Pontoscolex awa, Sousa & Hernández-García, 2020

Sousa, Sandriel Costa, Hernández-García, Luis Manuel & Rousseau, Guillaume Xavier, 2020, A new species of Pontoscolex earthworm (Rhinodrilidae, Clitellata) from the Gurupi Biological Reserve, along with records of earthworm species from the Amazon region of Maranhão, Brazil, Zootaxa 4801 (1), pp. 105-114 : 106-108

Pontoscolex awa, Sousa & Hernández-García , n. sp.

Holotype. MPEG000411 , adult, complete, Secondary Forest , Rio dos Bois, Bom Jesus das Selvas, Maranhão, Brazil, 4°4’32”S, 46°52’49”W, 141 masl, 24 April 2017, Hernández-García, L.M, Sousa, S.C & Rousseau, G.X. colls.

Paratypes. MPEG000412 , MPEG000413 , MPEG000414 , MPEG000415 , MPEG000416 , five adults, complete, Secondary Forest , Rio dos Bois, Bom Jesus das Selvas, Maranhão, Brazil, 4°4’50”S, 46°52’39”W, 149 masl, 24 April 2017, Hernández-García, L.M, Sousa, S.C & Rousseau, G.X. colls .

Etymology. The species name is in honor of the Awa indigenous people, the last hunter-gatherers of the continent, and who live in the forest of the region.

Description. Dimensions: holotype 66 mm by 4.1 mm at X, 4.2 mm at clitellum, 3.9 mm at XXX, 219 segments; paratypes 53–66 mm by 3.6–4.1 mm at X, 3.7–4.2 mm at clitellum and 3.5–3.9 mm at XXX, 218–219 segments. Body cylindrical and apigmented. Setae AB and CD commence on II, regular and closely paired throughout. Setal arrangement aa:ab:bc:cd:dd = 3.6:1.0:5.6:1.0:15.2 at XXX, dd>1/2 circumference throughout. Prostomium prolobic; peristomium grooved. Clitellum in XIII–XXIII, annular in XIII–XVIII, saddle-shaped in XIX–XXIII, dark beige preserved. Tubercula pubertatis band-shaped on XIX–(1/2) XXII in BC line (Fig. 1A). Four pairs of genital markings are ventrally between the tubercula pubertatis field protruding along the segment. Smooth genital setae (Fig. 1B) in XIX–XXI at AB line, 350 μ m in length, slightly curved at distal region, thickness near the apical region. Common setae smooth and slightly curve at the apical region, 250 μ m in length (Fig. 1C). Microscopical ovipores just on A line on oval light beige papilla of segment XIV, 0.25 mm apart. Male pores microscopical and not recognized externally. Vesicled intersegmental nephropores in D line, first nephropore visible in XIII–XIV.

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, 2.2 mm in wide and 1.9 mm in length, highly muscular, 0.5 mm in thickness. Intestinal origin in XVII, sigmoidal typhlosole at XXVII extended to CXLIX, occupying approximately 70% of the intestinal space. Three pairs of pyriform calciferous glands with small rounded appendage in VII–IX (Fig. 1D), dorsal-esophageal connection and tubular-composite structure (Fig. 1E). Vesiculated holonephridia; ducts to body wall near the level of D. Post-clitellar nephridia consisting of a tube arranged in two loops and connected with the bladder compartment (Fig. 1F). The vascular system with three pairs of blood vessel in VII–IX, parallel to calciferous gland, two pairs of lateroesophageal hearts, kidney-shaped, in X–XI. A poorly developed supra-esophageal vessel runs over the dorsal side of the intestine, supra-esophageal hearts are absent.

One pair of ovary sacs in XIII. The ovary funnels are backside of the segment XIII just on membranous septa. Female pores open in segment XIV between A lines space. Three pairs of lobulated and very small spermathecae are present in VII–IX, opening pairwise C line of 6/7, 7/8 and 8/9, respectively (Fig. 1G). Spermathecae increasing in size, from 0.2 mm in VII to 0.8 mm in IX. The spermathecal duct is as long as the ampulla. Although the spermathecae are very small, they have a bulky ampulla, with sperm seen in the three pairs, indicating that they are functional. Male sexual system metandric, testes sacs in XI; a pair of large seminal vesicles in XII extended to segment XXX–XLV. Deferent ducts go out from testes and enter into body tissue on XII near B line and then running to 20/21, opening into tubercula pubertatis.

FIGURE.1. Pontoscolex awa n. sp. A. Ventral view of anterior region. B. Right genital seta of XIX at A line. C. Right common setae of XXX at B line. D. View in cross section of left calciferous gland of VII. E. Dorsal view of transversal cut of left calciferous gland of VII. F. Dorsal view of post-clitellar nephridium. G. Dorsal view of right spermathecae of VII–IX.

Remarks. Smooth genital setae not larger than the common setae is a character not yet reported in species of Pontoscolex . It may be unique to P. awa sp. nov. but it is unknown in several species of the genus (see Table 1). Pontoscolex awa sp. nov. has a regular setal arrangement, a character state shared by 10 further species in the genus: P. eudoxiae Righi et al., 1978 ; P. franzi Zicsi & Csuzdi, 1999 ; P. maracaensis Righi, 1984 ; P. nogueirai Righi, 1984 ; P. pydanieli Righi, 1988 ; P. spiralis Borges & Moreno, 1990 , P. guianicus Černosvitov, 1934 ; P. hoogmoedi Righi, 1969 ; P. longissimus Černosvitov, 1934 ; P. roraimensis Righi, 1984 . Of these, the latter four species have tubercula pubertatis extending to XXVI, XXVII or XVIII, i.e. far beyond XXIII as in the new species. These four species are traditionally accomodated in the subgenus Meroscolex ( Righi 1984) . The remaining six species are traditionally accomodated in the subgenus Pontoscolex , on behalf of the posterior extension of the tubercula pubertatis to XXII or XXIII ( Righi 1984), a character that also applies to P. awa sp. nov. These six species are distinguished from P. awa sp. nov. by the posterior extension of the clitellum to XXIV, XXV, or XXVI ( Table 1), more posterior than in P. awa (XXIII). Other differences are as follows: P. pygdanieli is much larger (length up to 580 mm, up to 745 segments, vs. 53–66 mm, 219 segments); genital setae in P. eudoxiae are up to 0.7 mm long and ornamented (vs. 0.35 mm and smooth); in P. maracaensis , the seminal vesicles extend to XXVI and the male pore is on XXI (vs. XXX–XLV, on 20/21); in P. nogueirai , seminal vesicles are absent and the tubercula pubertatis extend from 1/2XX to 1/2XXIII (vs. XIX–1/2XXII); furthermore, the species is larger (length 93–145mm, up to 302 segments); in P. spiralis , the clitellum is saddle-shaped (vs. annular in the anterior part) and the seminal vesicles extend to XXIII; P. franzi is also larger (length 92–120 mm), the citellum is annular (vs. saddle-shaped in the posterior part), and the tubercula pubertatis begin in segment XX (vs. XIX). Table 1 gives an overview of taxonomically useful characters in species of Pontoscolex .

Pontoscolex is currently subdivided into three subgenera, Pontoscolex (17 species), Meroscolex (4 species) and Mesoscolex . (1 species). Subgenus Pontoscolex is distinguished from the other two by the anterior location of the tubercula pubertatis from XIX–XXI on (vs. from XXIV in Meroscolex and XXVI in Mesoscolex ) and by the location of the male pores in 19/20–XXII (vs. XXIV and XXVIII, respectively) ( Borges 1992). Further characters used previously to distinguish the taxa ( Černosvitov 1935; Righi 1984) had to be discarded because of non-exclusivity. For example, all species of Pontoscolex (Meroscolex) have posterior setae in regular rows, but the same applies to some species of P. ( Pontoscolex ) (see above). On the other hand, the conspicuous quincunx arrangement of posterior setae is found in subgenus P. ( Pontoscolex ), but P. ( Mesoscolex ) also has irregular arrangement of posterior setae (comp. Moreno 2004). As mentioned above, P. awa sp. nov., although with regular setae, fits perfectly in Pontoscolex (Pontoscolex) .