Rhampsinitus transvaalicus Lawrence, 1931

Schönhofer, Axel L., 2008, On harvestmen from the Soutpansberg, South Africa, with description of a new species of Monomontia (Arachnida: Opiliones), African Invertebrates 49 (2), pp. 109-109 : 122-125

Rhampsinitus transvaalicus Lawrence, 1931

Figs 11 , 12A–L

Rhampsinitus transvaalicus: Lawrence 1931: 493 , text-fig. 77; 1963: 304.

Diagnosis:Although highly variable, males of this species are easily distinguished by a row of large retrolateral curved spines on the femur of chelicerae ( Figs 12E, G, I–K ). The closely related R. leighi Pocock, 1902 has smaller spines irregularly scattered on the chelicerae ( Fig. 12M ). The penis of R. transvaalicus is bulbous at the base, whereas that of R. leighi is slender in lateral view ( Figs 12A–D, 12N, 12O ).

Material examined: SOUTH AFRICA: Limpopo: 7ơ Hanglip Forest, north of Makhado , alt. 1370 m, ii.1960, R.F. Lawrence ( NMSA, 7597); 4ơ 4^( NMSA, 7598); 2^( NMSA 7603 ) ; 1ơ 1^Makhado, alt. 915 m ( NMSA, 7605); 1ơ 1^Entabeni forest, 48 km east of Makhado ( NMSA, 7607); 5ơ 2^316 juv. Lajuma , alt. 1350 m, evergreen montane forest, 22.x–19.xi.2002, A.L. Schönhofer ( CJM, 4812–4820) .

Other material examined: R. leighi : SOUTH AFRICA: KwaZulu-Natal: 1ơ Hluhluwe Game Reserve (28 ° S: 32 ° E), higher altitude forest with Celtis africana , Harpephyllum caffrum, 1982 , W. Wickler (CJM, 2142) ( Fig. 12M–O ).

Biology/Ecology: Most animals were caught walking on a road in subtropical evergreen forest at night. They were most abundant near a small permanent stream. Pitfall trapping was successful only for small juveniles. Traps recorded specimens only in forest habitats with permanent water a few hundred metres away. Two males were found sitting at the side of stones near the ground, face looking down ready to catch prey. Adults’ bodies were often infested by red mites. Only seven adults were caught, but 316 juveniles in predominantly early stages of development. On one occasion a juvenile was seen carrying a cockroach double its body size; whether it was caught or just picked up dead was not observed.Adults are recorded from October to December and in February. The presence of juveniles in February suggests extension of maturity beyond that date. P. Schwendinger did not collect any specimen in April.

Comments: As the material from Lajuma contained only five adult males, which were highly variable in body size, coloration and length of chelicerae, additional material from the type locality Makhado was investigated. These specimens showed allometric growth of the male chelicerae and palps with increasing body size ( Fig. 13 ). This phenomenon is reported from other Phalangiidae like the European Phalangium opilio Linnaeus, 1761 , Zacheus crista (Brullé, 1832) (for both see Martens 1978 b; Lerma 1952), the African Guruia africana (Karsch, 1878) ( Stare,ga 1984) and R. leighi ( Pocock 1902; Lawrence 1931; Kauri 1961). Martens (1978 b) mentioned males of European species becoming similar to females with decreasing body size and loss of external sexual characteristics. In R. transvaalicus this is nicely expressed in the toothing of the cheliceral pincer, which is radically changed to female appearance if body size falls below a certain value. Large specimens display three prominent teeth, whereas smaller males and females have only two ( Figs 12H, 12F, 12L , 13 ). Kauri (1961) mentioned this circumstance for the closely related Rhampsinitus leighi without connecting it to allometric growth. Other characters, like length of legs, darkness of coloration or intensity of spination of chelicerae and ocularium, gradually change with body size.A convergent sexual dimorphism is exhibited in members of the Australian and New Zealand family Monoscutidae Forster, 1948 . Males of the genera Pantopsalis Simon, 1879 and Spinicrus Forster, 1949 have extremely elongated palps ( Forster 1949) and are polymorphic in respect to this character ( Taylor 2004).

One male of R. leighi (CJM, 2142) is remarkable for its large body size, extending the variability of this species to 7.05 mm. Chelicerae length of 42 mm results in chelicerae 6 times longer than body size ( Fig. 12M ; chelicerae 2–4 times longer than body are reported by Lawrence (1931) and Kauri (1961)).

Figures

Fig. 11. Rhampsinitus transvaalicus, body in dorsal view, palps: (A–D) ơ, Lajuma: (A, H) CJM, 4816; (B, D, G) CJM, 4819; (C) CJM, 4820; (E, F) ^, Makhado, NMSA, 7603; (G, H) palps, medial view. Scale bar = 2.0 mm.

Fig. 12. Rhampsinitus, penes and chelicerae: (A–L) R. transvaalicus: (A, B) NMSA, 7597; (C, D) NMSA, 7598; (E, F) CJM, 4819; (K) CJM, 4819, different ơ; (I) CJM, 4820; (L) CJM, 4814; (G, H) CJM, 4816; (M–P) R. leighi, KwaZulu-Natal, Hluhluwe Game Reserve, CJM, 2142. (A–D, N, O) penes: (A, C, N) lateral and (B, D, O) dorsal views, scale bar 1.0 mm at B; (E, G, I, K, M) chelicerae, lateral view, scale bar 2.0 mm at E and 10 mm at M; (F, H, L, P) pincer, dorsal view, scale bar 1.0 mm at F. (L) ^, all others ơ.

Fig. 13. Allometric and normal growth in Rhampsinitus transvaalicus. Scatterplot left: allometric growth of segment 2 of chelicerae; change of toothing in pincer at a body size of 4.1–4.3 mm is indicated by circles (2 teeth) and squares (3 teeth). Scatterplot right: femur I representing normal growth as for all legs.