Tritogenia talana, Nxele & Plisko & Ramongalo, 2018

Nxele, Thembeka Clara, Plisko, Jadwiga Danuta & Ramongalo, Boipelo K., 2018, The first proandric species of Tritogenia Kinberg, 1867 from Botswana, Tritogenia talana sp. n. (Clitellata, Crassiclitellata, Tritogeniidae), Zootaxa 4496 (1), pp. 214-217 : 215-216

Tritogenia talana sp.n.

( Figure 1 )

Locality and material. Botswana, Tuli Block region, Talana Farms , Limpopo River edge, 22°14'13.7''S; 29°00'43.8''E, 359 m asl, 05.ii.2016, T. Nxele, B. Ramongalo & N. Serameng leg.

Holotype. Clitellate, NMSA / OLIG.06946.

Paratypes. 1 clitellate, NMSA / OLIG.06726a; 1 clitellate, NMSA / OLIG.06943a.

Additional material. 1 juvenile, NMSA/OLIG.06726b, 1 juvenile, NMSA/OLIG.06943b.

Description. External. Holotype: body length 52 mm, width 4 mm at tubercula pubertatis; segment number 102. Paratypes: 50–60 mm in length, width 3–4 mm, segment number 107–110. Colour whitish grey. Prostomium prolobous. Preclitellar segments with secondary annulations: segment 1–3 simple, 1–2 with small horizontal grooves, segment 4–8 with two ringlets of similar size, 9–10 with second ringlet smaller, from 11 and in postclitellar segments simple and randomly annulated. Setae aa> ab = cd <bc, all minute, clearly visible on segments near tubercula pubertatis, difficult to locate on preclitella segments. Male pores not observed. Female pores minute on anterior part of segment 14. Spermathecal pore not observed. Clitellum saddle-shaped on 12,13–24,25. Tubercula pubertatis on 18,19–20,21 (figure 1). Genital papillae absent.

Internal. Septa 4/5 slightly thickened; 5/6–8/9 strongly thickened; other septa thin. Gizzard well developed in 6–7 with septum 6/7 attached. Calciferous glands in 9, large, fused dorsally. Intestinal origin in 12. Typhlosole begins in 20, V-shaped which enlarges into U-shaped. Dorsal blood vessel double in the anterior segments; hearts in 9 and 10; simple in the posterior segments. Nephridia meroic, single duct with coiled loops at the end, two pairs per segment. Proandric. Seminal vesicles lacking. Spermathecae not observed, possibly embedded deep in muscular tissue.

Etymology. Named after Talana Farms, the type locality. Noun in apposition.

Remarks. This species is most similar to T. debbieae Plisko, 2003 in body length (50–60 mm), typhlosole (starting as V-shaped) and calciferous glands (not separated dorsally). The new species differs in the extension of the clitellum (12,13–24,25 vs. 13–23) and in thicker septa (4/5–8/9 thickened vs. 4/5–7/8 and all other septa in preclitellar segments thin). Tritogenia talana sp. n. is clearly different from all other Tritogenia species by its lack of seminal vesicles.

The earthworm fauna of Botswana is currently unknown. Our recent collection resulted in the discovery of an indigenous Tritogenia species new to science. This species was collected in the south-eastern part, the Tuli Block. The northern region was also investigated but no Tritogenia species were found. The collection of T. talana sp. nov. provides new knowledge on the distribution of Tritogenia as it was assumed that possibly the northern boundary for South African species is the Limpopo River ( Plisko 2012). There is a possibility that some species may occur in Mozambique and Zimbabwe along the Limpopo River.

The reproductive organs of T. talana sp. n. show some level of degeneration. Most conspicuous is the lack of seminal vesicles, unusual in this genus: all other known species of Tritogenia have variably sized seminal vesicles in two segments. Other afrotropical earthworm species that lack seminal vesicles are found in Madagascar and belong to the family Kynotidae ( Razafindrakoto et al. 2011; Csuzdi et al. 2012). Furthermore, spermathecae were not observed in holotype and paratypes and may be absent as well, or they were deeply embedded in muscle tissue. As noted by Nxele (2014), spermathecae are difficult to observe in Tritogenia , especially when embedded in tissue and without sperm, so the possibility remains that they have been overlooked. Finally, this is the first proandric species in this genus, the pair of funnels is small. The reduction in reproductive organs suggests parthenogenesis although more data is needed to validate this. Hermaphrodite species may reproduce parthenogenetically. For example, Amynthas catenus Tsai et al., 2001 was found to reproduce parthenogenetically ( Shen et al. 2011), based on the study of reproductive organs and DNA ploidy levels. More qualitative collection campaigns in the country may reveal new earthworm species and confirm these suppositions.

Figures

FIGURE 1. Tritogenia talana sp. n. Anterior region of specimen, external ventral view. Cl= clitellum, Tp= Tubercula pubertatis. Numbers represent segment numbers. Scale bar 10 mm.