Potamonautes mulanjeensis, 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 : 504-506

POTAMONAUTES MULANJEENSIS SP. NOV.

( FIGS 5A–C , 6A–C )

Holotype: Madzeka hut 1800 m a.s.l.,15°50′00′′– 16°03′00′′S, 35°30′00′′–35°4″00′′E, Mount Mulanje (form B on tree topology, Fig. 2 ), southern Malawi, SAM A46799, 1 male collected v.2009 by Julian Bayliss. The samples were collected from a pool underneath rocks and from a lowland stream.

Paratype: Lichenya hut, Mount Mulanje, southern Malawi, SAM A46800, 1 juvenile male collected vi.2009 by Julian Bayliss .

A B C

Additional material examined: Mount Mulanje 2000 m a.s.l., southern Malawi, SAM A46801, 2 juvenile males, 3 juvenile females, collected vi.2009 by Julian Bayliss .

Description and diagnosis: Measurements of the holotype are provided in Table 3. Postfrontal crest present and strongly developed, with short forked region at midpoint. Carapace of living specimens light brown. Cephalothorax ovoid, granulated on the anteriolateral margins, and flattened, maximum height ( CH / CL = 0.49) posterior margin width (CWP/CL = 1.51). Urogastric grooves moderately deep, cardiac grooves deep ( Fig. 5A ). 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, terminal segment undivided and characterized by dense setae on posterior proximal surface. Chelipeds markedly unequal, arched right dactylus, both dactyli armed with several small cutting teeth ( Fig. 5B ). Heterochely appears to be associated with the adult male holotype, the remaining specimens are juvenile and are not heterochelous. 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 and 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 pointed tip ( Fig. 6A, B ). Subterminal segment of gonopod 1 tapering distally, inner margin slightly irregular. Basal margins of margins resemble those of P. montivagus ( Chace, 1953) . The species bears superficial resemblances to other large-bodied southern African freshwater crab species such as P. sidneyi , P. perlatus , and Potamonautes granularis , but was found here to be genetically distinct. The close phylogenetic relationship between P. mulanjeensis sp. nov. and the large-bodied South African riverine species suggests a close biogeographical affinity between the Malawian largebodied freshwater crab species and the southern African species.

subterminal segment of gonopod 1 with setae. Gonopod 2 is broken off in the holotype and hence not described. The paratype is a juvenile male and hence was not used to describe gonopod 2.

Distribution: This species has only been collected from high mountain streams (> 1800 m a.s.l.) on Mount Mulanje in southern Malawi and appears to be endemic. The species may be of conservation concern given its current small distribution range.

Remarks: The carapace characters of P. mulanjeensis sp. nov. such as the flat and granulated anteriolateral

Etymology: The species is named after Mount Mulanje, Malawi, where it was first collected.

Figures

Figure 2. A Bayesian phylogram for the combined 12S rRNA + 16S rRNA + COI mtDNA sequence data. Statistical values above the nodes represent values for bootstrapping for maximum parsimony (MP). Values below each node represent the posterior probability (pP) values for the Bayesian analyses. Only bootstrap values> 70% and pP values> 0.95 are shown.

Figure 5. Potamonautes mulanjeensis sp. nov. Male holotype (carapace length = 25.38 mm) Madzeka hut 1800 m a.s.l., Mount Mulanje (form B, Fig. 2), southern Malawi, SAM A46799. A, whole animal dorsal aspect; B, whole animal ventral aspect; C, cephalothorax, frontal aspect. Scale bars = 10 mm.

Figure 6. Potamonautes mulanjeensis sp. nov. male holotype, SAM A46799. A, left gonopod 1, anterior view; B, left gonopod 1 posterior view. Scale bars = 10 mm.