Potamonautes namuliensis, Daniels & Bayliss, 2012

Daniels, Savel R. & Bayliss, Julian, 2012, Neglected refugia of biodiversity: mountainous regions in Mozambique and Malawi yield two novel freshwater crab species (Potamonautidae: Potamonautes), Zoological Journal of the Linnean Society 164 (3), pp. 498-509 : 502-504

POTAMONAUTES NAMULIENSIS SP. NOV.

( FIGS 3A–C , 4A–C )

Holotype: Manho forest 1500 m above sea level (a.s.l.) 15°21′30′′S, 37°03′40′′E, Mount Namuli, Zambézia Province, central Mozambique SAM A46796, 1 male collected 25.xi.2008 by Julian Bayliss. Endemic to Mount Namuli and appears to be restricted to boulder strewn mountain streams with closed canopy forest. Samples were collected from an upland flowing stream in open habitat but also bordering riverine forest, and crabs were found hiding in vegetation overhanging the stream, or in mud on the stream banks, as well as under rocks.

Paratype: Manho forest 1500 m a.s.l., Mount Namuli, central Mozambique SAM A46797, 1 male collected 25.xi.2008 by Julian Bayliss .

Additional material examined: Manho forest 1500 m a.s.l., Mount Namuli, central Mozambique SAM A46798, 1 male and 2 females (one gravid) collected 25.xi.2008 by Julian Bayliss .

Description and diagnosis: Measurements of the holotype are provided in Table 2. Carapace of living specimens light brown to orange, chelipeds with hints of red, particularly on dactylus, tip of propodus. Cephalothorax ovoid, smooth, flattened, maximum height ( CH /CL = 0.48), posterior margin width (CWP/CL = 1.42). Exorbital tooth smooth, nearly continuous with epibranchial corner, postfrontal weak, short fork at midpoint. Urogastric grooves moderately deep, cardiac grooves deep ( Fig. 3A ). Sternites 1 and 2 fused, no suture discernible, suture between sternites 2, 3, and 4 complete, deep. Third maxillipeds filling entire buccal frame except for small, oval respiratory opening; flagellum present on exopod; ischium with faint distinct groove. Two segmented mandibular palps with dense setae, terminal segment undivided and characterized by dense setae on posterior pointed tip ( Fig. 4A, B ). Subterminal segment of gonopod 1 tapering distally, inner margin slightly irregular. Basal margins of subterminal segment of gonopod 1 with setae. Gonopod 2, terminal segment filamentous, about half the length of subterminal segment. Subterminal segment of gonopod 2 widest at base, tapering inward at 0.5 times length, narrow upright process supporting terminal segment ( Fig. 4C ).

Distribution: This species has only been collected from high mountain streams (> 1500 m a.s.l.) in Mount Namuli, central Mozambique, and appears to be endemic to the region, suggesting that it may be of conservation concern considering the anthropogenic impacts such as deforestation in the region.

proximal surface. Chelipeds markedly unequal, enlarged highly arched right dactylus, both dactyli armed with several small cutting teeth ( Fig. 3B ). Heterochely appears to be associated with the three male samples; the two females appear to have chelipeds of equal size. Propodus of right chelipeds also markedly arched. In both chelipeds, carpus with two prominent teeth. Pereiopods slender, pereiopod 3 longest, pereiopod 5 shortest, dactyli ending in sharp point, margins bearing sharp, spine-like bristles. First five segments of abdomen broad short, last two segments longer, terminal segment pointed at distal end. Gonopod 1, terminal segment short, curving away from midline when viewed posteriorly, widest at base, ending in

Remarks: The species is superficially similar to other mountain-living species in South Africa including P. parvicorpus Daniels et al. 2001 from Table Mountain, P. brincki (Bott, 1960) from the Hottentots Holland Mountains, and P. depressus and P. clarus Gouws et al. 2001 from the Drakensberg Mountains. In addition, P. namuliensis sp. nov. also resembles both Potamonautes infravallatus (Hilgendorf, 1898) and Potamonautes xiphoidus Reed & Cumberlidge, 2006 from the Western Usambara Mountains in Tanzania. All six of these species are small-bodied, characterized by a smooth carapace, lack dentition on the anteriolateral margins, have the major cheliped highly arched, and are endemic to mountainous areas. A similar pattern has also been documented for certain freshwater crab species found in the Rift Valley in East Africa ( Reed & Cumberlidge, 2006). Despite the superficial similarity in carapace and cheliped morphology, the species are distinct based on first gonopod structure and all the known species having well-developed, strong postfrontal crest regions.

Etymology: The species is named after Mount Namuli, Mozambique, where it was first collected.

Figures

Figure 3. Potamonautes namuliensis sp. nov. Male holotype (carapace length = 21.55 mm) from Manho forest 1500 m a.s.l., Mount Namuli, Zambézia Province, central Mozambique SAM A46796. A, whole animal dorsal aspect; B, whole animal ventral aspect; C, cephalothorax, frontal aspect. Scale bars = 10 mm.

Figure 4. Potamonautes namuliensis sp. nov. male holotype, SAM A46796. A, left gonopod 1, anterior view; B, left gonopod 1 posterior view; C, left gonopod 2 anterior view. Scale bars = 10 mm.