Eutyphoeus Michaelsen, 1900

Rodingpuia, Christopher, Hmar, Lalthanzara, Julka, Jatinder, Chawngthu, Zothansanga, Mathipi, Vabeiryureilai, Lalfelpuii, Ruth, Kumar, Nachimuthu Senthil, Gurusubramaniun, Guruswami, Lalchhandama, Kholhring & Chhakchhuak, Lalbiakzuala, 2024, A new species of Eutyphoeus earthworm (Clitellata: Acanthodrilidae) from Mizoram, North-East India, Zootaxa 5424 (2), pp. 214-224 : 217-219

Genus Eutyphoeus Michaelsen, 1900

Materials examined. Holotype: PUCZM A/ VI/1050 , clitellate (mature) specimen, 149 mm in total length, 8.5 mm diameter, dissected, collected from the roadside at Khawrihnim village , Mizoram, India, coll. Lalthanzara. Paratypes: six clitellate specimens PUCZM A/ VI/1051 - PUCZM A/ VI/1056 from Khawrihnim village , Mamit and Dampui village, Mizoram, India. coll. Lalthanzara and Rodingpuia.

Etymology. The name rihnimensis is given to this species after its type locality, Khawrihnim. In the native Mizo language, khaw/khua means village, and rihnim is a tree belonging to the genus Ficus .

Diagnosis. Length 105–149 mm, diameter 5.5–8.5 mm, segments 107–198. Prostomium prolobic. First dorsal pore on 11/12. Spermathecal pore paired on 7/8. Avestibulate, male pore on 17. Penes 4 lobes (2 anterior and 2 posterior). Genital markings on 16 and 18 at ab. Lateral intestinal caeca on 28. Metandric, bidiverticulate ental spermathecae. Supra-intestinal glands 5 pairs, in 81-88. Prostate glands tubular, paired in 17-22. Penial setae with curved tips.

Description. Length 149 mm, diameter 8.5 mm, segments 148. Live colour brownish grey, deep pigmentation in pre-clittellar portion; prostomium prolobic. First dorsal pore on 11/12. Clitellum annular from ½13 extends up to ½17. Setae lumbricine, aa =0.4 ab = 0.8 bc = 0.4 cd = 0.7 dd on segment 12, aa = 0.3 ab = 0.7 bc = 0.4 cd = 0.8 dd on segment 24. Spermathecal pores paired, small transverse slits, slightly lateral to b setal line, on segment 7/8. Female pore single, pre-setal, at a setal line on the left side of segment 14. Male genital region avestibulate, male pores discharge into the body in C-shaped conspicuous structures with penes projecting into 4 lobes (2 anterior and 2 posterior) from the male porophore on segment 17 ( Fig. 3C ). Genital markings paired, post-setal on segments 16 and 18 at ab ( Fig 3B ).

Septa 4/5/6 and 10/11 muscular, without septum 7/8/9. Oesophagus with large gizzard in 7-9 ( Fig. 3E ). Intestine begins in 15. Lateral intestinal caeca paired, tubular, directed upwards in 28 ( Fig. 3F&G ). Ventral intestinal caeca 10, small, unpaired at mid-ventral line in 33-43 (±1). Supra-intestinal glands 5 pairs, in 81-88 ( Fig. 3H ). Typhsole lamelliform, begins from 25-62. Dorsal blood vessel aborted, terminated with the heart of 7 (i.e. behind gizzard). Metandric testis, male funnels absent in segment 10; seminal vesicles paired, attached to the skin on the intersegmental groove at 11/12, left vesicle slightly longer, extending up to 14 ( Fig. 3E ). Prostate glands tubular, paired in 17-22. Spermathecae paired, ental bidiverticulate, large kidney-shaped ampulla, very short median and lateral ental diverticula ( Fig. 3D ). Penial setae ornamented with closely spaced irregular rows of 5 or 7 groups of spines ( Fig. 4B&C ), reduced in number towards the pointed and curved tip ( Fig. 4A ). Genital marking glands absent.

Variations. Variations in length and diameter are observed in all specimens. Two paratype specimens differ from the holotype in the appearance of four finger-like projections from the male porophore. The other paratype specimens possess a pile of lobe-like structures with a blunt end, unlike the holotype. Genital markings show variations between type specimens. The holotype and one of the paratypes have paired genital markings on segments 16 and 18 at ab, post-setal, while four paratypes had no markings on segment 16. Genital marking was also observed on segment 9, post-setal at aa in two of the paratypes.

Remarks. The new species belongs to the E. gigas group ( Gates 1958) characterized by dorsal blood vessels aborted with the heart on segment 7, avestibulate, spermatheca diverticulate and stalked, metandric, female pore present on the left side of segment 14. It can be distinguished from other species of the group such as E. gigas (Stepehenson 1917) , E. plenus ( Gates 1958) and E. serei ( Tiwari et al. 2021) by the list of characters given in Table 1 .

......continued on the next page

Figures

FIGURE 3. Eutyphoeus rihnimensis sp. nov. A. Illustration of male genital field, B. male genital field, C. Penes 4 lobes (2 anterior lobe and 2 posterior lobe), D. Spermathecae, E. Gizzard, seminal vesicles and prostate gland, F&G. Lateral intestinal caeca, H. Supra-intestinal glands. (al, anterior lobe; am, ampulla; di, diverticulum; gi, gizzard; gm, genital markings; ic, intestinal caeca; mp, male pore; pg, prostate glands; pl, posterior lobe; si, supra-intestinal glands; sv, seminal vesicles).

FIGURE 4. Eutyphoeus rihnimensis sp. nov. A. Illustration of penial setae, B&C. Penial setae under S.E.M, B. Anterior portion of penial setae ornamented with less spaced rows of spines, C. Posterior portion of penial setae ornamented with closely spaced rows of spines