Rhinodrilus antonioi, Hernández-García & Sousa, 2020

Sousa, Sandriel Costa, Sousa, Anny Mykaelly De, Hernández-García, Luis Manuel, Gualter, Regia Maria Reis & Rousseau, Guillaume Xavier, 2020, A new earthworm species of the genus Rhinodrilus (Rhinodrilidae, Clitellata) and new records of earthworms species from the Amazon-Cerrado-Caatinga transition in the State of Maranhão, Brazil, Zootaxa 4810 (1), pp. 169-174 : 171

Rhinodrilus antonioi, Hernández-García & Sousa , sp. nov.

( Figure 2 )

Holotype. MPEG001623 , adult, complete, old secondary Cerrado , Santa Tereza Village, Caxias, Maranhão, Brazil, 4°53’28.60”S, 43°25’33.27”W, 108 masl, 22 February 2019, Sousa, S.C, Sousa, A.M & Hernández-García, L.M colls.

Paratypes. MPEG001624 , MPEG001625 , MPEG001626 , MPEG001627 , MPEG001628 two adults and three amputee, same data as for Holotype .

Etymology. The species name is in honor of Manoel Antonio de Sousa, the owner of the area where the new species was found.

Description. Dimensions: holotype 54 mm by 3.5 mm at X, 5.0 mm at clitellum, 3.8 mm at XXX, 310 segments; paratypes 68–96 mm by 4.0– 4.2 mm at X, 4.8–5.3 mm at clitellum and 3.8–4.1 mm at XXX, 245–305 segments. Body cylindrical, dorsally pigmented to B line, dark brownish preserved, similar to code 7.5RP 3/10 of the Munsell table ( Munsell 1975), ventrally apigmented; intensity of pigmentation reduces when fixed in alcohol 99%. Segments I and II grooved. Setae AB and CD commence on III, closely paired-type, regular arranged to clitellum, then B and C became irregular, quincunx at tail. Setal arrangement aa:ab:bc:cd:dd = 1.3:1.0:2.6:0.12:5.3 at X, aa: ab:bc:cd:dd = 5.3:1.0:8.0:0.6:23.0 at XXX, dd>1/2 circumference throughout. Prostomium prolobic. Clitellum in XIV–XXVII, annular in XIV–XX and XXVI–XXVII, saddle-shaped to B line in XXI–XXV; dorsally milky white color preserved; ventrally pigmented to B line in XVIII–XXVII, similar to the code 7.5RP 3/16 of the Munsell table ( Munsell 1975). Tubercula pubertatis ( Fig. 2A ) band-shaped in XXI–XXV limited to BC line; dark red pigmentation. Two specimens with tubercula pubertatis milky white in color, similar color is found in paratypes. Genital setae in XXII–XXIV, in the center of rounded gential papillae on AB line. Genital setae of segment XXIII straight, 1750 μm in length, twelve alternate semilunar excavation at the subapical concave part ( Fig. 2B ). Common setae of segment XXX smooth and sigmoidal, 625 μm in length ( Fig. 2C ). Female pores microscopical, laterally to B line in XIV, on a small globular papilla, similar in color as clitellum. Microscopic male pores in 22/ 23 in line B. Sphincteric intersegmental nephridiopores in CD line, first nephridiopores visible in XIV–XV.

Septa equally thick, conical and highly muscular in 6/7–8/9. Septa 9/10–11/12 slightly muscular, intraclitellar septa membranous. Gizzard in VI, 2.3 mm in width by 2.6 mm in length, highly muscular. Intestine origin in XVIII. Sigmoidal typhlosole at XXVI extended to CCXL, occupying approximately 10%–15% of the intestinal space. Three pairs of calciferous glands, lobulated-shaped, in VII–IX; 1.5 mm in width by 1.3 mm in length, the glands are fragile, oriented dorsal-esophageal ( Fig. 2D ), and with tubular-composite structure ( Fig. 2E ). Holonephridial system, postclitellar nephridia with a small nephrostome connected to the bladder by a tube folded into two loops. Blood vessel in VII–IX. Two pairs of lateroesophageal hearts, kidney-shaped, in X–XI. A medium-developed supraesophageal vessel runs over the intestine.

One pair of ovary sacs in XIII. Female pores open in segment XIV near the B line. Three pairs of spermathecae with lobulated-shaped and seminal chambers in VI–VIII. Spermathecal pores open in 6/7, 7/8, 8/9, C line, spermathecal duct as wide as ampulla, the duct measures 0.5 mm in width and 0.3 mm in length, the ampulla measures 0.6 mm in width and 0.7 mm in length, diverticula absent ( Fig. 2F ). Two pairs of testes sacs in X and XI. Two pairs of seminal vesicles with lobulated-shaped in XI and XII–XIV. Deferent ducts go out from testes through B line into body wall and open on 22/23 between B lines.

Remarks. The quincunx arrangement of setae near the tail is a character not yet reported for the genus Rhinodrilus . This may be a character unique to Rhinodrilus antonioi sp. nov. However, this character is not known for some species of this genus ( Cordero 1943; Michaelsen 1934; Rosa 1895). In the genus Rhinodrilus , some species have one or more lines of irregular setal in the posterior region of the body: R. corderoi Righi, 1985 ; R. cucho Righi, 1996 ; R. fafner Michaelsen, 1918 ; R. fuenzalidae Cordero, 1944 ; R. hoeflingae Righi, 1980 ; R. pitun Righi & Moraes, 1990 ; R. xeabaibus Righi, 1969 . Within this group, only R. xeabaibus has calciferous glands with a tubular-composite structure, a character shared with the new species. Still within this group, R. pitun is the only species to share the annular and saddle-shaped clitellum with R. antonioi sp. nov. The new species differs from R. xeabaibus by the length (54–96 mm vs. 310 mm), by the extension of the clitellum (XIV–XXVII vs. 1/2XV–XXX), by the shape of the clitellum (annular and saddle-shaped vs. saddle-shaped throughout), by the position of tubercula pubertatis (XXI–XXV vs. 2/3XXIII–2/3XXVIII), by the position of the male pores (22/23 B line vs. 24/25 B line) and the number of spermathecae (three vs. four). R. antonioi sp.nov differs from R. pitun in length [54–96 mm vs. 360 mm (in an amputated specimen Righi & Moraes 1990)], by the extension of the clitellum (XIV–XXVII vs. 1/2XIV–XXIX), position of tubercula pubertatis (XXI–XXV vs. XXII–XXVII, 1/2XXVIII), by the structure of the calciferous glands (tubular-composite vs. tubular-dichotomous) and by the spermathecal pores (6/7–8/9 C line vs. 6/7–8/9 D line).

Figures

FIGURE 2. Rhinodrilus antonioi sp. nov., holotype.A. External ventral view of the anterior body region, with clitellum, tubercula pupertatis, and genital papillae, SP: Spermathecal pores. B. Genital seta on right A line of XXII. C. Common seta on right A line of CCL. D. Cross section of the right calciferous gland of IX. E. Dorsal view of transversal cut of the right calciferous gland of IX. F. Dorsal view of the right spermathecae of VII, SC: Seminal chambers.