Microchaetus Rapp, 1849

Jadwiga Danuta Plisko, 2006, A systematic reassessment of the genus Microchaetus Rapp, 1849: its amended definition, reinstatement of Geogenia Kinberg, 1867, and erection of a new genus Kazimierzus (Oligochaeta: Microchaetidae), African Invertebrates 47 (1), pp. 31-56 : 35-37

Genus Microchaetus Rapp, 1849 , emend.

Microchaetus: Rapp 1849: 143 ; Michaelsen 1900: 447; 1907: 5; 1913 a: 538; 1913 b: 306; 1913 c: 422; 1918: 306; 1928: 107 [in all papers partim]; Stephenson 1930: 900 [partim]; Brinkhurst & Jamieson 1971: 739 [partim]; Pickford 1975: 23 [partim]; Reynolds & Cook 1976: 56 [partim]; Plisko 1991 b: 293; 1999: 269; [in the following papers partim]: 1991 a: 286; 1992: 338; 1993 b: 222; 1995 b: 45; 1998: 250; 2002: 205; 2003: 281; 2005:105; 2006: 30–32.

Lumbricus: Rapp 1849: 142 ; Perrier 1881: 239; Beddard 1884: 570; 1886 a: 63; Reynolds & Cook 1976: 136 [for Microchaetus microchaetus ].

Anteus: Perrier 1872: 49 [for microchaetus ].

Antaeus: Vaillant 1890: 183 [invalid emendation of Anteus ].

Microchaeta: Perrier 1881: 239 [invalid emendation of Microchaetus ]; Beddard 1886 a: 63; 1895: 667 [partim]; Benham 1886 a: 63; 1886 b: 306; 1892: 141; Horst 1891: 77; Rosa 1891: 380; Michaelsen 1891: 207.

Microchaeta ?: Vaillant 1890: 185.

Rappia: Vaillant 1890: 186 [for Microchaeta ]; Reynolds & Cook 1976: 60.

Type species: Lumbricus microchaetus Rapp, 1849 , by monotypy.

Diagnosis: Testes and male funnels in holandric arrangement. Excretory system holonephric with nephridial holoic bladders V-shaped. One oesophageal gizzard in segment 7. Dorsal blood vessel double in 4–9, being partly or fully separated when passing segments, but simple when crossing septa; in segment 8 broadly parted, in 9 enlarged, constituting ‘cordiform’ organ; posterior to septum 9/10 simple. Calciferous glands not stalked; encircling oesophagous with vestigial dorsal and ventral grooves, in one or two segments: 10, or 9–10, or 10–11. Spermathecae in post-testicular segments; multiple per segment. Spermathecal pores in four (occasionally in three), or five intersegmental furrows, with all pores always behind both pairs of testes. Four septa 4/5, 6/7, 7/8, 8/9 thickened variably, although firmly. Clitellum and tubercula pubertatis extended on numerous segments.

Body length extending to nearly or over 1 meter, sometimes more than 2 meters. Corresponding with large body length, a large number of segments present, average over 500, sometimes more than 1200 segments.

Comments: The species now classified in Microchaetus (s. str.) are characterised by a cluster of features warranting their separation from other microchaetids that were previously considered congeneric. These characters are: clitellum and tubercula pubertatis extended on numerous segments; four septa (4/5, 5/6, 7/8, 8/9) muscularly thickened; multiple spermathecae and spermathecal pores in four or five post-testicular segments; extreme body length; large segment number. However, it is noteworthy that the number of spermathecal pores observed in certain populations of some species demonstrates variability. For example, the spermathecae are found in four, or occasionally five furrows in papillatus ; in vernoni , in four or three furrows. Such variability in species known from single specimens still has to be ascertained.

The species of this genus are known from a small number of sites in widely separated areas, spread over the eastern part of Western Cape, Eastern Cape, and the southern part of KwaZulu-Natal. Gaps in observed species distribution could be due to sampling bias. Representatives of these species are large, and live deeply in the soil—their collection is usually possible only where their activities bring them near to the surface. However, no large casts excreted onto the surface, characteristic for the species of this genus, have been recorded from any other sites. It should be noted that the reported occurrence of Microchaetus species in the Cape Peninsula might be erroneous. Similarly, the locality of a single sample of rappi reported by Beddard (1886 b), as ‘Breakwater, Cape Town’, was later, although by an unknown person, corrected on the collectionlabel as ‘Cape of Good Hope’ and so cited by Plisko (1999). Specimens of rappi , decipiens and braunsi collected in the districts of Avontuur, Port Elizabeth and Grahamstown (Beddard 1886 b; Michaelsen 1899 a, 1910), indicate the occurrence of these species in the eastern part of Western Cape and the southern Eastern Cape. The type localities of klopperi in the Adelaide neighbourhood and stuckenbergi near Stutterheim extend the range of the genus in Eastern Cape. M. vernoni and papillatus were found in southern KwaZulu-Natal (Vernon Crookes Nature Reserve and the Pietermaritzburg district) showing the occurrence of this genus to the north. The distribution of Microchaetus is shown in Fig. 1.

Key to species of Microchaetus (s. str.)

1 Spermathecal pores in four intersegmental furrows 12/13, 13/14, 14/15, 15/16...2

– Spermathecal pores in five intersegmental furrows 12/13, 13/14, 14/15, 15/16, 16/17 ..................................................................................................................... 7

2 Clitellum extended on less than 20 segments ....................................................... 3

– Clitellum extended on 20 or more segments ........................................................ 4

3 Clitellum on 10–23; tubercula pubertatis on 19–24 .............. decipiens Michelsen

– Clitellum on 12–28; tubercula pubertatis on 18–23 ............. microchaetus (Rapp)

4 Clitellum commences on segment 10 ................................................................... 5

– Clitellum commences posterior to 10 ................................................................... 6

5 Clitellum on 10–30; tubercula pubertatis dorsolateral, prominent on 16–20 with lateral extensions on 17–19; male pores in 17/18. Spermathecae and their pores occasionally in representatives of the same population also in furrow 16/17 .................................................................................................. papillatus Benham

– Clitellum on 10–33, 34; tubercula pubertatis elongated on 18, 19–24; male pores in 19/20 ....................................................................................... braunsi Michaelsen

6 Clitellum on 11–31; tubercula pubertatis probably in area of 17–22 ..................... ......................................................................................................... rappi Beddard

– Clitellum on 12–32; tubercula pubertatis as prominent ridges on 16–20. Occasionally, in representatives of the same population, posterior spermathecae and their pores in furrow 14/15 reduced .......................................... vernoni Plisko

7 Clitellum on 10–32; tubercula pubertatis narrow ridges on 18–22; male pores in segment 20 ............................................................................... stuckenbergi Plisko

– Clitellum on 11–32; tubercula pubertatis elongated on 22–29; male pores in 20 ........................................................................................................ klopperi Plisko