Potamonautes kantsyore, Cumberlidge & Clark, 2017

Cumberlidge, Neil & Clark, Paul F., 2017, Description of three new species of Potamonautes MacLeay, 1838 from the Lake Victoria region in southern Uganda, East Africa (Brachyura: Potamoidea: Potamonautidae), European Journal of Taxonomy 371, pp. 1-19 : 10-13

Potamonautes kantsyore sp. nov.

urn:lsid:zoobank.org:act:8EB2261D-E474-4809-B415-382269BF354E Figs 3 A–B, 4C, 5E–F, 6C, F, 7; Tables 1 , 3 Diagnosis

Carapace of medium height ( CH /FW 1.2; Fig. 3B ); exorbital tooth low, blunt, epibranchial tooth reduced to granule, postfrontal crest complete, faint medially, lateral ends well defined, meeting epibranchial teeth; anterolateral margin posterior to epibranchial tooth finely serrate, almost smooth ( Fig. 3A ); carapace sidewall vertical sulcus meeting anterolateral margin ( Fig. 3B ). Third maxilliped ischium with vertical sulcus ( Fig. 3B ); s3/s4 not visible except for two short deep notches at edges ( Fig. 3B ). Inferior margins of merus of cheliped with series of small granules, distal tooth pointed; cheliped carpus distal tooth large, pointed, proximal tooth small, one-third as large as distal tooth ( Fig. 3B ). Fixed finger (propodus) of major cheliped of adult male with large teeth along cutting edges, largest molars proximal, movable finger (dactylus) cutting edge with only small even granules, dactylus not arched, encompassing long narrow interspace when closed ( Fig. 5F ). G1 terminal article straight, directed outward at 45° angle to longitudinal axis of subterminal segment, curving outward throughout, tip slightly upturned ( Fig. 6C, F ).

Etymology

The new species is named for Kantsyore Island, which is located in the Kagera River (where it is about 130 m wide) at a locality that is about 120 km west of the point where the river enters Lake Victoria. The name is used as a noun in apposition. Vernacular name: the Kantsyore Island crab.

Material examined

Holotype (here designated)

UGANDA: adult ♂, CW 16.8, CL 11.6, CH 5.5, FW 4.6 mm, Ankole , Mbarara District , Kantsyore (Toni Nuti’s) Island, in the Kagara River, 12.9 km E of Kikagati, - 1.04216°S, 30.67056°E, 1280 m a.s.l., 19–20 Aug. 1967, J.S. Williams leg. ( NHMUK 2017.29 ).

Paratypes

UGANDA: 1 adult ♂, CW 15.6, CL 11.6, CH 5.5, FW 4.6 mm, same collection data as for holotype ( NHMUK 2017.30); 4 adult ♀♀ (CWs 16.1, 15.7, 15.5, 15.3), 1 subadult ♀ ( CW 14.2), 1 subadult ♂ (CW 13.2 mm), same collection data as for holotype ( NHMUK 2017.31–36).

Description

Carapace of medium height ( CH /FW 1.2; Fig. 3B ); front broad, measuring one-third CW (FW/CW 0.3; Fig. 3A ). Semi-circular, urogastric, cardiac, posterior and cervical carapace grooves all faint. Postfrontal crest complete, faint, lateral ends well defined, meeting epibranchial teeth; exorbital tooth low, blunt. Epigastric crests faint, median sulcus between crests short, forked posteriorly. Epibranchial tooth reduced to granule; anterolateral margin between exorbital, epibranchial teeth smooth, curving slightly outward, lacking intermediate tooth; anterolateral margin posterior to epibranchial tooth finely serrate, almost smooth ( Fig. 3A ); carapace sidewall vertical sulcus faint, incomplete, beginning at longitudinal sulcus, not meeting anterolateral margin, dividing sidewall into three parts ( Fig. 4C ). Suborbital margin granulated ( Fig. 4C ). Third maxilliped exopod with long flagellum, ischium with faint vertical sulcus ( Fig. 4C ). Epistomial tooth large, triangular, edges lined by large, round granules ( Fig. 4C ). Mandibular palp 2-segmented; terminal segment simple, s2/s3 deep, completely crossing sternum; s3/s4 not visible except for 2 short, deep notches at edges; margins of s4 flat, not raised; s4/e4, s5/e5, s6/e6 and s7/e7 all faint. Inferior margins of merus of cheliped with series of small granules, distal tooth pointed; two teeth on inner margin of cheliped carpus, both small, pointed; superior surface of merus granulated ( Fig. 3B ). Fixed finger (propodus) of major cheliped of adult male with large teeth along cutting edges, largest molars proximal, movable finger (dactylus) cutting edge with only small, even granules, dactylus not arched, encompassing long narrow interspace when closed ( Fig. 5 E–F). Pleon outline broadly triangular, with straight edges ( Fig. 3B ). G1 terminal article straight, directed outward at 45° angle to longitudinal axis of subterminal segment, with slightly upturned tip ( Fig. 6C, F ). G2 terminal article long (0.5 × length of G2), flagellum-like.

SIZE. Small species, adult size range between CW 15.3 and 16.8 mm.

COLOUR. Preserved specimens uniformly light brown.

Distribution

This species is known from only a single locality on Kantsyore Island in the Kagara River, 12.9 km east of Kikagati, where the river forms the border between Uganda and Tanzania ( Fig. 7 ).

Ecology

This river-living species was captured on Kantsyore Island in the Kagera River (water temperature 20–24°C) from between tree roots using meat as bait. The new species was collected in the same stretch of river as P. niloticus , a large-bodied, widely distributed species found throughout the Nile River basin ( Cumberlidge 2009; Cumberlidge & Clark 2010 b).

Conservation status

An IUCN extinction risk assessment of Potamonautes kantsyore sp. nov. has not yet been carried out, but given the fact that this species is known for only a few specimens from a single locality, it would probably be regarded as Data Deficient.

Remarks

Potamonautes kantsyore sp. nov. is superficially similar to several other species in this genus that share the following characters: reduced or absent exorbital and epibranchial teeth; a smooth anterolateral margin immediately behind the epibranchial tooth; and a thoracic sternum with a s3/s4 which is incomplete and deep at the sides but faint or absent in the middle. Ugandan crabs that share this suite of characters include P. rukwanzi , P. williamsi , P. mutandensis , P. morotoensis and P. imatongensis . Potamonautes emini (Hilgendorf, 1892) , from a geographically close locality in northwestern Tanzania, was also compared.

Potamonautes kantsyore sp. nov. can be distinguished from P. rukwanzi by the distal tooth on the cheliped merus, which is large, sharp and pointed in P. kantsyore sp. nov. ( Fig. 3B ) (vs small, blunt and low in P. rukwanzi ). Potamonautes kantsyore sp. nov. differs from P. willliamsi , P. mutandensis , P. morotoensis and P. imatongensis in that the proximal tooth on the inner margin of the cheliped carpus of P. kantsyore sp. nov. is pointed and almost as large as the distal tooth ( Fig. 3A ) (vs a weak, low and blunt proximal tooth in the other species) and the ischium of the third maxilliped is smooth in P.kantsyore sp. nov. ( Fig. 3B ) (vs with a distinct vertical sulcus in the other species). Potamonautes kantsyore sp. nov. is superficially similar to P. emini from northwest Tanzania ( Reed & Cumberlidge 2006) in that both are small species and both have smooth carapace margins. The most important differences between these two species are that the postfrontal crest is weak in P. kantsyore sp. nov. (vs distinct in P. emini ) and the ischium of the third maxilliped has a faint vertical sulcus in P. kantsyore sp. nov. (vs smooth in P. emini ) ( Bott 1955: pl. XIV, figs 1a–d; Reed & Cumberlidge 2006; Meyer & Cumberlidge 2011). Potamonautes kantsyore sp. nov. can be distinguished from P. entebbe sp. nov. by examination of s3/s4, which is almost completely absent except for two short notches on the external margins of the sternite ( Fig. 3B ) (vs deep at the edges and faint in the middle in P. entebbe sp. nov., Fig. 1B ). Finally, P. kantsyore sp. nov. can be distinguished from P. busungwe sp. nov. by examination of the ischium of the third maxilliped, which has a faint vertical sulcus ( Fig. 3B ) (vs smooth in P. busungwe sp. nov.; Fig. 2B ).

Figures

Fig. 3. Potamonautes kantsyore sp. nov. from Kantsyore Island in the Kagera River, southern Uganda. A–B. Holotype, adult ♂, CW 16.8 mm, (NHMUK 2017.29). A. Whole animal, dorsal view. B. Whole animal, ventral view. C. Paratype, adult ♀, CW 16.1 mm, (NHMUK 2017.33), whole animal, ventral view. Scale bars: A–B = 6.1 mm; C = 6.4 mm.

Fig. 5. Frontal view of left and right chelipeds. A–B. Potamonautes entebbe sp. nov., holotype, adult ♂, CW 35 mm, from Entebbe in southern Uganda (NHMUK 1955.11.8.26). – C–D. Potamonautes busungwe sp. nov., holotype, adult ♂, CW 21.5 mm, from Entebbe in southern Uganda (NHMUK 2017.37). – E–F. Potamonautes kantsyore sp. nov., holotype, adult ♂, CW 16.8 mm, from Kantsyore Island in the Kagera River in southern Uganda (NHMUK 2017.29). Scale bar: A–B = 2.3 mm; C–D = 3.1 mm; E–F = 3.3 mm. Photographs A–D by Phillip Crabb, NHMUK.

Fig. 6. G1, ventral view (A–C) and dorsal view (D–F). A, D. Potamonautes entebbe sp. nov., holotype, adult ♂, CW 35 mm, from Entebbe, southern Uganda (NHMUK 1955.11.8.26). – B, E. P. busungwe sp. nov., holotype, adult ♂, CW 21.5 mm, from Busungwe Island, Lake Victoria (NHMUK 2017.37). – C, F. P. kantsyore sp. nov., holotype, adult ♂, CW 16.8 mm, from Kantsyore Island in the Kagera River, southern Uganda (NHMUK 2017.29). Scale bars: A, D = 2.3 mm; B, E = 3.1 mm; C, F = 3.3 mm.

Fig. 4. Frontal view of carapace. A. Potamonautes entebbe sp. nov., holotype, adult ♂, CW 35 mm, from Entebbe, Lake Victoria, southern Uganda (NHMUK 1955.11.8.26). – B. P. busungwe sp. nov., holotype, adult ♂, CW 21.5 mm, from Busungwe Island, Lake Victoria,, southern Uganda (NHMUK 2017.37). – C. P. kantsyore sp. nov., holotype, adult ♂, CW 16.8 mm, from Kantsyore Island in the Kagera River, southern Uganda (NHMUK 2017.29). Scale bars: A = 2.34 mm; B = 3.1 mm; C = 3.3 mm. Photographs A–B by Phillip Crabb, NHMUK.

Fig. 7. Distribution map showing the known localities of Potamonautes entebbe sp. nov. (black triangle), P. busungwe sp. nov. (black circle) and P. kantsyore sp. nov. (black star) in Uganda, East Africa. For exact localities, see text.

Fig. 1. Potamonautes entebbe sp. nov., holotype, adult ♂, CW 35 mm, from Entebbe, southern Uganda (NHMUK 1955.11.8.26). A. Whole animal, dorsal view. B. Whole animal, ventral view. Scale bars: 6.3 mm. Photographs by Phillip Crabb, NHMUK.

Fig. 2. Potamonautes busungwe sp. nov, holotype, adult ♂, CW 15.9 mm, from Busungwe Island, Lake Victoria, southern Uganda (NHMUK 2017.37). A. Whole animal, dorsal view. B. Whole animal, ventral view. Scale bars: 6.3 mm. Photographs by Phillip Crabb, NHMUK.