Libyodrilus tenuisetus, 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 : 1867-1877

Libyodrilus tenuisetus n. sp.

(figures 5C, 6G, H, 7C, 9F)

Material examined

Type material. Cameroon, ca 2.5 miles S of Ambam , 2 ‡ 23 ’ N, 11 ‡ 17 ’ E, at bank of small stream, 14 January 1966, coll. M. W. Clausen (holotype: one adult, ZMUC OLI-12 ; paratypes: one clitellate, one aclitellate, one juvenile, ZMUC OLI-13 ) .

Additional material. Cameroon; 2.5 miles S of Ambam near frontier to Gabon, muddy soil a few metres from a river inside a forest, deep shade, 14 January 1966, coll. M. W. Clausen (one clitellate, ZMUC OLI-14 ) ; 1.25 miles N of Ambam , sandy clayish loam near small stream, 15 January 1966, coll. M. W. Clausen (one clitellate, ZMUC OLI-15 ) ; ca 4.7 miles S of Ambam, Ambam-Gabon road, close to small, very contaminated stream, 15 January 1966, coll. M. W. Clausen (two clitellates, ZMUC OLI-16 ) .

External characters (figure 7C)

HOLOTYPE: length 104 mm, maximum diameter 3.5 mm (variation 3.0– 3.5 mm), number of segments 204 (only the type was complete). Annulation: segment 8 triannular, 9–14 multi-annulate, 19 tri-annulate, 20–27 multi-annulate, annulation further posteriorly gradually decreasing and finally disappearing. Clitellar segments tetra-annulate if swelling not too developed. Prostomium prolobous. Clitellum brick red, rest of body without pigment. Setae uniform. No normal ventral setae, but penial setae present on segment 17. Setae uniform. Setal formula: aa: ab: bc: cd ~ 6.0:1.2:5.0:1.0, dd ~ two-thirds of body circumference at segment 10; 5.0:1.2:4.0:1.0, dd ~ two-thirds of body circumference at segment 30; aa widening posterior to clitellum, reaching ‘normal’ distance in segment 20. Clitellum annular, with up to five segments in 1/3 14, 14–2/5 18, 18; posterior half of segment 18 less pigmented between setal lines a.

No dorsal pores. Nephridiopores unrecognizable.

Spermarial pore unpaired, in 13 m /v in setal zone. Pore a small transverse slit, about 0.2 mm wide.

Female pores minute openings surrounded by pale narrow edge in 15, about 4 cd dorsal to d just anterior to setal zone.

Male pore unpaired, minute opening m/v in setal zone in 17 in centre of low longitudinally oval swelling extending laterally to b, anteriorly and posteriorly almost to 16/17 and to 17/18, respectively. Slightly less developed in some clitellate specimens.

Internal characters

First septum 4/5. Septa 5/6–11/12 with a thick layer of muscular fibres, 4/5 and 12/13 less muscular, all succeeding septa thin. Pharynx extending posteriorly to 4/5. No oesophageal gizzards, paired calciferous glands or unpaired ventral sacs. Oesophageal wall in 11 and 12 very richly supplied with blood vessels. Intestine beginning in 19. Three intestinal gizzards, one in each of segments 23, 24 and 25. Thin-walled sections of gut anterior to gizzards in each segment, with four pouches, two dorsally and two ventrally, in segments 24 and 25. Median typhlosole present from 19 (except in gizzards), becoming gradually less distinct towards posterior end (in type disappearing at about segment 170). Lateral typhlosoles present in segments 26–36, 38.

Dorsal blood vessel doubled (but united at septal insertions) in 12, 13–19, 21, 22; vessel can be traced to 6. Supra-oesophageal trunk visible in 6–12 (in holotype not visible in 6). Hearts in 6–12. Subneural trunk dividing into two extraoesophageal vessels in 16.

Excretory system holonephric.

Holandric. Testes free, paired in 10 and 11. Funnels paired in 10 and 11, large, with numerous plications and white iridescence. Posterior pair somewhat larger than anterior one. Seminal vesicles paired in 11 and 12, posterior pair larger than anterior one, both confined to the segment. Vasa deferentia disappearing into euprostates about 1 mm from ectal end.

Euprostates tubular, about 3 mm long and 1 mm in diameter, extending back to 19/20, 20/21 or 21/22, sometimes of different lengths in the two sides (in type to 19/ 20 in right side, to 21/ 22 in left). One pair of penial setae, one seta in each sac, just in front of euprostates in 17.

Penial setae (figures 5C, 6G, H) slender, almost straight, with slightly bent tip, about 0.94 mm long with maximum width of 0.02 mm (at base). Surface with irregular, roughly serrated indentations ectally (figure 5C) similar to those shown by Jamieson (1974: pls 6, 9, 12) for species of Cryptodrilus . Growth striation not visible.

Spermarium (figure 9F) consisting of a median dorsal sac with two branches emerging from anterior corners of sac and forming two rings in segment 13, one around nerve cord and one around oesophagus, with short tube between the two rings. Under nerve cord spermarium is in connection with spermarial pore through narrow duct within body wall. Perioesophageal ring continuing dorsally in a 0.5– 1.0-mm-wide tube extending back to septum 16/17. No diverticula behind perioesophageal ring. Ovisacs situated on posterior face of 13/14, connected ventrally with perioesophageal ring by a ca 0.5-mm-long tube. Ovisacs opening into ental part of oviducts, which has overgrown funnel entally. Ducts traversing segment 14 and adhering to anterior face of 14/15, disappearing into body wall in segment 15 at level of female pore (14/15 displaced posteriad). No ovaries observed in adult.

Remarks

Libyodrilus tenuisetus n. sp., together with L. crassisetus n. sp., L. platybrachyoncus n. sp. and L. kamerunensis Michaelsen, 1915 , belongs to spermarial group I (table 1). It is distinguishable from all other members of the group by shape and size of the penial setae (figures 6G, H, A, E, 5B, respectively) and from L. platybrachyonchus and L. kamerunensis also by the shape of the genital swellings (figure 7C, B, D, respectively).

Distribution

Only known from four localities in southern Cameroon. (1) type locality, ca 2.5 miles S of Ambam ; (2) locality near type locality; (3) ca 2.5 miles S of Ambam ; (4) 1.5 miles N of Ambam.

Etymology The name L. tenuisetus refers to the slender penial setae of the species.

Libyodrilus violaceus Beddard, 1891

(figures 5D, 6I, J, 7F, 10C)

Libyodrilus violaceus Beddard, 1891a: 172–176 ; Beddard, 1891b: 539–585, pls 38, 39; Gates, 1961: 579–584; Clausen, 1965: 274–279, pl. 41.

Remarks

Libyodrilus violaceus belongs to spermarial group II (table 1; figure 10C). It differs from all other species of Libyodrilus by the shape of the penial setae (figures 5D, 6I, J). The ventral view is shown in figure 7F.

Regarding similarities to L. mekoensis and L. simsi , see L. simsi .

Distribution

South-western Nigeria. Type locality Kew Gardens, London (Lagos, see Introduction) .