Microchaetidae Beddard, 1895

Plisko, Jadwiga Danuta, 2013, A new family Tritogeniidae for the genera Tritogenia and Michalakus, earlier accredited to the composite Microchaetidae (Annelida: Oligochaeta), African Invertebrates 54 (1), pp. 69-69 : 85-86

Family Microchaetidae Beddard, 1895 (s.str.)

Figs 12–14

Type genus: Microchaetus Rapp, 1849 .

Diagnosis: Body elongated, mature earthworms usually longer than 100 mm (few species slightly shorter, 60–100 mm), often much longer. Number of segments usually more than 100. Holandric (male funnels in 10 and 11) or proandric (male funnels in 10) or metandric (male funnels in 11), enclosed or free. Excretory system holoic; one pair of nephridia per segment (except for three anterior segments); large or medium-sized, tightly coiled loops with elongated nephridial bladders, V-shaped or J-shaped at the ectal end. One oesophageal gizzard in segment 7. Dorsal blood vessel undivided, simple along the whole length, or double anteriorly in 4–9 but simple when crossing septa, and simple posterior to segment 10. Two, three or four anterior septa: 4/5, 5/6, 7/8 and 8/9, which may be variably thickened. One or two seminal vesicles located in one or two segments: 9, or 9 and 10, or 10 and 11, or extended posteriorly through a variable number of segments, sometimes twisting forwards. Spermathecae variably shaped: ampulae, elongated tubes, bent, serpentine or tightly coiled loops; small or much enlarged; paired or multiple; with pores pretestical, testical, or post-testical; in one to six intersegmental furrows: 9/10–15/16, 16/17. Setae: eight per segment, paired, variably sized; in some species convergent in a few preclitellar segments, diverging postclitellarly.

Description: Live elongated ( Figs 12 , 13 ), usually firm; preserved ( Fig. 14 ) slightly stretched or contracted, although not compact. Pigmented or not, variably coloured (with violetish, greyish, greenish, whitish or pinkish grey tint). Body length 60–2600 mm. Number of segments 80–1200. Preclitellar segments variably annulated: 1–3 usually simple, 4–9 ringleted and annulated with 2–4 annuli; external segmental subdivision (annulation) characteristic for species. Female pores on 14, variable in position. Male pores occur variably (species character): pre-clitellarly as from 14/15 intersegmental furrow, clitellarly at tubercula pubertatis. Clitellum saddle-shaped or slightly extended ventrally. Papillae present; variably sized and shaped, usually in line with the ventral setae on some of the preclitellar segments, occasionally extending beyond clitellum on a few segments. Calciferous glands variably shaped, stalked or not, in segment 9, or 9–10, or 10. Genital glands variably shaped and sized, found in various segments.

Composition: Microchaetus Rapp, 1849 ; Geogenia Kinberg, 1867 ; Proandricus Plisko, 1992 and Kazimierzus Plisko, 2006 .

Distribution: Although the southern part of the African continent has been poorly investigated in that a large part of it has not yet been searched for earthworms, it can nevertheless be stated that representatives of this family occur widely, wherever ecological and climatic conditions permit. They are known from the northern part of the RSA, including the vicinity of the Limpopo River, extending to the southern edge of the continent and appearing in all provinces. Microchaetidae are also present in Lesotho and Swaziland, and are likewise expected to occur in the neighboring countries of Botswana, Zimbabwe, and Mozambique. The majority of species have been found at sea level alongside the Indian and Atlantic oceans, and in the Drakensberg mountains, some-times at high altitudes. The earthworms live in various biotopes, but their occurrence depends on the soil characteristics, water content, and the climatic conditions. It may, furthermore, be concluded that presently known genera occur in separate territories which, however, overlap slightly (see the generic distributional information published in Plisko 2012). Kazimierzus appears in the western part of South Africa along the Atlantic border, although overlapping with Microchaetus in the south-eastern part of the Western Cape. Geogenia occurs along the Indian Ocean coast, extending to the Drakensberg range; in the south of the RSA, it overlaps with Microchaetus , and in the northern areas it co-occurs with Proandricus . The genus Proandricus has species that are evidently undergoing morphological changes. In a number of localities, it occurs together with Geogenia , which often demonstrates some similarity to proandric species. It should be said that species of Tritogeniidae , although occurring partly in the Geogenia / Proandricus distributional area, usually inhabit environmentally different sites.

Figures

Fig. 12. Microchaetus papillatus Benham, 1892, live juvenile specimen. (Photo by A. Armstrong)

Fig. 13. Kazimierzus sp., live specimen. Scale bar = 1 cm. (Photo by S. James)

Fig. 14. Microchaetus vernoni Plisko, 1992, paratype, entire length 2.6 m.