Progyliauchen magnacetabulum, Al-Jahdali & O, 2013

Al-Jahdali, O. & O, P., 2013, New Intestinal Trematodes From Siganid Fishes Off The Saudi Coast Of The Red Sea, Acta Zoologica Academiae Scientiarum Hungaricae 59 (1), pp. 3-12 : 9-10

Progyliauchen magnacetabulum sp. n.

( Fig. 2 )

Type- host: S. luridus Rüppel (Teleostei, Siganidae ).

Site: Lowerintestine.

Type- locality: RedSeaoffthecoastofRabigh (between 22°49′Nand 22°54′N), SaudiArabia. Prevalence: 12/50 fishesexamined; 24%.

Type- material: HolotypeandparatypesaredepositedintheNaturalHistoryMu-

seum, London, Reg. nos. 2011.8.2.1 and 2011.8.2.2–10.

Description (Basedon 14 fullygravidspecimens): Bodyfleshy, robust, taperedan- teriorly, elongatetopyriform, 1,980 –3,200 (2,590) inlength, 610–950 (780) inmaximum widthatitsmiddle. Excretorypapillaabsent. Tegumentunspined. Oralsuckerabsent. Ventralsuckerlarge, spherical, 495–753 (624) indiameter, inmiddleofposteriorhalfof body, wellseparatedfromposteriorextremity. Pharynxelongate, 161–255 × 121–191 (208 × 156). Oesophagusverylong, relativelynarrow, highlycoiled, with 2–3 loops, longerthan bodylength, surroundedbyglandularcellsalongmostofitslength. Oesophagealbulb round, large, 198–295 × 229–323 (246 × 276). Intestinalbifurcationatbeginningofmid- dlethirdofbody; caecasimple, wide, extendintomiddlethirdofbody. Testes 2, oval, symmetrical, dorsaltoventralsucker, sub-equal, 241–383 × 177–281 (312 × 229). Cirrussac short, claviform, mainlyintercaecal, 251–383 (317) inlength, 148–230 (189) wideatitsbase, containstubularseminalvesicle (partlyexternaltocirrussac), well- developedprostatic complexandrelativelyshortejaculatoryduct; prostaticcellsextendoutsidethecirrussac tocoverexternalpartofseminalvesicle. Genitalporemedian, directlyposteriortointes- tinalbifurcation. Ovarytetra- lobed, median, anteriortoventralsuckerorbetweencaecal extremities. Seminalreceptacleoval, submedian, betweenventralsuckerandleftcaecum. Mehlis’glandwelldeveloped. Inseminationchamberlocatedbetweenovaryandoötype. Laurer’scanalopensondorsalsurfaceatlevelofventralsucker. Uterusshort, winding betweenovary, cirrussacandleftcaeum. Eggsthin-shelled, yellowish, 68–80 × 42–54 (74 × 48). Vitellinefolliclesrelativelysmall, irregular, numerous, extendalongcaecaforalmost theirentirelength. Transversevitellinecollectingductscomingfromvitellinefolliclesof eachsideopenintosmallsphericalvitellinereservoirdorsaltoanteriorborderofventral sucker. Excretoryvesicleclaviform, extendsanteriorlytonearventralsucker; excretory porepostero- terminal.

Comment – Morphologically,theabovedescriptionof P. magnacetabulum sp. n. agreeswellwiththeconceptof Progyliauchen ShalabyetHassanine 1997 , whichistodatestillendemictothe Siganus spp. intheRedSea. Although, P. magnacetabulum sp. n. and P. sigani (previously, theonlyspeciesofthegenus) arefromcloselyrelated, sympatrichostsofasimilarsize, thenewspecies clearlydiffersinsomespecificfeatures:

− Theventralsuckerisspherical, largeandstout (495–753 μmindiameter), butin P. sigani thissuckeristransverselyelongateandmuchsmaller (188–293 × 245–372 μm).

− Theoesophagusisverylong, highlycoiled (with 2–3 loops) andlonger thanthetotalbodylengthifstraightened, butin P. sigani theoesophagus slightlyconvolutedintolateralfoldsandmuchshorter (about 55% ofthe totalbodylength).

− Theoesophagealbulbislarge (198–295 × 229–323 μm), butin P. sigani , thebulbismuchsmaller (130–172 μmindiameter).

− Theseminalvesicleistubular, butin P. sigani itisconstrictedintothreeparts.

Inviewofthesedifferences, thepresentspeciesisconsideredtobenew

toscience.

Etymology: Thespecificname “ magnacetabulum ” ofthenewspeciesreferstothelarge

ventralsuckerofthenewspecies.

*

Acknowledgements – IamverygratefulforKingAbdulazizUniversity, SaudiArabia, forcontinuedencouragementandsupport. Ishouldalsoliketoextendmyappreciationto thestaffofRabigh- FacultyofScienceandArts, KingAbdulazizUniversity, fortheirhelp duringthecollectionofthematerial.

Figures

Figs 1–2. Holotypes (whole-mount, ventral view): 1 = Hexangium saudii sp. n. from Siganus rivulatus, Red Sea. 2 = Progyliauchen magnacetabulum sp. n. from Siganus luridus, Red Sea. Scale bar= 500 μm.