Tritogenia tetrata, 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 : 319-323

Tritogenia tetrata sp. n.

( Fig. 18 )

Etymology: G. tetra = four. Refers to the arrangement of spermathecal pores in four intersegmental furrows.

Material examined: KwaZulu­Natal: Holotype NMSA/Olig.03528 Nkandla Forest Reserve (28º42'59"S: 31º08'05"E) at 1178 m of forest edge, under recently burnt short grass, between roots of various plants, 21 November 2001, AJA, HM. Paratypes: NMSA/ Olig.03529, 2 cl + 3 with developing tubercula pubertatis + 3 juv, collected together with holotype. Other material: NMSA/Olig.03367 on summit near Nkandla State Forest (28º42'09"S: 31º07'28"E) under rock in grassland, 13 March 2001, 1 semi­mature with no spermathecae, BK, B. Church, S. Louw; NMSA/Olig.03366 on summit near Nkandla Forest Reserve (28º42'09"S: 31º07'32"E) under rock in grassland, 13 March 2001, 1 well developed clitellate [with abnormally regenerated segments], BK, B. Church, S. Louw; NMSA/Olig.03532 Nkandla Forest Reserve (28º42'44"S: 31º08'39"E) at 1204 m, grassland, east­facing slope, under grass burnt 3 years ago, at 30 cm depth, 21 November 2001, 2 cl, AJA, HM [associated with acanthodrilid of the genus Udeina , and Proandricus babanango ]; NMSA/Olig.03427 Nkandla Forest Reserve (28º44'31"S: 31º08'54"E) hillside, at the edge of forest, 10 April 2001, 2 juv, AJA, PN. Description based on holotype and paratypes.

External characters:

General: body cylindrical, compact after preservation. Colour: grey in life; preserved yellowish­grey with last 4–5 segments dark brown. Dimensions: preserved and contracted holotype 76 mm long, 7 mm wide at 10, 8 at tubercula pubertatis; mature paratypes with no clitellum, 52–66 mm long, 6–7 mm wide at tubercula pubertatis; juveniles 42– 52 mm long, 5 mm wide. Segment number: holotype 81, paratypes 77–83. Prostomium: prolobous, small. Segmentation: secondary annulation present on preclitellar segments, observed in holotype and paratypes; 1–3 simple, short, with irregular longitudinal grooves; 4–8 with 2 simple ringlets, similar in size and appearance; 9–10 with 2 ringlets, second shorter than first; 11 and clitellar simple, smooth; postclitellar segments irregularly annulated. Setae: minute, closely paired, with irregularities in longitudinal arrangement; on 8–18 distance between pairs of ab setae converging, postclitellarly slightly more distanced, in irregular, uneven lines; cd pairs in irregular lines on whole body length. Nephridial pores: not observed. Female pores: paired, minute, between aa setae in 14, close to 13/14 intersegmental furrow. Male pores: probably in intersegmental furrow 19/20 on tubercula pubertatis, where there are paired small depressions. Spermathecal pores: obvious in intersegmental furrows 12/13 13/14 14/ 15 15/16, slightly above cd setae.

Clitellar region ( Fig.18 ): Clitellum: saddle­shaped, pale or brownish, segmented; on holotype 15–26, on paratypes 14, 15–25, 26; on holotype clearly bordered anteriorly and posteriorly, on paratypes with faint borders; on first two anterior clitellar segments extending only dorsally, not reaching cd setae; on following segments, ventral borders extend slightly below cd setal lines, touching dorsal rims of tubercula pubertatis. Tubercula pubertatis: oblong, broad pads on 1/n17,18–23; commencing abruptly, terminating at intersegmental furrow 23/24. Dorsally commence below cd setal lines, ventrally terminate along a setae; clearly segmented, rimmed around, dorsally with soft fold separating pads from clitellum. Papillae: paired or single, on 11–19, 26; small swellings in ab and cd setal lines.

Internal characters:

Septa: 4/5–8/9 thickened very much, similar in size and appearance, 9/10 aborted; other septa thin. Gizzard: large, muscular, in 6–7; commencing at septum 5/6, extends through whole of 6 and 7; septum 6/7 attached to its middle. Calciferous glands: one pair stalked, dorsolateral, muscular, in 9–10; each gland connected to oesophagus by soft stalk in 9. Intestine: commences in 13, with some anterior part reaching posterior part of segment 12. Typhlosole: in holotype commences abruptly in 20 as V­shaped, sharply enlarging in following segments becoming large U­shaped fold; terminates in area of 49. Dorsal blood vessel: double in 4–11; double when crossing septa 4/5–10/11; simple in 12 and following segments. Paired dorsoventral commissural vessels: 4–8 thin, gradually enlarging; 9–11 thick, moniliform. Nephridia : two pairs per segment; ventral pairs close to median bodyline, lateral pairs dorsolaterally; in preclitellar segments much larger than posteriorly; in posterior segments small, coiled. Spermiductal funnels: holandric arrangement; two pairs, similar in size and appearance, iridescent, in 10 and 11 respectively; each pair enclosed in sac closely connected with seminal vesicles. Seminal vesicles: two pairs of sacs linked with testis sacs in 10 and 11 respectively. Spermathecae: tiny ampullae in 12–15, multiple at each side. Ovaries: paired, in 13, large, funnel­like, close to median line near septa 13/14. Genital glands: in 15–18 paired, small, flat; in 26 paired, large, oval.

Biological notes:Although approximately 85% of the Nkandla Forest Reserve, protected by KZN Wildlife, is covered by forest, the species was found between the roots of various short grasses which cover the margins of the forest verges. The soils in this grassland are shallow but there are some fairly deep watered patches. The grasses are regularly burned to provide grazing for cattle

Distribution: The species is known only from the protected area of the Nkandla Forest Reserve and its close vicinity ( Fig. 14 ).

Discussion: T. tetrata is unique in the genus for having spermathecae in four segments, and the spermathecal pores in intersegmental furrows 12/13–15/16. This remarkable species cannot be located in any of the species­groups established by Plisko (1997), and the new species­group is proposed to accommodate the species with four rows of spermathecae. The irregular arrangement of setae observed in tetrata resembles those irregularities noted in annetteae and ataxia of the sulcata species­group.

The zuluensis ­ species group

Characterised by multiple spermathecal pores in more than four intersegmental furrows, comprises species: crassa Michaelsen, 1918 , melmothana (Michaelsen, 1928) and zuluensis (Beddard, 1907) .

T. crassa and melmothana are known only from their type localities; zuluensis has also been collected from the vicinity of its type locality (Plisko 1992). Species occurrence is shown in Fig. 14 . No new material of this group was studied.

NOTES ON THE FAUNA OF MICROCHAETIDAE IN KWAZULU­NATAL

Although microchaetids are usually found in conditions generally suitable for other megadrile earthworms, most of the species prefer natural undisturbed habitats. Their limited ability to disperse naturally has resulted in speciation, which has produced many endemics found within restricted ecological habitats. All 137 species are endemic to the southern part of the African continent, and are assigned to four genera: Microchaetus (49), Proandricus (51), Tritogenia (36), and Michalakus (1).

Microchaetus has the widest distribution, as shown by Plisko (1998). Species are known the Northern Cape, Western Cape, Eastern Cape, KZN, Mpumalanga, and Limpopo provinces of South Africa, as well as from neighbouring Swaziland. The genus occurs in a variety of biotopes. Only 15 species have been recorded from KZN, of which 12 are endemic to the province, and exist in small areas of primary grassland, indigenous forest and woodlands. Microchaetus species known from KZN are listed in Table 1. Only three species extend their occurrence outside this province. M. pondoanus is known from a small area bordering the two provinces of KZN and Eastern Cape. Species natalensis and parvus occur at numerous sites in KZN and range beyond this province to the north. M. natalensis is known from KZN, Mpumalanga and Limpopo provinces, and from Swaziland. M. parvus has been collected in natural sites, as well as in cultivated areas into which it has been introduced, and occurs in KZN and Mpumalanga provinces.

Michalakus is monotypic and is known only from two sites in the KZN Midlands and is endemic to this province.

Proandricus is found in South Africa and Lesotho, ranging through the southeastern part of the Eastern Cape, through KZN, and terminating its distribution in northern Mpumalanga. Of the 51 known species, 30 occur in KZN with 28 being endemic to the region (Table 2). Species with a wider distribution, occurring in KZN and in the other provinces, include setosus and modestus . P. setosus is known from KZN and Mpumalanga. P. modestus has been collected at numerous localities in North West, Free State, Eastern Cape, KZN and Mpumalanga provinces. It is known mainly from agricultural fields, but also from less disturbed biotopes on the banks of rivers and road verges. Its wide distribution may result from an ability to adapt to environmental disturbance.

The other known proandric species (except sirgelli, known from Western Cape) occur in the south­eastern part of Eastern Cape, often ranging to the southern border of KZN, or occur at high altitudes in the Drakensberg mountain range and in Lesotho. Most of the Proandricus species are confined to natural biotopes. They occur in small areas with undisturbed soil, in indigenous grassland and pastures, but may occur also in indigenous forest and bushveld habitats, or open savannah.

Tritogenia is endemic to the north­eastern parts of South Africa. Of the 36 species, 27 are endemic to KZN (Table 3). They occur in primary grasslands, endemic forests with patches of grasses, and undisturbed sites in protected areas. Sporadically they may be found in freshly cultivated gardens (i.e. zuluensis , curta ), or near roads and on the banks of rivers, but always with clear preference for natural habitats. Three species, ataxia , herbana and liversagei , occur in northern KZN and range into Mpumalanga. Four species not recorded from KZN— kruegeri , palusicola , silvicola , and turneri — are known only from Mpumalanga and Limpopo provinces. The last two species occur as far north as the Soutpansberg mountain range. Only grisea has a wider distribution, being recorded from Free State, North West, Mpumalanga and Gauteng provinces. Although the distribution of benhami is not known, the species may eventually be found to occur in KZN. Tritogenia species, like other microchaetids, prefer natural habitats, and their distribution is usually confined to small areas.

The knowledge of microchaetid distribution in South Africa is incomplete. KZN province is the best researched, and probably has the best known microchaetid fauna. Recently obtained data provide more information on general microchaetid biodiversity and species distribution, throwing new light on generic ranges throughout the country. Proandricus species occur in the eastern parts of South Africa, with more than half of the species being endemic to KZN. Microchaetus with its widest distribution in Southern Africa may be made up of several distinct lineages. It is of distinct interest that a relatively small percentage of species occurs in KZN. Tritogenia , the other holandric genus, is endemic to the north­eastern parts of the country, with the majority of species living in KZN. During many years of collecting in other parts of the country, no Tritogenia species were found south of this province, though the presence of Tritogenia was positively established north of KZN.

This study demonstrates that KZN has the greatest variety of microchaetid species, with nearly 57% of the described species, although additional species undoubtedly await discovery elsewhere. Further surveys are required in areas not yet investigated, and should be conducted during the periods when earthworms are most active. Present knowledge of microchaetid distribution reveals extensive regional diversification, related to ecological and possibly climatic conditions, and linked to palaeo­geological transformation of this sub­region of Africa.

Figures

Fig. 18. Tritogenia tetrata sp. n., holotype, anterior part of the body ventrally, showing secondary annulation of segments 4–10, tubercula pubertatis, and papillae.

Fig. 14. The distribution of Tritogenia species in KZN. 1 = alveata; 2 = annetteae; 3 = ataxia; 4 = benhami; 5 = crassa; 6 = curiosa; 7 = curta; 8 = debbieae; 9 = diversa; 10 = douglasi; 11 = herbana; 12 = hiltonia; 13 = howickiana; 14 = insolita; 15 = karkloofia; 16 = koilia; 17 = liversagei; 18 = lunata; 19 = melmothana; 20 = miniseta; 21 = monosticha; 22 = morosa; 23 = mucosa; 24 = ngelensis; 25 = ngomensis; 26 = qudeni; 27 = shawi; 28 = soleata; 29 = sulcata; 30 = tetrata; 31 = zuluensis.