Tadzocrangonyx alaicus, Sidorov & Hou & Sket, 2018

Sidorov, Dmitry, Hou, Zhonge & Sket, Boris, 2018, Three new remarkable amphipod species (Crustacea: Gammaridae) from springs and subterranean waters of Central Asia, Zootaxa 4444 (4), pp. 437-461 : 453-458

Tadzocrangonyx alaicus , sp. n.

FIGURES 1D , 12–15

Material examined. HOLOTYPE SPEcImEn NC189: FEmALE, 4.5 mm, OOSTEGITES WEAKLY DEVELOPED, nOn-SETOSE; KYZYL BULAK SPRInG, 40.062972, 71.723139, 1155 m A.S.L., KYZYL BULAK, KADAmjAY DISTRIcT, BATKEn REGIOn, KYRGYZSTAn , LEG. 10 JUnE 2012 bY B. SKET. PARATYPES NC190-NC193: 3 FEmALES, 5.2 mm, cA. 5.0 mm, 4.0 mm, OOSTEGITES WEAKLY DEVELOPED, nOn-SETOSE, 1 PRObAbLE mALE, 4.2 mm; SAmE DATA AS HOLOTYPE .

OTHER SPEcImEnS EXAmInED FROm THE SAmE LOcALITY (nOT IncLUDED In THE TYPE SERIES): NC194-NC203: 1 FEmALE (4.2 mm, FRAGmEnT), 3 (SEX UnKnOWn) FRAGmEnTS, 6 jUVEnILES 2.5-3.0 mm. PARTIALLY DISSEcTED, mEASURED AnD DEPOSITED AT THE RESEARcH cOLLEcTIOn OF THE ODDELEK ZA bIOLOGIjO, BIOTEHnIšKA FAKULTETA, UnIVERZA V LjUbLjAnI.

Diagnosis. SmALL, EYELESS, PIGmEnTLESS cRAnGOnYcTID SHAPED AmPHIPOD WITHOUT STERnAL GILLS; TELSOn SHORT AnD DEEPLY SPLIT; mAnDIbULAR PALPUS nORmALLY DEVELOPED; cOXAL PLATES II–IV SHORT (SHALLOW) nOT LOnGER THAn WIDE; PROPODUS OF GnATHOPODS ARmED WITH 2 SPInES AT DEFInInG AnGLE; UROPODS I nOT REAcHInG TIPS OF II, UROPOD III EnDOPODITE ScALE-LIKE, EXOPODITE WITH WELL DEVELOPED DISTAL ARTIcLE.

GenBank accession number: MG655627 FOR ISOLATE 373TADZOcRKYR.

Etymology. SPEcIFIc EPITHET ' alaicus ' FOR THE ALAI MOUnTAInS WHERE THE SPEcImEnS WERE cOLLEcTED.

Description. GENERAL BODY MORPHOLOGY ( FIGS 1D , 12A, E, H , 15F ). Body DORSALLY WITH FEW FInE SETAE; PLEOn nOT ARmED DORSALLY; LEnGTH 4.5 mm. Head AS LOnG AS PEREOnITES I AnD II cOmbInED, ROSTRUm InDISTIncT, EYES (EYE PIGmEnTATIOn) AbSEnT. Epimeral plates I–III WITHOUT POST-VEnTRAL TEETH, ALTHOUGH PLATE II SLIGHTLY AcUmInATE, cORnERS bEARInG mInUTE SETA OR UnARmED; EPImERA WITHOUT VEnTRAL RObUST SETAE, POSTERIOR mARGInS SInUOUS AnD WITH 1 SETA OR nAKED. Urosomites I–III WITHOUT DORSAL cUTIcULAR ARmAmEnTS; EAcH ARmED WITH nOTcHED SPInES In THE FOLLOWInG mAnnER: 1–1 // 1–1 // 1–1. Telson : SHORTEnED, HALF SHORTER THAn UROPOD III PEDUncLE, LEnGTH HALF ITS WIDTH; EnTIRELY cLEFT; APIcES WITH 6 SHORT RObUST SETAE In A ROW AnD A PAIR OF SETULES DORSOLATERALLY. ANTENNAE ( FIGS 1D , 12A–D ). First antenna: LOnG, 0.7 bODY LEnGTH, APPROXImATELY 0.35 AS LOnG AS SEcOnD AnTEnnA; PEDUncULAR ARTIcLES I-III WITH A LEnGTH RATIO OF 1:0.6:0.5, ARTIcLES 1 AnD 2 WITH A FEW SETS OF SETAE On mEDIAL AnD VEnTRAL mARGInS, THE THIRD ARTIcLE bEARInG SPARSE SETAE; PRImARY FLAGELLUm WITH 21 UnIFORm, SPARSELY SETULATE ARTIcLES, LAncEOLATE AESTHETAScS PRESEnT On ARTIcLES 5-19; AccESSORY FLAGELLUm 2-ARTIcULATE, LOnGER THAn AccOmPAnYInG PRImARY FLAGELLAR ARTIcLE. Second antenna: LEnGTH AbOUT 0.35 bODY, PEDUncLE LEnGTH 1.3 FLAGELLUm; PEDUncULAR ARTIcLES 4 AnD 5 In LEnGTH RATIO 1:0.9, bOTH SETOSE WITH STIFF nOTcHED SETAE ALOnG VEnTRAL AnD DORSAL FAcES, ARTIcLE 4 bEARInG bUnDLE OF STIFF SImPLE SETAE On ITS VEnTRO-DISTAL cORnER; GLAnD cOnE SOmEWHAT TAPERED; cALcEOLI AbSEnT; FLAGELLUm WITH 12 WEAKLY SETATE ARTIcLES, 8 DISTAL OF THEm WITH SInGLE ROD-LIKE AESTHETASc EAcH. MOUTH PARTS ( FIGS 13A–I ). Upper lip ObLOnG, ROUnDED, WITH mInUTE SETAE AT APEX. MAnDIbLES SUbEqUAL, mAnDIbULAR bODY SmALL, SLIGHTLY cOmPRESSED. Left mandible: PALP ARTIcLE 2 LOnGER THAn ARTIcLE 3 (DISTAL), WITH 3 InnER mARGInAL SETAE, ARTIcLE 3 WEAKLY FALcATE, bEARInG 12 D-SETAE AnD 3 E-SETAE; IncISOR PROcESS WITH 7 TEETH; LAcInIA mObILIS WITH 6 TEETH AnD 4 STIFF PLUmOSE SETAE In A ROW. Right mandible: IncISOR PROcESS bEARInG 7 TEETH; LAcInIA mObILIS bIFID WITH FEW SETULES AnD 3 STIFF PLUmOSE SETAE In A ROW, mOLAR PROcESS WITH GRInDInG SURFAcE bEARInG LOnG POSTERIOR PLUmOSE SETA. Lower lip: OUTER LObES mODERATE, SLIGHTLY AnGULATED, DEnSELY SETOSE WITH SETULES; mAnDIbULAR PROcESS DISTIncT (nARROW); InnER LObES PRESEnT, VESTIGIAL. Maxilla I, PALPS A LITTLE ASYmmETRIcAL: LEFT maxilla: PALP LOnG AnD SLEnDER, ARTIcLE 1 HALF SHORTER THAn ARTIcLE 2 WITH 4 SHORT SPInES AnD 2 SImPLE RObUST SETAE On ITS APIcAL AnD SUb-APIcAL mARGIn; OUTER PLATE WITH 9 THIcK SPInES (2 bIDEnTATE, 7 mULTI-DEnTATE); InnER PLATE nARROW, WITH 4 PLUmOSE APIcAL SETAE; RIGHT maxilla I, PALP ARTIcLE 2 WITH 5 RObUST SETAE (1 OF THEm SERRATE) On APIcAL mARGIn. Maxilla II WITH bOTH PLATES nARROW, OUTER PLATE APIcAL mARGIn WITH 21 LOnG SImPLE SETAE In TWO ROWS; InnER PLATE WITH ObLIqUE ROW OF 7 PLUmOSE SETAE AnD bEARInG 25 LOnG SImPLE SETAE In TWO ROWS On APIcAL mARGIn. Maxilliped: InnER PLATE ObLOnG, nARROW, WITH 3 FORKED SUbTLE SPInES, 1 SImPLE SPInE AnD 2 nAKED SETAE APIcALLY, 11 PLUmOSE SETAE On InnER VEnTRAL FAcE; OUTER PLATE LOnG, SUb-OVOID, WITH A ROW OF 11 STROnG, KnIFELIKE SPInES AnD 3 PAPPOSE SETAE ALOnG OUTER mARGIn, AnD 10 STIFF SETAE SUb-mARGInALLY; mAXILLIPED PALP ARTIcLE 2 LInEAR, WITH A ROWS OF AbOUT 35 THIn SETAE ALOnG InnER VEnTRAL FAcE AnD 1 ELOnGATE APIcOLATERAL SETA; PALP ARTIcLE 3 nARROW, WITH SET OF 4 LOnG SETAE On OUTER mARGIn, 4 SETAE On InnER mARGIn, mEDIOVEnTRAL AREA WITH A ROW OF LOnG SImPLE SETAE (2 OF THEm STROnG, SERRATED); PALP ARTIcLE 4 (DISTAL), 0.3 SHORTER THAn PALP ARTIcLE 3, nAIL SLEnDER, bEARInG 6 SETAE AT ITS bASE. Lateralia WITH 12 STROnG, SImPLE SPInES AnD A ROW OF LOnG SETAE. COXAL PLATES, GILLS AND OOSTEGITES ( FIGS 1D , 14A, B , 15A–E ). Coxal plates I–IV OF DISSImILAR SHAPE, ROUGHLY SqUARE OR REcTAnGULAR, WITH A SPARSE ROW OF SHORT SETAE ALOnG VEnTRAL mARGIn OF EAcH; cOXAL PLATES V AnD VI WITH DISTIncT AnTERIOR LObES, POSTERIOR mARGIn SLIGHTLY nOTcHED bEARInG 1 SETA; cOXAL PLATE VII SmALLEST, SEmILUnAR, WITH 1 SETA On POSTERIOR mARGIn; EAcH PLATE II–VI bEARInG SInGLE, SAc-LIKE coxal gill WITH LOnG STALK. Sternal gills AbSEnT. Oostegites II–V nOT WELL DEVELOPED, ObLOnG, nARROW (nOT GAmmARID). GNATHOPODS ( FIGS 14A, B ). First gnathopod: bASIS WITH 1 LOnG AnD 4 SHORT SETAE On AnTERIOR AnD 3 LOnG SETAE On POSTERIOR mARGInS; cARPUS STOUT, POSTERIOR mARGIn WITH 2 SETAE AnD POSTERIOR AnGLE bEARInG 1 SETA, 2 GROUPS OF STIFF SETAE On VEnTRAL mARGIn, A ROW OF STIFF SETAE On InnER FAcE; PROPODUS SUb-TRAPEZOIDAL, LOnGER THAn WIDE, bEARInG 3 LOnG SETAE On AnTERIOR mARGIn, A GROUP OF 7 SETAE On AnTERO-DISTAL cORnER, 3 GROUPS OF STIFF SETAE On InnER FAcE AnD 3 GROUPS OF SETAE ALOnG POSTERIOR mARGIn, PALm AS LOnG AS POSTERIOR mARGIn, bEVELED, STRAIGHT WITH cUTTInG mARGIn SmOOTH, PALmAR mARGIn WITH 10 SHORT SETAE ALOnG OUTER AnD InnER FAcES, PALmAR AnGLE DEFInED AnD ARmED WITH 2 DISTALLYnOTcHED SPInES AccOmPAnIED WITH A GROUP OF LOnG SETAE On InnER FAcE; DAcTYLUS cREScEnT-SHAPED, nAIL LOnG, 0.37 OF TOTAL LEnGTH OF DAcTYLUS, 1 SETA ALOnG AnTERIOR mARGIn, InnER mARGIn SmOOTH, WITH A GROUP OF 3 mInUTE SETULES AT HInGE. Second gnathopod GEnERALLY SImILAR TO GnATHOPOD I, bUT A LITTLE LARGER; cARPUS FEEbLE, WITH 4 GROUPS OF STIFF SETAE On VEnTRAL mARGIn; PROPODUS AnD DAcTYLUS SUb-SImILAR TO THAT OF GnATHOPOD I. PEREOPODS ( FIGS 1D , 15A– E ): pereopods III AnD IV SUbEqUAL In LEnGTH, SOmEWHAT LOnGER THAn THE GnATHOPOD II, ARTIcLE IV bEARInG SHORT SETAE POSTERIORLY, ARTIcLES V AnD VI OF THIRD LEG bEARInG 1-1-1 AnD 2-2-2-1 POSTERIOR SPInES cORRESPOnDInGLY, AnD OF THE FOURTH LEG 1-1-1 AnD 1-2-2-1; pereopods V–VII SImILAR, SEcOnD ARTIcLES SLIGHTLY EXPAnDED POSTERIORLY, POSTERIOR mARGIn SERRATE WITH SHORT mARGInAL SETAE, POSTERIOR mARGInS OF PROPODI ARmED WITH nOTcHED SPInES EXcEPT ARTIcLES VI bEARInG LOnG SETAE, DAcTYLI III AnD IV WITH SInGLE FAcIAL PEnnATE SETULES, DAcTYLI V–VII WITH ADDITIOnAL FAcIAL SETULES. PLEOPODS AND UROPODS ( FIGS 12E–I , 15G–I ): pleopods EAcH WITH TWO RETInAcULA; PEDUncULAR ARTIcLES nAKED EXcEPT FOR 3 LOnG STIFF mEDIAL SETAE On THE THIRD; RAmI OF 8-7, 8-7, 7-6 ARTIcLES OF OUTER AnD InnER RESPEcTIVELY. Third uropod EXTEnDInG WELL bEYOnD UROPODS I AnD II In THE InTAcT bODY; UROPOD LEnGTHS RELATIVE TO UROPOD I; UROPOD II 0.8, UROPOD III 1.5; uropod I PEDUncLE LEnGTH 1.4 InnER AnD 1.6 OUTER RAmI, WITH 1 STROnG bASOFAcIAL SPInE, LATERAL mARGIn WITH A ROW OF 3 nOTcHED DORSAL SPInES, mEDIAL mARGIn bEARInG 2 STROnG nOTcHED SPInES; RAmI OF UnEqUAL LEnGTH, InnER RAmUS WITH 2 ROWS OF LATERAL SPInES, AnD 4 APIcAL nOTcHED SPInES; uropod II PEDUncLE 0.2 AS LOnG AS InnER RAmUS, WITH 2 SHORT DORSOLATERAL SPInES IncLUDInG 1 APIcAL SPInE, OUTER RAmUS SLIGHTLY SHORTER THAn InnER, InnER RAmUS WITH 3 mEDIOLATERAL SPInES, bOTH RAmI WITH 4 TERmInAL nOTcHED SPInES; uropod III PARVIRAmOUS, PEDUncLE AS LOnG AS UROSOmITE III, 0.3 LEnGTH OF OUTER RAmUS, bEARInG 3 FAcIAL AnD 5 VEnTRODISTAL nOTcHED SPInES, OUTER RAmUS TWO-ARTIcULATE, PROXImAL ARTIcLE WITH TRAnSVERSE ROW OF SPInES ARRAnGED mEDIALLY 3-3-3, LATERALLY nAKED, WITH 2 GROUPS OF 6-7 TERmInAL SPInES, DISTAL ARTIcLE SHORT, APPROXImATELY 0.38 PROXImAL, bEARInG 2 SPInES mEDIALLY AnD 2 SPInES AccOmPAnIED WITH FInE SETULES APIcALLY, InnER RAmUS VESTIGIAL, SHORT, 0.16 OUTER, WITH 1 APIcAL SPInE AnD 1 SETA OnLY.

Sexual dimorphism. OnE PRObAbLY mALE SPEcImEn WITH bODY LEnGTH 4.2 mm IS SImILAR TO FEmALE bUT WITH A SmALLER bODY SIZE AnD SLIGHTLY DIFFERInG In mORPHOLOGY OF GnATHOPODS (SEE FIGS 14C, D ).

Variability. THE EXAmInED SPEcImEnS HAVE An InSIGnIFIcAnT VARIATIOn In THE SHAPE OF EPImERAL PLATES AnD ARmORInG OF UROPOD 3.

Ecology and distribution. Tadzocrangonyx alaicus , sp. n. WAS FOUnD OnLY In THE PAmIR-ALAY mOUnTAIn SYSTEm, AT ELEVATIOn 1155 m A.S.L. OF THE nORTHERn FOOTHILLS OF THE ALAI RAnGE In A KARST SPRInG LOcATED In THE SHAKHImARDAn RIVER bASIn.

Remarks. AccORDInG TO mOLEcULAR AnALYSIS THIS AmPHIPOD bELOnGS TO GAmmARIDAE , AS THE mOST bASAL bRAncH OF THE Sarothrogammarus GROUP OF GEnERA (SKET & HOU, 2018). THE Sarothrogammarus GROUP HAS A DISjUncT DISTRIbUTIOn bETWEEn PAmIR PLATEAU FRESHWATERS AnD MEDITERRAnEAn SHORES; WHILE THE GEnUS Tadzocrangonyx IS LImITED TO CEnTRAL ASIA. THESE DISTRIbUTIOn PATTERnS mIGHT bE DRIVEn bY THE TETHYAn RETREAT (HOU ET AL., 2014). ALTHOUGH OF A cRAnGOnYcTID SHAPE, IT DIFFERS FROm cRAnGOnYcTIDS bY THE AbSEncE OF STERnAL GILLS AS WELL AS bY A DEEPLY SPLIT, nOn-cRAnGOnYcTID TELSOn . SIncE WE HAVE nO mOLEcULAR DATA AbOUT bOTH PREVIOUSLY DEScRIbED Tadzocrangonyx SPEcIES, THE TYPE T. schizurus ( BIRšTEjn, 1948) AnD T. setiferus (BIRSTEIn ET LjOVUScHKIn, 1972), OUR TAXOnOmIc DEcISIOn IS SUPPORTED bY GEOGRAPHIcAL POSITIOn bETWEEn bOTH AS WELL AS bY mORPHOLOGIcAL SImILARITY OF THREE SPEcIES.

THE mOST DISTURbInG cHARAcTER IS A WELL DEVELOPED TERmInAL ARTIcLE OF THE UROPOD III EXOPODITE, WHIcH IS mISSInG

AT bOTH PREVIOUS SPEcIES. HOWEVER, THIS IS nOT A PHYLOGEnETIcALLY STAbLE cHARAcTER. In THE RELATED GEnUS

Sarothrogammarus , THIS ARTIcLE mAY bE TWIcE THE LEnGTH OF SURROUnDInG SPInES In ATLAnTIc AnD MEDITERRAnEAn RELATIVES ( STOcK 1971), OR mORE THAn HALF SHORTER AnD nOT THIcKER THAn SURROUnDInG SPInES (In S. ruffoi KARAmAn, 1971), OR EVEn 'nOT VISIbLE (REDUcED)' (In S. asiaticus MARTYnOV, 1935). In THE LESS RELATED GEnUS Niphargus ScHIöDTE (FAm. NIPHARGIDAE ) THIS ARTIcLE mAY bE OF THE SAmE LEnGTH AS THE PROXImAL ARTIcLE, OR mUcH SHORTER, OR EVEn AbSEnT (In N. buturovici S. KARAmAn, 1958). IT IS AbSEnT ALSO In Haploginglymus SPP. WHIcH APPEARED TO bE mOLEcULARLY nESTED WITHIn Niphargus (SEE ALSO MOšKRIč, 2016). THUS, THE DIFFEREncE In THE UROPOD III DOES nOT PREVEnT THE nEW TAXOn OF bEInG A mEmbER OF THE SAmE PHYLOGEnETIc bRAncH, OF THE Sarothrogammarus GROUP AnD OF THE GEnUS Tadzocrangonyx .

THE SYSTEmATIcS OF THE CEnTRAL ASIAn SAROTHROGAmmARIDS, Sarothrogammarus , Comatogammarus , Barnardiorum AnD Tadzocrangonyx IS RATHER POORLY DEVELOPED AnD THEIR TAXOnOmIc RELATIOnSHIP IS cOnTROVERSIAL. NEVERTHELESS, In THE cOURSE OF THE cOmPARATIVE mORPHOLOGIcAL AnALYSIS WE DEcIDED THAT THE SUITE OF mORPHOLOGIcAL cHARAcTERS OF THE nEW SPEcIES mOST RESEmbLES Tadzocrangonyx (SEE KARAmAn & BARnARD 1979). TWO PREVIOUSLY DEScRIbED SPEcIES OF THE GEnUS Tadzocrangonyx KnOWn FROm THE CEnTRAL ASIA ARE RATHER DIFFEREnT FROm EAcH OTHER, ESSEnTIALLY DIFFERInG PRImARILY In THE STRUcTURE OF THE UROPOD III. BOTH SPEcIES SIGnIFIcAnTLY DIFFER bY ARmATURE OF bOTH GnATHOPODS AnD bY A SPEcIAL SHAPE OF TELSOn In T. alaicus , sp. n. (SEE TAbLE 1). MAXILLA II IS ALSO VERY DIFFEREnT WITH A VERY nARROW InnER PLATE. HOWEVER, FOR A nUmbER OF SIGnIFIcAnT FEATURES WE cOnSIDER THE nEW SPEcIES cLEARLY RELATES TO THE GEnUS Tadzocrangonyx : I.E., SHORTEnED cOXAL PLATES I–IV, SUb-SYmmETRIcAL PALPS OF mAXILLA I, STRUcTURE OF GnATHOPODS (PALm nOT ObLIqUE), UnmODIFIED PEREOPODS III AnD IV (SEE ALSO STOcK 1971). Tadzocrangonyx alaicus , sp. n. IS SIGnIFIcAnTLY DIFFEREnT FROm THE KnOWn SPEcIES OF Tadzocrangonyx AnD OTHER SAROTHROGAmmARIDS bY A qUITE UnIqUE STRUcTURE OF UROPOD III WITH THE RELATIVELY WELL DEVELOPED TERmInAL SEGmEnT OF THE EXOPODITE. WE mAY SUPPOSE THAT Tadzocrangonyx REPRESEnTS A STYGObIOTIc RELATIVE OF A mUcH DIVERSIFIED Sarothrogammarus -GROUP In THE REGIOn.

Figures

FIGURE 1. Habitus of examined specimens: (А) Gammarus troglomorphus, sp. n.; (B) Gammarus parvioculatus, sp. n.; (C) Gammarus cf. subaequalis-Garlyk; (D) Tadzocrangonyx alaicus, sp. n.

FIGURE 12. Tadzocrangonyx alaicus, sp. n., female, 4.5 mm, holotype NC189: (А) head; (C) antenna I, part; (D) antenna II; (E) urosome; (F) uropod I; (G) uropod II; (H) uropod III and telson, dorsal view; (I) uropod III, lateral view. Female, 5.0 mm, paratype NC190: (B) antenna I. Scale bars 0.2 mm.

FIGURE 13. Tadzocrangonyx alaicus, sp. n., female, 4.5 mm, holotype NC189: (А) mandible, left; (B) mandible, right; (C) maxilla I, left; (D) palp of maxilla I, right; (E) maxilla II; (F) lower lip; (G) upper lip; (H) maxilliped; (I) lateralia. Scale bars 0.2 mm.

FIGURE 14. Tadzocrangonyx alaicus, sp. n., female, 4.5 mm, holotype NC189: (А) gnathopod I; (B) gnathopod II. Male (?), 4.2 mm, paratype NC191: (C) gnathopod I; (D) gnathopod II. Scale bars 0.2 mm.

FIGURE 15. Tadzocrangonyx alaicus, sp. n., female, 4.5 mm, holotype NC189: (А) pereopod III; (B) pereopod IV; (C) pereopod V; (D) pereopod VI; (E) pereopod VII; (F) epimeral plates; (G) pleopod I; (H) pleopod II; (I) pleopod III. Scale bars 0.2 mm.