Microchaetus quaerus, Plisko, 2003

Plisko, Jadwiga Danuta, 2003, Eleven new South African earthworms (Oligochaeta: Microchaetidae) with new information on some known species, and an inventory of the microchaetids of KwaZulu-Natal, African Invertebrates 44 (2), pp. 279-325 : 286-288

Microchaetus quaerus sp.n.

( Fig. 6 )

Etymology: L quaero = seek to learn. Refers to the unusual conjunction of internal characters noted in this species.

Material examined: KwaZulu­Natal: Holotype NMSA /Olig.03659 Hluhluwe Game Reserve, Mbombe Forest (28º03'15"S: 32º03'12"E) at 484 m, forest valley, slightly damp sandy­clay next to water­seep, 30 September 2002, AJA, DG. Paratypes: NMSA / Olig.03664, 2 cl + 1 juv collected with holotype .

Description based on holotype and paratypes.

External characters:

General: body cylindrical. Colour: holotype, clitellate and juvenile paratypes preserved in alcohol for only a few days do not reveal pigmentation; grey­pinkish dorsally and ventrally. Dimensions: holotype preserved, slightly contracted, 104 mm long, 6 mm wide at 10, 8 mm wide at tubercula pubertatis; clitellate paratype 94 mm long, 6 mm wide at 10, 7 mm at clitellum; juvenile paratype 42 mm long, 3 mm wide. Segment number: holotype 180, clitellate paratype 170. Prostomium: prolobous, small, retracted into buccal cavity. Segmentation: secondary annulation present on preclitellar segments; 1 and 2 short, simple, with clear intersegmental furrow 1/2, both with irregular longitudinal grooves; 3 simple; 4–5 with two ringlets similar in size and appearance; 6 with two ringlets, first longer than second; 7–8 subdivided incompletely, 9 only partly demarcated; 10 and following simple, postclitellarly randomly demarcated. Setae: minute; in front of clitellum aa <bc, ab = cd. Nephridial pores: not observed. Female pores: obvious, paired, in 14 above b setae. Male pores: externally not observed; possibly in intersegmental furrow 18/19, as indicated by vasa deferentia entering body wall in segment 18. Spermathecal pores: externally difficult to trace, observed only at one side of one paratype, in intersegmental furrow 8/9; ectal parts of spermathecae were observed during dissection in intersegmental furrows 8/9 and 9/10 respectively.

Clitellar region ( Fig. 6 ): Clitellum: whitish­grey; elongated, clearly segmented; on 11–27, anterior and posterior borders are not clearly marked; anteriorly ventral borders extend to line of papillae located on ab setae; on 19–24 bordering tubercula pubertatis; thin clitellar tissues also cover ventral parts of clitellar segments. Tubercula pubertatis: on holotype and paratypes glandular, segmented, elongated strips, on 19–24; ventrally extending to ab setae. Papillae: prominent, glandular, encircling ab setae on 7–10 and 25–27; on 11–18 small globular blisters on ab setae.

Internal characters:

Septa: 4/5 thin, 5/6–6/7 slightly thicker than anterior; 7/8 and 8/9 thin. Gizzard: cylindrical, large, muscular, in 7. Calciferous glands: in 10, large, with only slightly marked separation dorsally; ventral separation little wider, although not apparent. Intestine: commences in 13; 10 pairs of yellowish, prominent, twice­folded dorso­lateral intestinal folds in segments 23–32. Typhlosole: commences in 17 as thin, flat tube; enlarging backwards changes into large U­shaped. In paratype terminates in segment 75. Dorsal blood vessel: 4–8 double, separated; 9 double, close, cordiform. Paired dorsoventral vessels: 4–8 enlarged vessels; 9–11 much enlarged, moniliform. Nephridia: meganephridia ; little coiled loops with extended, ribbon­like caeca. Spermiductal funnels: holandric arrangement; two pairs, free, in 10 and 11 respectively. Vasa deferentia : commencing on lateral sides of spermiductal funnels in 10 and 11 respectively, extend and run to segment 18; penetrations into body wall occur probably at intersegmental furrow 18/19, but it was not confirmed. Seminal vesicles: two pairs of large sacs commencing at septa 10/11 and 11/12 respectively. Spermathecae: small, elongated thecae in 8 and 9; 2–4 at each side, with ectal parts in intersegmental furrows 8/9 and 9/10 respectively. Ovaries: not observed. Genital glands: glandular tissues in 19–24 associated with tubercula pubertatis.

Biological notes: Hluhluwe Game Reserve, situated between altitudes of 80–540 m, has lower­lying valleys and high ridges. It comprises coastal scarp forest with various thickets of mixed scrub, woodland, grasses and riparian vegetation. The species was found in moist sandy­clay soil in a higher, forested part, near seeping water. Mature individuals together with juveniles collected at the beginning of spring suggest sexual activity during a relatively mild winter. Associated with Proandricus beddardi . Acanthodrilidae were found nearby.

Distribution: Known only from the type locality ( Fig. 1 ).

Discussion: Distinctive in having spermiductal pores in intersegmental furrows 8/9 and 9/10. Spermiductal pores in intersegmental furrow 8/9 do not occur in any other known microchaetid species. In Microchaetus the most anterior position of spermathecal pores was observed in namaensis (known only from the Northern Cape) whose anterior pores are in 9/10 and the other two rows of pores occur in intersegmental furrows 10/11 and 11/12 respectively. In the holandric genera Tritogenia and Michalakus the most anterior position of spermathecal pores is in intersegmental furrows 10/11 and 11/12 ( Tritogenia shawi and T. soleata ), and in Michalakus initus in 10/11, 11/12, 12/13. In some proandric species of the lesothoensis species­group the utmost anterior spermathecal pores occur in 9/10, or between ringlets in segment 9 ( Proandricus amphius sp. n. and P. oresbiosus sp. n.). M. quaerus differs from congeners in the shape and positions of clitellum, tubercula pubertatis, and thickness of preclitellar septa.

Figures

Fig. 6. Microchaetus quaerus sp. n., holotype, ventral view with tubercula pubertatis and papillae. [P = papilla, T = tuberculum pubertatis].

Fig. 1. The distribution of species of Microchaetus and Michalakus in KZN. Microchaetus: 1 = ambitus; 2 = caementerii; 3 = distasmosus; 4 = griphus; 5 = herberti; 6 = idechoritus; 7 = mkuzi; 8 = natalensis; 9 = papillatus; 10 = parvus; 11 = pondoanus; 12 = quaerus; 13 = tuberosus; 14 = vernoni; 15 = zaloumisi; 16 = Michalakus initus.