Revision of the family Carabodidae (Acari, Oribatida) V. Fourth part. Two new species of the genus Congocepheus from the Republic of Rwanda: Congocepheus rwandensis sp. n., and Congocepheus kayoveae sp. n.

Abstract Two new species from Rwanda are described utilizing optical and scanning electron microscope observations: Congocepheus rwandensis sp. n. and Congocepheus kayoveae sp. n. are compared to Congocepheus taurus Balogh 1961.


Introduction
Several species of the genus Congocepheus have recently been redescribed, namely Co. heterotrichus Balogh, 1958, Co. orientalis Mahunka, 1987, Co. hauseri Mahunka, 1989(Fernandez et al. 2013c and Co. involutus Mahunka, 1997, with descriptions of new species Co. gabonensis Fernandez et al., 2013, Co. ektactesi Fernandez et al., 2013and Co. germanicus Fernandez et al., 2014a. A redefinition of Congocepheus was given, and the new genus Cavaecarabodes, related to Congocepheus, was defined and two new species described: Ca. pulchritude Fernandez et al., 2014a, andCa. anouchkae Fernandez et al., 2014a. Cavaecarabodes includes some species previously considered members of the genus Congocepheus. Type specimens of Co. ornatus Mahunka, 1983, Co. latilamellatus Mahunka, 1984and Co. velatus Mahunka, 1986 were studied to establish their position in Congocepheus, and at the same time large collections of material were obtained from Rwanda, Zimbabwe, Kenya, Cameroon, the Republic of the Congo, Côte d'Ivoire and Thailand, which are housed at the Natural History Museum of Geneva (NHMG); and from Antilles, Namibia, the Democratic Republic of the Congo, Central African Republic, Tanzania, Ethiopia, Angola, Sudan and South Africa, from the Museum National d'Histoire Naturelle in Paris, France (MNHN). From this material numerous specimens of Congocepheus and related genera have been identified. A decision was made to continue with the series of studies of Congocepheus, including a number of very interesting new species related to Co. ornatus, Co. latilamellatus and Co. velatus. In this paper, two new species from Rwanda are described, making use of optical microscopy and SEM. Valuable information was obtained from SEM studies, which would be extremely difficult to obtain with optical microscopy alone.

Material and methods
Specimens studied by means of light microscopy were macerated in lactic acid and observed in the same medium using the open-mount technique (cavity slide and cover slip) as described by Grandjean (1949) and Krantz and Walter (2009). Drawings were made using a Zeizz GFL (West Germany) compound microscope equipped with a drawing tube.
Specimens were also studied by means of scanning electron microscope (SEM). Specimens preserved in ethanol were carefully rinsed by sucking them several times into a Pasteur pipette, after which they were transferred to buffered glutaraldehyde (2.5%) in Sörensen phosphate buffer: pH 7.4; 0.1 m for two hours. After postfixation for 2 hours in buffered 2% OsO4 solution and being rinsed in buffer solution; all specimens were dehydrated in a series of graded ethanol and dried in a critical point apparatus. After mounting on Aluminium-stubs with double sided sticky tape, specimens were gold coated in a sputter apparatus (Alberti and Fernandez 1988, 1990a, 1990bAlberti et al. 1991Alberti et al. , 1997Alberti et al. , 2007Fernandez et al. 1991). SEM observations were made using a FEI-Quanta Feg 250; with 10 Kv and working distance (WD) variable. Measurements taken: total length (tip of rostrum to posterior edge of notogaster); width (widest part of notogaster) in micrometres (μm).
Leg chaetotaxy studies using standard, polarized and phase contrast microscopes are provisional, due to the fact that only adult specimens were available. Setal formulae of the legs include the number of solenidia (in parentheses); tarsal setal formulae include the famulus (ε).
Paratype: two adult females, same locality and date as Holotype; deposited in Collection of MHNG; preserved in 70 % ethanol. Material studied for SEM: three specimens, not deposited.
Epimeral chaetotaxy 3-1-3-3. Discidum easily discernible; anterior genital furrow (a.g.f) clearly visible, situated in front of genital plate. Large genital plate; four pairs of genital setae, simple linear arrangement; all setae more or less equal in length; aggenital setae (ag) situated posteriorly to genital opening. Three pairs of adanal seta; ad 3 close to ag setae. Anal plate polyhedral, sharply tipped. Two pairs of anal setae. Lyrifissures iad well discernible, situated laterally between ad 3 and ad 2 . Depressions (dep) clearly visible, situated laterally to genital and anal openings.
Shape. Elongate oval (Figure 19). Colour. Specimens without cerotegument; light brown to yellowish-brown when observed in reflected light.
Clearly delimited zone on s.c with more or less smooth cuticula, immediately followed by clearly delimited pusticulate zone (Figure 29), and slightly below insertion of setae h 3 , p 3 , p 2 , p 1 to h.ap, a smooth zone extending to b.ng. Clearly delimited depressed zone behind leg IV. Cuticular ribbon (Figure 29 indicated by X) parallel to b.ng.
Remarks. In some specimens the cerotegumental layer appears damaged ( Figure  33), as more than 40 years have passed since collection, preservation of specimens may have been influenced by the quality of the initial diluted alcohol. Material of much greater age has been studied previously without problems, but in this case, the description of the cerotegumental layer must be regarded as provisional.
Twisting setae complicate and obscure observation; use of SEM vital in providing adequate information, while small particles adhering to setal surfaces further compli-    cate observation. In several cases study material presents slight genital neotrichy; in two instances five pairs of setae were observed. One example of neotrichy was observed in Congocepheus, with notogastral neotrichy present in Co. germanicus; but Co. kayoveae is the first observed occurrence of genital neotrichy.

Discussion
The two species described in this paper are related to Congocepheus taurus Balogh 1961. Unfortunately, as we were unable to obtain the type material, Co. taurus is the only species within the genus Congocepheus we were unable to study. The type locality given by Balogh is "Africa Orientalis: Meru", and searching through our material from Tanzania, we were unable to locate this species.
The description given by Balogh 1961 (page 522) is short and imprecise with only two figures, 10 (dorsal) and 11 (lateral) (page 523); figures lack detail, with important omissions. The following comparison is confined to an analysis of characters and figures provided by the author in 1961.
Commonalities: Co. taurus and Co. rwandensis are similar in terms of body shape; presence of irregular cord-shaped structures on notogaster; one central vein present on setae c 1 and in; e.i.p elevated with in setae situated anteriorly; p.p.d and n.a.d determine a large depression; presence of f.l.p. Co. taurus is similar to Co. kayoveae with regard to the presence of irregular cord-shaped structures on notogaster; c 1 setae with one central vein; presence of f.l.p.
Differences: Co. taurus differs from Co. rwandensis in terms of very short c 1 setae; e.i.p divided; f.l.p very different in shape; disposition, direction and shape of notogastral setae. Co. taurus differs from Co. kayoveae in terms of body shape; very short setae c 1 ; p.p.d and n.a.d different in shape and size; greatly differing shape of e.i.p; in setae with only one vein; disposition and direction of notogastral setae; f.l.p very different shape.  , dp, v, l" d,v (v), l",d (ft),ε,(tc),(it),(p),(u),(a), s,(pv), Ad" 1 solenidia σ φ 1, φ 2 ω 1, ω 2 Leg II setae dp, da, l' d,l',v v, d, l' (pv) The complexity of several structures present in species studied, necessitated observation from many different angles, as was the case in Antongilibodes paulae Fernandez et al., 2014 andMangabebodes kymatismosi Fernandez et al., 2014. In the description of Congocepheus kayoveae sp. n., Figures 29, 30, 31, and 34 are complementary; lateral, frontal and frontal inclined views permit understanding of several characteristics and aspects not clearly observed (or difficult to interpret) in only the lateral or ventral position. Succinct studies such as that of Co. taurus, with a short description and poorly developed figures, confound comparison, and several particularities of this species may go unnoticed.
In Congocepheus kayoveae sp. n. a similar situation was observed to that in Mangabebodes kymatismosi, Fernandez et al. 2014; where the tutorium forms a prominent lateral expansion and is relatively large; considered to be the first instance where this particularity is observed in Congocepheus. In Co. kayoveae sp. n., the s.tu.d is very deep, completely concealing leg I.
Other interesting aspects are the position of the lateral setae (l") of genu II ( Figure  20), which during the leg folding process (See Fernandez et al. 2013a) protect the opening of the bothridium, and the perfect coaptation of the legs and depressions during leg folding ( Figure 29).