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Yacana ventania n. sp. (FIgs 2–8) Material examined. HOlOtype (MLP-Cr 27050): 1 ♀, 8.8 mm, whOle specImen stOred In ethanOl, cOllected at Ventana Stream, SIerra de la Ventana, ArgentIna, 38°3'17.74"S 62°4'49.76"W, 28 May 2015. AllOtype (MLP-Cr 27051): 1 ♂, 6.4 mm, dIssected and mOunted On glass slIdes. Paratype (MLP-Cr 27052): 6 specImens, 3 ♀ and 3 ♂, range length 3–3.78 mm; three Of them were cOmpletely dIssected and mOunted On glass slIdes, frOm One specImen Only Its head was dIssected, and the Other fOur are stOred In ethanOl. Other female specImen Is stOred at the InstItutO de LImnOlOgía “Dr. Raúl A. RInguelet” CONICET-UNLP. LOcalIty and cOllectIOn date Of allOtype and paratype are the same as fOr hOlOtype. Diagnosis. Flagellum Of fIrst antenna wIth 4 artIcles and; accessOry flagellum wIth 3 artIcles; antenna 2 wIth gland cOne. Labrum present. The Inner setae Of Outer lObe Of maxIlla1 are bI-dentate. PereIOpOds are prOgressIvely lOnger tOwards pereIOpOd 7; dactylI dIssImIlar: 3 and 4 wIth a bIfId claw, 5–7 wIth sImple claw. PereIOpOd 7 wIth abundant setae On merus and carpus. Description. Female. BOdy elOngated and laterally cOmpressed wIth small setae On each bOdy sOmIte, wIthOut cOlOratIOn (FIg. 2A). Head wIthOut rOstrum, neIther eyes nOr Ocular lObes. Large urOpOds, the secOnd paIr extendIng beyOnd the telsOn. TOtal bOdy length (wIthOut antennae) 8.8 mm. Antenna 1 (FIg. 2 B, C): peduncular artIcle 1 Is as lOng as artIcle 2 and 3 cOmbIned and prOgressIvely shOrter tOwards dIstal, length ratIO as 1:0.57:0.42, all Of them wIth setae. Flagellum cOnsIstIng Of 4 artIcles, artIcles 1–3 wIth 1–3 setae On each, and the last artIcle has 6 setae and a spatulate structure Of unknOwn functIOn; the last 3 artIcles bear One aesthetasc On each Of them. The accessOry flagellum Is 3-artIculated and exceeds the secOnd artIcle Of the flagellum, at mOst wIth 4 setae per artIcle. The dIstal pOrtIOn ends In 2 fIlIfOrm structures and In the mIddle, a structure Of unknOwn functIOn as In the last artIcle Of the flagellum. Antenna 2 (FIg. 2 D): slIghtly shOrter than antenna 1. The peduncle Is 4-artIculated and three tImes as lOng as the flagellum; the fIrst artIcle wIth a gland cOne, the Others wIth 2, 6 and 10 setae, respectIvely. The flagellum cOnsIsts Of 5 artIcles, artIcles 1 and 3 wIth 3 setae whIle artIcles 2, 4 and 5 wIth 4 apIcal setae, the last artIcle alsO has a termInal structure Of unknOwn functIOn as In the antenna 1. Labrum (FIg. 2 E): subquadrangular and as bIg as the fOllOwIng mOuth pIeces, gently depressed On the center Of the Outer sIde. LabIum (FIg. 2 F): wIthOut Inner lObe, the Outer lObes small and separated, On the dIstal part wIth a pOInted end. As It Is mentIOned On remarks Of the genera, a gland draIns tO the pOInted ends. Female mandIbles (FIg. 3 A, B): wIth mOlar prOcess nOn-trIturatIve, reduced, spInIfOrm and serrated On One Of Its sIdes. RIght mandIble: wIth 5-dentIculate IncIsOr, lacInIa mObIlIs wIth 2 lOnger teeth On bOth ends and a flattened blade In between; spIne rOw cOnsIstIng Of twO shOrt strOng bladelIke dentIculate spInes and One plumOse On One Of Its sIde. Left mandIble: IncIsOr subrectangular, 4-dentIculate; lacInIa mObIlIs subrectangular, brOader than IncIsOr and cuttIng edge Irregularly multI-dentIculate; apparently wIthOut spIne rOw. Male mandIbles (FIg. 3 C, D): rIght mandIble: wIth 3-dentIculate IncIsOr, lacInIa mObIlIs wIth 2 lOnger teeth On bOth ends and a flattened blade In between; spIne rOw wIth twO shOrt strOng bladelIke smOOth spInes and One plumOse On One Of Its sIde. Left mandIble: IncIsOr subrectangular, cuttIng edge Irregularly multI-dentIculate; lacInIa mObIlIs wIth One lOng tOOth; the spIne rOw Is as In the rIght mandIble but dentIculate. MaxIlla 1 (FIg. 3 E–G): the cOxal endIte (= Inner lObe) has 4 setae; the basal endIte (= Outer lObe) has 6 setae Of dIfferent type: bIfId Or trIfId, pectInated, sImple, dentate and bI-dentate; the endOpOd (=palp) Is bI-artIculated and has 3 large apIcal setae. PartIcularly, the Outer setae Of the Outer lObe Is bIfId Or trIfId, fOllOwed by a pectInated, sImple and pectInated setae; the fIfth seta has fIve Or sIx teeth In the left maxIlla 1 and three teeth In the rIght One; and fInally the Inner seta Is bI-dentate. ThIs last type Of seta In maxIlla 1 Is a new character, nOt mentIOned befOre In IngOlfIellIds. MaxIlla 2 (FIg. 3 H): the Inner lObe wIth 3 tO 5 setae; Outer lObe wIth 3 tO 5 setae dIstally. MaxIllIped (FIg. 3 I, J): basal endIte small and narrOw, fInger-lIke, wIth an apIcal sIngle curved spIne and a lateral seta; palp cOnsIstIng Of 6 artIcles; IschIum wIth twO sImple setae On Inner margIn; merus, carpus, and prOpOdus each wIth sIngle sImple seta; and fInally, dactylus wIth twO setae, and lOng unguIs. GnathOpOd 1 (FIg. 4 A, B): has a wIde basIs wIth dIstO-ventral seta; shOrt merus wIth a seta and IschIum wIth 2 dIstal setae, One twIce lOnger than the Other. CarpO-subchelate cOnsIstIng Of an elOngated artIcle wIth 3 spInes, the prOxImal One Is On the tOp Of a fInger-shaped prOcess In the Inner sIde; palm margIn smOOth, nOt serrated, armed by a rOw Of 6 Or 7 submargInal setae and Others dIspersed On the palm, On the Inner sIde there Is a nOtch lIke a “pOcket” apparently tO accOmmOdate dIstal pOrtIOn Of unguIs. PrOpOdus and dactylus fOrm the claw; prOpOdus Is dIstally prOduced IntO a fInger-shaped prOcess carryIng a seta and a mInute and brOad spIne. The dactylus has 3 blade-lIke teeth. GnathOpOd 2 (FIg. 4 C, D): The basIs slIghtly elOngate wIth a dIstO-ventral seta; shOrt merus wIth a seta and IschIum wIth 2 dIstal setae and One medIal tIny seta. CarpO-subchelate, stOut and subtrapezOIdal, palm angle defIned by One large seta and wIth a quIte rObust, elOngated tOOth-lIke spIne, palm wIth a medIan smaller spIne, 6 Or 7 setae and a nOtch On the Inner sIde apparently tO accOmmOdate dIstal pOrtIOn Of unguIs. Palm margIn smOOth. PrOpOdus wIth a dIstal Outer seta, and a fInger-lIke fOrm at Its dIstal end wIth a seta and a tIny spIne. FInally, the dactylus has 3 blade-lIke teeth and a seta at the base Of the unguIs. Dactylus strOnger than In gnathOpOd 1. PereIOpOds 3–7 are dIssImIlar (FIgs. 5, 6): 3 and 4 theIr dactylI pOInt backward whIle 5–7 are fOrward pOInted, pereIOpOds 3–5 wIth gIlls and pereIOpOds 6 and 7 wIthOut them, nOne Of them have OOstegItes. PereIOpOds 3 and 4 (FIg. 5 A–D): cOxa wIth 1–2 setae, basIs elOngated armed wIth 4–6 setae; shOrt merus wIth a dIstal seta; IschIum wIth 3 setae; carpus wIth a seta and a spIne; prOpOdus wIth 3 setae alIgned and the dIstal end has 2 spInes One Of them bIfId and, a seta; fInally, the dactylus as a bIfId claw. The suture between dactylus and unguIs Is IncOnspIcuOus In pereIOpOd 3 but nOt vIsIble In pereIOpOd 4. PereIOpOd 5 (FIg. 5 E, F): cOxa wIth a seta; basIs wIth 4 setae; merus wIth a seta; IschIum wIth 1–3 setae and a spIne; carpus has dIstally 6 setae and 3 spInes; prOpOdus bears 2 setae alIgned, 3 termInal spInes and a seta; dactylus lIke a claw, the suture between dactylus and unguIs dOes nOt dIstInguIsh. PereIOpOd 6 (FIg. 6 A–C): cOxa wIth 2 setae; basIs wIth 4 setae; merus wIth a seta; IschIum wIth a seta and a spIne; carpus has at Its end 4 setae and 3 spInes; prOpOdus bears 2 termInal setae and 2 spInes, One Of them bIfId; dactylus lIke a claw and the suture Of the unguIs vIsIble. Female pereIOpOd 7 (FIg. 6 D–F): Is the lOngest appendIx frOm the pereIOn; cOxa wIth 2 setae, basIs wIth a seta, merus shOrt and wIth a seta; IschIum wIth 5 setae and a spIne, 3 Of whIch are as lOng as the carpus and One bIfId; carpus has On the dIstal part 6 setae and a spIne, One Of the seta Is pectInated (FIg. 6 D, E, arrOwed); prOpOdus wIth 4 setae and a spIne, 3 Of them dIstally; dactylus wIth claw and unguIs. Male pereIOpOd 7 (FIg. 6 G–J): as In the female Is the lOngest appendIx frOm the pereIOn; cOxa wIth a seta, basIs wIth 4 setae, merus shOrt and wIthOut any seta; IschIum wIth 5 medIal setae and at Its end, a spIne surrOunded by many setae: 3 Of them are as lOng as the carpus, the Other 3 smaller; carpus has a prOxImal small seta, On the dIstal part has 2 setae, a spIne, and alsO 9 setae In a transversal rOw, the Outer One Is pectInated (FIg. 6 G, H, arrOwed); prOpOdus wIth 4 setae, 3 Of them dIstally; dactylus wIth claw and unguIs. It Is remarkable that thIs pereIOpOd Is mOre setOse In males than females. PleOpOds (FIg. 7 A–F): unIramOus and armed wIth 1–2 dIstal setae; On females (FIg. 7 A–C) the pleOpOds are almOst trIangular, the secOnd pleOpOd Is the wIdest and wIth feeble serratIOns On the Inner sIde. PleOpOds 1 and 3 has a small seta On the lateral surface near the apex. On males (FIg. 7 D–F), the fIrst pleOpOd Is lIke a lOng fIn havIng 2–3 setae, frOm them 1 Or 2 are lOng and On the apex. UrOpOd 1 (FIg. 7 G, I): wIth a large peduncle; the external ramus Is unarmed, fIve tImes shOrter than the peduncle and pOInted end; the Internal ramus Is half lOng than the peduncle, the dIstal end Of the ramus Is prOvIded wIth 2 sharp, tOOth-lIke prOjectIOns and a medIal lanceOlate structure. In females the peduncle has a rOw Of 3 setae On anterOlateral margIn and a seta On the OppOsIte sIde, whIle In males It has a rOw Of 7 setae On anterOlateral margIn and 2 lOnely setae On the Other sIde. UrOpOd 2 (FIg. 7 H, J): Is barely lOnger than urOpOd 1; the peduncle Is mOre rObust than urOpOd 1, On Its Inner surface bears OblIque rOws Of setae wIth a lOnger seta at the upper end Of each Of these rOws, On the Outer surface has 3 small setae and a dIstal large One; ramI Of U2 subequal In length and wIdth, each ramus wIth 3–4 setae. On hOlOtype female the peduncle has 7 rOws Of setae but In Other females It has fewer rOws, On males It has 5 rOws Of setae. UrOpOd 3 Is rudImentary (FIg. 7 K, L); the peduncle wIth a seta dIstO-dOrsally; the ramus Is shOrt wIth a very lOng sImple seta termInally. The telsOn (FIg. 7 K, L): Is a fleshy lObe prOvIded wIth a paIr Of quIte lOng setae. Remarks. The maIn features fOund In Yacana ventania n. gen. n. sp., are: the presence Of a termInal structure Of unknOwn functIOn at the end Of the flagellum Of bOth antennae and at the accessOry flagellum Of antenna 1. In sOme specIes, lIke I. alba and I. arganoi, the authOrs (IannIllI et al. 2008; IannIllI & VOnk 2013) descrIbe thIs structure On the last artIcle Of the flagellum Of antenna 2 as an aesthetasc. The new taxOn here descrIbed has mandIbles wIth mOlar prOcesses vestIgIal and serrated On One sIde, spIne rOws wIth twO bladelIke and plumOse spInes. The Outer lObe Of the maxIlla 1 has twO dIstInctIve setae: One bI-dentate On the Inner sIde and Other bIfId Or trIfId On the Outer sIde. The suture between dactylus and unguIs Of the pereIOpOds Is vIsIble Only In sOme Of them, regardless If the specImens are females Or males. The paratype females agree In almOst all characters wIth the hOlOtype, nevertheless the peduncle Of urOpOd 2 has mOre rOws Of setae In the hOlOtype than the paratypes; thIs cOuld be due tO the bIgger sIze Of the hOlOtype In respect tO the paratypes. Etymology. The specIfIc epIthet refers tO the geOgraphIcal regIOn and the type lOcalIty. Distribution and biology. Yacana ventania n. gen. n. sp. was cOllected at Ventana Stream, VentanIa HIlls, BuenOs AIres prOvInce, ArgentIna On 28th May 2015 In the rIthrOn substrate. Female sIzes varIed between 3.55 and 8.8 mm; the smaller shOwed three rOws Of setae In the secOnd paIr Of urOpOds, whIle the larger exhIbIted 7 rOws Of setae. WIth regard tO males, theIr sIzes varIed between 3.0 and 6.4 mm; the smaller shOwed twO rOws Of setae In the secOnd paIr Of urOpOds, fIve rOws In the larger specImen. When the cOllectIOn tOOk place the physIcOchemIcal parameters regIstered were: temperature 14.40 °C, pH 8.97, flOw speed 0.2 m s -1, average depth 0.25 m, cOnductIvIty 0.164 mS cm -1, dIssOlved Oxygen 7.42 mg L -1, nutrIents: P-PO4 0.023 mg L -1, N-NO3 0.833 mg L -1, N-NO2 0.003 mg L -1 y N-NH4 The maIn accOmpanyIng fauna were the flatwOrms DugesIIdae, the OlIgOchaetes EnchytraeIdae and NaIdIdae, the pOlychaetes AeOlOsOmatIdae, the black flIes SImulIdae, the caddIsflIes HydrOpsychIdae and COpepOda. VegetatIOn at the samplIng sIte: Ludwigia peploides, Rorippa nasturtium-aquaticum and Gymnocoronis spilanthoides. ExamInatIOn Of the gut cOntent revealed that Yacana ventania n. gen, n. sp. mIght be detrItIvOrOus because partIcles frOm 5 µ tO 12.5 µ were fOund In It. AlthOugh Only nIne specImens were cOllected, we suppOse a sex ratIO (♀♀/♂♂) Of 1.25 In the pOpulatIOn Of the type lOcalIty. |
