Zygobothrium megacephalum DIESINg 1850
Creators: name: Alves, Philippe V.
name: Chambrier, Alain De
name: Luque, José L.
name: Scholz, Tomáš
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Platyhelminthes
Cestoda
Proteocephalidea
Proteocephalidae
Zygobothrium
Zygobothrium megacephalum

description: Zygobothrium megacephalum Diesing, 1850
Type and only known host. Phractocephalus hemioliopterus (BlOch & SchNEIdER) (SIlURIfORmES: PImElOdIdaE).
Site of infection. POSTERIOR INTESTINE.
Type locality. SOUThERN AmaZON RIVER baSIN, MaTO GROSSO STaTE (fORmER caPTaINcY Of MaTO GROSSO), BRaZIl— SPEcIfIc lOcalITY UNKNOWN. MaTERIal cOllEcTEd bY JOhaNN NaTTERER IN 1826 aNd 1828 (SEE DIESINg 1855). Additional localities. AmaZON RIVER, NEaR MaNaUS, AmaZONaS STaTE, BRaZIl; AmaZON RIVER, IqUITOS, REgION Of LORETO, PERU (dE ChambRIER et al. 2006); XINgú RIVER, NEaR AlTamIRa, PaRÁ STaTE, BRaZIl (3°12'S; 52°12'W).
Prevalence of infection. INfEcTEd 20 Of 29 fISh EXamINEd, I.E., PREValENcE 69%, fROm ThE AmaZON RIVER, ITacOaTIaRa, BRaZIl; 3 Of 5 fISh (60%) fROm ThE XINgú RIVER, AlTamIRa, BRaZIl.
Representative DNA sequence. 5.8S-ITS2-28S RDNA gENES (AY551177), 18S RDNA gENE (AF286991), 28S RDNA gENE (AF286939, AJ388621), 16S RDNA gENE (AJ389508), cox 1 mTDNA gENE (AJ275053) (ZEhNdER & MaRIaUX 1999; OlSON et al. 2001; HYPša et al. 2005). A fRagmENT 1 513 bP lONg Of ThE 28S RDNA gENE (D1–D3 dOmaINS) Of a SINglE SPEcImEN fROm ThE XINgú RIVER (TRIbUTaRY Of ThE AmaZON RIVER) WaS gENERaTEd de novo (GENBaNK MG429813).
Material studied. SYNTYPES—MHNG-PLAT-42526, 42527, 5 WhOlE-mOUNTEd SPEcImENS (5 SlIdES), aNd 15 SlIdES Of SERIal cROSS-SEcTIONS. AddITIONal SPEcImENS—MHNG-PLAT-18316, 18317, 3 WhOlE-mOUNTEd SPEcImENS (3 SlIdES) aNd 6 SlIdES Of SERIal cROSS-SEcTIONS, cOllEcTEd ON 17.IX.1992, hOST fIEld NOS. BR 291, 326; CHIOC 38884, MHNG-PLAT-21847, WhOlE-mOUNTEd SPEcImEN (1 SlIdE) aNd 19 SlIdES Of SagITTal SEcTIONS Of ScOlEX, cOllEcTEd ON 1.X.1995, hOST fIEld NO. BR 445; CHIOC 38885, MHNG-PLAT-19302, 21846, 21854, 21911, 22014, 22049, 22370, 85239, 5 WhOlE-mOUNTEd SPEcImENS, fRagmENTS (10 SlIdES) aNd SagITTal SEcTIONS Of ThE ScOlEX aTTachEd TO hOST INTESTINE (13 SlIdES), cOllEcTEd bETWEEN 5.X.1995 aNd 18.X.1995, hOST fIEld NOS. BR 334, 445, 539, 547, 599, 649, 802, 804; all SPEcImENS fROm ITacOaTIaRa, AmaZONaS, BRaZIl, cOllEcTEd bY A. A. REgO aNd A. dE ChambRIER. CHIOC 38883, IPCAS C-401, TWO WhOlE-mOUNTEd SPEcImENS (TWO SlIdES), cOllEcTEd ON 24.IV.2013, hOST fIEld NOS. BR-X 35a (hOlOgENOPhORE), BR-X 70d1; CHIOC 38567, ONE SPEcImEN IN 70% EThaNOl, cOllEcTEd ON 24.IX.2013, hOST fIEld NO. BR-PAX 6d; SPEcImEN fROm AlTamIRa, PaRÁ, BRaZIl, cOllEcTEd bY P. V. AlVES aNd T. SchOlZ.
Re-description (baSEd ON 12 WhOlE-mOUNTEd WORmS; 4 SlIdES WITh SERIal cROSS-SEcTIONS Of maTURE PROglOTTIdS aNd 5 SlIdES WITh SagITTal SEcTIONS Of 1 ScOlEX; 1 ScOlEX aNd PROglOTTId STUdIEd USINg SEM). PROTEOcEPhalIdaE, fORmER SUbfamIlY ZYgObOThRIINaE. TESTES, OVaRY aNd UTERUS mEdUllaRY; VITEllINE fOllIclES cORTIcal; mEdIUm-SIZEd WORmS. TOTal bOdY lENgTh 16–38 mm (N = 5), maXImUm WIdTh UP TO 2.3 mm (N = 17). STRObIla aNaPOlYTIc, cRaSPEdOTE, WITh TWO dORSal aNd TWO VENTRal VElUm-lIKE lacINIaTIONS, cONSISTINg Of abOUT 80–105 PROglOTTIdS: 50–65 ImmaTURE, 4–5 maTURE, 22–26 PREgRaVId aNd 5–8 gRaVId. ImmaTURE, maTURE aNd PREgRaVId PROglOTTIdS maRKEdlY WIdER ThaN lONg (lENgTh: WIdTh RaTIO 0.06–0.40), gRaVId PROglOTTIdS WIdER ThaN lONg (lENgTh: WIdTh RaTIO 0.50–0.90).
ScOlEX RObUST, qUadRaNgUlaR, 1.5–1.6 × 2.7–2.9 mm (N = 4), bEaRINg 4 UNIlOcUlaTE SUcKERS, Each WITh TWO OPENINgS, SEPaRaTEd bY bRIdgE-lIKE SEPTUm (FIgS. 19–21, 29). SUcKERS ElONgaTEd, dEEPlY EmbEddEd, STRONglY mUScUlaR, 940–1205 × 435–580 (N = 5); bOTh aNTERIOR maRgINS WITh cIRcUlaR mUScUlaTURE SERVINg aS SPhINcTER. APEX flaTTENEd, lacKINg aPIcal ORgaN (FIgS. 19–21, 29). APEX Of ScOlEX aNd EXTERNal RIm Of SUcKERS cOVEREd WITh caPIllIfORm fIlITRIchES INTERSPERSEd WITh gladIaTE SPINITRIchES (FIgS. 23, 25); SEPTUm Of SUcKER caVITY cOVEREd WITh fEW caPIllIfORm fIlITRIchES aNd laRgE gladIaTE SPINITRIchES (FIg. 24); REgION bETWEEN SUcKERS cOVEREd WITh caPIllIfORm fIlITRIchES INTERSPERSEd WITh fEW gladIaTE SPINITRIchES (FIg. 26); STRObIla aNd lacINIaTIONS cOVEREd WITh caPIllIfORm fIlITRIchES Of SImIlaR aPPEaRaNcE aNd dENSITY (FIgS. 27, 28).
INNER lONgITUdINal mUScUlaTURE WEll-dEVElOPEd, fORmINg ONE ROW Of laRgE bUNdlES Of mUSclE fIbERS ON dORSal aNd VENTRal SIdES (FIgS. 32–35). OSmOREgUlaTORY caNalS SITUaTEd aT dIffERENT lEVElS, WITh VENTRal caNalS mEdIaN TO dORSal ONES; VENTRal caNalS ThIcK-WallEd, aT SamE lEVEl aS laTERalmOST TESTES (FIgS. 31–36); dORSal caNal NaRROWER ThaN VENTRal ONE (FIg. 31–36).
TESTES NUmEROUS, SPhERIcal, 60–70 IN dIamETER, IN 2–3 laYERS IN mEdUlla, 110–200 (X = 159; N = 8) PER maTURE PROglOTTId (FIgS. 30, 32, 33); TESTES fORm ONE fIEld, SITUaTEd VENTRal TO OVaRY aNd dORSal TO cIRRUS-Sac (FIgS. 31–35). TESTES PRESENT alSO IN gRaVId PROglOTTIdS.
VaS dEfERENS cOIlEd, WITh lOOPS fORmINg ElONgaTE fIEld REachINg TO, bUT NOT cROSSINg, mEdIaN lINE Of PROglOTTId (FIg. 30). CIRRUS-Sac ElONgaTEd, ThIcK-WallEd, cOmPOSEd Of TWO dIffERENT PaRTS, WITh dISTal (aNTERIOR) PaRT lONgER ThaN ShORTER PROXImal (POSTERIOR) PaRT (FIgS. 30, 31, 34–36), 400–610 × 70–95 (N = 17), ITS lENgTh REPRESENTINg 17– 29% (X = 23; N = 9) Of PROglOTTId WIdTh. SPERm dUcT (INTERNal VaS dEfERENS) SINUOUS (FIgS. 30, 36). CIRRUS mUScUlaR, aRmEd WITh SPINITRIchES (FIg. 36), REachINg UP TO 80% (N = 17) Of cIRRUS-Sac lENgTh. COmmON gENITal aTRIUm NaRROW, dEEP (FIgS. 30, 31). GENITal PORES alTERNaTINg IRREgUlaRlY, maRKEdlY PRE-EqUaTORIal TO almOST EqUaTORIal, SITUaTEd aT 23–48% (X = 30; N = 17) Of PROglOTTId lENgTh fROm aNTERIOR maRgIN (FIgS. 30, 31).
OVaRY mEdUllaRY, bIlObEd, fOllIcUlaTE (FIgS. 30, 31, 33), WITh SOmE dORSal fOllIclES PENETRaTINg bETWEEN bUNdlES Of INNER lONgITUdINal mUScUlaTURE INTO cORTEX (FIg. 33); WIdTh Of OVaRY REPRESENTS 37–56% (X = 50%; N = 11) Of PROglOTTId WIdTh, ITS lENgTh REPRESENTINg 24–54% (X = 42%; N = 11) Of PROglOTTId lENgTh (FIgS. 30, 31). MEhlIS’ glaNd abOUT 115–215 IN dIamETER, REPRESENTINg abOUT 9% Of PROglOTTId WIdTh (N = 5). RElaTIVE OVaRIaN SIZE, I.E., PERcENTagE Of OVaRY SURfacE TO TOTal SURfacE Of maTURE OR PREgRaVId PROglOTTIdS (SEE dE ChambRIER et al. 2012), 21– 22% (X = 21.5%; N = 2).
VagINal caNal SlIghTlY SINUOUS, SURROUNdEd bY chROmOPhIlIc cEllS, WIdER IN TERmINal PaRT (pars copulatrix vaginae); laRgE, SPhERIcal VagINal SPhINcTER PRESENT aT SOmE dISTaNcE Of gENITal aTRIUm (FIgS. 30, 31, 35, 36). VagINa aNTERIOR (42%) OR POSTERIOR (58%) TO cIRRUS-Sac (N = 26). VITEllINE fOllIclES cORTIcal, fORmINg TWO WIdE dORSal aNd VENTRal baNdS NEaR ThE laTERal maRgINS Of PROglOTTIdS, dORSallY UNINTERRUPTEd aT cIRRUS-Sac lEVEl, RaRElY PRESENT PREPORallY, ON VENTRal SIdE (FIgS. 30–33).
UTERUS mEdUllaRY, WITh dEVElOPmENT Of TYPE 2 (SEE dE ChambRIER et al. 2004a, 2015a); UTERINE STEm aNd dIVERTIcUla (laTERal UTERINE bRaNchES) IN maTURE aNd PREgRaVId PROglOTTIdS lINEd WITh NUmEROUS chROmOPhIlIc cEllS, EXTENdEd bEYONd bRaNchES (FIgS. 31–33). UTERUS WITh 8–11 laTERal dIVERTIcUla ON Each SIdE, OPENINg bY ElONgaTE SlIT-lIKE PORE (FIg. 31). EggS ROUNdEd, VacUOlaTEd, OUTER ENVElOPE 50–65 IN dIamETER (N = 5); EmbRYOPhORE 23–25; ONcOSPhERE 11–12, EmbRYONIc hOOKS 5.5–6.5 lONg, dIgITaTE PROjEcTION abOUT 1–2 lONg (N = 5) (FIg. 37).
Remarks. ThE SPEcIES WaS bRIEflY chaRacTERIZEd bY DIESINg (1850), WhO EValUaTEd 17 TaPEWORmS cOllEcTEd bY J. NaTTERER IN BRaZIl. DIESINg (1855) IllUSTRaTEd ThE EXTERNal mORPhOlOgY Of ThE ENTIRE WORm, INclUdINg ITS ScOlEX aNd PIEcES Of ThE STRObIla. ThE fOllOWINg aUThORS PROVIdEd a fEW addITIONal dETaIlS, bUT alSO cOmmITTEd SOmE ERRORS, aS bRIEflY cOmmENTEd hEREIN. WOOdlaNd (1933) PROVIdEd a dETaIlEd mORPhOlOgIcal chaRacTERIZaTION Of ThE SPEcIES; hIS mEaSUREmENTS cORRESPONd WEll WITh ThOSE Of ThE PRESENT STUdY, EXcEPT ThaT hE SEEmINglY STUdIEd laRgER INdIVIdUalS. WOOdlaNd (1933) alSO cORREcTlY REPORTEd mOST Of ThE chaRacTERISTIcS TYPIcal Of ThE SPEcIES, bUT cONfUSEd OVaRIaN fOllIclES PENETRaTINg TO ThE cORTEX aS VITEllINE fOllIclES. HE PROPOSEd ThE SUbfamIlY ZYgObOThRIINaE TO accOmmOdaTE Zygobothrium, WhIch haS bEEN gENERallY accEPTEd (FREZE 1965; REgO 1994).
FUhRmaNN (1934) alSO STUdIEd ThE TYPE maTERIal Of Z. megacephalum aNd PROPERlY IllUSTRaTEd ThE OVaRIaN fOllIclES PENETRaTINg TO ThE dORSal cORTEX aNd ThE POSITION Of ThE VITEllINE fOllIclE baNdS, VagINal SPhINcTER aNd OSmOREgUlaTORY caNalS. HOWEVER, hE OVERlOOKEd SPhINcTERS ON ThE aNTERIOR maRgIN Of ThE SUcKERS aNd dEScRIbEd ThE INTERNal lONgITUdINal mUScUlaTURE aS WEaKlY dEVElOPEd WhEN IT IS IN facT WEll-dEVElOPEd (SEE FIgS. 35, 36 IN ThE PRESENT STUdY).
REgO (1984) PROVIdEd ThE fIRST SEM mIcROgRaPhS Of ThE ScOlEX Of Z. megacephalum aNd REPORTEd ThE PRESENcE Of a glaNdUlaR ORgaN ON ThE aPEX Of ThE ScOlEX, bUT WE WERE UNablE TO fINd SUch aN ORgaN IN aNY Of ThE SPEcImENS STUdIEd (FIg. 29). SchmIdT (1986) REPORTEd gENITal PORES aS UNIlaTERal aNd ThE cIRRUS aS UNaRmEd, bUT ThE PORES alTERNaTE IRREgUlaRlY aNd ThE cIRRUS IS cOVEREd WITh SPINITRIchES (FIg. 34).
ThE mOST cOmPREhENSIVE mOlEcUlaR PhYlOgENETIc aNalYSIS, YET INfERREd fROm SEqUENcES Of a SINglE gENE (lsr DNA), REVEalEd Z. megacephalum aS ONE Of ThE EaRlIEST dIVERgEd NEOTROPIcal fISh cESTOdES, TOgEThER WITh aNOThER TWO SPEcIES fROm ThE REdTaIl caTfISh, NamElY Proteocephalus hemioliopteri dE ChambRIER & VaUchER, 1997 aNd Scholzia emarginata (DIESINg, 1850) (SEE dE ChambRIER et al. 2015a). INTERESTINglY, ThESE ThREE SPEcIES fORm a WEll-SUPPORTEd cladE WITh NEaRcTIc SPEcIES Of ThE fORmER SUbfamIlY CORallObOThRIINaE fROm chaNNEl caTfIShES (IcTalURIdaE), I.E., SPEcIES Of ThE gENERa Corallotaenia FREZE, 1965, Essexiella SchOlZ, dE ChambRIER, MaRIaUX & KUchTa, 2011, aNd Megathylacoides JONES, KERlEY & SNEEd, 1956.
IN addITION TO ITS mOST baSal PhYlOgENETIc POSITION amONg NEOTROPIcal fISh PROTEOcEPhalIdS, Z. megacephalum POSSESSES a UNIqUE cOmbINaTION Of chaRacTERISTIcS ThaT OccUR ONlY RaRElY IN OThER PROTEOcEPhalIdS. ThEY aRE bRIEflY dIScUSSEd bElOW.
(1) SUcKERS WITh ThE caVITY dIVIdEd bY a bRIdgE-lIKE SEPTUm, I.E., WITh TWO SEPaRaTEd OPENINgS, haVE bEEN PREVIOUSlY fOUNd ONlY IN Barsonella lafoni dE ChambRIER, SchOlZ, BElETEW & MaRIaUX, 2009 fROm Clarias SPP. (SIlURIfORmES) IN AfRIca. HOWEVER, ThE OPENINgS IN ThESE TWO SPEcIES aRE cONSPIcUOUSlY dIffERENT fROm Each OThER, WITh ThE POSTERIOR OPENINg IN B. lafoni bEINg mUch SmallER ThaN ThE aNTERIOR ONE (dE ChambRIER et al. 2009b). IT IS WORTh NOTINg ThaT ThE SPEcIES aRE clOSElY RElaTEd (SEE dE ChambRIER et al. 2015a).
(2) ThE aRmEd cIRRUS WaS PREVIOUSlY REPORTEd ONlY IN Euzetiella tetraphylliformis dE ChambRIER, REgO & VaUchER, 1999 fROm ThE PImElOdId caTfIShES Of ThE gENUS Zungaro BlEEKER IN BRaZIl (dE ChambRIER et al. 1999). HOWEVER, SPINaTION Of ThE cIRRUS IS RaThER cOmmON IN cYclOPhYllIdEaN cESTOdES aNd mEmbERS Of dIffERENT ORdERS Of ElaSmObRaNch TaPEWORmS (SEE CaIRa & JENSEN 2017). IT IS ThUS PlaUSIblE TO aSSUmE ThaT ThIS chaRacTER maY haVE aPPEaREd mORE ThaN ONcE dURINg ThE EVOlUTIONaRY hISTORY Of cESTOdES.
(3) STRObIla WITh fOUR VElUm-lIKE lacINIaTIONS ObSERVEd IN Z. megacephalum IS PRESENT ONlY IN S. emarginata, bUT acTUal fUNcTIONal ImPORTaNcE Of ThESE STRUcTURE IS UNKNOWN.
(4) ShORT dIgITaTE PROjEcTIONS ON ThE SURfacE Of ThE EmbRYOPhORE WERE ObSERVEd ONlY IN ThE EggS Of PROTEOcEPhalIdS fROm TERRESTRIal hOSTS, SUch aS ThE SNaKE TaPEWORmS Vaucheriella bicheti dE ChambRIER, 1987 fROm Tropidophis cf. taczanowskyi (STEINdachNER) IN EcUadOR, Ophiotaenia gallardi (JOhNSTON, 1911) fROm Pseudechis porphyriacus (ShaW) IN AUSTRalIa, aNd Thaumasioscolex didelphidis CañEda-GUZmÁN, dE ChambRIER & SchOlZ, 2001 fROm ThE cOmmON OPOSSUm Didelphis marsupialis LINNaEUS IN MEXIcO (CañEda-GUZmÁN et al. 2001; COqUIllE & dE ChambRIER 2008; dE ChambRIER & dE ChambRIER 2010). ThE TWO laTTER SPEcIES aRE PhYlOgENETIcallY dISTaNTlY RElaTEd TO Z. megacephalum (mOlEcUlaR daTa ON V. bicheti aRE NOT aVaIlablE) aNd ThUS IT IS PlaUSIblE TO cONSIdER ThE PRESENcE Of ThESE STRUcTURES aS fUNcTIONal adaPTaTIONS Of INdIVIdUal TaXa WITh aN INdEPENdENT EVOlUTIONaRY hISTORY.
(5) ThE PRESENcE Of OVaRIaN OUTgROWThS IN ThE cORTEX, I.E., PENETRaTION Of SOmE OVaRIaN fOllIclES fROm ThE mEdUlla TO ThE dORSal cORTEX bETWEEN bUNdlES Of ThE INNER lONgITUdINal mUScUlaTURE, IS a chaRacTERISTIc Of Frezella vaucheri AlVES, dE ChambRIER, SchOlZ & LUqUE, 2015 aNd SPEcIES Of ThE fORmER SUbfamIlIES ENdORchIINaE, RUdOlPhIEllINaE aNd SOmE SPEcIES Of ThE PElTIdOcOTYlINaE (dE ChambRIER & VaUchER 1997; GIl dE PERTIERRa & dE ChambRIER 2000; GIl dE PERTIERRa 2009; AlVES et al. 2015). HOWEVER, ThIS fEaTURE SEEmS TO bE hOmOPlaSTIc aS ThESE SPEcIES aRE ONlY dISTaNTlY RElaTEd (SEE dE ChambRIER et al. 2015a).
description: Published as part of Alves, Philippe V., Chambrier, Alain De, Luque, José L. & Scholz, Tomáš, 2018, Towards a robust systematic baseline of Neotropical fish tapeworms (Cestoda: Proteocephalidae): amended diagnoses of two genera from the redtail catfish, Phractocephalus hemioliopterus, pp. 363-380 in Zootaxa 4370 (4) on pages 370-374, DOI: 10.11646/zootaxa.4370.4.3, http://zenodo.org/record/1146439