Eutyphoeus unithecus Ahmed & Marimuthu 2025, sp. nov.
Creators: name: Ahmed, Shakoor
name: Banerjee, Dhriti
name: Marimuthu, Nithyanandam
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Animalia
Annelida
Clitellata
Crassiclitellata
Acanthodrilidae
Eutyphoeus
Eutyphoeus unithecus

description: Eutyphoeus unithecus Ahmed & Marimuthu, sp. nov.
http://zoobank.org/ urn:lsid:zoobank.org:act: 825A4379-2F56-435E-AEA3-2C6BF59D2EC1
(Figs 1–2)
Type material. Holotype: Clitellate (ZSI–GNC – An8034/2), Khowai (24.063905° N; 91.600703°E), Khowai district, Tripura, India; 52 m above mean sea level; 26 October 1999 (date here is based on the deposition of specimens in the Zoological Survey of India, Kolkata, whereas specimens were collected during monsoon season); leg. P.S. Chaudhuri. Paratypes: 5 clitellates (ZSI–GNC – An8035/2), collection details same as for as the holotype.
Etymology. The specific name “ unithecus ” is derived from the Latin words “uni” meaning one or single, and “thecae” mean spermathecae which appropriately describes the single spermatheca.
Diagnosis. Length 86–132 mm, width 3–4mm, segments 184–243. Colour brownish (preserved specimens). Segment 5 bi-annulate, further 6–12 tri-annulate. Prostomium tanylobous. Setae lumbricine. First dorsal pore in intersegmental furrow 11/12. Male pores open into a small, oval porophore, median to a setal line, penes absent. Spermathecal pore single, midventral in intersegmental furrow 7/8. Female pores paired, presetal at or slight median to a setal line. Genital markings, unpaired, disc shaped, post-setal, mid ventral on segments 12 (lateral to bb), 13 (bb) and 16 (with in aa), sometime post setal on segments 14 and 15. Typhlosole simple, lamelliform begin in segment 26 ending with the beginning of supra-intestinal glands. Lateral typhlosole, low ridges in segments 27 and 28. Spermatheca with bilobed irregular or dumbbell shaped ampulla, with 2–3 digitiform diverticulum (two lateral and sometime one median). Supra-intestinal glands 4–5 pairs in segments 76, 84–80, 87. Ventral and median intestinal ceaca 4 in segments 31–37. Seminal vesicles in segment 12 extending to segments 13, 14. Prostates tubular, extending from segment 17 to 18 with long wavy duct. Penial setae 4–6 in each battery, length 1.5–2mm, tip slightly curved and pointed, ornamented with triangular teeth. Genital markings glands sessile in segments 12, 13, sometime 14.
Description. External: Medium size worm, colour brownish (preserved specimens). Dimensions: Holotype: length 122mm, width 4mm at clitellum, segments 243; paratypes: length 86–132 mm, width 3–4mm, segments 184– 232. Body cylindrical, segment 5 bi-annulate, 6–12 tri-annulate. Prostomium tanylobous (Fig. 1A, C). First dorsal pore in intersegmental furrow 11/12. Setae lumbricine, present from segment 2, aa:ab:bc:cd:dd =1.9:1.2:2:1.3:7 at 5; aa:ab:bc:cd:dd =1.6:1.2:3:1.6:8 at 8; aa:ab:bc:cd:dd = 2:1:2:1.5:8 at 20. Clitellum annular, on segments ½13–17, setae present and dorsal pores (visible in 13/14). Spermathecal pore single, midventral in intersegmental furrow 7/8 between to aa setal line (Fig. 1B, D). Avestibulate, male pores median to a open in to a small rounded porophore in segment 17, penes absent (Fig. 1B). Female pores paired, pre-setal, slight median to a setal lines. Genital markings unpaired, disc shaped, median, post-setal on segments 12 (lateral to bb), 13 (bb), 16 (aa), slight developed post setal on segment 14 and 15 median to aa (Fig. 1B). Penial setae projecting from the male genital region.
Internal: Septa 4/5–5/6 and 9/10–11/12 strongly thickened, 8/9 thickened, 6/7 and 7/8 absent. Gizzard single, large, in space between septa 5/6 and 8/9; intestine begin in segment 15 (Fig. 2A, E); typhlosole simple, lamelliform begin in segment 26 ending posteriorly in segment 84 with the beginning of supra-intestinal glands; lateral typhlosole, low ridges in segments 27 and 28. Calciferous glands, paired, intramural in segment 12 (Fig. 2E). Lateral intestinal caeca absent, median ventral intestinal caeca 4 in segments 34–37. Supra-intestinal glands 4 pairs in segments 84–87. Nephridia, meroic; enteronephric tuft nephridia in segment 3, numerous exonephric micro-nephridia on parities in segment 5 and posterior segments arranged in transverse rows from segment 18; paired exonephric megameronephridia in each segment posterior to the supra-intestinal glands. Dorsal vessel complete extending to segment 3, with heart in segment 5 and 6; last pairs of heart in segment 13. Metandric, testes and funnels in segment 11, funnels absent in segment 10. Seminal vesicles in segment 12 extending to segment 13 (Fig. 2A). Ovaries and funnels in segment 13, ovaries fan shaped attached on the posterior face septa 12/13. The Vas deferens enlarged before passing into the parietes just behind the prostatic duct (Fig. 2A). Prostates tubular, extending from segment 17 to 18, with long wavy duct. Spermatheca single in segment 8, ampulla large, bilobed, with short duct. Bi-diverticulate, digitiform, ental diverticulum, on lateral sides of the duct (Fig. 2A, B, F). Penial setae 6 per battery, length 1.5–2mm, 24–26µm width, tip spoon shaped and pointed, ornamented with triangular teeth (Fig. 2C, D). Genital markings glands sessile, associated with genital markings of segments 12, 13 and 14.
Variations. Genital markings on segments 13, 14, and 16 are well-developed, whereas the markings on segments 14 and 15 exhibit a slightly whitish color (4 paratypes). Most of the dissected specimens bear one pair of the ental diverticulum, whereas one dissected paratype has three diverticulums. Sometimes the ampulla is constricted by the ventral cord, which forms dumbbell-shaped or irregular two lobes.
Distribution. India: Tripura State: Khowai District: Khowai.
Remarks. The proposed species Eutyphoeus unithecus Ahmed & Marimuthu, sp. nov. differs from its congeners in terms of the number of spermathecae, spermathecal pore position and male pore position. All known species of Eutyphoeus have one pair of spermathecal pores in intersegmental furrow 7/8 and one pair of spermathecae, whereas the new species has a single spermathecal pore at the midventral line between aa and with a single associated spermatheca. Principal component analysis (Fig. 3A) of species coming under the genus, Eutyphoeus showed that there is a strong variability (PC1: 29.5% variance) between the species based on the observed taxonomical characters and the most influenced taxonomical characters observed were genital markings. There was also a variability (PC2: 14.2% variance) between the species and the influenced taxonomical characters observed were the number of spermathecae followed by the position of spermathecal pore and male pore. It was also observed that the proposed species became an outlier (distinguished) from all the species of the similar genus due to the distinct taxonomical characters such as spermathecae pores and male pore position followed by the number of spermathecae. Corresponding to the single spermathecal pore, the male openings are very close together in the proposed species. Based on these characteristics, CAP analysis used male pores position and number of spermathecae as factors to distinguish the proposed one from the other described species (Fig. 3B, C).
description: Published as part of Ahmed, Shakoor, Banerjee, Dhriti & Marimuthu, Nithyanandam, 2025, Two new earthworm species of the genera Eutyphoeus Michaelsen, 1900 and Priodoscolex Gates, 1940 (Crassiclitellata: Acanthodrilidae) from India, pp. 236-248 in Zootaxa 5609 (2) on pages 238-240, DOI: 10.11646/zootaxa.5609.2.5, http://zenodo.org/record/15215020