Righiodrilus omagua, Feijoo & Lavelle, 2023

Feijoo, Alexander & Lavelle, Patrick, 2023, New species and records of earthworms (Annelida, Oligochaeta: Crassiclitellata) in small holder farming systems in the Peruvian Amazon, Zootaxa 5255 (1), pp. 157-170 : 159-160

Righiodrilus omagua , sp. nov

( Figure 1A–B , Table 1 )

Etymology. The new species was named in recognition of and homage to the Omaguas indigenous people who live in the Alto Amazonia. Omaguas, occupied the upper reaches of the Amazon River from the mouths of the Napo River to the Putumayo ( Ullán, 2007).

Holotype. Clitellate specimen (CNLT-UTP-0354). Perú, Department of Loreto, Santa Rosa farm (5°53'56'' S, 76°10'34'' W). Secondary forest locally identified as Purma. 168 m. a.s.l. Sampling depth: 10-20 cm. 16 October 2016. Collectors: Obed Carrascal Torres.

Paratypes. 11 adults, 10 juveniles (CNLT-UTP-0355). Same collection data as holotype .

Description. Endogeic species, with a cylindrical, nonpigmented body. Holotype: length 34.2 mm, diameter 1.22 mm in preclitellar region, 1.15 mm at clitellum, 1.13 mm in postclitellar region. Number of segments: 140. Paratypes (11 adults, 10 juveniles): Adult 1: 28.4 mm long, diameter 1.25 mm in preclitellar region, 1.31 mm at clitellum, 1.18 mm in mid-posterior region, number of segments: 109. Adult 2: 29.5 mm long, diameter 0.93 mm in preclitellar region, 1.26 mm at clitellum, 1.1 mm in mid-posterior region, number of segments: 129. The remaining adults measure on average: 32.6, 1.2, 1.29, 1.16 respectively, and have 110 segments. The Prostomium small, epilobic. Setae arranged in four pairs of longitudinal rows. Straight setae, with nodulus, length 0.02 mm. Genital setae absent. Setae ratio in segment 30 aa:ab:bc:cd:dd = 20:1:3:1:28. The saddle-shaped clitellum lies in segments 15–20, ½ 21 (= 6, 6.5 segments) ( Fig. 1A ), with tubercula pubertatis located between segments ½15, 15- ½18, 18 (=3, 4), they have an oval shape with a milky white color, between the lines of setae ab and cd. Male pores in intersegment 16/17, female pores in ½ 14. Nephropores between setae c and d. Two pairs of spermathecal pores were observed in intersegments 8/9, 9/ 10 in line with setae cd.

Internal anatomy. Septa 6/7–10/11 very thick, conical, interpenetrated. Gizzard in segment 6. One pair of extramural calciferous glands with tubular structure (Kompositenschlauchtasche) emerging from region of esophagus of segment 11 and extending to segment 13, glandular part in segments 14 and. Esophagus-intestine transition in segment 15, typhlosole from segment 15. Caeca lacking. Three pairs of lateral hearts in segments 7–9, two pairs of intestinal hearts in segments 10 and 11. Supraesophageal and subneural vessels lacking. One pair of vesicular holonephridia per segment. The two large testis sacs coalesce ventrally in segment 11. The large seminal vesicles in segment 12 continue back to segment 24 ( Fig. 1B ). The male ducts run ventrally along the parietal region to intersegment 16/17. Ovaries in segment 13, female pores in segment 14. Two pairs of spermathecae in segments 9 and 10, heart-shaped, of different size, the second pair larger. The duct thin and separate from the ampulla ( Fig. 1B ).

Remarks. Righiodrilus omagua sp. nov. is a species closely related to Righiodrilus cigges Righi, 1970 (Serra do Navio, Amapá / Brazil), Righiodrilus mairaro Righi, 1982 (Boa Vista, Roraima / Brazil), and Righiodrilus paoletti Righi, 1984 (Parque Nacional El Avila/ Venezuela) because of the presence of clitellum in segments 15–21, two pairs of spermathecae in segments 9 and 10, and pores of the spermathecae in line with the setae cd ( Table 1 ). The following characteristics of the new species allow its differentiation from the others: tubercula pubertatis in segments ½15, 15- ½18, 18; male pores located in intersegment 16/17; large seminal vesicles in segment 12 that continue to the end of segment 24. Distinctive characteristics of the other species are as follows: R. cigges : tubercula pubertatis in segments 17, ½ 17 – 2/3 19, 19; male pores in segments 17/18; pores of the spermathecae in line with the setae b; seminal vesicles in segments 12–18. R. mairaro : tubercula pubertatis in segments 19–1/3 21; male pores in segments 19/20; seminal vesicles between segments 12 to 24 or 36 and, sack-shaped spermathecae in which the duct is indistinguishable from the ampoule. R. paoletti : tubercula pubertatis in segments 17–1/2 19, and position of male pores in 17 ( Table 1 ).

Figures

FIGURE 1. Righiodrilus omagua sp. nov. Holotype. A. External lateral view of anterior body (preserved), showing clitellum in 15–20. B. Internal anatomy of anterior segments, dorsal view. S = Spermathecae of 9, 10; CG = calciferous glands in segments 11, 12; SV= large seminal vesicles in segment 12 extending backwards to segment 24.