Potamonautes gorongosa, Cumberlidge & Daniels, 2016

Potamonautes gorongosa View in CoL new species

( Figs. 1–2 View Figure 1 View Figure 2 )

Potamonautes sp. 2 – Daniels et al., 2015: Pg. 553, Table 1; Pg. 558, Fig. 2 View Figure 2 .

Material examined. Gorongosa National Park , Sofala Province, 18.47227°S 34.21411°E, 320 m asl. Holotype: male subadult (CW 25.4, CL 18.8, CH 9.0, FW 8.3), coll. P. Naskreski, 2012, Northern Michigan University museum collection (NMU PN3 2012A). GoogleMaps

Diagnosis. Vertical sulcus on ischium of third maxilliped absent ( Fig. 1B View Figure 1 ). Fixed finger of propodus of major cheliped slender with 7 distinct molars along its length ( Fig. 2A, B View Figure 2 ); moveable finger of propodus of major cheliped with two large raised teeth in proximal region; first (distal) carpal tooth long, slender, pointed; second (proximal) carpal tooth less than half size of first carpal tooth, pointed, followed by several small granules; distal lower mesial margin of merus with large pointed tooth ( Fig. 1A View Figure 1 ). S3/s4 deep at edges, faint in middle, not meeting tip of sternoabdominal cavity; s4/e4, s5/e5, s6/e6, s7/e7, faint, incomplete ( Fig. 1C View Figure 1 ). G1 terminal article straight basally, curving outward at 60° angle to longitudinal axis of gonopod medially, tip pointed, distinctly upturned ( Figs. 2C–E View Figure 2 ). G2 terminal article flagellum-like, almost as long as subterminal segment ( Fig. 2F View Figure 2 ).

Description of male holotype. Carapace transversely oval, very wide (CW/FW 3.1), medium height ( CH / FW 1.1), surface texture smooth; cardiac, urogastric grooves deep, cervical grooves short, faint, transverse branchial grooves absent ( Fig.1A View Figure 1 ). Front narrow (FW/ CW 0.32), deflexed ( Fig. 1B View Figure 1 ). Postfrontal crest faint, complete, strongest at anterolateral margins where it meets epibranchial tooth; postorbital, epigastric crests faint ( Fig. 1A View Figure 1 ). Anterolateral margin finely granulated, continuous with posterolateral margin; epibranchial tooth very small but distinct; exorbital tooth low, blunt; vertical sulcus on carapace sidewall granulated, meeting anterolateral margin at epibranchial tooth; suborbital, pterygostomial region of carapace sidewalls completely smooth; subhepatic region of sidewall with fine granules ( Fig. 1B View Figure 1 ). Mandibular palp two-segmented, terminal article simple, setose; epistomial tooth triangular, deflexed, edges granulated. Third maxillipeds filling entire oral field, exceptfor transversely oval respiratory openings at superior lateral corners; vertical sulcus of ischium of third maxilliped absent; exopod of third maxilliped reaching to lower half of merus, with long flagellum ( Fig. 1B View Figure 1 ).

S1/s2 faint; s2/s3 deep, running horizontally across sternum; s3/s4 deep at edges, faint in middle, almost meeting sternoabdominal cavity; anterior margin of sternoabdominal cavity thin, low; s4/e4, s5/e5, s6/e6, s7/e7, faint, incomplete ( Fig. 1C View Figure 1 ). Abdomen (pleon) slim, outline triangular, tapered, widest at a3, telson outline forming straight-sided triangle with broad base, rounded apex; s6/s7 meeting abdomen at a5/a6; s5/ s6 meeting a6 one half of segment length from a6/a5 ( Fig. 1C View Figure 1 ). G1 terminal article straight basally, curving outward at 60° angle to longitudinal axis of gonopod medially, tip pointed, distinctly upturned ( Fig. 2C–E View Figure 2 ). G2 terminal article flagellum-like, almost as long as subterminal segment ( Fig. 2F View Figure 2 ).

Dactylus of major cheliped slender, arched, closed fingers enclosing wide oval interspace; upper margin of dactylus of cheliped smooth; fixed finger of propodus of major cheliped with 5 distinct, large teeth interspersed by smaller teeth; lower margin of propodus slightly indented ( Fig. 2A, B View Figure 2 ); first carpal tooth large, pointed; second carpal tooth less than half size of first carpal tooth, pointed, followed by several small granules; distal meral tooth small, pointed; superior margins of merus of cheliped lined by series of small, pointed teeth; superior surface of merus smooth, superior margin with carinae; outer face of merus smooth, lateral margin of inferior face of merus with very small teeth; inferior margin of ischium with small pointed teeth ( Fig. 1A View Figure 1 ). Walking legs (p2–p5) normal length, inner margins of propodi p2–p5 smooth, dactyli of p2–p5 tapering to point, each bearing four rows of downwardpointing short, sharp spines ( Fig. 1A View Figure 1 ).

Size. A medium-sized species, the male holotype has a CW of 25.4 mm.

Type locality. Mozambique: Gorongosa National

Park , Sofala Province, 18.47227°S 34.21411°E GoogleMaps , 320

m above sea level (asl) (NMU PN3 2012A).

Etymology. The new species is named for Gorongosa National Park in Mozambique, the only place that it is known to occur (so far).

Distribution. Potamonautes gorongosa , new species, is known from one locality in Gorongosa National Park in Mozambique. This is a 4,000 km 2 park at the southern end of the Rift Valley in central Mozambique, and includes Mount Gorongosa (1,863 m asl) where P. gorongosa was collected. The Gorongosa National Park dominates the Gorongosa District in Sofala Province of Mozambique.

Habitat. The freshwater crabs reported on in the present study were collected by the second author from Sofala Province in Mozambique, in highland and montane fresh waters where the vegetation type is predominantly savanna with fast-flowing mountain streams and rivers. This narrow 450 km long area lies within the Eastern Zimbabwe Highlands ecoregion in southeastern Africa along the eastern border of Zimbabwe with Mozambique and includes the Nyanga and Chimanimani mountains whose rivers drain eastwards through Mozambique ( Thieme et al., 2005; Abell et al., 2008). The known locality for P. gorongosa lies in the Zambezian lowveld freshwater ecoregion that comprises most of western and northern Mozambique and extends from south of the Zambezi delta in central Mozambique southwards to the Tugela River system in South Africa ( Thieme et al., 2005; Abell et al., 2008). This species was collected with P. obesus a semi-terrestrial burrowing freshwater crab found in the coastal belt of eastern Africa from Kenya to Mozambique ( Reed and Cumberlidge, 2004). The report of P. obesus from western Mozambique is a new record for this species in this part of the country.

Remarks. Afrotropical freshwater crabs undergo morphological changes as they grow and while most of this growth is isometric, some parts of their body (notably the major cheliped and the gonopods of males and pleopods of females) grow allometrically. Freshwater crabs start life as juveniles, then progress to subadults, and finally become reproductive adults after passing through the pubertal moult ( Cumberlidge, 1999). The specimen of P. gorongosa new species, is judged here to be a subadult following comparisons with congeneric species such as P. mulanjeensis , P. mutareensis , and P. flavusjo (whose adults are between CW 30–34.8 mm) ( Daniels and Bayliss, 2012; Phiri and Daniels, 2013; Daniels et al., 2014). This indicates that although the specimen of the new species is a subadult, it is nevertheless of a body size that will soon undergo the pubertal moult. This distinction is important when considering the utility of taxonomic characters of freshwater crabs, although most of the morphological characters commonly used for taxonomy (such as those of the third maxilliped, thoracic sternum, mandible, the merus and carpus of the cheliped, and the number and size of the teeth on the cutting edges of the cheliped fingers) undergo isometric growth and are not likely to be significantly different in subadults and adults. On the other hand, characters of the gonopods and major cheliped that grow allometrically are more developed in adults than in subadults. The subadult of the new species is well-developed and close to the pubertal moult, and so the gonopods would not be expected to develop a radically different form from those described here even after the next moult. This is supported by the observations that the gonopods of P. gorongosa new species ( Fig. 2C–F View Figure 2 ) are similar in most respects to those of the three genetically close species ( P. mulanjeensis , P. mutareensis , and P. flavusjo that are adult at CW 30.7 mm, 34.8 mm, and CW 34.8 mm respectively) ( Daniels and Bayliss, 2012; Phiri and Daniels, 2013; Daniels et al., 2014). The same cannot be said of the fingers of the chelipeds of P. gorongosa new species, because although its major cheliped is enlarged in comparison with the minor cheliped ( Fig. 2A, B View Figure 2 ), the major cheliped still lacks the dramatically curving dactylus and wide oval interspace enclosed by the closed fingers of adult males of P. mulanjeensis , P. mutareensis , and P. flavusjo (see Daniels and Bayliss, 2012; Phiri and Daniels, 2013; Daniels et al., 2014).

Potamonautes gorongosa View in CoL new species, is referred to as “ Potamonautes sp. 2 ” in Daniels et al. (2015, table 1, fig. 2). Phylogenetically, P.gorongosa View in CoL , new species, was found to be distinct from all other species in the large Afrotropical genus Potamonautes View in CoL based on mtDNA and nDNA evidence, and it is most closely related to several species that share the same lineage (“Clade 3” in Daniels et al., 2015, fig. 2) such as P. mutareensis View in CoL (from Zimbabwe, misspelt as “ P.mutariensis ” in Daniels et al., 2015: table 1 and fig. 2), P. mulanjeensis View in CoL (from Malawi), and P. flavusjo View in CoL (from South Africa). The G1 terminal article of P. gorongosa View in CoL new species closely resembles that of all three of these species (straight basally, medially curving outward at a 60° angle to the longitudinal axis of gonopod, and ending in a pointed and distinctly upturned tip) and it would be difficult to distinguish these taxa on this character alone. Fortunately, P. gorongosa View in CoL new species, can be distinguished from P. mutareensis View in CoL as follows ( Phiri and Daniels, 2013): the vertical sulcus of the ischium of the third maxilliped is absent (vs. deep in P. mutareensis View in CoL ), the anterolateral margin of the carapace is smooth (vs. granulated in P. mutareensis View in CoL ), and s3/s4 is deep at edges, faint in the middle, and does not meet the tip of the sternoabdominal cavity (vs. complete, deep and meeting the tip of the sternoabdominal cavity in P. mutareensis View in CoL ). Potamonautes gorongosa View in CoL , new species, can be distinguished from P. mulanjeensis View in CoL as follows ( Daniels and Bayliss, 2012): the vertical sulcus of the ischium of the third maxilliped is absent (vs. distinct in P.mulanjeensis View in CoL ), and s3/s4 is incomplete and deep only at the margins (vs. complete and deep throughout in P. mulanjeensis View in CoL ). Potamonautes gorongosa View in CoL , new species, can be distinguished from P. flavusjo View in CoL as follows ( Daniels et al., 2014): the vertical sulcus of the ischium of the third maxilliped is absent (vs. distinct in P. flavusjo View in CoL ) and s3/s4 is incomplete and deep only at the margins (vs. complete and deep throughout in P. flavusjo View in CoL ).

Potamonautes gorongosa View in CoL , new species, is easily distinguished from other species of freshwater crabs found in Mozambique ( P.namuliensis View in CoL , P. bellarussus View in CoL , P. calcaratus View in CoL , and P.obesus View in CoL ) both phylogenetically( Daniels et al., 2015, fig. 2) because all are in different lineages from P. gorongosa View in CoL , and morphologically ( Reed and Cumberlidge, 2004; 2006; Daniels and Bayliss, 2012; Daniels et al., 2014). For example, P. gorongosa View in CoL , new species, can be distinguished from P. calcaratus View in CoL and P. obesus View in CoL from Mozambique as follows ( Reed and Cumberlidge, 2004): the carapace is of medium height in the stream-living P. gorongosa View in CoL ( CH /FW = 1.1) (vs. highly vaulted in the semi-terrestrial burrowing crabs P. calcaratus View in CoL and P. obesus, CH View in CoL /FW = 1.2 and 1.3 respectively), and the dactylus of the major cheliped is slim and arched (vs. broadly flattened and high, an adaptation for burrowing in P. calcaratus View in CoL and P.obesus View in CoL ), and the anterolateral margin of the carapace is smooth (vs. armed with a small sharp single spine in P.calcaratus View in CoL and P.obesus View in CoL ). Potamonautes gorongosa View in CoL , new species, can be distinguished from P.bellarussus View in CoL as follows ( Daniels et al., 2014): the anterolateral margin of the carapace is smooth (vs. granulated in P. bellarussus View in CoL ), the exorbital tooth is small (vs. large and prominent in P.bellarussus View in CoL ), and the carapace is of medium height ( CH /FW = 1.1) (vs. flattened in P. bellarussus CH View in CoL /FW = 0.97). Finally, P. gorongosa View in CoL , new species, can be distinguished from P. namuliensis View in CoL as follows ( Daniels and Bayliss, 2012): thoracic sternal sulcus s3/s4 is incomplete and deep only at the margins (vs. complete and deep throughout in P. namuliensis View in CoL ), the postfrontal crest is incomplete but distinct (vs. very faint throughout in P. namuliensis View in CoL ), the dactylus and propodus of the cheliped are slightly arched with several large and medium sized teeth (vs. highly arched and lacking any conspicuous teeth in P. namuliensis View in CoL ), and the tip of the G1 terminal article is curved upward (vs. a straight uncurved tip in P. namuliensis View in CoL ).