ANEWSPECIESOF FRESHWATERCRAB(DECAPODA, POTAMONAUTIDAE)FROM THE SWAMPFORESTSOF KWAZULU-NATAL,SOUTHAFRICA:BIOCHEMICAL AND MORPHOLOGICALEVIDENCE

BY

GAVIN GOUWS1,3/,BARBARA A.STEWART 1/ andP ATRICK E.REAVELL 2/ 1/ Departmentof Zoology,University of Stellenbosch, Private Bag X1, Matieland 7602, SouthAfrica 2/ Departmentof Botany,University of Zululand, Private Bag X1001, KwaDlangezwa 3886, SouthAfrica

ABSTRACT Potamonautidriver crabs were collected from Ž velocalities in northeastern KwaZulu-Natal to determinebiochemical and morphological differentiation among these populations. T wodistinct formswere included in these collections. One of the forms could be identiŽ ed as Potamonautes sidneyi,whereasthe other was previously unknown. Biochemical analysis of 21 presumptive allozymeloci showed the two forms to be distinct,separating at a geneticidentity value of 0.829.A Žxedallele difference at the HEX locusin the sympatric populations of the two forms indicated that theywere reproductively isolated. Morphometric analysis of sevencarapace variables, by means of adiscriminantfunction analysis, showed the two forms to be distinct. The unidentiŽ ed form,which appearsto beconŽned to patches of swamp forest in northeastern KwaZulu-Natal, is described in thispaper as Potamonauteslividus sp. nov.

RÉSUMÉ Descrabes de riviè re du genre Potamonautes onté téré colté s danscinq localité s dela ré gion nord-orientaledu KwaZulu-NatalaŽ n dedé terminer les diffé rences biochimiques et morphologiques entreles diffé rentes populations. Deux formes distinctes é taientpré sentes dans ces ré coltes. L ’une deces formes a puê treidentiŽ é ecomme Potamonautessidneyi ,tandisque l’ autreé taitinconnue jusqu’à présent. L ’analysebiochimique de 21locienzymatiques a montréque les deux formes é taient distinctes,sé paré es par une valeur d’ identité gé né tique de 0,829. Une diffé rence allé lique Ž xeau locusHEX dansles populations sympatriques des deux formes indique qu’ ils sont isolé s dupointde vuereproductif. L ’analysemorphomé trique de septvariables de lacarapace,au moyend’ uneanalyse discriminante,a montréque les deux formes é taientdistinctes. La forme non-identiŽ ée, quiapparaî t conŽné e àdespans de forê t marécageuse au nord-est du KwaZulu-Natal, est dé crite dans ce travail comme Potamonauteslividus sp. nov.

3/ e-mail:[email protected] c KoninklijkeBrill NV ,Leiden,2001 Crustaceana 74(2):137-160 ° 138 G.GOUWS,B. A.STEWART& P.E.REAVELL

INTRODUCTION

Freshwater crabs ofthe family PotamonautidaeBott, 1970are commonthrough- outthe rivers ofKwaZulu-Natal,South Africa. Of the three species documented fromthe province(Barnard, 1935, 1950), two, Potamonautessidneyi Rathbun, 1904 and Potamonautesdentatus Stewart, Coke& Cook,1995, are knownto occur fromthe low-lyingmidlands to the coast. Theearliest recordsof Potamonautessidneyi fromthe rivers ofthe provincedate backto 1910.Stebbing (1910) documented collections madeat Port Natal, Lenz (1912)referred to collections madeat LakeSibayi and elsewhere inZululand, andBarnard (1935) reported collections inthe TransvaalMuseum, made at Oliviershoek,in the northernDrakensberg. Potamonautesdentatus ,however,has onlyrecently beendescribed from the MgeniRiver, Inyamvubu River, and other tributaries ofthe TugelaRiver (Stewart et al., 1995). Collections madenear Empangeni and Richards Bayrevealed specimens that couldnot be identiŽed as anyof the species knownfrom the provinceof KwaZulu- Natal. Thespecimens werecharacterized byhaving a highlyvaulted carapace; amedially reducedpostfrontal crest; inated, arched chelipeds; adownward projectingfrontal lobe; rounded,downward sloping epibranchial corners; and acharacteristic, silver-blue carapacesheen and bright orange to redchelipeds andpereopods. The specimens appearto exclusively inhabit small patches of swampforest andassociated herbaceouswetland, with characteristic swampforest vegetationassemblages (Wessels, 1997)and spongy peat-soil, inwhich these crabs formshallow, U-shaped burrows, partly Žlled with water.The unique morphologicalcharacteristics andhabitat requirements ofthis formraised the questionwhether it couldbe delineated as aspecies, separate tothose previously knownfrom the province. This paperprovides empirical morphologicaland biochemical evidencefor a newspecies ofpotamonautid river crabfrom the swampforests ofnortheastern KwaZulu-Natal,described as Potamonauteslividus sp.nov .Results are discussed against the broaderevidence of variation anddifferentiation within the genus Potamonautes andthe putative newspecies is comparedto species knownfrom SouthAfrica andfurther aŽ eld.

MATERIALS AND METHODS

Collection. —Crabs werecollected fromŽ velocalities (Žg. 1),using handnets baited withox-heart. Individuals of the undescribedform (form A) wereeasily identiŽable in the Želd dueto the muchin ated carapace,downward projecting