Potamonautes kivu, Cumberlidge & Clark, 2018

Cumberlidge, Neil & Clark, Paul F., 2018, Albertine Rift Valley endemics: three new species of freshwater crabs (Brachyura: Potamoidea: Potamonautidae) from Uganda, the Democratic Republic of the Congo, and Rwanda, Journal of Natural History 52 (25 - 26), pp. 1637-1656 : 1649-1651

publication ID

https://doi.org/ 10.1080/00222933.2018.1480812

publication LSID

lsid:zoobank.org:pub:FC681BD6-6FB2-4A14-B068-89FC3EB26605

persistent identifier

https://treatment.plazi.org/id/4F58C651-FF96-634E-FDEC-2A73B630F9A1

treatment provided by

Felipe

scientific name

Potamonautes kivu
status

 

Potamonautes kivu

( Figures 2a,b View Figure 2 , 4b View Figure 4 , 5b,e View Figure 5 , 6b,e, 7b View Figure 7 , 8b View Figure 8 )

Material examined

Type material. Rwanda. Holotype (here designated): adult ♂, CW 24.9 , CL 18.7 , CH 7.8 , FW 7.8 mm, from Gisenyi , Lake Kivu, − 1.698122°S, 29.251734°E, 1471 m asl ( NHMUK reg. 2018. 5, formerly NMU TRW August 1972), coll GoogleMaps . A GoogleMaps .G. Goodall, 1972. Paratypes: two adult ♀♀ CW 18.3 , CL 13.0, CH 7.2 , FW 6.9 (ovigerous), CW 15.5 , CL 12.4 , CH 6.3 , FW 5.5 ; two subadult ♀♀ (both with widened pleon incompletely covering sternum) CW 14.8 , CL 11.7 , CH 5.5 , FW 5.5 ; CW 14.0, CL 10.4 , CH 5.0, FW 5.0; two juvenile ♀♀ (both with slim pleon) CW 10.5 , CL 8.5 , CH 4.5 , FW 4.5 ; CW 10.2 , CL 7.6 , CH 4.0, FW 4.0; subadult ♂ CW 15.1 , CL 10 , CH 4.8 , FW 4.8 ; all same data as holotype ( NHMUK reg. 2018. 98 – 104) GoogleMaps .

Other material. Rwanda. Potamonautes sp. (not P. kivu . sp. nov.): juvenile ♂ (both chelipeds and both gonopods small and under-developed) CW 19.6, CL 15.3, CH 5.4, FW 6.8 mm, from Gisenyi, Lake Kivu, − 1.698122°S, 29.251734°E ( NHMUK reg. 2018.105, formerly NMU TRW 1972.08), coll. A.G. Goodall, 1972.

Diagnosis

Based on holotype (adult ♂ CW 19.8). Carapace: postfrontal crest faint, lateral ends meeting anterolateral margins; epigastric crests rounded, distinctly raised; exorbital, epibranchial teeth each reduced to granule; anterolateral margin posterior to epibranchial tooth smooth ( Figures 1b View Figure 1 , 4b View Figure 4 ). Third maxilliped: ischium with very faint shallow vertical sulcus ( Figures 1b View Figure 1 , 4b View Figure 4 ); s3/s4 incomplete, comprising two short shallow grooves on lateral margins, otherwise smooth; margins of s4 low, not raised ( Figure 1b View Figure 1 ). Cheliped: dactylus (moveable finger) slim, arched, enclosing oval interspace, teeth medium, small; propodus (fixed finger) with medium, small teeth; carpus distal tooth low, broadly triangular, proximal tooth small, low ( Figure 5b View Figure 5 ); merus lined by series of small granules, distal meral tooth small, pointed. G1: terminal article directed outwards, proximal third straight in line with longitudinal axis of subterminal segment, median part directed outwards at 45°, widened by raised rounded ventral lobe ( Figure 6e), tip curving sharply upwards ( Figure 6b,e).

Description

Based on holotype (adult ♂ CW 19.8 mm). Carapace: outline transversely oval, medium height ( CH /FW 1.0), front broad measuring one-third CW (FW/CW 0.33); postfrontal crest faint, lateral ends meeting epibranchial teeth; epigastric crests rounded, distinctly raised, median sulcus between crests short, forked posteriorly; semi-circular, urogastric, cardiac, posterior, cervical carapace grooves all distinct, shallow. Exorbital, epibranchial teeth each reduced to granule; anterolateral margin between exorbital, epibranchial teeth with small granules, lacking intermediate tooth; anterolateral margin posterior to epibranchial tooth smooth ( Figure 1b View Figure 1 ); suborbital margin faintly granular; vertical sulcus on carapace branchiostegal wall faint, meeting longitudinal sulcus, dividing carapace wall into three parts. Third maxilliped: exopod with long flagellum, ischium with faint shallow vertical sulcus ( Figures 2b View Figure 2 , 4b View Figure 4 ). Epistomial tooth large, triangular, margins lined by granules ( Figure 2b View Figure 2 ). Mandible: palp two-segmented; terminal segment simple. Sternum: s2/s3 deep, running horizontally across sternum; s3/s4 incomplete, comprising two short shallow grooves on lateral margins, otherwise smooth; margins of s4 low, not raised; s4/e4, s5/e5, s6/e6, s7/e7 grooves all either faint or not visible ( Figure 2b View Figure 2 ). Cheliped: dactylus (movable finger) slim, arched, enclosing oval interspace, teeth medium, small; tip of dactylus overlapping tip of propodus (fixed finger); propodus with medium, small teeth ( Figure 5b View Figure 5 ); carpus distal tooth pointed, triangular, proximal tooth small, low ( Figure 5e View Figure 5 ); merus lined by series of small teeth, distal meral tooth larger, pointed. Pleon: outline broadly triangular with straight margins. G1: terminal article directed outward, proximal third directed outwards at 45° to longitudinal axis of subterminal segment, median part widened by raised rounded ventral lobe ( Figure 6e), tip curving sharply upwards ( Figure 6b,e). G2: terminal article long, flagellum-like ( Figure 7b View Figure 7 ). Small-sized species, adult at CW 15.5 mm.

Distribution

This species is known only from three specimens collected from a single locality near the town of Gisenyi on the shores of Lake Kivu in Rwanda ( Figure 8b View Figure 8 ) .

Type locality

The type locality is Lake Kivu at Gisenyi, Rwanda (− 1.698122°S, 29.251734°E; Figure 8b View Figure 8 ) GoogleMaps .

Conservation status

An IUCN conservation assessment of P. kivu sp. nov. has not yet been carried out, but given the fact that this species is known from only three specimens from a single locality, and no specific threats are known, it would probably be regarded as Data Deficient. In addition, this species is not found in a protected area.

Etymology

The new species is named for Lake Kivu, Rwanda in the Albertine Rift Valley, where this species was first collected. The specific epithet kivu is used as a Latin noun in apposition. The vernacular name is the Kivu crab.

Ecology

Lake Kivu (1463 m asl) is a small (100 km long by 50 km wide), deep lake (480 m) situated in the Western Rift Valley as part of the Albertine Rift which is divided by the border between the DRC and Rwanda, with the large Idjwi Island in Lake Kivu lying in the DRC. Lake Kivu now drains southwards into Lake Tanganyika via the River Ruzizi (but historically Lake Kivu drained north into Lake Rutanzige before being blocked by volcanic activity in the mid-Pleistocene; Worthington and Lowe- McConnell 1994). Little is known about the habitat and ecology of P. kivu sp. nov. Lake Kivu is part of Lake Victoria Basin Freshwater Ecoregion 521 ( Thieme et al. 2005; Abell et al. 2008). Four other species of freshwater crabs are known from Lake Kivu ( Cumberlidge and Meyer 2011); two are endemic ( P. idjwiensis and P. bourgaultae ) and two ( P. lirrangensis and P. mutandensis ) have a wider distribution. Potamonautes kivu sp. nov. is the fifth species known to occur in this lake.

Remarks

Potamonautes kivu sp. nov. differs from other, similar small-bodied species of freshwater crabs from the Albertine Rift Valley and other parts of Uganda in that s3/s4 is reduced to two short faint shallow sulci at the margins ( Figure 2b View Figure 2 ) (vs two long deep sulci at the margins in P. amalerensis , P. busungwe , P. bwindi sp. nov., P. entebbe , P. imatongensis , P. loveni , P. rwenzori sp. nov., P. morotoensis , P. mutandensis and P. rukwanzi ; Corace et al. 2001; Cumberlidge and Clark 2010a, 2010b, 2016, 2017; Cumberlidge and Meyer 2011); the third maxilliped ischium is smooth and lacks a sulcus ( Figure 4b View Figure 4 ) (vs an ischium with a distinct vertical sulcus in P. aloysiisabaudiae , P. emini ( Hilgendorf, 1892) , P. loveni , P. mutandensis , P. rukwanzi , P. rwenzori and P. williamsi ); and the tip of the G1 terminal article curves sharply upwards ( Figure 6b,e) (vs a G1 terminal article whose tip is either straight or only slightly upturned in P. amalerensis , P. busungwe , P. elgonensis , P. entebbe , P. imatongensis , P. loveni and P. morotoensis ; Cumberlidge and Clark 2010a, 2010b, 2016, 2017; Cumberlidge and Meyer 2011).

It is of interest that a small juvenile male belonging to an unidentified species of Potamonautes ( NHMUK reg. 2018.105, formerly NMU TRW 1972.08 ) was also collected from Lake Kivu together with the holotype and paratypes of P . kivu sp. nov. described here. Although it was not possible for us to identify this specimen, it is clear from its undeveloped abdomen, gonopods and chelipeds at CW 19.6 mm that it belongs to a much larger species than P . kivu sp. nov. (one which would be adult at this size). Furthermore, the cheliped and carapace characters of the unidentified specimen (although under-developed) indicate that it does not belong to P. lirrangensis , the only species known to occur in Lake Kivu that grows to a large size (cf. Cumberlidge and Meyer 2011).

NHMUK

Natural History Museum, London

CH

Circulo Herpetologico de Panama