Hoplochaetella darwini Ahmed and Julka, 2023

Ahmed, Shakoor, Julka, Jatinder Mohan, Banerjee, Dhriti & Marimuthu, Nithyanandam, 2023, A new species of the genus Hoplochaetella Michaelsen 1900 (Clitellata: Octochaetidae) from the Deccan Peninsula Biogeographic Zone, India, Zootaxa 5346 (2), pp. 173-185 : 175-177

Hoplochaetella darwini Ahmed and Julka , sp. nov.

http://zoobank.org/ urn:lsid:zoobank.org:act:289B410E-A87F-4C4A-9F7E-B32F98AF2741

( Figs 1 & 2 )

Material examined. Holotype: Clitellate ( ZSI-GNC-An7269/1 ), India, Tamil Nadu, Salem district, Yercaud (11.776135° N; 78.212211° E); 1401 m a.s.l.; 3 November 2004; leg. A. Mishra and party . Paratypes: 11 clitellate ( ZSI-GNC-An7270/1 ), collection details same as for the holotype.

Etymology. The species is named in honor of Charles Robert Darwin, a naturalist and ecologist who encouraged scientific research on earthworms.

Diagnosis. Small sized worm, length 65–125 mm, width 4–6.5 mm, segments 64–117. Clitellum annular extending on segments 13–16. Setae perichaetine, 5–8 ventral most setae on each side at segment 7 around the spermathecal pores and right or left setae a of segment 8 modified as copulatory, internally associated with accessory glands (copulatory setae a of segment 8 and associated gland were found only in two specimens). Spermathecal pores only one pair in segment 7. Combined male and prostatic pores only one pair, posterior to setal arc of segment 17. Intestine beginning in segment 15; gizzard single, large in segment 7. Last pair of hearts in segment 13. Three pairs of seminal vesicles in segments 9, 10 and 12. Prostates one pair, tubular, long; duct straight. Genital marking glands, sessile, oval or slightly elongated.

Description of holotype. Dimensions: length 125 mm; width 4.3 mm at segment 7, 5 mm at clitellum and 4.5 mm at segment 20. Segments 101. Color of the preserved specimens light brown, clitellum reddish brown. Prostomium epilobic, tongue open. First dorsal pore in intersegmental furrow 4/5 ( Fig. 1B ). Setae perichaetine, uniformly distributed ventrally, with a dorsal break zz = 2.5 yz at segment 5; after clitellum aa = 2 ab and zz = 2 yz at segment 20. Setae 54 and 58 on segments 5 and 20, respectively; some ventral most setae on segment 17 missing. Setae a–h on segment 7 and left setae a on segment 8 modified as copulatory and displaced from their actual position (on segment 7 setae aa moved toward anterior and posterior of setal arc at mid ventral; setae b–h on each side in epidermal tumescence around the spermathecal pores; on segment 8 setae a on left side moved anterior to the setal arc). Clitellum annular, extending on segments 13 ½ –16, setae present, dorsal pores absent. Spermathecal pores only one pair, minute, slight posterior to the setal arc on segment 7, at e, 0.23 body circumference apart ( Fig. 1A ). Female pore single, median, in a whitish oval area, anterior to the setal arc of segment 14 ( Fig. 1C ). Combined male and prostatic pores, minute, at the center of protuberant circular porophores, on segment 17 at de, about equidistant from setal arc of segment 17 and intersegmental furrow of 17/18 ( Fig. 1C ). Male genital region is in a depression, separated by ridge, the depression is highest in anterior of segment 18. Genital markings minute, paired just anterior to intersegmental furrow 17/18 and a single and median on setal arc of segment 18.

Septa 4/5–5/6 thickened, 6/7–8/9 very thin, 9/10–12/13 slightly thickened. Intestine begins in segment 15. Gizzard single, large, cylindrical, in segment 7 (extending in segments 7–8). Typhlosole simple, lamelliform. Nephridia meroic: clustered nephridia present on the anterior face of septa 4/5 and 5/6; micronephridia numerous; meganephridia from segment 20 to the posterior most segments, open into a pair of longitudinal canal, which open separately into the rectum. Last pair of hearts in segment 13, almost equal to the size of heart a pair of commissural vessels in segment 14. Spermathecae in segment 7, ampulla large pear shaped, duct shorter then ampulla with a number of small tubular, chromosome shaped diverticulum encircle the junction of ampulla and duct ( Fig. 2A, C ). Copulatory setae unornamented, pointed ( Fig. 2E ), 0.48–0.5 mm long, 24–27µ diameter. There are six tubular glands (2.5 mm long) associated with copulatory setae at each side in segment 7 and a single left in segment 8. Ovaries, fan shaped in segment 13. Seminal vesicles three pairs in segments 9, 10 and 12, seminal vesicles of 10 is smaller than other two pairs ( Fig. 2B ). Testes and funnels in segments 10 and 11. Vasa deferentia commencing from testes segments slightly enlarge into ejaculatory bulbs before joining the prostatic ducts laterally ( Fig. 2B ). Prostates tubular, long, coiled itself, extending from segment 17 to segment 27; duct long and straight ( Fig. 2D ). Parietal glands paired in segment 17, lateral to ectal ends of prostatic ducts. Calciferous glands shortly stalked, extramural, 4 pairs, in segments 10–13. Genital marking glands sessile, oval, paired, median to prostatic duct in segment 17 and a single and median in segment 18. Intestinal caeca in segments 25 and 26. Penial setae absent.

Variations. Modified copulatory setae and associated gland on/in segment 8 were present only in two specimens among all the examined specimens of new species.

Distribution. Yercaud, Salem district, Tamil Nadu.

Remarks. The proposed new species, Hoplochaetella darwini sp. nov. is compared with other 19 species of the genus based on different morphological and anatomical characters through CAP analysis under PERMANOVA+ ( Fig. 3 ). It showed that the new species is noticeably distinguished from already described species based on the important taxonomic characters such as the position of spermathecae and prostate glands. Based on the position of spermathecae, the new species is segregated from three different groups of described species. The species, Hoplochaetella kinneari ( Stephenson, 1915) is plotted nearer to the proposed new species ( Fig. 3A ) due to its similarity of combined male and prostatic pores paired on segment 17 and the position of seminal vesicles in segments 9,10,12. Considering the number and position of prostate glands, almost all the species got cumulated together ( Fig. 3B ) except the new species and H. kinneari . Though new species hold prostate glands similar to the H. kinneari , it is distinguished due to the variation in the other characters such as the number and position of spermathecae, last pair of hearts and position of copulatory setae and associated glands. The new species possess only one pair of spermathecal pores in segment 7, whereas H. kinneari has two pairs in segment 8. Similarly, the new species has the last pair of hearts in segment 13, whereas H. kinneari holds in segment 12. Further, the proposed new species have copulatory setae and associated glands in segments 7 and 8, H. kinneari has in segment 8. The new species also shared some characters (copulatory setae and associated glands) with Hoplochaetella stuarti ( Bourne, 1886) , but were distinguished based on the number and position of spermathecae and prostates glands ( Table 1 ).

Figures

FIGURE 1. Hoplochaetella darwini sp. nov. A. ventral view, B. dorsal view, C. genital region (cl, clitellum; dp, dorsal pore; fp, female pores; pp, prostatic pores; ps, prostomium; spp, spermathecal pores).

FIGURE 2. Hoplochaetella darwini sp. nov. A&B. internal anatomy, C. spermathecae, D. prostate glands, E. copulatory setae. (cg, copulatory setal glands; di, diverticulum; am, ampulla; gi, gizzard; sv, seminal vesicles; he, hearts; vd, vas deferens; pd, prostatic duct; pg, prostate glands; pe, parietal glands).

FIGURE 3. Canonical Analysis of Principal coordinates (CAP) of the proposed new species Hoplochaetella darwini sp. nov. based on the taxonomic characters: A. Spermathecal pore positions; B. Male and prostatic pore positions. (8, on segment 8; 8_9 on segments 8 and 9; 8_10 on segments 8 and 10; 7_8 on segments 7 and 8; 7 on segment 7; 17_19 on segments 17 and 19; 17 on segment 17; S1–S20 refer checklist of species).