments 168–205. Setae present from segment 2. Prostomium prolobous, occasionally anterior portion of the buccal cavity is everted, with a protruded cylindrical knob-like proboscis. Clitellum, annular on segments ½9–½14 (= 5). Spermathecal apertures small in intersegmental furrow 7/8, aligned at C. Secondary male apertures at intersegmental furrow 10/11, in BC, close to B than C; primary male pores, on the tips of short tubular penes, eversible from a broad flower-like base or wholly concealed within the aperture in retracted condition. Genital markings absent. Gizzards two, within segments 12–14. Vas deferens form a mass of loops, mass smaller than testis sac, entering prostate directly, in middle prostate at median side. Prostates glandular, ovate or club-shaped, erect or bent on itself; prostatic capsule elongately club-shaped, smooth, shiny; duct shorter than gland, ectal end broad dome-shaped, sessile. Atrium, confined to segment 7, bilobed, heart-like, generally bend towards median side, duct long, with a few coils, discharge in atrium at the middle of two lobes.

Description. External: Colour bluish purple on dorsum pale ventrum in life; body circular in cross section. Dimensions: Holotype: length 74 mm, width 4 mm at segment 9, segments 172; paratypes: length 71–84 mm, width 4–5.5 mm at segment 9, segments 166–189; other materials: length 43–84 mm, width 3–6 mm at segment 9, segments 168–205. Setae lumbricine, small, closely paired, present from segment 2; setal formula AA = 6–6.33 AB = 0.75–0.84 BC = 6–7.6 CD = 0.19–0.21 DD at segment 8 and AA = 6–7 AB = 0.75–0.92 BC = 7.5–8.75 CD = 0.19– 0.24 DD at segment 20 (n = 2). Prostomium prolobous; in many clitellate specimens anterior portion of buccal cavity is everted and, in addition to prostomium, a cylindrical knob-like proboscis (c. 1.2 mm long) is protruded out ( Fig. 3A, B ). Dorsal pores absent. Clitellum, annular on ½9–½14 (= 5) ( Fig. 3B, C ), well demarcated in segments 10–13, buff or reddish buff colour (preserved specimens), intersegmental furrows distinct, setae visible. Spermathecal apertures paired, small transverse slits in intersegmental furrow 7/8, pores minute, aligned at C, puckered epidermal thickenings may present in front and back of spermathecal apertures at segments 7 and 8 ( Fig. 3B ). Secondary male apertures paired, in broad transverse slit, in intersegmental furrow 10/11, situated in BC ( Fig. 3B ), close to B than C; male pore situated on tip of short tubular penes ( Fig. 3D ), eversible from a broad, ovoid, multi-layered flower-like base ( Fig. 3B, C ) or wholly concealed within aperture in retracted condition. Female pores minute, hardly visible, one pair on intersegmental furrow 11/12, in B line. Nephridiopores present from intersegmental furrow 2/3, in single line at CD. Genital markings absent.

Internal: Brownish pigmentation in circular muscle layer. Septum 4/5 thin, weak, septa 5/6/7/8/9 thickly muscular. Gizzards globular, two within segments 12–14, constantly present on segment 13, anterior one smaller; intestine origin in segment 20±1. Last pair of hearts in segment 9; commissures of extra oesophageal vessel present on posterior face of septum 8/9, not recognizable on posterior face of 9/10. Testis sac paired, confined to segments 9, 10–11, irregular-shaped; vas deferens, very long, slender, coiled to form a mass of loops, aggregated mass significantly smaller than testis sac, entering prostate directly, in middle of the glandular portion and at its median side. Prostates paired, glandular (reddish orange colour), starkly ovate or club-shaped ( Fig. 4A, B ), erect or bent on itself (at ental end of prostatic duct) posteriorly, in median or lateral directions; prostatic capsule elongately club-shaped, smooth, shiny ( Fig. 4C, D ); prostatic duct smaller than gland, about one fourth of the combined length of gland and duct, duct form a broad sessile hemispherical or dome-shaped muscular ectal end (penial chamber), before entering parietes (penis retracted) or without dome-shape (penis everted). Spermathecal ampulla paired in segment 8, small, ovoid; atrium, confined to segment 7, small to medium size, with two slight lobe-like anterior and posterior protuberances, heart figure-like ( Fig. 4E, F ), generally bend towards median side; spermathecal duct long, slender, with a few coils, penetrating septum 7/8 to discharge in at atrium at middle of two lobes, at ental end towards median side. Ovarian chamber incomplete; ovisacs paired, lobed, rarely converges at mid dorsal surface, thick ectally, tapering towards ental end, extends in segments 11–14. Nephridia holoic, avesiculate.

Variations. Everted knob-like proboscis from buccal cavity is bent to dorsal surface and directed posteriorly in a few specimens. Eversible penes and flower-like bases are retracted in a few specimens: in such individuals, the secondary male aperture has puckered tumid lips on the anterior and posterior sides of segments 10 and 11. In such specimens, the dome-shaped ectal end of the prostatic duct (penial chamber) is much more pronounced than others. In certain specimens, everted penes are found only on one side. In one specimen, ovisacs extend in segments 11–12 on the right side, whereas on the left side they extend in 11–14. In another specimen, the right atrium is of unusual shape, which is erect and digitiform-kind with a middle portion notch and with the spermathecal duct entering at its middle notch. Another one specimen, the right atrium is large, and the anterior and posterior lobes are somewhat longitudinally placed, visible in segments 7 and 8. Occasionally, ovisacs may be twisted to the anterior or dorsal side.

Etymology. The specific epithet ‘ proboscidea’ (feminine, adjective) is a morphonym. Derived from the Latin word “ proboscis ”, meaning ‘an elongated tube from the head or connected to the mouth of an animal’. It refers to the presence of everted proboscis-like projection on the peristomium of this new species.

Ingesta. Mainly fine soil, with small sand particles and a few particles of small bark-like organic matter.

Habitat. Riverbank of Thodupuzhayar, a tributary of the Muvattupuzha River at Peringuzha with sandy-loam soil. Common vegetation of this area is dominated by native trees, herbs, and grasses such as Ochreinauclea missionis (Wall. Ex G.Don) Ridsdale , Ficus racemosa L., Cocos nucifera L., Axonopus compressus (Sw.) P. Beauv. , Cyperus sp. , Polygonum sp. , and exotic invasive herbaceous plants and vines such as Sphagneticola trilobata (L.) Pruski, Mikania micrantha Kunth , etc.

Biology. Autotomy and regeneration of lost parts are noticed. Many specimens were found with regenerated segments (mainly 12–22 segments) at the posterior end.

Ecology. Appears to be an endogeic species, as indicated by the large quantity of fine soil with a small amount of sand and a few particles of bark-like organic matter in the intestine. D. proboscidea sp. nov. was found to coexist with various endemic ( D. ghatensis , D. travancorensis , Megascolex polytheca uniquus Aiyer, 1929 ) and exotic ( Pontoscolex corethrurus (Müller, 1857) , Metaphire houlleti (Perrier, 1872) , and Ocnerodrilus occidentalis Eisen, 1878 ) earthworm species at the type locality.

Distribution. Endemic to India: Kerala State: Ernakulam District: Peringuzha ( Fig. 4 ).

Remarks. Drawida proboscidea sp. nov. belongs to the second subgroup ‘with slightly bilobed (lobes are light protuberances) atrium’ of the robusta species group. Members of this group comprise the new species described here, D. proboscidea sp. nov., D. ghatensis , and D. robusta cochinensis . D. proboscidea sp. nov. can be easily distinguished from D. ghatensis by the shape of the prostate (club-shaped vs mushroom-shaped) and the number of gizzards (2 in segments 12–14 vs 4–6 in segments 14–22). Whereas it can be differentiated from D. robusta cochinensis based on the body length (43–84 mm vs 125–130 mm), shape of the prostate (club-shaped vs subspherical), and number of gizzards and their position (two in segmental range of 12–14 v s five to six in the segmental range of 15–21 of 15–21). It can be easily distinguished from other members of the robusta species group by the characteristics as given in Table 2 .

Figures

FIGURE 3. Drawida proboscidea Narayanan sp. nov. A. Knob-like proboscis from the buccal cavity, dorsal view, B. Ventral view of the anterior region; C. Male genital region, ventral view; D. Everted penis from the flower-like base, right side, lateral view. Cl—Clitellum, Mg—Male genital region, Mp—Male pore, Pb—Proboscis, Pn—Penis, Sp—Spermathecal aperture.

FIGURE 4. Drawida proboscidea Narayanan sp. nov. A, B. Prostate, with testis sac, right side, dorsal view; C, D. Prostatic capsule, right side, dorsal view; E. Spermathecal atrium, right side, dorsal view, F. Spermathecal apparatus, right side, dorsal view. At—Atrium, Pc—Prostatic capsule, Pd—Prostatic duct, Pr—Prostate, Sa—Spermathecal ampulla, Sd—Spermathecal duct, Ts—Testis sac, Vd—Vas deferens.