Ramiellona microscolecina, Fragoso, Carlos & Rojas, Patricia, 2014

Fragoso, Carlos & Rojas, Patricia, 2014, New species and records of the earthworm genus Ramiellona (Annelida, Oligochaeta, Acanthodrilidae) from southern Mexico and Guatemala, Zootaxa 3753 (6), pp. 549-572 : 556-559

Ramiellona microscolecina sp. nov.

Figures 5 , 6

Localities. Mexico. (1) Type locality: Chiapas, Chajul, 3 km southwest of town, in sandy soils of a small island, margins of the Lacantun river. Riparian vegetation, within soil at 0–20 cm depth. 16°06’17.22”N, 90°57’06.73”W, 151 m a.s.l.. 3J-1A-10CA (five posterior amputees), 11/15/1981, C. Fragoso and P. Lavelle; 3A-5CA, 12/30/1982, C. Fragoso; 1CA, 01/01/1983, C. Fragoso; 1CA, 02/03/1984, C. Fragoso; 6J, 05/11/1984, C. Fragoso; 7J-2A- 3CA (two posterior amputees), 10/26/1984, J. Ramirez; 1J-1A-9CA (one and three posterior amputees, respectively) and one cocoon, 12/14/1984, C. Fragoso; 2A-1CA (posterior amputee), 12/29/1985, C. Fragoso. (2) Chiapas, Frontera Corozal, at the margins of the Usumacinta river, close to the wharf, riparian vegetation. 16°49′25.36”N, 90°53′11.01″W, 122 m a.s.l.. 1J, 11/02/1991, A. Cartas and J. Bueno. (3) Chiapas, Flor de Cacao, in the region of Marques de Comillas, margins of the Salinas (Chixoy) river, close to the wharf; riparian vegetation. 16°07’28.66”N, 90°26’58.39”W, 129 m a.s.l.. 2A, 10/31/1991, A. Cartas; 7J-1A, 05/21/1992, J. Bueno. (4) Tabasco, Tenosique, Hwy 203, 10 km before town of Tenosique and 1.3 km from Usumacinta river. Pastures of Cynodon plectostachyus over clay soils, within soil at 0–20 cm depth. 17°26’17.1”N, 91°30’17.6”W, 30 m a.s.l.. 3J-1A, 11/13/1981, C. Fragoso and P. Lavelle.

Holotype. One clitellate adult collected in locality 1, 11 /15/1981: IEOL 3356.

Paratypes. Dissected: Five clitellate adults collected in locality 1, 11 /15/1981: IEOL 4252, 4248; 12/30/1982: IEOL 2165; 01/01/1983: IEOL 4244; 12/14/1984: IEOL 4210; one posterior amputee adult from locality 4, IEOL 2171. Further 15 individuals, only externally characterized: Locality 1, 11 /15/1981: IEOL 3701, 2170, 4251, 4246; 12/30/1982: 4245, 2160; 01/01/1983: 2405; 02/03/1984 IEOL 3702; 10/26/1984: IEOL 4215, 3700; 12/14/1984: IEOL 4213, 4212, 4208, 4210; locality 3, 10 /31/1991: IEOL 2166.

Description. External. Length of relaxed specimens 167–230 mm (mean= 209 mm, n=13; holotype 216 mm), contracted 94–152 mm (mean= 126 mm, n=4). Width postclitellar 3.6–5.3 mm (mean=4.3, n=18; holotype 4.7 mm). Segments 169–210 (mean=193, n=15; holotype 201). Pigment absent. Prostomium prolobous. Peristomium with several longitudinal grooves, also present in second and third segment. Secondary annulations in preclitellar segments: one postsetal furrow in 5, 6 and 7; one presetal and one postsetal in segments 8–12 or, less common, two presetal and two postsetal furrows in some of segments 10–12 ( Fig. 5 A); behind clitellum generally absent or one presetal and one postsetal. Setae eight per segment, visible from segments 4–6, closely paired in anterior region and widely paired in posterior region. Setal formula (average, n=8) (aa:ab:bc:cd:dd): 10: 6.1:1:7.8:0.6:34.3 and 0.8 dd= 1/2 U; 30: 4.4:1:3.7:1.2:23 and 0.8 dd= 1/2 U; ten segments before anus: 1.2:1:1:1:4.6 and 1.2 dd =1/2 U. Genital setae absent. Conspicuous and robust paired dimorphic penial setae (a and b) in 17. Seta a 2.1–2.4 mm long before distal curvature, 105–108 µm wide, almost straight in the main axis, slightly curved at base and with a 90° curvature (or stronger) at the distal end ( Fig. 6 A); apex with irregularly distributed thorns, thinner than main axis ( Fig. 6 B); seta b slightly smaller and thicker than seta a, 2.0–2.2 mm long before ental curvature, 122–135 µm wide, also almost straight in the main axis, with a slight curvature at base and a 90° curvature in the spoon-like apex that ends like a hook ( Fig. 6 C); ornamentation limited to the last distal third and characterized by abundant irregular serrations, the apex with scarce and more conspicuous thorns ( Fig. 6 D). Setae a and b of 18 visible in c. 20% of checked material; in two individuals slightly larger than somatic setae.

Clitellum dark orange, 1/n 13, 14–18 (9 ind.), 14–18 (7 ind.), saddle-shaped in 15–18, reaching setae b ( Fig. 5 A); in fully mature individuals borders almost joined mid-ventrally, partially occluding the genital zone; in other individuals furrows and setae cd easily recognized. Large dorsal pores present all along the body, first functional pore in 12/13 (16 ind.); in some individuals a closed pore also present in 11/12. Female pores very small and difficult to observe, in 14, presetal in A or slightly median to A. One pair of prostatic pores in 17 just at the base of seta b; each pore apparently connected to male pores in the equator of 18 by an oblique groove which runs through the clitellum and outside B. Spermathecal pores paired in 8/9 and centered in AB, small or, less common, medium sized. Genital marks mid-ventral and unpaired, as intersegmental ovoidal-rectangular papillae commonly extending in BB (but in some individuals from outside B to outside B) located in 10/11 (present in all individuals except the one from Tabasco) and in 18/19 ( Fig. 5 A); due to the swelling of clitellum and the folding of genital zone, this last mark sometimes appears as paired. Other marks not present in all individuals include smaller midventral ovoid papillae in 11/12, 15/16, 16/17, 17/18, 20/21, 21/22 and swellings in segments 19 and 20; the adult from Tabasco with elliptical and narrow mid-ventral papillae from AB to AB in 11/12, 12/13 and 13/14.

Internal. Septa 5/6, 12/13 and 13/14 very thin and membranous, 11/12 slightly muscular, 6/7–10/11 muscular; septa 6/7–11/12 funnel shaped, imbricated and joined by up to 16 dorsal and lateral connective-muscular tissue fibers arranged in three or four pairs both dorsally and laterally, the latter fixed to walls of the same or posterior segments. One large gizzard in 5, extending 2–3 segments backwards. Extramural calciferous glands absent. The inner wall of the esophagus in 7, 8 and 9 (rarely 10) with developed lamellae which occlude almost half of the lumen; in 10 and 11 (rarely 12) lamellae less developed, larger in the dorsal part and highly innervated in 11; in 12 and 13 esophagus with only small grooves. Intestine begins in 14/15. Intestinal typhlosole starting in 15 or 16, laminar and small, increasing abruptly in size in 22 (3 ind.), 23 (1) or 24 (3) with free edge divided into three deep ridges (trifid), ending abruptly in 146, 148, 150, 152, 153. In the region of segments 23–29 (until 32 in one ind.) typhlosole with lateral folds, dorso-ventrally oriented. Smaller dorso-lateral typhlosoles in the region of segments 22–29, (24–32 in one ind.), at both sides of main typhlosole. Intestinal caeca present as 4–5 pairs of dorsal pouches on the intestine of segments 23–26 (2 ind.), 24–27 (3) or 25–29 (2); some segments with apparently more than two caeca, due to the invasion of posterior caeca.

Single dorsal vessel visible throughout; in the region of segments 15–26 two pairs of lateral commissures per segment dorsally visible. Supra-esophageal vessel visible in 7–12. Lateral hearts in 7, 8, 9 and 10; lateroesophageal hearts in 11 and 12. Ventral vessel present. Segment 6 with two larger latero-ventral vessels originating just at the union of the esophagus to gizzard (5/6) running forward under the gizzard. Paired infra-esophageal vessels in segments 8–12, joining supra-esophageal vessel in 8–11 through lateral esophageal commissures which apparently connect with their respective muscular septa. Extra-parietal ventral vessels on each side of segments 13, 14 and 15, running laterally of male gonoduct; those of 13 running towards lateral walls, then turning to the septum where each of them divides into two small branches; one of them entering the septum, the other one continuing to the posterior segment. Paired clusters of tufted microphridia in the ventral wall of segments 3–5. In 8–13 between 6 and 12 septal nephridia observed on the anterior face of the corresponding septa, present on both sides of the esophagus, oriented in dorsal-ventral direction. Parietal, closed meronephridia extending backwards from 13 (1 ind.) or 14 (3), 6–10 meronephridia per segment (3–5 on each side). The mid-ventral nephridium of last segments larger and with a small nephrostome in the preceding segment.

Holandric. Testes of 10 and 11 bushy and joined to male funnels by abundant coagulum, located mid-ventrally on the anterior face of the corresponding septum. Male funnels iridescent and plicated, placed at both sides of midventral line of the posterior face of septum; testes and male funnels in 11 larger than those in 10. Male gonoducts double from segment 11, running along body wall of segments 12–16 between B and C, muscular from segments 14, 15; disappearing in 16 under penial retractor muscles, entering body wall in 17 where they turn towards B, and opening in the equator of 18. Two pairs of acinous seminal vesicles in 9 and 12, respectively fixed to septa 9/10 and 11/12; the anterior pair smaller than the posterior one which covers most of the esophagus. One pair of tubular prostates in 17, strongly coiled, fixed to intestine and septa by connective tissue, extending 2–5 segments backwards; the glandular part 2–3 times wider and 4–5 times longer than the muscular duct. Follicles of penial setae a and b joined and forming a muscle pouch; on its free side, this pouch fixed by one muscular stripe to the lateral wall of 17; its base fixed by 2–3 fibers to the mid-ventral line of 16/17. Undeveloped extra setae (two per follicle) present.

One pair of medium-sized bushy ovaries on the floor of 13, at both sides of mid-ventral line, with numerous eggs in rows; female funnels one pair in 13; no ovisacs present. One pair of similar-sized spermathecae discharging in 8/9, ampulla and duct in segment 9, diverticle in 8, sessile, discoidal and attached to the ventral body wall, with several dozens of small seminal chambers ( Fig. 5 B); duct wider and shorter than elongate ampulla ( Fig. 5 C); ampulla often twisted in its medial region. Dimensions (n=2): 4.5, 4.9 mm length, 2, 2.4 mm width.

Etymology. The name of the species is related to the loss of the anterior spermathecae and the last prostatesthe microscolecin condition.

Remarks. Ramiellona microscolecina sp. nov. is unique in the genus by the microscolecin condition. It also belongs to the group of holandric species with last hearts in 12 and with the spermathecae characterized by a discoidal cabbage shape-like diverticle situated in the segment anterior to that of the ampulla ( R. strigosa , R. eiseni and R. tojolabana sp. nov.). This new species is very similar to R. strigosa setosa (see below), but differs in the different number of spermathecae and prostates. This species has previously been referred to as " Ramiellona sp. nov. 1" ( Fragoso & Lavelle 1987, Fragoso 1992), " Ramiellona sp. nov. 27" ( Fragoso 1993), " Ramiellona sp. nov. 12" ( Fragoso 2001), and " Ramiellona sp. nov. 14" (Fragoso 2007; Fragoso & Brown 2007).

Figures

FIGURE 5. Ramiellona microscolecina sp. nov. A. Ventral view of anterior region (paratype IEOL 3701). B. Right side spermatheca, dorsal view. C. Right side spermatheca, ventral view. Holotype IEOL 3356. Scale 1 mm.

FIGURE 6. Ramiellona microscolecina sp. nov. Penial seta from right side of segment 17. SEM photographs. A. Seta a (scale 200 µ). B. Apex ornamentation of seta a (scale 50 µm). C. Seta b (scale 200 µm). D. Apex ornamentation of seta b (scale 20 µm). Paratype IEOL 4251.