Libyodrilus edeaensis, Clausen, 2004

Clausen, Martha Weis, 2004, Description of seven new species of Libyodrilus Beddard from Cameroon, with a key to the species of the genus (Oligochaeta: Eudrilidae), Journal of Natural History 38 (15), pp. 1851-1880 : 1859-1862

Libyodrilus edeaensis n. sp.

(figures 3A, B, 8E, 11D, E)

Material examined

Type material. Cameroon, 12 miles S of Edea, 3 ‡ 47 ’ N, 10 ‡ 13 ’ E, yellow sandy soil at edge of small stream, Lower Lyon Basin , 9 January 1966, coll. M. W. Clausen (holotype: one clitellate, ZMUC OLI-3 ) .

Additional material. Cameroon: near above-mentioned locality, dark, moist, porous loam, 9 January 1966, coll. M. W. Clausen (one clitellate, ZMUC OLI-4 ). Specimen badly damaged (first 15 segments missing), but it was possible to make sections of euprostate and bundles of muscles connected with penial setae [ MWC slide no. 1887, sections 1–12] .

External characters (figure 8E)

HOLOTYPE: length 112 mm, maximum diameter 4 mm, 163 segments. No secondary furrows. Prostomium prolobous. Clitellum brownish red, rest of body without pigment (fixed specimens). Setae closely paired and uniform. Setal formula: aa: ab: bc: cd ~ 6:1:5.5:1, dd ~ two-thirds of body circumference at segment 10; 5.5:1:5.5:1, dd ~ two-thirds of body circumference at segment 30. Clitellum annular, with up to 3 2/3 segments in 1/3 14–17, 1/3 18, replaced by genital swelling ventrally in segment 17 (see below). Clitellar tissue of segment 1/2 14 to about 1/2 17 more pigmented than remaining part.

No dorsal pores. Nephridiopores not discernible.

Spermarial pore minute, unpaired, circular opening m/v in segment 13 in setal zone, surrounded by circular area of glandular tissue ca 1 mm in diameter and 0.3 mm high.

Female pores paired, small, circular openings dorsal to d in 15 just behind setal zone, distance from d about 1 6 cd.

Male pore unpaired, m/v in 17 in setal zone or just in front of setal zone (setal zone is difficult to determine due to swelling mentioned below), in small round depression on cone-like protrusion between setal lines b; protrusion situated on circular swelling reaching 16/17 and setal zone of 18 between b and c. Penial setal sacs opening in depression in front of male pore.

Internal characters

Septa 4/5–10/11 with thick muscular layer, septum 11/12 less muscular. All succeeding septa thin.

Pharynx extending back to septum 4/5. Oesophageal gizzards, ventral oesophageal sacs and paired calciferous glands absent. Wall of oesophagus in segments 11 and 12 very richly supplied with blood from branches of supra-oesophageal vessel. Intestine beginning in 19. Three intestinal gizzards, one in each of segments 23, 24 and 25. Thin-walled sections with four pouches (two dorsally and two ventrally) anterior to gizzards. Median typhlosole clearly visible from segment 26, becoming gradually less distinct towards segment 120. Lateral typhlosoles present in segments 26–35.

Dorsal blood vessel traceable to posterior face of 5/6, bifurcating segmentally, but reuniting where passing through septa in segments 13–22. Supra-oesophageal vessel visible in 6–12. Hearts in 6–12. Subneural vessel dividing into two extraoesophageal vessels in 16.

Excretory systems holonephric.

Holandric. Testes free, paired in 10 and 11. One pair of male funnels with numerous plications and white iridescence in 10 and 11. Both pairs well developed. Vasa deferentia of right and left sides joining (but not fusing) just in front of septum 12/13 and continuing posteriorly to euprostates, disappearing into their muscular layer on lateral side ca one-third length of euprostates from ectal end. One pair of seminal vesicles in 11 and 12.

Euprostates (figure 3A) almost cylindrical, slightly twisted organs, ca 5 mm long and with maximum width of about 1.1 mm. Left euprostate extending back to 22/23, right to 21/22. Euprostates narrowing gradually before disappearing into body wall, joining just before entering male pore. Close to ectal end of euprostates, muscles arranged in small boat-shaped bundles (resemble cauliflower when seen from above), completely hiding tiny penial setae (figure 3A). In dissection the muscles resemble glands, but sections reveal their muscular structure. Partly hidden by the muscle ‘boats’ is a hood-like evagination of muscular and peritoneal part of body wall, hiding ectal end of euprostates. From lateral ends of evagination, bands of muscles extend to lateral sides of euprostates near the evagination.

Penial setae (figure 3B) slender, cylindrical, slightly curved, ca 1.1 mm long, maximum width 0.3 mm (at base). Ectal end of setae gently tapering and ornamented with minute teeth arranged in a spiral. Figure 3B is an old photograph and not very good; the growth striation is not clearly visible. The seta is lost.

Spermarium (figure 11D, E) consisting of a median dorsal tube-like sac with two branches emerging from anterior corners of sac and forming two rings in segment 13, one around oesophagus and one around nerve cord. Under nerve cord, spermarium connecting with spermarial pore through narrow duct in body wall. Dorsally spermarium extending posteriorly as twisted tube to septum 16/17. From dorsal tube two pairs of diverticula, one in 14 and one in 15, surrounding oesophagus and forming meshwork ventrally with connection to ventral part of perioesophageal ring. Receptacula ovorum situated on posterior face of septum 13/14, opening into ental part of oviducts in segment 13. Each oviduct overgrowing funnel in 13, penetrating 13/14, and traversing 14, adhering to anterior face of 14/15 ventrally and mediad, and disappearing into body wall at setal level of female pore in 15. Receptaculum ovorum overgrown by a ventral branch from first diverticulum and thus in connection with perioesophageal ring. No ovaries observed.

Remarks

Libyodrilus edeaensis n. sp. is distinguishable from all other species of the genus by the shape of the swelling around the male pore (figure 8E), by the muscles around the ectal end of the euprostates and by the shape and ornamentation of the penial setae (figure 3A, B). Libyodrilus edeaensis belongs to spermarial group IV (table 1).

Distribution Only known from the type locality in southern Cameroon, 12 miles S of Edea.

Etymology The species L. edeaensis is named after the type locality.

Libyodilus kamerunensis Michaelsen, 1915

(figures 5B, 7D, 9E)

Libyodrilus kamerunensis Michaelsen, 1915: 228–231 , text-figure 7, pl. 18; figures 65, 66; Gates, 1961: 584–585.

Remarks

Libyodrilus kamerunensis belongs to spermarial group I (table 1; figure 9E). It differs from all other species of Libyodrilus by the shape of the genital field (figure 7D) and penial setae (figure 5B).

Gates (1961: 585) wrote: ‘One of the differences from violaceus , according to Michaelsen, 1915, is presence of a terminal spine at ectal end of the penial setae. However, penisetal tips of mature earthworms often are eroded, truncate or otherwise damaged’. Comparison of a seta (figure 5B) from one of the syntypes from the Michaelsen collection in Hamburg (no type was designated) with figures of a seta of Libyodrilus violaceus from Share, Nigeria (this paper, figures 5D, 6I, J; collection in ZMUC) shows that there are differences between the two other than the tip. A long groove is clearly visible in the seta of L. violaceus . Figure 67, pl. 18 in Michaelsen (1915) shows at least the anterior part of the groove.

Distribution

Only known from the type locality Mt N’Kolumbembe , 2 ‡ 25 ’ N, 10 ‡ 12 ’ E, Cameroon .

Figures

FIG. 3. Libyodrilus edeaensis n. sp. (A) Euprostates; (B) penial seta (not to scale). eupr, euprostate; h ev, hood-like evagination; m, muscle; mb, muscle bands; ps, sac of penial seta; v d, vas deferens.